Study on Challenges and Solutions for Enhancing Photocatalytic Activities of Ag<sub>3</sub>PO<sub>4</sub> Nanoparticles for Degradation of Organic Dyes from Wastewater

Beyecha, Wegene Lelisa; Asefa, Misikir Tamiru; Feyisa, Gebisa Bekele

doi:https://doi.org/10.1155/2022/5564667

Journal of Nanomaterials

On this page

Abstract Introduction Conclusion Data Availability Conflicts of Interest Acknowledgments References Copyright Related Articles

Review Article | Open Access

Volume 2022 | Article ID 5564667 | https://doi.org/10.1155/2022/5564667

Study on Challenges and Solutions for Enhancing Photocatalytic Activities of Ag₃PO₄ Nanoparticles for Degradation of Organic Dyes from Wastewater

Wegene Lelisa Beyecha,¹Misikir Tamiru Asefa,¹and Gebisa Bekele Feyisa¹

Academic Editor: Baskaran Rangasamy

Received28 Feb 2021

Revised29 Apr 2022

Accepted16 May 2022

Published06 Jun 2022

Abstract

Improper management of discharged waste material such as toxic organic dyes from industries causes severe health and economic problems because contaminated water with organic dyes is harmful to human being and aquatic ecosystems. The photocatalyst is a preferable wastewater treatment method because it is environmentally benign, cost-wise, and more efficient in degrading dyes. Most metal oxide semiconductors are photocatalytic materials, but nowadays, Ag₃PO₄ nanoparticles have attracted enormous attention due to their low bandgap and high absorption of visible light. However, Ag₃PO₄ nanoparticles have low performance due to photocorrosion, high recombination rate, and instability in the solution. Thus, in this review article, the mechanism to enhance the photocatalytic activities of Ag₃PO₄ nanoparticles was discussed, and the future perspective of the silver phosphate was also stated.

1. Introduction

Global widespread industrialization has brought a change in human life by giving vast opportunities to get employment. On the other hand, poor management of industrial wastes such as heavy metals, dyes, pharmaceutical waste, and agricultural wastes caused severe environmental pollution because most of these discharged compounds are stable so that they can persist for a long time [1–3]. Amazingly, the final destination of all industrial wastes including solid form, liquid, or gas form ended in the water body. As a result, the degree of environmental pollution by contaminated water is enormous. So, water pollution has tremendous negative consequences on the economy and health of human beings. Vanishing aquatic lives and deteriorating health of human beings are mainly the results of water pollution [4, 5]. Wastewater treatment is crucial to get a healthy environment.

There are two types of wastewater treatment methods such as traditional and advanced wastewater treatment techniques. Conventional wastewater treatment methods are the following: coagulation, filtration, disinfection, sedimentation, de-chlorination, adsorption onto activated carbon, screening, chemical precipitation [4–6], screening, and chemical precipitation. However, advanced techniques such as membrane filtration, reverse osmosis, ion exchange, electro-dialysis, adsorption, and advanced oxidation process have been used widely for wastewater treatment [7]. The advanced oxidation process (AOPs) is one of the recent methods for wastewater treatment due to degrading nonbiodegradable, chemically stable, persistent pollutants and its low operating cost, no chemical agent needed, and minimal sludge formation. Furthermore, the AOPs generated reactive oxygen species (ROS) that oxidize a broad range of organic pollutants inside wastewater [8].

Three common types of AOPs are photocatalyst, photolysis, and photo-Fenton which are light irradiated based [9]. Among those, photocatalysts gained tremendous attention because of the following reasons: (i) a small number of catalysts able to degrade a large number of dyes; (ii) no need for external force, environmentally benign; and (iii) cost-effective technology, and the organic pollutants directly converted nonoffensive by-products such as CO₂ and H₂O [10, 11]. Metal oxide semiconductors ZnO [3] and TiO₂ are widely used photocatalytic materials owing to their low cost, strong redox capacity, and good thermal and chemical stability [12, 13]. However, they operate only under UV light due to their wide bandgap (3-3.2 eV). The UV light reaches the earth’s surface only 4-5% of the total solar spectrum, but the amount of visible light that arrives at the earth’s surface is 45%. Doping of ZnO and TiO₂ reduces the bandgap of ZnO and TiO₂. As a result, they can operate in the visible range. However, doping these metal oxides introduces a new energy level in the bandgap, which acts as the recombination center of photogenerated e^--h⁺ pairs. Such recombination of electrons-holes is the main factor to reduce the photocatalytic efficiency of TiO₂ and ZnO [14–16]. To harvest a large amount of visible light (45%), it needs to develop or use novel visible light-responsive photocatalytic materials.

There are various types of metal oxide semiconductor that operate under visible light such as Fe₂O₃ (=2.1 eV), WO₃ (=2.6 eV), SnO₂ (=2.30 eV), Bi₂O₃ (=2.48 eV), Ag₃PO₄ (2.45 eV), CuO ( eV), and Cu₂O (2.17 eV) [10, 11, 17, 18]. Among these metal oxides, Ag₃PO₄ is the preferable photocatalytic material because of its high photoefficiency than other aforementioned oxides. For instance, the quantum efficiency of Ag₃PO₄ is up to 90% at a wavelength greater than 420 nm and its extremely high photooxidative ability to split water to the evolution of oxygen (O₂) and high organic dye removal under visible light irradiation [12, 13]. The reasons why Ag₃PO₄ have these mentioned benefits over other oxides are because of its novel atomic configurations and its metallic-like electronic structures. The reduction potential of H⁺/H₂ is more negative than the conduction band minimum of Ag₃PO₄. Consequently, Ag₃PO₄ may produce oxygen, not hydrogen. As a result of mentioned novel properties of Ag₃PO₄, it has been chosen as a candidate material for photocatalytic properties than other narrow bandgap semiconductors. Moreover, Yi et.al reported the first Ag₃PO₄ photocatalyst for degrading organic pollutants and splitting water [13, 14]. The schematic diagram of a photocatalytic mechanism of Ag₃PO₄ is shown in Figure 1.

Figure 1 shows that the conduction band edge potential of Ag₃PO₄ is more positive than the single-electron reduction process potential of -0.046 eV; thus, single-electron reduction for producing superoxide radicals (^•O₂^-) did not take place on the conduction band of Ag₃PO₄. Under visible light irradiation on the Ag₃PO₄ catalyst, the electron-hole pairs were generated, and the electron was excited to the conduction band of Ag₃PO₄. The excess electron on the conduction band of Ag₃PO₄ facilitated a multioxidation reaction (), and it further react with single electros () to form hydroxide radicals; those radicals reacted with methylene blue dyes and decomposed it into CO₂ and H₂O. In addition to this, the combination of Ag⁺ ions with single electrons forms a black Ag^o nanoparticle which is the main reason for the instability and photocorrosion of Ag₃PO₄. In the second reaction, the hole reacted with H₂O and formed OH^o radicals while it has been reacted with dyes and decompose into carbon dioxide and water [15, 16]. However, the photocatalytic activity of Ag₃PO₄ is limited due to photocorrosion, high recombination rate, and instability in a solution [14, 19, 20]. In this review article, we discussed the possible means to enhance the degradation of organic pollutants from wastewater by using Ag₃PO₄. Finally, we discussed the future perspective of the Ag₃PO₄.

1.1. Structure of Ag₃PO₄ for Photocatalysis Activity

Ma and coworkers reported the structural features and photocatalytic activity of the Ag₃PO₄ by using first-principle density functional theory (DFT) [21]. They investigated the energy band structure and density of the state of the Ag₃PO₄, which were essential for photocatalysis to harness solar energy for oxidizing water and degrading pollutants inside wastewater. The crystal structure of Ag₃PO₄ embraces isolated, regular PO₄ tetrahedral with a P-O distance of ~1.539 angstroms (A°). The six Ag⁺ ions dispersed among twelve sites of 2-fold symmetry are shown in Figure 2. With the advancement of X-ray diffraction (XRD) technology, it established that it belongs to the body-centered cubic (bcc) structure type with a lattice parameter of 6.004 A°, and the space group is P4n [20]. The electronic structure was also studied by hybrid DFT to obtain the high photocatalytic efficiency of Ag₃PO₄.

The band structure edge had determined by Perdew-Burke-Ernzerhof’s (PBE) generalized gradient approximation techniques, and its magnified view is nearly Fermi-level depicted in the following Figures 3(a) and 3(b). Both valance band edge maximum (VBEM) and conduction band edge minimum (CBEM) are located at point . Figure 3(b) ascribes that the direct bandgap is equal to 2.61 eV for Ag₃PO₄. The indirect bandgap is equivalent to 2.43 eV found between points and . Therefore, the Ag₃PO₄ is indirect band gap which is equal to 2.43 eV. As indicated in Figure 3(c), the valance band edge potential of eV vs. NHE is more positive than the oxidation potential of water (H₂O/O₂ (1.23 eV vs. NHE)), so it is attributed to the oxidation of water by a hole in the valance band to produce oxygen and oxidized organic pollutants. The conduction band edge minimum (CBEM) is 0.24 which is more positive than H⁺/H₂ and the single electron reaction process. As result, it is not produced hydrogen for energy production and superoxide radical (O^-2) for photodegradation [22]. Umezawa and coworkers showed that the conduction band edge minimum (CBEM) was composed of hybridized Ag (5s, 5p) along with some P (3s) orbitals, while the valance band edge (EVB) was composed of the hybridized (4d) orbitals of Ag and 2p orbitals of oxygen as indicated in Figure 3(c) [23]. Owing to this unique structure and properties of Ag₃PO₄, it is regarded as a good photocatalytic activity in visible light.

(a)

(b)

(c)

1.2. Factors Affecting the Photocatalysis Activity of Ag₃PO₄

The size, shape, and exposed facet of Ag₃PO₄ affect the photodegradation of organic dyes from aqueous solutions [24, 25]. Therefore, controlling the morphology and crystal facet of Ag₃PO₄ during synthesis has improved its photocatalysis efficiency [25]. Dong and a coworker reported the effect of different morphology of Ag₃PO₄ on photocatalytic activities. These morphologies such as branched, tetra-pod, nanorod, and triangular were synthesized by the mixture of dimethyl flour (DMF) and water (H₂O) solvent without using any kind of template materials under the different conditions as elucidated in Figure 4(a), and their SEM images revealed in Figure 4(b). The measured BET specific surfaces of different shapes are as follows: branched (18.9 m²/g), tetrapod (3.35m²/g), nanorod shaped (14.9 m²/g), triangular-prism shaped (2.18m²/g), and irregular spherical Ag₃PO₄ (1.02m²/g) surface area. The efficiency of degrading MB and RhB dyes was higher for branched ones since it has a high surface area to adsorb a large number of dyes which offered a high degradation ability of methylene blue (MB) and rhodamine blue (RhB) for branched as shown in Figures 5(a) and 5(b) [26].

(a)

(b)

(a)

(b)

Various shapes and facets of Ag₃PO₄ crystals have different photocatalysis efficiency. For example, Bi and coworkers synthesize a single crystalline Ag₃PO₄ dodecahedron with only {110} facets and cubes with {100} facets by facile precipitation methods as shown in Figure 6(a).The dodecahedron was synthesized by a reaction between CH₃COOAg and Na₂HPO₄ while the cubic was formed by a reaction between [Ag(NH₃)₂] ⁺ and Na₂HPO₄. As revealed in Figure 6(b), an SEM image of dodecahedrons of Ag₃PO₄ microcrystals bounded by twelve (110) planes, but smooth corners and edges of cubic crystals enclosed by (100) planes. Furthermore, the evaluated photocatalytic performance of rhombic dodecahedrons was higher than cubes for the degradation of organic contaminants as shown in Figure 6(c), which may be due to the higher surface energy of (110) facets (1.31 J/m²) than of {100} facets (1.12 J/m²) which impart a high active site to adsorb organic dyes to degrade [27].

(a)

(b)

(c)

In addition to the above factors, catalyst dose, pH of the solution, and initial dye concentrations also have enormous impacts on photocatalysis efficiency [28]. The catalyst dose refers to the number of photocatalysts in the solutions. Thus, increasing catalyst dosage increases the active site on the surface of the catalyst which causes the formation of more reactive species. As a result, the photodegradation activities increase with an increase in catalyst dosage till the optimum amount is reached; beyond this, the solution becomes turbid and prevented the solar light that reaching the active site, and therefore, degradation efficiency starts to decrease [29]. Furthermore, the dye degradation efficiency depends on the pH values of wastewater. At low pH values, the surface of the Ag₃PO₄ is protonated and becomes positively charged since the initial Ag₃pO₄ has a negative surface charge according to the analysis of its negative zeta potential by Huang et al. [21], and it is easily protonated. As a result, it is efficient to degrade negatively charged organic dyes. Similarly, at high pH values of the solution, the surface of the Ag₃PO₄ becomes negatively charged, and it is effective to degrade cationic dyes [22]. And also, an increase in initial dye concentration decreases the photocatalytic activities because covering the active site of Ag₃PO₄ resulted in low solar light available on the surface of the catalyst, and therefore, low reactive species were formed, thus causing low degradation percentage [23, 30]. As increasing irradiation times more electron-hole pairs were generated, and more reactive species were generated. As a result, the degradation efficiency is increasing with irradiation time [22].

2. Common Challenges to Enhancing Photocatalytic Activities of Ag₃PO₄ Nanoparticles

Figure 7 shows the common challenges to promoting the dye degradation efficiency of Ag₃PO₄. Photocorrosion, instability, and high recombination rate are the main challenges to enhancing the degradation efficiency of Ag₃PO₄. Photocorrosion reduces photocatalytic activities of Ag₃PO₄ by covering the active sites of Ag₃PO₄ with black silver metals. These black silver metals formed when the silver ions in an interstitial site of Ag₃PO₄ accept the excited electrons and then reduced them to silver metals. Then, those silver metals can cover the surface of Ag₃PO₄. As a result, the photocatalyst of Ag₃PO₄ declined [15]. Instability of Ag₃PO₄ is related to a decomposing of Ag₃PO₄ in an aqueous solution, at high thermal heating and long irradiated light, so instability or photocorrosion of Ag₃PO₄ is limited the use of Ag₃PO₄ in practical application [31]. The recombination rates of photoexcited electrons and holes of Ag₃PO₄ also reduce the photocatalytic activity of Ag₃PO₄ owing to there being no scavenger of electrons and holes to suppress the reunion photogenerated charge carriers.

3. Methods for Enhancing Photocatalysis Activity of Ag₃PO₄

3.1. Loading Noble Metal on the Surface of Ag₃PO₄

Loading noble metal on the surface of Ag₃PO₄ is the method to enhance the photocatalytic activities of Ag₃PO₄ because the noble metal loaded on the surface of Ag₃PO₄ acts as an electron scavenger [32]. This means the excited electrons from the valence band are removed from the Ag₃PO₄ by noble metal so that there is no further recombination of charge carriers and suppresses photocorrosion because the excited electron does not get interstitial Ag⁺ ions to form black Ag metal covers the active sites of Ag₃PO₄ which is reducing the absorption of light and adsorption of dyes to the active site of Ag₃PO₄ and leads to depletion of photocatalytic activity to degradation dyes from aqueous solution [33]. For instance, Figure 8 shows that decorating of platinum (pt) on the surface of Ag₃PO₄ highly enhances the stability of Ag₃PO₄ which has exhibited better efficiency when it is used for six consecutive runs [34]. However, the performance of neat Ag₃PO₄ deteriorated when it had been used for a six repeating runs due to the gradual decomposition of Ag₃PO₄ to weakly active Ag nanoparticle which is the main cause for instability and photocorrosion of Ag₃PO₄ [34, 35].

(a)

(b)

(c)

(d)

(e)

(f)

The aforementioned advantages were accomplished as follows. The loaded noble metals on Ag₃PO₄ formed Schottky-type heterostructures as depicted in Figure 9(a). Since the contact between metal and semiconductor forms the Schottky barrier at their interface owing to the difference in work functions [36], the work function of Ag₃PO₄ conduction band edge (CBE), Au, Pd, and Pt is 4.95, 5.1, 5.12, and 5.65 eV, respectively [34, 37] since Ag₃PO₄ n-type semiconductor and its Fermi level are close to the conduction band edge. When noble metal contacts with Ag₃PO₄, the electrons flow from semiconductor to metals to attain two systems at the equilibrium, and a new Fermi level is established, and the internal electric field directed from Ag₃PO₄ to metal was formed. When the (Au, Pd, Pt)/Ag₃PO₄ heterostructure is imposed to visible light, the electron in the VB excited to CB and by forming a hole at VB, and electrons in the CB easily flow to metals owing to CB of Ag₃PO₄ at higher potential and also an internal electric field-assisted the flow electron from Ag₃PO₄ to metals. As result, the charge recombination rate and the instability of Ag₃PO₄ are effectively suppressed [34]. The electron reacted with oxgen and form O^2- reactive species that able to decompose organic pollutants. The holes left in VB have proceeded an oxidization reaction to decompose organic dyes as depicted in Figure 9(b).

(a)

(b)

In addition to those benefits, noble metal nanoparticles loaded on the surface of Ag₃PO₄ revealed remarkable enhancement absorption of both UV and visible light than pure Ag₃PO₄ as indicated in Figure 10. This can be the attribution of localized surface plasmon resonance effect (LSPR) of noble metal loaded on the surface of Ag₃PO₄ in which a vibrational frequency of coming electromagnetic radiation matches with the vibration frequency of the electrons in the noble metals which help to harvest a large amount of coming light [38]. These have improved the photocatalytic activity of Ag₃PO₄ [34]. As shown in Table 1, many reported works on the loading of noble metal on surface Ag₃PO₄ to enhance the photocatalytic activities of Ag₃PO₄ are listed.

Different noble metals have a different effects on enhancing photocatalytic activities of Ag₃PO₄ because of their various specific properties. Figure 11(a) shows the enhancement of photocatalytic activities of the Ag₃PO₄ by loading noble metals, and a comparative study of the photocatalytic activities of various noble metals loaded on the surface of Ag₃PO₄ and with other photocatalyst materials. As indicated in this Figure 11(a), different noble metals loaded on Ag₃PO₄ show unequal performances because they do have not equal work functions. The large differences in work function between the noble metals and Ag₃PO₄ are necessary for a better photocatalytic process, because it facilitates a transfer of a photogenerated electron from Ag₃PO₄ to noble metals. So, the degrading ability of dyes by Pt/Ag₃PO₄ is larger than the other two noble metals due to Pt having a large work function difference with the conduction band edge of Ag₃PO₄ as shown in Figure 9(a) which highly assists the electron transfer from Ag₃PO₄ to Pt. As a result, the photodegradation Pt loaded on Ag₃PO₄ is higher than the other two noble metals and bare Ag₃PO₄ [39]. In general, as indicated in Figure 11(a), the degradation of the dye by noble metal loaded on the surface of Ag₃PO₄ was better when compared to the bare one due to the aforementioned reason [34]. Moreover, Figure 11(b) shows that the efficiency of degrading different types of dyes by identical photocatalysts is not the same owing to the structure, and the surface charge difference has existed between the given dyes [40], and the surface charge of Ag₃PO₄ negative due to it has plenty OH^-(hydroxyl group) [41] which helped to adsorb highly cationic dyes.

(a)

(b)

3.2. Forming Binary Ag₃PO₄ Composite with Semiconductor and Supported Material

There are different methods to enhance the photocatalytic activity of a given semiconductor among as forming heterojunctions with another semiconductor [42], which is provided the following advantages to improve photocatalysis performance such as (1) reducing the recombination of photogenerated charge carriers by transferring electrons and holes between a junction, and as result, the formation of reactive oxidative species increased which was decontaminated organic dyes from wastewater [39]; (2) extending the absorption of solar light for large bandgap semiconductors when combined with small bandgap semiconductors [43]; (3) improve stability issue of a single component; and (4) forming nanoheterostructure semiconductors has a large surface area and enough active sites to adsorbed organic dyes.

Therefore, coupling Ag₃PO₄ with other semiconductors is among the methods to enhance the photocatalytic activities of Ag₃PO₄. The main advantageous form heterojunctions with Ag₃PO₄ are as follows: (i) solving instability issues and reducing the photocorrosion, (ii) improving the absorption of solar light in the visible range, and (iii) suppressing the recombination of charge carriers [39, 44, 45]. For instance, Figure 12 reveals the composite of Co₃O₄/Ag₃PO₄ in which a heterojunction was formed between Co₃O₄ and Ag loaded on Ag₃PO₄ in which silver metal appeared on the surface of Ag₃PO₄ during the photocatalysis process [44]. As indicated in this Figure 12, the photoexcited electrons and holes transferred Ag and Co₃O₄, respectively. As a result, there is no recombination of holes-electrons and photocorrosion because both charge carriers have not stayed on the Ag₃PO₄ after photoexcitation has been done. The solar absorption of mentioned heterojunction is better than a single component.

Bi and coworkers decorated the silver halides as core-shell on the surface of rhombic dodecahedral Ag₃PO₄ by the ion change method, and as we knew, the Ag₃PO₄ has rhombic dodecahedral morphology that has high surface energy which makes it dissolve in solution [45]. The intention of decorating Ag₃PO₄ is to prevent dissolution and enhance the stability of Ag₃PO₄ during photocatalyst activity since silver halides have lower solubility in aqueous solution than pristine Ag₃PO₄. As well as, the valance band and conduction band of all halides are less negative than Ag₃PO₄ except Cl, so that the separation of charge carriers increases, and the recombination rate may be significantly reduced. In addition to this, the photocorrosion was inhibited for Ag (Br, I)/Ag₃PO₄ by facilitated multiple-electron reduction reaction of oxygen () [46] at Ag₃PO₄ without photoreduction of silver ions into black silver metals. As a result, photodegradation of organic dyes by Ag₃PO₄ was enhanced as shown in Figure 13.

Supporting materials such as cellulose, graphene, and other porous materials have been used with Ag₃PO₄. These supporting materials increases the photocatalytic activities of Ag₃PO₄ by improving the surface area, morphology and reducing agglomerations of Ag₃PO₄. Based on this concept, Yang and coworkers synthesized Ag₃PO₄/graphene oxide nanocomposite by simple precipitation methods and subsequently reduced graphene oxide to reduce graphene to form Ag₃PO₄/reduced graphene oxide nanocomposite. As a result, the morphology and size were controlled according to synthesis techniques illustrated in Figure 14(a). In addition to these, the conductive property of graphene inhibited recombination e^--h⁺ pairs by charge transferring between Ag₃PO₄ and graphene as indicated in Figure 14(c). Due to the above reason, the photodegradation of organic dyes by Ag₃PO₄/graphene-based nanocomposite is excellent when compared to bare Ag₃PO₄ as shown in Figure 14(b). To check the stability of Ag₃PO₄ and Ag₃PO₄/GR, the XRD characterization was recorded according to Figure 14(d) after a photocatalysis activity. It is observed that Ag metals appeared for Ag₃PO₄ which is the main cause for photocorrosion but not appeared for composite owing to the electron in an Ag₃PO₄ transferring to graphene sheet as indicated in Figure 14(c) before it combined with Ag⁺ ions to form black silver metals. Therefore, combining Ag₃PO₄ with graphene-based materials has reduced photocorrosion to a large extent [47]. Further, Table 2 shows the lists of published works on Ag₃PO₄/metal oxide semiconductor or supporting materials for dye degradation.

(a)

(b)

(c)

(d)

The photocatalytic activity toward degradation of organic dyes from aqueous solution was also enhanced when Ag₃PO₄ was combined within a different dimension (1D, 2D, 3D) semiconductor materials [48] which were reviewed in the following Table 3. Various morphology of semiconductors offers special properties for the materials such as increased surface area by reducing agglomeration, increasing charge transferring between the junction for transporting and separation photogenerated electron-hole pairs, and serving as a superior template for hetero growth of Ag₃PO₄ [1, 49, 50].

3.3. Ag₃PO₄-Based Ternary Nanocomposite for Degrading Dyes from Wastewater

Ternary nanocomposite types of the composite are formed when three semiconductors that have matched band structures are combined, and also, ternary composite is formed when the binary composite is clumped together with supporting materials like graphene, cellulose, etc. In ternary composite, the synthesized materials have synergetic performance and properties of three single components thus resulting in highly inhibited recombination of charge carriers since the time of recombination has elongated by easily transferring charge carriers between the junction of three semiconductors. In addition to these, the stability and absorption of light are highly enhanced than single and binary components, and therefore, the photodegradation of organic dyes by ternary is higher than in single and binary materials [51].

So, forming Ag₃PO₄ containing ternary nanocomposites improved the degradation efficiency of Ag₃PO₄. Among these materials, one is the Ag₃PO₄. And other two materials are used to enhance the photostability and photocatalytic activities of Ag₃PO₄. Using ternary nanocomposites has resulted in a reduction in the consumption of expensive noble metals. Among the three ternary nanocomposites, one of them may be magnetic or supporting materials. The magnetic material enhances the photocatalytic activities as well as the recoverability of Ag₃PO₄. A typical example of the photocatalytic activities of ternary nanocomposites is shown in Figure 15. As revealed in Figure 15, the conduction band edge and valance band edge of WO₃ are more positive than the conduction band edge and valance band edge of Ag₃PO₄, and their bandgap is 2.44 eV and 2.35 eV for WO₃ and Ag₃PO₄, respectively. So, electron-hole pairs were generated under visible light for both semiconductors, and also, the electron migrates from Ag₃PO₄ CB(conduction band) to WO₃ CB (conduction band), and the hole migrated from the valance band (VB) of WO₃ to the valance band (VB) of Ag₃PO₄. After that, the holes oxidized organic dyes adsorbed on the surface of Ag₃PO₄, and the electrons were consumed via proceeding multioxidation reaction with oxygen O₂+2H⁺ + 2e⁻ ⟶ H₂O₂, V vs. NHE. Further, the produced H₂O₂ reacted with electrons and produced hydroxyl radical ^̊OH (H₂O₂ + e⁻ ⟶ OH⁻ + ^̊OH) which participated degradation of organic dyes from aqueous solution, and the Fe₂O₃ in the composite acts as a mediator for electron transfer from Ag₃PO₃ to WO₃ and also its scale number of recyclability of catalyst for practical application [52]. Moreover, some of the lists of published articles on Ag₃PO₄ based on ternary nanocomposite for degradation of dyes are explained in Table 4.

And also, the magnetically separable Ag₃PO₄/CoFe₂O₄/GO composite reported by Chao and his coworkers was synthesized by an efficient precipitation method with different mass ratios of Ag₃PO₄ to CoFe₂O₄/GO. The Ag3PO4/MG-15% photocatalysts showed better photocatalytic activity than bare Ag₃PO₄; under Ag₃PO₄/MG-15%, 91% of MO is degraded, while under the same condition, only 36% of MO was degraded by the bare Ag₃PO₄ after 15 min of light irradiation, and also, Ag₃PO₄/CoFe₂O₄/GO shows good recyclability when compared to bare Ag₃PO₄ as evidenced in Figure 16(a) [53]. As explained in Figure 16(b) the photocatalytic mechanism of ternary is like the following. Firstly, the composite was irradiated with visible light; electrons were excited from VB to the CB in both CoFe₂O₄. At the same time, electrons transferred from CB of CoFe₂O₄ to CB of Ag₃PO₄ and reduced the oxygen adsorbed on the surface of the catalyst and formed O^-o₂ radical, and holes transferred from the valance band of Ag₃PO₄ to the valance band of CoFe₂O₄. Superoxide (O^-o₂) radical degrades MO dyes. The holes simultaneous oxidize MO directly into carbon dioxide and water molecules and the photoreaction; the e^--h⁺ pairs could be separated with ease due to the high electron transfer capacity of GO [54].

(a)

(b)

The hierarchical Ag₃PO₃/TiO₂/Fe₃O₄ nanocomposite structure shows high photocatalytic activity, high stability, and good recyclability than Ag₃PO₄ toward degradation of AO7 dyes from wastewater due to high photogenerated charge separation which attribution of TiO₂ and Ag⁺ ions that produced by photoinduced electron and inhibit the further decomposition of Ag₃PO₄. The Fe₃O₄ helps for separation after being used for photocatalytic activity. The performance achieved by this material is around 97% toward degradation of AO7 dyes [55]. Li et al. reported the ZnFe₂O₄-ZnO-Ag₃PO₄ hollow nanospheres synthesized by using phenolic formaldehyde microspheres as a template via an impregnating-calcination process. And it shows good photocatalytic activity toward mineralization of organic pollutants inside wastewater owing to the high surface area; small particle size is achieved. As shown in Figure 17, cascade electron transfer from CB of ZnFe₃O₄ to ZnO to Ag₃PO₄ is enhanced charge separation. And due to the small particle size that is difficult to separate after being used for photocatalysis activity, so by using external magnetic, it is easily separated because ZnFe₃O₄ has a magnetic property [56].

3.3.1. Photocatalysis Mechanisms in a Semiconductor to Decontaminate Organic Dyes

Photoreaction is essential to complete mineralization of organic pollutants from an aqueous solution at ambient temperature and pressure without introducing secondary pollutants. Under this part, we discussed the photoreaction pathway for any semiconductor materials used for photodegradation. The photodegradation of organic dyes is a redox reaction in which reduction reaction and oxidation reaction take place in the conduction and valance band, respectively. The process of photoreaction is divided into three steps. First, the electron (e^-) and hole (h⁺) pairs are generated by photon energy greater than or equal to the bandgap of the semiconductor, and the electrons transfer from VB to CB by leaving a vacant electron site (hole) in a VB. Second, the photo-induced electron and hole reacted with oxygen and water to form superoxide radicals (O₂^-o) and hydroxyl radicals (^oOH), respectively, according to Equations (2) and (4). Further superoxide radicals reacted with H₂O and form hydroperoxyl radicals (HO₂^o) according to (Equation (3)). Thirdly, these formed superoxide radicals (O₂^-o), hydroxyl radicals (^oOH), and hydroperoxyl radicals (HO₂^o) oxidized organic dyes and converted them into CO₂ and H₂O which is not a secondary pollutant. The overall mechanisms of photodegradation of organic dyes are elucidated in Figure 18 [57].

3.3.2. Future Perspective and the Opinion of the Reviewer

All the mentioned methods had been used as supportive material to reduce the limitation of the Ag₃PO₄ which are photocorrosion, instability, and high recombination rate. However, they have not stated the cost of a precursor used to synthesize Ag₃PO₄, but the precursor used for fabricated Ag₃PO₄ is expensive. So, we will suggest that replacing the Ag₃PO₄ precursor with a less-cost precursor will improve the availability and efficiency of Ag₃PO₄ for photocatalysis applications. Especially, extracting a precursor from waste by-products and naturally occurring materials enhances the nobility and application of Ag₃PO₄ for photodegradation. For instance, eggshells (ES) and bones are rich in phosphate so we can use them as precursors for synthesizing Ag₃PO₄. Synthesizing of Ag₃PO₄/supporting materials used to reduce agglomeration. For instance, silicate can be extracted from bagasse ash which is a by-product of sugar cane because it is cost-wise and available everywhere in the sugar industry. Doping of large bandgap semiconductors such as ZnO and TiO₂ is crucial to reducing the wideband to narrow bandgap that enables them to harvest the visible light while a couple with Ag₃PO₄. Thus, the doped wide-bandgap oxides not only reduce the limitation of the Ag₃PO₄ but also actively participate in the degradation of the organic dyes in the wastewater.

4. Conclusion

Nano-scaled metal oxide semiconductors have many applications due to their unique properties. The photocatalyst is among the wastewater treatment methods, where nano-scaled semiconductors have been used as a catalyst. Among the metal oxide semiconductors, Ag₃PO₄ gain significant attention due to its lower bandgap and visible light-absorbing efficiency of up to 95%. However, due to high photocorrosion, instability, and high recombination rate, the photocatalytic activities of Ag₃PO₄ are getting lower. Such factors which hinder the photocatalytic activity of Ag₃PO₄ can be overcommed by using Noble metal loaded Ag₃PO₄, forming binary composition such as Ag₃PO₄/metal oxides or supporting matarials, Ag₃PO₄-based ternary nanocomposite,and changing the morphology of Ag₃PO₄. From all the possible approaches, the mentioned limitations of Ag₃PO₄ were minimized, and the degradation efficiency of the organic dyes in the wastewater was enhanced. Therefore, the Ag₃PO₄ with reduced photocorrosion, instability, and recombination rate is a promising agent to degrade organic dye from wastewater.

Data Availability

The data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

The authors thank the Material Science and Engineering Department, Adama Science and Technology University (Adama, Ethiopia), for providing us support while we were developing these articles.

References

S. Shenoy, S. Ahmed, I. M. C. Lo, S. Singh, and K. Sridharan, “Rapid sonochemical synthesis of copper doped ZnO grafted on graphene as a multi-component hierarchically structured visible-light-driven photocatalyst,” Materials Research Bulletin, vol. 140, article 111290, 2021.
View at: Publisher Site | Google Scholar
C. A. Martínez-Huitle and E. Brillas, “Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods: a general review,” Applied Catalysis B: Environmental, vol. 87, no. 3-4, pp. 105–145, 2009.
View at: Publisher Site | Google Scholar
S. Shenoy, K. Tarafder, and K. Sridharan, “Bimetallic nanoparticles grafted ZnO hierarchical structures as efficient visible light driven photocatalyst: an experimental and theoretical study,” Journal of Molecular Structure, vol. 1236, article 130355, 2021.
View at: Publisher Site | Google Scholar
J. Acharya, J. N. Sahu, B. K. Sahoo, C. R. Mohanty, and B. C. Meikap, “Removal of chromium(VI) from wastewater by activated carbon developed from Tamarind wood activated with zinc chloride,” Chemical Engineering Journal, vol. 150, no. 1, pp. 25–39, 2009.
View at: Publisher Site | Google Scholar
J. Hollender, S. G. Zimmermann, S. Koepke et al., “Elimination of organic micropollutants in a municipal wastewater treatment plant upgraded with a full-scale post-ozonation followed by sand filtration,” Environmental Science & Technology, vol. 43, no. 20, pp. 7862–7869, 2009.
View at: Publisher Site | Google Scholar
A. Y. Zahrim and N. Hilal, “Treatment of highly concentrated dye solution by coagulation/flocculation-sand filtration and nanofiltration,” Water Resources and Industry, vol. 3, pp. 23–34, 2013.
View at: Publisher Site | Google Scholar
M. Elsayed and M. E.-S. Abdel-Raouf, “Wastewater treatment methodologies, Review Article,” Int J Environ & Agri Sci, vol. 3, p. 18, 2019.
View at: Google Scholar
S.-Y. Lee and S.-J. Park, “TiO₂ photocatalyst for water treatment applications,” Journal of Industrial and Engineering Chemistry, vol. 19, no. 6, pp. 1761–1769, 2013.
View at: Publisher Site | Google Scholar
N. N. Fathima, R. Aravindhan, J. R. Rao, and B. U. Nair, “Dye house wastewater treatment through advanced oxidation process using Cu- exchanged Y zeolite: a heterogeneous catalytic approach,” Chemosphere, vol. 70, no. 6, pp. 1146–1151, 2008.
View at: Publisher Site | Google Scholar
A. Ibhadon and P. Fitzpatrick, “Heterogeneous photocatalysis: recent advances and applications,” Catalysts, vol. 3, no. 1, pp. 189–218, 2013.
View at: Publisher Site | Google Scholar
H. Chen and L. Wang, “Nanostructure sensitization of transition metal oxides for visible-light photocatalysis,” Beilstein Journal of Nanotechnology, vol. 5, pp. 696–710, 2014.
View at: Publisher Site | Google Scholar
A. Fujishima and K. Honda, “Electrochemical photolysis of water at a semiconductor electrode,” Nature, vol. 238, no. 5358, pp. 37-38, 1972.
View at: Publisher Site | Google Scholar
Z. Yi, J. Ye, N. Kikugawa et al., “An orthophosphate semiconductor with photooxidation properties under visible-light irradiation,” Nature Materials, vol. 9, no. 7, pp. 559–564, 2010.
View at: Publisher Site | Google Scholar
J. Li, X. Ji, X. Li et al., “Preparation and photocatalytic degradation performance of Ag₃PO₄ with a two-step approach,” Applied Surface Science, vol. 372, pp. 30–35, 2016.
View at: Publisher Site | Google Scholar
Y. Luo, N. Xu, X. Liu, L. Yang, H. Wu, and Y. Qin, “Photoactivity enhanced and photo-corrosion inhibited Ag₃PO₄/ZnO visible light photocatalyst for the degradation of rhodamine B,” Energy and Environment Focus, vol. 4, no. 2, pp. 121–127, 2015.
View at: Publisher Site | Google Scholar
J.-D. Wang, F. R. Wang, J. K. Liu, X. H. Yang, and X. H. Zhong, “Controlled synthesis and characterizations of thermo-stabilized Ag₃PO₄ crystals,” Research on Chemical Intermediates, vol. 42, no. 12, pp. 8285–8304, 2016.
View at: Publisher Site | Google Scholar
S. Thangaraj Nishanthi, Photocatalytic Functional Materials for Environmental Remediation, John Wiley & Sons Inc, 2019.
P. Riente and T. Noël, “Application of metal oxide semiconductors in light-driven organic transformations,” Catalysis Science & Technology, vol. 9, no. 19, pp. 5186–5232, 2019.
View at: Publisher Site | Google Scholar
G. Kiriakidis and V. Binas, “Metal oxide semiconductors as visible light photocatalysts,” Journal of the Korean Physical Society, vol. 65, no. 3, pp. 297–302, 2014.
View at: Publisher Site | Google Scholar
X. Ma, B. Lu, D. Li, R. Shi, C. Pan, and Y. Zhu, “Origin of photocatalytic activation of silver orthophosphate from first-principles,” The Journal of Physical Chemistry C, vol. 115, no. 11, pp. 4680–4687, 2011.
View at: Publisher Site | Google Scholar
K. Huang, Y. Lv, W. Zhang et al., “One-step synthesis of Ag₃PO₄/Ag photocatalyst with visible-light photocatalytic activity,” Materials Research, vol. 18, no. 5, pp. 939–945, 2015.
View at: Publisher Site | Google Scholar
A. M. Taddesse, M. Alemu, and T. Kebede, “Enhanced photocatalytic activity of p-n-n heterojunctions ternary composite Cu₂O/ZnO/Ag₃PO₄ under visible light irradiation,” Journal of Environmental Chemical Engineering, vol. 8, no. 5, article 104356, 2020.
View at: Publisher Site | Google Scholar
K. M. Reza, A. S. W. Kurny, and F. Gulshan, “Parameters affecting the photocatalytic degradation of dyes using TiO₂: a review,” Applied Water Science, vol. 7, no. 4, pp. 1569–1578, 2017.
View at: Publisher Site | Google Scholar
Y. Bi, H. Hu, S. Ouyang, Z. Jiao, G. Lu, and J. Ye, “Selective growth of metallic Ag nanocrystals on Ag₃PO₄ submicro-cubes for photocatalytic applications,” Chemistry - A European Journal, vol. 18, no. 45, pp. 14272–14275, 2012.
View at: Publisher Site | Google Scholar
T. A. Vu, C. D. Dao, T. T. T. Hoang et al., “Highly photocatalytic activity of novel nano-sized Ag₃PO₄ for rhodamine B degradation under visible light irradiation,” Materials Letters, vol. 92, pp. 57–60, 2013.
View at: Publisher Site | Google Scholar
P. Dong, Y. Wang, H. Li, H. Li, X. Ma, and L. Han, “Shape-controllable synthesis and morphology-dependent photocatalytic properties of Ag₃PO₄ crystals,” Journal of Materials Chemistry A, vol. 1, no. 15, p. 4651, 2013.
View at: Publisher Site | Google Scholar
Y. Bi, S. Ouyang, N. Umezawa, J. Cao, and J. Ye, “Facet effect of single-crystalline Ag₃PO₄ sub-microcrystals on photocatalytic properties,” Journal of the American Chemical Society, vol. 133, no. 17, pp. 6490–6492, 2011.
View at: Publisher Site | Google Scholar
A. Kumar, “A review on the factors affecting the photocatalytic degradation of hazardous materials,” Material Science & Engineering International Journal, vol. 1, no. 3, 2017.
View at: Publisher Site | Google Scholar
H. M. Coleman, V. Vimonses, G. Leslie, and R. Amal, “Degradation of 1,4-dioxane in water using TiO₂ based photocatalytic and H₂O₂/UV processes,” Journal of Hazardous Materials, vol. 146, no. 3, pp. 496–501, 2007.
View at: Publisher Site | Google Scholar
M. Al Kausor, S. S. Gupta, and D. Chakrabortty, “Ag₃PO₄-based nanocomposites and their applications in photodegradation of toxic organic dye contaminated wastewater: review on material design to performance enhancement,” Journal of Saudi Chemical Society, vol. 24, no. 1, pp. 20–41, 2020.
View at: Publisher Site | Google Scholar
J. Tang, R. Meng, Q. Wang, S. Zhang, and Q. Li, “Fabrication and photocatalytic activity of Ag₃PO₄/T-ZnOw heterostructures,” Nanoscale Research Letters, vol. 15, no. 1, p. 131, 2020.
View at: Publisher Site | Google Scholar
H. Einaga, S. Futamura, and T. Ibusuki, “Complete oxidation of benzene in gas phase by platinized titania photocatalysts,” Environmental Science & Technology, vol. 35, no. 9, pp. 1880–1884, 2001.
View at: Publisher Site | Google Scholar
Y. Bi, H. Hu, S. Ouyang, Z. Jiao, G. Lu, and J. Ye, “Selective growth of Ag₃PO₄ submicro-cubes on Ag nanowires to fabricate necklace-like heterostructures for photocatalytic applications,” Journal of Materials Chemistry, vol. 22, no. 30, p. 14847, 2012.
View at: Publisher Site | Google Scholar
T. Yan, H. Zhang, Y. Liu et al., “Fabrication of robust M/Ag₃PO₄(M = Pt, Pd, Au) Schottky-type heterostructures for improved visible-light photocatalysis,” RSC Advances, vol. 4, no. 70, p. 37220, 2014.
View at: Publisher Site | Google Scholar
H. Wang, Y. Bai, J. Yang, X. Lang, J. Li, and L. Guo, “A facile way to rejuvenate Ag₃PO₄ as a recyclable highly efficient photocatalyst,” Chemistry, vol. 18, no. 18, pp. 5524–5529, 2012.
View at: Publisher Site | Google Scholar
H. Chen, S. Chen, X. Quan, H. Yu, H. Zhao, and Y. Zhang, “Fabrication of TiO₂−Pt coaxial nanotube array Schottky structures for enhanced photocatalytic degradation of phenol in aqueous solution,” The Journal of Physical Chemistry C, vol. 112, no. 25, pp. 9285–9290, 2008.
View at: Publisher Site | Google Scholar
P. Dong, Y. Wang, B. Cao et al., “Ag₃PO₄/reduced graphite oxide sheets nanocomposites with highly enhanced visible light photocatalytic activity and stability,” Applied Catalysis B: Environmental, vol. 132-133, pp. 45–53, 2013.
View at: Publisher Site | Google Scholar
J. Li, Z. Lou, and B. Li, “Nanostructured materials with localized surface plasmon resonance for photocatalysis,” Chinese Chemical Letters, vol. 33, no. 3, pp. 1154–1168, 2022.
View at: Publisher Site | Google Scholar
Y. Yu, B. Yao, Y. He, B. Cao, Y. Ren, and Q. Sun, “Piezo-enhanced photodegradation of organic pollutants on Ag₃PO₄/ZnO nanowires using visible light and ultrasonic,” Applied Surface Science, vol. 528, article 146819, 2020.
View at: Publisher Site | Google Scholar
A. Kudo, K. Omori, and H. Kato, “A novel aqueous process for preparation of crystal form-controlled and highly crystalline BiVO₄ powder from layered vanadates at room temperature and its photocatalytic and photophysical properties,” Journal of the American Chemical Society, vol. 121, no. 49, pp. 11459–11467, 1999.
View at: Publisher Site | Google Scholar
Q. Liang, Y. Shi, W. Ma, Z. Li, and X. Yang, “Enhanced photocatalytic activity and structural stability by hybridizing Ag₃PO₄ nanospheres with graphene oxide sheets,” Physical Chemistry Chemical Physics, vol. 14, no. 45, pp. 15657–15665, 2012.
View at: Publisher Site | Google Scholar
H. Li, H. Hu, C. Bao et al., “Forming heterojunction: an effective strategy to enhance the photocatalytic efficiency of a new metal-free organic photocatalyst for water splitting,” Scientific Reports, vol. 6, no. 1, p. 29327, 2016.
View at: Publisher Site | Google Scholar
L. Zhou, W. Zhang, L. Chen, and H. Deng, “Z-scheme mechanism of photogenerated carriers for hybrid photocatalyst Ag₃PO₄/g-C₃N₄ in degradation of sulfamethoxazole,” Journal of Colloid and Interface Science, vol. 487, pp. 410–417, 2017.
View at: Publisher Site | Google Scholar
C. Tang, E. Liu, J. Wan, X. Hu, and J. Fan, “Co₃O₄ nanoparticles decorated Ag₃PO₄ tetrapods as an efficient visible-light-driven heterojunction photocatalyst,” Applied Catalysis B: Environmental, vol. 181, pp. 707–715, 2016.
View at: Publisher Site | Google Scholar
Y. Bi, S. Ouyang, J. Cao, and J. Ye, “Facile synthesis of rhombic dodecahedral AgX/Ag₃PO₄ (X = Cl, Br, I) heterocrystals with enhanced photocatalytic properties and stabilities,” Physical Chemistry Chemical Physics, vol. 13, no. 21, pp. 10071–10075, 2011.
View at: Publisher Site | Google Scholar
H. Hu, Z. Jiao, T. Wang, J. Ye, G. Lu, and Y. Bi, “Enhanced photocatalytic activity of Ag/Ag₃PO₄ coaxial hetero-nanowires,” Journal of Materials Chemistry A, vol. 1, no. 36, p. 10612, 2013.
View at: Publisher Site | Google Scholar
X. Yang, H. Cui, Y. Li, J. Qin, R. Zhang, and H. Tang, “Fabrication of Ag₃PO₄-graphene composites with highly efficient and stable visible light photocatalytic performance,” ACS Catalysis, vol. 3, no. 3, pp. 363–369, 2013.
View at: Publisher Site | Google Scholar
S. Shenoy, E. Jang, T. J. Park, C. S. Gopinath, and K. Sridharan, “Cadmium sulfide nanostructures: influence of morphology on the photocatalytic degradation of erioglaucine and hydrogen generation,” Applied Surface Science, vol. 483, pp. 696–705, 2019.
View at: Publisher Site | Google Scholar
P. Wang, P. Shi, Y. Hong, X. Zhou, and W. Yao, “Facile deposition of Ag₃PO₄ on graphene-like MoS₂ nanosheets for highly efficient photocatalysis,” Materials Research Bulletin, vol. 62, pp. 24–29, 2015.
View at: Publisher Site | Google Scholar
K. Sridharan, S. Shenoy, S. G. Kumar, C. Terashima, A. Fujishima, and S. Pitchaimuthu, “Advanced two-dimensional heterojunction photocatalysts of stoichiometric and non-stoichiometric bismuth oxyhalides with graphitic carbon nitride for sustainable energy and environmental applications,” Catalysts, vol. 11, no. 4, p. 426, 2021.
View at: Publisher Site | Google Scholar
P. Zhu, M. Hu, M. Duan, L. Xie, and M. Zhao, “High visible light response Z-scheme Ag₃PO₄ / g-C₃N₄ / ZnO composite photocatalyst for efficient degradation of tetracycline hydrochloride: preparation, properties and mechanism,” Journal of Alloys and Compounds, vol. 840, article 155714, 2020.
View at: Publisher Site | Google Scholar
H. B. Gasmalla, X. Lu, M. I. Shinger, L. Ni, A. N. Chishti, and G. Diao, “Novel magnetically separable of Fe₃O₄/Ag₃PO₄@WO₃ nanocomposites for enhanced photocatalytic and antibacterial activity against Staphylococcus aureus (S. aureus),” J Nanobiotechnology, vol. 17, no. 1, p. 58, 2019.
View at: Publisher Site | Google Scholar
Z. Liu, H. Feng, S. Xue et al., “The triple-component Ag₃PO₄-CoFe₂O₄-GO synthesis and visible light photocatalytic performance,” Applied Surface Science, vol. 458, pp. 880–892, 2018.
View at: Publisher Site | Google Scholar
D. Chao, Y. Liu, and Z. Zhu, “Facile fabrication of magnetically separable Ag₃PO₄/CoFe₂O₄/GO composites with enhanced visible light photocatalytic performance,” Materials Letters, vol. 217, pp. 239–242, 2018.
View at: Publisher Site | Google Scholar
J. W. Xu, Z. D. Gao, K. Han, Y. Liu, and Y. Y. Song, “Synthesis of magnetically separable Ag₃PO₄/TiO₂/Fe₃O₄ heterostructure with enhanced photocatalytic performance under visible light for photoinactivation of bacteria,” ACS Applied Materials & Interfaces, vol. 6, no. 17, pp. 15122–15131, 2014.
View at: Publisher Site | Google Scholar
N. Azbar, T. Yonar, and K. Kestioglu, “Comparison of various advanced oxidation processes and chemical treatment methods for COD and color removal from a polyester and acetate fiber dyeing effluent,” Chemosphere, vol. 55, no. 1, pp. 35–43, 2004.
View at: Publisher Site | Google Scholar
J. Madhavan, J. Theerthagiri, D. Balaji, S. Sunitha, Choi, and M. Ashokkumar, “Hybrid advanced oxidation processes involving ultrasound: an overview,” Molecules, vol. 24, no. 18, p. 3341, 2019.
View at: Publisher Site | Google Scholar
J. J. Liu, X. L. Fu, S. F. Chen, and Y. F. Zhu, “Electronic structure and optical properties of Ag₃PO₄ photocatalyst calculated by hybrid density functional method,” Applied Physics Letters, vol. 99, no. 19, article 191903, 2011.
View at: Publisher Site | Google Scholar
A. Malathi, J. Madhavan, M. Ashokkumar, and P. Arunachalam, “A review on BiVO ₄ photocatalyst: activity enhancement methods for solar photocatalytic applications,” Applied Catalysis A: General, vol. 555, pp. 47–74, 2018.
View at: Google Scholar
W. Teng, X. Li, Q. Zhao, J. Zhao, and D. Zhang, “In situ capture of active species and oxidation mechanism of RhB and MB dyes over sunlight-driven Ag/Ag₃PO₄ plasmonic nanocatalyst,” Applied Catalysis B: Environmental, vol. 125, pp. 538–545, 2012.
View at: Publisher Site | Google Scholar
L. Lebogang, R. Bosigo, K. Lefatshe, and C. Muiva, “Ag₃PO₄/nanocellulose composite for effective sunlight driven photodegradation of organic dyes in wastewater,” Materials Chemistry and Physics, vol. 236, article 121756, 2019.
View at: Publisher Site | Google Scholar
Q. Xiang, D. Lang, T. Shen, and F. Liu, “Graphene-modified nanosized Ag₃PO₄ photocatalysts for enhanced visible-light photocatalytic activity and stability,” Applied Catalysis B: Environmental, vol. 162, pp. 196–203, 2015.
View at: Publisher Site | Google Scholar
P. Wang, Y. Li, Z. Liu et al., “In-situ deposition of Ag₃PO₄ on TiO₂ nanosheets dominated by (001) facets for enhanced photocatalytic activities and recyclability,” Ceramics International, vol. 43, no. 15, pp. 11588–11595, 2017.
View at: Publisher Site | Google Scholar
C. Zhu, Y. Zhao, L. Fang et al., “N-doped carbon quantum dots/Ag₃PO₄ hybrid materials with improved visible light photocatalytic activity and stability,” Materials Letters, vol. 188, pp. 304–307, 2017.
View at: Publisher Site | Google Scholar
J. Zhang, J. Lv, K. Dai, Q. Liu, C. Liang, and G. Zhu, “Facile and green synthesis of novel porous g-C₃N₄/Ag₃PO₄ composite with enhanced visible light photocatalysis,” Ceramics International, vol. 43, no. 1, pp. 1522–1529, 2017.
View at: Publisher Site | Google Scholar
J. Xie, Y. Yang, H. He et al., “Facile synthesis of hierarchical Ag₃PO₄/TiO₂ nanofiber heterostructures with highly enhanced visible light photocatalytic properties,” Applied Surface Science, vol. 355, pp. 921–929, 2015.
View at: Publisher Site | Google Scholar
S. Wan, F. Qi, W. Jin et al., “Construction of ultrafine Ag₃PO₄ nanoparticle and La₂Ti₂O₇ nanosheet 0D/2D heterojunctions with improved photocatalytic performance,” Journal of Alloys and Compounds, vol. 740, pp. 901–909, 2018.
View at: Publisher Site | Google Scholar
P. Ma, Y. Yu, J. Xie, and Z. Fu, “Ag₃PO₄/CuO composites utilizing the synergistic effect of photocatalysis and Fenton-like catalysis to dispose organic pollutants,” Advanced Powder Technology, vol. 28, no. 11, pp. 2797–2804, 2017.
View at: Publisher Site | Google Scholar
S. Kumar, T. Surendar, A. Baruah, and V. Shanker, “Synthesis of a novel and stable g-C₃N₄–Ag₃PO₄ hybrid nanocomposite photocatalyst and study of the photocatalytic activity under visible light irradiation,” Journal of Materials Chemistry A, vol. 1, no. 17, p. 5333, 2013.
View at: Publisher Site | Google Scholar
L. Cai, Q. Long, and C. Yin, “Synthesis and characterization of high photocatalytic activity and stable Ag₃PO₄/TiO₂ fibers for photocatalytic degradation of black liquor,” Applied Surface Science, vol. 319, pp. 60–67, 2014.
View at: Publisher Site | Google Scholar
H. Yu, Z. Jiao, H. Hu, G. Lu, J. Ye, and Y. Bi, “Fabrication of Ag₃PO₄–PAN composite nanofibers for photocatalytic applications,” CrystEngComm, vol. 15, no. 24, p. 4802, 2013.
View at: Publisher Site | Google Scholar
M. Al Kausor and D. Chakrabortty, “Facile fabrication of N-TiO₂/Ag₃PO₄@GO nanocomposite toward photodegradation of organic dye under visible light,” Inorganic Chemistry Communications, vol. 116, article 107907, 2020.
View at: Publisher Site | Google Scholar
X. C. Song, Y. L. Qi, Y. F. Zheng, J. N. Liu, and H. Y. Yin, “Construction of magnetic Fe₍₃₎O₍₄₎@C@Ag₍₃₎PO₍₄₎ nanocomposites with excellent visible photocatalytic performance,” Journal of Nanoscience and Nanotechnology, vol. 17, no. 2, pp. 1407–1412, 2017.
View at: Publisher Site | Google Scholar
J. Li, Z. Liu, and Z. Zhu, “Enhanced photocatalytic activity in ZnFe₂O₄-ZnO- Ag₃PO₄ hollow nanospheres through the cascadal electron transfer with magnetical separation,” Journal of Alloys and Compounds, vol. 636, pp. 229–233, 2015.
View at: Publisher Site | Google Scholar
S. Mosleh, M. R. Rahimi, M. Ghaedi, K. Dashtian, S. Hajati, and S. Wang, “Ag₃PO₄/AgBr/Ag-HKUST-1-MOF composites as novel blue LED light active photocatalyst for enhanced degradation of ternary mixture of dyes in a rotating packed bed reactor,” Chemical Engineering and Processing: Process Intensification, vol. 114, pp. 24–38, 2017.
View at: Publisher Site | Google Scholar
N. Güy, K. Atacan, E. Karaca, and M. Özacar, “Role of Ag₃PO₄ and Fe₃O₄ on the photocatalytic performance of magnetic Ag₃PO₄/ZnO/Fe₃O₄ nanocomposite under visible light irradiation,” Solar Energy, vol. 166, pp. 308–316, 2018.
View at: Publisher Site | Google Scholar

Copyright

Copyright © 2022 Wegene Lelisa Beyecha et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

398

Downloads

355

Citations

Journal of Nanomaterials

Study on Challenges and Solutions for Enhancing Photocatalytic Activities of Ag3PO4 Nanoparticles for Degradation of Organic Dyes from Wastewater

Abstract

1. Introduction

1.1. Structure of Ag3PO4 for Photocatalysis Activity

1.2. Factors Affecting the Photocatalysis Activity of Ag3PO4

2. Common Challenges to Enhancing Photocatalytic Activities of Ag3PO4 Nanoparticles

3. Methods for Enhancing Photocatalysis Activity of Ag3PO4

3.1. Loading Noble Metal on the Surface of Ag3PO4

3.2. Forming Binary Ag3PO4 Composite with Semiconductor and Supported Material

3.3. Ag3PO4-Based Ternary Nanocomposite for Degrading Dyes from Wastewater

3.3.1. Photocatalysis Mechanisms in a Semiconductor to Decontaminate Organic Dyes

3.3.2. Future Perspective and the Opinion of the Reviewer

4. Conclusion

Data Availability

Conflicts of Interest

Acknowledgments

References

Copyright

Study on Challenges and Solutions for Enhancing Photocatalytic Activities of Ag₃PO₄ Nanoparticles for Degradation of Organic Dyes from Wastewater

1.1. Structure of Ag₃PO₄ for Photocatalysis Activity

1.2. Factors Affecting the Photocatalysis Activity of Ag₃PO₄

2. Common Challenges to Enhancing Photocatalytic Activities of Ag₃PO₄ Nanoparticles

3. Methods for Enhancing Photocatalysis Activity of Ag₃PO₄

3.1. Loading Noble Metal on the Surface of Ag₃PO₄

3.2. Forming Binary Ag₃PO₄ Composite with Semiconductor and Supported Material

3.3. Ag₃PO₄-Based Ternary Nanocomposite for Degrading Dyes from Wastewater