Use of Agro or Clay Based Polymer Nano-composites for Wastewater TreatmentView this Special Issue
Adsorption Characteristics of Chitosan-Modified Bamboo Biochar in Cd(II) Contaminated Water
The purpose of this study was to fabricate a low-cost and eco-friendly adsorbent using bamboo biochar (BB), a kind of charcoal composed of high Brunauer–Emmett–Teller surface area and variety of functional groups, and chitosan as substrates for remediation of Cd(II) in Cd(II) contaminated water and characterized the functional group characteristics, surface morphology, and Cd(II) adsorption effect using the Fourier transform infrared (FT-IR), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometer (EDS). Results showed that chitosan-modified bamboo biochar (CBB) provided more active adsorption sites (such as –NH2, –COOH, –OH, and C=O) on the surface to enhance the Cd(II) removal efficiency in Cd(II) contaminated wastewater. Meanwhile, the optimal pH, contact time, and dose of CBB on the Cd(II) removal efficiency are 7, 120 min, and 600 mg, respectively. In addition, the adsorption isotherm results revealed that the possible adsorption mechanisms might include surface adsorption, electrostatic adsorption, and ion exchanges. Furthermore, the maximum adsorption capacity (Qm) values predicted from the Langmuir model were 37.74 and 93.46 mg/g for BB and CBB, respectively, also indicating a potential application of CBB in practical wastewater. Desorption and regeneration of CBB were attained simultaneously and the results showed that even after five cycles of adsorption-elution, the adsorption and desorption of CBB exhibited a slight decline and still reached at 71.70% and 65.92%. Results from this study would provide a reference to functionalized CBB for Cd(II) adsorption in contaminated water.
Water pollution is one of the most severe problems on our planet. It is a novel challenge to manage water resources sustainably under climate change and population growth in the 21st century [1, 2]. Because of the high toxicity and persistence of cadmium (Cd(II)) in natural water and farmland, it has become an increasing concern over the past decades . In Japan, the main cause of the itai-itai disease was Cd(II) accumulation in the aquatic environment . Meanwhile, according to the World Health Organization (WHO), as one of the most toxic heavy metals, Cd(II) could lead to Cd(II) accumulation to cause harmful effects on the human body and causes carcinogenicity and liver damage . Hence, Cd(II) must be removed from the contaminated water and soil before they were disposed to the environment [5, 6]. During the past decades, many techniques, including ion exchange , membrane filtration , flocculation/coagulation , chemical precipitation , photocatalysis , phytoremediation , and adsorption , are performed to remove heavy metals from the contaminated water and soil. Especially, various physical and chemical techniques have been employed to lower the Cd(II) concentration to meet environmental standards, including chemical precipitation, ultrafiltration, membrane separation, electrochemical deposition, and adsorption . However, these techniques have great limitations for heavy metals removal due to their higher cost of energy and sludge production.
Biochar is produced from sustainably sourced biomass and is used for nonoxidative applications in agriculture [14, 15]. If biochar is used as a fuel to burn and the carbon is oxidized into CO2, hence it is actually classified as charcoal. Activated carbon is produced from any carbon source, such as fossil, waste, and renewable, and engineered to be used as sorbents to remove contaminants from both gases and liquids [16, 17]. Thus, it is defined as a material for contaminant sorption without exigencies in regard to the sustainability of its production nor to the fate of the carbon after its use. The bio-based adsorption is a promising method for heavy metals removal because it has good potential application prospects with an abundance of functional groups. Recently, the recycling of agricultural wastes as renewable adsorbents has received more and more attention. As an eco-friendly material, biochar has been widely used to remediate heavy metals and organic pollutants in soil and water contaminants [18–20]. Bamboo biochar (BB), a kind of charcoal composed of high Brunauer–Emmett–Teller (BET) surface area and a variety of functional groups (e.g., –NH2, –COOH, and –OH) that have gained more and more attention, is an eco-friendly, readily available, low-cost, and renewable biochar [18–20]. However, the BB adsorption performance for heavy metal removal is not so good since the surface functional groups are still insufficient. Therefore, to enhance the heavy metals removal performance of BB, in recent years, many attempts, for example, citric-acid modification, amino modification, polyethylenimine modification, and some other methods, have been performed to surface modification with more functional groups [21–24]. Chitosan, an abundant natural polysaccharide in the world, is a plentiful, inexpensive, and nontoxic product of the shellfish processing industry. In recent years, chitosan has been used as alternative sorbents in many industrial and environmental applications because their amine functional groups have a strong bonding ability to various heavy metals [25–28].
Herein, the objectives of this research were to (1) fabricate chitosan-modified bamboo biochar (CBB); (2) characterize the surface morphology, element abundance, and functional groups of CBB; (3) determine the Cd(II) adsorption effect of CBB in contaminated water; and (4) speculate the possible adsorption mechanisms of CBB in Cd(II) contaminated water.
2. Materials and Methods
The offcuts of bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. Pubescens), collected from the bamboo forest (N26°29′49″ and E106°44′10″) in the Guizhou Academy of Forestry, Guizhou Province, China. The chemicals were purchased from Aladdin-reagent Co., Ltd. (Shanghai, China).
2.2. Preparation of BB and CBB
The BB and CBB samples were prepared by following the procedures reported previously with some modifications [29, 30]. The offcuts of bamboo were washed with deionized water for three times to remove the dirt contained in the samples. The washed samples were air-dried, chopped into a particle size below 1.0 × 1.0 × 1.0 cm, and then oven-dried at 100 ± 5°C for 8 h before use. After that, the bamboo particles were pyrolyzed at 900°C for 4 h under N2 flow (100 mL/min) using a vacuum annealing furnace. After pyrolysis, the samples were ground via a ball grinder and passed through a standard 200 mesh sieve to obtain a particle size of about 75.0 μm. The samples were rinsed several times with deionized water and then oven-dried at 80°C for 24 h to obtain BB products for further use. After that, 0.4 g of chitosan mixed with 2.0 g BB were added into 30 mL of water. The mixtures were stirred well with sonication for 2 d at 30°C and 75% relative humidity (RH) and then separated by vacuum filtration and dried at 100 ± 5°C to give rise to the CBB.
2.3. Characterization of BB and CBB
The particle size distribution and specific surface area of BB and CBB were measured using a laser Bettersize 2600 particle analyzer (Bettersize Instruments Ltd., Dandong, China). The Fourier transform infrared (FT-IR) spectra of BB and CBB were obtained using a Thermo Nicolet 380 FT-IR spectrometer (Waltham, MA, USA). The surface morphology and elements of BB and CBB were scanned using a Quanta 250 Scanning Electron Microscope (SEM; FEI, Oregon, USA) equipped with a Bruker Quantax X-Flash 5030 energy dispersive X-ray spectrometer (EDS; Bruker, Berlin, Germany). The zeta potential values of BB and CBB were measured by a zeta potential analyzer (Malvern Instruments Ltd., Malvern, UK).
2.4. Batch-Adsorption Experiments
Batch-adsorption experiments were performed to evaluate the maximum Cd(II) adsorption efficiency of BB and CBB in 30 mL Cd(II) contaminated water with a concentration of 10 μg/mL. Briefly, different BB or CBB amounts (100, 200, 400, 600, 800, and 1000 mg) with pH 7 and contact time of 2 h, different contact times (5, 10, 30, 60, 120, 180, and 240 min) with pH 7 and BB or CBB amount of 600 mg, and initial pH (3, 4, 5, 6, 7, and 8) with a contact time of 2 h and BB or CBB amount of 600 mg on the Cd(II) adsorption efficiency in Cd(II) contaminated water were studied systemically. Briefly, the mixtures were shaken in a rotary shaker at 20°C and 120 rpm. After adsorption, the suspension was filtered with a 0.2 μm syringe filter, the Cd(II) concentration in the filtrate was determined by an iCE 3500 flame atomic absorption spectrometer (FAAS; Thermo Fisher, MA, USA) and an inductively coupled plasma mass spectrometry (ICP-MS; Thermo Scientific, MA, USA). For experimental accuracy, each trial was repeated three times.
The adsorption rate R (%) and adsorption amount Q (mg/g) of Cd(II) in Cd(II) contaminated water by BB or CBB were calculated using equations (1) and (2), where C0 (mg/L) and Ce (mg/L) represent the Cd(II) concentrations at the initial and adsorption equilibrium state, respectively, V (mL) represents the volume of the aqueous solution, and m (g) is the amount of BB or CBB.
2.5. Model for Equilibrium Study of Adsorption
The adsorption kinetics of Cd(II) was studied in Cd(II) contaminated water using the Langmuir and Freundlich isotherm models (3) and (4), where Ce (mg/L) is the equilibrium concentration, Qm (mg/g) denotes the maximum adsorption capacity, Qe (mg/g) represents the Cd(II) adsorbed amount at the equilibrium concentration, KL (mg/g) and KF (mg/g) are Langmuir and Freundlich isotherm constants, respectively, and 1/n relates to the adsorption capacity [31–34].
2.6. Desorption and Regeneration
To investigate the possibility of repeated use of the adsorbent CBB, in this study, the generation experiment was also conducted through five consecutive adsorption-desorption processes with the essential pH, contact time, and dose. Meanwhile, for the desorption experiment after Cd(II) adsorption, the CBB was transferred to a flask containing 40 mL of 0.2 M HCl desorbing agent. The mixture was shaken at 200 rpm using a rotary shaker for 3 h. After elution, the CBB was rinsed three times with deionized water to remove any traces of acid and suspended again in Cd(II) solution for the next adsorption cycle. The adsorption-desorption cycle was repeated five times using the same CBB. The desorption rates of CBB were evaluated as
2.7. Statistical Analysis
Statistical analysis was conducted by ANOVA with software SPSS 17.0 (SPSS Inc, Chicago, USA).
3. Results and Discussion
3.1. Preparation of BB and CBB
This study successfully fabricated a new kind of CBB using BB and chitosan as substrates for Cd(II) remediation in Cd(II) contaminated water. Some previous studies reported by Zhou et al.  and Zhang et al.  had also explored the use of chitosan to modify the BB surface to fabricate chitosan-modified biochars (CMB) and chitosan-modified magnetic biochar (CMMB) to enhance their affinity to heavy metals (Cr(IV), Pb(II), Cu(II), and Cd(II)) in water. It is interesting to note that the preparation technology to fabricate CBB reported in our present study is relatively simple and environmentally friendly without using NaOH, Fe2(SO4)3, and FeSO4·7H2O. Therefore, as far as we know, it is the first report to fabricate CBB using the above method reported in our present study.
3.2. Characterization of BB and CBB
As shown in Table 1, after the modification, CBB has no significant impact on the specific surface area and particle size distribution of BB. However, contrary to our findings, many biochar with organic matter have been shown to register very low surface areas .
Figures 1(a)–1(c) show that the BB surface exhibits notable smoothness and has a rich pore structure and numerous small particles, which may be formed after the degradation of some bamboo tissue during high-temperature pyrolysis, whereas Figures 1(d)–1(f) show that the CBB is slightly rather rough due to the irregular stacking of the bamboo charcoal particles. Meanwhile, EDS showed that the abundances of C, K, N, and O elements, which were the essential components of active functional groups, such as –NH2, –COOH, C=O, and –OH were found to be uniformly distributed along the surface of BB and CBB. In comparison, the abundances of C, K, N, and O were more densely distributed at CBB than BB, suggesting that CBB has abundant active ligand sites and has a positive contribution to the Cd(II) adsorption.
3.3. Zeta Analysis
The effect of pH on the zeta potential charge of BB and CBB surface is determined. As shown in Figure 2(a), the zeta potentials of BB and CBB decreased with the increase of the pH value, probably because of the deposition of more OH− on the adsorbent surface . Zeta potentials of BB were in the range of +18.90 to –22.10 mV as the initial pH of the suspensions increased from 3 to 8, whereas the zeta potentials of CBB increased (+35.80 to –5.26 mV) in the designed pH range from 3 to 8. The point of zero charge pH (pHpzc) of BB is 5.2, whereas the pHpzc of CBB increased to 7.6 after being modified by chitosan, suggesting that chitosan loaded on the BB surface increased the positive charge. Meanwhile, Figure 2(b) shows that, after Cd(II) adsorption, the zeta potentials of BB and CBB had an apparent increase at the pH of 7, illustrating that amino functionalization of chitosan had been adsorbed on the surface of CBB and the adsorption mechanism of CBB was based on electrostatic attraction [37, 38].
3.4. Infrared Spectroscopy Study
The surface functional groups information of BB and CBB before and after Cd(II) adsorption are presented in Figure 3. Figure 3 shows that the broad FT-IR band at 3420 cm−1 was attributed to the stretching vibrations of –OH and –NH– groups . The bands at 2960 and 1750 cm−1 were associated with the stretching vibration of –CH– and C=O, respectively [40, 41]. The band at 1430 cm−1 was assigned to the in-of-plane bending vibration for –COO– and –OH of –COOH . The band at 1160 cm−1 was ascribed to the stretching vibration of C–O of various groups [43, 44]. The band at 1070 cm−1 indicated the occurrence of the C–O group . Figure 3 also shows that, compared to BB, the contents of the main oxygen-containing functional groups, such as C–O, –COOH, C=O, and –OH, significantly increased during the preparation of CBB. Surfaces with abundant oxygen-containing functional groups could change the surface zeta potentials to strengthen the metal ions adsorbent in contaminated water .
3.5. Effect of pH, Contact Time, and Dose on the Cd(II) Adsorption
pH, an important parameter for affecting heavy metals adsorption, could affect the surface potential, counter ions concentration on the functional groups, and ionization degree of adsorbents [47–50]. To examine the effect of pH on the Cd(II) adsorption, the pH values were varied from 3 to 8. As shown in Figure 4(a), the adsorption rates of BB and CBB in Cd(II) contaminated water depend on the pH values and show similar trends. The adsorption rates of CBB increased from 66.78% to 90.66%, respectively, over the pH values range from 3 to 7, while the adsorption of Cd(II) tends to be stable when pH is greater than 7. Therefore, the optimal pH of CBB on the Cd(II) removal efficiency is 7. This is consistent with the results reported for heavy metal removal from industrial wastewater using chitosan-modified oil palm shell charcoal which was in the pH values range of 6.8–7.1 . Therefore, our results demonstrated that pH is one of the most essential parameters in the Cd(II) adsorption process and might change the function groups, mainly oxygen-containing groups, of CBB .
Contact time is one of the critical parameters for the contaminated water treatment system [52, 53]. To examine the effect of contact time on the Cd(II) removal efficiency, the contact time were varied from 5 to 240 min. As shown in Figure 4(b), the Cd(II) adsorption rates of CBB in Cd(II) contaminated water are higher than those of BB and increase with an increase in contact time before adsorption equilibrium is reached. It can be seen that the adsorption rates of CBB increase from 81.54% to 90.24% when the contact time increase from 5 to 120 min. Therefore, the optimum contact time for CBB is found to be 120 min, compared to that of BB which is 180 min. Hence, CBB requires a shorter contact time to reach adsorption equilibrium, demonstrating that the greater availability of various functional groups on the surface of chitosan could significantly improve the binding capacity and the adsorption of Cd(II) from wastewater [54–56].
The effect of different doses of BB and CBB on the Cd(II) adsorption was studied by varying the amount of adsorbents from 100 to 1000 mg, while keeping the pH value and contact time constant. Figure 4(c) shows that the Cd(II) removal efficiency of the BB and CBB adsorbents generally improves with the increasing adsorbent dose. This is expected that the higher dose of adsorbents added in Cd(II) contaminated water, the greater removal availability of adsorbents for Cd(II) removal, and then shows no further increase in Cd(II) adsorption after a certain amount of BB and CBB adsorbents were added [57, 58]. Meanwhile, the results, as shown in Figure 4(c), also indicate that the Cd(II) adsorption rates of CBB in Cd(II) contaminated water are higher than those of BB as well as increase with an increase in dose before equilibrium is reached. It can be seen that the adsorption rates of CBB increased from 73.33% to 90.66% when the doses of CBB were increased from 100 to 600 mg. Therefore, the optimum dose for CBB adsorbents is 600 mg, compared to that of BB which is 800 mg.
3.6. Adsorption Isotherms
To further investigate the adsorption mechanism of BB and CBB, the adsorption equilibrium isotherms of Cd(II) in Cd(II) wastewater were determined at 20°C with optimal conditions. Figure 5(a) shows the effect of contact time on the theoretical Cd(II) adsorption capacity by BB and CBB, and the adsorption curves of BB and CBB increased steeply within the first 180 min, indicating that the abundant adsorption sites on the BB and CBB surface were rapidly occupied by Cd(II) via surface absorption. Figure 5(b) shows the effect of Ce on the Cd(II) adsorption capacity by BB and CBB. When Ce < 45 mg/L, the Cd(II) adsorption capacity of the BB and CBB adsorbents was found to increase remarkably, which could be ascribed to the sufficient active sites on the BB and CBB surface. Meanwhile, as the Ce values continue to increase, the available active adsorption sites on the surface of the BB and CBB adsorbents tend to saturate, therefore resulting in a dynamic adsorption equilibrium for the Cd(II) adsorption capacity. Similar results were reported by Yan et al. . The Langmuir and Freundlich fitting curves of BB and CBB are plotted in Figures 5(c) and 5(d) and the related parameters are presented in Table 2. Figures 5(c) and 5(d) as well as Table 2 show that the Langmuir and Freundlich models exhibit the best fit for BB and CBB with both the highest correlation coefficients exceeding 0.95, indicating that the BB and CBB surface are homogeneous . Generally, 1/n represents the heterogeneity factor of the site energy on the functional groups, and the smaller 1/n is, the better the adsorption capacity is, such as 0 < 1/n < 1 indicates favorable adsorption [60, 61]. This study shows that the 1/n values of BB and CBB are 0.24 and 0.21, respectively, indicating a favorable Cd(II) adsorption by the two adsorbents. The KF obtained from the Freundlich model as well as KL obtained from the Langmuir model could be the critical indicators of heavy metals adsorption . Table 2 shows that the KF and KL values followed the order: BB > CBB, suggesting that CBB had an adsorption affinity toward Cd(II). Furthermore, the maximum adsorption capacity (Qm) values predicted from the Langmuir model were 37.74 and 93.46 mg/g for BB and CBB, respectively. In recent years, many modified biochars were also prepared [61–65] and the comparison of the Qm values of Cd(II) was listed in Table 3. Table 3 shows that the Qm value of Cd(II) is higher than most of the reported modified biochars, indicating a potential application of CBB in practical wastewater.
3.7. Desorption and Reusability
The recyclability of adsorbent is one of the important performance indexes to evaluate the applicability of adsorbent in treating actual wastewater . The adsorption and desorption rates of Cd(II) in five adsorption-desorption cycles were shown in Figure 6. It was found that after five cycles, the adsorption and desorption of CBB exhibited a slight decline and still reached at 71.70% and 65.92%, respectively. The good reproducibility indicated that CBB could be used as a desirable, economic, and recyclable adsorbent in practical wastewater.
3.8. Possible Adsorption Mechanism
Based on the above analysis and isotherm results, a possible mechanism for the adsorption of Cd(II) by CBB has been proposed and depicted in Figure 7. As shown in Figure 7, we speculate that the possible adsorption mechanisms include surface adsorption, electrostatic adsorption, and ion exchanges. More specifically, the surface of CBB has abundant pores and active functional groups (–NH2, –COOH, –OH, and C=O), which could significantly improve the surface adsorption capacity. Meanwhile, abundant –OH and –COOH active functional groups on the surface of CBB could change the surface zeta potentials by loss of H+ to form charged functional groups, thus strengthening the electrostatic adsorption of the adsorbent in Cd(II) contaminated water. In addition, after carbonization at high temperature, the abundant K of CBB are transformed into free K+, which continuously exchange with Cd(II) in an aqueous solution, thus promoting the process of Cd(II) ion exchange.
In summary, a new eco-friendly and low-cost adsorbent for Cd(II) was prepared by the modification of BB with chitosan via a simple method. Results showed that the modification could significantly improve the surface properties and adsorption performance for Cd(II) adsorption. As well, the adsorption isotherm results show that the possible adsorption mechanisms include surface adsorption, electrostatic adsorption, and ion exchanges. Thus, the CBB can be considered as a feasible, promising, and high value-added approach for Cd(II) contaminated water recycling.
All data included in this study are available upon request by contacting the corresponding author.
Conflicts of Interest
The authors declare that there are no conflicts of interest.
This research was funded by the National Key Technology R&D Program of Guizhou Province, grant numbers 130, 334, and 186; the Rural Industrial Revolution Characteristic Forestry Industry Program of Guizhou Province, grant number 14; and the Youth Fund of Guizhou Forestry Bureau, grant number J07.
I. Anastopoulos, I. Pashalidis, A. Hosseini-Bandegharaei et al., “Agricultural biomass/waste as adsorbents for toxic metal decontamination of aqueous solutions,” Journal of Molecular Liquids, vol. 295, Article ID 111684, 2019.View at: Publisher Site | Google Scholar
L. P. Lingamdinne, J.-K. Yang, Y.-Y. Chang, J. R. Koduru, and J. R. Koduru, “Low-cost magnetized Lonicera japonica flower biomass for the sorption removal of heavy metals,” Hydrometallurgy, vol. 165, pp. 81–89, 2016.View at: Publisher Site | Google Scholar
Q. Zhou, B. Liao, L. Lin, W. Qiu, and Z. Song, “Adsorption of Cu(II) and Cd(II) from aqueous solutions by ferromanganese binary oxide-biochar composites,” The Science of the Total Environment, vol. 615, pp. 115–122, 2018.View at: Publisher Site | Google Scholar
P. Chowdhury, S. Athapaththu, A. Elkamel, and A. K. Ray, “Visible-solar-light-driven photo-reduction and removal of cadmium ion with Eosin Y-sensitized TiO2 in aqueous solution of triethanolamine,” Separation and Purification Technology, vol. 174, pp. 109–115, 2017.View at: Publisher Site | Google Scholar
K. Rao, M. Mohapatra, S. Anand, and P. Venkateswarlu, “Review on cadmium removal from aqueous solutions,” International Journal of Engineering Science and Technology, vol. 2, pp. 81–103, 2010.View at: Google Scholar
M. R. H. M. Haris, N. A. Wahab, C. W. Reng, B. Azahari, and K. Sathasivam, “The sorption of cadmium (II) ions on mercerized rice husk and activated carbon,” Turkish Journal of Chemistry, vol. 35, pp. 939–950, 2011.View at: Google Scholar
M. Naushad, A. Mittal, M. Rathore, and V. Gupta, “Ion-exchange kinetic studies for Cd(II), Co(II), Cu(II), and Pb(II) metal ions over a composite cation exchanger,” Desalination and Water Treatment, vol. 54, no. 10, pp. 2883–2890, 2015.View at: Publisher Site | Google Scholar
Z. You, C. Zhuang, Y. Sun, S. Zhang, and H. Zheng, “Efficient removal of TiO2 nanoparticles by enhanced flocculation-coagulation,” Industrial & Engineering Chemistry Research, vol. 58, no. 31, pp. 14528–14537, 2019.View at: Publisher Site | Google Scholar
A. A. H. Faisal, S. F. A. Al-Wakel, H. A. Assi, L. A. Naji, and M. Naushad, “Waterworks sludge-filter sand permeable reactive barrier for removal of toxic lead ions from contaminated groundwater,” Journal of Water Process Engineering, vol. 33, Article ID 101112, 2020.View at: Publisher Site | Google Scholar
G. Sharma and M. Naushad, “Adsorptive removal of noxious cadmium ions from aqueous medium using activated carbon/zirconium oxide composite: isotherm and kinetic modelling,” Journal of Molecular Liquids, vol. 310, Article ID 113025, 2020.View at: Publisher Site | Google Scholar
S. Muthusaravanan, N. Sivarajasekar, J. S. Vivek et al., “Phytoremediation of heavy metals: mechanisms, methods and enhancements,” Environmental Chemistry Letters, vol. 16, no. 4, pp. 1339–1359, 2018.View at: Publisher Site | Google Scholar
M. Naushad, Z. A. Alothman, M. R. Awual, M. M. Alam, and G. E. Eldesoky, “Adsorption kinetics, isotherms, and thermodynamic studies for the adsorption of Pb2+ and Hg2+ metal ions from aqueous medium using Ti(IV) iodovanadate cation exchanger,” Ionics, vol. 21, no. 8, pp. 2237–2245, 2015.View at: Publisher Site | Google Scholar
S. Zhang, M. Cui, J. Chen et al., “Modification of synthetic zeolite X by thiourea and its adsorption for Cd (II),” Materials Letters, vol. 236, pp. 233–235, 2019.View at: Publisher Site | Google Scholar
J. Lehmann and S. Joseph, Biochar for Environmental Management: An Introduction in Biochar for Environmental Management: Science, Technology and Implementation, Routledge, Oxford, UK, 2015.
European Biochar Certificate (EBC), European Biochar Foundation—European Biochar Certificate—Guidelines for a Sustainable Production of Biochar; Version 6.3E of August 14, 2017, European Biochar Certificate (EBC), Arbaz, Switzerland, 2017.
H. Marsh and F. R. Reinoso, Activated Carbon, Elsevier, Amsterdam, Netherlands, 2006.
M. Smisek and S. Cerny, “Activated carbon,” in Topics in Organic and General Chemistry, Elsevier Co., New York, NY, USA, 1970.View at: Google Scholar
J. B. Zhou, Study on the Mechanism of Action and Environmental Application of Bamboo Charcoal, Nanjing Forestry University, PHD thesis, Nanjing, China, 2005.
J.-H. Park, J.-S. Cho, Y. S. Ok et al., “Comparison of single and competitive metal adsorption by pepper stem biochar,” Archives of Agronomy and Soil Science, vol. 62, no. 5, pp. 617–632, 2016.View at: Publisher Site | Google Scholar
K. Lu, X. Yang, G. Gielen et al., “Effect of bamboo and rice straw biochars on the mobility and redistribution of heavy metals (Cd, Cu, Pb and Zn) in contaminated soil,” Journal of Environmental Management, vol. 186, pp. 285–292, 2017.View at: Publisher Site | Google Scholar
J. Rivera-Utrilla, M. Sánchez-Polo, V. Gómez-Serrano, P. M. Álvarez, M. C. M. Alvim-Ferraz, and J. M. Dias, “Activated carbon modifications to enhance its water treatment applications. An overview,” Journal of Hazardous Materials, vol. 187, no. 1–3, pp. 1–23, 2011.View at: Publisher Site | Google Scholar
J. P. Chen, S. Wu, and K.-H. Chong, “Surface modification of a granular activated carbon by citric acid for enhancement of copper adsorption,” Carbon, vol. 41, no. 10, pp. 1979–1986, 2003.View at: Publisher Site | Google Scholar
G.-X. Yang and H. Jiang, “Amino modification of biochar for enhanced adsorption of copper ions from synthetic wastewater,” Water Research, vol. 48, pp. 396–405, 2014.View at: Publisher Site | Google Scholar
Y. Ma, W.-J. Liu, N. Zhang, Y.-S. Li, H. Jiang, and G.-P. Sheng, “Polyethylenimine modified biochar adsorbent for hexavalent chromium removal from the aqueous solution,” Bioresource Technology, vol. 169, pp. 403–408, 2014.View at: Publisher Site | Google Scholar
R. N. Tharanathan and F. S. Kittur, “Chitin - the undisputed biomolecule of great potential,” Critical Reviews in Food Science and Nutrition, vol. 43, no. 1, pp. 61–87, 2003.View at: Publisher Site | Google Scholar
C. Gerente, V. K. C. Lee, P. L. Cloirec, and G. McKay, “Application of chitosan for the removal of metals from wastewaters by adsorption-mechanisms and models review,” Critical Reviews in Environmental Science and Technology, vol. 37, no. 1, pp. 41–127, 2007.View at: Publisher Site | Google Scholar
L. Pontoni and M. Fabbricino, “Use of chitosan and chitosan-derivatives to remove arsenic from aqueous solutions—a mini review,” Carbohydrate Research, vol. 356, pp. 86–92, 2012.View at: Publisher Site | Google Scholar
A. Bhatnagar and M. Sillanpää, “Applications of chitin- and chitosan-derivatives for the detoxification of water and wastewater—a short review,” Advances in Colloid and Interface Science, vol. 152, no. 1-2, pp. 26–38, 2009.View at: Publisher Site | Google Scholar
Y. Zhou, B. Gao, A. R. Zimmerman, J. Fang, Y. Sun, and X. Cao, “Sorption of heavy metals on chitosan-modified biochars and its biological effects,” Chemical Engineering Journal, vol. 231, pp. 512–518, 2013.View at: Publisher Site | Google Scholar
H. Zhang, R. Xiao, R. Li, A. Ali, A. Chen, and Z. Zhang, “Enhanced aqueous Cr(VI) removal using chitosan-modified magnetic biochars derived from bamboo residues,” Chemosphere, vol. 261, p. 127694, 2020.View at: Publisher Site | Google Scholar
Y. Rashtbari, S. Hazrati, A. Azari, S. Afshin, M. Fazlzadeh, and M. Vosoughi, “A novel, eco-friendly and green synthesis of PPAC-ZnO and PPAC-nZVI nanocomposite using pomegranate peel: cephalexin adsorption experiments, mechanisms, isotherms and kinetics,” Advanced Powder Technology, vol. 31, no. 4, pp. 1612–1623, 2020.View at: Publisher Site | Google Scholar
A. Hamzezadeh, Y. Rashtbari, S. Afshin, M. Morovati, and M. Vosoughi, “Application of low-cost material for adsorption of dye from aqueous solution,” International Journal of Environmental Analytical Chemistry, vol. 102, no. 1, 2020.View at: Publisher Site | Google Scholar
S. Afshin, Y. Rashtbari, M. Shirmardi, M. Vosoughi, and A. Hamzehzadeh, “Adsorption of basic Violet 16 dye from aqueous solution onto mucilaginous seeds of Salvia sclarea: kinetics and isotherms studies,” Desalination and Water Treatment, vol. 161, pp. 365–375, 2019.View at: Publisher Site | Google Scholar
S. Afshin, Y. Rashtbari, M. Vosough et al., “Application of Box-Behnken design for optimizing parameters of hexavalent chromium removal from aqueous solutions using Fe3O4 loaded on activated carbon prepared from alga: kinetics and equilibrium study,” Journal of Water Process Engineering, vol. 42, Article ID 102113, 2021.View at: Publisher Site | Google Scholar
G. N. Kasozi, A. R. Zimmerman, P. Nkedi-Kizza, and B. Gao, “Catechol and humic acid sorption onto a range of laboratory-produced black carbons (biochars),” Environmental Science and Technology, vol. 44, no. 16, pp. 6189–6195, 2010.View at: Publisher Site | Google Scholar
C. Lu and F. Su, “Adsorption of natural organic matter by carbon nanotubes,” Separation and Purification Technology, vol. 58, no. 1, pp. 113–121, 2007.View at: Publisher Site | Google Scholar
J. Pan, Y. Li, K. Chen, Y. Zhang, and H. Zhang, “Enhanced physical and antimicrobial properties of alginate/chitosan composite aerogels based on electrostatic interactions and noncovalent crosslinking,” Carbohydrate Polymers, vol. 266, Article ID 118102, 2021.View at: Publisher Site | Google Scholar
I. S. Lopes, M. Michelon, L. G. R. Duarte, P. Prediger, R. L. Cunha, and C. S. F. Picone, “Effect of chitosan structure modification and complexation to whey protein isolate on oil/water interface stabilization,” Chemical Engineering Science, vol. 230, Article ID 116124, 2021.View at: Publisher Site | Google Scholar
S. Wu, M. Lu, and S. Wang, “Antiageing activities of water-soluble chitosan from Clanis bilineata larvae,” International Journal of Biological Macromolecules, vol. 102, pp. 376–379, 2017.View at: Publisher Site | Google Scholar
S. Ali, M. Rizwan, M. B. Shakoor, A. Jilani, and R. Anjum, “High sorption efficiency for As(III) and As(V) from aqueous solutions using novel almond shell biochar,” Chemosphere, vol. 243, Article ID 125330, 2020.View at: Publisher Site | Google Scholar
P. S. Saravana, T. C. Ho, S.-J. Chae et al., “Deep eutectic solvent-based extraction and fabrication of chitin films from crustacean waste,” Carbohydrate Polymers, vol. 195, pp. 622–630, 2018.View at: Publisher Site | Google Scholar
C. Vasile, G. G. Bumbu, R. Petronela Dumitriu, and G. Staikos, “Comparative study of the behavior of carboxymethyl cellulose-g-poly(N-isopropylacrylamide) copolymers and their equivalent physical blends,” European Polymer Journal, vol. 40, no. 6, pp. 1209–1215, 2004.View at: Publisher Site | Google Scholar
Y.-H. Lin and P.-H. Su, “Behavior of aluminum adsorption in different compost-derived humic acids,” Clean-Soil, Air, Water, vol. 38, no. 10, pp. 916–920, 2010.View at: Publisher Site | Google Scholar
M.-E. Lee, J. H. Park, and J. W. Chung, “Comparison of the lead and copper adsorption capacities of plant source materials and their biochars,” Journal of Environmental Management, vol. 236, pp. 118–124, 2019.View at: Publisher Site | Google Scholar
Y. Shigemasa, H. Matsuura, H. Sashiwa, and H. Saimoto, “Evaluation of different absorbance ratios from infrared spectroscopy for analyzing the degree of deacetylation in chitin,” International Journal of Biological Macromolecules, vol. 18, no. 3, pp. 237–242, 1996.View at: Publisher Site | Google Scholar
S. M. Nomanbhay and K. Palanisamy, “Removal of heavy metal from industrial wastewater using chitosan coated oil palm shell charcoal,” Electronic Journal of Biotechnology, vol. 8, pp. 43–53, 2005.View at: Publisher Site | Google Scholar
Y. Guo, R. Wang, P. Wang, L. Rao, and C. Wang, “Developing a novel layered boron nitride-carbon nitride composite with high efficiency and selectivity to remove protonated dyes from water,” ACS Sustainable Chemistry & Engineering, vol. 7, no. 6, pp. 5727–5741, 2019.View at: Publisher Site | Google Scholar
Y. Guo, R. Wang, C. Yan, P. Wang, L. Rao, and C. Wang, “Developing boron nitride-pyromellitic dianhydride composite for removal of aromatic pollutants from wastewater via adsorption and photodegradation,” Chemosphere, vol. 229, pp. 112–124, 2019.View at: Publisher Site | Google Scholar
P. Wang, C. Wu, Y. Guo, and C. Wang, “Experimental and theoretical studies on methylene blue and methyl orange sorption by wheat straw-derived biochar with a large surface area,” Physical Chemistry Chemical Physics, vol. 18, no. 43, pp. 30196–30203, 2016.View at: Publisher Site | Google Scholar
X. Tan, Y. Liu, G. Zeng et al., “Application of biochar for the removal of pollutants from aqueous solutions,” Chemosphere, vol. 125, pp. 70–85, 2015.View at: Publisher Site | Google Scholar
K. Kadirvelu, C. Karthika, N. Vennilamani, and S. Pattabhi, “Activated carbon from industrial solid waste as an adsorbent for the removal of Rhodamine-B from aqueous solution: kinetic and equilibrium studies,” Chemosphere, vol. 60, no. 8, pp. 1009–1017, 2005.View at: Publisher Site | Google Scholar
W. Li, L. Zhang, J. Peng, N. Li, S. Zhang, and S. Guo, “Tobacco stems as a low cost adsorbent for the removal of Pb(II) from wastewater: equilibrium and kinetic studies,” Industrial Crops and Products, vol. 28, no. 3, pp. 294–302, 2008.View at: Publisher Site | Google Scholar
N. T. Abdel-Ghani, M. Hefny, and G. A. F. El-Chaghaby, “Removal of lead from aqueous solution using low cost abundantly available adsorbents,” International journal of Environmental Science and Technology, vol. 4, no. 1, pp. 67–73, 2007.View at: Publisher Site | Google Scholar
S. Shahraki, H. S. Delarami, F. Khosravi, and R. Nejat, “Improving the adsorption potential of chitosan for heavy metal ions using aromatic ring-rich derivatives,” Journal of Colloid and Interface Science, vol. 576, pp. 79–89, 2020.View at: Publisher Site | Google Scholar
B. Li, J. Gong, J. Fang, Z. Zheng, and W. Fan, “Cysteine chemical modification for surface regulation of biochar and its application for polymetallic adsorption from aqueous solutions,” Environmental Science and Pollution Research, vol. 28, no. 1, pp. 1061–1071, 2021.View at: Publisher Site | Google Scholar
F. C. Christopher, S. Anbalagan, P. S. Kumar, S. R. Pannerselvam, and V. K. Vaidyanathan, “Surface adsorption of poisonous Pb(II) ions from water using chitosan functionalised magnetic nanoparticles,” IET Nanobiotechnology, vol. 11, no. 4, pp. 433–442, 2017.View at: Publisher Site | Google Scholar
Z. Wan, D. Chen, H. Pei et al., “Batch study for Pb2+ removal by polyvinyl alcohol-biochar macroporous hydrogel bead,” Environmental Technology, vol. 42, no. 4, pp. 648–658, 2021.View at: Publisher Site | Google Scholar
Y. Yan, L. Zhang, Y. Wang et al., “Clanis bilineata larvae skin-derived biochars for immobilization of lead: sorption isotherm and molecular mechanism,” The Science of the Total Environment, vol. 704, Article ID 135251, 2020.View at: Publisher Site | Google Scholar
Y. Yao, B. Gao, M. Inyang et al., “Removal of phosphate from aqueous solution by biochar derived from anaerobically digested sugar beet tailings,” Journal of Hazardous Materials, vol. 190, no. 1–3, pp. 501–507, 2011.View at: Publisher Site | Google Scholar
H. J. Cho, K. Baek, J.-K. Jeon, S. H. Park, D. J. Suh, and Y.-K. Park, “Removal characteristics of copper by marine macro-algae-derived chars,” Chemical Engineering Journal, vol. 217, pp. 205–211, 2013.View at: Publisher Site | Google Scholar
S. Zhang, H. Zhang, J. Cai, X. Zhang, J. Zhang, and J. Shao, “Evaluation and prediction of Cadmium removal from aqueous solution by phosphate-modified activated bamboo biochar,” Energy and Fuels, vol. 32, no. 4, pp. 4469–4477, 2018.View at: Publisher Site | Google Scholar
G. Yin, X. Song, L. Tao et al., “Novel Fe-Mn binary oxide-biochar as an adsorbent for removing Cd(II) from aqueous solutions,” Chemical Engineering Journal, vol. 389, Article ID 124465, 2020.View at: Publisher Site | Google Scholar
J. Xiao, R. Hu, and G. Chen, “Micro-nano-engineered nitrogenous bone biochar developed with a ball-milling technique for high-efficiency removal of aquatic Cd(II), Cu(II) and Pb(II),” Journal of Hazardous Materials, vol. 387, Article ID 121980, 2020.View at: Publisher Site | Google Scholar
W. Yu, J. Hu, Y. Yu et al., “Facile preparation of sulfonated biochar for highly efficient removal of toxic Pb(II) and Cd(II) from wastewater,” The Science of the Total Environment, vol. 750, Article ID 141545, 2021.View at: Publisher Site | Google Scholar
J. Xiang, Q. Lin, X. Yao, and G. Yin, “Removal of Cd from aqueous solution by chitosan coated MgO-biochar and its in-situ remediation of Cd-contaminated soil,” Environmental Research, vol. 195, Article ID 110650, 2021.View at: Publisher Site | Google Scholar
F. Zhang, B. Wang, P. Jie, J. Zhu, and F. Cheng, “Preparation of chitosan/lignosulfonate for effectively removing Pb(II) in water,” Polymer, vol. 228, Article ID 123878, 2021.View at: Publisher Site | Google Scholar