Recent Developments in Homogeneous Advanced Oxidation Processes for Water and Wastewater Treatment

Table 2

Degradation of some model pollutants by ozone based AOPs under different experimental conditions.

Reference	AOPs applied	Pollutant(s)	Conclusions
[25]	O3, UV/H2O2, O3/H2O2, O3/AC	Diethyl phthalate (DEP) in ultrapure water, surface water, and wastewater	The O3/AC process was the most efficient for the removal of DEP in all three types of water. The O3/H2O2 and O3/AC processes are more efficient than ozonation alone.
[26]	O3, UV photolysis, O3/UV, H2O2/O3, O3/H2O2/UV	1,4-Dioxane	The O3/H2O2/UV process was most efficient for 1,4-dioxane removal at pH 10, with H2O2 : O3 ratio of 0.5.
[27]	O3, O3/H2O2, UV/H2O2, UV/O3 UV/H2O2/O3	Phenol	The UV/H2O2/O3 process at pH 7 with H2O2 = 10 mM was most ecoeffective with 100% of phenol removal within 30 min and 58.0% TOC removal after 1 h. UV/H2O2/O3 was the most effective process for phenol wastewater mineralization.
[28]	O3, O3/H2O2, UV/H2O2	Twenty-four micropollutants including endocrine disrupting compounds, pharmaceuticals, and personal care products	The general trend of ozone and hydroxyl radical reactivity with the selected micropollutants was explained. Suitable technology for the removal of these micropollutants was suggested based on the micropollutant reactivity with ozone and hydroxyl radical.
[29]	O3, UV photolysis, O3/UV, O3/catalyst, UV/catalyst, O3/UV/catalyst, H2O2/UV, H2O2/UV/catalyst	Pyruvic acid	The UV/H2O2 process with or without perovskite catalysts facilitates pyruvic acid removal fastest. The O3/UV/perovskite process was efficient for mineralization.
[30]	UV, UV/H2O2, UV/O3, UV/H2O2/O3,; UV/Fenton	p-Chlorophenol	Operating conditions such as initial pH, concentration of H2O2, and ferrous salt were optimized for each process. The UV/Fenton and UV/H2O2/O3 processes were found to be the most effective for the degradation and mineralization of p-CP.
[31]	O3, H2O2/O3, UV/Fe^2+/H2O2	Nitroaromatics such as; nitrotoluene, dinitrotoluene, and trinitrotoluene	Ozonation and/or Fenton’s reagent were found to be efficient for TNT degradation. The O3/H2O2 process at pH > 7 was most efficient for 2-MNT and 2.4-DNT removal.
[32]	O3/UV, H2O2/UV, O3/H2O2, O3/H2O2/UV	Haloacetic acids (HAAs), dichloroacetic acid (DCAA), and trichloroacetic acid; (TCAA)	The O3/UV process was the most efficient of the six degradation methods for DCAA and TCAA in water. Decomposition by AOPs was easier for DCAA than for TCAA.
[33]	O3, O3/UV, O3/H2O2, UV/H2O2, O3/UV/H2O2	O-Nitrotoluene	The optimum H2O2 dosage and solution pH were studied. Adding H2O2 to the ozonation process accelerated the oxidation of O-nitrotoluene by a factor of 8. The O3/UV and UV/H2O2 processes are 20 and 10 times more efficient than the ozonation process, respectively.
[34]	O3, UV-vis,; O3 + UV-vis, TiO2 + UV-vis, O3 + UV-vis + TiO2, and O3 + TiO2	Phenol,; 4-nitrophenol, and; 4-chlorophenol	AOP efficiencies are in the following order: adsorption < TiO2 + UV-vis < UV-vis < O3 + TiO2 ≈ O3 < O3 + UV-vis ≈ O3 + UV-vis + TiO2. The O3 + UV-vis and O3 + UV-vis + TiO2 methods are the most economically attractive.
[35]	O3, O3/H2O2, O3/activated carbon	Acid Blue 92 (AB92)	Ozone treatment was a very effective method for complete removal of colour but in COD removal it was not efficient. The removal of COD in ozonation, O3/H2O2, and O3/AC processes, 30%, 80% and 100%, respectively.
[36]	O3 or O3/H2O2, O3/powdered activated carbon (PAC)	Sodium Dodecylbenzenesulfonate(SDBS)	Comparison of the O3/PAC system with the O3 and O3/H2O2 processes showed that the O3/PAC system was more effective in the removal of SDBS.
[37]	O3, O3/UV, UV/H2O2	Dye house effluent	The AOP efficiency is dependent on the pH and dosage of H2O2. The UV/H2O2 process is 50 times more efficient than the O3/H2O2 process.
[38]	Ozonation, sonication, UV photolysis, O3/ultrasound, UV/ultrasound, O3/UV/ultrasound	Phenol	The efficiency of the various AOPs at two different pH was in the following order. At pH 2, US/UV/O3≫O3/UV > US/O3 > US/UV > O3 > US > UV.; At pH 10.0, US/UV/O3 > O3/UV > O3 > US/O3 > US/UV > UV > US. The maximum rate of phenol degradation was observed in the combined application of O3/UV/US at basic pH.
[39]	US; O3; O3/US; O3/UV; US/UV; O3/US/UV	Acid Orange 7	The UV/O3 process was more effective at all times than the US and/or O3 process. The O3/US/UV process was the most efficient for colour and aromatic removal and AO7 dye mineralization.