• Environmental Engineering Research
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• v.25 no.4
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• pp.488-497
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• 2020

The present study investigates the feasibility of nitrogenous heterocyclic compounds (NHCs) (Pyridine-Quinoline) degradation by catalytic wet peroxidation (CWPO) in the presence of nanoscale zerovalent iron supported on granular activated carbon (nFe⁰/GAC) using statistical optimization technique. Response surface methodology (RSM) in combination with Box-Behnken design (BBD) was used to optimize the process parameters of CWPO process such as initial pH, catalyst dose, hydrogen peroxide dose, initial concentration of pyridine (Py) and quinolone (Qn) were chosen as the main variables, and total organic carbon (TOC) removal and total Fe leaching were selected as the investigated response. The optimization of process parameters by desirability function showed the ~85% of TOC removal with process condition of initial solution pH 3.5, catalyst dose of 0.55 g/L, hydrogen peroxide concentration of 0.34 mmol, initial concentration of Py 200 mg/L and initial concentration of Qn 200 mg/L. Further, for TOC removal the analysis of variance results of the RSM revealed that all parameter i.e. initial pH, catalyst dose, hydrogen peroxide dose, initial concentration of Py and initial concentration of Qn were highly significant according to the p values (p < 0.05). The quadratic model was found to be the best fit for experimental data. The present study revealed that BBD was reliable and effective for the determination of the optimum conditions for CWPO of NHCs (Py-Qn).

• Environmental Engineering Research
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• v.25 no.2
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• pp.186-196
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• 2020

Pillared clays with Zr and Fe/Cu/Zr polycations have been prepared from natural clays found in large deposits of Kazakhstan and assessed as catalysts for the catalytic wet peroxide oxidation (CWPO), using 4-nitrophenol (4-NP) as model compound. The performance of the catalysts was followed by measuring the concentration of 4-NP, H₂O₂ and the total organic carbon (TOC), considering C_4-NP = 5 g L^-1, $C_{H_2O_2}$ = 17.8 g L^-1, C_cat = 2.5 g L^-1, initial pH = 3.0 and T = 50℃. At those selected conditions, the pillared clays showed higher activity than natural clays in the CWPO of 4-NP. The conversion of the model pollutant was complete when Fe/Cu/Zr-PILCs were used, with the TOC removal reaching 78.4% after 24 h with the best Fe/Cu/Zr-PILC. The H₂O₂, 4-NP and TOC time-evolution was well described by a kinetic model based on TOC lumps in three blocks, considering the initial TOC (corresponding to 4-NP), the production of oxidizable intermediates and the formation of refractory products.

• Clean Technology
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• v.24 no.4
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• pp.293-300
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• 2018

Sulfamethoxazole (SMX) is sulfaamide-based synthetic antibiotics, which are widely prescribed pharmaceutical compound to treat bacterial infections in both human and animals. Most of them are not completely decomposed as refractory substances. The environmental impact of pharmaceuticals as emerging contaminants has generated severe concerns. In this study, catalytic wet peroxide oxidation (CWPO) of SMX was carried out with $Cu/Al_2O_3$ catalyst and investigated the optimum reaction conditions of temperature, dosage of catalyst and concentration of $H_2O_2$ to completely decompose the SMX. It was observed that SMX was completely decomposed within 20 min using 0.79 mM $H_2O_2$ and 6 g $Cu/Al_2O_3$ catalyst at 1 atm and $40^{\circ}C$, but SMX was not fully mineralized and converted to intermediates as hydroylated-SMX, sulfanilic acid, 4-aminobenzenesulfinic acid and nitrobenzene. After that these are completely mineralized through organic acid. We proposed the decomposition reaction path ways of SMX by analyzing the behavior of these intermediates. To investigate the durability of heterogeneous catalyst, decomposition of SMX was observed by continuously recycling catalysts. When the heterogeneous catalyst of 10 wt% $Cu/Al_2O_3$ was continuously reused 5 times, decomposition of SMX was a little lowered, but the activity of catalyst was overall very stable.