Low-Pressure Catalytic Wet Air Oxidation of Aniline Over Co3O4/CeO2

Performance of various catalysts on treatment of refractory pollutants in industrial wastewater by catalytic wet air oxidation: A review

The tremendous increase of industrialization and urbanization worldwide causes the depletion of natural resources such as water and air which urges the necessity to follow the environmental sustainability across the globe. This requires eco-friendly and economical technologies for depollution of wastewater and gases or zero emission approach. Therefore, in this context the treatment and reuse of wastewater is an environmental friendly approach due to shortage of fresh water. Catalytic wet air oxidation (CWAO) is a promising technology for the treatment of toxic and non-biodegradable organic pollutants in the wastewater generated from various industries. Various heterogeneous catalysts have been extensively used for treatment of various model pollutants such as phenols, carboxylic acids, nitrogenous compounds and different types of industrial effluents. The present review focuses on the literature published on the performances of various noble and non-noble metal catalysts for the treatment of various pollutants by CWAO. Reports on biodegradability enhancement of industrial wastewater containing toxic contaminants by CWAO are reviewed. Detailed discussion is made on catalyst deactivation and their mitigation study and also on the various factors which affects the CWAO reaction.

Sorption mechanism and predictive models for removal of cationic organic contaminants by cation exchange resins

Understanding the sorption mechanism of organic contaminants on cation exchange resins (CXRs) will enable application of these resins for the removal of cationic organic compounds from contaminated water. In this study, sorption of a diverse set of 12 organic cations and 8 neutral aromatic solutes on two polystyrene CXRs, MN500 and Amberlite 200, was examined. MN500 showed higher sorbed concentrations due to its microporous structure. The sorbed concentrations followed the same trend of aromatic cations > aliphatic cations > neutral solutes for both resins. Generally, solute-solvent interactions, nonpolar moiety of the solutes, and resin matrix can affect selectivity of the cations. Sorbed concentrations of the neutral compounds were significantly less than those of the cations, indicating a combined effect of electrostatic and nonelectrostatic interactions. By conducting multiple linear regression between Gibbs free energy of sorption and Abraham descriptors for all 20 compounds, polarity/polarizability (S), H-bond acidity (A), induced dipole (E), and electrostatic (J(+)) interactions were found to be involved in the sorption of the cations by the resins. After converting the aqueous sorption isotherms to sorption from the ideal gas-phase by water-wet resins, a more significant effect of J(+) was observed. Predictive models were then developed based on the linear regressions and validated by accurately estimating the sorption of different test set compounds with a root-mean-square error range of 0.91-1.1 and 0.76-0.85 for MN500 and Amberlite 200, respectively. The models also accurately predicted sorption behavior of aniline and imidazole between pH 3 and 10.

Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3

The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts.

Heterogeneous catalytic wet air oxidation of refractory organic pollutants in industrial wastewaters: a review

Catalytic wet air oxidation (CWAO) is one of the most economical and environmental-friendly advanced oxidation process. It makes a promising technology for the treatment of refractory organic pollutants in industrial wastewaters. Various heterogeneous catalysts including noble metals and metal oxides have been extensively studied to enhance the efficiency of CWAO. The present review is concerned about the literatures published in this regard. Phenolics, carboxylic acids, and nitrogen-containing compounds were taken as model pollutants in most cases, and noble metals such as Ru, Rh, Pd, Ir, and Pt as well as oxides of Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, and Ce were applied as heterogeneous catalysts. Reports on their characterization and catalytic performances for the CWAO of aqueous pollutants are reviewed. Discussions are also made on the reaction mechanisms and kinetics proposed for heterogeneous CWAO and also on the typical catalyst deactivations in heterogeneous CWAO, i.e. carbonaceous deposits and metal leaching.