Carbonized polyaniline-activated peracetic acid advanced oxidation process for organic removal: Efficiency and mechanisms.

Recently, advanced oxidation processes (AOPs) based upon peracetic acid (PAA) with high efficiency for degrading aqueous organic contaminants have attracted extensive attention. Herein, a novel metal-free N-doped carbonaceous catalyst, namely, carbonized polyaniline (CPANI), was applied to activate PAA to degrade phenolic and pharmaceutical pollutants. The results showed that the CPANI/PAA system could effectively degrade 10 µM phenol in 60 min with low concentrations of PAA (0.1 mM) and catalyst (25 mg L-1). This system also performed well within a wide pH range of 5-9 and displayed high tolerance to Cl-, HCO3- and humic acid. The nonradical pathway [singlet oxygen (1O2)] was found to be the dominant pathway for degrading organic contaminants in the CPNAI/PAA system. Systematic characterization revealed that the graphitic N, pyridinic N, carbonyl groups (CO) and defects played the role of active sites on CPANI during the activation of PAA. The catalytic capacity of spent CPANI could be conveniently recovered by thermal treatment. The findings will be helpful for the application of metal-free carbonaceous catalyst/PAA processes in decontaminating water.

Oxidation of pyrazolone pharmaceuticals by peracetic acid: Kinetics, mechanism and genetic toxicity variations.

Peracetic acid (PAA) oxidation is an emerging technology in water disinfection and purification. This study evaluated the oxidation of three pyrazolone pharmaceuticals (i.e., Aminopyrine (AMP), Antipyrine (ANT), and Isopropylphenazone (PRP) by PAA. Experimental results showed that PAA exhibited structure selectivity to the above three pharmaceuticals and oxidized AMP with the highest reactivity. The degradation kinetics of AMP was investigated by calculating the apparent second-order rate constants (kapp) under different initial pH. Through kinetic simulation, the second-order rate constants of elementary reactions between AMP (i.e., neutral (AMP0) and protonated (AMP+) species) with PAA (i.e., neutral (PAA0) and anionic (PAA-) species) were obtained to be 0.34 ± 0.077 M-1 s-1(k"AMP+, PAA0), 0.89 ± 0.091 M-1 s-1(k"AMP0, PAA-) and 5.94 ± 0.142 M-1 s-1(k"AMP0, PAA0), respectively. The PAA could oxidize AMP via electrophilic attack, and the degradation site of AMP was confirmed to be the central nitrogen of -N(CH3)2 with the highest relative electrophilicity (sk-/sk+, 48.8614) by Density Functional Theory (DFT) calculation. The intermediates/products of AMP degradation were identified by high-performance liquid chromatography-mass spectrometry (LC-MS/MS), and the transformation pathways of AMP during PAA oxidation were inferred to be hydroxylation, demethylation, and CC cleavage. The genetic toxicity of AMP contaminated water could be reduced after PAA oxidation, which was evaluated by the micronucleus test of Vicia faba root tips.