Removal of p-arsanilic acid and phenylarsonic acid from water by Fenton coagulation process: influence of substituted amino group

Simultaneous degradation of organoarsenic and immobilization of arsenate by an electroactive CuFe2O4-CNT/peroxymonosulfate platform: Insights into the distinct roles of the Cu and Fe sites

Phenylarsonic acid (PAA) compounds, widely used in animal husbandry, pose a considerable environmental threat owing to their potential transformation into toxic inorganic arsenic species. To efficiently decontaminate PAA and adsorb secondary As(V), a hybrid CuFe2O4-modified carbon nanotube (CuFe2O4-CNT) filter was developed in this study. The hybrid CuFe2O4-CNT filter functioned as an effective catalyst, convective filtration medium, electrode, and adsorbent. Moreover, it removed 97 % PAA within 80 min in circulation mode under optimal conditions (25 °C, pH0 = 7, peroxymonosulfate [PMS] = 1.5 mM, and voltage = 1.0 V), with a total As removal efficiency of 94 %. Experimental and theoretical studies showed that the (100) and (211) planes of CuFe2O4-CNT contributed to PMS activation and As(V) adsorption, respectively. Quantum chemical calculations and high-performance liquid chromatography-mass spectrometry analysis determined the energy barriers for reactions between the transient state and SO4•- and HO•, based on which potential PAA degradation pathways were proposed. Additionally, the negligible loss of efficiency in practical water samples and acceptable leached metal ion concentrations (Cu < 0.1 mg/L and Fe < 0.15 mg/L) confirmed the reusability and stability of the filter. This study provides a promising strategy for organoarsenic decontamination by combining electrocatalytic PMS oxidation and filtration techniques.

Progress of photocatalytic oxidation-adsorption synergistic removal of organic arsenic in water

Photocatalytic oxidation-adsorption synergistic treatment of organic arsenic pollutants is a promising wastewater treatment technology, which not only degrades organic arsenic pollutants by photocatalytic degradation but also removes the generated inorganic arsenic by adsorption. This paper compares the results of photocatalytic oxidation-adsorption co-treatment of organic arsenic pollutants such as monomethylarsonic acid, dimethylarsinic acid, phenylarsonic acid, p-arsanilic acid, and 3-nitro-4-hydroxyphenylarsonic acid on titanium dioxide, goethite, zinc oxide, and copper oxide. It examines the influence of the morphology of organic arsenic molecules, pH, coexisting ions, and the role of natural organic matter. The photocatalytic oxidation-adsorption co-treatment mechanism is investigated, comparing the hydroxyl radical oxidation mechanism, the hydroxyl radical and superoxide anion radical cooxidation mechanism, and the hydroxyl radical and hole cooxidation mechanism. Finally, the future prospects of metal oxide photocatalytic materials and the development of robust and efficient technologies for removing organic arsenic are envisioned.

High efficient removal of 4-aminophenylarsonic acid from aqueous solution via enhanced FeOOH using Mn(VII)

Efficient removal of 4-aminophenylarsonic acid from contaminated water sources is essential to mitigate arsenic pollution. We proposed a competent technique to achieve 4-aminophenylarsonic acid removal via adsorption on enhanced α-FeOOH using various concentrations of Mn(VII). The elimination rate of 4-aminophenylarsonic acid applying FeOOH with Mn(VII) was dependent on acidic conditions. More than 99.9% of 4-aminophenylarsonic acid was eliminated in a 6-min reaction time under acidic conditions. The reaction of 4-aminophenylarsonic acid was fast at 4.0 and 5.0 pH, with its complete oxidation into arsenate and the liberation of manganese Mn(II) in the initial stage of the reaction. Similarly, the reaction rate constant (k_obs) decreased from 0.7048 ± 0.02 to 0.00155 ± 0.00007 as the pH increased from 4.0 to 9.0. Oxidation capacity was considerably enhanced via the removal of electrons from 4-aminophenylarsonic acid to Mn(VII) after the creation of its radical intermediate and further change in Mn(III) to Mn(II) in the solution. The results showed that Mn(VII) played a crucial role in 4-aminophenylarsonic acid degradation at a low pH (e.g., 4.0), and the oxidation process proceeded in different manners, namely, electron transfer, hydroxylation, and ring-opening. These results illustrated that Mn(VII) is an effective, economic purification process to mitigate 4-aminophenylarsonic acid generated from poultry waste.