Sulfite activation by a low-leaching silica-supported copper catalyst for oxidation of As(III) in water at circumneutral pH

Sulfite activation by metal is a promising SO4 center dot- -based advanced oxidation process (SR-AOPs) for pollutant removal. Homogeneous systems are limited by strict working pH and metallic oxide sludge generation. To overcome these drawbacks, a copper-silica composite modified by ammonia (CuNSi) was synthesized through a complexation-adsorption-combustion method and characterized by X-ray diffraction, X-ray photoelectron spectroscopies, transmission electronic microscopy etc. CuNSi demonstrates a stable and remarkable catalytic activation of sulfite for As(III) oxidation after five reuses in neutral wastewater. The negligible oxidation of As (III) under anoxic condition confirmed the importance of oxygen for the CuNSi/sulfite system. Bicarbonate significantly inhibited As(III) oxidation, whereas Cl-and NO3 slight restrained As(III) oxidation. The dosage of sulfite and As(III) affected initial rates of As(III) oxidation via the equation r(0)= k(r) x [Sulfite](2.11) x[As(III)](0.33) (k(r)=(3.68 +/- 0.46) x 10(3)M(-1).44 min(-1)). The apparent activation energy for As(III) oxidation was 60.14 +/- 5.17 kJ mol(-1). The SO4 center dot--was confirmed as the primary oxidative species, and the sulfite activation by CuNSi was through a Cu(II)-Cu(I)-Cu(II) cycle. Overall, this study suggests that the CuNSi/sulfite system can be a promising AOP for further application in wastewater treatment.