Photo driven homogeneous advanced oxidation coupled to adsorption process for an effective arsenic removal from drinking water

The presence of arsenic (As) in drinking water is a major concern for human health. As(III) is the most toxic water-soluble form and it is hard to remove by separation methods, including adsorption, while As(V) is less toxic and easily removable by adsorption. In this work homogenous photo driven advanced oxidation processes (HP-AOPs), namely UVC/H2O2 and UVC/NaOCl, have been investigated in the oxidation of As(III) (initial concentration of 0.1 mg/L) to As(V) and commercial available adsorbents (γ-Al2O3, Bayoxide E33, MgAl-LDHs and ZnAl-LDHs) were tested for subsequent As(V) removal. UVC/H2O2 (99% of As removal, 19 mg/L of H2O2, 2 min of treatment time) and UVC/NaOCl (99% of As removal, 5.1 mg/L of NaOCl, 2 min of treatment time) were found to be more effective than H2O2 (2% of As removal in the same condition of UVC/H2O2) and NaOCl (6% of As removal in the same condition of UVC/NaOCl), respectively and the optimum operation conditions were identified by response surface methodology (RSM) in distilled water and subsequently confirmed in real drinking water (with differences of less than 1%). UVC/NaOCl was the most suitable process being a good compromise among oxidation efficiency, oxidant dose and treatment time. The best results in terms of subsequent removal of As(V) by adsorption were obtained using ZnAl-LDH (88% in both distilled and drinking water). Accordingly, UVC/NaOCl advanced oxidation coupled to ZnAl-LDH adsorption is the best combination for an effective removal of arsenic from drinking water.