Photocatalytic Oxidation of Arsenic by Tartrate-Citrate and Citrate and Removal from Groundwater

Solar photocatalytic oxidation and removal of arsenic from groundwater with tartrate-citrate vis-à-vis citrate as photocatalyst was examined. In kinetic tests (5 mg/L Fe(II) and 50 μM catalyst in a 250 μg/L As(III)-spiked groundwater; solar intensity 0.3-0.7 kW/m2) with tartrate-citrate as photocatalyst, 84-87% As(III) oxidation and 89-95% arsenic removal were achieved in 6 h (in suspension: As(V) 210-218 μg/L and As(III) 17-31 μg/L; in filtrate: As(V) 4-8 μg/L and As(III) 8-20 μg/L). With citrate as photocatalyst, similar oxidation kinetics was observed, but the As(III) oxidation and arsenic removal efficiency were somewhat lower – 74-78% and 83-88% (in suspension: As(V) 185-195 μg/L and As(III) 30-52 μg/L; in filtrate: As(V) 10-14 μg/L and As(III) 20-28 μg/L). Extract of tamarind (equivalent to 50 μM tartrate-citrate) as photocatalyst achieved 83-90% arsenic removal from an arsenic-spiked groundwater (As(III) 250 μg/L; Fe(II) 5 mg/L) and 84-86% arsenic removals from an arsenic-bearing groundwater (As(III) 235 μg/L; As(V) 25 μg/L; Fe(II) 4.48 mg/L). Similar arsenic removal (82-84%) was achieved when the method was performed in a 1-L closed PET bottle with the arsenic-bearing water. The method and can be applied at the household level to treat small quantities of drinking water.