Arsenic Removal Using Advanced Reduction Process

Abstract

The effectiveness and feasibility of Advanced Reduction Process on arsenic has been studied. Advanced Reduction Process generates highly reducing radicals using a combination of a reducing reagent and UV light. These highly reducing radicals react with arsenic (oxidized specie) to convert it to elemental arsenic that is insoluble in water.

Screening experiments were conducted to identify the most effective ARP combination of a suitable reagent that gives maximum removal of arsenic. Three reagents (dithionite, ferrous ion and sulfite ion) were tested and dithionite was chosen to be the best amongst the three. This was based on faster kinetics and higher removal than other reagents.

Dithionite was further tested for effectiveness using various UV intensities, different initial dithionite concentrations and at 5 different pH (5, 6, 7, 8, and 9) conditions.

A kinetic study of changing arsenic and dithionite concentrations with time was done to better understand the reaction. Resolubilization of arsenic continues to be the challenge. However, pH 8 showed maximum removal of arsenic. And As (V) showed a better removal than As (III) species.