Optimization of continuous arsenic biosorption present in natural contaminated groundwater

Abstract

BACKGROUND: Arsenic (As) is a serious water pollution problem in the world. In Argentina, it is related to old volcanic activities; for example, the western region of Santa Fe State has concentrations higher than 0.1 mgAs L −1 . In this work, a green, sensitive method was used to determine As concentration, and its removal using chitosan in bed columns was studied. Mathematical models were used to explain sorption, and the process was optimized using statistical methods. RESULTS: Arsenic quantification was realized with a bespoke modification of the As molybdenum blue method (detection limit = 0.0048 mg L −1 , quantification limit = 0.0145 mg L −1 ). Chitosan molar mass, pH ZPC and deacetylation degree were 350 ± 10 kDa, 6.3% and 76.2%, respectively. A maximum of 68.5% was obtained for As(V) removal at optimum conditions. Raising the bed column height produced an increment in breakthrough times, and the sorption process was favoured using low flow rates. Salinity, phosphate and nitrate concentration reductions were 60%, 50% and 70%, respectively. CONCLUSIONS: Sorption studies have been carried out on groundwater, using columns packed with chitosan for arsenic removal. The process was optimized by a factorial design. Elution profiles were adjusted adequately with mathematical models. The modified analytical technique for arsenic quantification applied in groundwater, was successful.