Feasibility studies on arsenic removal from aqueous solutions by electrodialysis

Abstract

The effectiveness of electrodialysis (ED) in removing inorganic arsenic (As) from aqueous solution was investigated. A tailor-made ED stack was used to perform current-voltage and optimization experiments in a recirculating batch mode. Samples were pre-oxidized with NaClO using 1:2 sample to oxidant weight ratio (R_S:O) to transform 100% of As(III) to As(V) in 180 seconds. A high feed water conductivity of 1500 μS/cm and a low feed water conductivity of 800μS/cm had limiting currents of 595 mA and 525 mA, respectively. Optimum experimental conditions that provided maximum As separation were applied potential (E) of 12 V, feed flow rate (Q) of 0.033 L/s, feed concentration (C) of 662.0 μg L⁻¹, and operating time (t) of 45 min, the most significant ones were applied potential, feed concentration and operating time. Model confirmation experiments showed a good agreement with experimental results with only 0.031% error. The total As in the diluate stream was 4.0 μg L⁻¹, consisting of an average of 3.0 μg L⁻¹ As(V) and 1.0 μg L⁻¹ As(III).

Keywords:

• Electrodialysis
• arsenic removal
• limiting current density