A novel MD-ZVI integrated approach for high arsenic groundwater decontamination and effluent immobilization

• DCMD-APZ technology shows ability to immobilize and reduce arsenic respectively.
• Optimum conditions for high distillate flux production are depicted.
• Fast adsorption kinetics at t1/2 ≤ 30 min was observed for arsenic immobilization.
• XPS, wet chemistry, and adsorption models confirm immobilization and reduction of As.

A highly effective novel system of direct contact membrane distillation (DCMD) integrated with acid-purged zero-valent iron (APZ) technology has been developed. Compared to conventional processes of arsenic removal which reconstitute secondary contamination at disposal site, this system proves capable of simultaneous removal and immobilization of arsenic from contaminated water with great efficiency and improved water flux. Using composite microporous membranes of polytetrafluoroethylene (PTFE) and polypropylene (PP) integrated with APZ in a DCMD-APZ configuration, varying residual arsenic concentrations were injected anoxically into ≤2 g acid-washed Fuchen (XK 13-201) reduced Fe powder at a flow rate of 0.33 mL/min and pH 6 ± 1.0 at 60 °C. Results from this unique configuration show advantages including maximum distillate flux production of 55.5 kg/m2 h with greater than 95% arsenic rejection efficiency using PTFE/PP composite membrane, fast adsorption and immobilization of rejected arsenic on APZ at t1/2 ≤ 30 min, and electrochemical reduction of As(V) and/or As(III) to sparsely soluble As(0) as confirmed by macroscopic wet chemistry, adsorption kinetic model and X-ray photoelectron spectroscopic (XPS) analysis conducted within 5 days of experimental period. Since the arsenic adsorption/reduction process is a thermodynamically assisted phenomenon, integrated configuration of the DCMD-APZ technology stands out as a promising technique to mitigate the unresolved challenges of arsenic contamination and re-dissolution in groundwater.