A hybrid iron oxyhydroxide agglomerates-ultrafiltration process for efficient removal of chromate.

Hexavalent chromium (Cr(VI)) is often detected in groundwater, surface water and soils. The objective of the research was to study a hybrid process of adsorption onto iron oxyhydroxide agglomerates (IOAs) and ultrafiltration (UF) for removal of Cr(VI) from aqueous solution. Initially, the adsorption of the chromium onto IOAs was characterized by SEM and Raman analyses. Next, the IOAs dosages, required to obtain the regulatory limit of Cr(VI) ≤ 0.05-0.10 mg/L, at varying initial Cr(VI) concentrations, were determined in batch beaker tests and stirred tank reactor. The UF membrane held back efficiently the IOAs, at varying IOAs dosages, transmembrane pressures, and filtration velocities. Cake filtration was determined as the predominant fouling mechanism of the UF membrane. The fouling was reversible by backwash yet, faster fouling rates were obtained in consecutive filtration/backwash cycles. The results point to the applicability of the hybrid adsorption/UF process as a potent method for chromium removal from contaminated water.