Microporous ceramic membrane technology for the removal of arsenic and chromium ions from contaminated water

In the present work, we propose novel separation schemes of combined adsorption–ultrafiltration processes for the removal of arsenic and chromium from water. For the removal of arsenic ions, As(V), a combined adsorption–ultrafiltration processes in series is proposed based on Fe2O3 adsorbent nanoparticles [V. Zaspalis, A. Pagana, S. Sklari, Desalination 217 (2007) 167] with an average diameter between 20 and 30 nm and γ-Al2O3 ultrafiltration membranes with an average pore diameter between 3 and 4 nm. It is found from the experimental results that Fe2O3 adsorbent concentration of 0.2 wt% (w/v) is enough to reduce the As(V) concentration in water from an initial concentration of 1 ppm down to 10 ppb, which is the maximum allowable arsenic concentration in drinking water. The subsequent microporous membrane ultrafiltration process delivers 100% sorbent nanoparticle rejection at a purified water flux of 156 kg h−1 m−2, under a transmembrane pressure difference of 3 × 105 N m−2 (3 bar). For the removal of chromium ions, Cr(III), a combined adsorption–ultrafiltration parallel process is proposed using γ-Al2O3 ultrafiltration membranes. Experimental results showed a reduction of the feed chromium concentration of 0.5 ppm to below 10 ppb in the permeate stream, well below the maximum allowable chromium concentration of 100 ppb in drinking water. Furthermore, regeneration of the membranes is achieved by a combined heating and washing procedure process.