Removal of silica from brackish water by integrated adsorption/ultrafiltration process.

A lab-scale unit of the hybrid continuous stirred tank reactor (CSTR) adsorption/ultrafiltration (UF) system was used to evaluate the removal efficiency of silica from brackish water. The semi-batch adsorption process was carried out using iron oxy/hydroxide agglomerates (IOAs) as adsorbent and hollow fiber ultrafiltration membrane as a barrier to the adsorbent passage to the product water. The effect of residence time, concentration of silica, and adsorbent dosage on the silica removal and UF membrane blockage was examined. It was found that a short residence time of 15 min was sufficient to achieve the maximum adsorption capacity similar to that obtained in batch isotherm experiments. The adsorption capacity increased with the augmentation of the silica concentration and decreased with the increase in the adsorbent dosage. The UF was effectively employed to separate the loaded adsorbent without fouling the membrane until breakthrough. A simple model was applied to accurately predict the adsorption breakthrough curves.