Elimination of arsenic from the reject solution of the reverse osmosis process

Disposal of the concentrate of the reverse osmosis process (ROC) is a challenge arising from implementing reverse osmosis-based treatments for water supply. Environmentally friendly management options are related to technological changes tending to dismiss the environmental damage and offer reuse of the concentrate. In this work, we study the efficiency of a widely available material (laterite) for arsenic removal from raw ROC belonging to a treatment water supply plant. Assays of laterite were performed under batch conditions, by suspending it in raw ROC solutions enriched with As(V). Results indicated that arsenic adsorption was complete after 6 h of contact. Kinetic adsorption followed a law of the pseudo-second-order, where the rate was 96 g mg-1 h-1. The maximum adsorption capacity and equilibrium constant, which were determined by fitting equilibrium data to the Langmuir model adequately, were 154 mu g g-1 and 0.9 L mu g-1, respectively. The interaction between arsenic and laterite has a physical nature. From the raw ROC with an arsenic concentration near 150 mu g L-1, a reduction of 62% was determined. The final concentrations of the treated solutions resulted in adequate for several reuse purposes in agricultural activities, such as crop irrigation and supplementation of animal drinking water. Reverse osmosis concentrate from the water treatment had an As concentration near 150 mu g L-1 and a high salt content. Arsenic removal in laterite was completed after 6 h of time of contact, and a reduction of 62% of the initial concentration was registered. Treated solutions of concentrate meet the requirements to be reused in agricultural activities.