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

Abstract

Disposal of the concentrate of the reverse osmosis process (ROC) is a challenge arisingfrom implementing reverse osmosis-based treatments for water supply. Environmentallyfriendly management options are related to technological changes tending todismiss the environmental damage and offer reuse of the concentrate. In this work,westudy the efficiency of a widely available material (laterite) for arsenic removal fromraw ROC belonging to a treatment water supply plant. Assays of laterite were performedunder batch conditions, by suspending it in raw ROC solutions enriched withAs(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 96g mg−1 h−1. The maximum adsorption capacity and equilibrium constant, which weredetermined by fitting equilibrium data to the Langmuir model adequately, were 154μg g−1 and 0.9 L μg−1, respectively. The interaction between arsenic and laterite hasa physical nature. From the raw ROC with an arsenic concentration near 150 μg L−1,a reduction of 62% was determined. The final concentrations of the treated solutionsresulted in adequate for several reuse purposes in agricultural activities, such as cropirrigation and supplementation of animal drinking water.