Effectively arsenic(V) and fluoride removal in geothermal water using magnetic Fe3O4@MgO nanoparticles

Abstract

High residual concentration of arsenic and fluoride is a tricky problem to be solved in the process of reinjection after geothermal water utilization. We develop a method to simultaneously remove As(V) and F− from geothermal water using magnetic Fe3O4@MgO adsorbent, fabricated via a one-step method. The effects of pH, contact time, adsorbent dose and temperature on the removal efficiency were investigated systematically. The results show that the Fe3O4@MgO composite has a wide range of pH (2–11), ultrafast removal dynamics (As(V): 2 min; F−: 30 min), and high removal efficiency (As(V): 99.9%; F−: 96.6%). The adsorption kinetics follows the pseudo-second-order kinetics model, and the adsorption isotherm model fits Freundlich. The adsorption capacity of As(V) and F− can reach 123 and 98.4 mg/g, respectively. The exchange of As(V) and F− with Mg-hydroxyl groups hydrolysis by MgO was determined the adsorption mechanism. The Fe3O4@MgO adsorbent was capable of achieving the adsorption efficiency as high as 99.9% for As(V) and 97.3% for F− in real geothermal water, respectively. Hence, the proposed Fe3O4@MgO composite exhibited as an excellent adsorbent for the remediation of As- and F-contaminated geothermal water.