Arsenic adsorption study in acid mine drainage using fixed bed column by novel beaded adsorbent

Abstract

The downflow fixed-bed column adsorption-desorption of arsenic by the beaded coal mine drainage sludge-Youngdong (BCMDS-YD) adsorbent was experimentally studied. The specific surface area of BCMDS-YD synthesized using inorganic binding was 178 m² g^-1, and the pH_IEP was 5.32. The XRD analysis revealed that it was composed of calcite and schwertmannite. As a result, an increase in the inflow rate resulted in an earlier column exhaustion. The breakthrough curve indicated that a smaller adsorbent particle size and lower influent pH prolonged the column life span. Thomas logistic model was applied to fit the breakthrough curve by linear and nonlinear regression. Under the condition of an influent flow rate of 2.65 mL min^-1 (EBCT 40 min), an influent arsenic average concentration of 0.5-1 mg L^-1, an influent pH of 7.6, an adsorbent mass of 100 g, an adsorbent grain size of 1.40-1.70 mm, and an operating temperature of 25 °C, the equilibrium adsorption capacity reached 4.56 mg g^-1. The mechanism of arsenic adsorption is adsorption and precipitation. As a result of the adsorbent reuse experiment, it was judged that it could be reused with good results in all three cycle experiments. The cost of treating arsenic with the BCMDS-YD adsorbent was 0.145 $ per m^-3. The results of this study show examples of sustainable development concepts in mining drainage, and BCMDS-YD can effectively remove arsenic and other heavy metals from acid mine drainage.

Keywords: Arsenic; Beaded coal mine drainage sludge adsorbent; Fixed-bed column reactor; Nonlinear regression; Thomas model.