Magnetized and functionalized 2-mercaptobenzothiazole nanosilica from rice husk as efficient adsorbent for Hg2+ removal from local gold mining wastewater

Abstract

Wastewater generated during gold recovery from its mined ores usually contains mercury causing water pollution when discharged into rivers disrupting the ecosystem. In this study, magnetized and functionalized 2-mercaptobenzothiazole nanosilica from rice husk (MnS@MBT) was applied to eliminate Hg 2+ from local gold mining wastewater (GMW). The influence of reaction time ( t : 30 – 90 min), dosage ( d : 1 – 3 g), temperature ( T : 30 – 50 o C) and mixing rate ( m : 110 – 130 rpm) was investigated on the removal efficiency of nanosilica from rice husk (nS), its magnetized form (MnS) and MnS@MBT for Hg 2+ removal from GMW. Adsorbents were characterized using BET, SEM, FTIR, XRD, EDX, TGA, pH PZC and saturation magnetization evaluation. At optimum predicted point (where t = 90 min, d = 3 g, T = 50 o C and m = 120 rpm), 81.09 ± 1.03%, 90.77 ± 0.43% and 99.78 ± 0.81% of Hg 2+ was removed from GMW using nS, MnS and MnS@MBT respectively. ANOVA test revealed developed mathematical models are significant. MnS@MBT possessed excellent attributes for Hg 2+ removal having adsorption capacity of 77.30 ± 1.20 mg/g. Experimental data conformed to Freundlich and pseudo-second order kinetic models. Adsorption was spontaneous and exothermic. After five adsorption-desorption cycles, nS, MnS and MnS@MBT could remove 50.27 ± 1.85%, 65.00 ± 1.42% and 91.09 ± 1.91% of Hg 2+ from GMW respectively. The synthesized MnS@MBT was a highly effective, cheap and reusable adsorbent that could be applied in the water treatment plant of a gold mining industry to eliminate Hg 2+ from wastewater.