Adsorption of arsenic on the reused sanding wastes calcined at different temperatures

The removal capacity of arsenic(III), As(III), by the reused sanding wastes prepared at different calcination temperatures was investigated in this study. As a pretreatment process for the preparation of the reused material from raw sanding wastes (RSW), calcination was performed in a furnace at 550, 750, 900, 1100, and 1300 °C. After calcination at 550 °C, aluminum hydroxide which is a major inorganic composition in the RSW was transited to amorphous aluminum oxide. As the calcination temperature increased, a slightly developed crystallinity was noted up to 950 °C without variation of mineral type but a greatly developed crystallinity as well as changes in the mineral type was observed after 950 °C. When the calcined sanding waste (CSW) was applied in the treatment of As(III), maximum adsorption was observed around pH 8. Adsorption capacity of As(III) onto the CSW was gradually reduced as the calcination temperature increased up to 950 °C and then was greatly reduced after 950 °C due to the decreased surface area, much developed crystallinity, and change of the mineral type on the surface of CSW. From the investigation for the pore diffusion in the adsorption process, the rate constants of the intraparticle diffusion (Kp) for As(III) decreased as the calcination temperature increased. This result suggests that intraparticle diffusion become an important adsorption process when adsorbents having well developed surface are used in the adsorption. Adsorption isotherms were better described by the Langmuir equation than by Freundlich equation. The CSW was applied to treat leaches of one real mine tailing and mine drainages from two abandoned mines in Korea. The leaches of real mine tailing contained approximately 50% of As(III) in total arsenic concentration. When the CSW was applied to treat real wastewater, near complete arsenic adsorption was observed within 30 min with good removal efficiency, which meets the national wastewater discharge limits.