Arsenate removal from aqueous media on iron-oxide-coated natural rock (IOCNR): a comprehensive batch study

摘要

Iron-oxide-coated natural rock (IOCNR) was used as an adsorbent of arsenate, As(Ⅴ), from aqueous solution. Batch adsorption studies were performed at 25 ± 2℃ and pH 5.7 ± 0.2 with agitation at 200 rpm. Based on a batch study, 0.148 mm particles were adopted in this investigation. A 5 gL~(-1) dose of adsorbent removed ～99.6% As(Ⅴ) from the aqueous media within a shaking time of 4 h when the initial As(Ⅴ) concentration was 3 mg L~(-1) . The adsorption process followed the pseudo-second-order kinetic model. The maximum adsorptive capacity of IOCNR was calculated from the Langmuir isotherm 16.92 mgg~(-1). The D-R isotherm revealed the nature of the adsorption process. The dimensionless parameter (R_L) and Gibbs free energy changes (ΔG~0) suggest that the process is favorable and spontaneous. The study was performed in the presence of different coexisting ions, including organic contaminants, at various pH values of the medium, to determine their effects on the removal of As(Ⅴ). Film diffusion controlled of the process was evidenced from the D_f value and multiple interruption tests. The As(Ⅴ) removal efficiency (%) was compared with that of the patented adsorbent LEWATIT FO36. Finally, the IOCNR has been applied to remove arsenic from real arsenic-bearing sample.