Removal of Reactive Black 5 by zero-valent iron modified with various surfactants

Zero-valent iron (ZVI) particles were synthesized by the aqueous phase borohydride reduction method, and the synthesized ZVI particles were used for the reductive degradation of Reactive Black 5 (RB5) dye in aqueous solution. The sizes of the synthesized ZVI particles were in the microscale range, with an average diameter of 13.57 μm. To study the efficiency of surfactant-treated ZVI particles for the decolorization of RB5 solution, three different surfactants, triton X-100 (TX100, non-ionic surfactant), cetyl trimethyl ammonium bromide (CTAB, cationic surfactant), and sodium dodecyl sulfate (SDS, anionic surfactant) were selected for the treatment of ZVI. The normalized residual concentration after decolorization of 500 mg/l RB5 by ZVI for 3 h was 0.236, while ZVI particles treated with TX100 (0.5 g/l), CTAB (1.0 g/l), and SDS (2.5 g/l) exhibited normalized residual concentration of 0.172, 0.154, and 0.393, respectively, after 3 h. The color removal efficiency was found to be increased with decrease in initial pH of dye solution, and ZVI exhibited good color removal efficiency at acidic pH. Decolorization kinetics by pseudo-first-order rate equation showed that removal rate was increased after treatment with TX100 as well as CTAB, while that was reduced after SDS treatment.