Removal of Hexavalent Chromium from Aqueous Solutions by Sodium Dodecyl Sulfate Stabilized Nano Zero-Valent Iron: A Kinetics, Equilibrium, Thermodynamics Study

Sodium dodecyl sulfate stable nanoscale zero-valent iron (SDS-nZVI) was synthesized by the sodium borohydride reduction method, characterized with SEM and XRD. SDS-nZVI was used for the removal of Cr (VI) from aqueous solutions at different conditions in a batch process. XRD analysis indicated the presence of iron oxide and iron-chromium hydroxide coprecipitation on the surface of SDS-nZVI after reaction some time. The reaction kinetics, mechanism, isotherms, and thermodynamics for Cr (VI) removal of aqueous solution via SDS-nZVI were investigated. The pseudo-second-order model was relatively suitable for describing the reaction process. Intraparticle diffusion model was used to analysis the mechanism, the results indicated that there were two processes (bulk diffusion and surface diffusion) controlling the reaction rate, while only one was rate limiting in any particular time range. The fitted Temkin and D-R model satisfactorily explanted the experimental data in the range of 303-343K. The maximum removal capacity of SDS-nZVI for Cr (VI) was obtained for 336.7mgg(-1) at 303K. The overall removal process was endothermic. These results demonstrated that SDS-nZVI could potentially be used as an effective material for environmental remediation.