Chromium (Ⅵ) Removal From Aqueous Solutions Using A Composite Synthesized With A Dolomite-montmorillonite-corn Stover Mixture

Chromium pollution frequently happens in China in recent years. It has arousedwide concern among the public due to its severe impact on human health andenvironment. Dealing with this issue should depend not only on regulatory andsupervision system by nation, but on the development of pollution control techniques.Adsorption method is an attractive alternative, because it is efficient, easy to operateand environment friendly.The study focused on chromium (VI) removal using composite adsorbent, trying toprovide theoretical support for developing adsorbent to remove chromium (VI) fromwater. This composite adsorbent can improve adsorption capacity of single material,enhance environmental adaptation, effectively utilize agricultural wastes, avoidblocking and is easy to recycle.In this study, a novel calcined composite (D=2~3) comprising dolomite,montmorillonite and corn stover was developed. Batch experiments were conductedto investigate the effects of composite dosage, contact time, solution pH, temperatureand co-existing ions on chromium (VI) removal efficiencies. Equilibrium was reachedin72h. Chromium (VI) removal efficiency changed with the increasing amount of thecomposite. The trend present increase first, then keep flat, finally decrease slowlywhile solution pH increased from2.0to11.0. The maximum removal efficiency (86%)was reached in pH4~9. Chromium (VI) removal efficiency increased when thetemperature raised from293to313K, indicating that high temperature favored theremoval process. This conclusion was also confirmed by adsorption energy evaluationwhere the reaction process was found to be endothermic and spontaneous. Theremoval process well fitted the pseudo-second-order kinetic model. Fitting of theexperimental results with the intraparticle diffusion model revealed that the adsorptionprocess was controlled by the film diffusion process. Isotherm studies fitted Langmuirmodel very well demonstrated that the homogeneity of the composite surface andphysical forces may affect the removal process more significantly.