Removal Of Hexavalant Chromium From Aqueous Solution By Nano Zero-valent Iron/Sargassum Horneri Based Activated Carbon

With the large surface area and the high reactivity of nano zero valant iron, it has received much attention in removal of hexavalent chromium in aqueous solution. Besides, to improve the agglomeration and nanotoxicity of NZVI, carrier have drawn scientists’ eyes, especially active carbon, which can improve the chemical property of metarial and efficiency of reaction to remove high concentration(90-120 mg·L-1)of hexavalant chromium in aqueous solution.NZVI/SAC were prepared from Sargassum Horneri based activated carbons by the methods of equal volume impregnation, roasting method and liquid phase reducing method. The NZVI/SAC was applied in hexavalent chrome adsorption within simulated wastewater. Based on the analysis of removal of hexavalant chromium in aqueous solution, the optimal conditions of the reaction was determined through one factor experiments. Furthermore, the kinetics, thermodynamics and mechanism of the reaction were discussed.The results indicated that:(1) The removal of hexavalant chromium by NZVI/SAC could improve the aggregative of NZVI and reach the national standards for hexavalant chromium, which showed NZVI/SAC was a high- performance metarial that was well suited foe treating waste water containing hexavalant chromium.(2) NZVI/SAC could be prepared by liquid phase reducing method, under the condition of heating rate of 10 ℃·min-1, baking time of 240 min, baking temperature of 600 ℃, reduction time of 120 min, reduction temperature of 5 ℃, molar ratio of 5 and the nitrogen atmosphere.The NZVI/SAC consisted of mainly 30-150 nm spherical particles aggregated into chains of individual units and performed better than that of NZVI and SAC.(3) The final hexavalant chromium removal percentage was up to 100% at 30℃, pH = 2, NZVI/SAC dosage of 2 g·L-1 and the amounts of NZVI loaded on SAC of 30%. And the equilibrium time was 10 minutes. Hexavalant chromium is mainly reduced to insoluble Cr(Ⅲ) compound in the reaction with NZVI/SAC.(4) The adsorption isotherm of NZVI/SAC for removal of hexavalent chrome matched Langmuir model and Freundlich model, and adsorption rate fit the Lagrange Pseudo-second-order kinetics equation and Pseudo-first-order kinetics equation.(5) NZVI/SAC showed good selectivity for Cr(Ⅵ), and it could remove a little Ni2+ in aqueous solution, which provided theoretical basis for its practical application.