416 / 2018-07-27 16:09:41

Adsorption behaviors of Cr(Ⅵ) on to different activated biochar in aqueous solutions

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A novel activated biochar modified by ferric salts was synthesized as a low-cost adsorbent for the removal of Cr(VI) from aqueous solutions.The impregnation of iron on regular biochars and their activated biochar were investigated. SEM, TEM and BET characterizations of the activated biochar revealed that the Fe particles distributed uniformly on the surface or macrospores of carboxylated biochar by strong chemical bonding. The optimum preparation conditions, including different raw material, activation temperature, drying time, and activation time, were chosen. Mass ratios of biochar to ferric salts were optimized.The Cr(VI) removal process was well described using pseudosecond-order kinetic. By Langmuir isotherm model, the Cr(VI) ions adsorption capacity of activated biochar was 25.6 mg·g-1, surpassing original carboxylated biochar (2.1 mg·g-1). Based on X-ray photoelectron spectroscopy (XPS), the mechanism of Cr(VI) reduction reaction with the activated biochar has been unraveled as well. The adsorption recycling test showed that activated biochar kept most of its initial Cr(VI) adsorption capacity at the sixth cycle, and the Fe leakage was small. The results indicated that this novel activated biochar was applicable for the practical treatment of Cr(VI)-containing wastewater.