Reduction and adsorption of Cr (Ⅵ) in wastewater by Tieguanyin tea stalk
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Abstract:
A series of single factor experiments were employed to study the effect of a novel adsorbent, Tieguanyin tea stalk, for the reduction of the high toxic heavy metal Cr (Ⅵ) to Cr (Ⅲ) which is low toxic even nontoxic. Two adsorption isotherm models and two adsorption kinetic models were used to simulate the experimental data. The characterization methods, SEM, BET, FTIR and XPS were employed to discuss the reduction and adsorption mechanism. The results show that the bigger tea stalk diameter, the more dosing quantity or pH ≤ 11, the higher removal rate of Cr (Ⅵ); The influence of the coexisting ions Ca (Ⅱ) and Ni (Ⅱ) to adsorption of Cr (Ⅵ) by tea stalk are weak. The Freundlich isotherm model and the Pseudo-second-order model fit closely to the experimental data. Tieguanyin tea stalk, Pu'er tea stalk and Tieguanyin tea stalk modified by maldehyde show better performance than activated carbon under certain conditions. The characterization results show that the reduction and adsorption plays important roles on the removal efficiency of Cr (Ⅵ) in water by tea stalk, and the functional groups of the hydroxyl, amino and acyl are involved in the reduction and adsorption of Cr (Ⅵ) by tea stalk.
