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Adsorption of nitrate on ZnCl2 modified coconut granular activated carbon: kinetics, characteristics and adsorption kinetics

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Document pages: 12 pages

Abstract: Coconut granular activated carbon (CGAC) was impregnated with zinc chloride solution to remove nitrate from aqueous solution. A series of batch experiments were carried out for adsorption isotherm and kinetics. The adsorption of nitrate by ZnCl2 modified CGAC and CGAC accorded with Langmuir and Freundlich models. The batch adsorption isotherms showed that the maximum adsorption capacities of ZnCl2 modified CGAC and CGAC were 14.01   MGN · g − 1 and 0.28   MGN · g − 1, respectively. The kinetic data obtained from batch experiments are well described by pseudo second-order model. The dynamic adsorption process was analyzed by column method. One patient with a maximum bed adsorption capacity of 1.76   MGN · g − 50 obtained an inlet nitrate concentration of   MGN · L − 1, 20   g adsorbent and 10   ml · min − flow rate. The dynamic adsorption data were fitted well to the Thomas and Yoon–Nelson models with coefficients of correlation R2 > 0.834 at different conditions. Surface characteristics and pore structures of CGAC and ZnCl2-modified CGAC were performed by SEM and EDAX and BET and indicated that ZnCl2 had adhered to the surface of GAC after modified. Zeta potential, Raman spectra, and FTIR suggested the electrostatic attraction between the nitrate ions and positive charge. The results revealed that the mechanism of adsorption nitrate mainly depended on electrostatic attraction almost without any chemical interactions.

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