Adsorption Of Cu²⁺ And Zn²⁺ From Simulated Wastewater By Walnut Shell

Using walnut shells as adsorbent to remove Cu2+and Zn2+from simulated wastewaterthrough static adsorption experiments. Through single component adsorptive experiment andcompetitive adsorption experiment to research the adsorption characteristics of walnut shell toCu2+and Zn2+.In the one-component adsorption experiments, the factors including particle size, watersamples of initial pH, adsorbent dosage, water samples of initial concentration, adsorptiontime ect. were inspected to the effects of the adsorption to determine the optimum parametersof the adsorption.Adsorption kinetics and adsorption isotherm were analysed.In the static adsorption experiment of Cu2+, the adsorption capacity reached the peak forCu2+in25℃when the initial pH was5.0, particle size was1.25~1.60mm of the walnut shell,powder dosage was2.5g, oscillation speed reached200r/min, and the adsorption time was360min, all above leads the removal rate of Cu2+reached75.7%, and the adsorption capacityof Cu2+0.702mg/g.The pseudo-second-order model was fitted to describe the adsorption ofCu2+, it was shown that adsorption rate for the metal ions in proportion to the square of theconcentration. At the same time, the equilibrium concentration of adsorption fitted well withLangmuir isotherm equation, the process of adsorption was single molecular layer adsorption.In the static adsorption experiment of Zn2+, the adsorption capacity reached the peak forZn2+in25℃when the initial pH was6.0, particle size was1.60~2.50mm of the walnut shell,powder dosage was1.2g, oscillation speed reached200r/min, and the adsorption time was360min, all above leads the removal rate of Zn2+reached59.7%, and the adsorption capacityof Zn2+0.258mg/g.The pseudo-second-order model was fitted to describe the adsorption ofZn2+, it was shown that adsorption rate for the metal ions in proportion to the square of theconcentration. At the same time, the equilibrium concentration of adsorption fitted well withLangmuir isotherm equation, the process of adsorption was single molecular layer adsorption.In the competitive adsorption experiments, the influence of Cu2+on the absorption ofwalnut shell to Zn2+were More obvious than Zn2+to Cu2+. It shows that through preferenceadsorption experiment, the adsorption properties of walnut shell on the Cu2+is better than thatof Zn2+, and the adsorption on Cu2+is more stable.Through the analysis of the dynamics equation of adsorption and adsorption isothermequation, and the study of infrared spectrum and scanning electron microscopy (sem), toanalysis the walnut shell adsorption mechanism of the adsorption of Cu2+and Zn2+. The resultshows that adsorption of Cu2+and Zn2+on walnut shell is a complex process, which may have molecular force absorption, ion exchange adsorption, surface complexation, inorganicprecipitation, and coordination, etc.