| In today’s society, the rapid development of economic science and technology, along with the development is fairly serious and complex environmental pollution problems. A series of problems such as large discharge of waste water containing various kinds of pollutants, automobile exhaust gas polluting atmosphere, water resources scarcity endanger human production and life. The waste water which emissions from metallurgy, electroplating and other industries is still contained in the total amount of copper and zinc and other toxic elements. High salinity waste water from oil production, paper making, printing and dyeing and other fields has a high impact on human life. Usually, there are a lot of methods to removing copper, zinc, magnesium and calcium ions such as chemical precipitation method, ion exchange method, adsorption method, flotation method. Among these methods, the adsorption method with high removal efficiency, good operational flexibility, low cost and so on is applied more widely. Fast adsorption with high adsorption capacity is a simple and effective treatment method. Among the lots of adsorbents for the adsorption of metal cations, the calcined product of layered double hydroxides (LDO) has caused widely concern which has the larger specific surface area, developed pore distribution and renewable reuse. Therefore, co-adsorption of Cu2+ and Zn2+ and single adsorption of Mg2+/Ca2+by LDO become the subject of this paper.In this paper, the hydrotalcite is prepared by co-precipitation method and a new rapid preparation method. And the adsorption material is obtained by high temperature calcination. The physical and chemical properties of adsorbents are characterized by XPS, SEM, XPS, BET and so on. In order to study the adsorption process and mechanism, the thermodynamic experiments, co-adsorption experiments, kinetic experiments, regeneration experiments, and actual wastewater adsorption experiments etc. were carried out.The results show that when the co-adsorption of copper and zinc ions was happened, the adsorption process is in line with the pseudo second order kinetic model, and the adsorption rate of copper ion on the co-adsorption process is promoted, and the presence of zinc ion has a certain inhibitory effect. The amount of saturated adsorption reached by the co-adsorption was lower than that of the single adsorption, but little effect. As the single adsorption of copper and zinc ions, the adsorption removal quantity of zinc ions by LDO is greater than the copper ions’. According to the thermodynamic data of magnesium and calcium ions adsorbed by LDO, it was found that the adsorption isotherms under the three experimental temperatures all accord with the Langmuir model, which is a spontaneous irreversible, endothermic, and chemical adsorption process. From kinetic data, the fitting degree of the pseudo second order kinetic model with two kinds of adsorbed ions is the highest, and the saturation adsorption capacity increases with the increase of temperature, which indicates that it is endothermic reaction. It is mutually verified with the earlier conclusion. At 50℃, the maximum saturated adsorption capacities are 109.77 and 147.71mg/g, respectively. Regeneration experiments show that LDO has a good reuse, at least it can be recycled more than five times. The actual wastewater adsorption experimental results show that LDO can be applied in practical production, and has a broad prospect. |
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