The leachate from the Zixiaguan landfill of Wuhan City contains a lot of undesirable or toxic chemicals, among which arsenic may have the most serious threat to environment and human health. Lowering the arsenic concentration in the leachate is therefore of extreme importance. In this study, natural sediments obtained from Wuhan City, including clay, silty soil and silty sand, were used as low-cost sorbents to remove arsenic from solution. The results of the batch sorption experiments indicate that the sorption processes of clay and silty sand match well with linear isothermal sorption model, while that of silty soil is in good accordance with Langmuir isothermal sorption model. Among the three sorbents, clay has the best ability for arsenic removal from solution. Further experiments were carried out to determine the optimum sorption conditions for clay sorbent, the results showing that as the ratio of sorbent dosage to solution volume is 25.0 g/L, the reaction time is 120 min, and the pH of solution equals 7.0, the removal rate of arsenic from the leachate by clay sorbent reaches the highest value of 99.3 %.
Takovite, a kind of hydrotalcite-like compounds (HTlcs), was used for boron removal from water. It was prepared by coprecipitation method and characterized by X-ray diffraction technique (XRD). The equilibrium time of boron sorption by takovite as well as its boron uptake capacities was determined by the reaction kinetic experiments and isotherm sorption experiments. The effects of experimental conditions on boron removal efficiency were also evaluated. Generally, the boron uptake by takovites increases with increasing initial boron concentration in solution. The isotherm sorption data match well with the Freundlich model, indicating that the anion exchange contributes a lot to solution deboronation. Moreover, at higher temperature, greater boron removal by takovite was observed. As compared to calcined takovite, uncalcined takovite has better performance in terms of boron uptake, since the structural restoration of calcined takovite didnt happen during its contact with boron-containing solution, which is quite different from the behavior of other HTlcs as reported.
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