Study On Adsorption Properties Of Bentonite Based Adsorbents For Heavy Metals

This thesis reviews the present situation and the harm of heavy metal pollution, introduced briefly the research progress of treatment technology of wastewater containing heavy metals at home and abroad, and studied systematically on the mineral composition and physicochemical properties of bentonite of Handan. Taking Handan bentonite as the main raw material, a variety of bentonite based new adsorption materials with excellent performance were prepared. The physical and chemical properties of bentonite, activated with sulfuric acid, hydrochloric acid and bentonite / polyacrylic acid / xanthan gum composite adsorption materials were characterized using SEM, XRD, IR and other modern means of technology. In a the background of simulated wastewater and static adsorption, through changing the various operating conditions, such as temperature, p H value, reaction time, the optimum reaction conditions of heavy metal pollutants of the simulated wastewater adsorption on a variety of bentonite based adsorbents were derived from a number of experiments. These experiments were in order to obtain the highest removal rate and the best adsorption effect, and try to keep the energy consumption of experiment process low, also to minimize the possibility of the twice pollution to our the environment. And on this basis, the sorption mechanism was investigated by means of modern teconologies, for example, SEM, IR. The main achievements of this thesis are as follows:1. The bentonite adsorbents activited by sulphuric acid, hydrochloric acid(marked as HB,CB respectively) were prepared and the propeties for adsorbing copper and the effect of initial concentration, temperature, p H value,doses of adsorbent, and contact time and the adsorption mechanism were studied contrastively. The results showed that HB and CB had high soption rate of copper (HB>CB) and reasched 99%, 96% respectively. The best adsorption conditions were:initial concentration of Cu2+ 3mg/L, dosage of adsorbents(HB and CB)2g/L and 4 g/L, p H=6-8,contact time 15 min, temperature 18℃-25℃.2. The polyacrylic acid/xanthan/Bentonite composite adsorbent (HB/PAA/XG) was prepared with acrylic monomer combined with xanthan gum and bentonite by in-situ polymerization and was characterized by SEM, IR, XRD and so on. The infuluence of p H, contact time, doses of adsorbent, initial concentration on adsorption were also investigated. The best conditions of adsorption of Cu2+、Ni2+、Cr(Ⅵ)and Zn2+ on HB/PAA/XG were obtained.3. The adsorption mechanism was mainly chelation between-OH, COO- and Cu2+、Ni2+、Cr(Ⅵ)Zn2+ combined with ion exchange. With toxic metal pollutants which have the property of accumulation as the object of the research, the paper studied their adsorption performance on bentonite activated by sulfuric acid, hydrochloric acid and bentonite / polyacrylic acid / xanthan gum composite adsorbent, which provides a theoretical basis for the actual treatment of heavy metal wastewater by bentonite based adsorbents. The study has some practical significance.