Adsorptional Characteristics And Adsorptional Mechanism Of Cadmium And Copper By The Complex Of Cyanobacterial Bloom Biomass And Sediment

At present, the studies regarding the interaction mechanism of metal and algea are still in the intitial stage. Moreover, there is less information available on heavy metal biosorption by cyanobacterial bloom biomass, and the information about the interaction between the algae-sediment complex and heavy metal is limited even in the simulation environment.Using cyanobacterial bloom biomass and the sediment originated from Lake Dongting as materials, this thesis studied the adsorption characteristics of cadmium and copper by algae-sediment complex at different conditions, e.g. proportion of algae-sediment, different pH, different initial metal concentration, different temperature, and different adsorption time. The desorption of cadmium and copper from algae-sediment complex were also involved in this study.The effects of different ratio of cyanobacterial bloom biomass in algae-sediment complex (0%?5%?10%?20% and 40%) on the adsorption of cadmium and copper by algae-sediment complex were studied. The results indicated that cyanobacterial bloom biomass content had important effects on the adsorption of heavy metals by algae-sediment complex, and with the increase of ratio of cyanobacterial bloom biomass, the adsorption efficiency of heavy metals was increased.The effects of pH (4-8) on the adsorption characteristics of Cd(?) and Cu(?) was studied. The results showed that pH played a vital role in adsorbent process. The adsorption efficiency was very low when the pH was 4-5, and the maximum adsorption capacity for Cd(?) and Cu(?) was 0.98 mg/g and 5.27 mg/g, respectively. The adsorption efficiency increased when the pH was above 6, and the maximum adsorption capacity for Cd(?) and Cu(?) was 3.09 mg/g and 15.53 mg/g, respectivelyThe maximum adsorption capacity of Cd(?) by algae-sediment complex completed within 2 hours and adsorption characteristics was in consistent with pseudo-first-order model, R2>0.9. The biosorption kinetics was found to be fast, about 80%-90% of the total adsorbed heavy metal ions were removed from the solution within 30?40 min.The sorption of Cd(?) and Cu(?) by algae-sediment complex increased with the increase of initial metal concentration. The adsorption equilibriums of Cd(?) and Cu(?) could be represented by Langmuir isotherms and Freundlich isotherms, R2>0.8. However, the Freundlich model exhibited a slightly better fit to the biosorption date than Langmuir model.The results showed that the biosorption wasn't affected by temperature.The amount of Cd(?) desorped by H2O, NH4NO3 and EDTA was 1.5%?2.36%, 42.23%?61.33% and 57.63%?59.77%, respectively. The amount of Cu(?) desorped by H2O, NH4NO3 and EDTA was3.38%-5.94%,84.01%?94.18% and 35.21%?46.24%, respectively.