Separation And Recovery Of Lead Ions From Complex System By Modified Bagasse

Lead-containing wastewater produced in industrial processes is harmful to the environment and human health and it was urgent to be treated.Compared with other heavy metal treatment methods,the biosorption using straw,such as bagasse as adsorbent,has attracted much attention due to its advantages of aboudant source,low cost,and little secondary pollution.However,the untreated biosorbent raw materials have poor adsorption selectivity for heavy metal ions and poor ability to treat wastewater.Therefore,in this thesis,the sugarcane bagasse was used as the research object,and the phosphate modified bagasse with high selectivity to Pb²⁺was prepared.The selective adsorption behavior and mechanism of modified bagasse on Pb²⁺were discussed.The specific research results are as follows:?1?Phosphoric acid modified bagasse with high selectivity for Pb²⁺was prepared by chemical grafting method.SEM,FTIR,EDX and Zeta potential were used to characterizate the unmodified and modified SCB,results showed that the phosphate groups were successfully modified on the surface of SCB.The maximum adsorption capacity of PA-SCB for Pb²⁺was 0.71 mmol g^-1.The adsorption of Pb²⁺on modified bagasse can fitted well by Langmuir isothermal adsorption model and pseudo-second-order kinetics model,and the optimum adsorption p H range was 4.5-6.0.?2?Competitive adsorption behavior and mechanism of Pb²⁺and coexisting ions on PA-SCB in Pb/Cu,Pb/Zn,Pb/Cd and Pb/Ca two-component systems fixed-bed column were studied.Results showed that breakthrough curve of Pb²⁺presented an typical"S"shape,while the adsorption capacity of coexisting ions increased firstly and then gradually decreased,and the breakthrough curve of coexisting ions presented a "overshoot"shape,which could be predicted well by gaussian equation.The results of EDX study showed that PA-SCB had the highest adsorption affinity for Pb²⁺,and competitively replaced the adsorbed coexisting ions of Cu²⁺,Cd²⁺,Zn²⁺and Ca²⁺in the adsorption process to achieve the highly selective adsorption of Pb²⁺.Wastewater treatment experiment showed that the amount of Pb²⁺adsorbed on the column was 0.36 mmol g^-1,while that of Cu²⁺,Cd²⁺,Zn²⁺,Ca²⁺and Mg²⁺was 0.069,0.006,0.007,0.005and 0.001 mmol g^-1,PA-SCB packed column could selectively adsorb and separate Pb²⁺from actual wastewater.?3?The adsorption of Cu²⁺,Pb²⁺,Pb²⁺,Cd²⁺,Zn²⁺,Ca²⁺and Mg²⁺in wastewater was studied by using amine-modified bagasse?AM-SCB?and phosphoric acid modified bagasse?PA-SCB?tandem packed column.The results of single column experiment showed that AM-SCB could selectively adsorb Cu²⁺,PA-SCB could selectively adsorb Pb²⁺,and tandem double column could simultaneously adsorb and separate Cu²⁺and Pb²⁺.Two tandem column experiments showed that amount of Cu²⁺,Pb²⁺,Cd²⁺,Zn²⁺,Ca²⁺and Mg²⁺adsorbed on AM-SCB was 0.17,0.003,0.001,0.006,0.013 and 0.009 mmol g^-1 and that on PA-SCB was 0.04,0.24,0.002,0.018,0.028 and 0.005 mmol g^-1,respectively.Tandem columns fixed with different modified biosorbent had great potential in multi-metal recovery.?4?Phosphoric acid modified magnetic bagasse was prepared by in-situ coprecipitation method.The mixed adsorbent single column with phosphoric acid modified magnetic bagasse and AM-SCB could effectively recover Cu²⁺and Pb²⁺in metallurgical wastewater.By magnetic separation,we could separate magnetic PA-SCB and AM-SCB.After regeneration,Cu²⁺solution and Pb²⁺solution,could be obtained respectively from AM-SCB and magnetic PA-SCB.