Selective Adsorption Behaviour And Mechanism Of Cu²⁺ On Modified Biosorbent

Heavy metal wastewater,especially copper-containing wasterwater,to bodies of water can seriously threaten the environment,and treatment it allows of no delay.In many treatment methods,biosorption method by using agriculture waste such as bagasse as adsorbent has attracted much attention due to it rich source,simple operation,and low processing cost.China is a agricultural country with an annual output of 234 million tons of bagasse,but the majority of it was treated as solid waster.Thus,developing a new approach for the comprehensive utilization of bagasse is necessaried.Based on the above objectives,the modified bagasse with high selectivity to Cu²⁺was prepared in this thesis.The selective adsorption behavior and mechanism of modified bagasse on copper ions was investigated.Based on this,an acid-leaching biosorption combination method was used to extract and separate the copper from the metallurgical sludge.The results are as follows:?1?SEM,FTIR,EDX and Zeta potential were used to characterization the unmodified and modified SCB,results showed that the TEPA was successfully grafted on the surface of SCB.The maximum adsorption capacity of bagasse for Cu²⁺increased from 0.128 to 0.469 mmol g^-1 after the modification,increased about 3.7 times.The adsorption of Cu²⁺on modified bagasse can fitted well by langmuir and pseudo-second-order kinetics model,the adsorption process was observed to be monolayer adsorption and coordination adsorption was the main adsorption mode.?2?The effects of coexisting ions:Pb²⁺,Cd²⁺and Ca²⁺on the adsorption of Cu²⁺were investigated under dynamic conditions,results showed that when the concentration of:increased from 1:1 to 1:100,in Cu/Pb system,the adsorption capacity of Cu²⁺on modified SCB fixed bed column were 0.190,0.210 and 0.200 mmol g^-1,while that of Ca²⁺were lower than 0.009 mmol g^-1.In Cu/Cd system,the adsorption capacity of Cu²⁺were 0.227,0.249,0.245 and 0.253 mmol g^-1,while that of Cd²⁺were lower than 0.03 mmol g^-1.In Cu/Ca system,the adsorption capacity of Cu²⁺were 0.221,0.252,0.257,0.265,0.233 and 0.235 mmol g^-1,while that of Ca²⁺were lower than 0.002 mmol g^-1.Based on the above results,the treatment effect of the copper-containing wastewater was investigated,results showed that the column could selectively separate copper from copper-containing wastewater.?3?Different systems have different adsorption mechanism.In Cu-Pb and Cu-Cd system,the breakthrough curve of Pb²⁺and Cd²⁺shows obviously overshoot,indicated that the two coexisting ion was replaced by Cu²⁺when the active sites on the adsorbent decreased gradually during the adsorption process,which resulted in the selectively adsorption of Cu²⁺.In Cu-Ca system,the breakthrough curve of Ca²⁺shows inverted"L",showed that the adsorbent has weak adsorption affinity and low adsorption capacity to Ca²⁺,which shows little interference with Cu²⁺adsorption.?4?Separation and recovery of copper in metallurgical sludge by using acid leaching-biosorption combined method.Firstly,the copper in the sludge was leached by nitric acid.Than,the obtained leachate was pumped into the modified SCB fixed bed column after removal of iron to achieve selectively adsorption and separation of Cu²⁺.Results showed that the leaching rates of HNO₃ for Cu and other metals Mg,Ca,Zn,Fe,Cd,Pb,K,and Cr in metallurgical sludge were 96.9,51.2,94.8,91.0,53.5,87.8,41.4,8.8 and 97.5%,respectively.The adsorption capacity of Cu²⁺is 0.261mmol g^-1,while that of other metal ions is less than 0.0300 mmol g^-1.The above results showed that the acid-leaching-biosorption combination method can effectively separate and recover of copper from metallurgical sludge or other solid waster.