| The large amount of copper-containing metallurgical sludge produced in the process of copper smelting is not only a renewable resource,but also a heavy metal pollution source.If not properly disposed of,it is not only a waste of resources,but also cause serious pollution to the surrounding water and soil.Acid leaching could efficiently extract copper from metallurgical sludge,but it is difficult to separate and recovery copper due to the complex composition of leaching solution.In this paper,three kinds of copper（Ⅱ）ion-imprinted bagasse adsorbents with high selectivity were prepared from waste biomass:aminoguanidine modified copper（Ⅱ）ion-imprinted bagasse,tetraethylenepentamine modified copper（Ⅱ）ion-imprinted bagasse,polyethyleneimine modified copper（Ⅱ）ion-imprinted bagasse.The effects of initial solution concentration,p H,adsorption time and co-ions on Cu（Ⅱ）adsorption by the three copper（Ⅱ）ion-imprinted bagasse were investigated.The selective adsorption property and mechanism of adsorbents for Cu（Ⅱ）in leaching solution of metallurgical sludge were investigated.The main research contents are as follows:（1）Using nitric acid as leaching agent to leach copper from metallurgical sludge,the effects of nitric acid concentrations and leaching time on copper leaching efficiency were studied.The results showed that leaching progress of metal ions could reach equilibrium within 20 minutes using 0.5 mol L-1nitric acid solution,and the leaching efficiency of Cu（Ⅱ）,Zn（Ⅱ）,Ca（Ⅱ）,Mg（Ⅱ）and Cr（ⅡI）were 91.4,99.0,99.5,90.3 and 76.3%,respectively.（2）Aminoguanidine modified copper（Ⅱ）ion-imprinted bagasse was prepared with bagasse as raw material and aminoguanidine hydrochloride as amine modifying agent through imprinting and cross-linking process.The results of batch adsorption experiments showed that the maximum adsorption capacity of Cu（Ⅱ）on amineguanidine modified copper（Ⅱ）ion-imprinted bagasse was 23.01 mg g-1,and the adsorption effect was the best at p H=4.The adsorption process was in accordance with Langmuir isotherm adsorption model and pseudo-second-order kinetic model.The results of selective adsorption experiments showed that the aminoguanidine modified copper（Ⅱ）ion-imprinted bagasse had good adsorption selectivity for Cu（Ⅱ）in the presence of competitive ions of Zn（Ⅱ）,Cd（Ⅱ）,Mg（Ⅱ）,Ca（Ⅱ）and Pb（Ⅱ）.In addition,aminoguanidine modified copper（Ⅱ）ion-imprinted bagasse can also specifically recognize and bind Cu（Ⅱ）in leaching solution of metallurgical sludge.（3）The tetraethylenepentamine modified copper（Ⅱ）ion-imprinted bagasse was prepared by grafting tetraethylenepentamine onto the surface of bagasse via epichlorohydrin,and using Cu（Ⅱ）as template ion and glutaraldehyde as crosslinking agent.SEM,FTIR,EDS and zeta potential showed that the amine group was successfully grafted onto the surface of bagasse.The adsorption capacity of Cu（Ⅱ）onto tetraethylenepentamine modified copper（Ⅱ）ion-imprinted bagasse was 31.92mg g-1,and the adsorption could reach equilibrium within 40 min.The adsorption process was in accordance with Langmuir isotherm adsorption model and pseudo-second-order kinetic model.The adsorbent could selectively adsorb Cu（Ⅱ）in the presence of interfering ions with high concentration.After five consecutive adsorption and desorption cycles,the adsorption capacity does not decrease obviously,showing that the adsorbent has good reusability.Besides,the tetraethylenepentamine modified copper（Ⅱ）ion-imprinted bagasse could selectively adsorb and separate Cu（Ⅱ）from acid leaching solution of metallurgical sludge.（4）The polyethyleneimine modified copper（Ⅱ）ion-imprinted bagasse was prepared by grafting polyethyleneimine onto the surface of bagasse via epichlorohydrin,and using Cu（Ⅱ）as template ion and glutaraldehyde as crosslinking agent.The results of batch adsorption experiments showed that the maximum adsorption capacity of Cu（Ⅱ）is 36.89 mg g-1,and the adsorption process accords with Langmuir isotherm adsorption model and pseudo-second-order kinetic model.The adsorption capacities of polyethyleneimine modified copper（Ⅱ）ion-imprinted and non-imprinted bagasse were the best at p H=4,and the adsorption capacity of the former was higher than that of the latter under different p H conditions.This is because that during the preparation of the non-imprinted bagasse,more Schiff base reactions occurred between glutaraldehyde and primary amine on the surface of the bagasse,resulting in a decrease of-NH2on the surface of bagasse,thus reducing the number of active adsorption sites for Cu（Ⅱ）.Polythyleneimine modified copper（Ⅱ）ion-imprinted bagasse has a large number of imprinted cavities that are complementary to the size,shape and geometry structure of Cu（Ⅱ）,which makes the material could specifically recognize and bind Cu（Ⅱ）in the presence of competitive ions,and could also selectively adsorb and separate Cu（Ⅱ）from acid leaching solution of metallurgical sludge.In conclusion,the adsorption property and mechanism of aminoguanidine modified copper（Ⅱ）ion-imprinted bagasse,tetraethylenepentamine modified copper（Ⅱ）ion-imprinted bagasse and polyethyleneimine modified copper（Ⅱ）ion-imprinted bagasse were discussed,indicating that the three adsorbents all have good selectivity towards Cu（Ⅱ）and excellent reusability.However,in terms of adsorption capacity and selectivity towards Cu（Ⅱ）,the tetraethylenepentamine modified copper（Ⅱ）ion-imprinted bagasse has stronger potential for practical application,and the effective separation and recovery of Cu（Ⅱ）from metallurgical sludge can be achieved by the combination of acid leaching and adsoption process. |
