Preparation Of L-cysteine Modified Fe₃O₄ Magnetic Nanoparticles Combined With Eggshell And Its Application In Cu???,Ni??? Removal

Cu and Ni are two common precious metals.The ions of the two are complex and most of them have associated elements.They can only change forms or be transferred,diluted and accumulated,but they are difficult to degrade.Thus,they have brought potential risks and enormous pressure to human health and ecological environment.Therefore,reducing the concentration of heavy metals and recovering heavy metals in wastewater has become an important point and key point of heavy metal wastewater treatment.L-cysteine contains a large number of carboxyl groups?-COOH?,amino?-NH₂?and sulfhydryl groups?-SH?.These groups are easily complexed with metal ions.But it is very soluble in water and is not conducive to the recovery of pollutants.Eggshell?ES?is a kind of biological waste,which has a large specific surface area and excellent adsorption properties,and has potential as an environmental adsorption material.Using egg shell as the carrier,the magnetic nano iron oxide?Fe₃O₄?was synthesized in situ,and L-cysteine was modified to prepare L-cysteine modified magnetic eggshell?Cys-Fe₃O₄-ES?.In order to remove the heavy metal and realize the recovery and utilization of the adsorbent after the reaction,a kind of egg shell capital was provided.The means for the use of the source.In this study,the effects of egg shell pretreatment,egg shell particle size,mixture ratio of iron oxide and eggshell,L-cysteine concentration and stirring time on the synthesis were investigated.At the same time,the effects of Cys-Fe₃O₄-ES on the removal of target pollutants were studied under the conditions of the dosage,initial concentration of the solution,the reaction temperature,the initial pH of the solution,and the coexistence of Cu and Ni ions,and the mechanism and kinetics of the removal of Cu²⁺and Ni²⁺by Cys-Fe₃O₄-ES were preliminarily investigated.The main conclusions are as follows:?1?The optimum preparation parameters of Cys-Fe₃O₄-ES are:the size of eggshell is 200 mesh,the proportion of nano iron oxide and eggshell powder is 1:6,the concentration of L-cysteine is 2%,and the stirring time is 5 h.?2?Under the better preparation parameters,the batch experiment shows that increasing the dosage of Cys-Fe3O4-ES and increasing the reaction temperature can effectively speed up the reaction rate,but increasing the amount of Cys-Fe3O4-ES does not significantly increase the adsorption capacity of Cys-Fe₃O₄-ES.The increase temperature has no obvious effect on the final removal efficiency of Cu and Ni ions,and the removal rate is up to 100%,but it can shorten the time required for the reaction equilibrium.In the mixed solution of Cu and Ni ions,the effect of Cys-Fe₃O₄-ES on the efficiency of Ni ion removal is very large with the increase of the dosage of Cu and Ni ions,but there is no obvious effect on Cu.Influence.That is to say,under the same concentration and the same dosage,the adsorption effect of Cys-Fe3O4-ES on heavy metal Cu in water is better than that in Ni.?3?The fitting results of adsorption isotherm show that the fitting degree of Langmuir isotherm model to Cu and Ni ions is 0.7428 and 0.7471 respectively,and the correlation degree is not ideal,which indicates that the adsorption behavior of Cu and Ni ions is not simple single layer physical adsorption.The fitting degree of Freundlich and Generalized models is greater than 0.93,which can be used to describe the adsorption process positively.The kinetic process analysis shows that the adsorption of Cys-Fe3O4-ES on the adsorption of Cu and Ni ions in water accords with the quasi two order kinetic model,indicating that Cys-Fe3O4-ES removal of Cu and Ni ions is mainly chemical adsorption.?4?The removal of Cu and Ni ions by Cys-Fe₃O₄-ES is the result of adsorption and chelation.The results of SEM characterization show that the surface morphology of Cys-Fe3O4-ES changes obviously after the reaction of Cu and Ni ions:many crystals are formed on the surface of the material after the reaction with Cu ion,and the surface of the material becomes dense and irregular after the reaction with the Ni ion.The results of FT-IR characterization showed that Cu and Ni ions were chelated with-SH,-NH₂ and COO-in L-cysteine,and the reaction products might be CuS,NiS,COO-Cu²⁺,COO-Ni²⁺,NH₂-Cu²⁺and NH₂-Ni²⁺.