Preparation Of Amino Acid-Fe₃O₄ Composite Nanomaterials And Its Application In Removal Of Heavy Metals In Water

Heavy metal pollution in water body is one of the most serious environmental problems in today's world.Removal of various micro-trace heavy metal ions in water body and regeneration performance of separation and recovery of adsorbent materials with a variety of trace heavy metal ions in the water at the same time have plagued scientists and researchers.This subject aims to improve the corrosion resistance of adsorbent materials and simultaneous removal of multiple types of heavy metal ions.It uses silicon dioxide to wrap magnetic materials and bonds cysteine or chitosan to obtain magnetic composite adsorbent materials.The adsorption properties of heavy metal ions on materials were studied systematically to obtain good dispersion and corrosion resistance.The adsorbed materials can be used repeatedly to remove heavy metal ions from water bodies.The specific work is divided into the following four parts:?1?Fe₃O₄@SiO₂-NH₂ was synthesized by the modification of Fe₃O₄ particles with tetraethylorthosilicate and 3-aminopropyltriethoxysilane,and glutaraldehyde was used as a crosslinking agent to prepare Fe₃O₄@SiO₂-L-Cys by grafting cysteine.The orthogonal experiment was designed to investigate the six factors such as pH,glutaraldehyde dosage,and the feed ratio of Fe₃O₄@SiO₂-NH₂ and cysteine?Fe:cys/m:m?,time,temperature,the ratio of ethanol to water?m:m?on the adsorption of Pb?II?,and the FTIR,XRD,TEM,and MPMS were used to characterize the material.The results showed that the factors that affect the effect of Pb?II?on the adsorption rate of the synthetic material were from the main sequence to the pH>Fe:cys>Time>Glutaraldehyde dosage>Temperature>Ethanol:Water ratio,each factor had no interaction.The adsorption rate was at it's highest when pH was 9,the feed ratio was 1:1.5,the amount of glutaraldehyde was 1 mL,the reaction time was 14 hours,the temperature was55°C,and the adsorption ratio of ethanol and water was 1:0.The Fe₃O₄@SiO₂-L-Cys material had a superparamagnetic property when the materialhad a particle size of 150²00 nm and a saturation magnetization equaled to about 87.36 emu/g.?2?Fe₃O₄@SiO₂-L-Cys was used as adsorbent and Pb?II?as the adsorbent,the factors affected adsorption rate of Pb?II?such as ambient temperature,adsorption time,initial concentration of Pb?II?and solution pH ware investigated.Themechanism of adsorption and material regeneration performance ware investigated.The results showed that the adsorption rate of Pb?II?in water reached to 98.25%when the amount of adsorbent was 0.4 mg/L,temperature was 303 K,adsorption time was 2.5 h,pH was 5.02.The adsorption kinetics of Pb?II?on the material accorded with Lagergren quasi-second order kinetic equation and belonged to chemical adsorption process.Adsorption isotherm study showed that the adsorption of Pb?II?on the material conformed to the Langmuir isotherm model.The adsorption capacity of Pb?II?for molecular layer adsorption was 120.8mg/g.Adsorption thermodynamic studies showed that the whole system was an endothermic reaction,and the heating was conducive to the adsorption,and the process could be carried out spontaneously.The adsorption cycle was recycled 4 times After that,the adsorption rate still reached to92.7%.?3?Fe₃O₄@SiO₂-L-Cys was used as adsorbent,Multicomponent mixed metal ions Pb?II?,Ni?II?,Cu?II?,and Cd?II?in water were used as adsorbents,and the environmental temperature and adsorption time were investigated.The influence of the initial concentration of the mixed metal ions and the pH value of the solution on the adsorption rate of Pb?II??Ni?II??Cu?II??Cd?II?were discussed.The adsorption mechanism and the regeneration performance of the material were discussed.The results showed that the material was mixed with metal ions Pb?II?,Ni?II?.The adsorption kinetics of Cu?II?and Cd?II?were all consistent with the Lagergren quasi-second order kinetics equation.Adsorption belonged to the chemical adsorption process.Adsorption isotherm study showed that the adsorption of Pb?II?,Ni?II?,Cu?II?,and Cd?II?by Fe₃O₄@SiO₂-L-Cys conformed to the Freundlich adsorption model,and the adsorption was a heterogeneous adsorption process.Adsorption thermodynamic studies showed that the whole system was an endothermic reaction.The adsorption process of Pb?II?,Ni?II?,Cu?II?and Cd?II?by Fe₃O₄@SiO₂-L-Cys was an endothermic reaction.The progress of adsorption was an entropy increasing process that can proceeded spontaneously.?4?Fe₃O₄@SiO₂-CS was prepared by grafting chitosan with Fe₃O₄@SiO₂-NH₂ as carrier and glutaraldehyde as cross-linker.The material was characterized by XRD,FTIR and TEM.The selective adsorption of mixed metal ions Pb?II?,Ni?II?,Cu?II?,and Cd?II?was investigated.The adsorption performance of the material to single Pb?II?and the regeneration performance of the material were studied.The effects of temperature,time,initial concentration of Pb?II?and pH value on the adsorption rate of Pb?II?were investigated.The results showed that Fe₃O₄@SiO₂-CS is highly selective to a single Pb?II?.The adsorption kinetics of Pb?II?on the material conformed to the Lagergren quasi-second order kinetics equation and belonged to the chemical adsorption process.Adsorption isotherm studies have showed that the adsorption of Pb?II?on the material conforms to the Langmuir isotherm model and is monolayer adsorption.The maximum adsorption capacity for Pb?II?is260.4mg/g.Adsorption thermodynamic studies showed that the entire system was an endothermic reaction,and warming was conducive to the adsorption,and the process can be carried out spontaneously.After three cycles of adsorbent recycling,the adsorption rate still reached 82.3%,which can be recycled for adsorption of Pb?II?.