Removal Of Typical Contaminant In Water By Green Synthetic Iron-based Materials

Recent years,nano-materials such as nano-iron and graphene have been widely used as adsorbents for the treatment of heavy metals and organic contaminants in water environment due to their high specific surface area,high adsorption capacity and good chemical stability.However,the chemicals used in the traditional synthesis of nano-iron and graphene were not only expensive,but also prone to secondary pollution.In this study,green tea extract was used to prepare nano-iron(Fe NPs)and graphene loaded nano-iron-nickel composite materials(RGO-Fe/Ni),which were easy to operate,environmental friendly and low cost,and Fe NPs and RGO-Fe/Ni were used to remediation Pb(?),rifampin and antimony in the water environment.In this study,the effects of various experimental conditions on the adsorption of Pb(?)and rifampin by Fe NPs were investigated by changing the dosage of Fe NPs,the initial concentration of the contaminant,the reaction temperature and p H.From the characterization results of SEM and TEM,it can be seen that the particle size distribution of Fe NPs is between 30-100 nm.Combining with the characterization results of EDS,XRD,FT-IR and XPS,confirmed that Pb(?)and rifampin were successfully adsorbed on Fe NPs.The fitting results of the experimental data showed that the adsorption process of Pb(?)and rifampin by Fe NPs followed pseudo-second-order kinetics,was a rate control step based on chemical adsorption,and was a spontaneous endothermic process.Among them,the adsorption of Pb(?)by Fe NPs conforms to the Langmuir-type isotherm,while the adsorption of rifampin conforms to the Freundlich-type isotherm.Based on the above results,we deduced the removal mechanism of Fe NPs for Pb(?)and rifampin.At the same time,after 5 times of recycling,the removal efficiency of Fe NPs for Pb(?)and rifampin decreased from 98.76% and 78.21% to 52.33 % and 64.86 %,and the removal efficiency of Pb(?)and rifampin in wastewater was 97.48 % and 68.83 %,respectively.Based on the previous research,this study used green tea extract to synthesize graphene loaded nano-iron-nickel composite materials in one-step which was applied to the removal of Sb(?)contaminant in water environment.The removal performance of RGO-Fe/Ni on Sb(?)was investigated by changing the dosage of RGO-Fe/Ni,the initial concentration of Sb(?),the reaction temperature and p H.The experimental results showed that under the best experimental conditions,the removal efficiency of Sb(?)by RGO-Fe/Ni can reach 71.71 %.And after 5 times of recycling,the removal efficiency decreased from 64.30 % to 44.92 %.In addition,RGO-Fe/Ni removed 95.72 % of Sb(?)contaminant in groundwater.Characterization of RGO-Fe/Ni before and after reaction by SEM-EDS,XPS,XRD and other characterization methods,the results showed that RGO-Fe/Ni successfully removed Sb(?)contaminant in aqueous solution,and during the process of adsorption,it was accompanied by the occurrence of oxidation reaction,which oxidized Sb(?)to Sb(V),reducing the toxicity of antimony.The experimental data were fitted with kinetic and thermodynamic models,and the fitting results proved that the process of RGO-Fe/Ni adsorption of Sb(?)conforms to the Langmuir-type isothermal,which is an adsorption process mainly based on monolayer adsorption,and the process belongs to spontaneous heat absorption.At the same time,the adsorption process also conforms to the pseudo-second-order kinetics,which was a rate control step based on chemical adsorption.Antimony usually existed in the form of Sb(?)and Sb(V)in the water environment.Based on the previous research results,RGO-Fe/Ni was used to remove Sb(?)and Sb(V)compound contaminants in the aqueous solution,and further research on the RGO-Fe/Ni removal performance of antimony contaminant.Under the optimal experimental conditions,the removal efficiency of RGO-Fe/Ni to Sb(?)and Sb(V)reached 78.39 %and 53.16 %,respectively.The fitting results of the experimental data show that the adsorption process of Sb(?)and Sb(V)by RGO-Fe/Ni was consistent with Langmuir-type isotherm,and followed pseudo-second-order kinetics,which was mainly a chemical adsorption process.In summary,the Fe NPs and RGO-Fe/Ni materials synthesized using green tea extract have good removal efficiency for Pb(?),rifampin and antimony contaminants in the water environment,which were expected to be applied to the treatment of contaminant in wastewater.