Preparation Of Iron/carbon Matrix Composites And Their Purification Mechanism For Arsenic In Water

In recent years,arsenic pollution in water bodies around the world has become increasingly serious,and arsenic pollution in sedimentary groundwater has become a global health problem.Among arsenic and its compounds,As(Ⅲ)is more toxic than As(Ⅴ).Longterm exposure to arsenic pollution will cause serious harm to human beings,plants and animals.Iron based materials are widely used in many fields such as adsorption,photocatalysis,magnetic coatings and nanoelectrodes because of their wide sources,low cost and environmental friendliness.This paper focused on how to deal with arsenic pollution in water,studied the preparation of a new type of iron/carbon matrix composite,and explored the morphology composition,photoelectric performance and adsorption and photocatalytic oxidation of As(Ⅲ)in water of the new type of iron/carbon matrix composite.The main study contents and results of this paper are as follows:(1)Using FeSO4·7H2O as raw material and hydrothermal carbon(HTC)as carrier,the adsorbent α-FeOOH@HTC was prepared by hydrothermal method and chemical deposition method.The adsorption behavior of α-FeOOH@HTC on arsenate As(Ⅲ)under the influence of phosphate was investigated.The morphology and structure of α-FeOOH@HTC were characterized by X-ray diffraction(XRD),Scanning electron microscopy(SEM)and Transmission electron microscopy(TEM).The results show that α-FeOOH is successfully modified on the surface of HTC,and α-FeOOH@HTC is clearly a core-shell structure.The three adsorbents were applied to the adsorption of As(Ⅲ).The results showed that the adsorption rate of As(Ⅲ)was α-FeOOH@HTC>α-FeOOH>HTC.By fitting the adsorption kinetics model,α-FeOOH@HTC and α-FeOOHare chemical adsorption,and HTC is physical adsorption.In addition,α-FeOOH@HTC(10.78 mg·g-1)has the highest adsorption capacity for As(Ⅲ)at pH=9.The adsorption capacity of α-FeOOH@HTC for As(Ⅲ)was investigated under the influence of different phosphate species.The adsorption capacity of α-FeOOH@HTC(9.87 mg·g-1)for As(Ⅲ)was the highest under the influence of PO43-.The competitive adsorption size of the three phosphates for As(Ⅲ)was H2PO4->HPO42->PO43-,and the adsorption capacity of α-FeOOH@HTC for As(Ⅲ)was different under the influence of different concentrations of phosphate(H2PO4-).When the concentration of H2PO4-is greater than 15 mg,the adsorption capacity of α-FeOOH@HTC for As(Ⅲ)decreased obviously(2.75 mg·g-1).The X-ray photoelectron spectroscopy(XPS)and Fourier transform infrared spectroscopy(FT-IR)analysis showed that the characteristic peak of As element appeared in the XPS spectra after the reaction,and α-FeOOH@HTC was chemically combined with As(Ⅲ).This work attempts to provide a theoretical basis for reducing arsenic pollution in farmland through the interaction principle of P/As,which has potential practical application value.(2)Based on the hydrothermal growth of CdZn-OH@FeOOH on Carbon Cloth(CC),the curing conditions were controlled according to the different solubility product constants(Ksp)of Cd(Ⅱ),Zn(Ⅱ)and Fe(Ⅲ)-OH,and the interface synthesis matrix CZS@FeOOH@CC was successfully constructed by selective S2-anion exchange.It is also used for photocatalytic oxidation of As(Ⅲ).XRD,SEM and TEM showed that CZS@FeOOH@CC photocatalyst was successfully synthesized.The transient fluorescence spectroscopy(PL),Electrochemical impedance spectroscopy(EIS)and Photocurrent data showed that the introduction of CdZnS can inhibit the recombination rate of photogenerated electrons and holes.CZS@FeOOH@CC has absolute advantages in charge transfer and electron hole pair separation.The photocatalytic experiment results showed that CZS@FeOOH@CC completely degraded 10 mg·L-1 As(Ⅲ)within 10 min under visible light irradiation.The influence factors of CZS@FeOOH@CC composites on the catalytic oxidation of As(Ⅲ)were studied in oxalate system:The photocatalytic oxidation efficiency of As(Ⅲ)was affected by the concentration of oxalate in the system,and the atmosphere played a major role in the photocatalytic oxidation of As(Ⅲ).The mechanism of CZS@FeOOH@CC photocatalytic oxidation of As(Ⅲ)was revealed by experiments of EPR and free radical capture.Under visible light,the oxalate first combines with Fe(Ⅲ)on the surface of FeOOH to form an Fe(Ⅲ)-oxalate complex,which is then activated under visible light to form the Fe(Ⅲ)-oxalate complex to·C2O4-.In the presence of oxygen,Fe(Ⅱ)is easily oxidized to Fe(Ⅲ)by reacting with O2,and the introduction of CdZnS promotes the separation of interfacial electron holes and accelerates the REDOX cycle of Fe(Ⅱ)/Fe(Ⅲ).This research provides a feasible and simple method for promoting arsenic pollution in wastewater by photocatalytic oxidation of iron-based materials.