Preparation Of Nanoscale Zero-Valent Iron Supported By Straw And Its Removal Performance Of Antibiotics And Heavy Metals

Heavy metals are highly toxic and easy to enrich,but difficult to be biodegraded.Heavy metals can cause serious harm to human beings and the ecological environment even at low concentrations.In addition,antibiotic contamination also occurs frequently in water environment due to the extensive use of antibiotics.Therefore,exploring the removal of antibiotics and heavy metal pollutants in water environment has become one of the current research hotspots.Nano-zero-valent iron(NZVI)has many advantages as a new environmental remediation material,such as large specific surface area,high reactivity and strong reduction ability.And it is widely used in environmental remediation.However,NZVI is easy to oxidize and lose its activity in air and water.Moreover,NZVI particles are easy to agglomerate due to its magnetism,which limits their application in practical application.In order to make it better used in environmental pollution remediation,people try to improve the disadvantage of easy agglomeration and oxidation through modification.In this paper,wheat straw was used as carrier to modify NZVI,which can reduce the agglomeration of NZVI.And wheat straw supported Nanoscale Zero-valent Iron(WS-NZVI)was prepared in this experiment.Ciprofloxacin(CIP),chlorotetracycline(CTC)and copper(Cu2+)were selected as the target pollutants.The removal performance of WS-NZVI for the three pollutants and the feasibility of simultaneous removal of CTC and Cu2+ were investigated.The pollutants removal mechanisms were also preliminarily explored.The main research contents and results are as follows:NZVI and WS-NZVI were prepared by liquid phase reduction method,and a series of characterizations of straw,NZVI and WS-NZVI were carried out,including scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction and X-ray photoelectron spectroscopy.The characterization results show that the main form of iron in the NZVI and WS-NZVI prepared in this experiment is Fe0,and the NZVI in WS-NZVI material is successfully loaded on straw.They also illustrate that the agglomeration of NZVI is obviously reduced,and the dispersion of NZVI is improved.The effects of straw,NZVI and WS-NZVI on the removal of CIP and CTC were investigated,also the effects of WS-NZVI on the removal of Cu2+.The results showed that the removal efficiency of CIP and CTC by the three materials followed the order of WS-NZVI>NZVI>straw.The removal efficiency decreases with the increase of initial CIP and CTC concentration at 25?,but the removal rate increases gradually.The maximum removal rate of CIP by WS-NZVI can reach 363.63 mg/g,and the maximum removal rate of CTC can reach 1280.8 mg/g.The increase of WS-NZVI dosage contributes to the increase of removal efficiency of CIP and CTC.The effect of solution pH on the removal efficiency of CIP and CTC showed that the removal efficiency first increased and then decreased with the gradual increase of pH.The removal efficiency was the best under neutral partial acid condition.WS-NZVI has a good effect on the removal of Cu2+ alone,and the reaction can reach a balance within 30 minutes.The maximum removal of Cu2+ by WS-NZVI was 376.4 mg/g.The higher the initial pH of the solution,the better the removal effect.The feasibility of simultaneous removal of CTC and Cu2+ pollutants by WS-NZVI was explored,and the interaction between the two pollutants in the removal process was explored.The results show that WS-NZVI can remove both CTC and Cu2+pollutants simultaneously.The presence of CTC inhibited the removal of Cu2+ and the presence of Cu2+ promoted the removal of CTC at low concentration and high concentration.The products of WS-NZVI removal of three pollutants were analyzed based on mass spectrometry(MS)and XPS,and the mechanism of WS-NZVI removal of pollutants was preliminarily discussed.The experimental results show that the removal of pollutants by WS-NZVI includes redox removal and adsorption removal.This study proved that straw as NZVI carrier is feasible.And the WS-NZVI prepared has good removal effect on CIP,CTC and Cu2+.It can be used to remove both CTC and Cu2+.Consequently,the study provides an effective alternative material for the treatment of wastewater polluted by antibiotics and heavy metals.