Removal Of P-chlorophenol In Water By Supported Nano-zero-valent Iron Fenton-like Method

P-chlorophenol（4-CP）is discharged into the environment with waste water such as printing and dyeing,papermaking,medicine and pesticides,thereby contaminating water bodies.4-CP has highly toxic and has carcinogenic,teratogenic and mutagenic effects,which seriously endangers the environment and human health.Aromatic ring structure of 4-CP makes it extremely stable in the environment and difficult to be biodegraded.The Fenton method has attracted widespread attention due to its extremely oxidizing properties,its ability to oxidize almost all organics,and its simplicity and efficiency.However,the Fenton method has the problems of requiring the pH of the reaction system to be maintained acidic conditions,large iron salt consumption and large iron sludge production.To solve these problem,it is proposed to study a kind of composite material like Fenton method of loading nZVI with ferric oxide to remove 4-CP in water.In this study,Fe₃O₄ was first prepared by co-precipitation method,and then the prepared n ZVI was supported on the surface of Fe₃O₄ by liquid phase reduction method to prepare Fe₃O₄-nZVI conforming materials.Fe₃O₄-nZVI was characterized by SEM and EDS.The effect of Fe₃O₄-nZVI Fenton-like method to remove 4-CP in water was studied through batch equilibrium experiments.Effects of initial pH,the initial concentration of 4-CP,the amount of Fe₃O₄-nZVI composite material dosage,the molar ratio of nZVI to Fe₃O₄,temperature,concentration of H₂O₂,Ca²⁺ion concentration,Mg²⁺ion concentration,Cu²⁺ion concentration and Fe₃O₄-nZVI composite reuse times on 4-CP removal rate were studied.According to the batch equilibrium experimental data,the design of three factors and five levels was optimized by the star point design（CCD）method in the response surface method（RSM）to optimize the experimental data.The effects of the interactions of Fe₃O₄-nZVI dosage,4-CP concentration and hydrogen on the removal of 4-CP by Fe₃O₄-nZVI Fenton-like method were studied.Then the optimal experimental conditions were obtained.The main conclusions were shown as follows:（1）The SEM results show that the Fe₃O₄-nZVI composite material is nano-scale,and the composite material is uniformly distributed in a chain shape.The particle size of Fe₃O₄-nZVI composite material is basically between 50-200nm.The Fe₃O₄-nZVI composite has a core-shell structure,the core is Fe₃O₄,and the shell is nZVI.Fe₃O₄-nZVI composites are mainly composed of Fe and O elements.During the preparation of Fe₃O₄-n ZVI composites,they will be subjected to different degrees of oxidation.Fe₃O₄-nZVI nanomaterials is easy for magnetic separation.（2）The order of 4-CP removal rate by different materials is as follows:nZVI+H₂O₂+Fe₃O₄>nZVI+Fe₃O₄>nZVI+H₂O₂>H₂O₂+Fe₃O₄>nZVI>Fe₃O₄>H₂O₂,nZVI+H₂O₂+Fe₃O₄ has reached the highest romaval rate.The removal rate of4-CP in water by Fe₃O₄-nZVI Fenton-like method decreases with increasing pH,Ca²⁺ion concentration,Mg²⁺ion concentration,and 4-CP initial concentration.As the reaction temperature and Fe₃O₄-nZVI dosage increase,removal rate of 4-CP in water by Fe₃O₄-nZVI Fenton-like method increases.The removal rate of 4-CP by Fe₃O₄-nZVI-based Fenton method increases with the increase of the temperature and the amount of Fe₃O₄-nZVI dosage.（3）When the H₂O₂ concentration is low,the removal rate of 4-CP by the Fe₃O₄-nZVI Fenton-like method increases with the increase of H₂O₂ concentration.When the H₂O₂ concentration exceeds a certain value（10 mmol/L）,the removal rate decreases with increasing H₂O₂ concentration.When the molar ratio of Fe₃O₄ to nZVI is 1:1,the removal rate of 4-CP is the highest;when the molar ratio of Fe₃O₄ to nZVI is greater than or less than 1,it is not conducive to the reaction,and the removal rate of 4-CP decreases.Fe₃O₄-nZVI is easy to be magnetically separated.The loss of iron ions during the reuse process leads to a reduction in its removal rate.When reused 5times and 10 times,the removal rates of 4-CP were 78.56%and 62.13%,respectively.（4）According to the results of RSM analysis,the second-order model is suitable for removing 4-CP from the Fenton-like method of Fe₃O₄-nZVI.The analysis of variance:P value of the model is less than 0.0001,and the P value of the residual error is 0.2002>0.05.R-Squared（model determination coefficient）=0.9485,Adj R-Squared（corrected model coefficient）=0.9022,Adeq Precision=15.762>4.0,indicating that the model is significant,and the correlation between actual and experimental values is high.RSM method can optimize Fe₃O₄-nZVI Fenton-like method removes 4-CP.The effect of the amount of Fe₃O₄-nZVI dosage,the initial concentration of 4-CP,and the concentration of H₂O₂ on the removal rate of 4-CP is significant.The percentage of the contribution of the three influence factors to the removal of 4-CP is in the order of Fe₃O₄-nZVI dosage>4-CP initial concentration>H₂O₂ concentration.Experimental conditions for optimal removal rate of 4-CP:Fe₃O₄-nZVI dosage（X₁）1.0 g/L,4-CP initial concentration（X₂）63.4mg/L,H₂O₂concentration（X₃）11.6 mmol/L;The predicted removal rate and actual removal rate were 100%and 97.85%,respectively,with a deviation of 2.15%.