Study On The Remediation Of Cr⁶⁺ Contaminated Groundwater With Attapulgite Nano-iron Based Bimetallic Material PRB

In view of the current difficulties in removing Cr⁶⁺in groundwater and the lack of effective treatment technology,this study proposes a new perspective on the effective treatment of attapulgite-loaded nano-iron-based bimetallic materials.First,the experimental performance of Cr⁶⁺adsorption on single attapulgite was explored;then,based on the above research,nano-Fe/Ni and Fe/Cu bimetallic materials with different Ni and Cu conversion rates were prepared and their Cr⁶⁺treatment performance Conducted a comprehensive analysis.At the same time,the efficiency of removing Cr⁶⁺from iron filings,reduced iron powder and other materials was compared and analyzed through laboratory tests,and the best effect Cu rate was 3%nanometer Fe/Cu bimetallic material as the main material of the loading material.The load material was prepared for the reaction medium of the Permeable reactive barrier?PRB?device to treat the groundwater simulated by Cr⁶⁺pollution.Finally,the static conditions of the best conditions for the removal of Cr⁶⁺?dosage,reaction time,pH value,etc.?of attapulgite and nanomaterials are carried out,and the experimental research and comprehensive analysis are carried out from the aspects of microstructure,kinetics and thermodynamics The optimal conditions for the treatment of Cr⁶⁺contaminated groundwater by attapulgite loaded with nano-Fe/Cu bimetallic materials as permeable reactive wall fillers were determined.Research indicates:?1?The test uses attapulgite with structural support material as the main function as the test material.The test results show that it is used as a Cr⁶⁺treatment material in water,and the removal efficiency is poor.Under various modification methods,thermal modification purification has better treatment effect on Cr⁶⁺in water than other modification methods,and it can remove Cr⁶⁺in water with concentration of50mg/L under the condition of large dosage of 30g/L.The rate is only about 7%.The acid modification destroyed the regular octahedral structure of attapulgite,and the removal efficiency of Cr⁶⁺became poor.The effect is not great under the condition of thermal modification,and the ultrasonic 10min has a slight improvement on the removal rate.The increase of the dosage and the decrease of the pH of the environmental solution are both beneficial to increase the adsorption performance of attapulgite to Cr⁶⁺.The adsorption of attapulgite to Cr⁶⁺in water is mainly chemical adsorption,and the isothermal adsorption process is more in line with the theoretical model of monolayer adsorption.As a structural material,it has strong permeability and stable mechanical structure.?2?The removal effect of Cr⁶⁺in different media shows that:iron filings,reduced iron powder with particle size?200 mesh,nano-zero-valent iron,nano-Fe/Ni bimetal and nano-Fe/Cu bimetal sequentially increase the removal efficiency of Cr⁶⁺in water.Nano-Fe/Ni and Fe/Cu bimetallic materials are better for Cr⁶⁺treatment in water.Among them,nano-Fe/Cu bimetallic materials with a Cu rate of 3%are better than nano-Fe/Cu,Fe/Cu under other Cu and Ni rates The Ni bimetallic material has a higher removal rate of Cr⁶⁺in water,where the dosage of nano Fe/Cu bimetallic material with a Cu rate of 3%is 90 mg/L,and the concentration is 50 mg/L at 60 min in a neutral environment.The removal rate of Cr⁶⁺in the solution has reached 91.37%.Therefore,the experiment selected nano Fe/Cu bimetallic material with a Cu rate of3%as the main loading material.The test results of influencing factors show that the increase of the dosage of nano-Fe/Cu bimetallic materials and the decrease of Cr⁶⁺concentration and pH in the water are all conducive to the improvement of the removal efficiency of Cr⁶⁺.When the dosage is only 50mg/L,the environmental pH value When changing from 7 to 3,the removal rate of Cr⁶⁺increased from 69.96%to 77.82%at a reaction time of 60min.The reaction kinetics test results show that the nano-Fe/Cu bimetallic material with a Cu rate of 3%reacts with Cr⁶⁺in water at the fastest rate.The increase of the dosage and the decrease of Cr⁶⁺concentration and pH in water are all beneficial to nano-Fe/Cu The reaction rate of Cr⁶⁺in water increases with bimetallic materials.?3?Compared with the single nano bimetallic material,the removal efficiency of Cr⁶⁺by the loaded material is greatly increased.Compared with the single nano bimetallic material,the loaded material has some improvement in agglomeration phenomenon.Among the removal effects of solution Cr⁶⁺,attapulgite,the basic material used to load nano bimetallic material,has no obvious effect.When 200mg/L is added for 4h,the removal rate of solution Cr⁶⁺is only 0.12%,and the net amount of bimetallic is the same Under the condition of adding 100mg/L and 300mg/L nano bimetallic materials and loaded materials respectively,the removal rate of Cr⁶⁺in solution can reach 93.31%and 99.03%respectively when they react for 10min.The removal rate was 100%after 50 min reaction.The results show that the main reactant in the loading material is Fe/Cu bimetal material.The decrease of pH value is more beneficial to the removal of Cr⁶⁺from the solution.?4?In the PRB simulation dynamic response experiment,the response of loaded materials to simulated Cr⁶⁺polluted groundwater showed a downward trend as a whole.In terms of long-term effect,the removal effect of Cr⁶⁺under acidic condition is better than that under neutral condition.Under the condition of pH 3,the removal rate was still higher than 96.5%after 20 days of reaction.Under the condition of pH 7,the removal rate was also higher than 88%after 20 days of reaction.The removal rate of Cr⁶⁺in PRB column can be increased by reducing the flow rate.The optimum reaction condition is pH=3 and flow rate is 0.3ml/min.For the simulated Cr⁶⁺polluted groundwater at low flow rate,the treatment effect is good,and the treatment effect of16d can still meet the requirements of class III standard of groundwater quality standard.If we continue to improve the reaction efficiency,we can increase the quality of packing or the height of PRB reaction column.