Treatment Of Heavy Metals From Wastewater By Complexation-ultrafiltration Using Modified Palygorskite

With the acceleration of industrialization,heavy metal pollution has become one of the most serious pollution threatening human health and environment.With the development of ecological civilization,heavy metal wastewater treatment has become a heat topic.The complexation-ultrafiltration process has a good effect on the treatment of heavy metal wastewater,with low energy consumption,less secondary pollution and simple operation.The treatment effect meets the increasingly strict requirements of environmental regulations and has a broad application prospect.In this study,the process of complexation-ultrafiltration is used to study the simulated wastewater containing nickel and copper.Palygorskite is selected as the complexing agent and is modified by cetyltrimethylammonium bromide.Through the experiment of treating the simulated wastewater containing nickel and copper by modified palygorskite complexation-ultrafiltration.The influence of metal wastewater removal efficiency could be effected by many factors,as well as the correlation between conductivity and rejection rate.The heavy metal salt types,operation duration,heavy metal ion concentration,pH value and operation pressure were investigated as the affecting factors.This provides basic theory for palygorskite to replace the traditional complexing agent and that of the separation of heavy metal ions in the mixed system.The results show that in the treatment process of single wastewater containing copper and nickel,the rejection rate of heavy metal ions increases with the increase of pH value of the solution.When the pH value is low,the rejection rate of heavy metal ions rises rapidly.When the pH value rises to a certain value,the increase of the rejection rate of heavy metal ions slows down with the rise of pH value.When the pH value is 7,the rejection rate of heavy metal ions in five kinds of copper heavy metal salt solutions is over 94%.With the extension of the system operation time,there is a significant difference in the rejection rate of copper ions between five kinds of heavy metal salt solutions.The rejection rate of copper ions in copper acetate solution is significantly higher than that in other heavy metal salt solutions.When the pH value is 7,the rejection rate of heavy metal ions in the five nickel heavy metal salt solutions is over 70.00%.When the pH value rises to 10,the rejection rate of heavy metal ions in the five nickel heavy metal salt solutions is over 98.00%.When the operation time is20 min,40 min and 100 min,there is a significant difference in the rejection rate of nickel ions among five different nickel heavy metal salt solutions.With the prolongation of operation time,the rejection rate of heavy metal ions in five kinds of copper and nickel heavy metal salt solutions is basically unchanged under different pH values.The rejection rate of heavy metal ions in copper and nickel decreases with the increase of the concentration of heavy metal ions When the initial concentrations of copper ions is 10 mg/L,20 mg/L,and 30mg/L,the rejection rates of the five copper heavy metal salts and heavy metal ions reachesmore than 97.00%.The rejection rate of heavy metal ions in the copper chloride solution is75.00%.When the initial concentration of nickel ions is 10 mg/L,the lowest rejection rate of heavy metal ions is nickel nitrate solution,which has a rejection rate of 84.90%.There is a decrease,among which the rejection rate of heavy metal ions in nickel acetate solution decreased most obviously.When the initial concentration of nickel ions increases to 50 mg/L,the rejection rate of heavy metal ions in nickel acetate solution is 60.50%.The operation pressure has no obvious influence on the rejection rate of heavy metal ions of copper and nickel.The concentration of heavy metal ions and pH value have little effect on the membrane permeation flux.The membrane permeation flux increases with the increase of operating pressure and the change of membrane permeation flux is linear within the allowable pressure range.There is no significant difference between the five kinds of copper and nickel heavy metal salts.With the prolongation of operation time,the five heavy metal salts of copper and nickel have the same change trend.The membrane permeation flux decreases with the prolongation of operation time.The conductivity of the solution and the rejection rate of heavy metal ions are relatively highly consistent with the change of the mass ratio of heavy metal to palygorskite.When the mass ratio of heavy metal to palygorskite is lower than a certain level,a fairly high metal rejection rate is obtained and the conductivity of the solution decreases with the increase of the mass ratio of heavy metal to palygorskite.Among the four heavy metal salts of copper and nickel,copper acetate and nickel chloride have the highest rejection and the lowest conductivity.In the treatment of simulated wastewater containing copper and nickel mixed heavy metal ions,the rejection rate of heavy metal ions increases with the increase of pH value of solution until close to 100%.When the pH value is 7,the rejection rates of heavy metal ions in the simulated wastewater of cupric chloride,cupric sulfate,cupric acetate,cupric bromide and cupric nitrate are more than 90%.The rejection rates of heavy metal ions in the simulated wastewater of nickel chloride,nickel sulfate,nickel acetate,nickel bromide and nickel nitrate are 70.30%,66.01%,66.76%,75.16% and 75.51%,respectively.