Application Of Forward Osmosis Binary Extraction Solution In The Treatment Of High Salt And Heavy Metal Wastewater

In recent years,the treatment of high-salt heavy metal wastewater is a difficult problem in environmental protection in China.The rapid development of industrialization,reverse osmosis concentration wastewater,industrial high-salinity wastewater,water environment has been large-scale pollution,so that people pay more attention to high-salt heavy metal wastewater.The disadvantages of the traditional treatment methods are that the recovery of heavy metals is not complete,the treatment range is small,easy to add pollution and other problems.As a new membrane separation technology,Forward Osmosis（FO）is widely used in many fields because of its low energy consumption,low pollution and recyclability.As an important part of industrial power generation,wastewater treatment,food concentration,desalination and other processes.Through the difference of Osmotic pressure between Feed Solution（FS）and Draw Solution（DS）,pure water is driven to move across the membrane from low concentration wastewater to high concentration imbibing Solution.In view of the serious shortage of fresh water resources in China,the further study of positive osmosis technology provides theoretical support for the practical application of the technology,which is of great significance to the current water resources shortage and energy pressure.This paper focuses on the following aspects:1.Two binary swabbing solutions with high water flux,low reverse solute flux and stable performance were selected by mixing four swabbing substances:Calcium chloride,magnesium chloride,sodium chloride and potassium chloride The optimum concentration ratios of two binary swabbing fluids were obtained by comparing the water fluxes of two binary swabbing fluids with different mass ratios and one binary swabbing fluid.2.Taking the water flux and the reverse solute flux as the performance index,under the conditions of different temperature,the concentration of salt in the feed solution and the orientation of the membrane（AL-DS,AL-FS）,the treatment effect of high salinity wastewater and the factors affecting the change of the water flux are studied,the binary extracting solution suitable for the treatment of high salinity wastewater is optimized.3.Taking water flux,reverse solute flux and retention rate as performance indexes,Zn²⁺,Ni²⁺,Zn²⁺and Ni²⁺mixed ions were added to the raw material solution of different concentrations,the feasibility of treating high-salt heavy metal wastewater with binary extraction solution was investigated.The main results are as follows:1.The best combination of positive permeability is CaCl₂+KCl group and MgCl₂+Na Cl group.The two groups have not only high water flux of small inorganic salt swabbing solution,but also low salt reverse osmosis of macromolecular swabbing solution According to the comprehensive consideration of economy and normal permeability,the optimum mass ratio of binary swabbing solution is m（CaCl₂）∶m（KCl）=1:1,m（MgCl₂）∶m（Na Cl）=1:2,temperature and flow rate are always proportional to the water flux in the suitable range,but the influence of flow rate on the water flux of Binary swabbing solution is smaller than that of single salt swabbing solution.The binary swabbing solution has more stable positive permeability and is feasible.2.When the temperature was increased from 25°C to 30°C,the water flux increased obviously.The water flux of Na Cl+MgCl₂group was higher than that of KCl+CaCl₂group.When the temperature was higher than 30°C,the increase of temperature could not offset the effect of concentration on the water flux,the optimum treatment temperature is 30°C,and the water flux in the AL-DS mode is higher than that in AL-FS mode.With the increase of the salt concentration of the feed solution,the water flux decreases rapidly,and the high salinity feed solution is unfavorable to the positive osmosis treatment.The inverse solute flux increases with the increase of temperature.3.The addition of Zn²⁺in the feed solution has little effect on the water flux.When the concentration of Zn²⁺is low,the water flux decreases slowly,but when the concentration of Zn²⁺is high,the water flux decreases faster than when the concentration of Zn²⁺is low,when the concentration of Zn²⁺is high,the change of the water flux to the addition of Zn²⁺is not obvious,and the content of Zn²⁺is less than that of salt ion,the retention rate of Zn²⁺ decreased with the increase of Zn²⁺concentration,and the highest retention rate of Zn²⁺was99.83%.When the salinity of the feed solution is 0 g/L,the initial water flux is reduced by the addition of heavy metal Ni²⁺,and when the salinity of the feed solution is 50 g/L,the water and ions formed by Ni²⁺also accumulate on the surface of the membrane.During the process,the water and ions dilute the accumulation of Na⁺and Cl^-,when the salinity of the feed solution is 100g/L,the amount of Ni²⁺is much less than that of the Salt Ions,and the effect of Ni²⁺on the water flux is small when the salinity of the feed solution is high The retention efficiency of Ni²⁺was above 99%,and the retention efficiency of Ni²⁺was better.When the salinity of raw material solution is 0 g/L,the water fluxes of two membrane orientations are:Baseline Water fluxes;,Zn²⁺wastewater fluxes;Zn²⁺,Ni²⁺mixed wastewater fluxes;Ni²⁺;When the salinity of the feed solution was 50 g/L,the water fluxes of the two membrane orientations were:Ni²⁺wastewater fluxes;baseline water fluxes;Zn²⁺,Ni²⁺mixed wastewater fluxes;Zn²⁺wastewater fluxes;The influence of heavy metal ions on water flux is small at high concentration,and the water flux is close.The retention of mixed heavy metal ions was slightly higher than that of single heavy metal solution.The membrane fouling can be effectively improved by physical cleaning and ultrasonic method.