Nanofiltration Membrane Separation Technology To Deal With The Apt Crystal Mother Liquor And The Preparation Of Ammonium Paratungstate Research

New technological methods for recovering the tungsten from the APT crystallized barren liquor and for producing the pure ammonium metagtungstate(AMT) crystal by the efficient and economical nanofiltration membrane process are studied in this paper.During the processing of APT crystallized barren liquor , APT solution was converted into AMT solution by adjusting the pH value,then AMT was treated by nanofiltration. The main purpose of this experiment is to remove chloride ion from the barren liquor,to realize the separation of tungsten and chloride and the concentration of the tungsten in the barren liquor.the experiment proves that controlling pH value 3~4, APT can be converted into AMT effectively, hi the procedure of nanofiltration under the 20~25kgf/cm2 membrane pressure,chloride ion can be removed and seperated from rude AMT solution effectively. The removal ratio of chloride ion can reach over 90%,the cut-off percentage of tungsten also can reach above 90.This process can concentrate and purify APT crystallized barren liquor and meet the requirement of the industrial production.For the production of pure AMT crystal, chemical neutralization ?nanofiltration ?evaporation crystalization was utilized.The effects of temperature ^ pH value N stirring velocity N Membrane pressure > crystalization solution density etc on the process are systematically studied. It is found that the optimized AMT production conditions are the following:neutralization temperature 80~95 癈\ pH 2.0~3.5;nanofiltration membrane pressure 15 ~ 20kgf/cm2 , crystalization solution density 2.39kg/L,then cooling.The transforming percentage of APT into AMT is above 97.62.The removal percentage of NOs" by nanoflitration is above 99,The tungsten cut-off percentage is above 99.9.At last,small-grainedN even-proporationed, white-colored -. high-purified AMT crystal can be obtained.The two techologies above have a lot of advantages: simple technological process,short production cycle, low cost,less environmental pollution and high quality etc.They have an important practical value and are a prospective project.