Preparation Of Monopotassium Phosphate By Electrolysis

The purity of monopotassium phosphate prepared by electrolysis is very high, the electrolytic process is short, its pollution to the environment is very light, and its corrosion to the equipment is weak. The electric conductivities that are required by the production of monopotassium phosphate are measured; finally, the processes for preparation of KH2PO4 by electrolysis are studied.Electric conductivities of three kinds of solutions are measured and studied in this paper. Firstly, the relationships between electric conductivities of H3PO4-KH2PO4 solutions and temperature and molar ratio are studied. Secondly, the relationships between electric conductivities of NaOH-NaCl-NaClO3 solutions and temperature and molar ratio are studied. Thirdly, the relationships between electric conductivities of potassium chloride solutions and temperature and molar ratio are studied. Additionally, the equation of is obtained by regressing the experimental data, which can express these relationships between electric conductivities of the three kinds of solutions and temperature, and whose correlative coefficients (R2) are more than 0.99. The equaton of can be obtained by regressing the experimental data, which can express these relationships between electric conductivities of the first two kinds of solutions and molar ratio, and whose correlative coefficients (R2) are more than 0.98. By regressing the experimental data, the relationship between electric conductivities of potassium chloride solutions and concentration () can be expressed by, whose correlative coefficients (R2) are more than 0.99. Three kinds of processes are studied and discussed in this paper. The first process is failed, which is for manufacture of monopotassium phosphate and sodium chlorate from potassium chloride, phosphoric acid and sodium hydroxide. The second electrolytic process is successful, which is for production of monopotassium phosphate, hydrogen and chlorine from potassium chloride and phosphoric acid by using a cationic permselective membrane cell. The actual reduce voltage is 1.6748V, which can be got by the regression of experimental data. The proper electrolytic conditions are obtained, the voltage of electrolytic cell is 3.1～3.2V; The temperature of electrolysis is 80～90℃. The content of monopotassium phosphate is 100.31%. The third process is possible, which uses industrial potassium chloride and wet-process phosphoric acid as material, but in this paper the electrolysis doesn't work, because the concentration of impurity in wet-process phosphoric acid using is too high. Additionally, the influence of the main impurities in wet-process phosphoric acid on electrolysis was studied in this articale. The conclusion is drawn that if the content of fluosilicic acid in wet-process phosphoric acid is less than 0.19% or the content of dialuminium trioxide in wet-process phosphoric acid is less than 1.47%, the elctrolysis would go on wheels. In addition the influence of diiron trioxide on electrolysis is poor. Finally a process is presented in this paper, which prepares monopotassium phosphate by electrolyzing wet-process phosphoric acid and potassium chloride solutions.