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In order to establish the theortetical basis and optimize the production conditions for the separation process of the H_3BO_3-MgSO_4 mixed solution by using Mg(NO_3)_2 as the salting out agent.The phase diagrams of H_3BO_3─MgSO_4─Mg(NO_3)_2─H_2O system at 25℃ and 100℃ were studied.The results show that there appear MgSO_4·7H_2O,MgSO_4·6H_2O,Mg(NO_3)_2·6H_2O and H_3BO_3 three crystallization regions in the phase diagram at 25℃,and three crystallization regions of MgSO_4·H_2O,Mg(NO_3)_2·2H_2O,and H_3BO_3 at l00℃.When the temperatures rise from 25℃ to 100℃,the crystallization regions for magnesium sulfate hydlates grow larger and while that of H_3BO_3 get smaller.Only MgSO_4·4H_2O could be crystallized out alone,if evaporating the H_3BO_3─MgSO_4 solution in the presence of Mg(NO_3）_2.On cooling the MgSO_4 mother liquor,H_3BO_3 can be separated alone without any addition of water.
In order to establish the theortical basis and optimize the production conditions for the separation process of the H_3BO_3-MgSO_4 mixed solution by using Mg (NO_3) _2 as the salting out agent. The phase diagrams of H_3BO_3─MgSO_4─Mg (NO_3) _2_ H_2O system at 25 ℃ and 100 ℃ were studied.The results show that there appear MgSO_4 · 7H_2O, MgSO_4 · 6H_2O, Mg (NO_3) _2 · 6H_2O and H_3BO_3 three crystallization regions in the phase diagram at 25 ℃, and three crystallization regions of MgSO 4 · H 2 O, Mg (NO 3) 2 · 2H 2 O, and H 3 BO 3 at 100 ° C. The temperature rise from 25 ° C. to 100 ° C., the crystallization regions for magnesium sulfate hydlates grow larger and while that of H 3 BO 3 get smaller. Only MgSO 4 · 4H 2 O could be crystallized out alone, if evaporating the H_3BO_3─MgSO_4 solution in the presence of Mg (NO_3) _2.On cooling the MgSO_4 mother liquor, H_3BO_3 can be separated alone without any addition of water.