K_2SO_4-MgSO_4-H_2O三元体系蒸发制备软钾镁矾及其物理性质

Preparation of schoenite by evaporating the system of K_2SO_4-MgSO_4-H_2O and its physical property

利用25℃K2SO4-Mg SO4-H2O相图为理论依据,制备软钾镁矾晶体饱和溶液,控制蒸发速率在25℃下自然蒸发,结晶析出大颗粒纯软钾镁矾晶体,化学组成分析、晶体X-ray衍射图谱分析结果均证明为纯软钾镁矾晶体,热重分析结果表明在56~58℃时,软钾镁矾开始失去结晶水。选取温度(T)、真空度(Pa)、粒径(d)、时间(t)四因素,以失重率为指标设计正交试验,结果表明,晶体粒径对软钾镁矾失重率的影响最大,较小的粒径容易导致软钾镁矾失去结晶水,而真空度和环境温度对软钾镁矾失重率的影响相当,时间对软钾镁矾的影响最小,实验结果为钾镁肥产品水分测定、生产和存放提供最佳参数。

The saturated solution of schoenite was prepared according to the phase diagrams of the system K2SO4-Mg SO4-H2 O at 25 ℃.The water of the solution was evaporated at 25 ℃ by controlling the evaporation rate,giving pure schoenite crystals with large particles.The result was confirmed by chemical analysis and crystal X-ray diffraction. Thermo gravimetric shows that schoenite begins to lose crystal water at 56 ~ 58 ℃. By using orthogonal test method,the influence of different parameters( temperature( T),vacuum degree( Pa),particle size( d),and holding time( t)) on the characteristic of schoenite was studied based on the weight loss. The results show that the particle size is the most important factor influences the mass-loss of the schoenite,which means that the smaller particles are easier to lose crystal water. The vacuum degree and temperature have a similar influence on the mass-loss,and the influence of holding time is the least. The experimental results can provide the parameters for the water determination,production process and storage of the schoenite.