Study On Phase Transformation Of K-feldspar Based On Calcium Oxide

As one of the three nutrient elements required by plants,potassium plays a vital role in the growth of crops.As a large agricultural country,China has a huge demand for potassium fertilizer in agricultural production.The world’s potassium salt is mainly derived from water-soluble potassium minerals resources,but most of China’s potassium minerals are water-insoluble potasium resources.The annual import of potassium salt and potash fertilizer still exceeds 45%,because water-soluble potassium mineral resources are scarce in China.K-feldspar is the main insoluble aluminosilicate mineral in China,which is abundant and widely distributed.If the insoluble K-feldspar can be decomposed,and the insoluble potassium transform into water-soluble potassium.At the same time,the utilization of aluminosilicate minerals in K-feldspar will have a wide range of social and economic benefits.In this paper,K-feldspar was used as raw material,and the phase transformation rule of K-feldspar was studied by single factor experiment under hydrothermal conditions.The effects of hydrothermal temperature,hydrothermal time,n(Ca)/n(Al+Si)and the ratio of liquid to solid on the extraction efficient of potassium oxide during the process of leaching K-feldspar with calcium oxide were investigated.The second-order central composite design of response surface method was used to optimize the process conditions and evaluate them.At the same time,the influence of sucrose additives on the phase and solubility of leaching K-feldspar from calcium oxide was studied.The results show that increasing the hydrothermal temperature,n(Ca)/n(Al+Si)and hydrothermal time can significantly increase the extraction rate of potassium oxide,and the ratio of liquid to solid has little effect on the extraction efficient of potassium oxide.As the temperature increases from 150°C to 280°C,the extraction efficient of potassium oxide increases by 62.91% to 95.47% under the conditions of hydrothermal time of 8h,n(Ca)/n(Al+Si)=0.83,and liquid-solid ratio of 20.Response surface methodology showed that the main factors affecting the extraction efficient of potassium oxide were hydrothermal temperature,n(Ca)/n(Al+Si),and hydrothermal time.The prediction model established by regression fitting of the data was accurate and reliable.The predicted value of potassium oxide extraction efficient is in good agreement with the experimental results.When the amount of sucrose added is n(Su)/n(Ca)= 0.1,the tobermorite morphology changes from rod-like to plate-like or layered.At the same time,it has better adsorption performance than tobermorite without added sucrose.