Preparation Of Slow-release Potassium Fertilizer From K-feldspar

Slow-release fertilizer (SRF) is a green environment-friendly fertilizer with slow-acting and long-acting characteristics. SRF can keep achieve the balance among nutrient releasing, soil nutrient supplying, and the assimilating nutriment of the plant, which increase the fertilizer utilization and reduce agricultural and environmental pollution caused by irrational fertilization. Hence, SRF is the development direction of modern agriculture. Our team has made a contribution to the production of potassium sulfate by using the hydrothermal alkali decomposing potassium feldspar technology. Based on our former study, this dissertation is focused on developing two novelty SRF synthesis methods.SRF is prepared by sintering process. The raw materials MgO, K2CO3and the fine SiO2powder are mixed together in different two theoretical material ratios, and then sintered at1050℃for2hours, finally yielded K2MgSi3O8, K1.14Mg0.57Si1.43O4composite(Sample CH-1) and K2MgSiO4(Sample CH-2). The preparation of slow-release fertilizer by sintering kalsilite that mainly research how the different sintering temperature (900℃～1150℃) affects the phase change of product. When the SD3series products are sintered at the temperature of900℃, get the main phase K2MgSi3O8, however, the reaction is not complete, there still exist periclase impurity phase; at the temperature of1050℃, more purer phase K2MgSi3O8of slow-release fertilizer can be got; sintering temperature is higher than1100℃, the main phase of the sintered products transform K2MgSi3O8into K1.14Mg0.57Si1.43O4. The as-prepared samples are dried pressed, and tested the nutrition release in the pure water. The result shows that the K+release velocity is fast within2hours and become slowly continuous later. The release nutrition performance of sample SD3is better than SD4series products. Even though not meet the national standard, the release nutrition performance of SRF is better than the normal fertilizer.Silica gel coated potassium sulfate is prepared by the spray-drying. The relation between the ratio of raw materials and performance of product is studied. Generally, the mixed slurry of SiO2and K2SO4is faintly acid and pH is3～4. And the pH number increases as the ratio of SiO2to K2SO4reduce. After the spray-drying, the as-prepared sample is similar spherical and its diameter is3～10um. When the ratio of SiO2to K2SO4is3:7, the product shows the best performance. Even though not meet the national standard, Silicone gel-coated potassium sulfate products has showed some slow-release effect.