Potential Slow Release Fertilizers Based on K2MgSiO4 Obtained from Serpentinite

In this work, a potassium magnesium silicate mineral based on phase K2MgSiO4 was prepared from serpentinite rock and studied as a potential K and Mg slow-release fertilizer. The material was prepared by impregnation of serpentinite/KOH and calcination at 700 °C to produce K2MgSiO4 phase, olivine and forsterite. The release patterns of K and Mg in the stirred-flow trial and leaching through the soil columns showed that K2MgSiO4-based materials released K on lower rates than KCl and MgSO4.7H2O, however, there was no evidence of Mg release. The extraction with 1 mol L-1 NH4OAc showed a considerable content of Mg and K for K2MgSiO4-based materials, due to exchange of NH4+ and Mg2+. X-ray diffraction (XRD) analysis of materials impregnated with K and calcined showed peaks relative to K2MgSiO4. After leaching, the peaks intensity diminished, supporting that part of K leached. Therefore, the samples showed great potential as slow-release K-fertilizers when compared with KCl source.本研究以蛇纹岩为原料，制备得到基于硅酸镁钾相K₂MgSiO₄的钾镁硅酸盐矿物，并将其作为潜在的钾、镁缓释肥料开展研究。该材料通过将蛇纹岩与氢氧化钾浸渍后，于700℃下煅烧制备而成，产物包含K₂MgSiO₄相、橄榄石与镁橄榄石。搅拌流试验与土柱淋溶试验结果显示，相较于氯化钾（KCl）与七水硫酸镁（MgSO₄·7H₂O），基于K₂MgSiO₄的材料的钾素释放速率更低，但未检测到镁素释放现象。采用1 mol/L乙酸铵（NH₄OAc）进行提取的结果表明，由于NH₄⁺与Mg²⁺的离子交换作用，基于K₂MgSiO₄的材料中含有可观的镁、钾元素含量。对经钾浸渍并煅烧后的材料进行X射线衍射（X-ray Diffraction，XRD）分析，结果显示存在对应K₂MgSiO₄的特征衍射峰。淋溶处理后，该特征峰的强度出现减弱，证实了部分钾素发生淋溶流失。因此，相较于氯化钾肥料，该样品具备优异的缓释钾肥应用潜力。