不同有效钾提取方法的原理与效率比较

以6种典型含钾矿物为研究对象，探讨了盐溶液提取法、阳离子交换树脂法及四苯硼钠法等不同有效钾提取方法的原理、效率及影响因素的影响效应和机制。结果表明：盐溶液提取法对含钾矿物中钾的提取能力受离子种类、浓度及pH的影响，不同种类盐提取剂对矿物中钾释放的促进作用也因含钾矿物类型而异。NH4+ 使矿物层间塌陷，显著抑制各种矿物中非交换态钾的释放。阳离子交换树脂法对溶液中钾的提取能力与饱和离子种类及振荡强度有关。H+、Na+ 饱和树脂吸附溶液钾的能力大于Ca2+ 饱和树脂。振荡强度选为120 r/min可消除树脂法提取钾素时液膜扩散阻力的干扰。四苯硼钾的溶度积常数Ksp为2.40 × 10-8（25℃）。不加NaCl条件下，四苯硼钠浓度是影响四苯硼钠法对含钾矿物中钾的提取能力的主要因素。由不同方法的提取原理可以看出，铵盐类提取剂适用于速效钾为当季作物主要钾源（速效钾含量较高）的土壤钾素有效性的评价。而其他盐提取剂通过延长提取时间，可提取部分非交换态钾，可能较醋酸铵法更适合于提取非交换态钾为当季作物主要钾源的土壤有效钾。阳离子交换树脂法也可提取土壤非交换态钾，但操作较为繁琐，该方法更适用于原位研究土壤钾素的迁移、扩散等特性。四苯硼钠法提取效率较高，通过调节其提取力，可提取不同程度的非交换态钾，是具有较好应用前景的适于各类土壤和作物的土壤有效钾测定方法。

Comparing principles and efficiency of different methods for available potassium extraction

Principles and factors affecting the efficiency of different methods for extracting available K from six potassium-bearing minerals were investigated in current study.These methods included salt solutions,cation exchange resins and NaBPh₄ methods.The results showed that the effectiveness of K extraction from minerals by salts was mainly dependent on the ion type, concentration and pH value of the solution.Different salts had different preferential effect on K release from various minerals.NH₁⁺ saturation led to the collapse of the interlayer structure of the minerals and restrained non-exchangeable K（NEK） release remarkably.The effectiveness of K extraction by cation exchange resins method was mainly related to the ion type used to saturated resin beads and somewhat to the shaking speed used.Comparing with Ca²⁺,H⁺ and Na⁺ saturated resin had stronger K exchanging capacity from solution. For eliminating the effect of film mass transfer resistance on K exchange by resins,a shaking speed higher than 120 r/min was recommended.The solubility product constant of KBPh₄ was 2.40×10^-8（25℃） based on the data got in current study.Without NaCI, NaBPh₄ concentration was the main factor affecting the effectiveness of K extraction from minerals.According to the mechanism and efficiency of different methods,ammonium salts are suitable for evaluating K availability in soils with high content of exchangeable K. However,non-ammonium salts which can extract a small portion of NEK under long time extraction procedure,is superior to ammonium acetate to evaluate K availability in soils containing NEK available to crop.Cation exchange resins which can also extract NEK are more suitable for in situ research of soil K movement,but the procedure is relatively tedious.Different portion of NEK could be efficiently extracted with the NaBPh₄ method via modification of the K extracting power of the method.The NaBPh₄ method is assumed to be a good method for evaluation of available K in various soils in future.