Abstract: The phosphoric acid-modified kaolin material was used to take a chemical adsorption with K+ due to the active hydrogen groups on the surface， but the accumulation of H+ will affect the adsorption reaction. The hydroxyl groups of antigorite were activated to release OH- by milling. The OH- was dissolved to neutralize the accumulated H+ to promote the adsorption of K+. The effects of factors such as milling speed， mass ratio of phosphoric acid modified kaolin （KP） and activated serpentine （MAS）， adsorption time， and different initial concentrations were investigated. The results showed that the ball milling speed was 500 r/min， mass ratio of KP to MAS was 0.6∶0.4， the adsorption time was 120 min， and the initial concentration was 300 mg/L， the actual saturated adsorption amount of K+ was 30.25 mg/g， which reaches the level of industrial application. When K+ was adsorbed and saturated KP/MAS was tested in distilled water， only less than 5% K+ was dissolved out， and nearly all K+ was dissolved out after 8 h in citric acid solution with concentration of 2%， indicating that the product had low solubility in water， and had good slow-release characteristics under weak acid environment， which was conducive to the absorption of nutrients by plant roots.

Key words: kaolinite modified by phosphoric acid, antigorite, potassium ions, mechanochemical activation, adsorption equation