Mechanochemical synthesis of kaolin–KH₂PO₄ and kaolin–NH₄H₂PO₄ complexes for application as slow release fertilizer

• Published in: Powder technology Vol. 212; no. 2; pp. 354 - 358
• Main Authors: Solihin, Zhang, Qiwu, Tongamp, William, Saito, Fumio
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 10.10.2011; Elsevier
• Subjects: ammonium compounds; Amorphous structure; Applied sciences; Ball mills; Chemical engineering; Chromatography; Exact sciences and technology; Fertilizing; Grinding; ion exchange chromatography; ions; Kaolin; milling; Miscellaneous; nutrients; potassium; potassium dihydrogen phosphate; Powder technology; Rotational; slow-release fertilizers; Solid-solid systems; Synthesis; X-ray diffraction; Ion chromatography; Ball mill; Fertilization; Slow release fertilizer; Mechanochemical synthesis; Milling; NH4H2PO4; Differential thermal analysis; KH2PO4; Kaolin; Fertilizers
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2011.06.012

A milling process to reduce kaolin to amorphous phase in the presence of KH₂PO₄ or NH₄H₂PO₄ and allow mechanochemical (MC) reaction for incorporation of KH₂PO₄ and NH₄H₂PO₄ into the kaolin structure was investigated in this work. Mixtures of kaolin and KH₂PO₄ and NH₄H₂PO₄ in separate systems were prepared by milling in a planetary ball mill. Tests with kaolin contents ranging from 25 to 75wt.% and mill rotational speeds from 200 to 700rpm were performed to evaluate incorporation of KH₂PO₄ and NH₄H₂PO₄ and release of K⁺, NH₄ ⁺ and PO₄ ³⁻ ions into solution. Analyses by XRD, DTA and ion chromatography indicated that the MC process was successfully applied to incorporate both KH₂PO₄ and NH₄H₂PO₄ into the amorphous kaolin structure. Release of K⁺ and PO₄ ³⁻ ions from the system (kaolin–KH₂PO₄) when dispersed in water for 24h reached only up to 10%. Under similar conditions for the system (kaolin–NH₄H₂PO₄), release of NH₄ ⁺ and PO₄ ³⁻ ions reached between 25 and 40%. These results indicated that the MC process can be developed to allow amorphous kaolin to act as a carrier of K⁺, NH₄ ⁺ and PO₄ ³⁻ nutrients to be released slowly for use as fertilizer.