Preparation of a zeolite NaP1/hydroxyapatite nanocomposite and study of its behavior as inorganic fertilizer

BACKGROUND: A number of inorganic fertilizers have been used as a slow-release fertilizer for plants but control of release rates of nutrient ions can be difficult. We have prepared a novel slow-release inorganic fertilizer consisting of zeolite NaP1/hydroxyapatite nanocomposite containing the following nutrient ions: 17.4 mg g(-1) of ammonium ion, 54.6 mg g(-1) of potassium ion and 24.1mg g(-1) of phosphate ion. The release behavior of nutrient ions were evaluated in distilled water. RESULTS: Zeolite NaP1 was synthesized from coal fly ash by alkaline hydrothermal treatment. The zeolite surfaces were then covered with hydroxyapatite needle-like crystals of about 200 nm diameter by a hydrothermal treatment of the calcium-exchanged zeolite NaP1 in a mixed solution of potassium and ammonium phosphates at 40 degrees C for 8 h. The release behavior of the nanocomposite was evaluated by measuring the release into distilled water of nutrient ions over the long term. Phosphate ions were slowly released by the dissolution of HA in water, ammonium and potassium ions by cation exchange with calcium co-dissolved with phosphate. CONCLUSION: The zeolite NaP1/hydroxyapatite nanocomposite obtained is very useful as an inorganic fertilizer which can release nutrient ions over a long time. (C) 2013 Society of Chemical Industry