Phosphate-Adsorbed by Concrete-Based Layered Double Hydroxide: A Slow-Release Phosphate Fertilizer

A novel multipoint titration coprecipitation method was used to prepare concrete-based layered double hydroxide (CLDH) to uptake phosphorus into slow-release phosphate fertilizer. Both the characteristics and the slow release of CLDH-P were investigated. Results showed that the multipoint titration method was efficient for coprecipitation. P-loaded CLDH under weak acid conditions (CLDH-P1) contained mainly Al-P and Ca-P (CaHPO4<middle dot>2H2O, DCPD), while the content of Ca-P greatly increased in the product under weak alkaline conditions (CLDH-P2). The slow-release effects of the two samples in soil leaching columns were significantly better than triple superphosphate (TSP). CLDH-P1 was preferably used for mung bean growth promotion due to its better availability. The dry weight of CLDH-P1 mung bean increased by 33% in 40 days, which was obviously better than that of the TSP group. In addition to phosphorus, the nutrient elements Ca and Mg were also enriched in mung bean plants. The results revealed an economical and sustainable candidate for phosphorus recovery.