Increasing phosphorus solubility by sintering igneous Dorowa phosphate rock with recycled glass

Autor: Mike Bretherton, Mike Hedley, Akinson Tumbure, Peter Bishop
Rok vydání: 2020
Předmět:
Zdroj: Journal of Thermal Analysis and Calorimetry. 145:3019-3030
ISSN: 1588-2926
1388-6150
DOI: 10.1007/s10973-020-10078-2
Popis: The lack of low-cost phosphorus fertilizers is a major limitation for food production on Zimbabwe’s many smallholdings. A thermally fused magnesium phosphate could be manufactured from the local Dorowa phosphate rock (PR) but would be expensive because of the high cost of required additives and energy. This paper investigates the phosphorus solubility of mixtures of igneous Dorowa PR with either recycled glass or magnesium silicates, before and after thermal alteration at sub-fusion temperatures. The thermal behavior and chemical transformation of Dorowa PR and various additives were investigated by thermo-gravimetric and differential scanning calorimetric analysis and X-ray powder diffraction. Thermal transformation of Dorowa PR + serpentine and Dorowa PR + dunite mixtures resulted in decomposition of calcite, kellyite, lizardite, and chrysotile present in the original mixtures and recrystallization of dehydroxylated metachrysotile to forsterite. The final products of air-cooled Dorowa PR + glass mixtures sintered at 1173 K contained ahrensite (Fe2(SiO4)), wollastonite (CaSiO3), quartz (SiO2), and hydroxy-fluorapatite. Compared to the unamended Dorowa PR, thermal alteration of Dorowa PR + glass mixtures at 1173 K led to a 62%, 73%, and 44% increase in citric soluble phosphorus when mixed at 1:2, 1:1, and 2:1 (Dorowa PR:glass), respectively. This increase in the citric soluble phosphorus content increases the agronomic value of Dorowa PR and is likely the result of substitution of PO43− in hydroxy-fluorapatite by SiO44− and or Mg2+/Na+ for Ca2+ and Fe2+.
Databáze: OpenAIRE
Externí odkaz: