Ecologically Friendly, Slow-Release Granular Fertilizers with Phosphogypsum

Abstract

The paper provides information about phosphogypsum waste from various enterprises and how it can be used in the production of slow-release fertilizer mixtures. Such fertilizer mixes can potentially be used with different types of soil, including acidified soils. Experiments were conducted on phosphogypsum samples from the old and new dumpsites under the Taraz branch of Kazphosphate LLP. All representative samples underwent chemical, mineralogical, thermal gravimetric and differential thermal analyses, as well as Fourier-Transform Infrared (FTIR) spectroscopy and polarized optical microscopy (POM). No significant differences were found in the content of the samples. Phosphogypsum from the old dumpsite contained 87.93% gypsum (CaSO4 · 2H2 O), 9.10% quartz (SiO2), 17.55% calcium (Ca), 0.13% potassium (K), 0.35% phosphorus (P), and 0.80% phosphorus pentoxide (P2O5). Phosphogypsum from the new dumpsite contained 85.04% gypsum, 10.58% quartz (SiO2), 19.42% calcium (Ca), 0.14% potassium (K), 0.30% phosphorus (P), and 0.69% phosphorus pentoxide (P2O5). The current paper also offers a technological scheme for making a slow-release fertilizer mixture with phosphogypsum.