Abstract:

Phosphogypsum (PG) from fertilizer production is commonly stored in exposed surface areas, leading to its interaction with the surrounding environment. In this context, understanding the chemical properties, leachate composition, and environmental interactions of PG is crucial for devising effective waste management strategies. This study aimed to comprehensively characterize PG samples, assess their environmental behavior through leaching tests under varying conditions, and evaluate their geochemical behavior using modeling techniques. The samples underwent thorough chemical and mineralogical characterization processes. Leaching tests were conducted under specific pH conditions and different liquid-to-solid ratios (L/S), including EPA 1313, EPA 1316, TCLP, and SPLP methods. Long-term geochemical behavior was evaluated using kinetic weathering cells. The results indicated that PG, primarily composed of calcium and sulfur, was classified as non-hazardous based on the US regulatory leaching test. PG exhibited high leachability of elements under acidic conditions (Ca, S, P, and F). Leaching using distilled water for over 90 days revealed cumulative concentrations of analyzed elements (Ca, S, P, F, Cu, and U), which could pose adverse effects on the nearby environment if PG is stored for a long period. Geochemical modeling using PHREEQC showed that the speciation of Ca, S, P, and F depended on pH, with the dissolution of these elements mainly controlled by gypsum, anhydrite, and bassanite phases.

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Jean-Louis Bodinier