Comparative Assessment of the Leaching Properties of Fly Ash and Phosphogypsum Disposed of in South Africa

Fly ash (FA) and phosphogypsum (PG) are readily available industrial waste materials commonly disposed of in landfills. Knowledge of the leaching behavior of FA and PG can help us understand how to diminish their adverse effects on the ecosystem. However, there is limited research on the leaching properties of the FA and PG disposed of in South Africa. This study aims to comparatively assess the leaching properties of FA and PG disposed of at Eskom Duvha Power Station in Mpumalanga and Foskor Ltd in Phalaborwa, South Africa. The toxicity characteristic leaching procedure (TCLP) was used to obtain the leachates which were further analyzed by the inductively coupled plasma-mass spectrometer (ICP-MS). An XRF spectrometer was used to find the chemical composition of FA and PG. It was found that both FA and PG are non-hazardous since their leachate concentrations are within the US EPA TC, US EPA land disposal regulation, and EU waste acceptance at landfills. The solubility and mobility of As and Se depend on the alkaline concentration of the solution. The As adsorption rate escalates in Fe oxides and its mobility depends on the waste chemistry and pH. The chemical elements present in FA and PG i.e., Al3+, Si4+, Fe2+, Ca2+, instead of being leached into the ground can be incorporated into cement for construction applications. The present study output contributes knowledge on leaching properties of FA and PG in South Africa and can help policymakers create informed solid waste management frameworks and understand the potential of reusing in construction and recovering the elements of economic interest (e.g., Zn, Cu, Fe, P). The recycling of FA and PG for use as construction materials can help address landfill leaching problems and promote circularity.