Chemical activation of phosphogypsum exhibits enhanced adsorption of malachite green from aqueous solution due to porosity refinement

Abstract

Owing to its uncomplicated synthetic methodology and exorbitant market demand, malachite green is widely used in numerous industries, particularly as a fungicide in aquaculture. Considering its intrinsic toxicity and potential long-term health impacts, deployable and cost-effective strategies must be developed for eliminating water-soluble malachite green. In this study, chemically activated phosphogypsum, a byproduct of fertilizer production, was used to remove malachite green from an aqueous system. Due to its low cost and abundance, the use of phosphogypsum as a sorbent material may significantly reduce the cost of adsorption-based processes. Moreover, its structural durability allows efficient recycling without significant deformation during reactivation. However, untreated phosphogypsum exhibits minimal efficiency in adsorbing synthetic dyes due to its unfavorable surface chemistry. Our investigation revealed that Zn activation induced a noticeable increase in pore volume from 0.03 to 0.06 cm³·g⁻¹. A 60 mg·L⁻¹ sorbent dose, pH 7, 150 r·min⁻¹, and operational temperature of 30 °C produced 99% quantitative sorption efficiency. Response surface methodology and artificial neural network were used to optimize process parameters by validating experimental values. No detectable toxicity was observed in Escherichia coli when exposed to the treated water.