Mathematical modeling and ecological assessment of fluoride release in a mixture of mineralized phosphorite waste and wastewater from the fat and oil industry

Abstract

This study investigates fluoride loss in a mixture of mineralized mass (MM) extracted from the Central Kyzylkum phosphorite deposits and acidic wastewater (AWW) generated by the fat-and-oil industry. The research aimed to evaluate fluoride release and its retention stability under various conditions. Experimental trials were conducted using AWW:MM mass ratios ranging from 100:10 to 100:40. The experiments were carried out at 333 K for 30 minutes, employing ionometric analysis. The theoretical fluoride content varied from 1.23 g to 4.90 g, while the experimental values ranged from 0.88 g to 3.68 g. The lowest fluoride loss was observed at the 100:20 ratio, amounting to 0.34 g. The highest loss, 1.22 g, was recorded at the 100:40 ratio. The 100:25 ratio (pH 5.90), with a fluoride loss of 0.40 g and an experimental retention of 2.66 g, was identified as optimal. At pH values between 6.33 and 7.30, fluoride levels stabilized between 3.08 g and 3.68 g. An exponential regression model demonstrated a high degree of correlation (R² = 0.9767). The standard deviation ranged from ±0.002 g to ±0.008 g. Ions in AWW (SO₄²⁻: 48,145 mg/L and Cl⁻: 38,116 mg/L) significantly accelerated fluoride volatilization. The emission of HF gas contributed to atmospheric pollution; however, the 100:25 ratio minimized environmental impact. The results aligned with literature-reported fluoride loss ranges of 0.3–1.5 g. This research contributes to the development of effective and environmentally safe approaches to waste reutilization.