Sulfide recovery using fluidized bed homogeneous crystallization technology to produce nickel sulfide from wastewater that contains sulfides

Sulfide-containing wastewater, characterized by its foul odor, corrosiveness, and toxicity, can endanger human health. Fluidized-bed homogeneous crystallization (FBHC) avoids the excessive sludge production commonly associated with conventional chemical precipitation methods. In this study, FBHC is used to treat sulfur-containing synthetic wastewater. Furthermore, nickel-containing wastewater was utilized as a precipitant in the system, hence the advantage of simultaneous sulfur and nickel removal from the wastewater. The operating parameters, including pH, a precipitant dosage of [Ni²⁺]₀/[S²⁻]₀, and cross-sectional surface loading (L_S, kg/m²h) are optimized. The optimum operating conditions of pH 9.8 ± 0.3, [Ni²⁺]₀/[S²⁻]₀ = 0.8, and L_S = 1.5 kg/m²h results in total sulfur removal (TR) of 95.7% and crystallization ratio (CR) of 94.8%. The effect of organic compounds (acetic acid, oxalic acid, EDTA, and citric acid) and inorganic ions (NO₃⁻, CO₃²⁻, PO₄³⁻, F⁻, and Cl⁻) on the nickel sulfide granulation process was discussed.