The recovery of sulfur as ZnS particles from sulfide-contained wastewater using fluidized bed homogeneous crystallization technology

Sulfide wastewater that is anthropogenically generated from industrial activities is highly corrosive, hazardous, and harms the natural ecosystem. This study uses a novel fluidized-bed homogeneous crystallization (FBHC) method to remove sulfide ions from an aqueous solution. Zinc is used as a precipitant to crystallize ZnS homogeneously in the FBHC reactor to reduce the sludge, which is commonly produced in a conventional chemical precipitation process. The optimal pH value, [Zn2+](0)/[S2-](0) (M) ratio, sulfide cross-sectional surface loading (L, kgS/m(2).hr), and hydraulic retention time (HRT) for the system are established, to optimize the sulfur removal efficiency. The maximum crystallization ratio and the total removal efficiency for sulfur are 97.7% and 98.8%, respectively, at pH = 5.4, a [Zn2+](0)/[S2-](0 M) ratio of 1, a cross-sectional surface loading of 2.2 kg-S/m(2).hr, and an HRT number of 6 with an initial sulfur concentration of 320 mg/L. The solid products are collected and identified as zinc sulfide (wurtzite) using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Xray photoelectron spectroscopy (XPS).

Automated summary

This study utilizes a novel method, fluidized-bed homogeneous crystallization, to remove sulfide ions from wastewater. By homogeneously crystallizing ZnS using zinc as a precipitant, the production of sludge in the conventional chemical precipitation process is reduced. The study establishes the optimal pH value, [Zn2+](0)/[S2-](0) ratio, sulfide cross-sectional surface loading, and hydraulic retention time to optimize the sulfur removal efficiency.