UV light irradiation enhanced sand filtration performance of metal sulfide particles in acidic wastewater: Efficiency and mechanism

Sand filtration was innovatively used to separate metal sulfide particles from acidic wastewater. CuS particles were efficiently separated by sand filtration, and the turbidity in the effluent maintained less than 1.00 NTU. However, the filter column was easily penetrated after 25 min filtration of As 2 S 3 particles. CdS particles had poor sand filtration performance and the turbidity in the effluent was higher than 121.00 NTU. UV light irradiation greatly increased the zeta potential of CdS and As 2 S 3 particles from −26.79 to −8.46 mV and −38.45 to −11.20 mV, respectively, and also improved the hydrophobicity, making the water contact angels of CdS and As 2 S 3 particles increased from 22.79° to 61.70° and 64.50° to 87.80°, respectively. After UV irradiation, the particle size distribution of CdS and As 2 S 3 particles was transferred to a range with larger particle sizes. The sand filtration performance of the UV light irradiated As 2 S 3 and CdS particles was significantly enhanced, and the turbidity in the effluent was less than 1.00 NTU under a flow rate of 6.0–12.0 m/h. The calculated XDLVO energies ( Δ E d 0 Tot ) between the UV irradiated metal sulfide particles as well as between these particles and quartz sand greatly decreased, implies the self-aggregation and attachment on the surface of quartz sands of these particles were markable enhanced, resulting the improvement of sand filtration performance of these particles. This study presents an efficient and economical method to separate metal sulfide particles produced by sulfidation precipitation from acidic wastewater.