Parameter optimization of coagulation and sedimentation for fine suspended solids removal from mine water

In response to the issue of small particle size and difficult removal of suspended particles in the mine water of Baorixile open-pit coal mine, this study probed into the optimal parameters of the coagulation and precipitation process through single-factor and orthogonal experiments, and explored the mechanism behind the coagulation of fine particles in mine water.The optimal process parameters for coagulation and precipitation include: 50 mg/L of polyaluminum chloride (PAC), 5.0 mg/L of non-ionic polyacrylamide (NPAM) under 1 minute of rapid stirring (300 r/min), 8 minutes of slow stirring (50 r/min), and 5 minutes of settling.Under these optimum process conditions, the concentration of suspended solids (SS) is 5.0 mg/L with a removal efficiency of 99.1 %.Compared to the sole addition of PAC, the removal efficiency of fine particles below 10 μm increased by 25.9 %.Additionally, theζpotential of the mine water decreased from -40.9 mV to -16.3 mV, indicating that the coagulation mechanism of fine particles is mainly attributed to the adsorption and charge neutralization of PAC and the bridging effect of PAM.