Coagulation of coal suspensions with aluminum sulfate
and polyacrylamide-based flocculants in water purification

Summary

This study addresses the issue of sedimentation stability of SPDK-2 activated carbon suspensions in water purification processes. Despite its high sorption activity, activated carbon forms stable dispersions that complicate further water purification. The study examined the effectiveness of aluminum sulfate coagulant and polyacrylamide-based flocculants (non-ionic AK-631, anionic Polypam A-SG, cationic Polypam C-YZ, C-QG, C-GM, C-WQ, C-QE, and C-QU) in aggregating carbon particles in natural water of the Penza water reservoir. Microscopic analysis was used to estimate the aggregation efficiency of the sorbent particles. The calibrated drop method was used to record particle sizes and average the obtained data. It was found that cationic flocculants, particularly C-QG, exhibit a synergistic effect with aluminum sulfate forming large aggregates (mass-average particle radius of 0.103 mm while using a mixture of 80 mg/l aluminum sulfate and 0.2 mg/l C-QG flocculant). The highest efficiency was achieved with a combination of 40–80 mg/l of aluminum sulfate and 0.1–0.2 mg/l of C-QG flocculant. The results obtained have practical implications for the optimization of the water purification processes at the water treatment facilities in the Penza Region and demonstrate the feasibility of using charged reagents for hydrophobic carbon sorbents.

Key words

coagulation , water treatment , sedimentation , aluminium sulphate , activated carbon , flocculation , polyacrylamide , aggregation , synergistic effect