Abstract: In the industrial water treatment section of a copper mine，wastewater is first treated via Fenton oxidation，followed by neutralization with lime slurry to bring the treated effluent to near-neutral pH. Subsequently，polyacrylamide（PAM）is added to flocculate fine particles of undissolved lime in the bottom sludge. The resulting supernatant is discharged in compliance with regulatory standards，while the bottom sludge is transported to the tailings pond. In this process，the lime slurry used has a concentration of 10%. Given that the solubility of Ca（OH）₂ in water at 20 °C is only 0.165 g/100 g H₂O，it is inferred that the neu⁃ tralization reaction efficiency of the lime slurry in field applications is low.To verify this inference，compara⁃ tive neutralization experiments were conducted using two alkaline agents of 40% NaOH solution and the on�site lime slurry to treat the acidic effluent after Fenton oxidation. In addition，instrumental analyses，includ⁃ ing particle size analysis，scanning electron microscopy（SEM），and energy-dispersive X-ray spectroscopy （EDS），were employed to investigate the lime content in the underflow slurry from the lime neutralization tank，providing cross-validation for the experimental results.The results indicate that the neutralization reac⁃ tion efficiency of the 10% lime slurry used on-site ranges between 40% and 60%. As the pH of the solution increases，the neutralization efficiency of the lime slurry decreases significantly. Unreacted Ca（OH）₂ co�precipitates with neutralization products such as CaSO₄，forming sludge. This not only results in substantial waste of lime slurry but also causes severe blockage of conveying pipelines.Therefore，to improve efficiency and reduce scaling，it is recommended to first adjust the Fenton-treated tailwater to a pH of approximately 4 using an appropriate amount of lime slurry，followed by the addition of a small quantity of liquid alkali to fur⁃ ther raise the pH to the target range of 6~9. This approach would significantly enhance the reaction efficien⁃ cy of the lime slurry and markedly reduce scaling issues in the system.

Key words: Fenton oxidation, neutralisation reaction, lime slurry, flotation wastewater, environmen? tal engineering