What is the most important factor affecting the treatment of metals in colored smelting wastewater using lime milk?

Different heavy metals have different pH ranges for precipitation, and pH control is primarily used for selective precipitation.

The type and amount of precipitates are controlled by pH value.

It is generally difficult to meet the required standards by directly using lime to neutralize the metals in colored smelting wastewater; moreover, the lime sludge resulting from this neutralization process is likely to have toxicity levels that exceed the allowed limits, thus becoming a secondary pollutant. If such sludge is classified as hazardous waste, its further disposal incurs higher costs. From the perspective of meeting water quality standards, when directly neutralizing the metals in colored smelting wastewater with lime, it is crucial to control the pH value properly. A more reasonable treatment process is as follows: The colored metal smelting wastewater is first subjected to a sulfidation reaction to produce metal sulfide precipitates. The valuable metals contained in these precipitates can be recovered. Since the solubility product of metal sulfides is very low, the wastewater after sulfidation contains metal ions at levels that meet the specified standards ； The sulfided wastewater is neutralized using lime through a back-neutralization process, resulting in both the effluent and the lime sludge meeting the required standards.