Technical question: For wastewater treatment, is it better to use sodium hydroxide or sodium carbonate for neutralization?

Wastewater treatment basically involves adding alkaline neutralizers such as sodium hydroxide, sodium carbonate, and calcium hydroxide. The main factors considered when selecting a reagent include: price, reaction speed, dosage, costs of storage and preparation equipment, ease of transportation, and the final products after the chemical reaction. In terms of price, when the treatment effects are the same, the ratio of sodium hydroxide, sodium carbonate, and calcium hydroxide is 48∶100∶15 ； In terms of reaction speed, sodium hydroxide > sodium carbonate > calcium hydroxide ； In terms of cost related to usage amount, storage, and preparation equipment, sodium hydroxide < sodium carbonate < calcium hydroxide ； In terms of reaction products, the product calcium hydroxide is the easiest to dehydrate. When sodium hydroxide is used for neutralization, it produces a large amount of fluffy sludge that is difficult to settle. Meanwhile, sodium carbonate causes foaming issues due to the release of generated CO2. After comprehensive comparison, a suspension of calcium hydroxide, i.e., lime milk, is generally used as the neutralizer. Currently, composite alkalis are also used; their main components include: Ca(OH)2, activated white clay, diatomite, activated carbon, and saturated alkaline solution.

This post was last edited by hesonchang214 on 2012-8-6 at 11:53. It depends on what substance you need to neutralize, and what the pH level is

The wastewater after multi-effect evaporation of phenol-propanone wastewater has a pH of 4–5