Chemical Treatment for Nitrite Nitrogen Removal From Stainless Steel Pickling Liquor Wastewater

摘要

Steel pickling produces acidic waste liquor that has a high metal content and contains otherrncompounds, including nitrogen compounds such as nitrite. Most treatment technologies focus onrneliminating the hazardous nature of the waste pickling liquor by neutralization with lime.rnIncreasing the pH generates waste sludge and precipitates heavy metals; thus, reducing thernhazardous characteristics. Alternative treatment technologies focus on recovering valuable acidrnand metals. However, few of these treatments remove nitrogen compounds that can cause wholerneffluent toxicity problems. For this work, chemical treatments for removing nitrite from wasternpickling liquor were studied. Sulfamic acid, sodium bisulfite, and sodium hypochlorite (bleach)rnwere used to treat waste pickling liquor from a stainless steel continuous rolling mill. Sulfamicrnacid was determined to be the most efficient chemical treatment and most environmentallyrnfriendly because it completely reduced nitrite to nitrogen gas, while the other treatmentsrnproduced other nitrogen compounds (nitrous oxide or nitrate). The testing showed that thernhighest treatment efficiency occurs under acidic conditions and should be performed prior tornneutralization.