Production of zinc oxide from hazardous waste - Sal Ammoniac Skimming

Abstract

This article deals with hydrometallurgical treatment with the subsequent precipitation of zinc from hazardous waste Sal-Ammoniac Skimming produced in wet hot-dip galvanizing process. Chemical analysis showed that skimming contained 46.64% Zn. X-ray diffraction analysis identified the Zn(OH)Cl phase (96.36%) and NH 4 Cl (3.64%) in Sal-Ammoniac Skimming. The skimming was first subjected to leaching in order to extract zinc into the solution containing HCl, followed by precipitation of the zinc. The experiments were performed in a medium of HCl at concentrations of 0.25, 0.5, 1 and 2M. Complete dissolution of zinc was achieved in 0.5M HCl solution, at 40°C, L:S=20, max. 30 min. The apparent activation energy of leaching reaction by hydrochloric acid solution was Ea=5.543 kJ mol -1 . Zn precipitation was carried out using Na 2 CO 3 and NaOH. Zinc oxide with a purity of about 99% was obtained directly from the solution of 6M NaOH at a temperature of 60°C -80°Cat pH 8.8. ApstraktOvaj rad se bavi hidrometalurškim postupkom sa naknadnim taloženjem cinka iz opasnog otpada, odnosno pene amonijum hlorida nastale tokom postupka toplog cinkovanja u vlažnim uslovima. Hemijska analiza je pokazala da pena sadrži 46,64% cinka. Rentgenskom difrakcijom je ustanovljeno postojanje dve faze u peni amonijum hidroksida, faza Zn(OH)Cl (96.36%) kao i faza NH4Cl (3.64%). Pena je najpre lužena da bi se izdvojio cink u rastvoru HCl, da bi nakon toga došlo do taloženja cinka. Eksperimenti su izvedeni u prisustvu HCl, pri koncentracijama 0,25, 0,5, 1 i 2M. Potpuno razlaganje cinka je postignuto u rastvoru HCl koncentracije 0,5M, na 40°C, u odnosu T:Č=20, u periodu od maksimalno 30 min. Dobijena energija aktivacije reakcije luženja u prisustvu hlorovodonične kiseline iznosila je Ea=5.543 kJ mol-1. Taloženje cinka je postignuto u prisustvu Na2CO3 i NaOH. Cink oksid, čistoće 99%, dobijen je direktno iz rastvora 6M NaOH na temperaturi od 60°C -80°C pri pH vrednosti 8,8.

Utilization of Galvanizing Flue Dust Residue: A Sustainable Approach towards Complete Material Recycling

“…Therefore, it is necessary to look for other secondary sources with a high zinc content and to increase the EOL-RIR. The industries producing waste containing zinc include the hot-dip galvanizing of steel [8][9][10][11], secondary copper production [12,13], steel production in electric arc furnaces [14], and zinc batteries [15].…”