The use of electric arc furnace dust for treating wastewater from the galvanizing process

The objective of our work was to isolate zinc from electric arc furnace dust using the procedure of alkaline extraction with strong sodium hydroxide base and high neutralization/coagulation effect of the remaining alkaline solid residue for treating acidic industrial wastewater. The possibility of sludge regeneration was also tested using the procedure of alkaline zinc extraction and the application of the remaining solid residue for treating acidic wastewater. To this end, seven samples of composite electric arc furnace dust from the Sisak steel mill with zinc content ranging from 5.71% to 28.18% were used. By means of alkaline extraction, between 62.4 and 84.6% zinc was isolated. The composition of eluate from the remaining solid residue met the criteria for disposal at inert waste disposal sites. Its use in treating wastewater from the galvanizing process in optimal conditions (pH = 8; t(con) = 20 min.) removed between 99.17% and 100% of heavy metals, thus achieving the concentration values of elements suitable for discharge into the environment. The sludge was regenerated by zinc isolation using alkaline extraction while the remaining solid residue was successfully reused for treating acidic wastewater with a similar removal efficiency as in the previous experiment.