Abstract:
This research was to study the feasibility of using fly ash, which are the waste residues from coal combustion in the electricity generation processes at Mae Mao Power Plant in Lampang Province, to remove zinc in the acidic wastewater from rubber thread manufacturing factory. The experiments included the determination of the optimum fly ash dose for zinc reinoval and neutralization, zinc removal mechanism, and leaching resistant of the sorbed zinc. It was found that zinc sorption by fly ash reached the equilibrium within 24 hours. The optimum fly ash dose for both neutralization and zinc removal was 20 gram per 100 milliliter of wastewater which yielded the maximum sorption capacity of 2.09 milligram zinc per gram fly ash. The reinoval mechanism was proved to be ion exchange adsorption rather than hydroxide precipitation. Preliminary leaching test indicated a little dissolution of the sorbed zinc from the solid phase. Economic analysis showed that the removal of zinc through hydroxide precipitation and pose neutralization will cost roughly 92 baht for chemical expense and generate 7.6 kilograin of sludge. On the other hand, the treatment by fly ash required no chemical; however, will generate approximately 200 kilogram of sorbed residues which will raise substantially the sludge disposal cost compared to that of hydroxide sludge. As p. result, the used of fly ash for zinc removal and neutralization of rubber thread wastewater is considerably uneconomic.