Leaching optimization of municipal solid waste incineration ash for resource recovery: A case study of Cu, Zn, Pb and Cd. (February 2016)

• Record Type: Journal Article
• Authors: Tang, Jinfeng; Steenari, Britt-Marie
• Is Part Of: Waste management. Volume 48(2016)
• Page Start: 315
• Page End: 322
• Publication Date: 2016-02
• Subjects: MSWI ash -- Acidic leaching -- Copper -- Zinc -- Lead -- Cadmium -- Hazardous metals -- Waste treatment; Hazardous wastes -- Periodicals; Refuse and refuse disposal -- Periodicals; 363.728
• DOI: 10.1016/j.wasman.2015.10.003
• Languages: English
• ISSNs: 0956-053X

Abstract

Highlights: Acid leaching was evaluated as a first step in a process to recover Cu and Zn. Leaching with hydrochloric acid at pH 2 gave a yields of Cu (>75%) and Zn (>80%). It removed a significant part of Pb (>90%) and Cd (>90%) from the fly ash as well. Acid leaching of the bottom ash was not feasible due to gel formation. Abstract: Ash from municipal solid waste incineration (MSWI) may be quite cumbersome to handle. Some ash fractions contain organic pollutants, such as dioxins, as well as toxic metals. Additionally, some of the metals have a high value and are considered as critical to the industry. Recovery of copper, zinc and lead from MSWI ashes, for example, will not only provide valuable metals that would otherwise be landfilled but also give an ash residue with lower concentrations of toxic metals. In this work, fly ash and bottom ash from an MSWI facility was used for the study and optimization of metal leaching using different solutions (nitric acid, hydrochloric acid and sulfuric acid) and parameters (temperature, controlled pH value, leaching time, and liquid/solid ratio). It was found that hydrochloric acid is relatively efficient in solubilizing copper (68.2 ± 6.3%) and zinc (80.8 ± 5.3%) from the fly ash in less than 24 h at 20 °C. Efficient leaching of cadmium and lead (over 92% and 90% respectively) was also achieved. Bottom ash from the same combustion unit was also characterized and leached using acid. The metal yields were moderate and the leachates had a tendency to form a gelatinous precipitate, which indicates that the solutions were actually over-saturated with respect to some components. This gel formation will cause problems for further metal purification processes, e.g. solvent extraction.