This study proposes the utilization of CO2 based on the purification of landfill gas (LFG). The process included absorption of CO2 from LFG using monoethanolamine (MEA) absorbent, extraction of calcium ions from municipal solid waste incineration (MSWI) fly ash using various acids, and formation of calcium carbonate using the extracted calcium ions. During LFG purification, the concentration of CH4 in the gas after absorption was time dependent. The pH swing method was used for the extraction of calcium ions and comprised three phases: calcium ion leaching from MSWI fly ash phase, removal of cations from the supernatant, and calcium ion recovery. Hydrochloric and nitric acids, known as strong acids, and citric, acetic, and formic acids, which are weak acids, were used as extraction agents. Hydrochloric acid, nitric acid, acetic acid, and formic acid showed significant calcium ion recovery rates of 99.32%, 99.18%, 98.35%, and 97.99%, respectively, whereas citric acid showed a relatively low recovery rate of 82.82%. The extracted calcium ions were converted into calcium carbonate by reacting with ionic CO2 in the saturated MEA. The calcium carbonate formed showed different crystal structures based on the extraction agent used: aragonite for hydrochloric acid and nitric acid, amorphous CaCO3 for citric acid, vaterite for acetic acid, and calcite for formic acid. The results of this study can be applied to various CO2 utilization processes based on LFG and MSWI fly ash.
Bibliographical noteFunding Information:
This study was supported by the Korea South-East Power Co. (No. 2020-KOEN (Yeongdong)-02 ) and Korea Environment Industry & Technology Institute (KEITI) through Project to develop eco-friendly new materials and processing technology derived from wildlife Project, funded by Korea Ministry of Environment (MOE) ( 2021003280002 ).
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal