Demineralization of Enugu coal: effect of acid type and acid concentration

Abstract

Demineralization of Enugu Coal with HCl, H₂S0₄, HN0₃, HF and H₃P0₄ under different conditions such as leaching time, particle size, acid concentration and leachant volume was investigated in this study. The filtrate from each treatment was analyzed with Atomic Absorption X-ray Spectrophotometer (AAS) to determine the amount of metals (Pb, Cr, Cd, Ar, and Hg) leached. Similarly, the residual coal from each treated sample was also analyzed together with virgin coal using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrophotometer (EDAX), X-ray Fluorescence (XRF), and Fourier Transform Infrared Spectrophotometer (FTIR). Lithophiles like aluminum and silicates revealed by EDAX and Micrograph of virgin coal was found to be absent in residual coal, which is an indication of demineralization. Proximate analysis of coal ash after acid treatments showed that the ash content decreased with increase in acid concentration. XRF results showed that SiO₂, Al₂O₃, and Fe₂O₃ are the dominant minerals in coal ash. Statistical analysis at$P<0.05$ showed that leaching leaching of trace elements depend on the leaching time, acid type, acid concentration, particle size and leachant volume. Results of the investigation revealed that HNO₃ mostly influenced the removal of trace elements from Enugu coal.

Keywords:

• Leaching
• coal
• trace metals; virgin coal; residual coal

Acknowledgments

The author wish to thank in a special way, Projects Development Institute (PRODA), Enugu, Nigeria and the Department of Chemistry, Ahmadu Bello University, Zaria, Nigeria for making their Laboratories and equipments available for the experiments. Also we thank Prof. P.K. Igbokwe of the department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria for Supervising the work.

Disclosure statement

No potential conflict of interest was reported by the authors.