Thesis Archive
The Leachability of Chromium from Coal Ash Using Serial Batch Leaching Procedure (2011)
Ronquillo, Ria Joan K.
Salido, Beatrice Mari M.
Abstract:
-“Fly and bottom ash samples were obtained from a local coal-fired power plant which utilizes the use of Indonesian and Semirara coal. The general aim of this study was to determine the average leaching rate of Chromium from the samples using the Serial Batch Leaching Procedure or SBLP was carried out in the experiment. SBLP has the advantage of estimating the heavy metal release from alkaline ashes, unlike other leaching procedures which mostly assess acidic ashes. Initial heavy metal analysis of the raw ash samples showed that the only detectable heavy metals are Arsenic and Chromium. From the preliminary run, only chromium was detected. Sulfuric acid, a strong oxidizing agent, was used to vary the initial pH of the leachant to 2, 5 and 8. Together with pH, the other parameters used were liquid-to-solid ratio (2, 3.5 & 5) and contact time (8, 16 & 24 hrs). Atomic Absorption Spectrophotometry analysis was performed to determine the elemental concentration of Chromium present in the ash samples and results obtained were then used to calculate for the leaching rate under varying parameters. X-ray Diffraction analysis and BET method were done for the determination of the mineralogical content and specific surface area, respectively.
Results from the different runs showed Semirara fly ash has the highest average leaching rate which reached up to 0.0698ppm/g-hr at maximum contact time of 24 hours, leachant pH of 8 and L/S ratio of 3.5. It was then followed by the Indonesian fly ash with an average leaching rate of 0.06063ppm/g-hr, Semirara bottom ash with an average leaching rate of 0.0591ppm/g-hr and Indonesian bottom ash with an average leaching rate of 0.0542ppm/g-hr. From the mean effect plot of the Taguchi analysis, it was found out that pH had the highest effect on the rate of leaching of Chromium. Rate of leaching with respect to the pH was found to be lowest at pH 5 and highest at pH 8. An increasing trend for L/S ratio and contact time was also seen for increasing parameter levels.”
Adviser:
Susan M. Gallardo