Investigation of humic acid extraction possibility from Arguvan-Parcikan (Malatya) lignite

In this study, the extraction of humic substances from low-quality lignite samples obtained from Arguvan (Malatya) coal deposit was investigated by the California Department of Food and Agriculture (CDFA) method. The ideal conditions, in which the highest yield of humic acid was obtained, were found to be alkaline concentration 0.5 M, liquid/solid ratio 20 mL/g, leaching temperature 75 °C, leaching time 4 hour. In leaching experiments, raw coal (i.e. unwashed coal) sieved in different particle size and washed coals with different specific gravities obtained from float-sink test were used. Each coal sample was individually leached in alkaline media prepared using NaOH, KOH and Na4P2O7. Then, % humic acid of coal samples was determined by precipitation of humic acid from leach solution. In addition, the highest humic acid yield was achieved as x result of Na4P2O7 leaching. The humic acids obtained from leaching tests were characterized by elemental analysis and FTIR spectrometry. According to the experimental results, the highest humic acid yield for raw coal was reached by leaching of coal in the particle size of -4.75+2.36 mm. However. When the highest humic acid yield was 13.13% for raw coal in the particle size of-10 + 4.75 mm, humic acid yield of washed coal in the specific gravity of 1.5-1.6 g/cm3 obtained from the same size coal increased to 16.23%. Finally, it was concluded that coal washing had a positive effect on humic acid extraction. KEYWORDS: Lignite, coal washing, alkaline leaching, humic acid, elemental analysis, FTIR