Characteristics of humic acids of Mukah coal in Sarawak

In Malaysia, abundant coal resources were found in Sarawak and Sabah. The utilization of coal resources, to date, is emphasized on the energy productions. The non-energy utilization as soil conditioner is unexplored. Therefore, this study attempted to characterize the coal humic acids extracted from Mukah coal and to evaluate its properties as soil conditioner. The coal humic acids from the regenerated sample were also assessed. The results revealed that different extractants, concentrations, mesh size and temperature influenced the properties of humic acids. The extraction with KOH at 0.5 M produced humic acids with low ash content and high acidic functional groups, which are substantial as soil conditioner. However, the essential yield was low (20%). Regeneration of coal sample with 10% nitric acids improved the yield to an average of 83.45%. The acidic functional groups of nitrohumic acids were improved with the ash content remained at a low level. The UV-VIS study revealed no significant difference on the humification degree of humic acids prepared with varying treatments. Nevertheless, the nitration process was found to result in humic acids with higher condensation level.