Elemental Changes of Wahau Low-Rank Coal after Hydrogen Peroxide Pretreatment: Implications for Coal Bioavailability

Abstract

Low-rank coal contains abundant oxygen-bearing and aliphatic structures that can be chemically modified under mild oxidative conditions. However, the significance of small elemental shifts for subsequent biological utilization remains insufficiently constrained. This study evaluates elemental changes in Wahau low-rank coal after mild hydrogen peroxide (H2O2) pretreatment while keeping particle size uniform. A 100-mesh coal fraction was evaluated in three states: raw coal, ultrapure-water control, and coal treated with 0.3% H2O2. Carbon, hydrogen, and oxygen contents were interpreted together with atomic H/C and O/C ratios. Compared to the water control (O/C=0.200, H/C=0.941; raw coal: O/C=0.203, H/C=1.108), H2O2 treatment increased O/C to 0.222 while leaving H/C virtually unchanged at 0.944. The shift is consistent with mild oxygenation or oxidative modification of the coal matrix rather than a simple change in carbon abundance. Comparison with published H2O2 studies on lignite, sub-bituminous, bituminous, and anthracitic coals indicate that oxygenation commonly accompanies structural modification. However, the extent and biological consequences depend strongly on coal rank and treatment severity. These elemental shifts indicate increased matrix polarity and potential microbial accessibility rather than direct bioconversion.