Modification of bituminous coal by air oxidation to increase ammonia capture

The development of low-cost animal bedding materials for ammonia (NH3) mitigation in livestock facilities is highly desirable from both environmental and waste management perspectives. In this study, we developed an air oxidation method as a simple but effective approach to increase the NH3 adsorption capacity of relatively ubiquitous bituminous coal (BC). The BC samples were oxidized in air at a range of temperatures, from 100 to 550 °C, and the highest NH3 adsorption was observed from the BC modified at 300 °C, with an 11-fold increase (49.7 mg g−1) compared with the initial BC. Samples were characterized using microscopy, BET, FT-IR, XPS, and Boehm titration. The results indicated that NH3 adsorption was dominated by the acidic surface functional groups generated by air oxidation. Ammonium ion (NH4+) adsorption was described by the Langmuir adsorption isotherm and the modified BC retained 5 times more NH4+ than the initial BC. These findings provide insights for the modification of coal materials for the capture of NH3 by simple air oxidation and show promise for future utilization of modified BC for mitigation of NH3 emissions from intensive livestock systems.