Ash Activation as a Means of Improving Biochars for Aqueous Removal of Organic Contaminants

Biochar, a low-cost alternative to activated carbon, is produced through pyrolysis of waste biomass and is effective in the removal of organic contaminants in water treatment systems. In this study, pelletized pine biochars were prepared through a novel “ash activation” process to improve sorption of organic contaminants. The objective of this study was to compare ash activated biochars to regular biochars and activated carbon to evaluate the improvement in sorption gained through ash activation as well as the optimal production conditions for this process. Pine and sewage-sludge feedstocks were saturated with pine- and sludge-ash water and pyrolized at temperatures ranging from 400 to 850 °C to produce the biochars for this study. Our results showed that ash activated biochars showed an overall increase in sorption of the target compounds compared to regular biochar. The efficacy of ash activated biochar to sorb the target compounds neared that of commercial activated carbon at relevant dosages and in natural waters, while regular biochar sorbed only a small fraction. Our results suggest that ash activation is an effective method to increase sorption of organic contaminants in water treatment scenarios. Ash activation of biochar has the potential to lower costs for water utilities by providing an alternative to activated carbon that is similar in efficacy and simple to manufacture. In addition, biochar is being used in developing communities to remove organic contaminants from drinking water sources, and these findings could be used to improve biochars produced in the developing world through a single simple, and affordable preparation step. Finally, this novel ash activation process could have broad impacts across biochar applications in agriculture, water, energy, and the environment.