Biochar-ion interactions: an investigation of biochar charge and its effect on ion retention.

The method of measuring exchangeable cations as an approximation for cation exchange capacity was examined using a cow manure and green waste biochar. Both biochars were pre-treated by shaking with water over a range of times. Leachates were analysed, and the pre-treated biochars were then treated with two solutions (0.1M BaCl 2 or 0.1M CsCl) to measure ion adsorption. Pre-treatment shaking had a significant effect on ion adsorption for both biochars. Ion adsorption for the green waste biochar was significantly increased with pre-treatment shaking, whereas it decreased for the cow manure biochar. Compulsive exchange of cations to determine the ability of a substrate to retain positively charged ions on its surface may not be an appropriate method for biochar.