2,4-D adsorption to biochars: Effect of preparation conditions on equilibrium adsorption capacity and comparison with commercial activated carbon literature data

Batch isotherm experiments were conducted with chars to study adsorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Chars generated from corncobs, bamboo and wood chips in a laboratory pyrolyzer at 400-700 °C were compared with traditional kiln charcoals collected from villages in S/SE Asia and with activated carbons (ACs). 2,4-D uptake by laboratory chars obtained from bamboo and wood chips after 14 h of pyrolysis at 700 °C, from wood chips after 96 h of pyrolysis at 600 °C, and one of the field-collected chars (basudha) was comparable to ACs. H:C and O:C ratios declined with pyrolysis temperature and duration while surface area increased to >500 m2/g. Increasing pyrolysis intensity by increasing temperature and/or duration of heating was found to positively influence adsorption capacity yield (mg2,4-D/gfeedstock) over the range of conditions studied. Economic analysis showed that high temperature chars can be a cost-effective alternative to ACs for water treatment applications.