Effects of metal ions and pH on ofloxacin sorption to cassava residue-derived biochar

In this study, the impacts of various cations, cation strength and pH on ofloxacin (OR) adsorption to cassava residue-derived biochars were determined. The associated adsorption mechanisms are discussed. The biochars were prepared at pyrolysis temperatures ranging from 350 degrees C to 750 degrees C, and labeled as CW350, CW450, CW550, CW650 and CW750. The Freundlich model provided the best In to describe the adsorption capacity of OR and the Freundlich coefficient (logF(f)) increased with increasing pyrolysis temperature. The inclusion of Zn2+ or Al3+ increased OFL sorption capacities of five biochars, while Cu2+ reduced sorption to CW450 and CW550. No significant impacts on OFL sorption were observed in the presence of K+ and Ca2+ The concentration of Ca2+ affected the adsorption capacity of CW550, but had no significant impact on other biochars. The pH of OR solution, ranging from 3 to 9, had no significant changes on OR adsorption by all the tested biochars. Results of FTIR spectra and zeta potential indicated that electrostatic interactions, cationic exchange, metal bridging and micropore filling could be the main sorption mechanism between OR and biochars. These studies indicated that cassava residue can be converted into biochars that are effective adsorbents for removing OR from aqueous solution. (C) 2017 Elsevier B.V. All rights reserved.