Calcium-Doped Biochar for Optimized Glyphosate Removal in Aqueous Media

Overview

Biochar has been shown to effectively adsorb glyphosate, a widely used herbicide frequently detected in aquatic environments. This study aimed to optimize the glyphosate adsorption capabilities of biochar in aqueous media through calcium amendments. Biochar was prepared by using recycled aluminum cans to create a TLUD (top-lit updraft) gasifier, and dried wheat straw was used as a substrate for further modification. Two biochar variants were created: one consisting solely of wheat straw (BC), and the second soaked in a calcium acetate solution derived from acetic acid and egg shells prior to pyrolysis (CaBC). UV/Vis spectrophotometry revealed that BC and CaBC removed 81% and 93% of glyphosate, respectively. Kinetic models for CaBC fit both a pseudo-second order and pseudo-second order profile, suggesting a complex adsorption mechanism dependent on both chemisorption and physisorption. However, when data for BC was mapped to the same kinetic models, BC had a significantly lower correlation coefficient towards the pseudo-second order model, indicating limited chemisorption. Moreover, CaBC isotherm studies exhibited high correlation coefficients for both Langmuir and Freundlich models, further suggesting a mixed adsorption mechanism. FTIR characterization for CaBC yielded peaks at 721 cm-1, indicative of Ca-O bonds. Furthermore, these peaks were not visible post-adsorption, suggesting that the Ca-O bonds were replaced with interactions between Ca2+ ions, OH-, and glyphosate. This research demonstrates the viability of biowaste-derived, calcium-modified biochar as a promising material for water remediation applications.