Lignocellulosic Activated Carbon as a Powerful Glyphosate Adsorption Agent in Contaminated Water

One of the main contaminants in water sources is glyphosate, a broad-spectrum, non-selective herbicide whose use has increased due to intensive agriculture in the 21st century. Therefore, this research aims to produce four samples of activated carbon for the adsorption of this contaminant. Initially, corn cob residue was selected as a lignocellulosic precursor and subjected to thermogravimetric analysis (TGA), yielding a fixed carbon content of 58.86% and a low ash content of 14.45%, making it a suitable raw material for obtaining advanced carbonaceous materials. Subsequently, the activated carbon (biocatalytic support) was prepared through the thermochemical process of pyrolysis. Samples AC-TK and AC-TP were produced from raw corn cob residue, while samples AC-CK and AC-CP were produced from corn cob residue carbonized at 450 °C. These activated carbon samples were characterized using FTIR and Raman spectroscopy techniques, revealing bands associated with the presence of oxygenated functional groups, specifically between 3700 and 3100 cm−1 using FTIR. These bands are associated with the vibrations of alcohol and carboxylic acid functional groups, which are important in adsorption processes and act as active sites on the surface of the materials. Two peaks were also obtained near 1345 and 1596 cm−1, corresponding to the D and G bands, using Raman spectroscopy. These peaks are attributed to the disordered carbon structures and all the SP2 sites of graphite. Finally, after experimentation and adsorption tests, samples AC-TK, AC-CK, and AC-CP demonstrated the power to adsorb the contaminant at low glyphosate concentrations, achieving an adsorption of approximately 7.7 mg/g at concentrations below 10 mg/L. This demonstrates the viability of the raw material for glyphosate elimination.