Biochars as a Solution for Silver Removal and Antimicrobial Activity in Aqueous Systems

The objective of this research was to investigate silver adsorption on biochars prepared by the carbonization of desiliconized rice husks and cotton fabric, and to elucidate the adsorption mechanism. The biochars were characterized using various instrumental techniques, including thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and low-temperature nitrogen adsorption. The adsorption process was studied under multiple parameters affecting silver adsorption and was best described by the pseudo-second-order kinetic model. Both the Langmuir and Freundlich isotherm models provided good correlations for the adsorption of silver ions onto the biochars. Thermodynamic analysis indicated that the adsorption of Ag+ ions was spontaneous and exothermic. XPS confirmed the presence of metallic silver (Ag0) in the biochars RHB and ARHB, suggesting that a reduction process occurred during silver adsorption. Additionally, in vitro studies were conducted to evaluate the antimicrobial activity of silver-loaded activated rice husk biochar against E. coli strains.