Purified bentonite from Nador, Morocco: A sustainable adsorbent for caffeine removal from aqueous solutions

Abstract

Bentonite, primarily composed of montmorillonite, is an abundant clay with advantageous physical and chemical properties, such as small particle size, high surface area, significant porosity, and impressive adsorption capacity. These attributes position it as an auspicious material for the elimination of emerging pollutants, particularly caffeine, which poses serious ecological and health risks. This study focuses on the purification of clay from the Nador region in Morocco to assess its efficacy in eliminating caffeine from aqueous solutions. Through a mineralogical analysis via X-ray Diffraction (XRD), we ensured the successful purification of the clay. Experimental tests showed an adsorption percentage of 60% for raw bentonite (299mg/g), rising to 70% for purified bentonite (338 mg/g), subsequent adsorption experiments explored the influences of temperature, pH, initial pollutant concentrations, and adsorbent mass, on caffeine removal efficiency. Notably, the results revealed an enhanced caffeine adsorption rate in acidic conditions, aligning with the Freundlich isotherm model, while the adsorption kinetics fit well with the pseudo-second- order model. These findings highlight bentonite's potential as a cost-effective and environmentally sustainable sorbent, offering a viable solution to address the growing concern of caffeine contamination in water sources and contributing to the preservation of aquatic ecosystems.