Kinetic and thermodynamic aspects of cadmium adsorption onto raw and activated guava (Psidium guajava) leaves

Guava leaves as raw (GL) and activated Guava leaves (AGL) has been investigated for adsorption of cadmium ions from aqueous solutions. Both adsorbent materials have been characterized using different physicochemical methods. Adsorption kinetics were determined and modeled by rate and diffusion equations. It was found that the removal of cadmium ions is rapid and follows a pseudo second-order model. Empirical models were estimated to predict the amount of cadmium ions adsorbed onto GL and AGL for any given Co and contact time. Various parameters such as diffusion coefficient, activation energy, and thermodynamic parameters were evaluated to establish the mechanisms.