Adsorption of lead onto formaldehyde or sulphuric acid treated acorn waste: Equilibrium and kinetic studies

The adsorption of lead onto formaldehyde or sulphuric acid treated acorn waste was studied using a batch sorber. The aim of this study was to understand the mechanisms that govern lead removal and find a suitable equilibrium isotherm and kinetic model for the lead removal in a batch reactor. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin equations. The equilibrium data fit well the Langmuir isotherm. The experimental data were analyzed using four adsorption kinetic models – the pseudo first- and second-order equations, intraparticle diffusion equation and the Elovich equation – to determine the best fit equation for the adsorption of lead ions onto formaldehyde or sulphuric acid treated acorn waste. The rate constants, equilibrium capacities and related correlation coefficients for each kinetic model were calculated and discussed. Also, predicted qt values from the kinetic equations were compared with the experimental data. Results show that the pseudo second-order equation provides the best correlation for the adsorption process, whereas the Elovich equation also fits the experimental data well.