Study on the efficient removal of clopyralid from water using a resorcinol-formaldehyde carbon cryogel

A resorcinol-formaldehyde carbon cryogel was prepared, characterized and used for the removal of the commonly used herbicide clopyralid from aqueous solutions under varying experimental conditions. The carbon exhibited a relatively high specific surface area, significant mesoporosity and an amorphous structure. The following isotherm models were used to interpret the equilibrium data: the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Jovanovic, Hurkins-Jura and the Helsey Model. Several models fitted the data well although the calculated values for q(max) poorly correlated with the experimentally obtained data. The pseudo-first and pseudo-second-order kinetic models, the models of Elovich, Bangham and the intraparticle diffusion model were employed for fitting the kinetic data. The rate of the process was fast at the beginning, although the adsorption equilibrium was not attained before 24 h. The adsorption was found to be pH dependent and favored in acidic solutions.