A novel treatment for Cd-contaminated solution through adsorption on beech charcoal: the effect of bioactivation

In this paper, biochar produced by pyrolysis of beech has been investigated as a potential adsorbent for remediation of cadmium-contaminated groundwater. The experimental activity included determination of the main physical–chemical characteristics of charcoal and the study of the adsorption kinetics and isotherms through batch tests. Adsorption column tests were also carried out and breakthrough curves determined. The same tests were repeated using the beech charcoal after the addition of specific bacterial strains able to produce a reactive monolayer biofilm. The results showed that both charcoal and bioactivated charcoal (biocharcoal) are effective adsorbents for Cd at initial concentration of 25 mg/L, with the latter providing slightly better performance. The pseudo-secondorder model provided the best fitting of the kinetic data of both media, with the following values of the constants: qe = 0.600 mg/g and ks = 0.395 g/mg min for charcoal, and qe = 1.409 mg/g and ks = 0.061 g/mg min for biocharcoal, where qe and ks stand for the equilibrium adsorption capacity and the constant rate, respectively. Among the isotherm models, the Langmuir equation provided the best fitting of the experimental data for both charcoal and biocharcoal. The maximum adsorption capacity of biocharcoal was found to be about four times higher than that of charcoal (3.2 and 0.8 mg/g, respectively).