Salinity influences biosorption of heavy metals by the roots of the halophyte plant species Kosteletzkya pentacarpos

Abstract

Dry powder of the roots from the wetland halophyte species Kosteletzkya pentacarpos grown in the presence or in the absence of 50mM NaCl was used for biosorption of Cd and Zn. Experiments were performed in batch conditions using 100mg of root powder and 10mL of contaminated solution. Optimal temperature was found to be 25°C and contact time of 15min was sufficient for maximal adsorption. Sorption efficiency was higher for Cd (88.8%) than for Zn (56.9%). The maximal adsorption value qm was 10.6μmolesg−1 DW for Cd and 7.98μmolesg−1 DW for Zn. The use of roots collected from plants grown for 16 weeks in the presence of NaCl improved sorption process, especially for Zn. This positive impact could be related to the salt-induced increase in mucilage pectic compounds and hemicellulose involved in heavy metal binding. In contrast, the presence of NaCl during the biosorption incubation reduced sorption efficiency as a result of a competition between Na+ and divalent cations for binding sites. Removal of the majority of pollutant was obtained by 0.2M (Cd) or 0.3M (Zn) HCl. It is concluded that roots of K. pentacarpos provide a valuable biological material for heavy metal retention.