The adsorption potential and recovery of thallium using green micro-algae from eutrophic water sources

Thallium (T1) is a highly volatile and toxic heavy metal regarded to cause pollution even at very low concentrations of several parts per million. Despite the extremely high risk of T1 in the environment, limited information on removal/recovery exists. The study focussed on the use of green algae to determine the sorption potential and recovery of T1. From the study, removal efficiency was achieved at 100% for lower concentrations of >= 150 mg/L of T1. At higher concentrations in a range of 250-500 mg/L, the performance of algae was still higher with sorption capacity (q(max)) between 830 and 1000 mg/g. Generally, Chlorella vulgaris was the best adsorbent with a high q(max) and lower affinity of 1000 mg/g and 1,11 L/g, respectively. When compared to other studies on T1 adsorption, the tested algae showed a better q(max) than most adsorbents. The kinetic studies showed better correlation co-efficient of <= 0.99 for Pseudo-second order model than the first order model. Recovery was achieved highest for C. vulgaris using nitric acid at 93.3%. The strongest functional groups responsible for T1 binding on the algal cell wall were carboxyl and phenols. Green algae from freshwater bodies showed significant potential for T1 removal/recovery from industrial wastewater. (C) 2015 Elsevier B.V. All rights reserved.