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

Abstract

Thallium (Tl) is a highly volatile and toxic heavy metal regarded to cause pollution even at very low con-centrations of several parts per million. Despite the extremely high risk of Tl in the environment, limitedinformation on removal/recovery exists. The study focussed on the use of green algae to determine thesorption potential and recovery of Tl. From the study, removal efficiency was achieved at 100% for lowerconcentrations of ≥150 mg/L of Tl. At higher concentrations in a range of 250–500 mg/L, the performanceof algae was still higher with sorption capacity (qmax) between 830 and 1000 mg/g. Generally, Chlorellavulgaris was the best adsorbent with a high qmaxand lower affinity of 1000 mg/g and 1.11 L/g, respec-tively. When compared to other studies on Tl adsorption, the tested algae showed a better qmaxthanmost adsorbents. The kinetic studies showed better correlation co-efficient of ≤0.99 for Pseudo-secondorder model than the first order model. Recovery was achieved highest for C. vulgaris using nitric acid at93.3%. The strongest functional groups responsible for Tl binding on the algal cell wall were carboxyl andphenols. Green algae from freshwater bodies showed significant potential for Tl removal/recovery fromindustrial wastewater.