Selenium removal from mining and process wastewater: A systematic review of available technologies

Selenium is an important element that is required for humans, animals, plants and other life forms. Selenium is naturally present in the Earth's crust and its worldwide distribution has led to complex interactions between selenium and the natural environment (water, soil, sediments and air). The discharge of selenium contaminated water into the environment from industrial processes is a topic of regulatory (WHO – 40 μg/L, EU – 10 μg/L), environmental and health concern. The removal of selenium from water is complex, determined by its speciation and often expensive due to the characteristics of the wastewater and the stringent discharge limits for selenium and its oxyanions. In this review, selenium chemistry and its toxic effects on human health and the environment have been examined. An overview of the different physico-chemical and biological technologies used for the removal of selenium from contaminated water were discussed wherein adsorption capacities in the range of 0.22–120 mg/g and 0.135–127 mg/g, respectively, were reported in the literature. The challenges and future research directions in this progressive research field have also been stated.