A critical analysis of sources, pollution, and remediation of selenium, an emerging contaminant

Abstract

Selenium (Se) is an essential metalloid and is categorized as emerging anthropogenic contaminant released to the environment. The rise of Se release into the environment has raised concern about its bioaccumulation, toxicity, and potential to cause serious damages to aquatic and terrestrial ecosystem. Therefore, it is extremely important to monitor Se level in environment on a regular basis. Understanding Se release, anthropogenic sources, and environmental behavior is critical for developing an effective Se containment strategy. The ongoing efforts of Se remediation have mostly emphasized monitoring and remediation as an independent topics of research. However, our paper has integrated both by explaining the attributes of monitoring on effective scale followed by a candid review of widespread technological options available with specific focus on Se removal from environmental media. Another novel approach demonstrated in the article is the presentation of an overwhelming evidence of limitations that various researchers are confronted with to overcome achieving effective remediation. Furthermore, we followed a holistic approach to discuss ways to remediate Se for cleaner environment especially related to introducing weak magnetic field for ZVI reactivity enhancement. We linked this phenomenal process to electrokinetics and presented convincing facts in support of Se remediation, which has led to emerge 'membrane technology', as another viable option for remediation. Hence, an interesting, innovative and future oriented review is presented, which will undoubtedly seek attention from global researchers.

Keywords: Bioremediation; Contamination; Remediation technology; Selenium; Waste water.

Fig. 1

Speciation diagrams of selenite [SeO₃²⁻, Se(IV)] and selenate [SeO₄²⁻, Se(VI)] as a function of pH; conditions: zero ionic strength at 25 °C, and 1 bar pressure. Reproduced with the permission of Sharma et al., (2018)

Fig. 2

Characteristics and appearance of selenium

Fig. 3

Global annual selenium refinery production for different countries across the world (1996–2020). Adapted and Reproduced with permission from ‘(Ullah et al., 2018a, b, c)’

Fig. 4

Global selenium cycle in nature. Reproduced with the permission of ‘(Nancharaiah & Lens, 2015a, b)

Fig. 5

Various types of phytore-mediation of selenium occurring in plants. Passage and probable fates of selenium in plants. Adapted with the permission of Usmani et al. (2018)

Fig. 6

Adsorption kinetics of Se(IV) by MNP@hematite (a) and MNP core (b) at 25 °C. Initial solution pH 7.0, adsorbent dosage 0.1 g/L. Reproduced with the permission of Ma et al. (2018)