Electrochemical Evaluation of Selenium (IV) Removal from Its Aqueous Solutions by Unmodified and Modified Graphene Oxide.

Zuzana Koudelkova,Kledi Xhaxhiu,Monika Kremplova,Lukas Richtera,Zuzana Bytesnikova,David Hynek,Vojtech Adam

doi:10.3390/molecules24061063

Abstract

The removal of selenium from superficial and waste water is a worldwide problem. The maximum limit according to the World Health Organization (WHO) for the selenium in the water is set at a concentration of 10 μg/L. Carbon based adsorbents have attracted much attention and recently demonstrated promising performance in removal of selenium. In this work, several materials (iron oxide based microparticles and graphene oxides materials) and their composites were prepared to remove Se(IV) from water. The graphene oxides were prepared according to the simplified Hummer’s method. In addition, the effect of pH, contact time and initial Se(IV) concentration was tested. An electrochemical method such as the differential pulse cathodic stripping voltammetry was used to determine the residual selenium concentration. From the experimental data, Langmuir adsorption model was used to calculate the maximum adsorption capacity. Graphene oxide particles modified by iron oxide based microparticles was the most promising material for the removal of Se(IV) from its aqueous solution at pH 2.0. Its adsorption efficiency reached more than 90% for a solution with given Se(IV) concentration, meanwhile its maximal recorded adsorption capacity was 18.69 mg/g.

Highlights

Increasing concentrations of metals and metalloids in the environment still represent a threat to biota, whereas bioremediation and/or physico-chemical cleaning of various water sources are challenging issues [1,2,3]
This study sheds light on removal of Se(IV) from its aqueous solutions using different composite materials based on graphene oxide (GO) and their modifications with MPs
9.35 adsorption efficiency was over 93% in a of Se(IV) solution with initial concentration of 5 μg/mL within

Summary

Introduction

Increasing concentrations of metals and metalloids in the environment still represent a threat to biota, whereas bioremediation and/or physico-chemical cleaning of various water sources are challenging issues [1,2,3]. Selenium belongs to essential metalloids, its unique features lay within a very thin line between essentiality and toxicity [4,5]. Selenium occurs in both organic and inorganic forms. The organic forms of selenium include amino acids selenomethionine and selenocysteine. Inorganic forms include these oxidation states: Selenite (SeO3 2− ), selenide (Se2− ), selenate (SeO4 2− ), and elementary selenium (Se0 ) [6,7]. Selenium, with respect to its oxidation state and form, plays an important role in numerous biological processes and biochemical pathways, such as maintaining antioxidant homeostasis, formation of thyroid hormones, Molecules 2019, 24, 1063; doi:10.3390/molecules24061063 www.mdpi.com/journal/molecules

Objectives

Results

Conclusion