Adsorption of chromium species from industrial effluent using magnesium-bentonite clay composite: kinetics, equilibrium and risk assessment study

Abstract

To counter for pollution hazards imposed by anthropogenic activities on the environment, government, national and international scientific communities are in a quest to find pragmatic chromium depollution techniques. More prevalently, chromium enriched effluents emanate from mining, electroplating, leather tanning, chromite beneficiation, fertilizer and several other industries, thus, posing serious environmental problem when introduced to aqueous environments (Yu and Zhang, 2014, Zewail and Yousef, 2014, Zhang and Huang, 2014, Zhang et al., 2014). Both natural and human activities contribute to the introduction of chromium into the environment (Baral and Engelken, 2002, Ghorbel-Abid et al., 2009, Fabbricino et al., 2013, Zuo and Balasubramanian, 2013). It mainly exists as an oxyanion at circumneutral to basic pH conditions (Sultana et al., 2014). The species of concern are although inorganic chromium can exist in a range of valence states from 2+ to 6+, Cr (III) and Cr (VI) are the most common oxidation states. Chromium (III) and chromium (VI) are species of main environmental concern. They are interchangeable in the natural environment, depending on the pH and redox potential of the medium and the presence or absence of a strong oxidant or reductant (Rengaraj et al., 2001, Peng et al., 2014, Rangasamy et al., 2014, Saha and Saha, 2014).