Reduction and Removal of Cr(VI) from Aqueous Solution by Microplasma
In this chapter, the reduction and removal of Cr(VI) from aqueous solution by microplasma are explained, which represents a new and fascinating realm of plasma science for the first time. The effect of various process parameters on the Cr(VI) reduction ef
- PDF / 761,741 Bytes
- 19 Pages / 439.37 x 666.142 pts Page_size
- 70 Downloads / 195 Views
Reduction and Removal of Cr(VI) from Aqueous Solution by Microplasma
Abstract In this chapter, the reduction and removal of Cr(VI) from aqueous solution by microplasma are explained, which represents a new and fascinating realm of plasma science for the first time. The effect of various process parameters on the Cr(VI) reduction efficiency and the effect of initial pH and ethanol on the removal of Cr(VI) are systematically examined. The optimum condition for Cr(VI) reduction was initial pH at 2 with stir where the microdischarge gas was argon with the flow rate of 60 mL/min. The reduction efficiency of Cr(VI) increased with an increase in input power but decreased with an increasing initial concentration of Cr (VI). In particular, additive hydroxyl radical scavenger (ethanol) greatly improved the reduction efficiency and facilitated the removal of chromium dissolved in the solution. The best removal efficiency was obtained when the pH was 6. In addition, the energy efficiency of microplasma to reduce Cr(VI) is 2.0 10−4 mg/J and is comparable to that in electrolysis and other forms of glow discharge. The advantages, such as low cost, scalability, and easy operating techniques, of this approach have broad prospects in water treatment (Xiao in Removal of hexavalent chromium in water and preparation of cuprous oxide nanoparticles by microplasma. Yat–sen University, 2012, [1]; Du in Non-Thermal arc plasma technology and application. BeiJing: Chemical Industry Press, 2015, [2]. Keywords Microplasma
4.1
Chromium(VI) Reduction Removal Mechanism
Introduction
Chromium exists in large amounts in the wastewaters of leather tanning, pigment and fertilizer productions, electroplating, metallurgy, and other industries. Although Cr can exist in oxidation states ranging from Cr(II) to Cr(VI), trivalent chromium
© Zhejiang University Press, Hangzhou and Springer Natue Singapore Pte Ltd. 2017 C. Du and J. Yan, Plasma Remediation Technology for Environmental Protection, Advanced Topics in Science and Technology in China, DOI 10.1007/978-981-10-3656-9_4
41
42
4 Reduction and Removal of Cr(VI) from Aqueous Solution …
(Cr(III)) and hexavalent chromium (Cr(VI)) are the most dominant oxidation states in the natural environment [1]. Cr(III) is an essential nutrient at trace level and has lower solubility in water. In contrast, Cr(VI) is highly toxic, mutagenic, and potentially carcinogenic to living organisms [3]. Therefore, it is necessary to reduce Cr(VI) to Cr(III) with subsequent immobilization as hydroxide when disposing Cr (VI)-contaminated wastewater [4]. Current technologies for treatment of Cr(VI)-containing wastewaters include ion exchange, reduction, adsorption, membrane separation, solvent extraction, and electrodialysis [5–12]. Among them, the conventional method of reduction using chemicals, such as sulfur dioxide or sodium metabisulfite, is easy to implement but produces additional pollution due to the ultra use of reducing chemicals and the production of poisonous by-products [13]. Adsorption is another widely
Data Loading...
