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In situ Treatment Technologies
Published in Rong Yue, Fundamentals of Environmental Site Assessment and Remediation, 2018
Ferrous iron is an effective reductant. However, when injected alone, ferrous iron will be oxidized to ferric iron and rapidly precipitate out of solution (USEPA 2011b). This precipitation can be prevented by acidifying the solution (USEPA 2000) as Fenton’s reagent (refer to Section 8.1.1.3) or by co-injection with sodium dithionite as a buffer. Sodium dithionite is also a strong reductant conventionally used in the textile and paper industries and in wastewater treatment. An aqueous solution of sodium dithionite is acidic and decomposes to sodium thiosulfate and sodium bisulfite (Lister et al. 1959).
Traditional and innovative methods for physical and chemical remediation of soil contaminated with organic contaminants
Published in Katalin Gruiz, Tamás Meggyes, Éva Fenyvesi, Engineering Tools for Environmental Risk Management – 4, 2019
É. Fenyvesi, K. Gruiz, E. Morillo, J. Villaverde
Sodium dithionite (Na2S2O4) is used for chemical reduction of Fe(III) present in the soil or sediment to Fe(II), providing reducing conditions. The lower redox potential favors both abiotic and biotic reduction of contaminants such as explosives and chlorinated solvents, e.g. TCE (Szecsody et al., 2004). For the treatment of soils not rich in iron, the combined injection of ferrous iron with sodium dithionate is beneficial.
Mao berry as a green reducing agent in natural indigo dyeing on cotton fabrics
Published in The Journal of The Textile Institute, 2022
Laksanawadee Saikhao, Jantip Setthayanond, Thitinun Karpkird, Potjanart Suwanruji
Sodium dithionite (Na2S2O4) is the most important reducing agent used in the reduction of indigo because of its effectiveness and availability in an easily handled form (Blackburn et al., 2009). However, the disadvantages of Na2S2O4 are its low stability, easy oxidation by atmospheric oxygen and detrimental environmental impact. Moreover, the decomposition of Na2S2O4 during the process generates by-products such as sulphate and sulphite ions that can cause health problems and also corrosion of concrete pipes (Meksi et al., 2012). The regeneration of dithionite from the used dyebath is so far not possible, hence the by-products are discharged into the wastewater. As a result, there are attempts to use alternative natural reducing agents in indigo reduction, for example, glucose (Ushida & Matsuo, 1991), ripe banana (Lasopha et al., 2015), banana peel extract (Shin et al., 2013), apple extracts (Hossain et al., 2017), and bokbunja (Rubus coreanus Miq.) sludge (Shin et al., 2014). Reducing sugars such as glucose is successfully used for indigo reduction in a strong alkaline solution at high temperatures. As shown in Figure 2, glucose is oxidized to gluconate form which can simultaneously reduce indigo pigment in the dyebath to leuco indigo (Bechtold et al., 1998; Saikhao et al., 2017).
Characterization of kraft pulp delignification using sodium dithionite as bleaching agent
Published in Chemical Engineering Communications, 2020
Jishnu Krishnan, Susmith Sunil Kumar, R. Krishna Prasad
Sodium dithionite is a whitish yellow crystalline solid and is the active chemical in dithionite (hydrosulfite) bleaching process. It is obtained as a solid or liquid or even produced onsite through reaction of sodium hydroxide with sodium borohydride. The kappa reduction of the pulp is achieved by the reaction of dithionite with the chromophores present in the lignin to yield lighter colored compounds. It has been established through studies that high temperatures results in good bleaching as high temperature favors diffusion of dithionite ions into fiber cell wall and has a large reaction rate than hydrogen peroxide. UV light reacts with the sodium dithionite pulp and reduces the brightness by inducing a yellowish color to the paper (Melzer, 1985). The objective of this work is to remove lignin from kraft pulp using sodium dithonite as bleaching agent. The sodium dithionite is cheap and efficient bleaching agent used in delignification process of kraft pulp.