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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).
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.