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Sodium borohydride, used in combination with sodium bisulfite, is recognized by leading researchers as a replacement for sodium hydrosulfite in vat dyeing, indigo dyeing, color stripping, reductive clearing, machine cleaning and many other applications where a stable, environmentally desirable reducing agent is .
Sodium dithionite may also be used as a bleach for leather. Paper industries use Sodium Hydrosulfite for bleaching of the wood pulp and producing white paper. In chemical industries, Sodium hydrosulfite (sodium dithionite, Na2S2O4) is an inexpensive and safe reducing agent, which for example enables the reduction of aromatic nitro and diazonium ...
Reagents used to bleach or "brighten"high-yield pulps (high lignin content retained after bleaching) are milder in their action than reagents used for delignification. Both mild oxidative and reductive treatments are effective; the most commonly used reagents are hydrogen (sodium) peroxide and sodium dithionite (hydrosulfite).
Reducing the iron contents to increase the value of kaolin by bleaching process is investigated. The effects of factors which can improve the whiteness of kaolin have been studied. The dosage of sodium dithionite, pH value, solid-to-liquid ratio and reaction time were chose as factors based on mono-factor experimental results.
Like newsprint, coated papers have been on the decline as well in recent years. In 2005, North American production of coated paper was down 3 percent for the year. Sodium hydrosulfite is used to bleach kaolin clay, which makes up most of the mineral content of clay coatings.
Properties and reactions. Sodium dithionite is stable when dry, but is slowly oxidized by air when in solution. Even with the absence of air, solutions of sodium dithionite deteriorates due to the following reaction: 2 S 2 O 4 2-+ H 2 O → S 2 O 3 2-+ 2 HSO 3-Thus solutions of sodium dithionite cannot be stored for a long period of time. [2 ...
Sodium hydrosulfite is also used as commercial bleach for treatment of leather, kaolin clay, fur and chrome tanning. Hazards Identification Hazard Warnings: Sodium Hydrosulphite may ignite with moisture and air. harmful if swallowed or inhaled. causes irritation to skin, eyes and respiratory tract.
SOURCES OF HYDROSULFITE IN PULP MILLS NaBH 4 + 8 NaOH + 8 SO 2 4 Na 2 S 2 O 4 + NaBO 2 + 6 H 2 O hydrosulfite borate Solid sodium hydrosulfite and hydrosulfite bleach solution containing pH buffer & other stabilizers can both be purchased Sodium hydrosulfite can also be produced on-site using the Borol Process
In a process for treating raw kaolin clay to improve the color and brightness by treating the clay in an aqueous dispersion with sodium dithionite, the improvement consisting of treating the dispersion with hydroxylamine or salt thereof after the treatment with sodium dithionite is complete.
Orthogonal Experiments for Kaolin Bleaching by Using Sodium Dithionite and Sulfuric Acid Article in Advanced Materials Research 968:116-124 · June 2014 with 97 Reads How we measure 'reads'
Improved methods for bleaching kaolin clay and other minerals are provided. More particularly, methods of the present invention employ a hydrosulfite or bisulfite material and a second reducing agent, preferably a reducing agent that contains a Group III element, such as a borohydride, to increase the brightness of kaolin clay and other minerals and reduce color present therein.
May 01, 2011· Sodium hydrosulfite, also known as sodium dithionite, can be made by cathodic reduction of sodium bisulfite (ECHO Process, Fig. 5.48). Important for the success of this reaction is the use of a high surface, multilayer stainless steel fiber cathode. This allows a low CD at the cathode for efficient reduction combined with a compact cell design.
Jul 24, 2020· Sodium dithionite has been used for bleaching of mechanical pulp since the 1930s (Bajpai 2014) and has been extensively studied as such. .
Search results for sodium dithionite at Sigma-Aldrich. Compare Products: Select up to 4 products. *Please select more than one item to compare
Sodium dithionite (also known as sodium hydrosulfite) is a white crystalline powder with a weak sulfurous odor. It is a sodium salt of dithionous acid. Although it is stable under most conditions, it will decompose in hot water and in acid solutions. It can be obtained from sodium bisulfite by the following reaction.
The reduction properties of Sodium Hydrosulphite also eliminate excess dye, residual oxide, and unintended pigments, thereby improving overall colour quality. Reaction with formaldehyde produces Rongalite, which is used as a bleach, in, for instance, paper pulp, cotton, wool, leather, chrome tanning agent and kaolin clay.
dioxins. In fact, the most abundant dioxin produced by the pulp and bleaching process, 2,3,7,8-tetrachlorodibenzo- p -dioxin (2,3,7,8-TCDD), has been found to be both a carcinogen and a deadly toxin .Thus, chlorine as a bleaching agent is being replaced by the safer bleaching agents chlorine dioxide and hydrogen peroxide.
Most reductive bleaching of wool is carried out using stabilized dithionite (2–5g/L) at pH 5.5–6 and 45–65 C for 1 h. Thiourea dioxide is more expensive than sodium dithionite, but is an effective bleach when applied (1–3 g/L) at 80 C and pH 7 for 1 h.
Anhydrous sodium dithionite decomposes to sodium sulfate and sulfur dioxide above 90 °C in the air. In absence of air, it decomposes quickly above 150 °C to sodium sulfite, sodium thiosulfate, sulfur dioxide and trace amount of sulfur. Redox reactions. Sodium dithionite is a reducing agent. At pH=7, the potential is -0.66 V vs NHE.
An alternative form of sodium dithionite is sodium sulfoxylate formaldehyde, which is prepared by the reaction of formaldehyde with the dithionite. Its applications are like those of dithionite, except that it is less reactive and more stable thermally. When the sulfoxylate is used, .
Residential without plant uptake. 200 .... The mechanism of Cr(VI) treatment using sodium dithionite (Na2S2O4) involves the conversion of... Get Quote; Sodium dithionite - ipcs inchem. Nov 14, 2002 ... processing of sodium dithionite and from the use of the substance itself, .... consumption of oxygen in biological sewage treatment plants or ...
Sodium hydrosulfite's reduction reaction removes residual oxide and wrong pigments. Sodium hydrosulfite is a reductive bleaching agent. It reduces carbonyl and alcohol groups, which function as colorants of the substances. It is used in bleaching mechanical paper pulp, cotton, wool and kaolin clay.
The removal of iron oxide from clay by sodium dithionite ... On the removal of iron oxide from clays with sodium dithionite-sulfuric acid solution (pH2-3), the reducing agent is used not only for the reduction of Fe^ to Fe^ but for the reaction with atmospheric oxygen and the self-decomposition reaction, therefore it is necessary to determine effective conditions of the reducing reaction.
Sodium hydrosulfite is the bleaching agent of choice for (chemi)mechanical pulps when a moderate (4-14 points) brightness increase is required [2]. Hydrogen peroxide is preferred for higher brightness gains, e.g., between 10 and 20 points [2].
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