Laboratory Testing & General Mineral Processing Engineering

Laboratory Testing & General Mineral Processing Engineering 2017-04-04T06:57:51+00:00
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Substitute of sodium hydrosulfite in bleaching of talc ore. (1 reply)

9 months ago
Joel 9 months ago

Sodium hydrosulfite (or sodium dithionite) is an excellent reducing agent. It acts as a hematite reductant in bleaching process of talc; the reaction is very fast at room temperature. The problem is that the talc becomes contaminated with sulfur compounds. Can anyone suggest another bleaching agent?
Sorry, I don't speak english.
Thank you for understanding!

9 months ago
David 9 months ago

Bem-vindo ao fórum Joel.

maybe this will help you. I am really outside my expertise here. Here is some of what I found.

The theory of the action of bleaching clays in decolorizing oils is highly involved and the underlying reasons for the phenomenon are not completely known. Suffice it to state here that the action is not a straining or filtering action but a selective adsorption of the color bodies and other impurities. The adsorbed color bodies and impurities are strongly held within the clay structure and can be removed only by drastic treatment. This indicates that the bleaching clays operate mainly by chemical adsorption. The literature should be consulted for a thorough investigation of the subject.

At present, sodium hydrosulfite is used by the kaolin industry as the reductive bleach. It is often purchased commercially as a liquid solution and added into an acidified slurry. Before the use of commercial sodium hydrosulfite, kaolin plants manufactured zinc hydrosulfite on site by adding zinc dust to sulfurous acid made by passing SO2 gas into water. This process was abandoned in the 1970s due to environmental concerns about zinc in waste waters. In the 1970s, Engelhard patented a process that made sodium hydrosulfite from an iron hydrosulfate. Difficulties with separating the iron hydroxide byproduct from the bleach and a decrease in the cost of commercial bleach caused the project to be abandoned.

I am attached 3 papers you may find useful. They talk about aluminium hydrosulfite as a method.

Hope others can complement and certainly improve this.

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