Separating method for chromium and iron in hydrochloric acid system

Abstract

The invention discloses a separating method for chromium and iron in a hydrochloric acid system. The separating method comprises the following technology steps that firstly, a chromic chloride and ferrous chloride mixed solution is obtained through carbon ferrochrome leaching via hydrochloric acid, all Fe<2+> is oxidized into Fe<3+> through hydrogen peroxide firstly, then an extraction agent is added for extraction according to the content of iron in the solution and the proper phase ratio, a water phase obtained after extraction is a chromic chloride solution, reextraction is conducted on an organic phase through water, a ferric chloride solution and an extraction agent are obtained, and the extraction agent is circularly used; secondly, chromic chloride crystals are obtained from the chromic chloride solution via a direct crystallization method, chromic hydroxide can be prepared through an alkali adding neutralization and sedimentation method as well, the chromic hydroxide is then subjected to high-temperature roasting, and chromic oxide is obtained; and thirdly, the ferric chloride solution can be directly used as a water purifying agent, ferric hydroxide can be prepared through the alkali adding neutralization and sedimentation method, the ferric hydroxide is subjected to high-temperature roasting, and iron oxide red pigment is obtained. The technology is simple, operation is easy, and the iron removal rate reaches up to 99.95% or above.

Description

technical field [0001] The invention relates to the technical field of ferrochrome acid-dissolving production of chromium salts and electroplating sludge hydrochloric acid leaching solution treatment, in particular to a method for separating chromium and iron in a hydrochloric acid system. Background technique [0002] In the field of ferrochromium acid solution production of chromium salt and electroplating sludge hydrochloric acid leaching solution treatment technology, especially in the process of carbon ferrochromium hydrochloric acid leaching to produce chromium salt, due to the similar chemical properties of chromium and iron elements, there is an adsorption-co-precipitation effect, which makes the separation Iron removal has become a difficult problem. The existing methods for the separation of chromium and iron in hydrochloric acid medium mainly include: (1) ferrous oxalate precipitation method, which utilizes the principle of low solubility product of ferrous oxalate...

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Problems solved by technology

Although this method can realize the separation of chromium and iron, the iron removal rate can only reach about 98%, and the loss of chromium is large, and the higher reaction temperature and longer reaction time will definitely lead to the increase of cost, the most obvious The defect is that the chromium precipitation reaction is sensitive to the pH value, and a slight error will produce a composite precipitate of colloidal chromium phosphate and chromium hydroxide, making filtration very difficult

(4) Solvent extraction method. It has been reported that TBP chromium extraction or P204 iron extraction method is used to separate chromium and iron in hydrochloric acid medium. Low rate, large loss of chromium

There are also reports of using dodecylamine or octadecylamine as the extraction agent to extract and separate chromium and iron. Although the iron removal rate of this method can reach 99%, the pH value of the solution is required to be around 2, and there is a problem of co-extraction of chromium and iron. , the emulsification phenomenon is serious during the extraction process. In order to solve the emulsification problem, a higher temperature (80°C is the best) is required. At the same time, it is necessary to add demulsifiers such as sodium chloride, and the back extraction of iron ions is also difficult. At present, this method It is still in the stage of laboratory research and cannot realize industrial production

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