A kind of method for preparing magnesium carbonate from calcium-free chromium slag

Abstract

The invention discloses a method for preparing magnesium carbonate from chromium slags without calcium. The method comprises the following steps: (1) smashing the chromium slags without calcium; (2) leaching the chromium slags by adding water and making leach liquor for later use; (3) reducing hexavalent chromium in the leach liquor into trivalent chromium for precipitating; (4) separating iron and aluminum precipitates from the chromium slags treated by the step (2); (5) separating an aluminum solution from the precipitates obtained by the step (4); (6) adding ammonium benzoate into the aluminum solution so as to generate aluminum benzoate; and (7) collecting filtrates obtained by the steps (3), (4) and (6) and combining; and adding the sodium carbonate into the combined filtrate so as to prepare the magnesium carbonate. According to the method, the chromium slags containing the hexavalent chromium can be detoxicated; and the magnesium elements contained in the chromium slags are converted into another type of the magnesium carbonate which can be utilized and has a better additional value. Thus, the effects of turning a disadvantage into an advantage as well as turning waste into treasure are realized.

Description

technical field [0001] The invention belongs to the technical field of comprehensive utilization of chromium slag, and in particular relates to a method for preparing magnesium carbonate from calcium-free chromium slag. Background technique [0002] Chromium salt is an important inorganic salt product. In recent years, under the guidance of relevant government departments, the manufacturers of chromium salt in my country have adopted technological transformations. Most of them adopt calcium-free roasting process, although the chromium residue is reduced compared with calcium roasting process. However, the chromium slag produced still contains hexavalent toxic chromium salts, the main components are MgO70-80%, CaO0.5-1.0%, Fe 2 o 3 6~12%, SiO 2 3~7%,Al 2 o 3 3~5%,Cr 2 o 3 0.2~2%, of which Cr 6+ 0.2~0.5%. Due to its strong toxicity due to the excess water-soluble Cr(Ⅵ), chromium slag is one of the 47 most dangerous wastes recognized internationally and is listed as a na...

AI Technical Summary

Problems solved by technology

However, whether it is used as an additive for cement production or as a sintering agent for steelmaking, it needs to be processed in cooperation with relevant manufacturers. During the processing process, due to problems such as chromium slag transportation, addition process, and cost, the cooperative manufacturers are not active, and the reduced chromium slag Can not be disposed of in a timely and sufficient amount, resulting in an increasing stockpile of chromium slag in chromium salt manufacturers, causing increasing pressure on the environment