The invention relates to a method for producing sodium bichromate. The method comprises the following steps: 1) performing hydrothermal oxidation on slurry of chromium-containing sodium carbonate, ferrochromium and soda and water to obtain sodium chromate and carbon dioxide, and removing carbon dioxide; 2) separating the obtained reaction mixture to obtain a sodium chromate solution and iron slag; 3) concentrating the obtained sodium chromate solution to 600-1400g/L; 4) carbonizing and acidizing the sodium chromate concentrated solution by using the carbon dioxide removed in the step 1), thus obtaining a sodium dichromate solution and chromium-containing sodium bicarbonate; and 5) decomposing the obtained chromium-containing sodium bicarbonate into chromium-containing sodium carbonate and carbon dioxide, returning the chromium-containing sodium carbonate to the step 1), and returning carbon dioxide to the step 4). According to the method, the processes of preparing the sodium chromate solution and acidizing the sodium chromate are organically combined, comprehensive recycling of Na+ and CO2 is realized, no waste residues are generated in the whole production process, the discharge of three wastes is greatly reduced, the method is a low-carbon, cyclic and clean type process for production of sodium bichromate, and the purity of the produced sodium bichromate is high.

Method for producing high-quality sodium bichromate

The invention relates to a one-step preparation method of sodium bichromate. The preparation method comprises the following steps: carrying out hydrothermal oxidation reaction on dispersoid of containing chromite powder, sodium-containing alkali and water at 150-370 DEG C under gauge pressure of 5-25MPa in the presence of oxygen and carbon dioxide catalyst; removing solids out of the reaction mixture to obtain sodium bichromate-containing aqueous solution; and performing complementary acidification on the aqueous solution to transform sodium chromate in the solution into sodium bichromate. The method has the advantages that sodium bichromate is prepared in one step, the traditional sodium bichromate production process is broken through, and the process flow is greatly shortened; moreover, the emission of the three wastes is greatly reduced and energy loss in the reaction process is lowered. Therefore, the method is an efficient, energy-saving and clean production process of sodium bichromate.

One-step preparation method of sodium bichromate

The invention belongs to the field of heavy metal solid waste treatment, and discloses a method for extracting chromium in electroplating sludge through cooperation of hydrothermal treatment and oxidation. The method comprises the following steps: mixing and stirring original electroplating sludge or pretreated electroplating sludge and alkali liquor in a hydrothermal kettle; sealing the obtainedmixed system, introducing oxygen or air with a certain pressure, or adding an oxidizing agent, keeping stirring, keeping warm, carrying out hydrothermal reaction, standing and cooling the obtained reaction system, carrying out suction filtration to obtain a filtrate which is a high-concentration chromium solution, and washing the solid to obtain non-toxic minerals. According to the method, on thebasis that the high leaching rate of chromium is guaranteed, the temperature can be reduced to 300 DEG C or below, energy consumption is reduced, and the service life of equipment is prolonged. Fillers such as lime and dolomite do not need to be added, so that reduction of wastes is facilitated.

Method for extracting chromium in electroplating sludge through cooperation of hydrothermal treatment and oxidation

The present invention provides a hydrothermal oxidation method for producing alkali metal dichromate from carbon ferrochrome, and the method comprises the following steps: formulating an initial reaction liquid by mixing carbon ferrochrome, an alkaline substance and water, in which the actual addition amount of the alkali is controlled smaller than the theoretically required amount; adding the initial reaction liquid into a reaction kettle, charging an oxidizing gas into the reaction kettle, and allowing the reaction to proceed for 0.5 to 3 h at a temperature of 150° C. to 370° C. and a pressure of 2 Mpa to 24 MPa; carrying out solid-liquid separation, cooling the resultant filtrate to a temperature of −12° C. to −20° C. to precipitate crystals, and carrying out separation by centrifuge to obtain alkali metal dichromate solution; adding CrO3 to the alkali metal dichromate solution until the degree of acidification reaches 100% or greater, concentrating the solution by evaporation, and cooling it to precipitate crystals, so as to afford alkali metal dichromate. The method has a simple process, is easy to control, and can directly produce sodium dichromate under hydrothermal conditions.

Zhu Ji

Papers

A hydrothermal oxidation method for production of alkali metal dichromate from carbon ferrochrome