Method for preparing chromium iron black from electroplated chromium-containing waste water in recycling mode

Abstract

The invention discloses a method for preparing chromium iron black from electroplated chromium-containing waste water in a recycling mode. The method comprises the following steps that 1, the total chromium, chromium (III) and chromium (VI) content in the electroplated chromium-containing waste water is measured, the pH of the waste water is adjusted to range from 8 to 11 with liquid caustic soda, and an oxidizing agent is added to oxidize chromium (III) into chromium (VI); 2, the pH of the oxidized waste water is adjusted to range from 3 to 4 with sulfuric acid, an iron-containing agent is added, stirring is carried out at normal temperature for reacting, and a reaction solution is obtained; 3, liquid caustic soda is added into the reaction solution obtained in the step 2, the pH is adjusted to range from 8 to 9, then an aeration reaction is carried out, filtering and separation are carried out, and a filter cake and filtrate are obtained, wherein the filtrate is waste water obtained after chromium removal and can be directly drained or used for the rinsing section in the step 4; the filter cake obtained in the step 3 is subjected to rinsing, drying, calcining and smashing, and the chromium iron black product is obtained. Chromium in the electroplated chromium-containing waste water is converted into chromium iron black pigments with high economic additional value through a simple process path, the problem about treatment of the electroplated chromium-containing waste water is solved, chromium resources are reutilized, and sustainable development of the resources is achieved.

Description

technical field [0001] The invention relates to the field of resource treatment of iron-based pigment wastewater, in particular to a method for preparing ferrochrome black from electroplating chromium-containing wastewater as resource. Background technique [0002] Electroplating is a process of plating a layer of metal or alloy on the surface of metal or other materials using chemistry and electrochemistry. Electroplating technology is widely used in machine manufacturing, light industry, electronics and other industries. [0003] The water quality of electroplating wastewater is complex. Chromium-containing wastewater is a large amount of wastewater produced in the electroplating industry. The total chromium and hexavalent chromium contained in it are the first type of pollutants. The pollution to the environment and ecology is extremely serious. It is a national Strictly controlled pollutant indicators. [0004] For the treatment of chromium-containing wastewater, common...

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Problems solved by technology

[0004] For the treatment of chromium-containing wastewater, common treatment methods include chemical method, electrolysis method, ion exchange method, membrane separation method and microbial method, etc. The chemical reduction method uses a reducing agent to reduce the highly toxic Cr(Ⅵ) in the wastewater Cr(Ⅲ) with low solubility is finally removed by precipitation with chromium hydroxide. This method has simple equipment, easy operation, and low operating costs; but it produces a large amount of difficult-to-handle sediment sludge, which will cause secondary pollution

The electrolysis method is a method to eliminate the toxicity of Cr(Ⅵ) by electrochemical reaction between the electrode and the wastewater. This method consumes a lot of electricity, consumes a lot of electrode metal, and the separated precipitate is not easy to process and utilize, and there is a certain amount of secondary pollution. thing

Membrane separation method to treat electroplating chromium-containing wastewater is in the exploration and development stage. In addition, the cost of the membrane is relatively high, and it needs to be regenerated or replaced after a period of use. When it is used for large-scale wastewater treatment production, the operating cost is relatively high

The adsorption method is to use the large specific surface area of ​​the adsorbent to adsorb and remove the Cr(Ⅵ) in the wastewater; this method can quickly treat the chromium ions in the wastewater, and the treatment effect is better, the operating cost is less, but the adsorbent is consumed , the equipment is huge; in actual production, it is difficult to transport, load and unload the adsorbent, and there are still certain technical difficulties in desorption

The biological method mainly relies on artificially cultivated functional bacteria, and uses the electrostatic adsorption of microorganisms, catalytic conversion of enzymes, complexation, flocculation, and co-precipitation to remove Cr(Ⅵ) from wastewater, which is rarely used in actual engineering.

The ion exchange method treats electroplating wastewater, the effluent water quality is good, useful substances can be recovered, and it is easy to realize automation. The disadvantage of this method is that the resin is easily oxidized and polluted, and the pretreatment requirements are relatively high.

[0005] At present, there are many methods for treating chromium-containing wastewater, but the traditional chemical reduction precipitation method and electrolysis method have the disadvantages of secondary pollution and the difficulty of recycling chromium ions; although biological methods and membrane separation methods have broad prospects, they are still under research In the trial stage, it will take time for large-scale utilization; while the ion exchange method and adsorption method have disadvantages such as high pretreatment requirements, easy oxidation of the resin, and low concentration of recovered chromic acid.

Moreover, in the prior art, the recovery and utilization efficiency of chromium resources is mainly low, resulting in waste of resources