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Method for recycling chromium in electroplating sludge through sub-molten salt method

A technology of electroplating sludge and sub-molten salt method, which is applied in the direction of improving process efficiency, can solve problems such as blanks, and achieve the effects of ensuring full contact, avoiding hardening, and being conducive to full dissolution

Active Publication Date: 2019-01-29
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The sub-molten salt method has been involved in chromium ore smelting, such as "Clean Production Method of Potassium Chromate" (CN 1162330 C), but due to the very different properties of electroplating sludge and chromite (the original mineral for smelting chromium slag), Large, there is currently a blank for the improvement of the sub-molten salt method for the treatment of electroplating sludge

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] Get 100 kilograms of some kind of original electroplating sludge, its moisture content is about 69% according to laboratory measurement, and chromium content is 5.6% (relative to electroplating sludge dry mass). Thoroughly mix and stir 30 liters of aqueous solution containing 4.5 kg of NaOH and electroplating sludge, and dry at 60°C until the water content is lower than 20%. Put the dried material into high-temperature equipment, and bake it at 350°C for 3 hours in an air atmosphere. After the material is cooled, take it out, soak it with 150 liters of pure water for 40 minutes, filter, and rinse the filter cake with 50 liters of water to obtain a chromium solution with a concentration of about 200 liters. The chromium concentration is 7.7 grams per liter, and the recovery rate of chromium is about 89 %, to obtain about 28.1 kg of detoxified minerals, wherein the chromium content is 0.69%.

Embodiment 2

[0028] Get 20 kilograms of some kind of original electroplating sludge, its moisture content is about 33%, and chromium content is 8.9% (relative to electroplating sludge dry mass) as measured in the laboratory. Fully mix and stir 40 liters of aqueous solution containing 3.5 kilograms of KOH and the electroplating sludge to form a slurry, and then air-dry naturally until the water content is lower than 20%. Put the obtained dry material into a granulator for granulation, put the granulated pellets into a high-temperature equipment, and bake at 400° C. for 2 hours in an air atmosphere. After the material is cooled, it is taken out, leached with 85 liters of hydrochloric acid with a pH of 5 to 6 for 25 minutes, filtered, and the filter cake is rinsed with 45 liters of hydrochloric acid with a pH of 5 to 6 to obtain a chromium solution with a concentration of about 130 liters. The concentration was 8.5 g / l, the chromium recovery rate was 93%, and about 11.3 kg of detoxified miner...

Embodiment 3

[0030] Get 50 kilograms of some kind of original electroplating sludge, its water content is about 41%, chromium content is 8.2% (relative to electroplating sludge dry basis mass), calcium element mass is about 8% of dry basis sludge ( It has been proven that the use of NaOH and KOH alone or in combination will form slightly soluble calcium chromate, resulting in incomplete extraction). Will contain 4 kg NaOH and 6.5 kg Na 2 CO 3 80 liters of aqueous solution and electroplating sludge are fully mixed and stirred to form a slurry, which is dried at 50°C until the water content is lower than 20%. Put the dried material into high-temperature equipment, and bake it at 420°C for 3 hours in an air atmosphere. After the material is cooled, it is taken out, leached with 220 liters of sulfuric acid with a pH of 6 for 40 minutes, filtered, and the filter cake is rinsed with 60 liters of water to obtain a chromium solution with a concentration of about 280 liters. The chromium concentr...

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Abstract

The invention belongs to the technical field of solid waste treatment, and discloses a method for recycling chromium in electroplating sludge through a sub-molten salt method. The method comprises thesteps of sufficiently stirring and mixing the electroplating sludge and an alkaline liquor so as to form a sludge slurry, then drying until the moisture content is lower than 20 percent, and obtaining dried sludge; roasting the dried sludge under the air atmosphere at 280 to 580 DEG C, then using water or a weak-acid water solution for leaching, filtering and separating to obtain a chromium-containing solution and a detoxified sludge slag. According to the method for recycling the chromium in the electroplating sludge through the sub-molten salt method provided by the invention, low melting points of alkali metal hydroxides such as NaOH and KOH are utilized, so that a sub-molten salt state is formed, and reactants are promoted to be mixed sufficiently and contact with air; and aiming at the situations of a calcium-containing element, sodium carbonate or potassium carbonate is added for promoting the formation of sodium chromate, potassium chromate and calcium carbonate, so that the formation of calcium chromate is avoided, and chromate is favorably dissolved sufficiently. By adopting the method, the recovery rate of the chromium is larger than 90 percent, the resource utilizationof the electroplating sludge is realized, and the method has favorable socioeconomic benefit and ecological environment benefit.

Description

technical field [0001] The invention belongs to the technical field of solid waste treatment, and in particular relates to a method for recovering chromium in electroplating sludge by a sub-molten salt method. Background technique [0002] Electroplating sludge is a toxic and hazardous solid waste produced in the production process of the electroplating industry. Because it contains a large amount of toxic heavy metals such as chromium, cadmium, nickel, and zinc, it has caused great pressure on the development of the industry, the ecological environment, and human health. harm. The traditional solidification-landfill mode of electroplating sludge and the method of using electroplating sludge to prepare building materials cannot solve a large amount of electroplating sludge, nor can it completely solve the impact of heavy metals on the environment. Therefore, there is an urgent need to develop effective separation methods for heavy metals in electroplating sludge. [0003] ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C22B7/00C22B1/02C22B1/24C22B1/248C22B34/32
CPCC22B1/02C22B1/24C22B1/248C22B7/001C22B7/006C22B34/32Y02P10/20
Inventor 林璋郑嘉毅刘炜珍邓洪刘学明
Owner SOUTH CHINA UNIV OF TECH
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