Method for detoxifying chromium slags

Abstract

The method discloses a method for detoxifying chromium slags. The method comprises the following steps of: drying and grinding the chromium slags and walnut shells; placing the dried and ground chromium slags and walnut shells into a ceramic crucible in a certain ratio and mixing the chromium slags and the walnut shells uniformly; then placing the crucible into a microwave oven, wherein the crucible is enclosed by slag wool heat insulating material for heat preservation; adopting an armored thermocouple with a shield to measure the temperature in a microwave field; performing heat preservation for 10 to 20 minutes when the temperature rises to 700 to 1,000 DEG C, and then turning off the microwave oven; opening the oven port in 5 to 10 minutes; immersing the material into distilled water for 24h after the material is cooled; filtering the material and setting the volume of the filtrate to be 250 ml; measuring the concentration of Cr6+ in the filtrate by adopting a diphenylcarbazide spectrophotometric method; and converting the Cr6+ concentration into the mass percent of the mass of extractive hexavalent chrome accounting for the mass of a sample chromium slag to finally calculate the detoxification ratio. The method for detoxifying the chromium slags deoxidizes the chromium slags by using C in the walnut shells, so both the walnut shells and the chromium slags are fully used, resources are saved, and the waste is changed into a useful material. The method has the characteristic of improving the chemical yield to lower the production cost, and has simple steps and convenient operations to further reduce the production cost.

Description

technical field

[0001] The invention relates to a technology for detoxifying chromium residues by reacting walnut shells and chromium residues by a microwave heating method, and belongs to the fields of environmental protection and "three wastes" treatment. Background technique

[0002] Chromium slag is the waste residue in the production process of chromium salts. The production of chromium salts in my country mostly adopts the soda ash roasting method. In the production process of metallic chromium or chromium salts, the finely ground chromite, dolomite and soda ash are added to the rotary kiln for oxidation roasting to make the chromite in the chromite ore. Most of the chromium trioxide is converted into sodium chromate, and the residual solid waste is chromium slag. The harmful components in chromium slag are mainly hexavalent chromium compounds such as sodium chromate tetrahydrate and calcium chromate. Hexavalent chromium has strong oxidizing properties and fluidity, a...

Examples

Embodiment 1

[0041]Put 10g of chromium slag and 1.0g of walnut shell into the ceramic crucible, and mix evenly, then put the reactor into the microwave oven, use slag wool insulation material around the reactor to keep warm, and use a shielded armored thermocouple to measure the microwave field. Temperature: raise the temperature to 700°C, keep warm for 20 minutes, turn off the microwave oven, open the furnace door after 5 minutes, immerse the material in distilled water after the material is cooled, filter after soaking for 24 hours, and dilute the filtrate to 250ml, use diphenylcarbazide Determination of Cr in filtrate by spectrophotometry 6+ Concentration, calculated as Cr 6+ The detoxification rate is 99.012%.

Embodiment 2

[0043] Put 10g of chromium slag and 2.0g of walnut shell into the ceramic crucible, and mix evenly, then put the reactor into the microwave oven, use slag wool insulation material around the reactor to keep warm, and use a shielded armored thermocouple to measure the microwave field. temperature, raise the temperature to 800°C, keep warm for 15 minutes, then close the microwave oven, and open the furnace door after 5 minutes. After the material is cooled, immerse the material in distilled water, filter after soaking for 24 hours, and dilute the filtrate to 250ml. Determination of Cr in filtrate by spectrophotometry 6+ Concentration, calculated as Cr 6+ The detoxification rate is 99.117%.

Embodiment 3

[0045] Put 10g of chromium slag and 5.0g of walnut shell into the ceramic crucible, and mix evenly, then put the reactor into the microwave oven, keep warm with slag wool insulation material around the reactor, and use a shielded armored thermocouple to measure the microwave field Temperature, raise the temperature to 900°C, keep warm for 10 minutes, turn off the microwave oven, open the furnace door after 5 minutes, immerse the material in distilled water after the material is cooled, filter after soaking for 24 hours, and dilute the filtrate to 250ml. Determination of Cr in filtrate by spectrophotometry 6+ Concentration, calculated as Cr 6+ The detoxification rate is 99.258%.

technical field

[0001] The invention relates to a technology for detoxifying chromium residues by reacting walnut shells and chromium residues by a microwave heating method, and belongs to the fields of environmental protection and "three wastes" treatment. Background technique

[0002] Chromium slag is the waste residue in the production process of chromium salts. The production of chromium salts in my country mostly adopts the soda ash roasting method. In the production process of metallic chromium or chromium salts, the finely ground chromite, dolomite and soda ash are added to the rotary kiln for oxidation roasting to make the chromite in the chromite ore. Most of the chromium trioxide is converted into sodium chromate, and the residual solid waste is chromium slag. The harmful components in chromium slag are mainly hexavalent chromium compounds such as sodium chromate tetrahydrate and calcium chromate. Hexavalent chromium has strong oxidizing properties and fluidity, a...

Examples

Embodiment 1

[0041]Put 10g of chromium slag and 1.0g of walnut shell into the ceramic crucible, and mix evenly, then put the reactor into the microwave oven, use slag wool insulation material around the reactor to keep warm, and use a shielded armored thermocouple to measure the microwave field. Temperature: raise the temperature to 700°C, keep warm for 20 minutes, turn off the microwave oven, open the furnace door after 5 minutes, immerse the material in distilled water after the material is cooled, filter after soaking for 24 hours, and dilute the filtrate to 250ml, use diphenylcarbazide Determination of Cr in filtrate by spectrophotometry 6+ Concentration, calculated as Cr 6+ The detoxification rate is 99.012%.

Embodiment 2

[0043] Put 10g of chromium slag and 2.0g of walnut shell into the ceramic crucible, and mix evenly, then put the reactor into the microwave oven, use slag wool insulation material around the reactor to keep warm, and use a shielded armored thermocouple to measure the microwave field. temperature, raise the temperature to 800°C, keep warm for 15 minutes, then close the microwave oven, and open the furnace door after 5 minutes. After the material is cooled, immerse the material in distilled water, filter after soaking for 24 hours, and dilute the filtrate to 250ml. Determination of Cr in filtrate by spectrophotometry 6+ Concentration, calculated as Cr 6+ The detoxification rate is 99.117%.

Embodiment 3

[0045] Put 10g of chromium slag and 5.0g of walnut shell into the ceramic crucible, and mix evenly, then put the reactor into the microwave oven, keep warm with slag wool insulation material around the reactor, and use a shielded armored thermocouple to measure the microwave field Temperature, raise the temperature to 900°C, keep warm for 10 minutes, turn off the microwave oven, open the furnace door after 5 minutes, immerse the material in distilled water after the material is cooled, filter after soaking for 24 hours, and dilute the filtrate to 250ml. Determination of Cr in filtrate by spectrophotometry 6+ Concentration, calculated as Cr 6+ The detoxification rate is 99.258%.

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