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A method for recovering chromium from leather tanning wastewater

A waste water and tanning technology, applied in the field of chromium recovery, can solve the problems of low recovery rate, high cost, unfavorable chromium recovery and utilization, etc., and achieve the effects of improving chromium recovery rate, sufficient reaction, and saving recovery cost.

Active Publication Date: 2018-02-09
武汉森泰环保股份有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, the disclosure of existing chromium-containing wastewater treatment technology, as disclosed in CN103101491A, is a method for reclaiming collagen and chromium salts from chromium waste skin slag. The method uses chemicals such as metal oxides and surfactants, and the cost High, it is easy to introduce other impurities, which is not conducive to the recovery and utilization of chromium
Another example is disclosed chromium-containing wastewater treatment process in CN103833155A, and this method recycling rate is low

Method used

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  • A method for recovering chromium from leather tanning wastewater

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Embodiment 1

[0035] A method for recovering chromium from leather tanning wastewater. The sewage of the chromium recovery system comes from the tanning and retanning process. The chromium content of the wastewater is 2500-3000mg / L, and the designed treatment water volume is 350m 3 / d, pH value is 3.5~4.5, recovery process figure 1 ,Specific steps are as follows:

[0036] (1) Pretreatment: After the wastewater intercepts large floating objects through artificial grills and mechanical grilles, oil and other fine suspended solids and colloidal substances are further separated by pressurized dissolved air flotation, and then impurities are removed by self-cleaning mechanical filtration ; Fine grid gap 1mm, air bearing surface load 2.5m 3 / m 2 h, the air flotation separation time is 35min, the dissolved air water reflux ratio is 40%, and the self-cleaning filtration accuracy is 80μm;

[0037] (2) Precipitation and separation: add 20% NaOH solution and sedimentation aid MgSO to the effluent a...

Embodiment 2

[0045] A tannery processes 1 million pieces of raw cowhide annually, and produces 3000m of wastewater every day 3 / d, of which, the chrome tanning wastewater is about 300m 3 / d, Cr in wastewater 3+ Concentration is about 2000mg / L, pH is 4-5, adopt method of the present invention to process leather tanning chromium-containing wastewater and recycle the chrome sludge that produces, concrete steps are as follows:

[0046] (1) Pretreatment: Firstly, the raw water is pretreated by the drum grill machine, pressure dissolved air flotation machine and brush self-cleaning filter to remove impurities such as minced meat, grease, skin dregs, hair and suspended solids in the water , the mechanical grid is a drum type grid, and the gap between the grid bars is 1mm; the air flotation equipment is a pressure dissolved air flotation machine, and the surface load of the separation area is 2.5m 3 / m 2 h, the air flotation separation time is 35min, the dissolved air water reflux ratio is 40%;...

Embodiment 3

[0055] A method for reclaiming chromium from leather tanning wastewater, comprising the following steps:

[0056] (1) Pretreatment: remove impurities, grease, suspended matter and some organic matter in the leather tanning wastewater; the leather tanning wastewater first removes impurities through a mechanical grid, and then separates the grease, suspended matter and part of the organic matter through the air flotation equipment, and then Then remove the suspended matter in the liquid through a filter; wherein the mechanical grid is a drum type grid, and the gap between the grid bars is 1mm; the air flotation equipment is a pressure dissolved air flotation machine, and the surface load of the separation area is 2 ~ 3m 3 / m 2 h, the air flotation separation time is 30-40min, the dissolved air water reflux ratio is 30%-50%; the filter is a brush-type self-cleaning filter, the filtration accuracy is 80μm, and the water inlet pressure is 3kg / cm 2 ;

[0057] (2) Precipitation an...

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Abstract

The invention discloses a method for recovering chromium from leather tanning waste water. The method comprises the following steps: (1) pretreatment; (2) precipitation separation; (3) dehydration; (4) acidification; and (5) reduction. By adoption of the method disclosed by the invention to carry out recovery and resource utilization of heavy metal element chromium in the leather tanning waste water, the problems of up-to-standard release of chromium-containing waste water and safe disposal of chromium-containing hazardous wastes are effectively solved, a new approach for treating the chromium in the leather tinning waste water is opened, the recovered chromium liquor is used for a leather tinning process, the waste is changed into a valuable thing, the added amount of chromium powder is reduced, the production cost is reduced, the generated quantity of chromium-containing hazardous wastes is reduced at the same time, and energy conservation and emission reduction are realized. Moreover, according to the method disclosed by the invention, the chromium-containing sludge generated by the treatment of leather tanning chromium-containing waste water is prepared into a chromium tanning agent, useful components in the sludge are effectively utilized, and resource waste and environmental pollution are reduced, so that the method accords with the concepts of clean production and cycle economy.

Description

technical field [0001] The invention relates to a method for recovering chromium from leather tanning wastewater, belonging to the field of wastewater treatment. Background technique [0002] Leather tanned by chrome tanning agents is washable, storage-resistant, and has the best moisture and heat stability, so it is widely used in leather tanning. According to statistics, for every ton of hide and hide processed, Cr 2 o 3 The consumption is about 50kg, of which more than one-third is not absorbed by the leather and enters the waste water, which not only causes waste of chromium resources, but also brings serious water pollution problems. Since chromium is a heavy metal, it belongs to the first category of pollutants strictly controlled by the state. In order to remove chromium in wastewater, it is often necessary to add a large amount of chemical agents, and eventually form a large amount of chemical sludge. [0003] According to the "National List of Hazardous Wastes",...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C02F9/04C02F11/00C02F11/12C02F11/18C02F101/22
CPCC02F1/52C02F1/66C02F9/00C02F11/00C02F11/122C02F11/18C02F2101/22
Inventor 彭继伟王敏冯梅王淼左洛邹彬杨卓黄凯
Owner 武汉森泰环保股份有限公司
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