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Method for removing heavy metals in sludge by using free nitrous acid

A technology for nitrous acid and heavy metals, applied in sludge treatment, chemical instruments and methods, water/sludge/sewage treatment, etc., can solve the problems of large consumption of sulfuric acid, long treatment time, large consumption, etc., and achieve removal effect Good, improve the dissolution efficiency, improve the effect of sludge settling performance

Inactive Publication Date: 2019-01-22
GUANGDONG INST OF ECO ENVIRONMENT & SOIL SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The chemical method usually uses sulfuric acid, hydrochloric acid or nitric acid to reduce the acidity (pH) of the sludge, so that the heavy metals adsorbed or fixed in the sludge are dissolved in the form of ions, and then the heavy metals are separated from the solid phase of the sludge by solid-liquid separation. This method has a good effect on removing heavy metals in sludge, but acidifying sludge and neutralizing the acid in the leaching solution consume a large amount of chemical reagents, and the cost is high
For example: CN 103183459A discloses a method for removing heavy metals from sewage treatment plant sludge, which requires adjusting the pH value of the sludge to 0.3-0.5, consumes a lot of sulfuric acid, and takes a long time to process

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0043] The sludge sample for testing is thickened sludge produced by a sewage treatment plant in Guangzhou. The physical and chemical properties of the sludge are as follows: pH is 6.36±0.21, oxidation-reduction potential (ORP) is (36.46±0.24) mV, water content is ( 97.86±0.18)%, the total solid content (TS) is (32.24±0.43) g / L, the volatile solid content (VSS) is (14.68±0.11) g / L, heavy metals Cu, Zn, Pb, Cd, Mn and The Co contents were (421.78±3.65) mg / kg, (825.56±4.68) mg / kg, (102.58±0.32) mg / kg, (5.96±0.12) mg / kg, (425.54±4.58) mg / kg and ( 6.58 ± 0.25) mg / kg.

[0044] A method utilizing free nitrous acid to remove heavy metals in sludge, comprising the following steps:

[0045] 1) Sludge acidification: Adjust the solid content of the sludge to 2%, then adjust the pH value of the sludge to 2.5 with sulfuric acid with a mass fraction of 10%, and then control the oscillator speed to 150r / min, and carry out at 30°C for 1h shaking culture;

[0046] 2) Free nitrous acid react...

Embodiment 2

[0050] The sludge samples for testing are the same as in Example 1.

[0051] A method utilizing free nitrous acid to remove heavy metals in sludge, comprising the following steps:

[0052]1) Sludge acidification: adjust the solid content of the sludge to 1%, then adjust the pH value of the sludge to 2.0 with sulfuric acid with a mass fraction of 15%, then control the oscillator speed to 200r / min, and carry out 0.5 at 30°C. h shaking culture;

[0053] 2) Free nitrous acid reaction: Add sodium nitrite to the sludge treated in step 1) (the addition amount is 60.50mg / L), then control the oscillator speed to 200r / min, and carry out shaking culture at 30°C for 4h, After testing, the dissolution rates of heavy metals Cu, Zn, Pb, Cd, Mn and Co in the sludge were 44.59%, 80.35%, 4.59%, 78.59%, 37.86%, and 32.69% respectively (as a comparison, simply carry out sludge acidification, Without free nitrous acid reaction, the dissolution rates of heavy metals Cu, Zn, Pb, Cd, Mn and Co in t...

Embodiment 3

[0057] The sludge samples for testing are the same as in Example 1.

[0058] A method utilizing free nitrous acid to remove heavy metals in sludge, comprising the following steps:

[0059] 1) Sludge acidification: adjust the solid content of the sludge to 2%, then adjust the pH value of the sludge to 2.5 with sulfuric acid with a mass fraction of 10%, then control the oscillator speed to 200r / min, and carry out at 30°C for 1h shaking culture;

[0060] 2) Free nitrous acid reaction: Add sodium nitrite to the sludge treated in step 1) (addition amount is 126.98mg / L), then control the oscillator speed to 200r / min, and carry out shaking culture at 30°C for 5h, After testing, the dissolution rates of heavy metals Cu, Zn, Pb, Cd, Mn and Co in the sludge were 41.59%, 79.86%, 4.01%, 69.48%, 36.14%, 31.52%, respectively;

[0061] 3) Sludge dehydration: carry out centrifugal dehydration to the treated sludge in step 2) to obtain filter residue (moisture content 74%) and filtrate;

[...

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PUM

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Abstract

The invention discloses a method for removing heavy metals in sludge by using free nitrous acid. The method comprises the following steps: 1) sludge acidification; 2) free nitrous acid reaction; 3) sludge dewatering; and 4) removal of the heavy metals in a filtrate. The free nitrous acid is used to destroy extracellular polymers in the sludge and dissolve microbial cells, so the dissolution efficiency of heavy metals, especially organically bound heavy metals, in the sludge is significantly improved, and the removal effect on the heavy metals in the sludge is good. The method also can be usedas a conditioning process before sludge the dewatering to significantly improve sludge sedimentation performance and kill pathogenic bacteria in the sludge, so favorable conditions are provided for the subsequent treatment, disposal and utilization of the sludge.

Description

technical field [0001] The invention relates to a method for removing heavy metals in sludge by using free nitrous acid. Background technique [0002] With the acceleration of urbanization and industrialization in my country, the output of municipal sludge is increasing day by day. It is estimated that by 2020, the annual output of urban sludge in my country will exceed 60 million tons. At present, most of the municipal sludge has not been stabilized and harmlessly treated and disposed of. It is usually sent to the municipal waste treatment plant for simple landfill or disposal, which greatly offsets the environmental purification effect of the sewage treatment plant and seriously restricts sewage treatment. The healthy development of the cause, and the non-standard disposal of urban sludge has also brought safety hazards to the urban environment. Municipal sludge contains a large amount of organic matter and rich N, P, K and other nutrient elements, which can be used as fe...

Claims

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Application Information

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IPC IPC(8): C02F11/00C02F11/127C02F11/121C02F11/143C02F101/20
CPCC02F11/00C02F11/121C02F11/127C02F11/14C02F2303/06C02F2101/20
Inventor 余震王跃强汤佳刘晓明周顺桂
Owner GUANGDONG INST OF ECO ENVIRONMENT & SOIL SCI
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