CN102583916A

CN102583916A - Method for removing heavy metal from sludge

Info

Publication number: CN102583916A
Application number: CN2012100286781A
Authority: CN
Inventors: 李少华
Original assignee: Hubei Dingxin Environmental Protection Technology Co Ltd
Current assignee: Hubei Dingxin Environmental Protection Technology Co Ltd
Priority date: 2012-02-09
Filing date: 2012-02-09
Publication date: 2012-07-18

Abstract

The invention relates to a method for removing heavy metal from sludge. The method comprises the following steps of: extracting the heavy metal by using citric acid and hydrogen peroxide, performing microwave heating and solid-liquid separation, and adding sodium hydroxide to precipitate the heavy metal. The method is simple in process, the removal rate of the heavy metal is high, and consumption of acid is low; the citric acid solution can be recycled; the method is low in cost and does not harm the environment; and by adding the hydrogen peroxide into the extract, the extraction rate is improved, the reaction is quickened, and loss of available chemical elements such as N and P is reduced.

Description

A kind of method of removing heavy metal in the mud

Technical field

The present invention relates to the environmental treatment technical field, be specifically related to a kind of method of removing heavy metal in the mud.

Background technology

Mud is the solid precipitation material that is produced by water and sewage treatment process.Along with Increase of population and quickening of urbanization process, the output of municipal sludge increases day by day, forms new environmental problem.Traditional sludge treatment method is landfill, burning, throwing sea, and these processing modes are not fundamentally eliminated its influence to environment.Contain nutrition such as a large amount of soil ulmin, nitrogen phosphorus on the other hand in the mud, have huge recycling and be worth, these processing modes have obviously been wasted resource.But owing to contain heavy metal in the mud, greatly influenced the recycling of mud, and aggravated the risk of mud contaminate environment, the heavy metal of how effectively removing in the mud is the prerequisite that recycling sludge utilizes.After deliberation, the heavy metal that most of municipal sludge mainly contains is Cu, Zn, Pb, Hg, Ni, Cd, Cr, As, and wherein, Cu, Zn, Pb, Hg are topmost heavy metals, account for more than 95% of contained heavy metal.

The method of from mud, removing heavy metal mainly contains three major types: chemical method, biological process and physical method.Physics mode has absorption method and electrode method, EM etc.But these three kinds of physical methods all have its limit, can't widespread use.And the labile factor of biological process is more.Chemical method mainly is to utilize mineral acid or organic acid to leach metal, removes heavy metal element again.Yet there is the shortcoming that consumption acid is big, the time is long, expense is big in present chemical method.

Summary of the invention

The object of the present invention is to provide a kind of method of removing heavy metal in the mud, this method is simple to operate, acid consumption is few, heavy metal removing rate is high.

Technical scheme of the present invention is: in the mud environment, add the citric acid solution dissolving and leach the heavy metal in the mud, and add the redox potential that ydrogen peroxide 50 improves environment, accelerate to leach heavy metal; Microwave heating improves the temperature of environment, quickens to leach the carrying out of reaction, and system can be carried out in higher PH environment; Reduce the loss of useful elements such as N, P in the mud; And the recyclable utilization of Hydrocerol A reduces cost, the quick purpose of effectively removing heavy metal in the mud thereby reach.

The method of heavy metal may further comprise the steps in the removal mud of the present invention:

1) leaching of heavy metal: in sludge sump, add citric acid solution and ydrogen peroxide 50, stir;

2) microwave heating: step (1) gained solidliquid mixture is warming up to 50-80 ℃, insulation 50-100min;

3) solid-liquid separation: obtain the sewage sludge solid material and be used to make fertilizer, filtrating is carried out heavy metal and is removed processing;

4) deposition of heavy metal is separated out in the filtrating: in filtrating adds, add excessive sodium hydroxide, have deposition to disengage in the filtrating;

5) filter filtrating, the throw out that obtains is dried, otherwise processed.

After citric acid solution adds in the mud; Can extracting go out the heavy metal ion in the mud; The adding ydrogen peroxide 50 can improve the redox potential of system environment, improves the extract content of heavy metal ion, stirs to help the carrying out that heavy metal leaches reaction; Microwave heating has further quickened to leach the carrying out of reaction, has saved the time; Hydrocerol A with the abundant lixiviate of the heavy metal in the mud after, carry out solid-liquid separation, the sewage sludge solid material that obtains does not contain heavy metal; Can be used for making fertilizer or other agricultural use, and the filtrating that obtains contains the further processing of heavy metal needs, in filtrating, add sodium hydroxide; Heavy metal ion generation precipitin reaction in sodium hydroxide and the filtrating produces sedimentable matter, at this moment; Filtering filtrating just can separate heavy metal compound with filtrating; The filtrating that obtains mainly contains Hydrocerol A, can be reused in the heavy metal lixiviate of mud, and the throw out solid that obtains is otherwise processed then.

Preferably, the concentration of the citric acid solution that adds in the step 1) is 2～3mol/L, and every kilogram of mud adds the 2L citric acid solution, and to use nitric acid or sodium hydroxide to regulate PH be 5.

Preferably, the ydrogen peroxide 50 mass concentration that adds in the step 1) is 27.5～35%.

Preferably, stir on liquid feeding limit, limit in adding citric acid solution and ydrogen peroxide 50 process, the liquid feeding continued stirring 20～30min that finishes.

Preferably, adopt the method for centrifugal settling to carry out solid-liquid separation in the step 3), obtain the filtrating of sewage sludge solid material and dissolving heavy metal.

Compared with prior art, the invention has the beneficial effects as follows:

1. the recyclable utilization of vat liquor can not produce environment and pollute, and can save cost again;

2. add ydrogen peroxide 50 in the vat liquor; Improve the redox potential of environmental system, make the lixiviate of heavy metal fill more, both reduced the consumption of citric acid solution; The lixiviate reaction can be carried out in higher PH environment, reduce the loss of useful chemical elements such as N, P;

3. the carrying out of lixiviate reaction accelerated in microwave heating;

4. technological operation is simple, and heavy metal removing rate is high, and few with the acid amount, the time is short, and expense is low.

Embodiment

Below in conjunction with the practical implementation example the present invention is done further explain.

Embodiment 1

Mud is taken from husky certain sewage work of Hunan star, after wet mud is handled through oven dry, analyzes the heavy metal composition of sludge-drying sample, like table 1.

The heavy metal composition analysis (mg/Kg) of Wuhan, table 1 Hubei sludge of sewage treatment plants sample

Composition	Cu	Pb	Zn	Hg	Ni	Cr	Cd	As
									Content	480	190	841	104	8	73	4	19

Get primary sludge and place beaker for 1 kilogram, add the citric acid solution of 2L 2mol/L, stir on liquid feeding limit, limit; Then using nitric acid and sodium hydroxide to regulate PH is 5, and then to add the 0.5L mass concentration be 27.5% ydrogen peroxide 50, likewise; Stir on liquid feeding limit, limit, and the liquid feeding continued that finishes stirs 20min.

Adopt the above-mentioned mud solidliquid mixture of microwave heating, be heated to 50 ℃ after, insulation 100min lets Hydrocerol A with the abundant lixiviate of the heavy metal ion in the mud.

Adopt the method for centrifugal settling to carry out solid-liquid separation in the mud after the above-mentioned lixiviate, solid matter is used to make fertilizer to be recycled, and filtrating is surveyed its heavy metal content earlier, calculates the extraction rate of the heavy metal of 1 kilogram of mud again, result such as table 2.

The heavy metal analysis of the vat liquor of 1 kilogram of mud of table 2

After the lixiviate;, filtrating adds excessive sodium hydroxide in adding; The reaction of heavy metal ion and sodium hydroxide produces to precipitate and disengages in the filtrating, filters and promptly gets heavy metal precipitation thing and citric acid filtrate, the recyclable heavy metal that is reused for lixiviate mud of citric acid filtrate; The precipitated metal thing collects otherwise processed after drying treatment.

Embodiment 2

Mud is taken from the waste water treatment plant of Hubei Zhijiang printing and dyeing enterprise, after wet mud is handled through oven dry, analyzes the heavy metal composition of sludge-drying sample, like table 3.

The heavy metal composition analysis (mg/Kg) of the mud sample of the waste water treatment plant of table 3 Hubei Zhijiang printing and dyeing enterprise

Composition	Cu	Pb	Zn	Hg	Ni	Cr	Cd	As
									Content	535	210	923	86	15	64	12	5

Get primary sludge and place beaker for 1 kilogram, add the citric acid solution of 2L 3mol/L, stir on liquid feeding limit, limit; Then using nitric acid and sodium hydroxide to regulate PH is 5, and then to add the 0.5L mass concentration be 33% ydrogen peroxide 50, likewise; Stir on liquid feeding limit, limit, and the liquid feeding continued that finishes stirs 20min.

Adopt the above-mentioned mud solidliquid mixture of microwave heating, be heated to 80 ℃ after, insulation 50min lets Hydrocerol A with the abundant lixiviate of the heavy metal ion in the mud.

Adopt the method for centrifugal settling to carry out solid-liquid separation in the mud after the above-mentioned lixiviate, solid matter is used to make fertilizer to be recycled, and filtrating is surveyed its heavy metal content earlier, calculates the extraction rate of the heavy metal of 1 kilogram of mud again, result such as table 4.

The heavy metal analysis of the vat liquor of 1 kilogram of mud of table 4

Conclusion is analyzed: can know from above two embodiment; The combination of citric acid solution and ydrogen peroxide 50 and the reaction conditions of controlling well can obtain higher extraction rate; To the extraction rate of each heavy metal species all more than 90%; And more than 95%, extracting effect is better for the extraction rate of main several heavy metal species.

Claims

1. method of removing heavy metal in the mud is characterized in that may further comprise the steps successively:

4) deposition of heavy metal is separated out in the filtrating: in filtrating, add excessive sodium hydroxide, have deposition to disengage in the filtrating;

5) filter filtrating, the throw out that obtains is dried, otherwise processed.

2. the method for heavy metal in the removal mud as claimed in claim 1 is characterized in that: the concentration of the citric acid solution that adds in the step 1) is 2～3mol/L, and every kilogram of mud adds the 2L citric acid solution, and to use nitric acid or sodium hydroxide to regulate PH be 5.

3. the method for heavy metal in according to claim 1 or claim 2 the removal mud, it is characterized in that: the ydrogen peroxide 50 mass concentration that adds in the step 1) is 27.5～35%.

4. the method for heavy metal in the removal mud as claimed in claim 1 is characterized in that: stir on liquid feeding limit, limit in adding citric acid solution and ydrogen peroxide 50 process, the liquid feeding continued stirring 20～30min that finishes.

5. the method for heavy metal in the removal mud as claimed in claim 1 is characterized in that: adopt the method for centrifugal settling to carry out solid-liquid separation in the step 3), obtain the filtrating of sewage sludge solid material and dissolving heavy metal.