JP6550801B2 - Method of treating metal-containing sludge - Google Patents

Description

The present invention relates to a method for treating metal-containing sludge, and more particularly to a method for treating metal-containing sludge in which an alkali is added to metal-containing sludge containing titanium, magnesium and calcium, and subsequently a polymer flocculant is added.

Metal-containing sludge is generated from treatment processes such as mine wastewater, chemical factory wastewater, smelter wastewater, ironworks wastewater, plating factory wastewater, paint wastewater, and waste incineration wastewater.

Conventionally, as a treatment method of sludge and wastewater containing metal, including heavy metals, after treatment with an amphoteric polymer flocculant containing a bifunctional monomer unit (Patent Document 1), alkali coagulation precipitation, Methods (Patent Documents 2 and 3) for performing treatment with a polymer flocculant have been proposed.

However, any of the methods of Patent Documents 1 to 3 described above can not form a sufficiently strong floc that can withstand mechanical dewatering after floc formation. Therefore, there has been a problem that the amount of sludge treated per unit time can not be increased, and the moisture content of the cake can not be sufficiently reduced.

JP 10-309405 A JP, 2013-141641, A JP 2008-264626 A

The purpose of the present invention is to improve the sludge dewatering efficiency by reducing the cake moisture content by increasing the strength of the coagulated floc and forming a sufficiently strong floc that can withstand mechanical dewatering in the dewatering treatment of the metal-containing sludge. It is providing the dehydration method of the metal containing sludge which can be achieved.

As a result of intensive studies to solve the above problems, it is effective to add a specific polymer flocculant after adjusting the pH with an alkali to metal-containing sludge, particularly metal-containing sludge containing titanium, magnesium and calcium. As a result, the present invention has been completed.

That is, the present invention provides a metal-containing sludge that is dehydrated by adding an amphoteric polymer flocculant having a dialkylaminoalkyl methacrylate alkyl chloride quaternary salt structural unit after adjusting the metal-containing sludge to have a pH of 10 to 13. It depends on the processing method.

Further, the present invention resides in the method for treating metal-containing sludge according to claim 1, wherein the metal-containing sludge is a metal-containing sludge containing titanium.

Moreover, this invention exists in the processing method of the said metal containing sludge whose titanium concentration in the said metal containing sludge is 0.01-1 mass%.

Further, the present invention resides in the above-described method for treating metal-containing sludge, wherein the dialkylaminoalkyl methacrylate alkyl chloride quaternary salt structural unit is a dimethylaminoethyl methacrylate methyl chloride quaternary salt structural unit.

Furthermore, this invention exists in the processing method of the said metal-containing sludge which adds 200-500 ppm of said amphoteric polymer flocculents with respect to 100 mass parts of metal-containing sludge.

According to the metal-containing sludge treatment method of the present invention, in the dewatering treatment of metal-containing sludge, the sludge dewatering efficiency is improved by forming a sufficiently strong floc that can withstand mechanical dewatering by increasing the strength of the coagulation floc. It is possible to provide a method for dewatering metal-containing sludge which can achieve a reduction in the moisture content of the cake.

The present invention is described in detail below.
In the following, "ppm" is based on mass unless otherwise noted. In the method for treating metal-containing sludge of the present invention, a metal-containing sludge containing titanium, magnesium and calcium is adjusted to pH 10 to 13 to precipitate metal as a hydroxide. By adding 200 to 500 ppm of an amphoteric polymer flocculant having a dialkylaminoalkyl methacrylate alkyl chloride quaternary salt structural unit to the sludge, the polymer flocculant can be added to the sludge without causing an insufficient addition amount or an excess addition of the polymer flocculant. The aggregation action can be enhanced by causing entanglement of polymer chains by charge neutralization of suspended particles and further causing electrostatic interaction. For this reason, it is possible to form a floc having strength sufficient to endure mechanical dewatering in the post process, even for metal-containing sludge in which the floc tends to be fine. Therefore, the improvement of the amount of sludge treatment and the improvement of the dewatering effect of the cake can be expected.

The metal-containing sludge is not particularly limited as to the type and concentration of other components as long as it contains 0.01 to 1% by mass of titanium and further contains magnesium and calcium. The concentration of (hereinafter referred to as TS) is usually preferably 1.0% by mass or more, and more preferably 2.0% by mass or more. Moreover, 6.0 mass% or less is preferable and 5.0 mass% or less is more preferable. If it is within the above range, the flocs can be formed while the metal-containing sludge is pH-adjusted and the precipitated metal is wound around the flocs, so that the metal and solid matter in the sludge can be efficiently removed.

The pH adjustment of the metal-containing sludge can be performed by adding an alkali to the sludge. Examples of the alkali include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide. Above all, calcium hydroxide is preferable as the alkali for adjusting the pH, from the ease of metal deposition in the wastewater.

Calcium hydroxide is added to metal-containing sludge containing titanium, magnesium and calcium to adjust the pH to precipitate metal hydroxide. The pH after pH adjustment is preferably 10 or more, and more preferably 10.5 or more. Moreover, 13 or less is preferable. If the pH is less than 10, the metal in the sludge cannot be collected sufficiently. When the pH exceeds 13, when the amphoteric polymer flocculant used in the subsequent step is an ester compound, the ester group causes hydrolysis, and a floc having sufficient strength cannot be formed.

The polymer flocculant is preferably made into an aqueous solution and then mixed with sludge. 0.01 mass% or more is preferable normally, and, as for the density | concentration of the aqueous solution of a polymer coagulant | fever, 0.05 mass% or more is more preferable. Moreover, 2 mass% or less is preferable and 0.5 mass% or less is more preferable. If it is in the said range, a polymer flocculent can be efficiently added to the said sludge.

In the amphoteric polymer flocculant of the present invention, the cationic monomer structural unit is a dialkylaminoalkyl methacrylate alkyl chloride quaternary salt, and among them, dimethylaminoethyl methacrylate methyl chloride quaternary salt is preferable. The content of the dimethylaminoethyl methacrylate methyl chloride quaternary salt structural unit is preferably 40.0 to 52.5% by mass with respect to all the monomer structural units constituting the amphoteric polymer flocculant. As a nonionic monomer structural unit, acrylamide is preferable, and as an anionic monomer structural unit, acrylic acid (salt) is preferable. With respect to the total monomer structural units constituting the amphoteric polymer flocculant, the content of acrylamide structural units is 40.0 to 52.5% by mass, and the content of acrylic acid (salt) structural units is 5. It is preferable that it is 0-10.0 mass%.

Moreover, 200 ppm or more is preferable and, as for the addition amount to the sludge of the said amphoteric polymer flocculent of this invention, 250 ppm or more is more preferable. Moreover, 500 ppm or less is preferable and 350 ppm or less is more preferable. Within the above range, when the polymer flocculant is added and stirred, the polymer flocculant does not remain unreacted and the dewatering efficiency of the cake is improved.

By adding the amphoteric polymer flocculant to the sludge, the polymer chains are entangled due to the charge neutralization of the suspended particles in the sludge, and the agglomeration action is enhanced by causing electrostatic interaction. For this reason, it is possible to form flocs having sufficient strength to withstand mechanical dehydration in the subsequent process even for metal-containing sludge that tends to be fine. Therefore, the improvement of the amount of sludge treatment and the improvement of the dewatering effect of the cake can be expected.

When the amphoteric polymer flocculant of the present invention is added to the sludge, an inorganic coagulant or an organic coagulant can be used in combination.

Examples of the inorganic coagulant include sulfuric acid band (aluminum sulfate), ferric chloride, ferrous sulfate, polyferric sulfate and the like. Of these, a sulfuric acid band is preferred because of its high sludge dewatering performance.

Examples of the organic coagulant include polyamine, polydiallyldimethyl ammonium chloride, polydialkylaminoalkyl methacrylate alkyl chloride quaternary salt, poly (dialkylamino alkyl acrylate alkyl chloride quaternary salt-acrylamide), cationic surfactant and the like. It can be mentioned. Polydialkylaminoalkyl methacrylate alkyl chloride quaternary salt and poly (dialkylaminoalkyl acrylate alkyl chloride quaternary salt-acrylamide) are preferred because of their high sludge dewatering performance.

After the floc is formed, the floc can be dewatered using a dehydrator to obtain a dewatered cake. As a form of a dehydrator, for example, filter press dehydrator, screw press dehydrator, press-in screw press dehydrator, vacuum dehydrator, belt press dehydrator, centrifugal dehydrator, multiple disc dewatering Machine etc. Among them, a filter press type dehydrator and a belt press type dehydrator are preferable because sludge dewatering efficiency is high.

Hereinafter, the present invention will be described in detail by showing Examples and Comparative Examples, but the present invention is not limited by the following description as long as the gist thereof is not exceeded. In addition, "%" in a present Example and a comparative example shows "mass%" unless there is particular notice.

Table 1 shows polymer flocculants used in Examples and Comparative Examples. The numerical values in the table indicate the content of the cationic monomer structural unit, the anionic monomer structural unit, and the nonionic monomer structural unit in each polymer flocculant in mass%.

AAm: acrylamide DME: dimethylaminoethyl acrylate methyl chloride quaternary salt DMC: dimethylaminoethyl methacrylate acrylate methyl chloride quaternary salt MBAA: methylene bis acrylamide AA: acrylic acid (salt)

Example 1
Calcium hydroxide was added to the paint-based metal-containing sludge containing titanium, magnesium and calcium to adjust to pH 11.8. The adjusted TS of the sludge was 5.38% as measured according to the Japan Sewage Works Association, Japan, Sewage Test Method, Volume 1997, p. Moreover, when titanium content of the sludge after pH adjustment was measured by the ICP emission-spectroscopic-analysis method of JISH1632-1: 2014, it was 0.05 mass%. Take 300 mL of the above sludge in a 500 mL beaker, add 25 mL (addition rate to sludge: 250 ppm) of amphoteric polymer flocculant A (aqueous solution concentration 0.3 mass%), stir with 200 rpm for 30 seconds using a spatula to make floc It formed. The average floc diameter was measured visually to obtain a floc diameter. The sludge formed by floc was filtered with a 50 mesh nylon filter cloth, and the turbidity of the filtrate was visually evaluated. The turbidity of the filtrate was judged based on the following criteria.

-: The filtrate is almost clear and almost no suspended matter can be seen (SS amount standard: less than 50 ppm).
+: Partial turbidity is observed in the filtrate, and a slight amount of suspended matter (SS amount standard: 50 ppm or more and less than 100 ppm).
++: Partial turbidity is observed in the filtrate, and suspended matter is present in some places (SS amount standard: 100 ppm or more and less than 200 ppm).
+ ++: A large amount of turbidity is observed in the filtrate, and suspended matter is totally present (SS amount standard: 200 ppm or more and less than 500 ppm).
++ ++: A large amount of turbidity is generally observed in the filtrate, and a suspended matter is present in whole and partially in coarse size (SS amount standard: 500 ppm or more and less than 1000 ppm).

After filtration, the floc remaining on the filter cloth was press-dehydrated at a pressure of 0.1 MPa for 1 minute to obtain a dehydrated cake, and the moisture content of the dehydrated cake was measured. The moisture content was measured in accordance with the Japan Sewage Association of Japan, "Sewage test method upper volume 1997 edition" p.

(Example 2)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant B.

(Example 3)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant C.

(Example 4)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 10.3.

(Example 5)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 12.5.

(Example 6)
The treatment was performed in the same manner as in Example 1 except that the addition rate of the amphoteric polymer flocculant A to the sludge was 200 ppm.

(Example 7)
The treatment was carried out in the same manner as in Example 1 except that the addition rate of the amphoteric polymer flocculant A to the sludge was 400 ppm.

(Comparative example 1)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant D.

(Comparative example 2)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant D.

(Comparative example 3)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 9.2.

(Comparative example 4)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 13.8.

(Comparative example 5)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the cationic polymer flocculant F.

(Comparative example 6)
Treatment was carried out in the same manner as in Example 1 except that the amphoteric polymer flocculant A was replaced by the addition of 75 mL (addition rate to sludge: 250 ppm) of the anionic polymer flocculant G (aqueous solution concentration 0.1 mass%). went.

The test results in Examples and Comparative Examples are shown in Table 2.

(Example 8)
Calcium hydroxide was added to the paint-based metal-containing sludge containing titanium, magnesium and calcium to adjust the pH to 10.9. The TS of the adjusted sludge was 4.59%. Moreover, when content of titanium was measured by the ICP emission spectrochemical analysis as described in JISH1632-1: 2014, it was 0.65 mass%. 300 mL of the above sludge was taken in a 500 mL beaker, 35 mL (addition rate to sludge: 350 ppm) of amphoteric polymer flocculant A (aqueous solution concentration 0.3%) was added, and stirred for 30 seconds at 200 rpm using a spatula. The measurement of the floc diameter, the determination of the turbidity of the filtrate, the preparation of the dehydrated cake and the measurement of the water content were carried out in the same manner as in Example 1.

(Example 9)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant B.

(Example 10)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant C.

(Example 11)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 10.0.

(Example 12)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of the sludge with calcium hydroxide was adjusted to pH 13.0.

(Example 13)
The treatment was performed in the same manner as in Example 1 except that the addition rate of the amphoteric polymer flocculant A was set to 200 ppm.

(Example 14)
The treatment was performed in the same manner as in Example 1 except that the addition rate of the amphoteric polymer flocculant A was changed to 450 ppm.

(Comparative example 7)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant D.

(Comparative example 8)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the amphoteric polymer flocculant E.

(Comparative example 9)
The treatment was performed in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 9.5.

(Comparative example 10)
The treatment was carried out in the same manner as in Example 1 except that the pH adjustment of sludge with calcium hydroxide was adjusted to pH 14.0.

(Comparative example 11)
The treatment was performed in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the cationic polymer flocculant F.

(Comparative example 12)
Treated in the same manner as in Example 1 except that the amphoteric polymer flocculant A was changed to the addition of 117 mL (addition rate to sludge: 350 ppm) of the anionic polymer flocculant G (aqueous solution concentration 0.1 mass%) Did.

The test results in Examples and Comparative Examples are shown in Table 3.

As shown in Tables 2 and 3, according to the treatment method of the present invention, as in Examples 1 to 7 and Examples 8 to 14, the floc diameter increases and the water content decreases. On the other hand, when the pH of the sludge after pH adjustment deviates from 10 to 13 as in Comparative Examples 3, 4, 9 and 10, the flock diameter becomes small and the water content becomes high.

Further, as in Comparative Examples 1, 2, 7 and 8, when the cationic monomer structural unit in the amphoteric polymer flocculant is different, the water content does not decrease.
Also in the case where the treatment is carried out with only the cationic polymer coagulant or only the anionic polymer coagulant, it is difficult to form a floc and the water content does not decrease.

ADVANTAGE OF THE INVENTION According to this invention, an alkali is added to metal containing sludge and it can apply widely as a processing method of the metal containing sludge which adds a polymer flocculant continuously.

Claims (7)

After adjusting the metal-containing sludge to have a pH of 10 to 13, it has a dimethylaminoethyl methacrylate methyl chloride quaternary structural unit as a dialkylaminoalkyl methacrylate alkyl chloride quaternary structural unit, and an acrylic acid salt as an anionic structural unit ( A method for treating metal-containing sludge, which comprises dehydrating treatment by adding an amphoteric polymer flocculant having a salt) structural unit and an acrylamide structural unit as a nonionic structural unit ,
The amphoteric polymer flocculant comprises 40.0 to 52.5% by mass of dimethylaminoethyl methacrylate methyl chloride quaternary salt structural unit and acrylamide structural unit with respect to all monomer structural units constituting the amphoteric polymer flocculant. The processing method of the metal-containing sludge characterized by containing 40.0-52.5 mass% of content, and 5.0-10.0 mass% of acrylic acid (salt) structural units. The method for treating metal-containing sludge according to claim 1, wherein calcium hydroxide is added to the metal-containing sludge to adjust to pH 10-13. The metal sludge is obtained in the treatment process of mine wastewater, chemical factory wastewater, smelter wastewater, steelworks wastewater, plating factory wastewater, paint wastewater and waste incineration wastewater. The processing method of the metal-containing sludge as described in a term. The method for treating metal-containing sludge according to any one of claims 1 to 3, wherein the metal-containing sludge is a metal-containing sludge containing titanium. The method for treating metal-containing sludge according to claim 4, wherein the concentration of titanium in the metal-containing sludge is 0.01 to 1% by mass. The density | concentration of the solid substance in metal containing sludge is 1.0 mass% or more and 6.0 mass% or less, The processing method of the metal containing sludge as described in any one of Claims 1-5. The method for treating metal-containing sludge according to any one of claims 1 to 6, wherein 200 to 500 ppm of the amphoteric polymer flocculant is added to 100 parts by mass of the metal-containing sludge.