JPS61230785A - Removal of mercury in waste water - Google Patents

Abstract

PURPOSE:To make it possible to remove mercury up to a low level, by combining a flocculative sedimentation process, a sand filtering process and an adsorbing process by a chelate resin tower and preliminarily changing colloidal mercury to soluble mercury prior to guiding water to be treated to a chelate resin. CONSTITUTION:Waste water 1 containing mercury is guided to a flocculation treatment tank 2 to perform flocculative sedimentation treatment and sludge is separated in a sedimentation tank 3. Thereafter, flooded water is filtered through the sand bed in a first sand filter tower 4 to remove the suspended substance in water and a part of the filtered water is electrolyzed in an electrolytic cell 5 to generate chlorine and the electrolyzed water is met and mixed with non-electrolyzed water in an oxidizing tank 6 to decompose the org. substance and colloidal mercury by oxidation to convert metal mercury to soluble mercury. Next, the treated water is newly guided to a second sand filter tower 7 where the suspended substance generated as a by-product at the time of reaction is removed and the filtered water is passed through a chelate resin tower 8 at last to adsorb and remove a mercury ion by a chelate resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for removing mercury from mercury-containing wastewater, and particularly to a method for removing mercury from the wastewater to environmental levels.

[Conventional technology]

Conventionally, heavy metals in wastewater are generally treated by the coagulation-sedimentation method, but mercury has attracted attention due to its toxicity, as is known from Minamata disease, etc., and the environmental standard is 0.5pp.
Due to the strict electrical conductivity of less than b, the treatment cannot be achieved by coagulation-sedimentation alone. So 0.5 ppb
In order to reduce the concentration to such a low level, a method is generally used in which water is passed through a chelate resin column after coagulation and precipitation treatment.

[Problem that the invention seeks to solve]

However, simply treating coagulation-sedimentation treated water with a chelate resin causes colloidal mercury (mercury suspended in water, metal Hg, etc.) in the raw water to leak out, making it impossible to treat the water to a low concentration of 0.5 ppb or less. Can not.

The present invention provides a method for removing trace amounts of mercury from wastewater without such drawbacks.

[Means for solving problems]

In order to achieve the above objects, 1) the present invention carries out a coagulation-sedimentation treatment on mercury-containing wastewater, then performs a primary sand filtration treatment, electrolyzes at least a portion of the filtrated water from the sand filtration treatment in an electrolytic cell, and chlorinates We propose a method for removing mercury from wastewater, which is characterized by producing mercury and then passing the water through a chelate resin column.

[Effect]

In the method of the present invention, after coagulation and precipitation treatment is performed.

The first sand filtration treatment is performed, at least a portion of the sand filtration water is electrolyzed to generate chlorine, and the action of this chlorine decomposes cicoloidal mercury into complex anions, and then the second sand filtration treatment is performed. After the treatment, the resin is passed through a chelate resin tower.

That is, first, in the coagulation-sedimentation step, the pH of heavy metals such as Cd and PB is adjusted to generate hydroxide according to the following reaction formula, which is precipitated and removed together with a flocculant.

Cd ”+2Na oH-+ Cd (oH)2↓・・
-.- (1) In the next primary sand filtration step, suspended particles that could not be removed in the coagulation-sedimentation step are removed. If suspended particles are not removed, adverse effects such as increased chlorine consumption in subsequent steps will occur.

Furthermore, in the next electrolysis step, a portion of the sand-filtered water is electrolyzed to generate chlorine according to the following reaction formula.

(Cathode) H"+e→I H, ↑ ・・・・・・・・・
・(3) The generated chlorine and colloidal metal Hg are reacted according to the following reaction formula, and the metal Hg is oxidized to become soluble mercury (mercury dissolved in water) (O Hg + C12 → H-) + C4 -2・・・・・・・・・(
4) Next, the mixture is led to a second sand filtration step to remove suspended solids generated as a by-product in the reaction to prevent clogging of the chelate tower in the next step.

In the next chelate resin treatment step, the chelate resin undergoes a chelate reaction with mercury ions to selectively adsorb and remove mercury ions.

9 In the present invention, after electrolysis treatment.

To accelerate the reaction between chlorine and colloidal mercury.

A mixing step or stirring step for the water to be treated may be provided.

〔Example〕

Next, an embodiment of the method of the present invention will be described with reference to the drawings.

As shown in FIG. 1, mercury-containing wastewater 1 is introduced into a coagulation treatment tank 2, and 150 ppm of FeCl2 is added thereto.

Heavy metals such as Cd, Ni, and Zn are converted into Cd (0H)
2. To make Ni(0H)2Zn(oH)2 hydroxide, adjust the pH to 10-11 with NaoH, add 2 ppm of organic polymer flocculant, and add to the precipitation tank 3.
Separate the sludge.

After that, the overflow water is filtered with sand in the first sand filter tower 4 to remove suspended matter in the liquid, and then a portion of the sand filtered water (fishing of the entire flow rate)
is electrolyzed in the electrolytic tank 5 to generate about 5QQppm of chlorine, and then combined with the unelectrolyzed solution in the oxidation tank 6 and mixed.
Organic matter in liquid.

Oxidatively decomposes colloidal mercury. Next, after passing through the second sand filter tower 7, the water is passed through the chelate resin tower 8 to remove mercury.

Next, Table 1 shows the results of experiments using the above apparatus.

Huangqiu (1) Raw water: COD25ppm, CdCd1-7p
p pbloppm.

Zn90ppm, Hg0. Municipal waste incineration plant inorganic wastewater containing lppm (no each process ■ Organic polymer flocculant used in coagulation sedimentation tank 2 [Diafloc AP825j (product name. Manufactured by Diafloc Co., Ltd.) ■ Primary and secondary sand Filter tower 4 and 7 sand amount: 2t (76mφX 4
40mmH) Sand used: Silica sand 1-3+I! ! 1φ SV (space velocity): 2.5 1/hr LV (linear velocity): 1-1 m/hr Electrolytic cell 5 Electrolytic area: 12 J (3x4 wounds) Cathode: Titanium plate anode @ Pi, plated titanium plate Water flow rate: 0 .5 t/h Current flow: 0.5A ■Oxidation tank 6 1 Capacity: 2t ■Chelate resin tower 8 Resin amount: 1t (54mmφX440w+H) SV (space velocity): 51/hr LV (linear velocity) * 2.2rn /hr Chelate resin used: Sumikylate Q-10J (trade name. Sumitomo Chemical Co., Ltd. As shown in the experimental example, after water is passed through the second sand filtration tower 7, colloidal mercury is completely removed and soluble As a result, the mercury in the treated water after passing through the chelate resin tower was 0.1 ppb or less.

The reaction in the electrolytic cell 5 occurs as shown in equations (2) and (3) above, and chlorine is generated, so there is no need to collect the oxidizing agent. Further, by providing the second sand filter tower 7, clogging of the expensive chelate tower can be prevented.

According to this method, colloidal mercury is decomposed to fully demonstrate the performance of the chelate resin tower, and as a result, the effective period of the chelate resin tower can be extended.

〔Effect of the invention〕

As described above, according to the method of the present invention, a coagulation-precipitation process, a sand filtering process, and an adsorption process using a chelate resin tower are combined, and colloidal mercury is converted into soluble mercury before the water to be treated is introduced into the chelate resin. By changing the mercury in the water to be treated, it is possible to remove mercury to an extremely low level, and the water to be treated can meet environmental standards.

Note that the method of the present invention uses municipal waste incinerator wastewater.

It can be widely applied to the treatment of mercury-containing wastewater such as industrial waste, wastewater from waste treatment plants such as sewage sludge, and wastewater from various manufacturing plants.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing an embodiment of the method of the present invention. 1...Mercury-containing wastewater, 2...Coagulation treatment tank, 3...
Sedimentation tank, 4... First sand filter tower, 5... Electrolytic tank, 6...
... Oxidation tank, 7... Second sand filter tower, 8... Chelate tower.

Claims (1)

[Claims] After coagulation and precipitation treatment of mercury-containing wastewater, a primary sand filtration treatment is performed, and at least a portion of the filtrated water from the sand filtration treatment is electrolyzed in an electrolytic cell to generate chlorine, and the generated chlorine is used to remove colloidal mercury. A method for removing mercury from wastewater, which comprises converting the mercury into soluble mercury, then performing a secondary sand filtration treatment, and then passing the water through a chelate resin tower.