JP2009189906A - Alkaline wastewater treatment agent - Google Patents

Abstract

An object of the present invention is to provide an alkaline wastewater treatment method that reduces environmental pollution.
[MEANS FOR SOLVING PROBLEMS] The present invention is characterized in that a polymer compound having a pH buffering performance is used to adjust the pH of alkaline drainage generated during the demolition of a concrete structure and when processing concrete waste into recycled crushed stone. .
[Selection figure] None

Description

  INDUSTRIAL APPLICABILITY The present invention can adjust the pH of drainage without deviating pH to 5.5 or less even when excessively added to alkaline drainage generated when demolishing a concrete structure and processing concrete waste into recycled crushed stone. A polymer compound-containing liquid material having a pH buffering function.

  When dismantling a concrete structure, such as a building, or when processing a piece of concrete produced as a waste material as recycled crushed stone, it is common practice to apply water to prevent dust from scattering. In addition, in seismic reinforcement work such as buildings and piers, a method of cutting the surface of existing concrete with a high-pressure water jet is generally performed. The waste water containing dust of concrete generally exhibits high alkalinity and sometimes has a pH exceeding 12. If these wastewaters were drained as they were, they would affect the environment.

In order to solve this problem, it is equipped with a powdered organic acid for adjusting the pH of alkaline wastewater and a pair of spunbond nonwoven fabrics sandwiching this powder. When alkaline wastewater is passed, citric acid dissolves. Thus, a wastewater treatment method for adjusting the pH of alkaline wastewater has been proposed (see Patent Document 1).
JP 2006-102705 A

  In the case of dismantling the concrete structure described above or processing into recycled crushed stone, the generated waste water can be recovered and a pH adjuster such as an acid can be added and neutralized. However, in order to collect all wastewater, appropriate storage facilities and neutralization facilities are required. Especially in the dismantling of concrete structures, the construction site is not constant, so it is necessary to move the storage facilities and neutralization facilities, which is only used for large-scale construction in terms of cost and technology. difficult. Therefore, there is a demand for a wastewater treatment method that can be used in small and medium-sized construction.

  Patent Document 1 includes a pair of spunbond nonwoven fabrics that support a powdered organic acid, and a wastewater treatment method that adjusts the pH of the alkaline drainage by dissolving the organic acid by passing the alkaline drainage through the nonwoven fabric. This suggests that storage facilities and neutralization facilities may be unnecessary. However, in the technique of Patent Document 1, it is necessary to obtain in advance the amount of acid necessary for adjusting the pH of the alkaline waste water as described in the text of the document. Once it can be stored, it is possible to determine the required amount, but when draining water from a water jet directly, it is difficult to determine the required amount of acid, and storage facilities are also required. Necessary. In addition, a certain amount of expertise is required to determine the required amount of acid. In the unlikely event that an acid is added in excess, there is also the possibility of generating acidic waste water.

  When there are rivers, lakes, and seas in the vicinity of the construction site, there are cases where alkaline drainage flows and pollutes fishing grounds. In light of these circumstances, in recent years, there have been local governments that have stipulated regulations on alkaline drainage generated by dismantling concrete structures and processing them into recycled crushed stone, which has become a major social problem.

  Therefore, in order to solve such problems, the present invention provides an alkaline wastewater treatment method for reducing environmental pollution, characterized by using a polymer compound having pH buffering performance to adjust pH of alkaline wastewater. The purpose is to provide.

  The present invention is characterized in that a polymer compound having a pH buffering performance is used to adjust pH of alkaline drainage generated at the time of dismantling a concrete structure and processing a concrete waste material into recycled crushed stone.

  According to the present invention, it is possible to neutralize at a low cost without the need for a facility for storing alkaline wastewater generated when demolishing a concrete structure and when processing concrete waste into recycled crushed stone, or special facilities for neutralization. Can be treated and drained, greatly reducing environmental pollution.

  The first aspect of the present invention is water used for preventing dust scattering during the dismantling of a concrete structure, water used for preventing dust scattering and cooling when processing into recycled crushed stone, and water. A polymer compound having a pH buffering capacity is previously added to water used in the jet. The polymer compound used at this time must contain 3 mmol / g or more of carboxyl groups, and if it is less than 3 mmol / g, the amount necessary for obtaining sufficient pH buffering properties increases, which is disadvantageous in terms of cost. . When the polymer compound is added to water, some of the carboxyl groups contained in the water so that the pH of the water is 5.5 or higher are alkali metal ions, alkaline earth metal ions, ammonium ions, quaternary ammonium ions. It is necessary to neutralize with one or more kinds of cations selected from As a result, even if it is excessively added, the pH does not become 5.5 or less. When used in a water jet, the polymer compound having a pH buffering function is preferably in the form of fine particles that do not dissolve in water. When the polymer compound is dissolved, the viscosity of the liquid is remarkably increased, so that it is difficult to inject at a high pressure like a water jet, which is extremely disadvantageous in terms of cost and technology. In this case, the particle diameter depends on the diameter of the injection nozzle, but is preferably 50 μm or less, more preferably 10 μm or less. The concentration of the polymer compound in the liquid material is preferably 5% by mass to 20% by mass.

  The second mode of the present invention is to add to water used (sprayed) to prevent dust from concrete pieces processed as recycled crushed stone. Recycled crushed stones are often piled up outdoors, and when the surface is dry, there is a high possibility of generating dust and polluting the surrounding environment. Moreover, when exposed to rain, there is no denying the possibility that alkaline drainage will occur due to the surface being washed away. By applying water with a pH-buffering polymer compound to recycled crushed stones, etc. that are piled outdoors, the alkaline components on the surface are neutralized in advance even when exposed to rain. Can be reduced.

  Although dependent on the second embodiment, since the present invention uses a polymer compound, the polymer compound is adsorbed on the concrete surface after being subjected to recycled crushed stone and the like, and a water retention layer is formed. The speed can be reduced. In addition, when the powder is dried, the fine powder that is scattered by the wind is fixed or agglomerated to prevent scattering and reduce environmental pollution. In both the first and second embodiments, the polymer compound may be water-soluble unless an increase in viscosity is a problem except in special cases such as a water jet.

  Examples of polymer compounds having pH buffering performance that can be employed in the present invention include polyacrylic acid polymers, methacrylic acid polymers, maleic acid polymers, and fumaric acid polymers. It is not limited to this.

Next, the present invention will be described with reference to examples and comparative examples.
A cleaning liquid obtained by washing 1 kg of recycled crushed stone (crushed concrete waste material) with 100 g of ion-exchanged water was used as alkaline drainage. The pH of the alkaline drainage was 11.3. As a result of neutralization titration with dilute hydrochloric acid, the alkali content was 4.5 × 10 ⁻³ meq / g.

Example 1
A liquid water retention material Espec L (polysodium acrylate, particle size of about 1 μm, solid content 9%) manufactured by Toyobo Co., Ltd. was dried as a polymer compound having pH buffering performance, and the solid content was taken out as Sample 1. It was 7.0 mmol / g when the amount of carboxyl groups of sample 1 was quantified. The pH when the dried product was dispersed again in ion-exchanged water at 9% by weight was 7.0. The above-mentioned 9% dispersion of the polymer compound was added to 100 g of the above alkaline waste water, and the change in pH was examined. When 20 g was added, the pH dropped to 9, and 50 g dropped to 8. After that, it gradually decreased, but finally became constant at 7.2.

Example 2
After adjusting the pH to 5 by adding sulfuric acid to liquid water retention material Espec L manufactured by Toyobo Co., Ltd., the solid content was taken out and used as sample 2. When pH was measured in a state where sample 2 was dispersed in ion-exchanged water so as to be 9% by weight, it was 5.5. As in Example 1, the pH change was observed while adding the 9% dispersion of Sample 2 to 100 g of alkaline waste water. When 10 g was added, the pH dropped to 9 and reached 7 at 35 g. The addition was continued, but the pH did not drop below 5.8.

Comparative Example 1
After adjusting the pH to 3 by adding sulfuric acid to liquid water retention material Espec L manufactured by Toyobo Co., Ltd., the solid content was taken out and used as sample 3. When pH was measured in a state where sample 3 was dispersed in ion-exchanged water so as to be 9%, it showed 3.8. As in Example 1, the pH change was observed while adding the 9% dispersion of Sample 3 to 100 g of alkaline waste water. When 4 g was added, the pH dropped to 9 and became 20 or less at 20 g. As a result of continuing the addition, the pH was 5.5 or less, which was outside the lower limit of the drainage standard.

Example 3
A polymer was obtained according to a conventional method using ammonium sulfate as a polymerization initiator in ion-exchanged water at a weight ratio of acrylonitrile 90 to methyl acrylate 10 and a total monomer concentration of 10%. Next, the polymer was introduced with a crosslinked structure in a 20% aqueous hydrazine solution at 90 ° C. and then hydrolyzed with a 5% aqueous sodium hydroxide solution to give a carboxyl group-containing polymer having a carboxyl group content of 5 mmol / g. A compound was obtained. This polymer compound was dispersed in ion-exchanged water, and sulfuric acid was added to adjust the pH to 6. Then, the solid content was taken out and used as sample 4. When pH was measured in a state where sample 4 was dispersed in ion-exchanged water so as to be 9%, it was 6.2. As in Example 1, the pH change was observed while adding the 9% dispersion of Sample 4 to 100 g of alkaline waste water. When 19 g was added, the pH dropped to 9 and reached 7 at 47 g. The addition was continued, but eventually became constant at 6.3.

Comparative Example 2
After introducing a crosslinked structure in the same manner as in Example 3, hydrolysis was performed with a 2% aqueous sodium hydroxide solution to obtain a carboxyl group-containing polymer compound having a carboxyl group content of 1 mmol / g. This polymer compound was dispersed in ion-exchanged water and sulfuric acid was added to adjust the pH to 5. Then, the solid content was taken out and used as Sample 5. When pH was measured in a state where sample 4 was dispersed in ion-exchanged water so as to be 9%, it showed 5.8. As in Example 1, the pH change was observed while adding the 9% dispersion of Sample 5 to 100 g of alkaline waste water. It took 70 g to lower the pH to 9, which was insufficient as a neutralizing effect of the waste water.

Example 4
A 9% dispersion of a polymer compound derived from Espec L manufactured by Toyobo Co., Ltd. having a pH of 7.0 was prepared in the same procedure as in Example 1. The pH of the washing liquid when washing 1 kg of the reclaimed crushed stone with 100 g of a solution obtained by diluting the dispersion 10 times was 7.8, which was significantly lower than the pH 11.3 when washing with the above-mentioned ion exchange water.

  INDUSTRIAL APPLICABILITY The present invention can be applied to neutralization of alkaline drainage generated at the time of dismantling a concrete structure and processing concrete waste into recycled crushed stone.

Claims (3)

  A polymer compound-containing liquid material having a pH buffering performance for treating alkaline wastewater generated when demolishing a concrete structure and processing concrete waste into recycled crushed stone.   The polymer compound having pH buffering performance contains 3 mmol / g or more carboxyl group as a pure polymer compound, and a part of the carboxyl group is an alkali metal ion, alkaline earth metal ion, ammonium ion, quaternary 2. The polymer compound-containing liquid according to claim 1, wherein the liquid is neutralized with at least one cation selected from ammonium ions, and the pH of the liquid is 5.5 or more.   2. The polymer compound-containing liquid according to claim 1, wherein the polymer compound having a pH buffering performance is in the form of fine particles and is a dispersion that maintains the shape of the fine particles without dissolving in the liquid.