JPS6028774B2 - Aggregate manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing aggregate using industrial waste liquids. With the recent development of industry, a large amount and variety of industrial waste liquids are being discharged.

Many of these waste liquids contain harmful heavy metals. For example, plating waste liquid, etching waste liquid, glass processing waste liquid, etc. are one of them. BACKGROUND ART Research has been conducted into methods for disposing of waste liquids containing harmful metals in order to prevent them from polluting the environment. The most typical method was to dispose of the solid content or solidified waste liquid by turning it into cement and bran. Although this method is much safer than the case where the solid components of the waste liquid are simply dumped, it has been pointed out that there are still several points that need to be improved. This is because the ratio of cement to the solid content of the waste liquid is very high, requiring a large amount of cement, and there are restrictions on where to dump concrete. Even after mixing and forming concrete, there is still a risk that toxic metals will melt outside over time. In other respects, concrete obtained by mixing solid components of waste liquid with cement usually has low mechanical strength, and there is almost no possibility of using this concrete for other purposes. Therefore, the main purpose of the present invention is to safely treat waste liquid containing such harmful metals and to actively utilize the waste obtained as a result of the treatment.

The present invention is a process of separating a precipitate by adding a reagent for chemically converting the metal into a permanent metal compound and a flocculant for precipitating the formed metal compound to a waste liquid containing harmful metals, and a step of separating the precipitate. This method of producing aggregate is characterized in that the main steps are a step of mixing a material and a silicic oxide, and a step of firing this mixture. The aggregate obtained by the production method of the present invention is chemically very stable and has excellent mechanical strength.

Once the harmful metals originally contained in the waste liquid are contained as a skeleton, they will not be leached to the outside even under severe conditions. Furthermore, the mechanical strength of the obtained aggregate is greater than that of materials normally used as aggregate for concrete, and has a strength that can be used for various purposes. Instead of dumping the precipitate separated from the waste liquid, by mixing it with silicic oxide and firing it, the originally toxic metals are rendered harmless and used as an effective material. The invention provides a highly effective method for treating industrial waste liquids. Many of the harmful metals contained in industrial wastewater are contained in the wastewater as ions.

In addition, a portion is contained as an element or as a compound in a dissolved or suspended state. The main harmful metals are Cr,
Examples include Pb, Ni, C↓Cd, and Zn. In the most fundamental implementation of the present invention, a reagent and a flocculant for reacting with these metals to form a permanent metal compound are added to the waste liquid containing such metals. Amorphous metal compounds usually do not settle immediately and are often in a floating state. Metal compounds that are in a floating state or are about to become a floating state are precipitated by a flocculant,
It is separated from the waste liquid as a precipitate. As the flocculant, those commonly used as flocculants are used. Examples include china clay, bentonite, sodium silicate, aluminum sulfate, polyaluminum chloride, and ferric chloride. In particular Sumishi and Pentonite are used as better flocculants.

In order to make a metal into an insoluble metal compound, the composition of the compound should be appropriately determined. A specific substance required to form a defined insoluble metal compound is used as a reagent. When converting a metal into an insoluble metal hydroxide, a caustic alkali is used as the reagent. Furthermore, if it is difficult to form an insoluble compound as it is depending on the ionic state of the metal, a necessary reagent may be added to obtain another ionic state. The amount of silicic oxide mixed with the precipitate separated from the waste liquid is usually 1 to 9 parts by weight, assuming that the entire mixture of the precipitate and silicic oxide is 1 part by weight. In particular, it is preferable to mix in a proportion of 2 to 7 parts by weight. Note that this weight value is based on the weight (after drying) of the dry solid content of the precipitate. Typical silicic oxides include water clay,
These include mountain gravel sludge, glass waste, clay, and water glass. The mixture with the silicic oxide is usually fired into a shape suitable for ease of firing and the intended use. For example, it may have a granular shape such as a triangular prism, a spherical shape, or an oval shape, or a rod shape. Firing is typically carried out at a temperature in the range of 500 oo to 1300 oo. Since the aggregate produced in this way has excellent mechanical strength, it is expected to be used particularly as a construction material. One typical example is its use as aggregate for concrete. In this case, the size of the fired product is usually 0.1
It is preferable to set the particles in the size range of about 3 to 3 ribs. The affinity of aggregate for cement is excellent, and cement can be set in a small amount relative to aggregate. The strength of the manufactured concrete is also equal to or higher than that of ordinary concrete. Example 1 Pentony was added to polishing wastewater (wastewater discharged during the polishing of optical lenses) containing about 100 g of lead and trace amounts of barium and boric acid.

The amount of pentonite added was 500 ml per liter of waste water. Next, sodium hydroxide is added so that the pH of the wastewater becomes about 9.0, and then the wastewater is stirred for about 10 minutes before being transferred to another tank where wastewater 1 is applied and a polymer flocculant (in this case, polychlorinated (using aluminum) was added.

The resulting precipitate was separated from the supernatant water in a Clarifier, and the supernatant water was adjusted to pH 7.0 and discharged. On the other hand, the precipitate was dehydrated using a thickener and then a vacuum dehydrator to bring the moisture content to about 70%. Next, 4/5 weight of glass waste crushed to 50 mesh and 1/5 weight of mountain gravel sludge are added to the sediment using a V-type mixer, and about 1
After being mixed for an hour, it is pulverized into spherical particles with a diameter of about 1 cm by a pan-type granulator, and then placed in a hot air dryer for 110 cm.
It was dried for 4 hours at 0±10 degrees.

The resulting product had a drop breaking strength of 150 skin or more. After drying, the rotary kiln is used for the first stage of 500
The temperature was increased by 10°C for 1 minute at a final temperature of 850°C.
Baked for an hour. The resulting fired product has a consolidation strength of 100k9 or more, a specific gravity of 2.5, and a water absorption rate of 1.5.
%, it showed a value similar to that of natural aggregate. Baked product at 100o
A dissolution test was conducted by immersing the sample in pure water with a pH of 7.0 for 6 hours, but no harmful metals such as lead were detected. In addition, using the fired product as aggregate, the following concrete formulation (
JASS5) was conducted. Water-cement ratio Cement Sand 60% 93 volumes 331 volumes Burnt product admixture (Vinsol) 34 strings volume 0.062k9/remix the above composition using a portable mixer (50〆) to 30%
In the evening, we poured 1,000 x 20 pieces of concrete.

As a result, the compressive strength of the craned material after 7 days of age was 176
The compressive strength of K9/ after 28 days of age was 294 K9/, which is equivalent to that of ordinary concrete. As a comparison, in this example, when nitric lime was used instead of sodium hydroxide, the crushing strength of the obtained baked product was 5 to 20k9, and it easily crumbled when pressed with a finger. Met.

Furthermore, when nitrate lime was used, the results were the same even without adding a flocculant. Example 2 About 200 pieces of hexavalent chromium, about 200 pieces of nickel, about 10 pieces of lead
Q: The plating wastewater containing about 500 feet of blood and copper has a pH of about 3.
After sulfuric acid was added to zero, sodium metabisulfite was added to convert the chromium to trivalent chromium.

In addition, sodium hydroxide and 500 yen of thoracic acid per 1 liter of waste water were added to make the volume more than about 9.0 yen. Next, the resulting wastewater containing sediment was separated into the sediment introduced into the cruff ear and the top water, and the top water was adjusted to a bait of about 7.0 and then released. The precipitate was sequentially treated with a thickener and a vacuum dehydrator to bring the moisture content to around 80%. Clay was added to the precipitate in an amount approximately equal in weight to the dry solids of the precipitate and mixed in a fret mill mixer for approximately 30 minutes. Next, it was made into a sphere with a diameter of about 5 skins to 1 mound using a bread-shaped beletizer, and heated at 110°C ± 10qC for 4 hours in a hot air dryer.
dried in The breaking strength after drying is 80 skin or more.
After that, a multi-stage rotary kiln is used to reduce the initial temperature to 40
0oo, final temperature of 1180qo under heating conditions of 1 minute loo0
It was then baked for 2 hours. The resulting fired product has a pressing strength of 80k9 or more, a specific gravity of 2.11, and a water absorption rate of 4.
．． It was 77%. Crush the fired product to pH 95±500
7 in pure water and conducted two unique continuous melting tests, but no release of toxic metals such as hexavalent chromium was detected. Further, using this fired product as an aggregate, concrete was formed under the same conditions as in Example 1, and its strength was examined.

As a result, the compressive strength after 7 days of age was 162k9/m, and the compressive strength after 28 days of age was 265k9/m. In addition, the air-dried specific gravity of the material after 28 days was 2.05, which was lower than that of general concrete using natural aggregate and had the same strength. As a comparison, in this example, when nitric lime was used instead of sodium hydroxide, the compaction strength of the obtained fired product was 5 to 20k9 or less, and it crumbled easily when pressed with a finger. It was something to put away.

Claims (1)

[Claims] 1. A step of separating the precipitate by adding caustic alkali to chemically convert the insoluble metal compound from the metal and a coagulant to precipitate the metal compound to a waste liquid containing harmful metals, and separating the precipitate from the silicification. A method for producing aggregate, the main steps being a step of mixing materials and a step of firing the mixture.