JPH03157107A - Silica-based liquid flocculant and its production - Google Patents

Abstract

PURPOSE:To obtain the silica-based liq. flocculant excellent in flocculating effect by using a silica-alumina-calcium soln. obtained by dissolving a material contg. acid-soluble silica, acid-soluble alumina and acid-soluble calcium in acid as the essential component of the flocculant. CONSTITUTION:The material such as slag contg. the acid-soluble silica, alumina and calcium is dissolved in reducing acid or neutral acid to obtain a silica- alumina-calcium soln. which is used as the essential component of the flocculant. The flocculant is polymerized and gelled in weakly alkaline water due to the presence of salt. When the flocculant is gelled, the metal cation, ion of an alkaline-earth metal such as Ca, part of anion, surfactant, etc., dissolved in the water are combined with silica, integrally polymerized and gelled. The fine particles of protein, fat, etc., suspensoid, suspended matter, etc., are adsorbed by the silica, integrally polymerized, gelled and separated from the water. The silica-based liq. flocculant can be preserved for a long period by holding its pH at about 2.5-3.5 or decreasing the CaO concn. in the liq.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a novel method for extracting, coagulating, and removing contaminants contained in water, such as various dissolved substances, fine particles, and suspended substances. The present invention relates to a novel method for producing a silica-based flocculant and an excellently stable flocculant, in particular the polymerization/gelation phenomenon of monomer silica dissolved in water, A 6 +3 and Ca
42, etc., and Af”3 and Ca +2
This invention relates to a silica-based flocculating liquid that exhibits excellent extraction and flocculating effects through chemical reactions and synergistic effects with adsorption racks, and a method for producing the same.

[Conventional technology] Conventionally, extraction, coagulation, and removal of dissolved substances (ions), organic and inorganic particles, suspended substances, etc. from sewage and various wastewaters have been carried out using
Mainly AJ flocculants, Fe flocculants, and polymer flocculants are used.

A7 of these! Flocculants (Punk, Bando) utilize only the flocculating effect related to hydroxide production of A/, and are effective only when the pH of the target water is around neutral, and is effective against acidic water and strong No effect on alkaline water. Therefore, pH adjustment (OH-containing supply) operation is required before and after the addition, and it is also necessary to promote flocculation by adding an organic polymer flocculant.

Moreover, the dehydration properties of the obtained sludge are poor, and its treatment is difficult. Furthermore, since it is based on ion adsorption, it is effective for extraction and coagulation of anions such as PO4'2, so4"2, and HCO3- in water, as well as suspended solids such as surfactants, emulsions, lime wastewater, cement wastewater, etc. , is not suitable for removal.

On the other hand, like the Ae flocculant, the Fe-based flocculant only exhibits the flocculating effect associated with hydroxide production, and what is worse is that it leaves Fe+2 and Fe'' in the water after treatment. The residual ions cannot be sufficiently removed even if the solution is made alkaline by adding OH- after adding the flocculant.

Moreover, in both cases, it is essential to use a polymer flocculant, but since the polymer flocculant has particularly high hydrophilicity, there is a fear that a part of it will be discharged into the natural world together with the treated water.

AN flocculants, Fe flocculants, and polymer flocculants have the above-mentioned inconveniences, and are effective only for specific extraction and flocculation targets. Therefore, treatment costs (including sludge treatment) are high, delicate management is required, and the impact of polymer flocculants on the environment cannot be ignored.

Therefore, the present inventors have developed a system for creating a solution for water inclusions that utilizes the phenomenon in which dissolved ions and suspended substances and silica combine with or adsorb them during the process in which dissolved monomer silica polymerizes in an aqueous solution through an ionic reaction and then gels. (Japanese Patent Application No. 1-136898). Then, we developed a method that uses a highly concentrated acid-dissolved silica, car alumina solution as a type of fused silica.

[Problem N to be solved by the invention] This highly concentrated acid-dissolved silica alumina solution can effectively extract and coagulate contaminants in a small amount (ratio) of wastewater, especially in a slightly acidic region, but it can The problem was that it lacked stability, such as gelation.

That is, this acid-dissolved silica alumina solution is a supernatant liquid obtained by dissolving mineral slag powder with dilute sulfuric acid, and contains substantially a large excess of A.
Contains I +3 and Ca +2, etc., and even if the pH is maintained at 2.0, which is considered to be the parallel point of polymerization progress by +(", OH- donation of fused silica), silica polymerization-gelation progresses for a short time. It had the disadvantage of solidifying.

[Means for Solving the Problems] Therefore, the present inventor continued research on the acid-dissolved silica-alumina solution and succeeded in developing a stabilizing technique.

That is, the silica-based agglomerate of the present invention is a silica-based agglomerate obtained by melting a material containing acid-soluble silica, acid-soluble alumina, or acid-soluble calcium, such as mineral slag, with dilute sulfuric acid, dilute hydrochloric acid, or the like.
Main component is alumina-calcium solution. In addition, in order to ensure its long-term storage stability, the pl+ of the solution was adjusted to 2.5.
The amount of dissolved calcium in the solution is adjusted to about 3.5 or lower.

It is generally believed that when silica (SiO2) is dissolved in water, it is bonded to OH- (SiOH), and in particular, when the amount of dissolved silica exceeds 1100 pp, S t (O
H) 4 (monomer silica, monosilicic acid, small silicic acid) is said to be promoted (The Che
mistry of 5ilicon: Ra1pf
K, IIer).

This monomer silica exists in water in the form of hydrosil, and is known to exhibit special behavior and ionic reactions that differ from other ions.

In other words, monomer silica undergoes silanolization and polymerization/gelation in acidic water, and in particular, because it has double charges (dipolar), it cannot adsorb substances with each charge of ■ and O. Known. However, the reaction rate is pH2
In the range of ~7, it is proportional to the OH- ion concentration, and p1
It is said that when the hydrogen ion concentration is below 12, dehydration progresses in proportion to the hydrogen ion concentration. Further, in the slightly acidic region around FIH 4 to 6, particle growth is achieved, and particle aggregation and gelation rapidly proceed in a simultaneous manner.

Furthermore, in alkaline water, it is said that depolymerization of polymer silica occurs at p)19 or higher, but in weakly alkaline water, polymerization → gelation is said to proceed due to the presence of salt. This is because the monomer silica has the property of being extremely unstable and prone to condensation (ionic reaction), and depending on the concentration, temperature, and P T ( Polymerization progresses to form polymer silica (polysilica) through siloxane bonds. As the condensation reaction progresses, H+ is released, rapidly promoting polymerization and gelation of the fused silica (around ρpm 4 to 6). ), gelation of fused silica is further promoted.

During this gelation, Zn, Pb, and
Metal cations such as As, alkaline earth metal ions such as Ca, some anions such as p-3, and dissolved substances such as cationic surfactants combine with silica to integrally polymerize and form a gel (
In addition, fine particles such as proteins and fats, suspended solids, suspended solids, etc. are adsorbed to the silica and integrally polymerize and gel (
flocculation), so that these aqueous contaminants are separated from the water.

The present invention utilizes this phenomenon for purposes such as purifying sewage.

Furthermore, gelled silica is highly stable and has the characteristic that back extraction does not occur in its natural state.

Furthermore, A I +3, Ca
32, polymerization occurs when cations such as M g +2 are present.
The above-mentioned application by the present inventor revealed that the gelation reaction progresses rapidly. However, although AN2 alone promotes polymerization and gelation, Ca +2 and M g "'
It will only have a great effect if it coexists with N+3.

This is due to alumina modification resulting from so-called interaction in which A I +3 replaces silica within the silica polymer at the molecular level, and combines with silica to form a composite precipitate, while simultaneously producing a large amount of H+. This seems to be due to the phenomenon.

(-5iOH)m +Al"3= (-3iOH)m-n ・ (-31o)nAl◆3
+n H+ Moreover, Al”3 is O in water at pH > 4.
Combines with H- to form aluminum hydroxide, where
It adsorbs suspended substances in water, phosphate ions, and other cations and precipitates.

On the other hand, Ca' and Mg' are HCO3-, So, 1''
It chemically combines with 2 to produce hard-to-melt precipitates to enhance the coagulation and precipitation effect, or to extract and remove them.

In addition, in alkaline water, these salts, especially 0.2
In the coexistence of a salt of N or more, monomer silica undergoes grain growth independently and has the characteristic of rapidly gelling due to the loss of charge due to neutralization.

The amount of monomer silica dissolved is inversely proportional to the amount of H, and the amount of silica dissolved is inversely proportional to the amount of H.
Although proportional to the amount of H, it has usually been difficult to obtain monomeric silica in practice, especially at high concentrations. That is, silica (SiO2) does not dissolve in strong acids, but partially dissolves in strong alkalis, but quickly gels as the pH decreases.

As a result of various research, the present inventors focused on slag containing a large amount of silica and tried dissolving it with dilute sulfuric acid and dilute hydrochloric acid, and found that a highly concentrated acid-dissolved silica-alumina-calcium solution was obtained very easily. It was done. Of course, various materials containing acid-soluble silica, acid-soluble alumina, and acid-soluble calcium can be used, including not only slag but also cement, bentonite (mixed with other materials that do not contain calcium), but they are inexpensive and Mine slag is the most preferred because it can be obtained in large quantities.

Mine slag (blast furnace slag, converter slag, electric furnace slag) is
The main and subcomponents are O2, Al 203, CaO, MgO, etc. And if they are for example Cao 5i
Calcium silicates such as Oz, 2cao-3iOz,
2CaO5i02 Aj! These composite crystals such as calcium silicate aluminates such as 203 are easily dissolved in acids because St, AN, and Ca are bonded through 0, and SiO2 itself is mainly metastable silicic acid. Because it is of the so-called α-cristobalite type, it is easily melted, and slag is easily dissolved by dilute acid.

As the acid, a reducing acid such as hydrochloric acid (HCl) or an organic acid, or a neutral acid such as sulfuric acid (H2SO4) (which takes on the properties of a reduced acid when diluted) is used. These are used diluted to 2N or less. If the concentration is higher than about 2N, colloid precipitation will occur during or after melting, and if it is higher still, it will not dissolve.On the other hand, if the concentration is too low, the amount dissolved will be small.More preferably, 0 .5-1.
It is about 5 regulations, especially about 1 regulation.

Although some of this slag is used industrially, the majority of it is currently disposed of in landfills as industrial waste, which is preferable from the perspective of being inexpensive and effective use of R sources. . In addition, it contains abundant silica as the first component, alumina as the second component, and calcium and magnesium as the third component, making it ideal as a material for the silica-based flocculant of the present invention.

However, since this solution contains a large excess of the second component, acid-soluble alumina, and the third component, acid-soluble calcium and magnesium, it may gel within several minutes after melting, depending on the degree of PL+. It is unstable. Therefore, p
The following experiments were conducted by changing the type of H and acid and examining the pH of the acid solution, the concentration of each component, the stability (time until gelation starts), etc. Note that each experiment was conducted at room temperature.

[Experiment] Experiment 1 Preparation of silica-based flocculant (Part 1) Slag powder (1
After measuring acid-dissolved silica (Si), dissolve an appropriate amount of IN in dilute hydrochloric acid and sulfuric acid.
i O2), acid-dissolved alumina, acid-dissolved calcium (Cab), and acid-dissolved magnesium (MgO) concentrations were measured (Samples 1 to 8). Note that since the pH increases as the amount of dissolved slag powder increases, the liquid was filtered to stop melting at a certain pH stage. The results are shown in Table-1.

In Table 1, × in Note 1 indicates that the product cannot be used, △ indicates that it can be used for a short time, and ○ indicates that it can be used. In addition, Note 2 seems to be the result of alumina modification.

Experiment 2 Preparation of silica-based flocculant (Part 2) Next, dissolve the slag at the level of sample 7 of Experiment 1 (IN/HCN melting), and when the pi of the dissolved solution rises above 3.2, IN
/ H2S O4 is added little by little while melting is continued to form a precipitate of calcium sulfate. In this case, the already dissolved CaO precipitates to form Ca 2 SO 4 . Once the pH reaches 3.1 to 3.2 again, the dissolution is stopped and the dissolved solution is extracted together with the precipitate, and then the precipitate (C
aSO4) was separated by filtration to obtain a flocculation liquid. This treatment was designated as Experiment 9, and the results are shown in Table 1.

The above results show that liquids with pl+ of around 3.1 (sample 3 and sample 7) have excellent stability.

Furthermore, the agglomerated solution of Sample 9 was also extremely stable. In Experiment 1, the amounts of dissolved calcium and dissolved magnesium were smaller in the sulfuric acid solution.

This is thought to be due to binding with 804″2 and precipitation.

Table Experiment 3 Gelation rate of dissolved silica Next, to measure the gelation rate of dissolved silica, I
Constant amount of N/H2S O4 and IN/HC/ (100
A certain amount of ffi (6 g) of slag was added to the slag, and the mixture was stirred and melted.

In this case, dissolution was stopped at any pH, and the solution (all precipitates) excluding undissolved residues was taken out into a separate beaker, and its coagulation behavior (gelation of silica) was investigated. The results are shown in Table-2.

As is clear from Table 2, both sulfuric acid and hydrochloric acid have a pH of 3,
The stability near 1 was extremely good. However, if it is manufactured on-site and consumed immediately, the pH should be 2.5.
If it is around 3.5, it is almost usable.

Furthermore, HCI! The reason why the stability of the solution is inferior to that of the H2SO4 solution is probably due to the large amount of dissolved Ca salt.

[Function] The silica-based flocculant of the present invention uses a silica-alumina-calcium solution obtained by melting materials containing acid-soluble silica, acid-soluble alumina, and acid-soluble calcium with a reducing acid or a neutral acid as a product component. It is something to do. Then, the polymerization/gelation phenomenon of monomer silica dissolved in water, the accompanying extraction/coagulation phenomenon, and the A 12 *3 and Ca
*Synergetic effect with the promotion of this phenomenon by factors such as 2, chemical reactions and adsorption phenomena caused by A1+3 and Ca', and adsorption phenomena that occur when other cations and anions contained in water become precipitates. This provides excellent extraction and flocculation effects.

Therefore, the silica-based flocculant of the present invention can contain dissolved substances contained in water, such as cations, anions, and ions.
It efficiently extracts, coagulates, and removes suspended solids such as proteins, fats, surfactants, and algae, as well as suspended solids contained in various emulsions, lime wastewater, cement wastewater, etc.

This silica-based flocculant has a pH of 2.5 to 3.5, especially 3.
．． By keeping the temperature around 1 or lowering the Ca04 degree in the liquid, long-term storage is possible.

An example of use will be explained below.

Usage example 1 Aggregation test of algae-containing water using silica-based flocculating liquid Take sample water 11 (pH = 6.6) in a beaker, add PAC and silica-based flocculant while stirring with a stirrer, and stir for 10 minutes. Table 3 [Usage Example 1] Next, the silica-based flocculants of Sample 3 and Sample 7 were prepared. 30
Transparency was measured for the supernatant water after it had been allowed to stand for several minutes. The results are shown in Table-3.

In use example 1, the transparency was good in all cases, but
The silica-based flocculant had a faster sedimentation rate than PAC, and the compressibility of the precipitate was also good.

In addition, the concentration (111)Ill of each component of the silica-based flocculating liquid
) has 34.6 ppm dissolved silica in sample 3 (Note 1).
, dissolved alumina: 17.0 ppm, dissolved calcium: 11. OrlPM % dissolved magnesium is 3.6 ppm
, Sample 7 (Note 2) has dissolved silica of 36.0ρpHl.
% molten alumina 17.6 ppm, molten calcium 34.0 ppm, molten magnesium 4.6 ppm
This is a fraction of that of PAC.

Usage example 2 Concrete drainage treatment using silica-based flocculant (Part 1: PL + no adjustment) Concrete drainage treatment (pH = 12) in the same manner as usage example 1
．． 3: Raw water) PAC and silica-based flocculant were added to If, and after stirring for 10 minutes, the sedimentation rate and transparency were measured. The results are shown in Table-4.

In this example table, the one with PAC added is A7! It melted and turned into a colloid, and even after 30 minutes, there was no sedimentation, the visibility was almost the same as the raw water, the calcium concentration was high, and there was almost no flocculation effect.

On the other hand, both samples to which Sample 3 and Sample 7 were added produced and settled silica-calcium-alumina-based precipitates, and exhibited extremely good coagulation effects. However, in this example, the concentration (ppm) of each component of the silica-based flocculant was
(Note 1), fused silica is 86.5 ppm, fused alumina is 42, sppm, and dissolved calcium is 27.5 ppm.
pm, dissolved magnesium is 9. oppm, sample 7 (
In Note 2), dissolved silica is 90.0 ppm, dissolved alumina is 44.0 ppm, and dissolved calcium is 85.0 ppm.
, dissolved magnesium is 11.5 ppm, and the total is about the same as PAC. Below, usage examples 3 and 4 have the same concentration.

Table Usage Example 3 Concrete wastewater treatment using silica-based flocculant (Part 2: ρII adjustment) Concrete wastewater (ppm 12.1) was preliminarily treated with 2N/H2S to prevent PAC from becoming a colloid.

4 to adjust the pH to 7.0 to 7.2, and treated in the same manner as in Use Example 2. The results are shown in Table-5.

In the case of this example, the PAC treatment also showed a considerable aggregation effect. However, in order to sufficiently precipitate A/ after the PAC treatment, a large amount of alkali was added to adjust the pH.

At present, pH is used to treat concrete wastewater.
Adjustments are inevitable and are a factor that increases costs. Despite this, it is extremely difficult, as the precipitate is poorly packed, resulting in poor dehydration.

On the other hand, in the case of the product of the present invention, the sedimentation rate was only slightly higher than that of Use Example 2 (91 (no adjustment)).In other words, in the case of the silica-based flocculant of the present invention, the cost It can be said that sufficient aggregation effect is exhibited even without adjusting the pH by applying .

Use Example 4 Aggregation treatment of milk fat and protein in water A 10% milk aqueous solution was treated in the same manner as in Use Example 1 as raw water. The results are shown in Table-6.

In this example, the one containing PAC was unsatisfactory in its flocculating effect on the emulsion. However, although the visibility is much better than that of raw water, cloudiness remains and the coagulation effect is not very good.

Conventionally, wastewater from this type of food industry, other than PAC treatment, has generally been diluted and subjected to biological treatment, or biological treatment and a coagulant are used in combination. However, biological treatment requires large equipment and is difficult to manage, and is not very effective for this type of wastewater, and in any case, a definitive treatment method has been lacking.

On the other hand, the silica-based flocculant of the present invention has a flocculating effect, particularly effective against particles smaller than colloids, than PAC, has a faster sedimentation rate, and produces a silica-calcium-alumina-based precipitate. , showed very good aggregation effect. The use of this silica-based flocculant eliminates the need for biological treatment.

Table 6 [Effects of the Invention] As detailed above, the flocculating liquid of the present invention is obtained by dissolving materials containing acid-soluble silica, acid-soluble alumina, and acid-soluble calcium with a reducing acid or a neutral acid. This is a silica-based flocculating liquid whose main component is a silica-alumina-calcium solution.

Polymerization and gelation of monomer silica can be carried out by removing the stable pH (about 3.1) of monomer silica and making it weakly acidic.
It progresses significantly by utilizing interactions with dissolved salts (calcium ions, aluminum ions, etc.), and is effective in extracting, coagulating, and removing contaminants in water.

On the other hand, this flocculation solution contains a large excess of Ca″″2, AIも3, and Mg.
+2, and each exhibits its effect when the pH of the target water is above neutral or on the alkaline side. In addition, interaction occurs with ions in wastewater, increasing the extraction flocculation effect. For example, when water is present in a high concentration, the dissolved silica is gelled, and contaminants in the water are extracted, coagulated, and removed during polymerization and gelation.

In this way, this flocculating liquid retains multifunctionality and p 1
It can exhibit effects not found in conventional flocculants, such as being less susceptible to the effects of 1, having excellent flocculating effects, and facilitating dehydration of aggregates.

In addition, this flocculation solution can be stored for a long period of time, or
When used, the purpose can be achieved by adjusting the pH of the flocculating solution to about 3.1 and controlling the Ca salt and Mg salt concentrations to about 0°2N or less.

Furthermore, the silica-based flocculant of the present invention can be obtained at low cost, and can be used by simply mixing several to several tens of ppm into wastewater and stirring, resulting in extremely low processing costs.

Therefore, it can be used to treat not only industrial wastewater, but also agricultural wastewater and vast amounts of quasi-natural water (lakes, ponds, etc.), and it is also possible to treat large amounts of water that has traditionally been neglected due to treatment and equipment costs. Therefore, it greatly contributes to preventing pollution of environmental water.

Claims (1)

[Claims] 1. A silica-based agglomerate whose main component is a silica-alumina-calcium solution obtained by dissolving materials containing acid-soluble silica, acid-soluble alumina, and acid-soluble calcium with a reducing acid or a neutral acid. liquid. 2. When dissolving materials containing acid-soluble silica, acid-soluble alumina, and acid-soluble calcium with reduced acid or neutral acid, the pH of the solution is adjusted to 2.5 to 3.0 by increasing or decreasing the amount of the dissolved materials. A method for producing a silica-based agglomerate, characterized in that the silica-based agglomerate is stabilized by adjusting the concentration to about 5 to prevent gelation of dissolved monomer silica. 3. When dissolving materials containing acid-soluble silica, acid-soluble alumina, and acid-soluble calcium with reduced acid or neutral acid, first melt the materials with reduced acid, and then add an appropriate amount of sulfuric acid to the solution. 1. A method for producing a silica-based flocculant, which comprises producing a calcium sulfate precipitate to reduce the amount of dissolved calcium in the solution, thereby preventing gelation of monomer silica.