JP5574745B2 - Calcium phosphate water purification material and method for producing the same - Google Patents

Description

  The present invention relates to a calcium phosphate water purification material for purifying wastewater containing, for example, heavy metals and fluoride ions as impurities, and a method for producing the same.

  Conventionally, in order to remove heavy metals such as lead (Pb), cadmium (Cd), copper (Cu) and iron (Fe) and fluoride ions contained in waste water, calcium phosphate compounds such as hydroxyapatite (HAP) A water purification material containing water is used. Such a calcium phosphate-based water purification material removes harmful substances from wastewater by utilizing ion exchange ability such as HAP.

  As this type of calcium phosphate water purification material, a low crystalline hydroxyapatite powder or granule of Ca / P (molar ratio) = 1.4 to 1.8 is known (for example, Patent Document 1). reference.).

JP 2003-126687 A (pages 3 and 4)

  However, the calcium phosphate-based water purification material as described above is very expensive. If such a calcium phosphate-based water purification material is used, the cost increases.

  This invention is made | formed in view of such a point, and it aims at providing the calcium-phosphate type | system | group water purification material which can be manufactured cheaply, and its manufacturing method.

The calcium phosphate-based water purification material according to claim 1 includes at least one of concrete sludge , sewage, food factory effluent, and surplus water obtained by dewatering sludge generated when the sewage or effluent is treated by the activated sludge method. mixing the phosphorus-containing aqueous solution and is either a principal component and calcium ions and hydroxide ions from said concrete sludge, a calcium phosphate and phosphoric acid ions are crystallized in response derived from said phosphorous-containing aqueous solution To do.

The method for producing a calcium phosphate-based water purification material according to claim 2 includes concrete sludge , sewage, food factory effluent, and surplus water obtained by dewatering sludge generated when the sewage or effluent is treated by the activated sludge method. of a mixture of phosphorus-containing aqueous solution and at least one, such that the ratio of P contained in the Ca and the phosphorus-containing aqueous solution contained in said concrete sludge, is 0.1 to 200 at Ca / P ratio The calcium phosphate and hydroxide ion derived from the concrete sludge are reacted with the phosphate ion derived from the phosphorus-containing aqueous solution to crystallize calcium phosphate.

According to the invention described in claim 1, concrete sludge is used, and calcium ions and hydroxide ions derived from the concrete sludge react with phosphate ions derived from the phosphorus-containing aqueous solution to cause crystallization. Since the main component is calcium phosphate, it can be manufactured at low cost.

According to the invention described in claim 2, since calcium phosphate is crystallized by mixing concrete sludge and a phosphorus-containing aqueous solution, a calcium phosphate-based water purification material can be produced at low cost.

It is a graph which shows transition of Cd concentration after each sample material addition. It is a graph which shows transition of Ca concentration after each sample material addition. It is a graph which shows transition of Cd removal amount after each sample material addition. It is a graph which shows transition of Ca elution amount after each sample material addition. It is a graph which shows transition of Cd removal amount and Ca elution amount after sludge HAP addition. It is a graph which shows transition of Cu concentration after each sample material addition. It is a graph which shows transition of Ca concentration after each sample material addition. It is a graph which shows transition of Cu removal amount after each specimen addition. It is a graph which shows transition of Ca elution amount after each sample material addition. It is a graph which shows transition of Cu removal amount and Ca elution amount after sludge HAP addition. It is a graph which shows transition of each F density | concentration after sludge HAP and cement powder addition. It is a graph which shows transition of each F removal amount after sludge HAP and cement powder addition. It is a graph which shows transition of pH of each solution after sludge HAP and cement powder addition.

  Hereinafter, the configuration of an embodiment of the present invention will be described in detail.

  Calcium phosphate water purification material mixes concrete waste and phosphorus-containing aqueous solution so that calcium ions and hydroxide ions derived from concrete waste react with phosphate ions derived from phosphorus-containing aqueous solution. The main component is hydroxyapatite (HAP) as calcium phosphate crystallized.

Concrete wastes are co down cleat sludge are those that contain a basic calcium compound such as calcium hydroxide derived from cement. Co down cleats sludge, for example, concrete products centrifugal molding, concrete production, those generated in the fresh concrete site of use, such as cleaning and cleaning of concrete transport vehicles concrete production facilities, particle-derived cement particles and aggregate into water Min is the residue of suspended concrete material. When using concrete sludge, it can be used as it is except for excess water.

In addition, since the concrete waste when mixed with the phosphorus-containing aqueous solution is concrete sludge, the aggregate content in the concrete waste is suppressed, and calcium ions and hydroxide ions react with phosphate ions. It becomes easy.

Phosphorus-containing aqueous solution, which contains a phosphate ion, and lower water and food factory wastewater, and these sewage and wastewater treatment with activated sludge process and sludge surplus water generated during the dehydration of the sludge This is sludge return water . In the sludge return water, phosphorus is dissolved as phosphoric acid, the phosphorus concentration is as high as about 50 mgPL- ¹ , and the reaction efficiency with concrete sludge is good.

When concrete sludge and phosphorus-containing aqueous solution are adjusted such that the ratio of Ca contained in concrete sludge and P contained in phosphorus-containing aqueous solution is 0.1 to 200 in terms of Ca / P ratio, It is preferable because hydroxide ions and phosphate ions easily react with each other, and more preferably, the Ca / P ratio is 1.0 or more and 100 or less.

  The calcium phosphate water purification material only needs to contain calcium phosphate crystallized as described above as a main component, and may contain impurities.

  Next, a method for producing the calcium phosphate water purification material will be described.

In preparing the calcium phosphate water purification materials, within the reaction vessel, the concrete sludge and phosphorus-containing aqueous solution was charged and mixed by stirring and concrete sludge and the phosphorus-containing aqueous solution in such a stirrer.

When concrete sludge and a phosphorus-containing aqueous solution are mixed, the cement hydration part in the concrete containing a large amount of a basic calcium compound such as calcium hydroxide is reacted with Ca (OH) ₂ → Ca ²⁺ + 2OH ^{− in} the aqueous solution. It causes a dissolution reaction of calcium hydroxide represented by the formula and acts as calcium ions and hydroxide ions.

That is, by mixing the concrete sludge and the phosphorus-containing aqueous solution, calcium derived from the concrete sludge as shown by the reaction formula of 10Ca ²⁺ + 6PO ₄ ³ + 2OH ⁻ → Ca ₁₀ (PO ₄ ) ₆ (OH) ₂ Ions and hydroxide ions react with phosphate ions derived from the phosphorus-containing aqueous solution to crystallize hydroxyapatite, which is calcium phosphate.

In the above reaction, since insolubles concrete sludge acts as a seed crystal, and phosphate calcium component and a phosphorous-containing aqueous solution of the surface of the insoluble portion of the concrete sludge reacts directly, by using a concrete sludge, hydroxyapatite It is easy to crystallize.

  And this crystallized substance is collect | recovered with collection | recovery means, such as a solid-liquid separator and a centrifuge, for example, and a calcium-phosphate type | system | group water purification material is obtained.

The calcium phosphate water purification material is not limited to a method of stirring and mixing with concrete sludge , a phosphorus-containing aqueous solution, a stirrer, or the like, as long as it can be mixed in a reaction vessel.

  Further, the reaction tank does not need to have a special structure, and a generally used one such as an open type reaction tank can be used.

  Next, the effect of the one embodiment will be described.

Calcium phosphate water purification material is mainly discarded because it contains calcium phosphate crystallized by the reaction of calcium ions and hydroxide ions derived from concrete sludge and phosphate ions derived from a phosphorus-containing aqueous solution. By using concrete sludge , raw material costs can be reduced, and production can be made at a low cost.

In addition, calcium phosphate water purification materials can be manufactured simply by mixing concrete sludge and phosphorus-containing aqueous solution, crystallizing calcium phosphate, and recovering the crystallized material, so there is no need for special equipment or processes. Can be manufactured.

  According to such a calcium phosphate-based water purification material, since calcium phosphate is the main component, just by putting the calcium phosphate-based water purification material into the wastewater to be treated, using the ion exchange ability of the main component calcium phosphate, Heavy metals and fluoride ions can be removed from the wastewater, and the wastewater can be purified.

Here, although the amount of concrete sludge is expected to increase in the future, there are many cases where it is discarded without being effectively used at present, and its treatment is regarded as a problem. Therefore, since concrete sludge can be reused by using concrete sludge for the production of calcium phosphate water purification material, it is possible not only to manufacture calcium phosphate water purification material at low cost by reducing raw material costs, but also to reduce the amount of waste. It is also effective as a countermeasure against problems.

Further, by using concrete sludge, a calcium phosphate-based water purification material can be produced simply by stirring and mixing the concrete sludge and the phosphorus-containing aqueous solution without the need for a step such as pulverization, and can be easily manufactured.

In addition, by using phosphorus-containing wastewater such as sewage and food factory effluent as the phosphorus-containing aqueous solution, calcium phosphate water purification materials can be manufactured only from those that are originally discarded along with the concrete sludge. The quantity can be reduced and it is very effective as a countermeasure for environmental problems.

  Next, examples of the present invention will be described.

  In order to confirm the water purification performance of heavy metals and fluoride ions in calcium phosphate water purification materials, an experiment was conducted to remove heavy metals cadmium (Cd) ions, copper (Cu) ions, and fluoride ions in a batch-type reaction. It was.

  A calcium phosphate water purification material as an example was produced using a sample corresponding to concrete sludge.

  Specifically, 1 g of cement was added to 100 ml of pure water and stirred for 2 hours to obtain a concrete sludge equivalent sample. To this concrete sludge equivalent sample, 100 ml of a phosphorous solution was added, and the phosphoric acid concentration was Ca / P ratio. The mixture was adjusted to 1.67 by mixing with a triangular magnetic stirrer (magnetic stirrer) at 400 rpm and mixed.

  At 1 hour, 4 hours, 24 hours and 72 hours after the start of the reaction, samples of the mixed liquid were collected, and concentration analysis of Ca, Si and P and measurement of pH were performed on each sample, and the crystallized hydroxy The sludge HAP recovered from the apatite and then dried was used as an example of a calcium phosphate water purification material.

Each of the sludge HAP thus produced, a reagent HAP as a comparative example using commercially available HAP, a reagent calcium carbonate (CaCO ₃ ) as a comparative example, and a cement powder as a comparative example And a removal test was conducted to remove heavy metals or fluorides with each test material.

The removal test, a Cd-containing solution as a heavy metal-containing solution Cd concentration of ^{5.0 × 10 -3 mol / l (} 562ppm), Cu concentration is ^{5.0 × 10 -3 mol / l (} 317ppm) heavy metal A Cu-containing solution as the containing solution and an F-containing solution as a fluoride-containing solution having an F concentration of 8.2 × 10 ⁻⁴ mol / l (147 ppm) were used as the solution to be removed.

  While stirring 100 ml of each of these solutions to be removed at 400 rpm with a triangular stirrer, 0.2 g of each test material pulverized to a powder particle size of 150 μm or less was added, and stirring was continued as it was for reaction.

  And the thing using the heavy metal containing solution used a filter (filter diameter 0.20 micrometer) in the reaction time after addition of a test material in 0 minutes, 5 minutes, 10 minutes, 30 minutes, 60 minutes, and 120 minutes. 2 ml samples of each liquid were taken.

  In addition, in the case of using a fluoride-containing solution, each liquid sample was obtained using a filter (filter diameter 0.20 μm) at a reaction time of 0 minutes, 10 minutes, 30 minutes, and 90 minutes after addition of the test material. 3 ml of was collected.

  Each collected sample was subjected to liquid analysis, and the concentration and removal amount of any of Cd, Cu, and F, and the concentration and elution amount of Ca were confirmed.

  Moreover, the solid of each sample was separated into solid and liquid by suction filtration, dried, and analyzed by XRD.

  With respect to the Cd-containing solution that is the solution to be removed, the transition of the Cd concentration after the addition of each test material is shown in FIG. 1, and the transition of the Ca concentration after the addition of each test material is shown in FIG. Also, the transition of the Cd removal amount obtained from the results of FIG. 1 is shown in FIG. 3, and the transition of the Ca removal amount obtained from the results of FIG. 2 is shown in FIG.

  When sludge HAP is used, as shown in FIG. 1, the Cd concentration decreases from about 600 ppm of the initial concentration to about 400 ppm 10 minutes after the start of the reaction, and to 300 ppm 120 minutes after the start of the reaction. Further, as shown in FIG. 3, Cd ions are rapidly removed in about 10 minutes.

From the results of XRD and equilibrium calculation, sludge HAP seems to contain HAP and CaCO ₃ , but when reagent HAP and reagent CaCO ₃ were used, Cd ions were hardly removed. Although it is known that CaCO ₃ does not have much substitution performance, it was because of the difference in crystallinity of HAP that Cd ions could hardly be removed even in the reagent HAP using HAP with known ion exchange ability. it is conceivable that. Reagent HAP measured by XRD showed a very clear peak, suggesting high crystallinity, but the one attached to sludge HAP was very poor in crystallinity. This difference in crystallinity is considered to have made the difference in Cd removal ability remarkable.

  In the case of using cement powder, a unique behavior was observed with respect to the amount of Cd removed. That is, the removal amount when the reaction time was short after the start of the reaction was lower than the sludge HAP, but the removal amount increased with the reaction time, and the removal amount was the same as the sludge HAP after 2 hours from the start of the reaction. However, as shown in FIGS. 2 and 4, the amount of Ca removal when cement powder is used is the largest in 2 hours after the start of the reaction, and it is not preferable that the amount of Ca removal is large as a water purification material. Therefore, it can be seen that it is preferable to use sludge HAP rather than cement powder from the viewpoint of the amount of Ca removal.

FIG. 5 shows changes in Cd removal amount and Ca elution amount when sludge HAP is used. Since the HAP adsorption mechanism is mainly ion exchange, the removal amount of heavy metal ions and the elution amount of Ca ions seemed to be about the same in the sludge HAP ion exchange. As shown in FIG. The amount was about 3 times the Ca elution amount, which was different from the quantitative relationship of ion exchange. This is because, for example, the solubility product of CaCO ₃ is 3.8 × 10 ⁻⁹ , and the solubility product of CdCO ₃ is 5.2 × 10 ^−12. , The possibility that the Cd crystal seeds were precipitated as simple precipitates without the elution of Ca, or ion exchange by changing from a product with a low Ca / P ratio to a product with a high Ca / P ratio. It is possible that Cd ions were taken in Since it is preferable for the water purification material to have a small amount of Ca removal, it is preferable to use sludge HAP because not only the amount of Cd removal is large but also the amount of Ca removal is small.

  As in the case of the Cd-containing solution, for the Cu-containing solution that is the solution to be removed, the transition of the Cu concentration after the addition of each test material is shown in FIG. 6, and the transition of the Ca concentration after the addition of each test material is shown in FIG. 7 shows. Further, FIG. 8 shows the transition of the Cu removal amount obtained from the result of FIG. 6, and FIG. 9 shows the transition of the Ca removal amount obtained from the result of FIG.

  When sludge HAP is used, as shown in FIG. 6, the Cu concentration decreases from about 320 ppm of the initial concentration to about 200 ppm 10 minutes after the start of the reaction, and to about 150 ppm 120 minutes after the start of the reaction. Further, as shown in FIG. 8, Cu ions are rapidly removed in about 10 minutes.

Here, the sludge HAP showed a higher Cu removal action than when the reagent HAP and the reagent CaCO ₃ were used, but the amount of Cu removal by the cement powder was the largest, and when the cement powder was used, the reaction started Cu was completely removed from the Cu-containing solution in 60 minutes.

Although the mechanism by which the cement powder showed such high removal performance with respect to Cu has not been elucidated, since the amount of Ca removal is also extremely high, as a different kind of crystal such as copper hydroxide (Cu (OH) ₂ ) Possible dissolution and re-precipitation.

By removing Cu, no change in the appearance of the reagent HAP and the reagent CaCO ₃ was observed, but the sludge HAP and the cement powder turned green. From this, it is considered that the crystal seed has changed. However, XRD did not show much change in crystal structure. Therefore, it is presumed that the crystal structure has changed only to a part in the solid, or to a crystal species in which the crystal structure hardly changes.

  FIG. 10 shows changes in Cu removal amount and Ca elution amount when sludge HAP is used.

  As in the case of Cd, Cu that is greater than or equal to the Ca elution amount has been removed, but the ratio of the amount is about 1.5 times that of the Cd removal amount and Ca elution amount is about 1/2. It is. This difference is thought to be due to the difference in metal species.

  Here, when the amount of Cd removed by the sludge HAP is compared with the amount of Cu removed, Cu is about 25% more. In the case of Cd, the reaction was almost completed in about 10 minutes after the start of the reaction, whereas it took a little time to remove Cu.

  Similarly to the Cd-containing solution and the Cu-containing solution, FIG. 11 shows changes in F concentration after addition of sludge HAP and cement powder for the F-containing solution that is the solution to be removed. Moreover, transition of each F removal amount after sludge HAP and cement powder addition is shown in FIG.

  As shown in FIG. 11, the F concentration decreased from an initial concentration of about 147 ppm to about 140 ppm in a 90-minute reaction.

The amount of Cd removed by sludge HAP is about 0.20 mmol (1 mmol / g) 120 minutes after the start of the reaction, and the amount of Cu removed by sludge HAP is about 0.26 mmol (1.29 mmol / g) 120 minutes after the start of the reaction. In contrast, as shown in FIG. 12, the amount of F removed by sludge HAP was about 0.08 mmol (0.16 mmol / g) 90 minutes after the start of the reaction, which was slightly less. However, considering the HAP composition of Ca ₅ (PO ₄ ) ₃ OH, the number of OH substituted for F is 1/5 of the number of Ca substituted for heavy metals. Is also good.

  FIG. 13 shows the transition of the pH of the solution when F is removed by sludge HAP and cement powder.

  When sludge HAP was added and F was removed, the pH of the solution remained at about 6 and hardly changed. On the other hand, when F was removed by adding cement powder, the pH of the solution rose to 10 or more.

Claims (2)

And concrete sludge, sewage, food factory wastewater, and, mixing the phosphorus-containing aqueous solution and at least one of excess water dehydrated sludge these sewage and wastewater upon treatment with activated sludge, said concrete sludge calcium ions and hydroxide ions from the calcium phosphate water purification material and phosphate ions, characterized in that the main component was crystallized by reacting calcium phosphate derived from a phosphorus-containing aqueous solution. Mixing concrete sludge with sewage, food factory effluent, and a phosphorus-containing aqueous solution that is at least one of excess water that has been dewatered from sludge generated when the sewage and effluent are treated by the activated sludge method ,
The ratio between Ca contained in the concrete sludge and P contained in the phosphorus-containing aqueous solution is adjusted so that the Ca / P ratio is 0.1 or more and 200 or less, and calcium ions derived from the concrete sludge and A method for producing a calcium phosphate-based water purification material, comprising reacting hydroxide ions with phosphate ions derived from the phosphorus-containing aqueous solution to crystallize calcium phosphate.

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