TWI385125B - Method for reducing silica from water - Google Patents

Description

Method for reducing cerium oxide in water

The present invention relates to a method of water recovery treatment, and more particularly to a method of reducing cerium oxide.

With the booming industry, the demand for water resources has increased significantly, and the establishment of a cost-effective water recycling system is extremely important. At present, most of the most commonly used water recovery treatment systems in the commercial industry are reverse osmosis or electrodialysis. However, when the content of cerium oxide in water is too high, when osmosis is used, cerium oxide tends to form a scale which is difficult to remove on the surface of the film. However, when electrodialysis is used, since cerium oxide has almost no charge at neutral pH, it is also impossible to effectively remove cerium oxide. In order to solve the above problems, it is necessary to have a pretreatment method to effectively reduce the cerium oxide content in water.

Taiwan Patent Publication No. 200604108 proposes a cerium oxide removing device and a cerium oxide removing method, which use a simple device to remove cerium oxide from a reverse osmosis membrane concentrated water to below a saturated concentration, thereby effectively preventing reverse osmosis membrane concentrated water circulation. At the same time as the cerium oxide spalling occurs, the entire amount of raw water can be used as a reverse osmosis membrane to permeate the water.

Taiwan Patent No. 00585843 provides a method and a prevention device for preventing gangue fouling, which removes cerium oxide in water by charging cooling circulating water by filling 1 μm to 10 mm cerium particles.

German Patent DE 3940464 proposes a method for reducing seawater cerium oxide by controlling the amount of alkali agent to a pH of less than 9, thereby forming a precipitate of calcium carbonate and citrate, but not producing a precipitate of magnesium hydroxide.

U.S. Patent 4,276,180 discloses a process for reducing cerium oxide in industrial waste water by selectively removing cerium oxide from activated aluminum.

At present, the methods for removing cerium oxide include a lime softening method, an anion exchange resin method, a ruthenium adsorption method, etc. However, the above methods have limitations in application and cannot be adopted by the industry. Therefore, there is an urgent need in the industry to develop a method for effectively reducing cerium oxide in water.

The invention provides a method for reducing cerium oxide in water, comprising the steps of: introducing raw water containing cerium oxide, magnesium ion and calcium ion into a fluidized bed reaction tank containing a support; adding an alkaline solution to the fluid In the fluidized bed reaction tank, the pH value in the fluidized bed reaction tank is about 11-13, wherein a salt crystal is formed on the support; and the effluent water of the fluidized bed reaction tank is introduced into a subsequent treatment system. .

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The present invention provides a method for reducing cerium oxide in water, comprising the following steps. Referring to FIG. 1, a raw water 12 containing cerium oxide, magnesium ions and calcium ions is introduced into a fluidized bed reaction tank 106 containing a support 16. The raw water system is derived from cooling circulating water, and the concentration of cerium oxide in the raw water is about 10 mg/L, and the molar ratio of magnesium ion to cerium oxide is 1, the molar ratio of calcium ions to cerium oxide 0.67. The carrier 16 of the fluidized bed reaction tank 106 comprises quartz sand, brick powder, activated carbon or a combination thereof, and has a particle size of about 0.1 to 1 mm, preferably a range of about 0.2 to 0.5 mm, which serves to provide a carrier. Position, allowing subsequent salts to form crystals here.

Then, an alkaline solution 14 is added to an alkali solution tank 104, an alkaline solution such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution, and the alkaline solution 14 is introduced into the fluidized bed reaction tank 106. The fluidized bed reaction tank 106 has a pH of about 11 to 13, preferably a pH of 12. Since the solubility of cerium oxide in water is related to the pH value, the higher the pH value, the greater the solubility, while at neutral, the solubility of cerium oxide is the lowest. Therefore, the present invention controls the fluidized bed reaction tank 106. The pH value causes the cerium oxide to ionize under the condition of pH 11~13, and then reacts with magnesium ions and calcium ions in the water to form salt crystals on the support. The salt crystals include magnesium silicate (MgSiO ₃ ). Calcium citrate (Na ₂ Ca ₂ Si ₃ O ₉ ), magnesium hydroxide (Mg(OH) ₂ ), calcium carbonate (CaCO ₃ ) or a combination thereof. The reaction in the above support can be carried out at room temperature, and the temperature can be about 20 to 35 ° C, but not limited thereto, because the higher the temperature, the better the ionization of cerium oxide. In addition, the order of adding the raw water 12 and the alkaline solution 14 is not limited thereto. The person skilled in the art can appropriately adjust the order of addition according to the needs of the actual application, for example, adding the raw water 12 and the alkaline solution 14 at the same time. Alternatively, the alkaline solution 14 is added first and the raw water 12 is added.

The invention can effectively reduce the content of calcium ions and magnesium ions in water by reacting ceria with calcium ions and magnesium ions while reducing the content of ceria in water.

Thereafter, the effluent water 18 of the fluidized bed reaction tank 106 is introduced into a subsequent processing system (not shown), such as electrodialysis (ED), Electrodialysis reversal (EDR) or reverse osmosis (RO). By the method of the invention, the content of cerium oxide in water can be effectively reduced, and the removal rate of cerium oxide is more than about 50%.

When the amount of crystal formed on the surface of the support is gradually increased, the larger the crystal grain size, the larger the crystal grain size near the reaction tank is. In order to maintain fluidization and provide sufficient crystal surface area, the particles below the reaction tank are periodically larger. The salt crystals of the diameter are discharged, and then some new support is added to the fluidized bed reaction tank to maintain the treatment efficiency of the cerium oxide.

In another embodiment of the present invention, referring to Fig. 2, raw water 22 containing cerium oxide, magnesium ions and calcium ions is introduced into a fluidized bed reaction tank 208 containing a support 28, wherein the raw water system is derived from a cooling cycle. The concentration of the cerium oxide in the raw water is more than about 10 mg/L, and the type and effect of the carrier 28 of the fluidized bed reaction tank 208 are the same as those in the first embodiment, and will not be described herein.

Then, an alkaline solution 24 and a carbonate-containing solution 26 are separately added to an alkali solution tank 204 and a carbonate solution tank 206, and an alkaline solution such as sodium hydroxide (NaOH) or potassium hydroxide (KOH) solution is added. And a solution of carbonate such as sodium carbonate solution or sodium hydrogencarbonate solution. The two solutions 24, 26 are then introduced into the fluidized bed reaction tank 208 such that the fluidized bed reaction tank 208 has a pH of about 11 to 13, preferably a pH of 12. The purpose of adding carbonate solution 26 is to increase the carbonate concentration in the water. When the concentration of carbonate is increased, it can effectively help the precipitation of calcium carbonate, so that the concentration of calcium ions in the water can be effectively reduced while reducing the cerium oxide in water. It should be noted here that the first embodiment mainly increases the pH by increasing the concentration of hydroxide (OH ^- ) ions, and the purpose of adding the carbonate solution in this embodiment is mainly to increase the concentration of carbonate ions, Helps the formation of calcium carbonate crystals. In addition, the order of adding the raw water 12 and the alkaline solution 14 is not limited thereto. The person skilled in the art can appropriately adjust the order of addition according to the needs of the actual application, for example, adding the raw water 12 and the alkaline solution 14 at the same time. Alternatively, the alkaline solution 14 is added first and the raw water 12 is added.

Thereafter, the effluent water 30 of the fluidized bed reaction tank 208 is introduced into a subsequent processing system (not shown), such as electrodialysis (ED), electrodialysis reversal (EDR), or reverse osmosis (reverse). Osmosis, RO). By the method of the invention, the content of cerium oxide in water can be effectively reduced, and the removal rate of cerium oxide is more than about 50%.

The embodiment of the present invention can be applied to waste water containing both cerium oxide, calcium ion and magnesium ion in water, for example, applied to cooling cycle water recycling, wastewater treatment or process drainage treatment. Furthermore, the present invention controls the pH of the fluidized bed reaction tank to ionize the cerium oxide at a pH of about 11 to 13, thereby forming various salt crystals, which not only effectively reduces water oxidation in water. The content of strontium can also achieve the effect of reducing calcium ions and magnesium ions.

[Examples] [Example 1] Manually prepared wastewater

The experimental apparatus used a transparent glass column with a diameter of 2 cm and a height of 120 cm, and was filled with a carrier of 85 cm of high-density 0.1-0.3 mm quartz sand (SiO ₂ ). Using calcium chloride, magnesium chloride, sodium citrate and sodium bicarbonate to prepare a solution containing calcium, magnesium and strontium to simulate the cooling water raw water, introduced from below the reaction tank, and simultaneously injecting sodium hydroxide to increase its pH value, and S1- Sodium bicarbonate was added to S7. The array experiment results (S1~S9) are shown in Table 1. When the pH of the reaction tank needs to be above 11 (such as S4, S5, S8, S9), calcium, barium and magnesium will have obvious treatment effects. Comparing the results of S4, S5 and S8, S9 (without adding sodium bicarbonate), it is known that the alkalinity affects the calcium ion removal rate, and the higher the non-hydrogen oxygenation degree, the higher the calcium ion removal rate.

[Example 2] Factory cooling water

The experimental apparatus used a transparent glass column with a diameter of 2 cm and a height of 120 cm, and was filled with a carrier of 85 cm of high-density 0.1-0.3 mm quartz sand. The cooling water of the cooling tower of the factory is introduced from below the reaction tank, and the liquid alkali is simultaneously injected to increase the pH value. The array experiment results (S10~S13) are shown in Table 2. The S10 experiment has obvious removal effect on cerium oxide, magnesium ion and calcium ion, and the cesium ion removal rate is 88%. Since the carbonate concentration in this cooling cycle water is low, the calcium ion removal rate is also low. Above pH 11, the removal rate of strontium ions and magnesium ions can reach more than 70%.

While the invention has been described above in terms of several preferred embodiments, it is not intended to limit the scope of the present invention, and any one of ordinary skill in the art can make any changes without departing from the spirit and scope of the invention. And the retouching, so the scope of protection of the present invention is defined by the scope of the patent application attached The standard is subject to change.

12‧‧‧ raw water

14‧‧‧Liquid

16‧‧‧Support

18‧‧‧Outflow of water

22‧‧‧ raw water

24‧‧‧Liquid

26‧‧‧ carbonate-containing solution

28‧‧‧Support

30‧‧‧Outflow of water

102‧‧‧ original sink

104‧‧‧ lye tank

106‧‧‧ Fluidized bed reactor

202‧‧‧ original sink

204‧‧‧ lye tank

206‧‧‧ carbonate-containing liquid tank

208‧‧‧ Fluidized bed reactor

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view showing an embodiment of the present invention for reducing cerium oxide in water.

Figure 2 is a schematic view of another embodiment for explaining the method of reducing cerium oxide in water of the present invention.

12‧‧‧ raw water

14‧‧‧Liquid

16‧‧‧Support

18‧‧‧Outflow of water

102‧‧‧ original sink

104‧‧‧ lye tank

106‧‧‧ Fluidized bed reactor

Claims (12)

A method for reducing cerium oxide in water comprises the steps of: introducing raw water containing cerium oxide, magnesium ions and calcium ions into a fluidized bed reaction tank containing a support, wherein the carrier of the fluidized bed reaction tank comprises Quartz sand, brick powder, activated carbon or a combination thereof; adding an alkaline solution to the fluid bed reaction tank, so that the pH in the fluidized bed reaction tank is about 11-13, wherein the support forms a Salt crystallization; and the effluent from the fluidized bed reactor is directed to a subsequent processing system. The method for reducing cerium oxide in water according to claim 1, wherein the salt crystal comprises magnesium ruthenate, calcium citrate, magnesium hydroxide, calcium carbonate or a combination thereof. The method for reducing cerium oxide in water according to claim 1, wherein the fluidized bed reaction tank has a particle size of about 0.1 to 1 mm. The method for reducing cerium oxide in water according to claim 1, wherein the temperature in the fluidized bed reaction tank is about 20 to 35 °C. The method for reducing cerium oxide in water according to claim 1, wherein the subsequent processing system comprises electrodialysis (ED), electrodialysis reversal (EDR) or reverse osmosis (reverse osmosis). RO). The method for reducing cerium oxide in water according to claim 1, wherein the alkaline solution comprises a sodium hydroxide solution or a potassium hydroxide solution. Reducing cerium oxide in water as described in claim 1 The method further comprises discharging the salt crystals, and supplementing the support into the fluidized bed reaction tank. The method for reducing cerium oxide in water according to claim 1, wherein the method further comprises: introducing a carbonate-containing solution into the fluidized bed reaction tank. The method for reducing cerium oxide in water according to claim 8, wherein the carbonate-containing solution comprises a sodium carbonate solution or a sodium hydrogencarbonate solution. A method for reducing cerium oxide in water as described in claim 1, wherein the raw water has a cerium oxide concentration of greater than about 10 mg/L. The method for reducing cerium oxide in water according to claim 1, wherein the cerium dioxide removal rate of the effluent water is greater than about 50%. The method for reducing cerium oxide in water according to claim 1, wherein the raw water system is derived from cooling circulating water.