TW201940230A - Method for treating fluoride-containing activated alumina - Google Patents

Abstract

A method for treating a fluoride-containing activated alumina is described and includes steps of: providing the fluoride-containing activated alumina; and performing an desorption step on the fluoride-containing activated alumina by at least a fluoride desorbent for 1 to 3 hours, such that the fluoride-containing activated alumina forms a regenerated activated alumina, wherein a volume ratio of the fluoride desorbent and the fluoride-containing activated alumina ranges from 1 to 3, and the fluoride desorbent is selected from a group consisting of sodium hydroxide and ferrous sulfate.

Description

Processing method of fluorine-containing activated alumina

The present invention relates to a method for treating alumina, and more particularly to a method for treating fluorine-containing activated alumina.

Low doses of fluoride can help prevent dental caries, but high doses of fluoride can cause dental or bone damage. The US Environmental Protection Agency requires that the fluoride in drinking water should not exceed 4 mg / L. For the Republic of China, the maximum limit for fluoride salts in drinking water quality standards is 0.8 mg / L, while the maximum limit for fluoride salts is 15 mg / L in the Drainage Water Law.

For ordinary steel mills, the fluorine-containing wastewater discharged from steel mills can usually utilize activated alumina to adsorb fluorine components. However, there is currently no research indicating the specific method for regenerating the activated alumina to reuse the activated alumina.

Therefore, it is necessary to provide a treatment method for fluorine-containing activated alumina to solve the problems existing in conventional technology.

An object of the present invention is to provide a method for treating fluorine-containing activated alumina, which uses a specific type of fluorine desorbent to perform a desorption step to obtain regenerated activated alumina, which can reduce the cost of treating fluorine-containing wastewater.

Another object of the present invention is that the used fluorine desorbent (such as sodium hydroxide) can be applied to metal-containing wastewater, which can be used as an acid-base regulator in the softening step.

In order to achieve the above object, the present invention provides a method for treating fluorine-containing activated alumina, which comprises the steps of: providing a fluorine-containing activated alumina; and at least A fluorine desorbent performs a desorption step on the fluorine-containing active alumina for 1 to 3 hours, so that the fluorine-containing active alumina forms a regenerated active alumina, wherein the fluorine desorbent and the fluorine-containing active oxide are oxidized. A volume ratio of aluminum is between 1 and 3, and the fluorine adsorbent is selected from a group consisting of sodium hydroxide and ferrous sulfate.

In an embodiment of the present invention, in the step of providing the fluorine-containing activated alumina, the method further includes a step of adsorbing fluorine components in a wastewater with an activated alumina to form the fluorine-containing activated alumina.

In one embodiment of the present invention, the fluorine desorbent is sodium hydroxide.

In an embodiment of the present invention, after performing the desorption step, the method further includes a step of adding sodium hydroxide after performing the desorption step to a metal-containing wastewater to adjust an acid-base of the metal-containing wastewater. The value is between 9 and 11, wherein the metal-containing wastewater contains at least one metal ion, the metal ion is selected from the group consisting of calcium ion, magnesium ion, iron ion and manganese ion; and The metal-containing wastewater after the pH value is subjected to a softening step to soften the metal-containing wastewater.

In one embodiment of the present invention, the softening step is performed through a fluidized bed or a reaction tank.

In one embodiment of the present invention, the softening step is performed through the fluidized bed, and the fluidized bed includes a quartz sand having an average particle size between 0.5 and 1 mm.

In one embodiment of the present invention, after the acid-base value is adjusted, an ascending flow rate of the metal-containing wastewater in the fluidized bed is between 50 and 150 meters / hour.

In one embodiment of the present invention, the softening step further includes adding calcium chloride to the fluidized bed or the reaction tank.

In one embodiment of the present invention, a concentration of the fluorine desorbent is between 0.5 and 2.0% by weight.

In an embodiment of the present invention, after performing the desorption step, the method further includes: performing a cleaning step on the regenerated activated alumina with a liquid water, wherein a volume ratio of the liquid water to the regenerated activated alumina is a It is between 1 and 3, and an acid-base value of the liquid water is adjusted to be equal to or less than 7.5 through an acid solution.

10‧‧‧Method

11‧‧‧ steps

12‧‧‧ steps

FIG. 1 is a schematic flow chart of a method for treating fluorine-containing activated alumina according to an embodiment of the present invention.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, the following describes the preferred embodiments of the present invention and the accompanying drawings in detail, as follows.

Referring to FIG. 1, a method 10 for treating fluorine-containing activated alumina according to an embodiment of the present invention mainly includes the following steps 11 and 12: providing a fluorine-containing activated alumina (step 11); and desorbing with at least one fluorine The agent performs a desorption step on the fluorine-containing activated alumina for 1 to 3 hours, so that the fluorine-containing activated alumina forms a regenerated activated alumina, wherein the fluorine desorption agent and the fluorine-containing activated alumina have a volume. The ratio is between 1 and 3, and the fluorine adsorbent is selected from the group consisting of sodium hydroxide and ferrous sulfate (step 12). The present invention will use the following to describe the implementation details and principles of the above steps of the embodiment one by one in detail.

A method 10 for treating a fluorine-containing activated alumina according to an embodiment of the present invention is firstly step 11: providing a fluorine-containing activated alumina. In this step 11, the fluorine-containing activated alumina is, for example, adsorbing fluorine components in a wastewater with an activated alumina to form the fluorine-containing activated alumina. In more detail, granular (1 ~ 10mm) activated alumina can be filled in the adsorption tower first, and then a fluorine-containing wastewater whose pH value is adjusted to 8 or less can be provided. The fluorine-containing wastewater can be first subjected to sand filtration or After pretreatment of a filtering device such as fiber filtration, it flows through the packed tower again to remove or reduce the fluorine content in the fluorine-containing wastewater through the adsorption of fluorine by activated alumina. In one embodiment, the fluoride ion concentration in the wastewater flowing out of the packed tower can be controlled by changing the filtration speed of the wastewater in the packed tower. In a specific example, the lower the filtration speed, the lower the fluoride ion concentration in the wastewater flowing out of the packed tower.

A method 10 for treating a fluorine-containing activated alumina according to an embodiment of the present invention is followed by step 12: performing a desorption of the fluorine-containing activated alumina with at least one fluorine desorbent. The step is from 1 to 3 hours, so that the fluorine-containing activated alumina forms a regenerating activated alumina, wherein a volume ratio of the fluorine desorbent to the fluorine-containing activated alumina is between 1 and 3, and the The fluorine adsorbent is selected from the group consisting of sodium hydroxide and ferrous sulfate. In this step 12, an excellent activated alumina regeneration effect is mainly produced through a specific material and a specific ratio of a fluorine desorbent. Specifically, for example, when the regenerated activated alumina is used as the raw material for step 11 (that is, the regenerated activated alumina is filled into an adsorption tower to adsorb the fluorine component of the fluorine-containing wastewater to form a fluorine-containing activated alumina again), This fluorine-containing activated alumina undergoes the process of step 12 to form regenerated activated alumina again. The regenerated activated alumina has substantially the same fluorine adsorption ability as the original activated alumina (that is, the activated alumina used for the first time). . In one embodiment, a concentration of the fluorine desorbent is between 0.5 and 2.0 wt%.

It is worth mentioning that if the fluorine desorbent is sodium hydroxide, it has another characteristic. In one embodiment, when the fluorine desorbent is sodium hydroxide, the sodium hydroxide after the desorption step can be added to a metal-containing wastewater to adjust a pH value of the metal-containing wastewater. Between 9 and 11, wherein the metal-containing wastewater contains at least one metal ion, the metal ion is selected from a group consisting of calcium ion, magnesium ion, iron ion and manganese ion; and the pH value is adjusted. The subsequent metal-containing wastewater undergoes a softening step to soften the metal-containing wastewater. Specifically, for the case where the metal-containing waste water contains calcium and / or magnesium ions, the trace will be contained sodium bicarbonate in water (HCO ₃ ^-) and calcium ions (magnesium ions) to form calcium carbonate ( magnesium carbonate) (i.e., a chemical reaction ^{is: Ca 2+ (Mg 2+) +} HCO 3 - the hydroxide _{^{+ NaOH → Na + + CaCO 3}} (MgCO 3) + H 2 O), the desorption step is carried out Fluoride ions in sodium can also react with calcium ions to form calcium fluoride (CaF ₂ ), so the purpose of reducing calcium ions and magnesium ions (to soften wastewater) and fluoride ions can be removed. On the other hand, for the case where the metal-containing wastewater contains iron ions and / or manganese ions, when the metal-containing wastewater passes through sodium hydroxide to increase the pH value to above 9.0 (for example, between 9 and 11), such as Ferrous ions (Fe ²⁺ ) and manganese ions (Mn ²⁺ ) can be rapidly oxidized by oxygen dissolved in water to form Fe (OH) ₃ and MnO ₂ , so it can achieve the removal or reduction of ferrous ions and manganese ions. purpose.

In one embodiment, the softening step is performed through a fluidized bed. Yes, wherein the fluidized bed comprises a quartz sand having an average particle size between 0.5 and 1 mm. In a specific example, after adjusting the pH value, the metal-containing wastewater flows through the fluidized bed from bottom to top, for example, an ascending flow rate in the fluidized bed is between 50 and 150 meters / hour, thereby Soften the metal-containing wastewater.

In one embodiment, the softening step may be performed through a reaction cell. In a specific example, the metal-containing wastewater after adjusting the pH value is set in the reaction tank, and the metal-containing wastewater can be uniformly softened by stirring or the like. In another embodiment, when fluoride ions will react with calcium-containing wastewater to form calcium fluoride, if the fluoride ion concentration in the effluent wastewater is too high due to insufficient calcium concentration, calcium chloride may be added to the reaction tank. Increase the calcium salt concentration to avoid excessive fluoride ion concentration. It is worth mentioning that calcium chloride can also be added to the above-mentioned fluidized bed to increase the concentration of calcium salt to avoid excessive fluoride ion concentration.

In one embodiment, after performing the adsorption step, the method further includes: performing a cleaning step on the regenerated activated alumina with a liquid water, wherein a volume ratio of the liquid water to the reactivated activated alumina is between 1 and 1. 3, and adjusting an acid-base value of the liquid water to 7.5 or less through an acid solution. The cleaning step is mainly cleaning and removing the fluorine desorbent in the regenerated activated alumina. In a specific example, the pH value of liquid water (such as tap water) can be adjusted through sulfuric acid or hydrochloric acid, so that the pH value can be stably maintained at 7.5 or less after 0.5 hour of washing.

Several examples will be given below to demonstrate that the treatment method of the fluorine-containing activated alumina of the present invention can indeed make the regenerated activated alumina have substantially the same fluorine as the original activated alumina (that is, the activated alumina used for the first time). Adsorption capacity of ingredients.

Example 1

Example 1 is wastewater produced by a factory. After testing, it was found to have about 100 mg / L of fluoride ions, COD of about 2,500 mg / L, and sulfate ion of about 170 mg / L. Provide 40 mL of wastewater with a pH value of 7.0. Add 0.4 g of granular activated alumina (average particle size is about 2 to 3 mm) to the batch to perform a batch adsorption test. After 24 hours, carry out the residual fluorine in the aqueous solution. Salt analysis to calculate active oxidation The adsorption amount of aluminum can be obtained about 3.40 mg / g of the original activated alumina to the fluoride salt.

Then, according to the regeneration conditions in Table 1 (a total of 10 groups of conditions), a desorption step was performed using a fluorine desorbent of 0 to 2 wt% sodium hydroxide and / or 0 to 2 wt% of ferrous sulfate, in which the fluorine adsorbent / activity The volume ratio of alumina is about 2. The regenerated activated alumina is then washed with tap water. When the volume ratio of tap water / activated alumina is about 2, the pH value of the tap water is adjusted with sulfuric acid or hydrochloric acid, so that the pH value can be stably maintained at 7.5 or less after 0.5 hours. Take experimental condition 1 as an example, that is, use a fluorine desorbent / active alumina volume ratio = 2, soak with 0.5% sodium hydroxide for 0.5 hours, drain the sodium hydroxide, and soak with 0.5% ferrous sulfate for 0.5 hours. After that, the ferrous sulfate is evacuated and washed with tap water. The tap water / activated alumina volume ratio = 2, and the pH value of the tap water is adjusted with sulfuric acid or hydrochloric acid, so that the pH can be stably maintained at 7.5 or less after 0.5 hours.

After the reactivated activated alumina, the original activated alumina was tested for fluoride salt adsorption, that is, 40 mL of wastewater with a pH value of 7.0 was provided, and 0.4 g of the reactivated activated alumina was added to the wastewater for batch processing. In the adsorption test, the residual fluoride salt analysis of the aqueous solution was performed after 24 hours to calculate the adsorption amount of activated alumina, as shown in Table 1 above.

It can be known from Table 1 that the adsorption amount of the activated alumina to the fluoride salt is almost close to the adsorption amount of the original activated alumina to the fluoride salt, and some operating conditions can even increase the adsorption amount. It can be seen that the method for treating fluorine-containing activated alumina in the embodiments of the present invention does have the effect of forming regenerated activated alumina.

Example 2

The wastewater from a plant was tested and found to have about 100 mg / L of fluoride ions, COD of about 2,500 mg / L, and sulfate ion of about 170 mg / L. Provide 40 mL of wastewater with a pH value of 7.0. Add 0.4 g of granular activated alumina (average particle size is about 2 to 3 mm) to the batch to perform a batch adsorption test. After 24 hours, carry out the residual fluorine in the aqueous solution. Salt analysis, in order to calculate the adsorption amount of activated alumina, it can be obtained that the adsorption amount of fluoride salt of the original activated alumina is about 3.40 mg / g.

Next, the desorption step is performed using 0.5 wt% sodium hydroxide and 0.5 wt% ferrous sulfate, wherein the volume ratio of the fluorine desorbent (the total of sodium hydroxide and ferrous sulfate) / activated alumina is about 2. After that, the ferrous sulfate is evacuated and washed with tap water. The tap water / activated alumina volume ratio = 2, and the pH value of the tap water is adjusted with sulfuric acid or hydrochloric acid, so that it can still maintain a stable pH of 7.5 or less after 0.5 hours to obtain Regenerated activated alumina. After the reactivated activated alumina, the original activated alumina was tested for fluoride salt adsorption, that is, 40 mL of wastewater with a pH value of 7.0 was provided, and 0.4 g of regenerated activated alumina was added to the wastewater to perform a batch adsorption test. An analysis of the residual fluoride salt of the aqueous solution was performed after 24 hours to calculate the adsorption amount of activated alumina. The obtained result is the adsorption amount of activated alumina to the fluoride salt after the first regeneration. After the activated alumina is regenerated once, the adsorption amount of the activated alumina to the fluoride salt obtained by repeating the above steps of regeneration and adsorption is called the adsorption amount of the activated alumina to the fluoride salt after the second regeneration. The inventor of the present case repeatedly performed the regeneration process, and analyzed the adsorption capacity of the regenerated activated alumina to the fluoride salt. The measured adsorption capacities were all between 2.8 and 3.7 mg / g. It can be seen that the method for treating fluorine-containing activated alumina according to the embodiment of the present invention has at least another advantage, that is, the fluorine-containing activated alumina can be regenerated multiple times without substantially changing the adsorption capacity of the original activated alumina.

Example 3

Example 3 collects the sodium hydroxide waste liquid of Example 2 as a pH-adjusting agent for metal-containing wastewater having calcium / magnesium / iron / manganese. The composition of the metal-containing wastewater with calcium / magnesium / iron / manganese is shown in Table 2 below, which is a plant wastewater. After that, the metal-containing wastewater was injected into a fluidized bed using quartz sand (average particle size between 0.5 and 1.0 mm) as a medium, and the waste liquid of sodium hydroxide generated in Example 2 was used to adjust the fluidized bed. The metal-containing wastewater has a pH value between 10 and 11, and the rising velocity of the metal-containing wastewater in the fluidized bed is about 80 m / h. Please refer to Table 3 below for the water quality test of the waste water outlet.

It can be known from the above tables 2 and 3 that after the softening step, the proportion of calcium ions, magnesium ions, ferrous ions, and manganese ions in the metal-containing wastewater can be reduced, and the fluoride ion concentration in the sodium hydroxide waste liquid can also be reduced. reduce.

In summary, the present invention proposes a method for treating fluorine-containing activated alumina, which does have the ability to obtain regenerated activated alumina, which can reduce the cost of treating fluorine-containing wastewater, reduce the generation of a large amount of sludge, and remove fluorine from wastewater. Ion to less than 10 mg / L to meet wastewater discharge standards. In addition, the sodium hydroxide waste liquid used in the embodiments of the present invention can also be applied to metal-containing wastewater, which can be used as an acid-base regulator in the softening step.

Although the present invention has been disclosed in a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. The scope of protection shall be determined by the scope of the attached patent application.

Claims (10)

A method for treating fluorine-containing activated alumina, comprising the steps of: providing a fluorine-containing activated alumina; and performing a desorption step on the fluorine-containing activated alumina with at least one fluorine desorbent for 1 to 3 hours, so that The fluorine-containing activated alumina forms a regenerated activated alumina, wherein a volume ratio of the fluorine desorbent to the fluorine-containing activated alumina is between 1 and 3, and the fluorine desorbent is selected from the group consisting of A group of sodium hydroxide and ferrous sulfate. The method for treating fluorine-containing activated alumina according to item 1 of the scope of patent application, wherein in the step of providing the fluorine-containing activated alumina, the method further includes the step of: adsorbing a fluorine component in a wastewater with an activated alumina, and This fluorine-containing activated alumina is formed. The method for treating fluorine-containing activated alumina according to item 1 of the scope of the patent application, wherein the fluorine desorbent is sodium hydroxide. According to the method for treating fluorine-containing activated alumina described in item 3 of the scope of patent application, after performing the desorption step, the method further includes the step of adding sodium hydroxide after performing the desorption step to a metal-containing wastewater, To adjust the acid-base value of the metal-containing wastewater to be between 9 and 11, wherein the metal-containing wastewater contains at least one metal ion, the metal ion is selected from the group consisting of calcium ion, magnesium ion, iron ion and manganese ion. A group of groups formed; and performing a softening step on the metal-containing wastewater after adjusting the pH value to soften the metal-containing wastewater. Treatment method of fluorine-containing activated alumina as described in item 4 of the scope of patent application Method, wherein the softening step is performed through a fluidized bed or a reaction cell. The method for treating fluorine-containing activated alumina according to item 5 of the scope of the patent application, wherein the softening step is performed through the fluidized bed, and the fluidized bed includes an average particle size between 0.5 and 1 mm. Quartz sand. The treatment method for fluorine-containing activated alumina according to item 6 of the scope of patent application, wherein an ascending flow rate of the metal-containing wastewater in the fluidized bed after adjusting the pH value is between 50 and 150 meters / hour. The method for treating fluorine-containing activated alumina according to item 5 of the application, wherein the softening step further comprises adding calcium chloride to the fluidized bed or the reaction tank. The method for treating fluorine-containing activated alumina according to item 1 of the scope of the patent application, wherein a concentration of the fluorine desorbent is between 0.5 and 2.0% by weight. The method for treating fluorine-containing activated alumina according to item 1 of the patent application scope, wherein after performing the desorption step, the method further includes: performing a cleaning step on the regenerated activated alumina with a liquid water, wherein the liquid water A volume ratio with the regenerated activated alumina is between 1 and 3, and an acid-base value of the liquid water is adjusted to be equal to or less than 7.5 through an acid solution.