JPS5815190B2 - 100% of the population - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a treatment method for recovering heavy metal ions from heavy metal-containing wastewater, such as plating wastewater.

Heavy metal ions are extremely harmful to the human body, and it is prohibited to discharge untreated industrial wastewater such as plating wastewater into rivers, oceans, etc.

Adsorption methods, precipitation methods, ion exchange methods, and the like are known as methods for removing heavy metals such as cadmium, nickel, chromium, zinc, and lead, but the ion exchange method is known as the simplest method.

However, in the ion exchange method, recycling and reusing the ion exchange resin is a general-purpose prerequisite, and unless it is efficient as a regeneration method, it cannot be used industrially.

The blow sheet shown in Figure 1 shows an example of the simplest method considered when removing heavy metal ions using an ion exchange resin tower.The heavy metal-containing wastewater led from the heavy metal-containing wastewater storage section 1 is weakly acidic. The heavy metals are passed through a cation exchange resin column 8 (hereinafter referred to as WAC), but since the heavy metals usually exist as salts such as sulfates and hydrochlorides, when heavy metal ions are expressed as Me+F, for example, R-Na+MeSO4→R-Me+Na2SO4 (1)
Heavy metal ions are adsorbed according to the reaction formula shown by +MeSO4 on R-→2SO4 on R-Me+ (2),
The treated water from which heavy metal ions have been removed enters the treated water recovery section 2.

On the other hand, hydrochloric acid is induced as a regenerating liquid from the regenerating liquid storage section 3 and is passed through the WAC 8 to form R-Me HC1→R-H+M.
The ion exchange resin is regenerated according to the reaction formula shown in eCt2 (3), and the heavy metal ions are converted to MeC12.
The metal ions enter the heavy metal ion recovery section 5 as ions.

However, in this method, the treated water in the treated water recovery section 2 is
Since alkalis such as SO4 and Na2SO4 are mixed into the water, it has the disadvantage that it cannot be used as is as recovered water.

Therefore, a method as shown in FIG. 2 can be considered, which is a direct connection of the method shown in FIG. 1 with a known pure water production method.

Therefore, the wastewater containing heavy metals is WAC8 as in the case of Figure 1.
For example, heavy metal ions are adsorbed according to the same reaction format as the reaction formula (1) or (2).

The treated water from which heavy metal ions have been removed does not immediately enter the treated water storage section, but is passed through the strongly acidic cation exchange resin tower 9 (hereinafter referred to as SAC), where it removes the alkali metal ions derived from WAC8 that are mixed in the treated water. Sodium ions and potassium ions are removed.

The reaction formula in this case can be expressed as R
-H-+Na2SO4→R-Na+H2SO4(5)R
-H+ to 2SO4→R- to +H2SO4 (6) Therefore 5
In AC9, sulfuric acid is produced and cannot be used as pure water as it is, so the treated water from which alkali metal ions have been removed is further passed through a strong basic anion exchange resin column 10 (hereinafter referred to as SBA), where R-OH+HSo→R -80, state 20
The acid radicals are removed according to the reaction formula shown in (7), and the obtained pure water enters the treated water storage section 2.

On the other hand, since it is necessary to regenerate these ion exchange resin towers, regeneration liquid storage sections 3 and 4 are provided. Hydrochloric acid is stored in the regeneration liquid storage section 3, and caustic soda is stored in the regeneration liquid storage section 4. It is stored.

First, hydrochloric acid for regeneration enters 5AC9 and reacts with the resin that has been converted to R-Na or R-K by the reaction formula (5) or (6) as shown below, resulting in R-Na + HC1 → R-H + NaC1 (8 ) SiC2 is returned to its original H form.

The regenerated hydrochloric acid that has passed through 5AC9 is further passed through WAC8.

According to reaction formula (1) or (2), WAC8 resin is
Although it is converted to the R-Me type, it reacts with hydrochloric acid for regeneration as shown below, resulting in R-Me+HCl→R-H+MeC12(9)WAC8
Once it becomes H type.

In this hydrochloric acid for regeneration, NaC1 is added according to reaction formula (8).
Some of them return to their original Na form according to the following reaction formula (% formula 10), but in reality, H
Since the amount of Cl is large, it is thought that the reaction represented by formula (9) takes center stage.

MeC12 generated according to equations (9) and (10) enters the heavy metal ion recovery section 5.

Next, recycled caustic soda is led from the recycled liquid storage section 4,
Water is passed through 5BA10.

Since the resin in 5BA10 is in the SO4 type according to reaction formula (7), it reacts in 5BA10 as follows,
R-8O4+NaOH→R-OH+Na2SO4(11
) The resin is returned to its original OH form.

The regenerated liquid that has passed through 5BA10 is further passed through WAC8, where it reacts with the resin that has been converted to H type according to reaction formula (9), but the regenerated liquid contains excess NaOH and reaction formula (11).
), so it contains Na2SO4 produced by
R-H+NaOH→R-Na+H20(12)R-H+
The reaction shown by Na2SO4→R-Na+H2804 (13) progresses and the resin returns to its original Na form, and H2
O and H2SO4 are produced.

This H2SO4 causes a neutralization reaction with an excess amount of NaOH, but since NaOH is present in an even larger excess, it is completely neutralized after being guided to the neutralization processing section 6.

It goes without saying that when a type of WAC8 is used, KOH may be used instead of NaOH as the regenerating liquid.

Although this method can achieve the intended purpose,
In general, when the concentration of inorganic acids present in heavy metal-containing wastewater is high and the relative concentration of heavy metal ions to the inorganic acid concentration is low, when water is passed through WAC8, the above equations (1) and (2) In addition to the ion exchange shown in, for example, R-Na+H2SO4→R-H+Na2SO4 (14)
As the reaction shown in (1) progresses, the resin in the WACB is regenerated into the H type, which may have an adverse effect on the intended purpose of adsorbing heavy metal ions, making it impossible to perform a fully satisfactory treatment.

The present invention has been made in view of the above-mentioned circumstances, and it is capable of always achieving a stable heavy metal ion removal effect regardless of the acid concentration or heavy metal ion concentration in heavy metal-containing waste liquid, and producing stable pure water. The purpose of the present invention is to provide a method for treating wastewater containing heavy metals.

The structure of the present invention that achieves this objective is that heavy metal-containing wastewater is treated in advance with a weakly basic anion exchange resin, and then brought into contact with a weakly acidic cation exchange resin to adsorb and remove heavy metal ions. The gist lies in that the treatment is performed using a strongly acidic cation exchange resin and a strongly basic anion exchange resin.

Therefore, the structure of the present invention is characterized in that a weakly basic anion exchange resin treatment step is added before the treatment method shown in FIG. We are trying to remove as much as possible, thereby increasing the removal and recovery effect of heavy metal ions.

The configuration and effects of the present invention will be explained below based on the drawings which are examples, but the present invention should not be limited to the following examples.

FIG. 3 is a flow sheet showing an example of the treatment process according to the present invention, in which wastewater discharged from the heavy metal-containing wastewater storage section 1 is first passed through a weak basic anion exchange resin tower 7 (hereinafter referred to as WBA).

Since WBA7 is used to remove and recover free acids, the OH type is generally used, and reactions in WBA7 are shown, for example, as follows.

R-OH+H2804→R-804+H20 (15) The wastewater from which free acids have been removed as much as possible is then treated with W.
Water is sequentially passed through AC8, 5AC9, and 5BA10, but the outline of this treatment process is the same as that explained in FIG. 2, so a description thereof will be omitted.

Next is the regeneration of these ion exchange resins. WAC8,
The reproduction method of 5AC9 and 5BA10 is the same as that explained in FIG. 2, so a description thereof will be omitted.

However, the regenerating caustic soda discharged from the regenerating liquid storage section 4 is not directly passed through the neutralization processing section 6 after regenerating 5BA10 and WAC8, but is further utilized for regenerating WBA7.

That is, since this regeneration solution contains excess caustic soda, when this water is passed through WBA7, the following ion exchange reaction takes place with R-8O4 produced by reaction formula (15), and R -8O4 is returned to its original OH form.

R-8O4+NaOH→R-OH+Na2SO4(16
) The sodium sulfate and excess amount of NaOH-containing liquid produced here are directly led to the neutralization treatment section 6 and then subjected to a complete neutralization reaction.

The above examples are merely representative embodiments of the present invention, and the types of acid groups and salt substrates in each ion exchange resin, H type, Na type,
There are no limitations on the active state of the K-type, etc., or the resin regeneration process, etc., and those that remove free acids from heavy metal-containing wastewater, heavy metal ions, and salts generated in the previous process in a predetermined order. All are included within the technical scope of the present invention.

Furthermore, the heavy metals to which the present invention is applied include all heavy metals except for light metals such as alkali metals and alkaline earth metals, and the heavy metal-containing wastewater includes all wastewater containing heavy metals, but representative examples include: For example, plating waste liquid,
Examples include various industrial waste liquids such as scouring waste liquid, mineral processing waste liquid, pile water, electric wire factory waste liquid, etc.

Since the present invention is constructed as described above and the WBA treatment step is performed before the heavy metal removal step by WAC treatment, free acids in wastewater are removed as much as possible by WBA.

Therefore, during WAC treatment, the adsorption of heavy metal ions is less likely to be hindered, and heavy metal ions are almost completely adsorbed and removed.

Therefore, the overload of SAC and SBA due to insufficient adsorption of heavy metals is reduced, the life of the ion exchange resin is extended, and the purity of the recovered treatment liquid is extremely high, increasing its utilization rate.

Furthermore, since there is no need to use a special regenerating liquid when regenerating WBA and the WAC regenerating liquid can be used as is, there is no fear that the amount of regenerated waste liquid will increase.

[Brief explanation of drawings]

Figures 1 to 3 are flow sheets showing the steps for treating waste liquid containing heavy metals, with Figure 1 depicting a known method, Figure 2 depicting an improved method, and Figure 3 depicting the method of the present invention. 1... Heavy metal-containing wastewater storage section, 2...
Treated water recovery section, 3, 4... Regeneration liquid storage section, 5.
... Heavy metal ion recovery section, 6 ... Neutralization processing section, 7 ... Weak basic anion exchange resin (WB
A), 8... Weakly acidic cation exchange resin (WAC
), 9...strongly acidic cation exchange resin (SAC),
10... Strong basic anion exchange resin (SBA)
.

Claims (1)

[Claims] 1. When removing and recovering heavy metal ions by contacting heavy metal-containing wastewater with an ion exchange resin and purifying and recovering the wastewater, the wastewater is treated with a weakly basic anion exchange resin, and then heavy metals are removed using a weakly acidic cation exchange resin. 1. A method for treating wastewater containing heavy metals, which comprises adsorbing heavy metals and then treating with a strongly acidic cation exchange resin and a strongly basic anion exchange resin.