JPS5915710B2 - Method for removing heavy metals from aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing heavy metals from an aqueous solution containing heavy metal ions by treating the aqueous solution with a resin having a polyalkylene polyamine type chelate forming group.

Specifically, the resin has a polyalkylene polyamine type chelate forming group (hereinafter referred to as polyalkylene polyamine type chelate resin).

) when treating aqueous solutions containing heavy metal ions, NaC
The present invention relates to a method for increasing the metal adsorption capacity of a resin by allowing an alkali metal salt or alkaline earth metal salt such as 1, CaC12, Na2SO4, etc. to be present in the aqueous solution.

Recently, in connection with pollution problems and resource recovery, the problem of capturing heavy metals in mine and factory wastewater has been emphasized, and various metal adsorbents have been researched and developed as a countermeasure.

These metal adsorbents include those in which so-called chelating agents such as dithizone and 2-mercaptobenzothiazole are supported on carriers such as activated carbon or silica gel, and so-called chelate resins in which various chelate-forming groups are immobilized on synthetic resins. However, each has advantages and disadvantages in terms of the ease of regenerating the adsorbent that has adsorbed heavy metals, that is, the possibility of repeated use, and the difficulty of manufacturing.

Among these, polyalkylene polyamine type chelate resins can be easily regenerated by treatment with an aqueous acid solution such as hydrochloric acid or sulfuric acid (reusable, relatively inexpensive, easy to manufacture, etc.). Therefore, it is an excellent adsorbent in practical use.

While investigating a method for treating a heavy metal-containing aqueous solution using a polyalkylene polyamine type chelate resin, the present inventors found that when treating a heavy metal-containing aqueous solution with a polyalkylene polyamine type chelate resin, NaCl, CaCl2,
The present invention was achieved by discovering a new fact that the metal adsorption capacity of a resin is increased by coexisting an alkali metal salt or alkaline earth metal salt such as Ca S 04 in an aqueous solution containing heavy metals.

The polyalkylene polyamine type chelate resin of the present invention includes, for example, the following.

That is, a resin having a crosslinked bond obtained by reacting a polyalkylene polyamine with epihalohydrin or alkylene dibromide, or a crosslinked copolymer having an aromatic ring, such as a crosslinked copolymer of styrene and divinylbenzene, is reacted with methyl chloromethyl ether or the like. These are resins obtained by further reacting polyalkylene polyamine after halomethylation.

Examples of the heavy metal ions treated in the present invention include ions of heavy metals such as zinc, cadmium, mercury, copper, and manganese.

In addition, in the present invention, when a heavy metal-containing aqueous solution is treated with a polyalkylene polyamine type chelate resin, the salts coexisting in the heavy metal-containing aqueous solution are hydrochlorides of alkali metals such as Na, K, Ca, Mg, and alkaline earth metals. , sulfates, nitrates, etc., and the amount of coexisting salts varies depending on the salts coexisting and the target heavy metal, but is 10 ppm or more, preferably 40 ppm or more.

The reason why the metal adsorption capacity of the resin increases due to the coexistence of these salts is currently unknown, but it is presumed that the chelate formation reaction rate of the polyalkylene polyamine type chelate resin increases due to some effect. Ru.

Treatment methods for heavy metal-containing aqueous solutions include filling a column with chelate resin and passing the heavy metal-containing aqueous solution through the column, or stirring and mixing the heavy metal-containing aqueous solution and the resin, and then separating the resin and liquid by decanting or filtration. Methods employed in normal ion exchange unit operations, such as separation methods, are applicable.

The method for passing the liquid through the column is not particularly limited, and can be carried out by a conventional method, and can be arbitrarily determined as appropriate, such as an upward flow method or a downward flow method.

The pH of the liquid to be treated is usually 2 to 12, preferably 3.5 to 7.
Adjust to.

If the pH value is too low, the metal adsorption ability of the resin will decrease, and if the pH value is too high, metal hydroxides will precipitate, which may impede the operation.

By treating the resin that has adsorbed heavy metals with an aqueous acid solution such as 1 to 6 N sulfuric acid, the adsorbed heavy metals can be easily recovered as acid salts.

The resin treated with an acid aqueous solution is thoroughly washed with water, and then further treated with an alkali such as 1 to 6N NaOH or KOH to make the resin into a free form, washed with water again, and used again to remove heavy metals. can do.

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Example 1 Styrenic polyethylene polyimine type chelate resin CR
A glass column with a diameter of 15 mm was filled with 100 ml of free resin -20 (manufactured by Mitsubishi Chemical Industries, Ltd., trade name), and a liquid having the composition shown in the table was passed in a downward flow at a space velocity of 10/hr. did.

At this time, the temperatures of the liquid to be treated and the resin tower were maintained at 18°C.

The concentration of Cu+E in the liquid flowing out from the resin tower is lpp
The amount of liquid passed and the through-flow exchange capacity of the resin until it reached m were determined.

The results are shown in the table below. The through-flow exchange capacity of Ca 2 in the presence of CaCl 2 was dog.

Example 2 A glass column with a diameter of 15 mm was filled with 100 ml of Diaion CR-20 free resin, and a liquid having the composition shown in the table was passed through the column in a downward flow at a space velocity of 10/hr.

At this time, the temperatures of the liquid to be treated and the resin tower were maintained at 18°C.

The concentration of Cu+ in the liquid flowing out from the resin tower is 1 pp
The amount of liquid passed and the through-flow exchange capacity of the resin until it reached m were determined.

The results are shown in the table below.

Example 3 The same test as in Example 1 was conducted except that the composition of the treatment liquid was changed, and the results shown in the following table were obtained.

The coexistence of calcium sulfate increased the Cu cubic cross-flow exchange capacity of the resin.

Example 4 The same test as in Example 1 was conducted except that the composition of the treatment solution was changed and the end point was set at Zn+t'-1 ppm, and the results shown in the following table were obtained.

The coexistence of calcium chloride increased the Zn+ flow exchange capacity of the resin.

Claims (1)

[Claims] 1 When treating an aqueous solution containing heavy metal ions with a free polyalkylene polyamine type chelate resin to remove heavy metal ions from the aqueous solution, the presence of alkali metal salts and/or alkaline earth metal salts in the aqueous solution A method for removing heavy metal ions in an aqueous solution, the method comprising: