JPS61287492A - Method and apparatus for producing ultrapure water - Google Patents

Abstract

PURPOSE:To produce the titled ultrapure water having an extremely low content of total org. carbon (TOC) by combining membranous materials having different membrane potentials, treating water in multiple stages and effectively removing org. low mol.wt. compds. resulting from humic acid or the like. CONSTITUTION:In the process for producing ultrapoure water having <=100ppb TOC from raw water, multistage separation membranes consisting of >=2 stages are used and the separation membranes in at least two stages differ in the membrane potential measured under the following conditions by >=5mv. The membrane potential is defined as the value measured at 25 deg.C by using an aq. KCl soln. having 10<-3>mol/l concn. at the lower concn. side and 4X10<-3>mol/l at the higher concn. side. Namely, the separation membrane is selected in accordance with an org. low mol.wt. compd. having positive, negative and neutral ions resulting from humic acid, etc., causing an increase in TOC, water is treated in multiple stages by using a combination of membrane materials having respectively different membrane potentials, the org. low mol.wt. compds. are effectively removed and ultrapure water having an extremely low content of TOC can be produced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for producing ultrapure water that efficiently and economically removes organic components (TOC) from water. and manufacturing equipment. More specifically, the present invention relates to a technique that can significantly reduce TOC by using multi-stage mt membranes with different membrane potentials.

[Conventional technology]

Ultra pure water with low TOC is ultra LS which requires high quality water.
It is required as an indispensable cleaning process in the electrical and electronic fields such as I manufacturing. In addition, there are high demands for raw drug crystal dilution water and process water used in the pharmaceutical industry, which are used in these manufacturing fields.

In order to meet these demands, membrane separation technology and ion exchange separation technology are being applied. The separation method using a semi-permeable membrane that utilizes the principle of reverse osmosis has traditionally been used to produce pure water from seawater and can water, as well as from various industrial wastewaters such as dyes, jelly, and dipping sauce. It is used industrially in many fields such as the recovery and concentration of valuable substances, and the selective separation and removal of pollutants.

In the field of electronics industry, reverse osmosis is also used to eliminate ions in the feed water and reduce the amount of ion exchange (or 1) used in the subsequent process. This is a common method for purifying water.

Recently, with the increase in the density of LSIs, there has been a demand for the development of a method for removing organic substances from water, which were previously very difficult to separate. These organic substances in water are low-molecular substances dissolved in water, and have a molecular weight of about 500 or less. These are typically derived from humic acid decomposition, microbial metabolites, medicines, and industrial waste.

However, conventionally, DingOC derived from these Iba molecular weight substances
There is no technology to remove ultrapure water and obtain ultrapure water at low cost, and improvements to this technology have been desired.

(Problems to be solved by the invention) The present invention improves the above-mentioned problems of the prior art, and by combining membrane materials with different membrane potentials and performing multi-stage processing, organic low molecular weight caused by humic acid, etc. To provide a technology for producing ultrapure water that effectively removes compounds and has extremely low levels of OC.

Organic low molecular weight compounds 1 caused by humic acid etc. that cause an increase in OC, those with a positive charge,
A mixture of negatively charged and neutral substances exists. Therefore, the present inventors have discovered that it is effective to select a membrane in accordance with the charge state of the substance contained therein, leading to the present invention.

(L-intensive means to solve the invention) In order to achieve the above object, the present invention consists of the following configuration.

F(1) A method for obtaining ultrapure water under TOC1001)I)bJx from raw water, using multi-stage separation membranes on two stages, and the membrane potential of at least two stages of separation membranes is
1. A method for producing ultrapure water, characterized in that the following measurement conditions differ by 5 millipol 1 to 1".

(Membrane potential, however, refers to the membrane potential at 25°C when the concentration of the KCσ aqueous solution is 10.3 mol/(10.3 mol/(1) on the low concentration side and 4×10-3 mol/(1) on the high concentration side.

) (2) 1! Ultrapure water with TOC1001111b or less from raw water! ! In the equipment for producing water, the first stage raw water pump, the first
At least a stage separation membrane, a second stage raw water pump, and a second stage @membrane are provided, and the membrane potentials of the at least two stages of separation membranes must differ by 5 millivolts or more under the following measurement conditions. Ultrapure water production equipment featuring:

(However, the membrane potential refers to the membrane potential at 25° C. when the concentration of the aqueous solution is 10 −3 mol/σ on the low Ii degree side and 4×10 −3 mol/σ on the high concentration side. ) J First, a sample configuration of the present invention will be explained using the drawings.
The figure shows a two-stage processing technique that is one embodiment of the basic wrestling of the present invention. First stage raw water pump 2 from raw water line 1
The raw water is supplied to the first stage separation membrane 3, where the first
Perform stage water purification treatment. Waste liquid is discharged through line 5.

Next, the treated water taken out from the first stage treated water line is preferably stored in an intermediate tank 4 (not necessarily a tank, but may be a tank with a thick pipe), and the second stage raw water pump 6 is pumped. The ultrapure water is taken out and discharged from the line 8.The line 9 is a waste liquid pipe.The separation membrane can have as many stages as there are two or more stages. It's okay.

As the at least two-stage separation membrane, at 25°C, the amount of KGα aqueous solution is reduced to
-a mol/σ, and the membrane potential at CJ of 4×10 −3 mol/σ on the high concentration side is used by 5 millipores or more.

Here, the membranes whose membrane potentials differ by 5 millivolts or more may be any combination of membranes, and specifically,
Acetic acid 1? Lulose type (neutral), polyamide type, cross-linked polyamine type, cross-linked 1n polyamine 7/polyether type,
Cross-linked polyether type with positive charge of 1 or more>, polyacrylonitrile, polyether, sulfonated polysulfone (
(negatively charged) etc. are used in appropriate combinations. Membrane types of reverse osmosis membranes made from these membrane materials include asymmetric membranes and composite III membranes. Membrane element structures that can be used in water purification equipment include spiral type, hollow fiber type, dicobbler type, and plate ant.
There are frame types.

In this way, organic low molecular weight compounds with different charge characteristics such as humic acid, which cause an increase in OC, can be efficiently separated by a membrane having a charge corresponding to each iJ. Ultrapure water with the following concentration of OC can be obtained.

In a more preferred embodiment of the present invention, the 2f! iJ's-H membrane is used. This is because the charge characteristics can be handled by different organic low molecular weight compounds.

In the present invention, the membrane electrolyte (KCβ aqueous solution) is heated at 25°C.
The reason why the concentration on the Iba concentration side was 10-3 morph/ρ and the concentration on the high-concentration side was 4X10-3 morph/ρ was determined as follows. It is relatively different depending on the change in the concentration (corresponding to the OCt of raw water).
This is because the typical value that must be passed when ultra-pure water is processed from 10-2 degree Is) to ultra-pure water has fluctuated.

As the raw water to be supplied to the reverse osmosis membrane of the present invention, city water, coagulation)-superhydration, activated carbon)-superhydration, ultraviolet irradiation 13=1 decomposed water, etc. can be used. Between the first-stage reverse osmosis membrane treatment and the second-stage reverse osmosis membrane treatment, there may be steps such as ion exchange treatment, active charcoal treatment, ultraviolet decomposition, and other methods.

〔Example〕

A commercially available micro organic matter analyzer was used to analyze organic matter in water. The analyzer is a high-sensitivity OC meter model 18001) r) l) manufactured by Amerikuchi Co., Ltd. (USA), range range: O
~500Dr)b, reproducibility: ±2% (±10ppb)
. Range range: O~250011pb, reproducibility: 2% soil
(±50DDb>.Temperature 25℃ 1KCθ The concentration of the aqueous solution is 10-3 mol/ρ on the low concentration side and 4 mol/ρ on the high concentration side.
The method for measuring X10-3 mol/L is as shown in FIG.

Example 1 In the process shown in Figure 1, a spiral-type aromatic polyamide composite membrane (Toshi Co., Ltd.'! Membrane, membrane potential -12 millivolts) was used as the reverse osmosis membrane element in the first stage reverse osmosis membrane. Pressure 15kq/cJ of water to the front stage reverse osmosis membrane
The first-stage reverse osmosis permeated water was supplied to the second-stage reverse osmosis membrane at a pressure of 15 kq/cJ. At this time, the organic matter concentration in the city water supplied to the front stage reverse osmosis membrane was 1200 Dpb, and the organic matter fA degree in the water permeated through the front stage reverse osmosis membrane was 921111b. Furthermore, when the permeated water of the first stage reverse osmosis membrane is supplied to the second stage reverse osmosis membrane, the organic matter concentration in the second stage reverse osmosis membrane permeated water is 3 (]) rl
l).

The desalination performance of J Cymen 1~ used here was 96% for the cellulose acetate membrane, and the water production amount was IT,/m2・day (NaC11
500pI)m, pressure horn 30ki,/cJ). In addition, the desalting properties of the aromatic polyamide J-” composite membrane element are 180%, and the desalting properties are 1112 T/7112/day (N
aCI 2000111'1m, pressure 20kg/cr.

As a result of this strike, we were able to obtain ultrapure water with a preferable low concentration of DOC.

Practical Example 2 An experiment was conducted by replacing the membranes used in Example 1 in the front and rear stages. That is, a spiral-type aromatic polyamide composite membrane was used as the front-stage reverse osmosis membrane element 1, and a spiral-type cellulose acetate asymmetric membrane was used as the rear-stage reverse osmosis membrane element 1. Front and rear reverse osmosis membrane operating conditions (
The organic matter concentration in the permeated water in the first stage was 94 ppb, and the concentration of organic matter in the water permeated through the reverse osmosis membrane in the second stage when the water permeated through the first stage reverse osmosis membrane was supplied to the second stage reverse osmosis membrane. The organic matter concentration was 42 DDb. The desalination performance of the first stage element used here was 80%, and the amount of water produced was 2.5 tons/m2 m day (NaCI 2000 DDm,
Pressure: 20 ky/cl') The desalination performance of the latter element is 9.
7%, water production amount is 0.7 tons/m2・day (NaCI 150
0DDm, pressure 30 kq/cJ>.

As a result, ultrapure water with a preferable low concentration of TOC could be obtained.

Comparative Example 2 A spiral type aromatic polyamide composite membrane was used as the front stage reverse osmosis membrane Niremen 1, and the same type of membrane element used in the front stage was used as the rear stage reverse osmosis membrane element. The operating conditions for the front and rear reverse osmosis membranes were the same as in Example 1. At this time, the degree of crystallinity in the water permeated through the front stage reverse osmosis membrane was 181p. In addition, the water permeated through the reverse osmosis membrane in the first stage,
The organic matter concentration in the water permeated through the rear reverse osmosis membrane when supplied to the rear reverse osmosis membrane was 120%.

The desalination performance of the front element used here was 75%,
The amount of water produced is 2.5T/i2・day (NaC1200Oppm
, repulsion force 20kq/c dimension) weak salt ↑ repellency to the latter Niremen 1 is 80%, fresh water N is 2.5 tons/yn2・R (NaC12
000DDm, pressure 20 kq, / crK).

The results were significantly worse than those in Example 1.2.

〔Effect of the invention〕

In accordance with the above-mentioned technology, the present invention selects a separation membrane in response to an increase in TOC and an organic low molecular weight compound having positive, negative, and neutral ions caused by 1C humic acid, and increases the membrane potential. By combining different membrane materials and performing multi-stage processing, organic low-molecular compounds can effectively remove compounds and TO
This has the remarkable effect of achieving V-formation of ultrapure water with an extremely low C content.

Furthermore, it is highly practical in industrial terms, as it is easy to operate the device, and it is easy to regenerate the membrane. In addition, high-quality water can be produced industrially and stably, making a significant contribution to this industry.

[Brief explanation of drawings]

FIG. 1 shows a two-stage processing technique that is one embodiment of the Fumoto process of the present invention. FIG. 2 shows the relationship between membrane potential difference and solution concentration. FIG. 3 shows a method for measuring membrane potential difference. 2; 1st stage raw water pump; 3; 1st stage separation membrane 4; intermediate tank; 6; 2nd stage raw water pump 7; 2nd stage separation membrane 8; ultrapure water extraction line.

Claims (5)

[Claims] (1) In a method for obtaining ultrapure water with a TOC of 100 ppb or less from raw water, two or more multi-stage separation membranes are used, and the membrane potential of at least two separation membranes differs by 5 millivolts or more under the following measurement conditions. 1. A method for producing ultrapure water, characterized by using ultrapure water. (However, membrane potential is the membrane potential at 25°C when the concentration of KCl aqueous solution is 10^-^3 mol/l on the low concentration side and 4 x 10^-^3 mol/l on the high concentration side. say.) (2) In the method described in claim (1),
A method for producing ultrapure water, characterized in that at least two stages of separation membranes use two or more types of membranes selected from a substantially neutral membrane, a positively charged membrane, and a negatively charged membrane. (However, a positively charged membrane is one that exhibits a negative membrane potential under the same conditions, a negatively charged membrane is one that exhibits a positive membrane potential under the same conditions, and a nearly neutral membrane is one that exhibits a positive membrane potential under the same conditions.) (This refers to a film with a value between these values.) (3) In an apparatus for producing ultrapure water with a TOC of 100 ppb or less from raw water, at least a first-stage raw water pump, a first-stage separation membrane, a second-stage raw water pump, and a second-stage separation membrane are provided, and The membrane potential of the at least two stages of separation membranes is
An apparatus for producing ultrapure water, characterized in that the membranes differ by 5 millivolts or more under the following measurement conditions. (However, membrane potential is the membrane potential at 25°C when the concentration of KCl aqueous solution is 10^-^3 mol/l on the low concentration side and 4 x 10^-^3 mol/l on the high concentration side. say.) (4) In the device according to claim (3),
At least two stages of separation membranes are selected from a substantially neutral membrane, a positively charged membrane, and a negatively charged membrane.
An apparatus for producing ultrapure water characterized by a membrane that is more than 100% pure. (However, a positively charged membrane is one that exhibits a negative potential under the same conditions, a negatively charged membrane is one that exhibits a positive potential under the same conditions, and a nearly neutral membrane is one that exhibits a negative membrane potential under the same conditions.) It refers to the membrane of value.) (5) In the device according to claim (3),
An apparatus for producing ultrapure water, characterized in that an intermediate tank is provided between a first-stage separation membrane and a second-stage raw water pump.