JPS6014906A - Concentrating method of aqueous solution containing dissolved nonvolatile substance - Google Patents

Abstract

PURPOSE:To increase the concentrating efficiency in the wide range of solutes, concns., and temps. by holding an aq. soln. on one side of a porous membrane having specified diameter which is inert to the aq. soln. to be treated contg. a nonvolatile substance, and holding a low-temps. liquid on the opposite side of the membrane. CONSTITUTION:A porous membrane 1 made of polytetrafluoroethylene, for example, having 0.05-150mu pore diameter which is inert to an aq. soln. to be treated contg. a nonvolatile substance is placed in the center to constitute a high- temp. side cell 2 and a low-temp. side cell 3. When the aq. soln. contg. dissolved nonvolatile substance is charged into the high-temp. cell 2 and low-temp. water or an organic or an inorganic aq. soln. into the low-temp. cell 3, the concn. of the nonvolatile substance in the high-temp. side aq. soln. is increased with time. The temp. difference between the high-temp. side and the low-temp. side is regulated preferably within the range of 3-70 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of concentrating a non-volatile substance dissolved aqueous solution using a porous membrane.

More specifically, the present invention relates to a method of concentrating non-volatile substances dissolved in an aqueous solution using a salinity difference as a driving force using a porous membrane that is inert to an aqueous solution to be treated containing non-volatile substances.

Traditionally, the reverse osmosis method is used as a chain line method for aqueous solutions using membranes.
Known methods include the limitless method and the electric bamboo method, which use a pressure difference or a potential difference as a driving force. On the other hand, the driving force for membrane separation in the method of the present invention is the temperature difference. Conventionally, membrane permeation using a temperature difference as a driving force is sometimes called thermal osmosis or thermal dialysis depending on the pore size of the membrane used, but the present invention falls into the category of thermal dialysis. That is, by storing a mixture solution on both sides of the membrane across a porous membrane, and keeping the two liquids separated by the membrane at different temperatures, water selectively permeates through the membrane from the high temperature side to the low temperature side, and the high temperature side It increases the concentration of volatile substances. Until now, there have not been many research reports on such thermal dialysis1.For example, Gieta et al. reported that acetic acid, sodium acetate, phenol, etc. can be concentrated in an aqueous solution at high temperature using a porous membrane made of glass fibers hardened with acrylic resin. There is (Oan.

It is. However, the porous membrane used in this report uses acrylic resin as a binder.

It has low resistance to acidic or alkaline solutions, and membrane performance tends to deteriorate when exposed to relatively high concentration organic solvents such as DMF and DM80, or condensation occurs because the membrane surface becomes active against the solution. I can't. Therefore, the present inventors conducted intensive studies using various porous membranes, and found that by using an inert porous membrane, an excellent method that can be used over a wider range of solutes, a wider range of concentrations, and a wider range of temperatures than the previously reported method. We found a method and arrived at the present invention. In the present invention, membrane-membrane activity means that the membrane is wetted by a water bath.

That is, the present invention provides a method for concentrating a non-volatile substance-dissolved aqueous solution, which is inert to the aqueous solution containing a non-volatile substance and is characterized by a concentration of 0.05 μm to 150 μm.

The inert porous membrane used in the present invention has a processing temperature (for example, 30
C) refers to a porous membrane that has a low affinity with the solution when immersed in an aqueous solution to be treated or a 15% ethanol aqueous solution, and therefore does not get wet by the solution. Examples of such a film include a film made of a hydrophobic material with low surface energy. For example, fluorine-containing polymers such as polytetrafluoroethylene, poly(trifluorochloroethylene), poly(hexafluorotetrapyrene), polyvinylidene fluoride, hydrocarbons such as ethylene, tetrapyrene, vinyl chloride, etc. Polymers made of μ-gunized hydrocarbon monomers,
Hydrophobic polycondensation polymers such as aromatic polyester, aromatic polyamide, and aromatic polysulfone, and silicon-containing polymers such as polydimethylsiloxane are hydrophobic and have low surface energy and are suitable as membrane materials for use in this method. It is. Among these, polytetrafluorocarbons are mostly made of ethylene. In the concentration according to the present invention, in most cases, the volume flow occurs from the high temperature side to the low temperature side, but even if this volume flow is forcibly stopped, concentration can be performed on the high temperature side.

The non-volatile substance that can be concentrated by the method of the present invention refers to a substance in which the non-volatile substance composition in the liquid in the vapor-liquid equilibrium of the aqueous solution is greater than the non-volatile substance composition in the gas.

Examples of substances with such properties include organic low molecular compounds such as 1,3-butanediol, 1,4-butanediol, glycerin, ethylene glycol, dimethyl sulfoxide, dimethylformamide, acetic acid, and tetrapionic acid; polyacrylamide, poly N-vinylbitetralidone,
Carboxymethyl cell is made of one substance, a polymer compound such as hydroxyethyl cellulose, Na01. KOI, NaOH
, inorganic compounds such as sulfuric acid, and inorganic salts of organic compounds such as sodium acetate, sodium gluconate, and potassium acrylate. The present inventors have discovered that these values increase with the non-volatile time.

The appropriate temperature difference between the high temperature side and the low temperature side is in the range of 3 to 70C, the temperature of the aqueous solution on the high temperature side is 30 to 90C%, preferably 40 to aOC, and the temperature of the aqueous solution on the low temperature side is from 40G to the melting point. The temperature is preferably selected between 30C and the melting point. The thickness of the porous membrane varies depending on its material and the composition of the aqueous solution to be treated, but is generally between 20 and 300 mm.
It is 0μ, preferably 50 to 1000μ.

Applications of the condensation method according to the present invention include the concentration of an aqueous solution of a non-volatile substance produced at a relatively high temperature, or the recovery of an aqueous raw material solution in a system that reacts at a relatively high temperature.

EXAMPLES The present invention will be specifically explained below with examples, but the present invention is not limited by these in any way.

Example 1 Porous membrane made of polytetrafluoroethylene (Daikin Co., Ltd.'s registered trademark Borifun Paper PA - water flow jacket,
6 is a stirrer, 7 is a thermometer, 8 is a capillary for measuring the amount of liquid permeated through the membrane, 9 is a hot water circulation line, 10 is a cold water circulation line,
11 is a motor. The effective area of the membrane in the cell is 38.
It was 5d. 11C15%1,4 on both sides of the separation cell
- Pour 270ml of butanediol water bath solution into the left cell (high temperature side cell) 2 and the right cell (low temperature side cell).
When hot water (C6OC) and cold water (OC) from a constant temperature bath were passed through the outer jacket parts 4 and 5 of 5, respectively, the temperature of the solution in the cell on the high temperature side was constant at 51.5 C, and the temperature of the solution in the cell on the low temperature side was constant at 165 C. Ta.

When the concentrations of 1,4-butanediol in the high-temperature and low-temperature cells were measured over time after a certain period of time, the concentration in the high-temperature cells increased with time, while the concentration in the low-temperature cells decreased with time. After 7 hours, the concentration of 1,4-butanediol in the high temperature cell is 19.2%, and the concentration in the low temperature cell is 7.7.
%Met.

The volumetric flow was from the hot side cell to the cold side cell.

The flow rate at 3 hours after the start was 0.06117 minutes. The membrane used showed no wetting even after 24 hours of measurement, and was an inert membrane. Furthermore, this film was inactive and did not wet with 15% ethanol at 25G.

Examples 2 to 8 Concentration was carried out in the same manner as in Example 1, except that various solutions shown in Table 1 below were used instead of the 15% 1,4-butanediol aqueous solution in Example 1. The solution concentrations in both cells at the initial stage and after 7 hours of measurement are as shown in Table 1. In both cases, the concentration of non-volatile substances increased in the high temperature side cell, and a concentrated solution could be obtained.

1 Comparative Example 1 In Example 1, a porous membrane made of silicon boride fiber (Milipore) was used instead of the porous membrane made of polytetrafluoroethylene.
When the same 1% acetic acid aqueous solution was added to the measurement separation cell used in Example 1 using a 100% Thermostat (AP-20), and constant-temperature water at the same temperature as in Example 1 was passed through the high-temperature side and low-temperature side jackets, the cell The temperature inside was constant at high temperature [47.5C and low temperature 2L8C]. When we measured the changes in the purity of both cells after a certain period of time, we found that within one hour after the start of the measurement, there was a concentration change on the high temperature side, but after that, the concentration changed to 1 due to back diffusion.
The difference in concentration between both cells disappeared. This membrane is 25tl:',
It was wettable to a 15% ethanol aqueous solution and also wetted to a 1% acetic acid aqueous solution.

Comparative Example 2 Porous membrane made of silicon boride fiber (AP manufactured by Milipore)
-20) was immersed in an aqueous sodium hydroxide solution of P813, it swelled abnormally and could not maintain its membrane shape after several hours, so it could not be applied to the concentration of the present invention.

[Brief explanation of the drawing]

FIG. 1 is a schematic @-plane diagram of an example of a separation cell used in the present invention. 1: Inert porous membrane, 2: High temperature side cell, 3: Low temperature side cell.

Claims (1)

[Claims] The above aqueous solution is held on one side of a porous membrane having a pore size of 0.05 μm to 150 μm, which is inert to the aqueous solution to be treated containing non-volatile substances, and the aqueous solution is held at a lower temperature than the above aqueous solution on the other side across the layer. 1. A method for concentrating a non-volatile substance-dissolved aqueous solution, characterized by increasing the non-volatile substance condensation of the aqueous solution at a higher temperature than by holding water or a water bath liquid.