GB/T 40258-2021Evaluation method for corrosion resistance of hollow fiber membrane to chemical cleaning agent (English PDF)

3.6 Pure water flux

The volume of pure water passing through the membrane per unit area and unit time at a certain pressure and temperature. [Source: CJ/T 530-2018, 3.9]

3.7 Retention

It indicates the ability to remove specific components. [Source: GB/T 32360-2015, 3.7]

3.8 Bubble point pressure

The critical pressure when the first bubble appears and leads to continuous bubbles. [Source: GB/T 32361-2015, 3.1]

3.9 Bursting strength

Applying fluid pressure perpendicular to the membrane surface on the membrane surface, the critical pressure when the membrane begins to burst. [Source: HY/T 233-2018, 3.4]

4.1 Principle

At a certain temperature, the hollow fibre membrane sample is sealed and immersed in a certain concentration of acidic or alkaline or oxidizing chemical cleaning agent solution for a certain period of time; and compare the change rate of the performance indicators (including breaking elongation force, elongation at breaking, pure water flux, retention, bubble point pressure and bursting strength, etc.) of the membrane sample before and after immersion; according to the range of the value of the change rate of performance indicators, evaluate the category of corrosion resistance of the hollow fibre membrane to the corresponding chemical cleaning agent.

4.2 Test conditions

Test environment temperature: (20±2) °C; test water temperature for pure water flux and retention: (25.0±0.5) °C.

4.3 Reagents

Unless otherwise specified, only use analytical reagents.

4.6.1

b) Take out the soaked sample; and check the integrity of the sample again according to the inspection pressure specified in 4.5. If the integrity of the sample is unqualified, it is classified as Class-IV. If the integrity is qualified, continue with the following test procedures;

c) Take 70 pieces of blank samples, of which 50 pieces of samples are tested for their breaking elongation force and elongation at breaking according to the provisions of HY/T 213-2016. 5 pieces of samples are tested for the pure water flux according to the provisions of 5.1 of GB/T 32360-2015. 5 pieces of samples are tested for retention according to the provisions of 5.2 in GB/T 32360-2015 or Clause 6 a) ~ g) in GB/T 38949-2020. 10 pieces of samples are tested for bubble point pressure and bursting strength according to the provisions of Appendix A;

d) The soaked test sample is rinsed by water for several times until the pH value of the cleaning water is 6.5~7.5;

e) Take 70 pieces of test samples, and test their breaking elongation force, elongation at breaking, pure water flux, retention, bubble point pressure and bursting strength according to the same methods as procedure c);

f) Respectively take 5 groups of blank samples and test samples for parallel test; and respectively calculate the average breaking elongation forces L0 and, the average elongations at breaking E0 and, and the average pure water fluxes of F0 and, the average retentions R0 and, the average bubble point pressures p0 and, and average bursting strengths B0 and of the blank samples and test samples. According to the formulas (1) ~ (6) in 4.7 to calculate the change rage of performances of test samples against the blank samples.

4.6.2 Corrosion resistance to alkaline chemical cleaning agents

The test procedures for evaluating the corrosion resistance of the hollow fibre membrane to alkaline chemical cleaning agents are as follows:

a) Airtightly soak a test sample in a sodium hydroxide aqueous solution for 24h;

b) Perform tests and calculations according to procedures b), d), e), and f) in 4.6.1.

4.6.3 Corrosion resistance to oxidizing chemical cleaning agents

The test procedures for evaluating the corrosion resistance of the hollow fibre membranes to oxidizing chemical cleaning agents are as follows:

a) Soak a test sample in an aqueous sodium hypochlorite solution for 24h in an airtight manner and avoid light;

b) Perform tests and calculations according to procedures b), d), e), and f) in 4.6.1.

4.7.4 Change rate of retention

The change rate of retention deltaR is calculated according to Formula (4):

Where: deltaR - change rate of retention, in %; R0 - average retention of blank samples, in %;

4.7.5 Change rate of bubble point pressure

The change rate of bubble point pressure deltap is calculated according to Formula (5):

Where: deltap - change rate of bubble point pressure, in %;

p0 - average bubble point pressure of blank samples, in MPa;

4.7.6 Change rate of bursting strength

The change rate of bursting strength deltaB is calculated according to Formula (6):

Where: deltaB - changer rate of bursting strength, in %; B0 - average bursting strength of blank samples, in MPa; […]