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This post was last edited by hesonchang214 on 2020-3-19 at 18:05. 1. pH value: Different materials have varying pH value ranges suitable for use; for example, the pH range suitable for acetate fiber membranes is 3–8, while that for aromatic polyamide membranes is 4–10. The pH range for DuPont-type nylon hollow fiber membranes is 1.5–12. When the pH value of the feed solution exceeds the operational range specified for the membrane, it can cause harmful effects such as hydrolysis and aging on the membrane, leading to a decrease in water production volume. This results in a continuous decline in the membrane’s performance until the membrane is damaged. Generally, the pH value during operation of acetate fiber membranes should be maintained between 4 and 7, while that for aromatic polyamide membranes should be kept between 3 and 11; the allowable pH range for composite membranes is approximately 2 to 11. 2. Temperature: During the reverse osmosis process, the temperature of the feed solution increases as the operation proceeds. Within a certain range of Χ, an increase in temperature leads to a decrease in the viscosity of the feed solution, which facilitates an increase in the amount of water produced through reverse osmosis. Generally, for every 1°C increase in temperature, the water-permeation capacity of the membrane increases by about 2.7%. The water permeability value indicated on the membrane for commercial use is generally based on water temperatures of 24–25°C; the actual permeability at the operating temperature must be calculated using correction factors. It should be noted that the operating temperature must not exceed the heat resistance limit of the membrane; otherwise, it will affect the membrane’s service life. 3. The pH value of the feed solution, as well as the levels of suspended solids and microorganisms present in it, all affect the efficiency of reverse osmosis. Therefore, effective pre-treatment measures must be taken on the raw water when necessary, such as pH adjustment, filtration, and disinfection, in order to maximize the performance of reverse osmosis.