[0032] The following examples further illustrate the present invention.
[0033] A method for measuring the content of water-insoluble matter in soda ash by using a microporous filter membrane, including the following steps:
[0034] (1) Selection of microporous membrane
[0035] 1. Material selection: According to the material, the microporous membrane can be divided into nylon 66 (Nylon66), nylon 6 (Nylon6), polyethersulfone (PES), mixed cellulose (MCE), polypropylene (pp), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF) 7 varieties, the following are their characteristics and scope of application:
[0036] Nylon has good hydrophilicity and is suitable for most organic solutions and acid-resistant aqueous solutions.
[0037] PES hydrophilic membrane, resistant to acid and alkali and high temperature, used in terminal filtration.
[0038] MCE is not resistant to organic solvents and strong acid and alkali solutions, and filtration tolerates a pH value of 2-9.
[0039] pp is used in the filtration of biological macromolecule sediments.
[0040] PTFE is resistant to high temperatures, strong acids, strong alkalis, organic solvents and oxidants, and has good chemical compatibility and can withstand most chemical solvents. It is used in water solvent sterilization filtration, vacuum filtration, steam and food industries.
[0041] PVDF protein adsorption rate is extremely low, resistant to chemical corrosion and oxidation.
[0042] The soda ash aqueous solution is strongly alkaline, and the pH value is 11.6, which is corrosive to a certain extent. During the test, it needs to be vacuum filtered and dried at a high temperature of (110±5) ℃ for 2 hours. It can be seen that the filter membrane suitable for the determination of soda ash must be resistant to high temperature, strong alkali corrosion, and vacuum. In summary, PTFE material best meets the requirements.
[0043] 2. Pore size selection: GB/T210.2-2004 "Industrial Sodium Carbonate and Its Test Methods" Part 2: The acid-washed asbestos method for the determination of water-insoluble matter in the industrial sodium carbonate test method has no specific pore size requirements. The PTFE microporous filter membrane has two specifications of 0.22μm and 0.45μm. The standard soda ash samples are determined by this method (the standard value of water-insoluble matter is 0.0079%). The comparison data of the water-insoluble matter measurement results and the standard value are shown in Table 1. .
[0044] Sample serial number
[0045] The above experimental data show that the absolute difference between the measurement results of the two filter membranes with pore diameters of 0.22μm and 0.45μm and the given value of the standard sample is much smaller than the second of GB/T210.2-2004 "Industrial Sodium Carbonate and Its Test Methods" Part: The arbitration method for the determination of water-insoluble matter in the industrial sodium carbonate test method—the acid-washed asbestos method stipulates 0.006%, and the two sets of values are similar. Considering that the filtration rate of 0.45μm is faster than 0.22μm, in order to achieve the purpose of rapid analysis , Finally choose 0.45μm pore size.
[0046] 3. Selection of membrane diameter:
[0047] Select the membrane diameter according to the vacuum solvent filter used.
[0048] (2) Instruments and reagents used:
[0049] 1. Instruments: Electronic balance (precision 0.01g), analytical balance (precision 0.0001g), PTFE microporous membrane (pore size 0.45μm, φ60mm), volumetric filter, vacuum pump, high-type weighing bottle (35×70mm) )
[0050] 2. Reagent: Phenolphthalein (10g/l).
[0051] 3. Analysis steps
[0052] 3.1 Constant weight of filter membrane:
[0053] Place the PTFE microporous filter membrane on the solvent filter, connect the vacuum pump, and filter with 20ml (50±5) ℃ distilled water. The washed filter membrane is placed in a numbered tall weighing bottle and placed in an oven. Dry to constant weight at (110±5)℃.
[0054] 3.2 Sample determination steps:
[0055] Mix the soda ash sample evenly, weigh 20g, accurate to 0.01g, denoted by m, place it in a beaker, add 200ml of water at about 40℃ to dissolve, and maintain the temperature of the test solution at 50±5℃;
[0056] Place the filter membrane with constant weight on the solvent filter, connect the vacuum pump to filter the sample, and wash the insoluble matter with distilled water at (50±5)°C until the water insoluble matter is washed with 20ml of distilled water and the washing solution and 20ml are taken again Place the distilled water in a clean beaker and add 2 drops of phenolphthalein indicator solution until the color is consistent;
[0057] Put the filter membrane together with the insoluble matter into the correspondingly numbered tall weighing bottle, and dry it to constant weight at (110±5)℃ in an oven;
[0058] Use an analytical balance to weigh the constant-weight tall weighing bottle with filter membrane and insoluble matter, and record its mass value as m1;
[0059] The loss on ignition of soda ash is a known value, represented by ω0.
[0060] 3.3 Calculation of the determination results of soda ash samples:
[0061] The mass fraction of water-insoluble matter is calculated in ω, and the value is expressed in %, calculated by the following formula:
[0062] ω= 100
[0063] Where:
[0064] m 1 —The mass value of the water-insoluble matter, the microporous filter membrane and the tall bottle after constant weight, in grams (g);
[0065] m 2 —The mass value of the microporous filter membrane and the tall bottle after constant weight, in grams (g)
[0066] m—The mass value of the sample, in grams (g)
[0067] ω 0 —The mass fraction value of the loss on ignition in the sample, expressed in%
[0068] Take the arithmetic average of the parallel determination results as the determination result. The absolute difference of the parallel determination results: no more than 0.006% for top-grade products and first-class products, and no more than 0.008% for qualified products.
[0069] 4. Matters needing attention:
[0070] 4.1 Since moisture absorption will cause quality changes, the filter membrane must be covered with the lid of the tall bottle immediately after being taken out of the oven, and placed in the desiccator. Remember that the constant weight of the filter membrane and the constant weight of the filter membrane with the sample are twice The time for the membrane to cool to room temperature remains the same to reduce accidental errors.
[0071] 4.2 The surface smoothness of PTFE material is not good, and the seal with the solvent filter is not tight when filtering distilled water and samples. Therefore, it is necessary to control the flow rate of the poured liquid, not too fast to prevent leakage.
[0072] 4.3 After filtration, rinse the edge of the solvent filter that is in contact with the filter membrane.
[0073] 5. Effect inspection:
[0074] Comparison with GB/T210.2-2004 Industrial Sodium Carbonate and its Test Method Part 2: Arbitration Method in Industrial Sodium Carbonate Test Method—Analysis Results and Time of Pickling Asbestos Method, the list is as follows:
[0075] Table 2: The arbitration method in the industrial sodium carbonate test method—the comparison table of the analysis results and time of the pickling asbestos method.
[0076]
[0077] It can be seen from Table 2 that the absolute difference between the measurement results of the microporous membrane and the pickling asbestos method is far less than the 0.006% required in Part 2 of GB/T210.2-2004 "Industrial Sodium Carbonate and Its Test Methods". The accuracy is high, and the analysis time is shortened from 26h for pickling asbestos method to less than 4h.
[0078] The foregoing descriptions are only preferred and feasible embodiments of the present invention, and are not therefore limited to the scope of rights of the present invention. All equivalent structural changes made using the content of the description of the present invention are included in the scope of rights of the present invention.
