GB/T 15818-2018Test method for the biodegradability of surfactants (English PDF)

1 Scope

China's national test method for the primary biodegradability of surfactants - how far a surfactant is broken down by the micro-organisms it meets after it goes down the drain. It specifies the test methods for primary biodegradability and applies to anionic surfactants carrying sulfonate and sulfate groups, to polyoxyethylene surfactants with a single chain of 3 to 40 EO units and two-, three- and four-chain types with 6 to 60 EO units in total, to alkyl glycosides, to cationic and amphoteric surfactants, to fatty acid surfactants, to high-foaming surfactants and to surfactants that substantially lower the surface tension of water. It applies equally to the determination of those surfactants in detergents. Surfactants reach surface water in enormous quantity and are the component of a detergent that does the environmental damage if it persists: a surfactant that survives treatment foams in the receiving water, is toxic to fish at low concentration through its action on gill membranes, and accumulates. The test is therefore a condition of sale, and the number it produces has to be reproducible between the manufacturer and the regulator. The method is a die-away test: the surfactant is put into a synthetic sewage inoculated with activated sludge, held under defined aerobic conditions, and the residual surfactant is measured over time by the analytical method appropriate to its class - two-phase titration for the anionic and cationic types, and the specific methods referenced for the others. Primary biodegradation is what is measured: the loss of surface-active character, not complete mineralisation to carbon dioxide. That distinction is the reason the standard has to be read carefully, because a substance can pass a primary biodegradability test while leaving a persistent fragment behind. Issued on 28 December 2018 and in force since 1 July 2019, it replaces GB/T 15818-2006.

This standard specifies the test methods for the primary biodegradability of surfactants. This standard is applicable to the determination of anionic surfactants with sulfonic acid groups and sulfuric acid groups. The single-chain EO addition number of polyoxyethylene groups is 3~40 and two, three, four chain total EO adduct number 6~60 surfactants, alkyl glycoside surfactants, cationic and zwitterionic table Surfactants, fatty acid surfactants, surfactants with richer foam and surfactants that can effectively reduce the surface tension of water the biodegradability of the agent. This standard also applies to the determination of the degree of biodegradation of the above-mentioned surfactants in detergents.

2 Normative references

The following documents are essential for the application of this document. For dated references, only the dated version applies to this article pieces. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 5173 Determination of the content of anionic active substances in surfactant detergents by direct two-phase titration

GB/T 5174 Determination of cationic active content of surfactant detergents by direct two-phase titration

GB/T 6682 Analysis Laboratory Water Specifications and Test Methods

GB/T 13173 Surfactant Detergent Test Method

GB/T 19464 Alkyl glycosides QB/T 2344 Amphoteric surfactant fatty alkyl dimethyl betaine Preparation of test solutions for titration analysis (volumetric analysis) of QB/T 2739 commonly used test methods for washing products

3 Terms and Definitions

The following terms and definitions apply to this document.

3.1 biodegradability Molecular degradation of organic matter that occurs under the complex activities of living organisms.

3.2 The original parent molecular properties disappeared to a certain extent.

3.3 Disappearance time DT-90 disappeartime(DT-90) The time it takes for the biodegradability of the surfactant to reach 90% of the initial concentration.

4 Principles

The activated sludge that has been cultured and acclimated as a surfactant sample is used as a biodegradable source, added to the test sample for shaking culture, and the culture period is determined. The reduction of surfactant during the period was used to obtain the DT-90 of the sample and the degree of biodegradation at the specified time.

5 Reagents

Unless otherwise stated, only the reagents confirmed as analytical grade and the tertiary water specified in GB/T 6682 are used in the analysis.

5.1 Ammonium chloride.

5.2 Dipotassium hydrogen phosphate.

5.3 Potassium dihydrogen phosphate.

5.4 Disodium hydrogen phosphate.

5.5 Magnesium sulfate.

5.6 Potassium chloride.

5.7 Calcium chloride.

5.8 Ferrous sulfate.

5.9 Ferric chloride.

5.10 Yeast extract (biochemical reagent).

5.11 Linear sodium dodecylbenzene sulfonate. the content is more than 95%, and the biodegradability is more than 99%.

5.12 Linear dodecanol polyoxyethylene ether (7EO). the content is more than 98%, and the biodegradability is more than 99%.

5.13 Microbial source. activated sludge is taken from the sewage treatment plant that treats civil wastewater, and the mass concentration of activated sludge suspended matter should be adjusted to 10g/L~20g/L, use within 5h after sampling.

6 Instruments

Common laboratory instruments and the following.

6.1 Shaking culture flask. capacity 1000mL, sterilize in oven at 170°C for 1h~2h. Tighten with a silicone stopper, the silicone stopper is sealed with pressure steam Sterilizer for sterilization.

6.2 Shaking culture machine. the amplitude is more than 20mm, the oscillation frequency is adjustable from 40 times/min to 300 times/min, the constant temperature range is 5°C to 50°C, and the temperature Control accuracy ± 2 °C. The shaking culture machine should be able to record and monitor the temperature and rotation speed during operation in real time, and confirm the temperature of the whole test cycle. The degree and rotation speed meet the requirements of 7.7.RHZJ-I intelligent biodegradable incubator 1) can meet this requirement. 1) RHZJ-I intelligent biodegradable incubator is an example of a suitable commercial product. This information is given for the convenience of users of this standard and is not Indicates approval for this product.

6.3 Pressure steam sterilizer. rated temperature 126°C, rated pressure 0.14MPa.

Appendix A

(normative appendix) Determination of anionic surfactants

---methylene blue method A.1 Principle The complex formed by anionic surfactant and methylene blue was extracted with chloroform, and then the anionic surface was determined by spectrophotometry Active agent content. A.2 Scope of application This method is suitable for anionic surfactants containing sulfonic acid groups and sulfuric acid groups. A.3 Reagents Unless otherwise stated, only the reagents confirmed as analytical grade and the tertiary water specified in GB/T 6682 are used in the analysis. A.3.1 Standard solution of anionic surfactant. determine the purity according to GB/T 5173.Weigh 1g equivalent to 100% of the reference substance (5.11) (accurate to 0.001g), dissolve in water, transfer and dilute to 1000mL, and mix well. The mass concentration of anionic surfactant in this solution is 1g/L. A.3.2 Anionic surfactant use solution. Pipette 10.0mL of anionic surfactant standard solution, put it in a 1000mL volumetric flask , add water to volume, and mix well, then the mass concentration of the anionic surfactant in the solution is

0.01 mg/mL. A.3.3 Sulfuric acid. A.3.4 Sodium dihydrogen phosphate washing solution. Dissolve 50 g of sodium dihydrogen phosphate in water, add

6.8 mL of sulfuric acid (A.3.3), and dilute to 1000 mL. A.3.5 Methylene blue solution. Weigh

0.1 g of methylene blue, dissolve it with water and dilute to 100 mL, pipette 30 mL of this solution, use dihydrogen phosphate Dilute the sodium washing solution (A.3.4) to 1000mL. A.3.6 Trichloromethane. A.4 Instruments Commonly used laboratory instruments and spectrophotometers, wavelength 360nm ~ 800nm. A.5 Operation steps A.5.1 Drawing of working curve Accurately pipette 0 mL of the anionic surfactant solution (A.3.2) with a mass concentration of

0.01 mg/mL (as a blank reference solution), 3.0mL, 6.0mL, 9.0mL, 12.0mL, 15.0mL, respectively, in a 250mL separatory funnel, add water to make the total volume 100mL. add Add 25 mL of methylene blue solution (A.3.5), mix well, add 15 mL of chloroform (A.3.6), shake for 30 s, let stand for stratification; if the water layer is blue If the color fades, add 10 mL of methylene blue solution, shake for 30 s, and let it stand for 10 min. Put the chloroform layer into another 250mL separatory funnel (do not bring out the interface flocs with chloroform), and repeat the extraction to three times. The methyl chloride layer was colorless. Add 50 mL of sodium dihydrogen phosphate solution (A.3.4) to the combined chloroform extracts, shake for 30s, let stand for 10min, and add chloroform Put the layer into a 100mL volumetric flask, add 5mL of chloroform into a separatory funnel, and repeat the extraction until the chloroform layer is colorless, and all the chloroform layer is colorless. The methane layer was placed in a 100mL volumetric flask, and the volume was adjusted with chloroform, and mixed. Use a spectrophotometer at a wavelength of 650nm and a 10mm colorimetric cell, and use a blank reference solution as a reference to determine the net absorbance value of the test solution. in table The mass (mg) of the surfactant is the abscissa, and the net absorbance is the ordinate. The working curve is drawn or calculated by the univariate regression equation y=a bx. A.5.2 Determination of surfactant content in degradation test solution Accurately pipette an appropriate volume (the initial sampling volume for degradation is 2mL~5mL, and the sampling volume during the degradation process can be appropriately increased to 50mL) for degradation Add the solution (7.7) to a 250mL separatory funnel, add water to 100mL, and then add 25mL of methylene blue solution according to A.5.1 "in the following steps, and then use Trichloromethane to volume, mixing" procedure. Measure the blank test solution (7.3.3) in the same procedure. Use a spectrophotometer in a colorimetric cell with a wavelength of 650 nm and 10 mm, and use the blank test solution as a reference to determine the net absorbance value of the test solution. The light value and the working curve or y=a bx are calculated to obtain the mass concentration of the surfactant, expressed in mg/L. A.6 Result calculation The mass concentration rho of anionic surfactant is calculated according to formula (A.1). rho= (A.1) where. rho

--- mass concentration of anionic surfactant, in milligrams per liter (mg/L); m

---The content of anionic surfactant in the test solution obtained from the working curve or calculated, in milligrams (mg); V

--- Sampling volume, the unit is liter (L).

Appendix B

(normative appendix) Determination of ethoxylated surfactants

---cobalt thiocyanate method B.1 Principle The complex formed by ethoxylated surfactant and cobalt thiocyanate was extracted with chloroform, and then the surface activity was determined by spectrophotometry. Sexual agent content. B.2 Scope of application This method is suitable for the surface activity of polyoxyethylene type single-chain EO adduct number 3~40, double-chain, triple-chain, quadruple-chain total EO adduct number 6~60 and surfactants such as polyethylene glycol (molar mass 300g/moL~1000g/moL) and polyether. B.3 Reagents Unless otherwise stated, only the reagents confirmed as analytical grade and the tertiary water specified in GB/T 6682 are used in the analysis. B.3.1 Standard solution of ethoxylated surfactant. determine the purity according to GB/T 13173.Weigh out the reference material equivalent to 100% (5.12) 1g (accurate to 0.001g), dissolve in water, transfer and dilute to 1000mL, and mix well. The mass concentration of ethoxylated surfactant in this solution is 1g/L. B.3.2 Use solution of ethoxylate surfactant. Pipette 25.0mL of ethoxylate surfactant standard solution into a 250mL volumetric flask , add water to volume, and mix well, then the mass concentration of surfactant in the solution is 0.1mg/mL. B.3.3 Ammonium thiocyanate. B.3.4 Cobalt nitrate (hexahydrate). B.3.5 Benzene. B.3.6 Cobalt ammonium thiocyanate solution. Dissolve 620g ammonium thiocyanate (B.3.3) and 280g cobalt nitrate (B.3.4) in a small amount of water, and mix them evenly Diluted to 1000mL, and then extracted twice with 30mL of benzene for later use. B.3.7 Sodium chloride. B.3.8 Trichloromethane. B.4 Instruments Commonly used laboratory equipment and spectrophotometer, wavelength.200nm ~ 800nm. B.5 Operation steps B.5.1 Drawing of working curve Accurately pipette 0 mL of the ethoxylated surfactant solution (B.3.2) with a mass concentration of

0.1 mg/mL (as a blank reference solution), 5.0mL, 10.0mL, 20.0mL, 25.0mL, 30.0mL, 35.0mL, respectively, in a 250mL separatory funnel, add water to make the total volume 100mL, add 15mL of cobalt ammonium thiocyanate solution (B.3.6), mix slightly, add 35.5g sodium chloride (B.3.7), shake well for 1min, and let stand After 15min, add 15mL of chloroform (B.3.8), shake for 1min, and put the chloroform layer into a 50mL volumetric flask after standing for 15min (Do not bring out the interface flocs with the chloroform layer), repeat the extraction twice, make up to volume with chloroform, and mix. Use an ultraviolet spectrophotometer in a quartz cell with a wavelength of 319 nm and 10 mm, and use a blank reference solution as a reference to determine the net absorbance of the test solution. Take the surfactant mass (mg) as the abscissa and the net absorbance value as the ordinate, draw the working curve or use the univariate regression equation y=a bx calculate. B.5.2 Determination of surfactant content in degradation test solution Accurately pipette 50.0mL of the degradation test solution (7.7) into a 250mL separatory funnel, add 50mL of water (when the degradation is near the end point, pipette the degradation test solution) The amount should be increased to 100mL, no more water), the following steps are according to B.5.1 "Add 15mL of cobalt ammonium thiocyanate solution with chloroform Continue to mix and mix" procedure. Measure the blank test solution (7.3.3) in the same procedure. Use an ultraviolet spectrophotometer at a wavelength of 319 nm and a 10 mm colorimetric cell, and use the blank test solution as a reference to determine the net absorbance of the test solution. Depend on The net absorbance value and the working curve or y=a bx are calculated to obtain the surfactant mass concentration, expressed in mg/L. B.6 Result calculation The mass concentration rho of ethoxylated surfactant is calculated according to formula (B.1). rho= (B.1) where. rho

--- mass concentration of ethoxylated surfactant, in milligrams per liter (mg/L); m

---The content of ethoxylated surfactant in the test solution obtained from the working curve or calculated, in milligrams (mg); V

--- Sampling volume, the unit is liter (L).

Note. The presence of anionic surfactants, cationic surfactants, amphoteric surfactants and polyethylene glycol will affect the accuracy of the analysis results. separated and removed. See GB/T 5560 for the separation of polyethylene glycol; see GB/T 13173 for the separation of other surfactants.

Appendix C

(normative appendix) Determination of cationic and zwitterionic surfactants

---Golden Orange-2 method C.1 General pH=1 buffer system is suitable for zwitterionic surfactants, cationic surfactants and their mixtures; pH=5 buffer system Suitable for cationic surfactants. When the sample is a mixture of cationic and zwitterionic surfactants, cations are obtained at pH=

5 The absorbance value of the surfactant, the total absorbance value of the cationic and zwitterionic surfactants is obtained at pH=1, the difference between the two is the amphoteric Ionic surfactant absorbance. C.2 Determination of cationic surfactants C.2.1 Principle The complexes formed by cationic surfactants and golden orange-2 under pH=5 buffer conditions were extracted with chloroform, and then subjected to spectrophotometry. Determination of cationic surfactant content by the method. C.2.2 Scope of application This method is applicable to cationic surfactants. C.2.3 Reagents Unless otherwise stated, only the reagents confirmed as analytical grade and the tertiary water specified in GB/T 6682 are used in the analysis. C.2.3.1 Standard solution of cationic surfactant. determine the purity according to GB/T 5174.Weigh equivalent to 100% cationic surface activity 1.0g (accurate to 0.001g), dissolve in water, transfer and dilute to 1000mL, mix well, the mass concentration of cationic surfactant in this solution is 1g/L. C.2.3.2 Use solution of cationic surfactant. Pipette 10.0mL of cationic surfactant standard solution into a 1000mL volumetric flask , add water to volume and mix well, then the mass concentration of surfactant in the solution is 0.01mg/mL. C.2.3.3 Golden Orange-2, weigh

0.1 g of Golden Orange-2 and dissolve it in 100 mL of water, and mix well. C.2.3.4 Acetic acid, 0.2mol/L acetic acid solution. C.2.3.5 Sodium acetate, 0.2mol/L sodium acetate solution. C.2.3.6 Buffer solution, pH=5, measure 59mL of 0.2mol/L acetic acid solution and 141mL of 0.2mol/L sodium acetate solution and mix well spare. C.2.3.7 Trichloromethane. C.2.4 Instruments Commonly used laboratory instruments and spectrophotometers, wavelength 360nm ~ 800nm. C.2.5 Operation steps C.2.5.1 Drawing of working curve Accurately pipette 0mL of the cationic surfactant solution (C.2.3.2) with a mass concentration of 0.01mg/mL (as a blank reference solution), 5.0mL, 10.0mL, 15.0mL, 20.0mL, 25.0mL, 30.0mL, and 35.0mL were placed in a 250mL separatory funnel, respectively, and water was added to make the When the volume reaches 100mL, add 10mL of pH=5 buffer solution (C.2.3.6), 3mL of golden orange-2 solution (C.2.3.3), and add chloroform after mixing. 10mL, shake for 30s, put it into a 50mL volumetric flask after standing for 10min (do not take the flocs out with chloroform), repeat the extraction, until the To chloroform colorless, dilute to volume with chloroform, and mix. Use a spectrophotometer at a wavelength of 485nm, a 10mm colorimetric cell, and use a blank reference solution as a reference to determine the net absorbance value of the test solution. in table The mass (mg) of the surfactant is the abscissa, and the net absorbance is the ordinate. The working curve is drawn or calculated by the univariate regression equation y=a bx. C.2.5.2 Determination of surfactant content in degradation test solution Accurately pipette 10mL of the degradation solution (7.7) into a 250mL separatory funnel, and add water according to C.2.5.1 in the following steps to make the volume reach 100mL Dilute to volume with chloroform and mix. Measure the blank test solution (7.3.3) in the same procedure. Use a spectrophotometer at a wavelength of 485nm and a 10mm colorimetric cell, and use the blank test solution as a reference to determine the net absorbance value of the test solution. by net The absorbance value and the working curve or y=a bx were calculated to obtain the mass concentration of the surfactant, expressed in mg/L. C.2.6 Result calculation The mass concentration rho of the cationic surfactant is calculated according to the formula (C.1). rho= (C.1) where. rho

---mass concentration of cationic surfactant, in milligrams per liter (mg/L); m

---The content of cationic surfactant in the test solution obtained from the working curve or calculated, in milligrams (mg); V

--- Sampling volume, the unit is liter (L). C.3 Determination of zwitterionic surfactants C.3.1 Principle The complexes formed by zwitterionic surfactants and golden orange-2 under pH=1 buffer conditions were extracted with chloroform, followed by spectrophotometry. Photometric determination of zwitterionic surfactant content. C.3.2 Scope of application This method is applicable to zwitterionic surfactants, as well as cationic surfactants and their mixtures. C.3.3 Reagents Unless otherwise stated, only the reagents confirmed as analytical grade and the tertiary water specified in GB/T 6682 are used in the analysis. C.3.3.1 Amphoteric surfactant standard solution. determine the purity according to QB/T 2344.Accurately weighs the equivalent of 100% amphoteric surfactant Dosage 1.0g (accurate to 0.001g), dissolve in water, transfer and dilute to 1000mL, and mix well. Amphoteric surfactant mass concentration in this solution is 1g/L. C.3.3.2 Amphoteric surfactant use solution. Pipette 10.0mL of amphoteric surfactant standard solution into a 1000mL volumetric flask, add Dilute to volume with water and mix well, then the mass concentration of surfactant in the solution is 0.01mg/mL. C.3.3.3 Golden Orange-2, weigh

0.1 g of Golden Orange-2 and dissolve it in 100 mL of water, and mix well. C.3.3.4 Hydrochloric acid, 0.2mol/L hydrochloric acid solution. C.3.3.5 Potassium chloride, 0.2mol/L potassium chloride solution. C.3.3.6 Buffer solution, pH=1, measure 97mL of 0.2mol/L hydrochloric acid solution (C.3.3.4), and 0.2mol/L potassium chloride solution (C.3.3.5)