Basic yellow 40

Guidelines (The following is our recommended protocol. This protocol is for reference only and should be modified according to your specific needs).

2. Working solution preparation
2.1 Diluent: water; Basic yellow 40 (BY40; also known as Maxilon Flavine 10GFF; CAS 12221-32-5; molecular formula C20H20ClN3O2; molecular weight 369.84 g/mol) is a water-soluble bright yellow powder.
2.2 Working concentration: prepare BY40 solutions at initial concentrations of 1 to 600 mg L−1, pH = 9, for adsorption tests. For surfactant tests, prepare a 10 mg L−1 BY40 solution.
2.3 Note: adjust the working solution concentration as needed; prepare fresh before use.

3. Staining procedure
3.1 Sample type: use polymeric adsorbent microspheres Mic1, Mic1/AMS, Mic2, or Mic2/AMS; weigh 0.05 g of adsorbent into an Erlenmeyer flask[2].
3.2 Incubation conditions: add 20 mL of BY40 solution at the selected working concentration to the Erlenmeyer flask, place the flask in a mechanical shaker set at an amplitude of 8 and 150 cycles per minute, and shake at room temperature for 24 h. For surfactant tests, use 10 mg L⁻¹ BY40 with 0.1-0.5 g L⁻¹ CTAB or SDS, with a contact time of 15 min, then separate the solution by filtration.

4. Controls
4.1 Blank: determine the BY40 concentration against a blank at 431 nm.
4.2 Surfactant-free control: compare adsorption in the presence of CTAB or SDS with BY40 adsorption without these additives.

5. Detection and analysis
5.1 Instrument type: use a single-beam UV-visible spectrophotometer.
5.2 Wavelength setting: measure absorbance at the maximum wavelength of 431 nm.
5.3 Calibration: determine the BY40 concentration from a calibration curve established in the 0.1-20 mg L⁻¹ range with a coefficient of determination of 0.998, using a 1 cm quartz cuvette, a slit width of 1 mm, and an integration time of 1 s.
5.4 Result analysis: calculate the adsorption capacity q_e using q_e = (C0 − Ce) V/m, where C0 and Ce are the initial and equilibrium concentrations of BY40 (mg L⁻¹), respectively, V is the volume of BY40 solution (L), and m is the mass of adsorbent (g). For surfactant tests, calculate q_t using q_t = (C0 − Ct) V/m, where Ct is the BY40 concentration after a specific adsorption time t. Equilibrium data can be fitted to isotherm models such as Freundlich, Langmuir, Temkin, and Dubinin-Radushkevich. The adsorption of BY40 on the studied adsorbents follows the Freundlich isotherm model, and a 1/n value below 1 indicates favorable adsorption.