2.4.1. Adsorption Isotherm of Chrysin on Bi-MIPs, Bi-NIPs, Si-MIPs and Si-NIPs

To estimate the adsorption properties of Bi-MIPs, the Bi-MIPs were weighed (0.02 ± 0.0002 g) with an analytical balance and placed into a round of 50 mL conical flasks, and added into 20 mL of a chrysin methanol solution with different concentrations (0.2 mg/mL–1.4 mg/mL). The adsorption process of the Bi-MIPs was carried out for 5 h in an 80 rpm constant temperature oscillator at 25 ◦C. After the sorption experiments, the Bi-MIPs were separated from the mixed solution by a centrifuge and the concentration in the supernatant was obtained for UV-vis absorbance. The chrysin adsorption amount of Bi-MIPs was determined based on the following Equation (1):

$$\mathbf{Q\_e} = \frac{(\mathbf{C\_0} - \mathbf{C\_e}) \times \mathbf{V}}{\mathbf{W}} \tag{1}$$

where C0 (mg/mL) represents the initial concentration of chrysin in the solution, Ce (mg/mL) represents the equilibrium concentration of chrysin after adsorption, V (mL) represents the volume of the adsorbed chrysin solution and W (g) represents the mass of polymers in the adsorbed chrysin solution.

At the same time, to evaluate the adsorption capacity of Bi-NIPs, Si-MIPs and Si-MIPs. A total of 20 mg of Bi-NIPs, Si-MIPs or Si-MIPs was placed into a round of 50 mL conical flasks and added into 20 mL of chrysin solution with different concentrations (0.2 mg/mL– 1.4 mg/mL). Under the same operating conditions of Bi-MIPs, the concentration of chrysin in the supernatant was analyzed using UV-vis absorbance. The equilibrium adsorption capacity was calculated using Equation (1).

#### 2.4.2. Adsorption Kinetics

To estimate the adsorption kinetics of Bi-MIPs on chrysin, the influence of the adsorption properties over time was studied. The Bi-MIPs were weighed (0.02 ± 0.0002 g) with an analytical balance and placed into a round of 50 mL conical flasks. After adding 20 mL of chrysin methanol solution, the Bi-MIPs were used to adsorb chrysin (1 mg/mL) in an

80 rpm constant temperature oscillator at 25 ◦C. Samples of 0.05 mL volume were taken at 15, 30, 45, 60, 75, 90, 105,120, 150, 180, 210, 240 and 300 min, and the concentration in the supernatant was obtained for UV-vis absorbance. The chrysin equilibrium adsorption amount of the Bi-MIPs was obtained based on the following Equation (2):

$$\mathbf{Q\_t} = \frac{(\mathbf{C\_0} - \mathbf{C\_t})}{\mathbf{W}} \times \mathbf{V} \tag{2}$$

where C0 (mg/mL) represents the initial concentration of chrysin in the solution, Ct (mg/mL) represents the concentration of chrysin solution at time t (min), V (mL) represents the volume of adsorbed chrysin solution and W (g) represents the mass of polymers in the adsorbed chrysin solution.

At the same time, to evaluate the adsorption capacity of Bi-NIPs, Si-MIPs and Si-MIPs. Under the same operating conditions of the Bi-MIPs, the concentration of chrysin in the supernatant was analyzed using UV-vis absorbance. The equilibrium adsorption capacity was calculated using Equation (2).
