## 3 Materials and Methods
### Adsorption Studies  
Batch adsorption studies were performed by mixing 20 mg of MMIPs with 5 mL of OFL solution at various concentrations ranging from 20 to 1000 mg. L\({}^{-1}\) in a 50 mL conical flask. Both 0.1 mol. L\({}^{-1}\) HCl and 0.1 mol.L\({}^{-1}\) NaOH solutions were used to adjust the pH to 5. The solution was shaken at 150 rpm in a thermostatic shaker for 30 min. After magnetic separation, the OFL concentration in the supernatant was measured by HPLC. All tests were conducted in triplicate. Using the OFL concentrations before and after adsorption, the equilibrium adsorption capacity of OFL was calculated using the following equation [36; 37]:  
\[\mathrm{q}=\frac{(\mathrm{C}_{0}-\mathrm{C}_{\mathrm{e}})\mathrm{V}}{\mathrm{ m}} \tag{1}\]  
where \(\mathrm{q}\) (\(\mathrm{\mu g\cdot g^{-1}}\)) is the adsorption capacity of OFL bound on MMIPs, \(\mathrm{C}_{0}\) and \(\mathrm{C}_{\mathrm{e}}\) are the initial solution concentration and equilibrium concentration of OFL (\(\mathrm{\mu g\cdot mL^{-1}}\)), respectively, \(\mathrm{V}\) is the volume of the solution (mL), and \(\mathrm{m}\) is the adsorbent dosage (mg).  
To further analyze the adsorption data, the Langmuir equation and Freundlich model were used to estimate the binding properties of the MMIPs. The Langmuir equation is expressed as follows [38]:  
\[\frac{\mathrm{C}_{\mathrm{e}}}{\mathrm{q}}=\frac{\mathrm{C}_{\mathrm{e}}}{ \mathrm{q}_{\mathrm{m}}}+\frac{1}{\mathrm{q}_{\mathrm{m}}\mathrm{K}_{\mathrm{L}}} \tag{2}\]  
where \(\mathrm{q}\) is the adsorption capacity at equilibrium (mg\(\cdot\mathrm{g^{-1}}\)), \(\mathrm{q}_{\mathrm{m}}\) is the apparent maximum adsorption capacity (mg\(\cdot\mathrm{g^{-1}}\)), \(\mathrm{C}_{\mathrm{e}}\) is the equilibrium concentration of OFL (mg\(\cdot\mathrm{L^{-1}}\)), and \(\mathrm{K}_{\mathrm{L}}\) is the Langmuir constant related to the affinity of the adsorption sites (L\(\cdot\mathrm{mg^{-1}}\)). The values of \(\mathrm{K}_{\mathrm{L}}\) and \(\mathrm{q}_{\mathrm{m}}\) can be calculated from the slope and intercept of the linear regression fit for a plot of 1/q versus 1/\(\mathrm{C}_{\mathrm{e}}\).  
The Freundlich isotherm is represented as follows [39; 40]:  
\[\mathrm{lgq}=\mathrm{lgK}_{\mathrm{F}}+\frac{\mathrm{lgC}_{\mathrm{e}}}{\mathrm{ n}} \tag{3}\]  
where n and \(\mathrm{K}_{\mathrm{F}}\) are Freundlich constants that are related to the adsorption favorability and adsorption capacity, respectively.  
The adsorption kinetic data were analyzed using a pseudo-first-order Equation (4) and a pseudo-second-order Equation (5), as follows [41]:  
\[\ln(q_{e}-q_{t})=lnq_{e}-k_{1}t \tag{4}\]  
\[\frac{t}{q_{t}}=\frac{1}{k_{2}q_{e,c}}^{2}+\frac{t}{q_{e,c}} \tag{5}\]  
where \(q_{e}\) and \(q_{t}\) are the adsorption amounts (mg.g\({}^{-1}\)) of OFL bound to the MMIPs at equilibrium and at any time t, respectively, and \(k_{1}\) (min\({}^{-1}\)) and \(k_{2}\) (g.mg\({}^{-1}\cdot\)min\({}^{-1}\)) are the pseudo-first-order rate constant and pseudo-second-order rate constant at equilibrium, respectively.  
After adsorption, the MMIPs loaded with OFL were eluted with 1%, 2%, 3%, 5%, 8%, 10%, 15%, or 20% methanol-acetic acid (\(\
u/v\)). The supernatants were evaporated to dryness under a stream of nitrogen, and the residues were redissolved in the mobile phase. Then, 20 \(\mu\)L of the resulting solution was used for HPLC analysis. After elution, the MMIPs were dried for 32 h in a freeze dryer at -40 \({}^{\circ}\)C and reused for OFL adsorption.