# Yeast-Based Magnetic Biocomposite for Efficient Sorption of Organic Pollutants
## 3 Result and Discussion
### Methylene Blue Adsorption
#### 3.2.2 Equilibrium Studies  
Equilibrium data are an important factor to prepare the adsorption systems [72]. Equilibrium studies often use multiple isotherms, but for this experiment, the main four were used (Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich). Figure 8 shows the plots of the studied isotherms, and the calculated parameters are shown in Table 2. As noted in Table 3, the three studied isotherms are characterized by a high fit (R\({}^{2}\) > 0.978 and ARE < 9.76), while the Freundlich isotherm favors MB uptake by YL-M-L-AC (R\({}^{2}\) = 0.996, ARE = 3.41) more than other models. The values of the correlation coefficient and the average relative error show that the experimental data fit the isotherm model. \begin{table}
\begin{tabular}{l c c} \hline \hline
**adsorbent** & **q\({}_{e}\) [mg/g]** & **Reference** \\ \hline Alginate/polyvinyl alcohol–kaolin composite & 30.8 & [62] \\ \hline SA/zeolite/Fe\({}_{3}\)O\({}_{4}\) composite & 181.8 & [63] \\ \hline Sugarcane bagasse biochar and alginate composite & 30.1 & [64] \\ \hline Starch–humic acid composite hydrogel beads & 110.0 & [65] \\ \hline Magnetic Fe\({}_{3}\)O\({}_{4}\)-nanoparticle-loaded guava leaves powder & 136.7 & [66] \\ impregnated into calcium alginate hydrogel beads & 12.5 & [67] \\ \hline Alginate/Clin/Fe\({}_{3}\)O\({}_{4}\) nanocomposite bead & 22.8 & [68] \\ \hline Magnetic alginate beads & 106.4 & [69] \\ \hline Graphene oxide–montmorillonite/sodium alginate (GO–MMT/SA) aerogel beads & 150.7 & [70] \\ \hline MXene/sodium alginate gel beads & 92.2 & [71] \\ \hline YL-M-L-AC & 32.1 & This study \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of investigations involving alginate and its composites in the removal of MB. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Isotherm Model** & \multicolumn{4}{c}{**Parameters**} \\ \hline \multirow{2}{*}{[PERSON]} & ARE [\%] & R\({}^{2}\) & q\({}_{m}\) [mg/g] & K\({}_{L}\) [dm\({}^{3}\)/mg] \\ \cline{2-5}  & 7.47 & 0.9889 & 47.94 & 0.021 \\ \hline \multirow{3}{*}{[PERSON]} & ARE [\%] & R\({}^{2}\) & K\({}_{F}\) & 1/n \\ \cline{2-5}  & 3.41 & 0.9959 & 2.865 & 0.538 \\ \hline \multirow{3}{*}{Temkin} & ARE [\%] & R\({}^{2}\) & K\({}_{T}\) [dm\({}^{3}\)/g] & B [k]/mol] \\ \cline{2-5}  & 9.76 & 0.9777 & 0.256 & 9.643 \\ \hline \multirow{3}{*}{D–R} & ARE [\%] & R\({}^{2}\) & K\({}_{\rm ad}\) [mol\({}^{2}\)/k\({}^{2}\)] & q\({}_{d}\) [mg/g] \\ \cline{2-5}  & 15.91 & 0.9482 & 0.0069 & 35.18 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Adsorption isotherm parameters for the adsorption of MB onto YL-M-L-AC, t = 24 h, T = 25 \({}^{\circ}\)C.  
The Freundlich isotherm is used to investigate the beneficial effects of the adsorption process. The process is called favorable if the value of n is between 1 and 10, otherwise it is unfavorable. It was found that the value of \(1/n\) of 0.538 for dye adsorption on the biocomposite ranges from 0 to 1, which indicates the desired adsorption process and process heterogeneity, and the value of the K\({}_{\rm F}\) constant is \(\sim\)2.8 (above 1), suggesting the participation of physical sorption in the examined process [60; 73]. The Langmuir adsorption isotherm describes the single-layer adsorption of analytes on a limited number of active sites of sorbents, which can quickly become completely saturated. Additionally, the amount of adsorbed analytes in single-layer adsorption is moderately smaller compared to multilayer adsorption [3]. The high fit to the Langmuir model suggests a uniform distribution of active centers on the YL-M-L-AC surface [74]. The Temkin isotherm model assumes that the heat of adsorption of molecules changes linearly with increasing surface coverage. B represents the constant associated with the heat of adsorption. In exothermic and endothermic adsorption reactions, the value of B is higher or lower than unity [75]. The reported B value of approximately 9.6 kJ/mol indicates that the adsorption of MB onto YL-M-L-AC was an exothermic process.