# Yeast-Based Magnetic Biocomposite for Efficient Sorption of Organic Pollutants
## 3 Result and Discussion  
### Characterizations of Materials  
The first stage was to conduct a thermal analysis of the material in an atmosphere of an inert gas such as argon. Pyrolysis is a process of thermochemical conversion of biomass through thermal movement into volatile substances, water vapor, and a mixture of liquid compounds in a neutral environment [33]. During the pyrolysis of dried lotus pods, the products are liquid, synthesis gas, and solid. During the pyrolysis process, natural polymer components found in biomass decompose into volatile vapors containing oxygen and hydrogen. These vapors can be condensed to obtain bio-oil, which can be used as an energy source used in the initial stage of pyrolysis, such as material drying or carbonization [34]. Carbonization speeds up the elimination of polar functional groups and reorganizes organic structures with ring or linear configurations into polycondensed aromatic sheets. This process of carbonization necessitates low oxygen levels to minimize the production of CO\({}_{2}\) and NOx [35]. Studying the results of the thermal analysis (Figure 2), the temperature for the pyrolysis process was selected. The thermal analysis was carried out in the temperature between 30-1000 \({}^{\circ}\)C with a temperature increase of 20 \({}^{\circ}\)C/min. Lotus pods and other biomass consist mainly of hemicellulose, cellulose, and lignin, the pyrolytic mass loss of which occurs mainly in the temperature ranges of 220-315 \({}^{\circ}\)C, 315-400 \({}^{\circ}\)C, and 160-900 \({}^{\circ}\)C, respectively [36]. The analysis shows that the lotus pods pyrolysis process includes three stages, the first below 150 \({}^{\circ}\)C, the second between 150 and 500 \({}^{\circ}\)C, and the third above 500 \({}^{\circ}\)C. In the temperature range of up to 150 \({}^{\circ}\)C, there was a drying area (weight loss of 7.12%) and the main biomass degradation process took place in the temperature range of about 200 \({}^{\circ}\)C to about 500 \({}^{\circ}\)C. At this stage, the highest weight loss is observed, amounting to 41.5%, which is caused by the pyrolysis of lignocellulosic. Additionally, both hemicellulose and cellulose can be completely degraded, while only part of lignin can undergo this process due to its limited thermal reactivity. In the third stage, a slowdown in the mass loss rate is observed (mass loss 16.35%) and the mass loss effect may be related to lignin pyrolysis, self-gasification, secondary reactions, or something unknown [37; 38]. The temperature of 500 \({}^{\circ}\)C was chosen as the temperature for the pyrolysis process, which corresponds to the temperature at which the material has already charred and the mass loss that occurs allows for obtaining the appropriate amount of material for testing. The surface morphology of the obtained YL-M-L-AC biocomposite after drying to dry mass before and after the sorption process was determined using SEM-EDX analysis. Figure 3 shows analysis along with the analysis of the surface composition. YL-M-L-AC itself has rough surfaces that provide high porosity and a large adsorption surface [39]. Mapping of the biocomposite also shows a uniform distribution of Fe\({}_{3}\)O\({}_{4}\) particles, confirming the successful deposition of Fe\({}_{3}\)O\({}_{4}\) particles on its surface. Additionally, the analysis shows that magnetite particles partially agglomerate as a result of magnetic interaction with each other. This arrangement of particles may result in crystallites without pores [40]. Micrographs show fine pores, which indicate that the porosity of the biocomposite is maintained. The SEM image after dye sorption shows morphological changes due to the adsorption of the MB dye by YL-M-L-AC (Figure 3B). The pores were occupied by MB molecules and the initial roughness disappeared.