3.1 Crystallite phase investigation
[Figure-2] illustrates the X-ray obstruction framework of the two specimens that emerged before it. Whereas relatively limited template represents frequent Fe3O4 fragments, the existence of MnO2 in the Fe3O4/MnO2 lattice is recommended by comparative recognisable peaks at 2θ = 27.5 and 2θ = 40.3 in the located in the outer line. This it seems to be due to the influence of the sharp phases. As stated previously, the crystallographic peaks were detected to be mainly correlated to the magnetite cubical symmetric spinel platform's standard template recognisable peak position (JCPDS 01-072-2345). Using the Scherrer equation, we assessed the crystalline structure of Ferrite nanoparticles and acquired 19.64 nm .
3.2 FT IR analysis
[Figure-3] depicts the FTIR spectrum of Fe3O4/MnO2 nanocomposite. The recognizable peak observed of Fe3O4/MnO2 composite particles is located at 647 cm− 1. It's possible that the Fe-O-Mn particles were bind to the monodispersive compared to the feedstock oil. It is noteworthy that a novel peak at 439 cm− 1 originated in the ability to respond of the nanocomposites, suggesting that a new bond was formed between both the core and the shell. The absorption peaks near 3711.9 and 3157 cm− 1 are adaptable oscillating hydroxy peaks on the surface of substrate; they are broader and powerful than that of the Fe3O4 absorption bands. It assumes that the composite particles encompass more hydroxys than Fe3O4, which may increase the activity of MnO2 particles .
3.3 Morphological investigation
[Fig-4 (a)] shows the structural and morphological spectrum of Fe3O4@MnO2 NCs. These SEM images showed granular shapes with no assemblage and un equality of homogeneously Fe3O4@MnO2 NCs. Figures 4 (c) HRTEM shows the surface characteristics of Fe3O4@MnO2 NCs. [Fig-4 (b)] shows that TEM images of Fe3O4@MnO2 NCs indicate rod like spherical in patterns with molecule size varying from 12 to 22 nm. Furthermore, the monocrystalline phase of Fe3O4@MnO2 NCs by co-precipitation strategy was supported by their corresponding SAED examination, as shown in Fig. 4 (d), with recognizable peak (311), (400), (422), (511) and (400) crystallographic patterns recommending cubical symmetric spinel strategy. The HR-TEM illustration also reveals a well inner surface of the ligament, with the d –widths for adjoining interlayer fringes one assessed to be 0.236 nm, that also represents the proportion of the (311) plane cubical symmetric spinel of Fe3O4@MnO2 NCs [16, 14]
3.4 BET isotherm of Fe3O4@MnO2NCs
The N2 adsorption-desorption isotherm models and pore size diffusion of a novel Fe3O4@MnO2 impetus are displayed in Fig. 5 (a & b). Figure 5 (a) illustrates an impressively genuine MnO2@Fe3O4 impetus with a group IV isotherm, which emerges to be a characteristic revealed by hierarchical highly permeable components. The inter - facial state (SBET) was assessed using Brunauer–Emmett–Teller (BET) approach, and the pore diameter correspondence was acquired utilising the Barrett–Joyner–Halenda (BJH) tactic case and even the adsorption isotherm band. Figure 5 (b) demonstrates how the volume immobilized rapidly with increasing comparative imperative attributes for all isotherms depending on the volume required to fill of mesopores in Fe3O4 screenplay. The porosity and surface province of MnO2@Fe3O4 and the permeability length across were characterised to be 13.19 m2/g and 0.059 cm3/g, respectively 
3.5 EDX spectrum and Elemental mapping Analysis
Elemental analysis of Fe3O4@MnO2 NCs photo detectors demonstrated that certain components, chiefly iron, oxygen, and Mn were generally provided in the hybrid [email protected] nanocomposite. Moreover, the EDX template of Fe3O4@MnO2 NCs reported the existence of all component parts including such Fe, O, and Mn were shown in Fig – 6 
3.6 AFM analysis
The AFM is a type of electron microscopy that is being used to detect factors like length. In tapping phase, an AFM image of Fe3O4/MnO2 was captured. Surface morphology, which is commonly expressed in dimensions of exterior hardness, is essential for forecasting catalytic characteristics. The root mean square roughness (RMS) of a material is related to its particle diameter. The average rough surface was 5.89 nm, with the Root Mean Square at 10.37 nm. The rougher the texture and the greater the contact area, the more activation centres there are. The excessive annealing temperature  may have caused the nanocatalyst's irregular structure.
3.7 Magnetic behavior of synthesized Fe3O4/MnO2 nanocomposites
The magnetic profiles of Fe3O4 nanoparticles and Fe3O4/MnO2 omposite fragments are shown in Fig. 7(a) and (b). Two very different designs are similar, and the Fe3O4/MnO2 composite particles possess super-paramagnetic characteristics. Even as permanent magnet field was curtailed, the ferromagnetism lessened until it dropped to zero at H = 0. No residual magnetic moment stayed. It further inhibits particle aggregation, and the powders could be incredibly quickly distributed equally because once the magnetic field is excised. Fe3O4 nanoparticles have a saturation magnetization of 68.1 emu/g, while Fe3O4/MnO2 considered as part have a magnetization of 33.5 emu/g.[14, 20]
3.8 Effect of core magnet Fe3O4/MnO2 catalyst loading on biodiesel production
Effect of Fe3O4/MnO2 nanocomposites posses basic surface sites, which make them highly efficient in catalytic processes. Transesterification reaction was strongly affected by catalyst concentration. Biodiesel conversion was investigated with 12:1 M ratio of methanol: oil at a temperature of 550C for 50 min. When the catalyst concentration was increased from 5wt % to 15wt% the conversion was increased from 4–90% respectively as shown in Fig. 9 (a). However when the catalyst concentration was increased beyond 15 wt%, there is slight reduction in the conversion due to slurry being viscous and emulsified 
3.9. Effect of methanol to oil ratio on biodiesel production
Important factor governing the biodiesel conversion is methanol to oil molar ratio. The stoichiometry ratio of the transesterification reaction requires 3 mol of methanol to yield 1 mol of glycerol and 3 mol of fatty esters. Being a reversible reaction excess methanol is used to shift the reaction to the right. The reaction was carried out by varying molar ratios of methanol from 5:1 to 14:1 under the conditions of 14 wt% catalyst, reaction temperature of 600 C in 50 min. Conversion of biodiesel was increased from 9 to 90% as the molar ratio increased from 5:1 to 12:1 (Fig. 9 (b)). The conversion decreased from 90–78% when the molar ratio was further increased from 12:1 to 14:1, this is due to accumulation of methanol and viscous nature of the fluid .
3.10. Effect of temperature on biodiesel production
Reaction temperature is another important criterion that will affect the yield of biodiesel. Each experiment was run for 50 min with 15 wt% catalyst and 12:1 methanol oil molar ratio. The reaction temperature was varied from 40 to 800 C as shown in Fig. 10 (a). The result indicates that the biodiesel conversion was low at lower temperature with only 60% at 400 C, biodiesel conversion increased sharply and reached 95% at 600 C. Increase in the temperature increases the yield respectively due to increase in the solubility of the solvent with enhanced diffusion rate. The conversion dropped on further increase in temperature 88% at 700C. The yield tends to decrease after certain temperature due to methanol vaporization .
3.11. Effect of reusability of Fe 3 O 4 /MnO 2 NCs
Reusability is one of the most important features of a heterogeneous Fe3O4/MnO2 catalyst. Catalysts were reused to test the lifetime and stability of the catalyst. The catalyst used after the first cycle was collected and dried for the use in the successive cycles. To study the effect of reusability, experiments were carried out at 600 C, with a 12:1 methanol to oil ratio, 14 wt.% of catalyst for 50 min. The activity of the regenerated catalyst used for the sequential steps tends to remain stable for four cycles where the yield was around 95% (Fig. 8). The conversion was 87% after fourth cycles and tends to decrease at faster rate due to the deactivated active sites 
3.12. Kinetic investigation
The kinetic survey was done by appropriate conditions for the transesterification process. The average rate variable at various heating rate (40–800 C) for the biodiesel synthesis of castor oil engendered by Fe3O4/MnO2 NCs has been estimated Nanocatalyst. Transesterification reaction tends to follow the first order reaction as the product formations (Methyl esters) are studied as function of time. Plot of ln[p] versus ln(dp/dt) at different interval of time and temperature was found to be linear where rate constant was determined from intercept and slope. The yield tends to increase with respect to time and temperature where the reaction rate rises with increase in temperature . Thus the reaction rate is dependent on reaction temperature and time. Arrhenius relationship and the activation energy were studied for the transesterification process. The activation energy (Ea) was calculated using Eq. (3).
ln k = - Ea/RT + C ---------------- (3)
The activation energy was calculated from the slope of 1/T versus (ln k). The first order tends to fit the kinetic model. The activation energy required for transesterification of castor oil catalyzed by nanocatalyst was found to be 1627.23 J/mol.
3.14 Bio-fuel assessment
The fatty acid methyl ester contents of biofuels compounds were characterized employing Gas chromatography - mass in detection mode, as demonstrated by earlier work. The prevalence of methyl esters is indicated by the distinct peaks in Fig. 11. The greatest signal, with latency duration of 18.7 minutes, shows the existence of 9-octa decenoic acid, methyl ester .