## 4 Conclusions  
In this study, magnetic composites CoFe\({}_{2}\)O\({}_{4}\) and CoFe\({}_{2}\)O\({}_{4}\) stabilized with polyvinylpyrrolidone (PVP) were synthesized by co-deposition. [PERSON]'s refinement of CoFe\({}_{2}\)O\({}_{4}\)/PVP confirms that these composites have a pure spinel cubic structure without any additional phases with the space group Fd-3m.  
The obtained samples were characterized by various physico-chemical methods. The X-ray image of the CoFe\({}_{2}\)O\({}_{4}\)/PVP nanocomposite shows that CoFe\({}_{2}\)O\({}_{4}\) is a cubic spinel structure with a lattice constant of a = 0.83880 nm and has a size in the range from 10 to 15 nm. According to the results of X-ray phase analysis, the unit cell parameters of CoFe\({}_{2}\)O\({}_{4}\) and CoFe\({}_{2}\)O\({}_{4}\)/PVP are 0.83880 and 0.83939 nm, respectively. The stabilization of CoFe\({}_{2}\)O\({}_{4}\) using PVP can minimize the agglomeration of CoFe\({}_{2}\)O\({}_{4}\) nanoparticles and forms a composite together with a ferrite nanocrystal. The decrease in effective fields can be explained by a decrease in the particle size of cobalt ferrite stabilized by PVP (particle diameter is less than 16 nm). Surface stabilization leads to a decrease in the size of ferrite nanocrystallites in nanocomposites. It can be noted that the magnetic composites CoFe\({}_{2}\)O\({}_{4}\) stabilized with polyvinylpyrrolidone CoFe\({}_{2}\)O\({}_{4}\) prepared in this work are characterized by a sufficiently developed specific surface area, the value of which was in the range of 126-156 m\({}^{2}\)/g.  
Figure 12: Absorption spectra of the initial aqueous solution of phenol and from the oxidation time: (**a**) initial phenol, (**b**) oxidation time of 1 h, (**c**) oxidation time of 2.0 h.  
Magnetic nanoparticles of CoFe\({}_{2}\)O\({}_{4}\)/PVP can improve the thermal stability of the nanocomposite due to the interaction between the CoFe\({}_{2}\)O\({}_{4}\) nanoparticle and PVP. CoFe\({}_{2}\)O\({}_{4}\)/PVP nanocomposites exhibit ferromagnetic behavior.  
Thus, a comparative study of the properties of cobalt ferrite and CoFe\({}_{2}\)O\({}_{4}\)/PVP was carried out. The effectiveness of using the synthesized magnetic composite CoFe\({}_{2}\)O\({}_{4}\)/PVP for the oxidation of phenol in the presence of hydrogen peroxide in order to obtain oxygen-containing compounds is shown.  
Conceptualization, T.V.S., B.T.D. and L.R.S.; methodology, T.V.S. and B.T.D.; software, L.R.S. and B.T.D.; validation, B.T.D., L.R.S. and T.S.A.; formal analysis, B.T.D., L.R.S. and T.S.A.; investigation, B.T.D., U.N.D. and M.S.I.; resources, T.V.S. and B.T.D.; data curation, T.V.S., L.R.S. and B.T.D.; writing--original draft preparation, B.T.D. and L.R.S.; writing--review and editing, B.T.D. and L.R.S.; visualization, T.V.S., U.N.D. and M.S.I.; supervision, T.V.S., L.R.S. and B.T.D.; project administration, T.V.S.; funding acquisition, T.V.S. and B.T.D. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Science Committee of the Ministry of Education and Science of the Republic of Kazakhstan, grant No. AP14870308 \"Development of technology for catalytic petrochemical synthesis of oxygen-containing compounds from aromatic hydrocarbons in the presence of nanoscale magnetic composites\", Center of Physicochemical Methods of Research and Analysis.  
Not applicable.  
The data presented in this study are available in article.  
The authors declare no conflicts of interest.