Study of the Oxidation of Phenol in the Presence of a Magnetic Composite Catalyst CoFe\({}_{2}\)O\({}_{4}\)/Polyvinylpyrrolidone  
[PERSON]  
1 Center of Physical-Chemical Methods of Research and Analysis, Al-Farabi Kazakh National University, Almaty 050012, Kazakhstan; [EMAIL_ADDRESS] (T.V.S.); [EMAIL_ADDRESS] (B.T.D.);  
[EMAIL_ADDRESS] (M.S.I.); [EMAIL_ADDRESS] (U.N.D.); [EMAIL_ADDRESS] (T.S.A.)  
1 Center of Physical-Chemical Methods of Research and Analysis, Al-Farabi Kazakh National University, Almaty 050012, Kazakhstan; [EMAIL_ADDRESS] (T.V.S.); [EMAIL_ADDRESS] (B.T.D.);  
[EMAIL_ADDRESS] (M.S.I.); [EMAIL_ADDRESS] (U.N.D.); [EMAIL_ADDRESS] (T.S.A.)  
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Cobalt ferrite (CoFe\({}_{2}\)O\({}_{4}\)) is a reverse spinel-type and can be synthesized by the hydrothermal method, ball grinding, chemical reduction, sol-gel, microwave oven, and co-precipitation methods [9; 22; 24; 25; 27]. The co-deposition method is a simple, less toxic synthesis option with a high yield and ease in separating the target substance from the liquid after the process. Cobalt (II) ferrite is a promising object that has received close attention from researchers, since it has very important characteristics that can be applied for technical purposes. Being a magnetic material, it can be used as sorbents of various toxic compounds, for example, organic dyes. It is known that cobalt (II) ferrite is also used for the synthesis of catalytic composites, sorbents, and inorganic compositions [37; 38; 39; 40; 41; 1; 2; 9; 33; 34; 35; 1].  
It is well known that nanostructured materials tend to decrease their surface energy, and this, of course, is the cause of thermodynamic instability. Unmodified nanoparticles can be stabilized either by the sorption of molecules from the environment or by reducing the surface area using coagulation or agglomeration. Various materials can be used to stabilize metal nanoparticles, for example, water-soluble polymers [3; 46; 1; 3; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78]. Small organic molecules serve as stabilizers, and organic molecules can bind to the surface of metal particles in the form of metal ligands. Stabilizer polymers promote the presence of a strong bond at various sites and can be bonded to a metal particle in different places [3; 46; 1; 3; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78]. The literature describes a number of studies related to the production of ferrites stabilized by polymers [79; 79; 79; 78]. All these studies were mainly focused only on the preparation of the material and its characteristics, without describing the effectiveness of use for a particular process. In these works, different polymers (polyaniline, chitosan, polystyrene, polyacrylic acid, polyethyleneemin) are used for stabilization, as well as catalysts based on other metals (Pd, Pt, Ag, Fe), and not cobalt ferrite.  
Poly(n-vinyl-2-pyrrolidone) (PVP) is one of the most well-known polymers used to stabilize nanoparticles, since it meets the necessary requirements of both ligands and steric sites [3; 1; 2]. For catalysts based on PVP-stabilized nanomaterials, the size of nanoparticles and the stability of the nanomaterial were analyzed under the conditions of a catalytic reaction. It was found that the use of PVP stabilization for the nanocatalysts led to a reduction in the size of Pd nanoparticles to 3 nm in the Suzuki reaction and improved the catalytic activity of the catalyst [93].  
The purpose of this study is to synthesize a magnetically controlled magnetic composite, CoFe\({}_{2}\)O\({}_{4}\) (known as cobalt ferrite), stabilized with polyvinylpyrrolidone (PVP); to study the catalyst by physico-chemical research methods; and to determine the effectiveness of the CoFe\({}_{2}\)O\({}_{4}\)/PVP catalyst in the phenol oxidation reaction.