Here, we discuss the fabrication and problems of application of chitosan-based composite materials for the removal of hazardous metal ions from tap water and wastewater. The chitosan-based composites containing iron oxides for the uptake of Sr²⁺ ions were fabricated via a co-precipitation method with variation of the iron/chitosan ratio and pH of the medium. The morphology and composition of the fabricated sorbents were characterized using scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDX) and X-ray diffraction (XRD) analysis. We have shown that the suggested fabrication approach allows for a homogeneous distribution of the inorganic phase in the polymer matrix. Investigations of the sorption performance of the composites have shown that they are efficient sorbents for ⁹⁰Sr radionuclides uptake from tap water. The composite sorbent containing amorphous iron oxide in a chitosan matrix and calcined at 105 °C showed the best sorption characteristics. We have also demonstrated that there is an optimal iron oxide content in the composite: with increasing oxide content, the efficiency of the sorbents decreases due to poor stability in solution, especially in alkaline media. The alternative approach yielding magnetic chitosan-based composites with sufficiently good sorption performance and stability in neutral and weakly alkaline media is suggested.

The article describes the synthesis of composite sorbents by immobilizing iron oxide in a polymer matrix with subsequent hydrothermal treatment at a temperature of 175 °C. The sorbents based on magnetite and hematite were synthesized, their magnetic properties and phase composition were evaluated, and the iron content was determined. Sorption characteristics of the composites towards microconcentrations of Sr-90 radionuclide in solutions with different mineralization and pH were investigated. It was shown that the sorbent based on magnetite was the most efficient. In alkaline media with pH above 11, the composite sorbent based on magnetite exhibited increased selectivity towards Sr-90 and proved to be suitable for application under dynamic sorption conditions with subsequent desorption of the radionuclide with a solution of HNO₃.

Introduction of magnetic nanoparticles into composite sorbents based on polymer matrices has received great attention due to the possibility of using cheap iron oxides and removing spent sorbents by means of magnetic separation. In the present paper, we discuss the problem of creating magnetic sorbents using two types of matrices as host materials: synthetic cation exchange resin and natural aminopolysaccharide chitosan. The possibilities of applying matrices for the in situ formation of oxide phases of a specified composition with the required content of an inorganic component in a composite material were estimated. The composition of the oxide phase formed in the composite material was studied, and particle sizes were evaluated by the method of X-ray diffraction analysis. Magnetic characteristics were investigated. Sorption characteristics with respect to strontium for the composites containing iron oxides were determined.

The composites manganese oxide/carbon fiber are obtained by chemical and electrochemical deposition. The process of electrodeposition was carried out in the presence of tetraalkylammonium cations of neutral SAA Triton X-100 in a potentiostatic regime by oxidating Mn²⁺ salts at +1.0 V (with respect to Ag/AgCl). Cathodic deposition was carried out in aqueous electrolytes NH₄Cl and KCl and in the presence of polyelectrolyte of chitosan with oxidation of the formed precipitates by oxygen in air. The obtained composites are characterized by scanning electron microscopy, X-ray diffraction, and cyclic volt-amperometry techniques. The mechanism of film formation at the surface of the carbon fiber and the electrochemical properties of the composites are discussed.

The data on the possibility of obtaining transition metal ferrocyanides, which are highly selective compounds with respect to cesium, in polysaccharide matrices (cellulose, chitin, chitosan) are systematized and generalized. Based on the electron microscopy data, it has been found that the distribution of the sorption active component (nickel ferrocyanide) in the chitosan matrix is fairly uniform. The crystallite sizes calculated from X-ray powder diffraction data are significantly higher for Zn–K chitosan/ferrocyanide sorbent as compared to Ni–K and Cu–K chitosan/ferrocyanide sorbents. A comparative analysis of the sorption properties and stabilities of the Zn–K, Zn–Ni, and Cu–K chitosan/ferrocyanide sorbents and sorbent Thermoxide-35 in the extraction of cesium from alkaline mineralized solutions and seawater has been carried out.