The thesis is devoted to the creation of modified and composite sorbents on the basis of plant, natural mineral and synthetic raw materials for the removal of residual amounts of organic pollutants and the selective extraction of heavy metal ions from waste water in order to organize low-waste and safe water consumption systems in industry and energy sector.
The conditions for the modification of sorbents based on natural plant and mineral raw materials, carbon, synthetic mineral and polymer materials were defined. Methods of chemical modification of wood sawdust with urea, paraform-thiocarbamide solutions and thermo-chemical modification in presence of activators of carbonization – ammonium salts of orthophosphoric and sulfate acids were developed. A composite sorbent is created on the basis of a natural mineral zeolite by deposition of humic acids on its surface. The modified ferrite sorbent was obtained by the addition of a solution of thiocarbamide in a mixture of iron salts during the synthesis of magnetite. The composite sorbent is synthesized on the basis of cation exchange resin KU-2-8, which contains magnetite nanoparticles deposited in pores. The method of obtaining a composite sorbent has been developed, in which a matrix carrier is activated charcoal Filtrasorb 300, and a dispersed phase – MnO2.
The dependence of the heavy metals sorption on the contact time at different temperatures was investigated, heavy metals sorption isotherms on modified lignocellulosic sorbents were obtained. Sorption of heavy metal sorbents onto modified lignocellulosic materials best runs in the pH range 4-7 and is determined by the nature of the sorption centers of hydroxyl and carboxyl groups of lignocellulosic material and the electronodonor -N-, S- and P-containing groups grafted due to chemical or physical-chemical modification. The influence of one-, two- and three-charge cations- ambient electrolytes on the sorption of heavy metals from aqueous solutions has been investigated.
The copper ions sorption process by composite sorbents from the chemical and diffusion kinetics point of view has been studied. Sorption isotherms have been built, the efficiency of granular sorbents under dynamic conditions is investigated. The influence of the presence of ambient one-, two- and three-charge cations on the efficiency of copper ion sorption was investigated. The presence of such cations suppresses the process of copper extraction by zeolite-humic acids sorbent. Composite sorbent KU-2-8-M in the process of heavy metals removal did not reduce its effectiveness in large excess of alkaline and alkaline-earth cations.
The investigations of sorption properties of composite coal sorbent F300-MnO2 in the processes of extraction of ions Mn2+ and Fe2+, organic pollutants such as oil, phenol, anionic and nonionic surfactants, dyes, from aqueous solutions were conducted. The sorption isotherms of organic contaminants of various classes on F300 and F300-MnO2 have shown that the modification with KMnO4 solution enhances the sorption ability of coal in the case of removal of organic substances with negative -potential of particles. The effect of oxidative removal of pollutants is more pronounced during the process for a relatively long time (several days or weeks). The specific sorption capacity of the F300-MnO2 to petroleum was as much as twice higher then of the unmodified F300. The method is best used at the post-treatment stage to remove residual amounts of dissolved oil products.
The scientific principles of creation of sorbents, selective to heavy metals, and sorbents of complex action are developed. The selectivity of the sorbent, reflected in the increase of the distribution coefficient of heavy metal ions between the solid phase and solution and the increase of the separation coefficient of the basic and other cations, depends on the cation exchange capacity of the sorbent, i.e. the share of the metal ions extracted due to nonspecific sorption. Selectivity increases with decreasing concentration of acidic cation exchange centers. The ratio between nonspecific and specific sorption by lignocellulosic sorbents can be changed by chemical interaction of acidic centers with alkaline nitrogen and sulfur-containing substances – urea, a mixture of thiourea and paraform, as well as by phosphorylation, resulting in the formation of electron-donor groups containing nitrogen, sulfur and phosphorus atoms, which are new active centers of heavy metal sorption. Principal schemes for extraction of heavy metal ions and organic pollutants from aqueous solutions by composite and modified sorbents have been developed, which can be successfully used in practice for the purification of process water in the circulating industrial water supply system. The feasibility study of the technology of extraction of heavy metal ions using the composite sorbent KU-2-8-M was carried out.
