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The use of rice husk (the waste in the production of seeded rice (Oryza sativa) as a sorption material for the removal of pollutants of various classes – inorganic (Cr, Ni, Co, Pb, Hg, As, Cd, Cu, Zn) and organic substances (synthetic and natural dyes, phenols, antibiotics, polycyclic aromatic compounds, humic acids, pesticides, chitosan) from aqueous media is generalized. The literature data on the structure of seeded rice, the volume of its cultivation, the chemical composition, and some components of rice husk are given. The methods of physical and chemical (the use of inorganic acids, salts, and alkalis) are described activation, as well as modification of rice husks using surfactants, Fe3O4 nanoparticles, functional agents, and monomers (polymerization reactions). Quantitative characteristics of the absorption of various pollutants (recoveries, equilibrium limit sorption) are given. The influence of pH, temperature, the concentration of pollutants, phase contact time, volume, and mass of rice husk on sorption and removal of pollutants from aqueous media is shown. Possible sorption mechanisms, kinetic and sorption models are described. It is revealed that the isotherms of the sorption of pollutants in most cases are most adequately described by Langmuir and Freundlich models, and the kinetics of the process is a pseudo-second-order model.

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An efficient sorbent for magnetic solid-phase extraction was developed from Fe 3 O 4 nanoparticles covered with aminated hypercrosslinked polystyrene. The sorbent has a saturation magnetization of 47 emu/g and a surface area of 509 mg/g and was tested for the extraction of 11 phenols from aqueous media. The optimum conditions were as follows: pH 3; adsorbent mass, 20.0 mg; adsorption time, 30 min; eluent (acetone) volume, 0.5 mL; and desorption time, 5 min. The enrichment factor after desorption reached 1595-1716 and the maximum adsorption capacity was 501-909 mg/g. Capillary electrophoresis was applied successively to separate 11 phenols after solid-phase extraction. The best separation was achieved using a fused silica capillary and borate buffer (pH 10.7) as a supporting electrolyte. After optimization, the linearity range was from 0.2 to 950 μg/L, and the limits of detection were 0.05-0.2 μg/L. The relative standard deviation varied from 6.1 to 8.7% (C = 1 μg/L) and from 2.9 to 3.5% (C = 500 μg/L). The determination of phenols is complicated in eutrophic water and spring water with a high content of humic and fulvic acids.

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