Lyudmila Alekseyevna Zemnukhova

A comparative study of the microscopic morphology and chemical characteristics of spicules of Hexactinellids (Hexactinellida) with different structural features of the skeletons, as well as the freshwater Baikal sponge belonging to the class of common sponges (Demospongia), was carried out. The trace element composition of sponge spicules was determined by X-ray fluorescence spectrometry. The spicules of siliceous sponges contain many elements, arranged in decreasing order of concentration: Si, Ca, Fe, Cl, K, Zn, and others. It was shown that the surface layer of sea sponges contains mainly carbon (C), oxygen (O), and to a lesser extent nitrogen (N), silicon (Si), and sodium (Na). The spicules of the studied siliceous sponges can be divided into two groups according to the phase composition, namely one containing crystalline calcium compounds and one without them. Analysis of infrared absorption spectra allows us to conclude that the sponges Euplectella aspergillum, E. suberia and Dactylocalyx sp. contain silica partially bound to the organic matrix, while the silica skeleton of the sponges of the other group (Schulzeviella gigas, Sericolophus sp., Asconema setubalense, Sarostegia oculata, Farrea sp. and Lubomirskia baicalensis sp.) practically does not differ from the precipitated SiO₂. This comparative study of the chemical composition of the skeletons of marine Hexactinellids and common freshwater sponge allows us to conclude that there are no fundamental differences in the chemical composition of spicules, and all of them can be used as a starting material for creating new composite silicon–organic functional materials.

In order to solve the problem of complex utilization of rice straw – waste of rice production – the task was to obtain from vegetable silicon-containing raw materials samples of aluminosilicates that are promising for use as highly efficient sorbents. A series of sodium aluminosilicate samples were synthesized from alkaline hydrolysates of rice straw of various strains of Far Eastern breeding, the effect of synthesis conditions on the properties of the final product was investigated. The chemical and phase composition of the samples were determined, the particle morphology was observed by scanning electron microscopy, the specific surface area was measured, the IR spectra were recorded, the thermal properties were studied, the limits of thermal stability were determined, and the products of thermal transformations were identified. The acid-base properties of the surface were investigated by the pH-metry method and the Hammett indicator method, and the distribution of active centers was determined. The dependence of the sorption capacity of the obtained aluminosilicates on rice varieties and the conditions of the extraction of silicon from the straw (the duration of alkaline hydrolysis) was established on model aqueous solutions of methylene blue. The results expand the possibilities of comprehensive utilization of agricultural wastes with obtaining valuable products and deepen knowledge about the processing biogenic silicon-containing raw materials and the sorption mechanisms of organic pollutants on aluminosilicate materials.

We have studied amorphous silica samples prepared by a thermal method and precipitation from rice processing waste: straw and grain shells (husk and peelings). We have determined their true and bulk densities, silica content, and sorbed water vapor content. The porosity of the samples has been evaluated by different techniques: nitrogen desorption (Barrett-Joyner-Halenda method) and adsorption (BET analysis), water vapor adsorption, sorption of organic dyes (methylene blue and brilliant green), and positron annihilation spectroscopy. The effect of the nature of raw materials and processing procedure on the physicochemical properties of amorphous silica is examined.

Some important magnetic and local structural properties of amorphous silica separated from biogenic (fruit shell of rice and oats, larch and Korean spruce needles, horsetail pedicels, and diatomic...

The rice floral glume (husk) and its processing products were studied using X-ray photoelectron spectroscopy. We established that the rice husk contained silica in two non-equivalent forms in 1:3 ratio. The predominating form is silicon dioxide, while the minor component contains the silicon bound with the organic component which is stable up to ∼350°C.

This study is devoted to investigation of the composition and content of free amino acids in the wastes of processing of Oryza sativa rice (Poaceae L.), Fagopyrum esculentum buckwheat (Polygonaceae L.), and Helianthus annuus sunflower (Compositae).

Behavior of molecules of adsorbed water in rice hulls, weevil, and amorphous samples of carbon-containing (carbonized, SiO₂ content 47%) and pure silica was studied by ¹H NMR spectroscopy in the temperature range from 200 to 298 K. The temperature dependence of the signal intensity from humid samples shows a decrease in temperature of freezing of the adsorbed water and presence of unfrozen water. This dependence was used for estimating the pore size distribution. For pure amorphous silica, the pore diameter is in the range from 50 to 150 Å with a maximum at about 85 Å.