V. Petkova

Thermal Analysis of Polymer-silicate Nanocomposites

The thermal behavior of epoxy-smectite nanocomposites (hybrids) is examined by non-isothermal thermogravimetry (TG, DTG and DTA) in air atmosphere. It has been shown that the thermal stability of hybrids is much greater than that of epoxy resin and strongly depends on both the smectite loading and the type of the gallery cations of organically modified smectites. The kinetics of degradation of nanocomposites is significantly influenced by the presence of smectites and proceeds in three stages. Stage I is attributed to the effect of quaternized ammonium ion exchanged smectite, as stages II and III are associated with the decomposition of the bulk epoxy resin. Because of the interfacial interactions and thesilicate-polymer multilayered nanoscale organization, the nanocomposites act as excellent heat insulator and mass transport barrier, which shift the thermal decomposition peaks towards much higher temperatures.

Investigation on Thermal Decomposition of Pyrite Part I

Thermochemical decomposition of pyrite in air-gas medium has been studied by means of MOM-Q 1500D Derivatograph. The derivatograms have been obtained at a heating rate of 5 K min-1 and air flowrate of 25 1 h-1 to final temperatures of 833, 933 and 1273 K, chosen on the basis of the stepwise oxidation of pyrite. The solid product is analyzed using X-ray powder diffraction and Mössbauer spectrometer techniques. The formation of nonstoichiometric sulfides (pyrrhotines) as intermediates has been confirmed. The second stage of decomposition is the oxidation of these pyrrhotines to hematite. The recorded weight losses are lower than the theoretically possible because of the formed nonstoichiometric iron sulfides. The complicated structure of the intermediate products has been confirmed by means of other techniques.

MECHANISM AND KINETICS OF INORGANIC SULPHATES DECOMPOSITION

Thermal decomposition of different inorganic sulphates are presented. A number of techniques, but mainly TG and DTA, are used to prove the mechanism and kinetics of CaSO4, BaSO4, FeSO4·xH2O, Al2(SO4)3·xH2O under various gas atmospheres. It is shown how the partial pressure of gas components and heating rate may effect the mechanism and kinetic parameters. There are also examples on the effects of some additives and initial treatment on the thermal processes.On the base of the results obtained some recommendations are given concerning the precautions to be taken into account in the thermal decomposition studies and the sulphur recovering.

Investigation on The Thermal Properties of Fe2O(SO4)2. Part II

The data on the thermal decomposition of FeSO4⋅H2O upon various regimes of heating and gaseous environment prove the formation of intermediate products of the types Fe2O(SO4)2 and FeOHSO4, their stability and amount being determined mainly by temperature and oxygen-reduction potential.This communication aims at presenting results on the synthesis and characterization of Fe2O(SO4)2. The synthesis was carried out using a laboratory thermal equipment operating under isothermal conditions in the temperature range 713–813 K in a gaseous environment either poor in oxygen or containing 100% oxygen. The experimental conditions under which Fe2O(SO4)2 is stable are established. The effect of three basic parameters on the synthesis of Fe2O(SO4)2 is clarified: the oxygen partial pressure, the ratio PH2O/PO2 and the temperature and the mode of heating. Mössbauer spectroscopy and X-ray diffraction data for Fe2O(SO4)2 are presented.

Mechano-chemical Activation of Dolomite

Mechano-chemical activation is a widely used method for increasing the reaction activity of solids and, consequently, to accelerate solid phase reactions and to reduce the temperature of the subsequent thermal decomposition. Thermal decomposition of triboactivated calcium carbonate is a subject of different studies while dolomite decomposition has limited data.The present work represents a study of thermal stability and phase transitions of mechano-chemical activated dolomite under different conditions, namely using various amounts and kind of milling balls and the duration of activation. Temperatures of decomposition of MgCO3 and CaCO3 are specified. The study includes the determination of the thermal stability and the rate of thermal decomposition of activated dolomite.

Thermochemical characterization of chicken litter and peat as a source for energy recovery

The shortage of raw materials and the environmental problems due to pollution require development of new green technologies utilizing some wastes and transforming them to secondary raw materials. The aim of this work is to study the properties of poultry waste to propose possibilities to minimizing the released emissions and avoiding the risk for human health and the environment. At the same time, two types of low grade peats with different origin are studied as components for the production of soil conditioners. During the studies, we applied the inductively coupled plasma (ICP) and chemical analysis, powder X-ray diffraction, thermal analysis, IR spectroscopy, and scanning electron microscopy for determining the composition, crystal phase, the shape and size of particles, and thermal stability of the investigated samples. The chemical and the phase compositions of the studied samples confirmed that the content of nutrient compounds and of the carbon substances is suitable as an effective secondary raw material for soil conditioners. It is found that the poultry wastes and peat samples have a similar phase and chemical composition and contain an organic mass in the form of carbon components with amorphous, fibrous, and skeleton-like structure, suitable to be combined with other nutrient-containing compounds. During the thermal treatment, the carbon compounds are oxidized releasing heat. Based on that the materials under study are considered as environmentally friendly fuels, releasing relatively low emissions.

Thermal analysis of mechanoactivated mixtures of tunisia phosphorite and ammonium sulfate

The thermal behavior of Tunisia phosphorite and ammonium sulfate mixtures are examined by non-isothermal thermogravimetry in air atmosphere. It has been shown that the thermal stability of mixtures have different behavior after mechano-chemical treatment due to phase changes in the mixtures. New solid phases are confirmed by the stages and rate of mass changes and also by the heat effects observed. New phases are also confirmed by using X-ray diffraction method. Based on the data obtained by the mechanism of chemical transformations is proposed. The kinetics of mechano-activated mixtures decomposition is significantly influenced by the time of treatment and proceeds in few stages. Stage I is attributed to the effect of partially ammonia releasing, when the next stages are associated with the decomposition of apatite structures. Because of the interfacial interactions during mechano-chemical treatment insoluble phosphorous forms from apatite structures are transformed to the soluble forms suitable for plants nutrition. The results have shown that the soluble form can be controlled by the initial components ratio and conditions of treatment on the way to obtain slow releasing nutrition products.

Thermal Stability and Properties of New NPS-Fertilisers

New NPS-fertilisers are investigated using TG-DTA systems and other techniques to determine their thermal stability and properties. The main component is ammonium sulphate by-product from clean-up technologies. Acidic reaction of ammonium sulphate (AS) is compensated by adding treated or untreated phosphates. Some samples are additionally mechanochemically activated. Tribochemical effects are confirmed. Distribution and conversion of harmful impurities are also studied. The results clearly show that the histories of components, additional treatment and the initial content of impurities affect the thermal properties of the new fertilisers. The mass components ratio influences the thermal fertilisers stability and their solubility. It is shown that the by-product from electron beam technology is the most suitable component, because of high-activity. The results obtained confirmed that TG and DTA techniques could be successfully used for products quality control. Most of the simultaneous TG, DTG and DTA curves may have a practical application for future studies and comparative analysis.

Isothermal investigation of decomposition of FeSO4·H2O-BaO2 mixtures

Isothermal studies were conducted on mixtures of Fe2SO4·H2O in BaO2 in molar ratios ofn=4, 2 and 1 at temperatures of 573 and 1073 K, in a closed crucible, in air as gas medium. The solid products of decomposition were investigated by means of X-ray analysis, Mössbauer spectroscopy and electron spectroscopy.The experiments revealed that the mechanism of the process is connected with the formation of different quantities of barium ferrites (BaFeO3, BaFe2O4 and BaFe12O19), as well as BaSO4 and Fe2O3, depending on the quantity of BaO2 in the initial mixture, the partial pressure of the gas components and temperature. Differences were found in the mechanism of the process for the same mixtures under dynamic temperature conditions.

Thermal behaviour of nitric-acid-treated biomass and chicken litter mixtures

The sustainable agriculture is based on biological (organic and ecological) agriculture. This is a production system that restricts the use of fertilizers, pesticides and growth regulators. Commercial chicken production is one of the largest agricultural industries generating large quantities of poultry waste, a serious contaminant of air, soil and water. This requires its processing and utilization to obtain products, which can be used as a source of bioenergy and soil improvers. In this paper, we proposed a new solution of using chicken litter as soil improvers. For the purpose, we prepared four mixture samples, composed of chicken litter, another one industrial waste, namely wood ash and nitric acid, in different mass ratios. The aim of the study is the chemical and thermal characterization of the samples in order to verify the proposed approach for waste utilization. For the purpose, we used chemical analysis, powder X-ray diffraction, Fourier transform infrared spectroscopy and thermal analysis. It was found that the selected raw materials have a structure and composition, which defines them as carriers of essential micro-nutrients for the plants, without excessive content of heavy metals. The experimental results show that used complex of methods (XRD, FT-IR and Thermal analysis) is appropriate for the investigation of the mineralization process and the phase transformations under NA treatment.