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ABSTRACT
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Within this paper, investigations were carried out in order to obtain data for determining the maximum absorption capacity and the conditions in which the balance in the systems occurs: Mn2+ ions - expanded perlite and Mn2 + ions -... more
Within this paper, investigations were carried out in order to obtain data for determining the maximum absorption capacity and the conditions in which the balance in the systems occurs: Mn2+ ions - expanded perlite and Mn2 + ions - carbonized sunflower husks. A series of tests were performed using model solutions of Mn2+ ions with different concentrations.Experimental data obtained by the equilibrium absorption of the systems: Mn2+ ions - expanded perlite and Mn2+ ions - carbonized sunflower husks are fitted with four commonly used isotherms: Langmuir, Freundlich, Langmuir – Freundlich and Redlich – Peterson, with the application of MATLAB/Curve Fitting Toolbox. The obtained results from analyzes are shown graphically and tabular, after which a comparison of the adsorption characteristics of the two adsorbents is performed.
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Zeolites are nano-porous crystalline aluminosilicates. Natural zeolites are non-toxic and safe for humans which expand their application in different fields. Clinoptilolite is the most abundant natural zeolite with high purity that occurs... more
Zeolites are nano-porous crystalline aluminosilicates. Natural zeolites are non-toxic and safe for humans which expand their application in different fields. Clinoptilolite is the most abundant natural zeolite with high purity that occurs in many parts of the world. It has a frame structure in which the tetrahedra of silicon [SiO4/2] and aluminium [AlO4/2]- are interconnected with oxygen bridge. Cations like K+, Na+ and Ca2+ and water are located in its pores and large cavities. Zeolites have high ion exchange capacity, selective adsorption capacity and thermal and mechanical stability.In this paper, the characterization of the natural zeolite - clinoptilolite from Bulgaria is performed. The investigated clinoptilolite was characterized in terms of its chemical composition, particle size distribution, structural morphology (SEM, XRD, FTIR) and thermal analysis. The chemical analysis show that clinoptilolite contains 69.7% of SiO2 and 11.4% of Al2O3. As specific surface area is the m...
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Wastewater that contains heavy metal ions is considered as the serious threat for environmental pollution. Most of the heavy metals are toxic and their ions are not biodegradable with the tendency to accumulate in the soil and in the... more
Wastewater that contains heavy metal ions is considered as the serious threat for environmental pollution. Most of the heavy metals are toxic and their ions are not biodegradable with the tendency to accumulate in the soil and in the living organisms, and hence they are significant environmental pollutants. Therefore, the treatment of the heavy metal ions and their elimination from water and wastewater is very important for environmental protection. Adsorption is the most commonly used method for removal of the heavy metal ions of aqueous solutions. There are a number of materials that can be applied as adsorbents for heavy metals.In this paper, the possibility of removing of Mn (II) ions from aqueous solutions using modified natural zeolite (clinoptilolite) was investigated under different operating conditions. For this purpose, the effect of several working parameters on the percentage of the removal of manganese ions was investigated, including: the effect of pH of the solution (...
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A broad spectrum of solid–liquid extraction techniques is used for isolation of the biological activecompounds, for receiving natural products from plant material. For this purpose, different types of polar andnon-polar extractive agents... more
A broad spectrum of solid–liquid extraction techniques is used for isolation of the biological activecompounds, for receiving natural products from plant material. For this purpose, different types of polar andnon-polar extractive agents (solvents) are used. White mustard seeds are a natural material of which natural oilis extracted. Ultrasound-assisted extraction (UAE) of oil from white mustard (sinapis alba l.) seeds was studied,as well as the influence of two working parameters (extraction times and extraction temperature), while using ofone polar (ethanol–96 %) and two non-polar solvents (petroleum ether–100 %, methylene chloride–100 %).Ultrasound extraction is performed for duration of 30, 60 and 90 min at 25, 30 and 35 ˚C, at a constantfrequency of ultrasound pulses of 40 kHz, 240 W ultrasound power and module (ratio) between solvent andwhite mustard seeds (volume of solvent [ml]:seed weight [g] = 33.333:1). In Statgraphics Centurion XVII,software optimization is made to deter...
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Natural minerals from different localities in the Republic of Macedonia are selected for elimination of Cr(VI) ions from water resources. For that aim are selected: aksil (Kriva Palanka), trepel (Bitola), SiO2 amorphous (Kozuf), pemza... more
Natural minerals from different localities in the Republic of Macedonia are selected for elimination of Cr(VI) ions from water resources. For that aim are selected: aksil (Kriva Palanka), trepel (Bitola), SiO2 amorphous (Kozuf), pemza (Bojanciste). In this study, their adsorption capacity is analyzed using spectrophotometric method (UV/VIS Spectrophotometer). Results from the spectrophotometric analysis in all used examples gave us insight for the starting concentration of Cr(VI) before adsorption and concentration after adsorption. The physical, chemical and mineralogical characteristics of adsorbents are studied. XRD, TGA-DTA and FT-IR analysis are used for characterization of natural mineral materials. The surface area of the sorbents were measured by BET method. With aim to determine the optimum pH value for maximal removal of Cr(VI) ions, the point of zero charge, pHPZC, for investigated materials were obtained. The aim of the study is to select which adsorbent is more efficien...
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Removing hexavalent chromium from contaminated wastewater is very important because of toxicity to living organisms. Chromium is carcinogenic and mutagenic in very low concentration values (sub-ppm). The ability of the natural mineral... more
Removing hexavalent chromium from contaminated wastewater is very important because of toxicity to living organisms. Chromium is carcinogenic and mutagenic in very low concentration values (sub-ppm). The ability of the natural mineral (bentonite) for adsorption of hexavalent chromium, Cr(VI), from aqueous solutions was investigated. The influence of different physical and physicochemical parameters (pH, amount of adsorbent, adsorbate initial concentration) was examined. For characterization of adsorbent, classical chemical analysis thermogravimetric analysis (DTA/TGA), XRD analysis, FTIR-analysis and determination of specific surface area by BET were performed. For quantitative monitoring of the dynamics of studied system for the presence of Cr(VI) ions in model solutions, the AAS and UV/Vis analysis were used. The obtained experimental results were used for modeling of the equilibrium of the process through the application of software package MATLAB/Curve Fitting Toolbox., Followin...
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The goal of this work is isolation of tomato seed oil from the tomato waste (skin and seed) from tomato processing industry by utilization of non-conventional, green solvent technology. In the frames of experimental research, the... more
The goal of this work is isolation of tomato seed oil from the tomato waste (skin and seed) from tomato processing industry by utilization of non-conventional, green solvent technology. In the frames of experimental research, the influence of working parameters (temperature, pressure and extraction time) on the total yield of isolated tomato seed oil. Dynamic method for determination of solubility parameter in a supercritical CO2 has been used to determine the solubility of tomato seed oil in the supercritical CO2. Obtained results regarding the influence of operating parameters on total yield of extracted tomato seed oil are presented graphically. The influence of the supercritical fluid’ density on the tomato seed oil’ solubility was determined based on those results. The chemical composition of isolated tomato seed oil was determined by application of Gas Chromatography.
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The aim of the present work is to study the gasification and combustion of biomass and solid waste material. An empirically - experimental model was developed with the main objective of calculating the gas composition at different... more
The aim of the present work is to study the gasification and combustion of biomass and solid waste material. An empirically - experimental model was developed with the main objective of calculating the gas composition at different operating conditions. The present model takes into consideration few assumptions, and gives a simplified model for determination of the molar rates of tall gas components on the fluidized bed exit. Key words: modeling, gasification, combustion, fluidized bed, biomass, solid waste material.
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SYNOPSIS The Black Sea fisheries diagnostic analysis has been performed under the initiative of the Black Sea Commission for the long-term period. Some of the most important pressure and state indicators with significant impact on the... more
SYNOPSIS The Black Sea fisheries diagnostic analysis has been performed under the initiative of the Black Sea Commission for the long-term period. Some of the most important pressure and state indicators with significant impact on the environment reveal the increasing trophic level in the last investigated years, indicating higher abundance of species like Rapana venosa and significant contribution of some high trophic levels such M.merlangus. The performed analysis show significant decrease of anchovy catch since 2005. The increasing of FiB is connected with significant decrease of anchovy fishery and expanding of the exploited ecosystem. Perhaps, this is connected with sprat and whiting fishery intensification (e.g.Turkey), still high anchovy catches and sea snail (Rapana venosa, e.g. Bulgaria and Turkey) fishery expansion too. Reporting on catches needs improvement. Illegal fishery should be assessed as well. INTRODUCTION Under anthropological and natural impact, the Black Sea ec...