Raisa Nastas

Moldova State University Institute of Chemistry

The progress of the textile industry has led to a severe increase in the discharge of colored effluents, polluted with dyes and metal ions (non-biodegradable, carcinogenic to humans and environmental hazards). The implementation of effective methodologies and materials for the treatment of wastewater has become an urgent requirement. The present wo...

In this study, activated carbons derived from walnut shells (CA-N) and apple wood (CA-M) were used as adsorbents to remove cobalt(II) and strontium(II) ions from aqueous solutions. The novel materials were obtained using nitric acid (CA-Mox) and nitric acid/urea mixture (CA-Mox-u, CA-Nox-u) as oxidizing agents. The physical–chemical characteristics...

Carbonaceous materials have great potential as catalyst supports since a high metal loading and dispersion can be achieved. Also, it is well known that the role of the support is not simply that of a carrier; the interaction between the active phase and the support can also affect the catalytic activity. The aim of this work was to develop catalyst...

The purpose of this work was to perform adsorption experiments of p-coumaric acid from water solutions on two activated carbons: (i) commercial activated carbon FA (Granucol, Germany) and (ii) of local origin ones AC-C, obtained from apricot stones (Republic of Moldova).

In this paper the situation of pollution with nitrogen compounds both in the EU member states and in the Republic of Moldova was analyzed. Also, the existing methods of determination of nitrate ions are analyzed and the necessity of elaborating the method for determination of the nitrate ions in the presence of nitrite ions.

In this study, activated carbons of local origin (Republic of Moldova) from the apple wood (CA-M) and nut shells (CA-N) were oxidized with nitric acid (sample CA-Mox) and mixture of nitric acid/urea (samples CA-Mox-u and CA-Nox-u) in order to improve their ion-exchange properties. The surface chemistry was characterized by using Boehm and potentiom...

Activated carbons, owing to their versatility, are the most frequently used adsorbents. Their exceptional performance derives from a unique combination of geometrical and chemical properties. The different size and shape of pores, as well as vacancies and steps are responsible for the geometrical heterogeneities of the activated carbon surface; add...

Heavy and radioactive metals (such as Pb, Cd, As, Cs, Sr, Co, Hg etc.) are persistent pollutants with potential hazards, which are characterized with a high toxicity, difficult biodegradation, and are easily accumulated in organisms. Adsorption on active carbons is one of the procedures used for binding of toxic metals. In this study, activated car...

In this work, the results of active carbon (initial and oxidized samples) testing for removal of nitrite ions in oxic condition have been reported. The removal of nitrite ions from water was carried out in a semi-pilot plant equipped with air bubbles and a vessel for the capture of aerated NOx gases. Indigenous active carbons, produced from nut she...

Consumption of polluted water with nitrate and nitrite ions affects adversely consumer health by the occurrence of methaemoglobinemia (especially in young children) and the formation of N-nitroso compounds with carcinogenic potential. The purpose of the paper was to test a series of local active carbons for removal nitrite ions from water through t...

Composite materials resulted from impregnation of active carbons with aqueous solutions of manganese (II) chloride were studied by the methods of gas adsorption, X-ray powder diffraction, atomic absorption spectrometry, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The texture and specific characteristics of porosity, micr...

The main objective of this work was to study the modification introduced in the functionality of modified activated carbons. Carboxylic acids, lactones, anhydrides, phenolic groups, carbonyl groups and quinones can be analyzed by temperature programmed desorption experiments with mass spectrometric detection (TPD). Activated carbon obtained by phys...

EVALUATION OF ACTIVE CARBONS ACID-BASIC PROPERTIES The methodological peculiarities of visual titration method (Boehm method) and electrometric (alkalimetric and acidimetric titrations) for researching of acid-basic properties of carbonaceous adsorbents have been specified. On the surface of active carbons obtained by physical-chemical method of ac...

Four series of samples containing manganese supported carbonaceous adsorbents were prepared. Samples of series AC-B, synthesised from the carbonaceous support with basic surface, were obtained with a yield of 50-60%, while manganese was loaded in amount of 1.44-1.65 % depending on applied method. The samples of series AC-A, synthesised from the car...

Efficient catalysts in the oxidation of hydrogen sulfide oxygen species are activated carbons. Activated carbon research highlights the important role of surface functional groups as a source for free radicals and initiate steps in catalytic activation of oxygen on the surface of activated carbon. Studies show that with increasing oxygen content on...

Efectul chemi-luminescenţei luminolului prezintă un procedeu eficace de estimare comparativă a activităţii catalitice a catalizatorilor. S-a constatat că cel mai pronunţat efect catalitic, având o intensitate a chemi-luminescenţei de 18 ori mai mare faţă de martor, posedă H-forma Al-montmorilonitului intercalat cu oligomeri de aluminiu la raportul...

The most efficient and cost-effective treatment option will depend primarily on the concentration of hydrogen sulphide. Activated carbon removes a variety of water contaminants, including hydrogen sulphide, by adsorbing and oxidation of the hydrogen sulphide species on the carbon particles surface. This work deals with experimental investigation re...

This paper deals with the experimental investigation related to removal of hydrogen sulfide from simulated groundwater by adsorption/oxidation on activated carbons. Carbonaceous adsorbents were synthesized from peach stones by physical-chemical activation method and modified by oxidation following impregnation with Cu2+ by ion-exchange method. Obta...

The paper presents the results concerning hydrogen sulfide removal from model solutions and real groundwater. Active carbons used as adsorbents were synthesized from vegetal by-products following the oxidation with nitric acid. Oxidized active carbons were impregnated with Fe(II) and Cu(II) ions. Structural parameters and the adsorption capacity of...

The changes induced by urea - modification which appears on the surface of activated carbon were measured by attenuated total reflectance (ATR) Infrared (IR) spectroscopy and Raman spectroscopy, elemental analysis, gas adsorption analysis, selective titration, pH of the carbon surface. It is important to know the nature of surface functional groups...

Water conditioning for food industry uses. Tap (drinking) water from many localities of Moldova doesn't always correspond to the "Sanitary standards for drinking water quality" or to the requirements of the "Regulation for non-alcoholic beverages", requiring the need for additional purification/ conditioning. This paper presents research regarding...

Synthesis of new vegetal active carbons, investigation of porous structure and adsorption characteristics, and their using.

Particularităţi de sinteză a adsorbanţilor intercalaţi pe bază de montmorilonit Rezumat În ultimele decenii au început cercetări foarte intense pe plan global în vederea sintezelor unei clase noi de materiale cu proprietăţi de site moleculare, având caracteristicile sorbţional-structurale mai bune, în comparaţie cu zeoliţii obişnuiţi. Astfel de mat...

The peculiarities of surface chemistry, functional groups and acid-basic properties of activated carbons obtained from vegetal raw materials by different methods of activation have been emphasized. Active carbons obtained from peach and plum stones by physical-chemical activation (with steam, aqueous solutions of sulfurous anhydride or ammonia) pos...

In this work certain methodological peculiarities for evaluation of surface acidic-basic functional groups of carbonaceous adsorbents were specified with procedures by joining titration methods.

The results of investigation of oenotannins content in the seeds of different grape varieties are presented in the paper. It was demonstrated that the oenotannins content depends on the grape variety as well as on the geographycal zone of grape cultivation. A new procedure for water sollubilization of oenotannins by depolimerization has been elabor...

The results of investigation of oenotannins content in the seeds of different grape varieties are presented in the paper. It was demonstrated that the oenotannins content depends on the grape variety as well as on the geographycal zone of grape cultivation. A new procedure for water sollubilization of oenotannins by depolimerization has been el...

Activated carbons (ACs) made from peach and plum stones were oxidized and impregnated with salts of Cu(II), Fe(III), Ni(II) and Cr(III). The chemically modified ACs, along with a commercial AC (S208c), were saturated with ortho- (OCP) and meta-chlorophenol (MCP) to investigate the potential for thermally regenerating the spent ACs. The thermal rege...

Modified active carbons were used for removal of hydrogen sulfide, ammonia and nitrite ions from water solutions. Obtained results demonstrate that active carbon oxidized with H2O2 following impregnation with Co(II) possesses higher adsorption capacity for NH4 + compared with unimpregnated samples. It was established that active carbon obtained fro...

Oxidation and impregnation treatments of activated carbons result in sorbents with selected properties and reduced surface areas. In this work, to investigate the effects of these methods on both the porous structure and surface chemistry, activated carbons derived from peach stones were oxidized with concentrated nitric acid and then impregnated w...

Several types of active and oxygenated coals obtained in micropilot plant by IR and UV-VIS-NIR spectral techniques, as well as by chemiluminescence, are characterized. The tests revealed the main changes induced during oxidation of a number of coals obtained from vegetable raw materials.

For the evaluation of vegetable oils and oenotanine obtained from grape, apple seeds and nut kernel some specific spectral techniques: UV-VIS-NIR-FTIR and chemiluminescence have been used. Corroboration of these experimental data emphasized the structural complexity and the antioxidative capacity of the systems studied.