4-Dialkylamino-2,5-dihydroimidazol-1-oxyls with Functional Groups at the Position 2 and at the Exocyclic Nitrogen: The pH-Sensitive Spin Labels

Local acidity and electrostatic interactions are associated both with catalytic properties and the adsorption activity of various materials, and with the vital functions of biomolecules. The observation of acid–base equilibria in stable free radicals using EPR spectroscopy represents a convenient method for monitoring pH changes and the investigation of surface electrostatics, the advantages of which are especially evident in opaque and turbid samples and in porous materials such as xerogels. Imidazoline nitroxides are the most commonly used pH-sensitive spin probes and labels due to the high sensitivity of the parameters of the EPR spectra to pH changes, their small size, and their well-developed chemistry. In this work, several new derivatives of 4-(N,N-dialkylamino)-2,5-dihydrioimidazol-1-oxyl, with functional groups suitable for specific binding, were synthesized. The dependence of the parameters of their EPR spectra on pH was studied. Several showed a pKa close to 7.4, following the pH changes in a normal physiological range, and some demonstrated a monotonous change of the hyperfine coupling constant by 0.14 mT upon pH variation by four units.

Adsorption of the Petrochemical Pollutants Released at the Small Vehicle-Service Facilities on the Coal Refinery Sludge/Pyrocarbon Compositions

It has been proven that the use of coal-like adsorbents with the mosaic and hydrophobic surface structure is efficient in cleaning thewastewater from a wide range of pollutants under the condition of their uncontrolled release from various small enterprises. Thisrange includes such environmentally dangerous agents as petrochemicals and other pollutants formed at car filling, carwash stationsor other similar facilities. Technical pyrocarbon and the coal refinery sludges are readily available waste materials with high porosity,which exhibit some adsorption activity and can be utilized in water/wastewater treatment solutions. Then the adsorbents can be eitherdisposed of at the landfill areas or incinerated as components of some secondary fuels. The highest adsorption performance is achievedfor the sorbent mixture of the refinery sludges and technical pyrocarbon with the ratio of the components 4:1.If the wastewater is flowing through this composition, the degree of petrochemicals removal reaches 75-80% for the mixture sludge/technical pyrocarbon, while the pure pyrocarbon ensures the removal degree of 15-20% only. Though adsorption efficiency under stationary conditions (keeping the adsorbent and the wastewater in contact inside some decontamination pond/vessel for at least 24 h) ishigher, this option is hard-to-realize for a small car service/wash station. As an alternative, comparatively small wastewater cleaningcartridges filled with the 4:1 mixture of coal sludge and technical pyrocarbon can be recommended for preliminary decontaminationof the wastewater formed at such enterprises before their discharge to the local municipal sewerage lines.

Optimisation of conditions for deacetylation of chitin-containing raw materials

The paper describes the differences between chitosan and chitin, and reviews works by foreign scientists on obtaining chitosan from various raw materials. Methods of modifying chitosan and obtaining combined sorbents have been analysed. It has been studied whether chitosan is applicable in the technology of wines and alcoholic beverages as a sorbent. The purpose of the study was determining the optimal conditions of the deacetylation stage to obtain chitosan with the best sorption properties from Aspergillus niger biomass. A three-factor experiment has been carried out. It involved obtaining 27 samples of chitosan using sequential four-step acid-base hydrolysis under various conditions of the deacetylation stage. The deacetylation process was optimised under alkaline conditions depending on the alkali concentration, processing temperature, and exposure. For each of the samples obtained, the adsorption activity, specific surface area, and distribution coefficient in the sorbent–sorbate system have been determined. The degrees of deacetylation of all chitosan samples have been determined by potentiometric titration. The study has resulted in determining the optimal conditions for the deacetylation stage: processing temperature 110–130°C, sodium hydroxide concentration 27–36 g/dm3, exposure 45 to 65 minutes. The sample deacetylated at the temperature 120 °C, alkali concentration 30 g/dm3, and exposure 45 minutes has shown the best adsorption activity values: the adsorption activity for methyl orange 347.96 mg/g, the specific surface area of the sorbent samples 0.52·105 m2/g, the distribution coefficient in the sorbent–sorbate system 3.29·10-3 ml/g. This sample had the highest degree of deacetylation, 43.6%. The sample has been analysed using IR spectroscopy, and its main characteristic frequencies have been studied. It has been concluded that the sample obtained was equivalent to the reference chitosan

Effects of various media on micellization, adsorption and thermodynamic behaviour of imipramine hydrochloride and antimicrobial surfactant mixtures

The effect of various media (aqueous, NaCl, urea (U) and thiourea (TU)) on the micellization and adsorption activity of varied mixtures of imipramine hydrochloride (IMP) and benzethonium chloride (BZCl) is investigated via tensiometry. In an aqueous medium, the interactions between IMP and BZCl are also evaluated using UV–visible and FTIR spectroscopy. The interaction between components increases with increased mole fraction ( α 1 ) of BZCl in the mixed system (IMP + BZCl). Different parameters, such as micellar and the mixed monolayer component composition, the interaction parameters of the solution and the interface, the activity coefficients of the components in solution and at the interface, and thermodynamic parameters, are computed using different proposed theoretical models (i.e. Clint, Motomura, Rubingh and Rosen). The cmc values obtained for the pure components and mixtures (IMP + BZCl) of all the compositions are found to be less in NaCl than in the aqueous solution while found more in the presence of U or TU. TU is more effective in increasing the cmc of the pure and mixed systems than U. The Gibbs free energy ( Δ G mic ∘ ) values of the studied pure and mixed systems are negative, showing the spontaneous nature of the reaction.

Synthesis and Characterization of CuO Nanoparticles and CuO/PVA-PVP Nanocomposites: Adsorption Activity for Malachite Green (MG) Dye and Antibacterial Property in Wastewater Treatment

Contaminated waterways, particularly effluent from the dye industry, are one of the major issues today. Among various methods adsorption being the most straight forward, low-cost, effective, and successful to treat such effluents. For this purpose, Copper oxide nanoparticles (CuO) and Copper oxide nanoparticles embedded within Polyvinyl alcohol (PVA) and Polyvinyl pyrrolidone (PVP) mixed polymer (CuO/PVA-PVP) were synthesized using precipitation methods and different analytical techniques such as dynamic light scattering (DLS), powdered X-ray diffraction (XRD), fourier-transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) were used to characterize morphology and size. Synthesized nanomaterials were used for the adsorption of malachite green (MG) dye in aqueous solution by the batch adsorption method. Various experimental conditions e.g., contact time, concentrations, pH, were optimized to obtain best adsorption outcome. Adsorption kinetics and isotherm suggested that it follows Pseudo-second-order-kinetic and Freundlich isotherm. The invitro antibacterial activity was investigated using disk diffusion and minimum inhibitory concentration (MIC) test against Staphylococcus aureus (S.aureus), a gram positive and Escherichia coli (E.coli), a gram negative bacteria, where both the synthesized nanoparticles showed a decent antibacterial activity against both the bacterial strain.

INVESTIGATION OF THE THERMODYNAMIC CHARACTERISTICS OF THE EXTRACTION OF COPPER IONS FROM AQUEOUS SOLUTIONS USING ACTIVATED CARBON

Изучение термодинамических и кинетических характеристик позволяет более эффек- тивно использовать углеродные адсорбенты в технологических процессах, чем поддерживается тех- нология их использования на оптимальном уровне. В работе изучалась адсорбционная активность углеродных нанопористых материалов, рассчитывались кинетические характеристики процесса ад- сорбции, термодинамические характеристики (энергия Гиббса, энтальпия, константа адсорбции) адсорбции ионов меди на активных углях, полученных на установках (модульная пиролизная реторт- ная установка) и УВП (углевыжигательная печь). Установлено, что процесс идёт самопроизвольно, характер адсорбционного взаимодействия экзотермический. Адсорбционные равновесие достигается меньше чем за 15 мин. The study of thermodynamic and kinetic characteristics allows more efficient use of carbon adsorbents in technological processes. Thus, keeping their use at an optimal level. The adsorption activity of carbon nanoporous materials was studied, the kinetic characteristics of the adsorption process, thermodynamic characteristics (Gibbs energy, enthalpy, adsorption constant) of copper adsorption on activated carbons obtained at MPRP and CK installations were calculated in this work. It was found that the process is spontaneous (G <0). The nature of the adsorption behavior is exothermic. Adsorption equilibrium is achieved in less than 15 minutes.

Adsorption of H2S from Thermal Water Using Clinoptilolite

The goal was to study and develop the composite adsorbents to uptake H2S from thermal water on the base of natural zeolite clinoptilolite (CL) from deposit of Georgia and activated carbon (AC). Cation-modified forms of CL have been prepared by wet-milling method. The crystalline structure and content of prepared adsorbents have been studied by X-ray diffraction (XRD) technique, IR-and AAS methods. Adsorption experiments carried out varying the ratio zeolite: AC, composite: solution, duration of contact, granulation degree. The results obtained showed that modification of CL by ion-exchanging method with metal ions (Zn2+, Fe3+, Mn2, Cu2+) has improved the adsorption capacity. Adsorption equilibrium reached in seven-fifteen minutes, and adsorption activity grows in a row: DeCL < CL < CuDeCL < MnDeCL < FeDeCL < ZnDeCL < AC/CL. The sorption capacity ranged from 0.68 mg/g to 28.17 mg/g. pH of thermal water before sorption was 8.97 and in filtrates changed in very wide ranges – from 10.44 until 3.55 depending on type of modification. Presence of multivalent cations of metals in the zeolite confirmed to be an essential factor determined the adsorption activity in relation to H2S, adsorption occurs via both physical sorption and chemisorption. Most active was composite AC/CL with ratio AC:CL, equal 3:2. The difference for H2S between decationated and cation-exchanged forms of CL may be explained by the change of surface potential. Polarity of zeolites depends on Si/Al ratio, which by-turn depends on conditions of acid treatment.

Characteristics of diatomite-alginate-Fe3O4 composite as a phosphate adsorbent

Technological approaches to the use of diatomaceous earth as a raw material for the creation of composite adsorbents for wastewater treatment from phosphate ions are analysed. It is shown that the developed surface of diatomite can be used to create a granular adsorbent, and iron (III) oxides (magnetite, goethite, lepidocrocite, ferrihydrite, hematite and goethite) are environmentally safe, cheap, economically feasible modifiers. Emphasis is placed on the possibility of obtaining magnetic granules due to the formation of magnetite. The use of the deposition method for the formation of the applied granular adsorbent is proposed. The influence of diatomite concentration on the static strength of granules was established. It is determined that the diameter of the nozzle is also an important factor. The selected technical solutions are aimed at solving the problems of granule hardening and ensuring high adsorption activity. Experimental studies of the synthesis and granulation of the composite adsorbent alginate - diatomaceous earth - magnetite have shown that an increase in the content of diatomaceous earth leads to a natural increase in the size of the granules. When increasing the diameter of the nozzle from 1.5 mm to 3.5 mm, for example, the size of the granules 1.5-4.0 (dc = 1.5 mm), 2.0-5.0 mm (dc = 3.0 mm) and 2.5-5.0 mm (dc = 3.5 mm). The diatomaceous earth content of more than 20% does not allow to carry out high-quality granulation on the experimental installation due to the increase in the viscosity of the suspension. The relationship between the size of gel granules and dried. The process of application of the active magnetic phase of the adsorbent is investigated. The dependence of the quality of the granulation process on the solid phase content is established. The measured static strength of the adsorbent granules is in the range of 17 - 25 kPa. It is established that the composite adsorbent with the applied layer of magnetite has magnetic properties. The adsorption of PO43- anions from aqueous solutions was studied. For the adsorbent alginate - diatomite and alginate - diatomite - Fe3O4 - the adsorption capacity is 4 and 9 mg PO43- / g, respectively. The obtained composite adsorbents have a set of functional properties that are promising for use in modern water purification and purification systems.

In Vitro Anti-Orthohantavirus Activity of the High-and Low-Molecular-Weight Fractions of Fucoidan from the Brown Alga Fucus evanescens

The Hantaan orthohantavirus (genovariant Amur–AMRV) is a rodent-borne zoonotic virus; it is the causative agent of haemorrhagic fever with renal syndrome in humans. The currently limited therapeutic options require the development of effective anti-orthohantavirus drugs. The ability of native fucoidan from Fucus evanescens (FeF) and its enzymatically prepared high-molecular-weight (FeHMP) and low-molecular-weight (FeLMP) fractions to inhibit different stages of AMRV infection in Vero cells was studied. The structures of derivatives obtained were determined using nuclear magnetic resonance (NMR) spectroscopy. We found that fucoidan and its derivatives exhibited significant antiviral activity by affecting the early stages of the AMRV lifecycle, notably virus attachment and penetration. The FeHMP and FeLMP fractions showed the highest anti-adsorption activity by inhibiting AMRV focus formation, with a selective index (SI) > 110; FeF had an SI of ~70. The FeLMP fraction showed a greater virucidal effect compared with FeF and the FeHMP fraction. It was shown by molecular docking that 2O-sulphated fucotetrasaccharide, a main component of the FeLMP fraction, is able to bind with the AMRV envelope glycoproteins Gn/Gc and with integrin β3 to prevent virus–cell interactions. The relatively small size of these sites of interactions explains the higher anti-AMRV activity of the FeLMP fraction.

Computational Study of the Adsorption of Phosphates as Wastewater Pollutant Molecules on Faujasites

The adsorption of sodium dihydrogen phosphate (NaH2PO4) onto X- and Y-type faujasite zeolites was computationally studied using the Density Functional Theory (DFT) method. The structures were modeled using the Materials Studio software. The Si/Al ratios for the X- and Y-type zeolite models were 1.2 and 2.5, respectively. The central pore of the zeolite provided a more favorable coordination for adsorbing NaH2PO4. Full molecular optimization and adsorption energy calculations were performed using the VASP code. The adsorption was more effective on zeolite Y, with an adsorption energy of 161 kJ/mol, compared to the zeolite X system, with an adsorption energy of 31.64 kJ/mol. This calculated value for X-type faujasite was found in the interval of the adsorption energy of H2PO4− on hydrated Fe oxide (94.4 kJ/mol) and modified polyether sulfone (22.5 kJ/mol), and the calculated adsorption energy of the molecule on Y-type faujasite coincides with the reported value for this adsorbate on Mg/Ca-modified biochar structures. The molecular conformations of the adsorbate on the two studied models are very different, so the difference between the adsorption energy values of each type of zeolite model is comprehensible. On the one hand, the oxygen atoms of the molecule formed a bidentate complex with the hydrogen atoms of the pore in the X-type faujasite model, and the O-H distance was 1.5 Ǻ. On the other hand, an adsorbed oxygen atom of the phosphate was placed on a hydrogen atom at site II of the Y-type faujasite zeolite, and two of the hydrogen atoms of the phosphate were placed on the oxygen atoms. The Bader analysis results indicated that the negative charge of the phosphate anions was delocalized on the zeolites protons. The hydroxy groups of the phosphate form bonds between their hydrogen atoms and the oxygen atoms of the zeolite porous structure; therefore, we concluded that these sites have an alkaline character. The aim of this study was to include a computational analysis of possible phosphate adsorption mechanisms in faujasite zeolites that can be confirmed by experimental tests, and hence contribute to the generation of new technologies for capturing pollutant molecules in wastewater. The results are in agreement with the experimental information concerning the influence of pH on the adsorption activity of phosphate adsorption on zeolites.