Nitrophenols are carcinogenic, non-biodegradable pollutants in wastewaters from textile, paper and other industries. Cost-effective and environmentally friendly photocatalysts for degradation of such toxicants are magnetic nano-sized spinel ferrites. The research was aimed at establishing the effect of structure and cations distribution in tetrahedral and octahedral sublattices of ferrite spinels on adsorption-catalytic activity of CoFe2O4 (CF), Co0.5Mg0.5Fe2O4 (CMF), MgFe2O4 (MF) in photocatalysis and Fenton-like oxidation reactions. Nanosized spinels were synthesized by citrate combustion method and characterized by XRD, Mossbauer spectroscopy, FTIR, SEM, energy dispersive analysis and BET nitrogen adsorption-desorption technique. Oxidative degradation of 2,4-dinitrophenol by hydrogen peroxide was used to evaluate catalytic activity of spinels under differentiation of contributions of sorption, photocatalysis and Fenton-like reactions to overall degradation process. The reaction followed pseudo-first-order kinetic model with degradation efficiency of 79.5 and 98.3 % for CF and MF, respectively. The highest degree of pollutant degradation after four catalysis cycles without regeneration was characteristic of CMF. The observed stability of CF, CMF and MF in several cycles demonstrate their high catalytic potential for treatment of wastewaters containing phenolic compounds. Additionally, the study illustrated the possibility of synthesized spinels application as sorbents of inorganic toxicants from aqueous medium. The sorption capacity for heavy metal ions, activity of sorption sites per unit surface area, efficiency of purification increased in the order CF < CMF < MF allowing to extract from 19 to 58 mg/g of Cu2+ from water. The investigated materials reached sorption equilibrium within 20-80 min, successfully operated in several sorption cycles both without and under regeneration conditions, and were easily isolated for reuse and regeneration by external magnetic field.

The aim of the work was to develop and study new compositions for the treatment of natural wood based on used vegetable oil with the addition of nanosized silicon oxide to obtain a wood composite with improved properties. The basis of the developed impregnating compositions was used frying vegetable oil. Additives of nanopowders of amorphous and crystalline silicon oxide were introduced into the compositions at a dosage of 0.01 to 0.5%. To modify wood, a stable suspension of synthesized silicon oxide nanopowders in used sunflower oil was prepared. The processing of wood samples was carried out by the method of “hot-cold impregnation”. The obtained wood composites with the addition of nanosized silicon oxide had improved hydrophobic properties of wood (an increase in the contact angle by 30%), increased moisture and water resistance (by 11 and 14 times, respectively), as well as reduced swelling in the tangential and radial (5 times) directions in comparison with natural wood after 1 day of testing. The optimal dosage of silicon oxide nanopowders (0.01%) was chosen. A comparative evaluation of the use of amorphous and crystalline silicon oxides in impregnating compositions based on used vegetable oil was carried out using birch wood as an example.

Thermally stable perovskite-like SmFeO3 powders were obtained by the co-precipitation method using (NH4)2CO3 as a precipitating agent; their physicochemical, optical, and magnetic properties were characterized to preliminary evaluate their potential applications. It was found that a well-crystallized pure-phase SmFeO3 will be obtained when the calcination temperature (tc) reaches 850 degrees C. The average size of SmFeO3 crystallites was about 45, 55, and 64 nm for the SmFeO3-750, -850, and -950 samples, respectively. The orthorhombic structure was distorted, as evidenced by the varied unit cell volume (from 233.3510-3 to 233.0710-3 nm3) and microstrain (from 2.0210-3 to 0.00910-3) in dependence on tc (from 750 to 950 degrees C), respectively. The synthesized SmFeO3 samples exhibited paramagnetic properties, with the coercive field (Hc) in the range of 250-750 Oe. Moreover, the obtained materials have direct bandgap energies with values below 3.06 eV.

We obtained pine and birch biochars by carbonising sawdust at 500°C for 3 hours with a heating rate to the specified temperature of 10°C/min, with a fairly good yield for slow pyrolysis of 29% and 36% and particle sizes of up to 160 and 350 μm, respectively. Two-hour alkaline activation resulted in a decrease in particle size (20–60 µm for birch and 50-150 µm for pine coals), an increase in bulk and real densities, and a slight increase in pH. Using the energy dispersive analysis, we established the carbon basis of activated biochars and identified a tendency to an increase in the carbon content and a decrease in oxygen as a result of activation, which led to reduced O/C ratio of 0.258 for birch charcoal and 0.243 for pine charcoal. The kinetic sorption curves of the methylene blue dye on all studied coal samples were correctly described by a pseudo-second order model. The adsorption rate depended on the number of adsorption centres and was controlled by the contribution of the chemical reaction. A significant share of electrostatic interactions between the cationic dye and the negatively charged biochar surface could be expected. The sorption capacity of the initial and activated birch charcoal was twice higher than the corresponding pine samples. The Langmuir adsorption model correctly described the sorption of methylene blue on the studied biochars, which was confirmed by the high values of correlation coefficients. The efficiency of sorption purification from the cationic methylene blue on activated biochars from birch and pine reached 98 and 49%, respectively, which agreed well with the values of the adsorption capacity and sorption rates on these coal samples.

Nanocrystalline bismuth ferrite was synthesized using spray pyrolysis and citrate combustion methods. BiFeO3 samples were characterized by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopy, and energy dispersive X-ray spectroscopy. The citrate and spray pyrolysis samples of bismuth ferrite were tested as catalysts for the Fenton-like oxidative degradation of methyl orange. The effect of the synthesis method on the composition and morphology of bismuth ferrite particles and on the catalytic activity was established. The oxidative degradation of the dye in the presence of bismuth ferrite samples is satisfactorily described by pseudo-first order kinetics. The reaction rate constant for BiFeO3 synthesized by spray pyrolysis is 0.0072 min–1, while that for citrate BiFeO3 is slightly lower: 0.0049 min–1. The degree of degradation of methyl orange in 120 min is 7

Nanoscale magnetic spinel ferrites are attracting an increased attention as functional materials for catalysis and sorption. Such catalysts and sorbents are advantageous due to their chemical stability in aggressive media, their thermal stability, a large area of specific surface, and high saturation magnetization, which allows using them to create magnetically controlled functional materials. This article presents the results of the synthesis of nickel (II) ferrite nanopowder, its characterization, and a study of its catalytic and sorption activities towards methyl orange dye. X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were used to characterize nanocrystalline NiFe2O4 synthesized by citrate combustion. The nickel spinel was tested as a catalyst of Fentonlike reaction of oxidative degradation of methyl orange under UV irradiation of l = 270 nm. The study involved differentiation of oxidation during dye sorption on a NiFe2O4 nanoscale catalyst. The oxidative degradation of the pollutant under ultraviolet irradiation in the presence of a catalyst was satisfactorily described by a pseudo-first-order model, the rate constant of the reaction was 0.0191 min–1. The degree of methyl orange destruction reached 99% 150 minutes after the beginning of thereaction. A parallel experiment without the addition of hydrogen peroxide to the dye solution allowed assessing the sorption capacity of nanoscale nickel (II) ferrite. After 150 minutes, the concentration of the dye decreased by 7.5% due to its sorption, the equilibrium sorption capacity of NiFe2O4 was low (0.132 mg/g). This indicates that the methyl orange solution decolorizes mainly due to its catalytic oxidative degradation according to the Fenton reaction. This allows considering nanoscale nickel ferrite as a promising material for wastewater treatment by deep oxidation of organic pollutants

DyFeO3 nanoparticles were successfully prepared by a simple co-precipitation method at room temperature using 0.2

The work proposes the use of multi-walled carbon nanotubes in various concentrations treated in nitric acid (f-MWCNT) as a filler for urea-formaldehyde resin to produce birch plywood with improved physical-mechanical, water-resistant and thermal properties. The MWCNTs were characterized using transmission electron microscopy, IR and Raman spectroscopy, and the zeta potential was determined. The thermal stability of plywood on the UFR/f-MWCNT adhesive composition was assessed and a higher thermal stability of plywood was revealed when a nanofiller was added to the resin. The modulus of rupture increased by 62.7% and the modulus of elasticity by 113% with the addition of 1.5% f-MWCNT. A decrease in water absorption was established by 43%. A steady decrease in the emission of free formaldehyde from plywood was determined. The possibility of intermolecular interaction between the functional of f-MWCNT and urea resins has been established.

Pine sawdust, 0.5–1 mm in size, was made carbonized. The resulting biochar was activated. This activated KOH biochar was confirmed to be a better methylene blue dye sorbent than the original charcoal. The conclusion was made about the possibility of using the study results in the processing of timber industry waste into carbon sorbents for water treatment systems and ensuring environmental safety of production sites.

Interest in biochar as a sorbent for wastewater treatment, including for the extraction of heavy metal ions, is due to its properties: resistance to degradation, large area and significant negative surface charge, the possibility of generating reactive oxygen species under ultraviolet irradiation with the subsequent destruction of organic pollutants. The purpose of the study was the creation of a sorbent based on birch sawdust as sawmill wood waste as a result of directed physico-chemical modification of biochar, the determination of its characteristics and sorption capacity for copper ions. According to scanning electron microscopy data, simultaneous activation of birch sawdust carbonizate with KOH and ultrasound for 30 minutes contributed to an increase in the fraction of biochar particles with a size of 20-60 microns and the disappearance of biochar particles larger than 100 microns, an increase in bulk density was noted. An increase in the carbon content in biochar after activation and a decrease in the O/C molar ratio from 0.304 to 0.258 were established using energy dispersive analysis method. IR spectroscopy confirmed the presence of a number of surface oxygen-containing functional groups: hydroxyl, carbonyl, carboxyl, quinoid. The sorption of Cu2+ by modified coal increased by 2.2 times compared with the original birch sawdust carbonizate. Sorption isotherms of copper ions both by the initial and activated biochar were satisfactorily described by the Langmuir equation. Physical and chemical modification of biochar with KOH and ultrasound contributed to an increase in the capacity of the adsorption monolayer and the equilibrium constant. The sorption at pH=5.8 contributed to the deprotonization of oxygen-containing functional groups –COOH and –OH present on the biochar surface, which increased the adsorption of Cu2+ ions. The formation of Cu-O bond between carboxylate ions and Cu2+ was confirmed by shift at 1200 cm-1, corresponding to the stretching vibrations of the C-O bond in the carboxyl group, to the region of lower frequencies in the IR spectra of biochar samples after sorption. A larger shift was typical for the spectrum of B+KOH+US+CuSO4 sample, which was consistent with an increase in the sorption of copper ions by activated biochar.

Wood is a common natural polymeric material with hydrophilicity and low biostability with a limited service life. The article considers the issue of using a multicomponent composition (used motor oil, rosin, paraffin) for impregnating birch wood and giving it increased water resistance, bio- and dimensional stability. The possibility of recycling the used impregnated wood to obtain a biochar adsorbent was shown. The impregnating composition was characterized by the FTIR method to assess the possibility of interaction between the functional groups of the impregnating composition and wood. Moisture and water absorption decreased by more than 4 and 6 times. Volumetric swelling decreased by 57% relative to untreated wood, the effectiveness against swelling after 30 days was 46%. The high efficiency of the impregnating composition against the wood biodegradation has been established. The method of micro-X-ray tomography determined a high degree of filling of the anatomical structures of wood.

Due to their multi-functionality, spinel ferrites, both doped and undoped, are promising materials for a wide range of practical applications, including catalysis, sustainable production of hydrogen and СО2 deposition, electronic and magnet devices, as well as antibacterial agents. Recently, nanosized ferrites have been actively tested as catalysts in Fenton-like processes of deep oxidative degradation of organic substances in order to purify waste waters of different dyes, phenol and its derivatives, and antibiotics. The goal of this work was to establish the catalytic activity of СоFe2O4 nanopowder synthesisedusing citrate combustion in the reaction of oxidative degradation of 2,4-dinitrophenol upon the activation of the process with UV radiation. Using citrate combustion, we synthesised the impurity-free nanopowder of CoFe2O4 cobalt ferrite with the average size of particles of about 70 nm and a pronounced agglomeration of particles. The cobalt spinel was tested as a catalyst of Fentonlike reaction of oxidative degradation of 2,4- dinitrophenol with UV radiation of l = 270 nm. This process was differentiated with the sorption of dinitrophenol on a nanosized catalyst. The degree of degradation of 2,4-dinitrophenol in a Fenton-like reaction without the CoFe2O4 catalyst was 14 %, while in the presence of a nanosized catalyst it increased up to 80 %. The effective oxidative degradation of the pollutant was performed in a less acidic environment as compared to a classic Fenton process with a rather large initial concentration of dinitrophenol. This allowed considering the nanosized CoFe2O4 as a promising catalyst of Fenton-like of waste waters purification through deep oxidative degradation of toxins.

In this study, holmium orthoferrite ( o -HoFeO 3 ) nanoparticles were successfully synthesized by simple co-precipitation method without adding gelling organic polymers. Structures, morphologies, elemental composition, thermal, and magnetic properties of the product were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetry and differential scanning calorimetry (TG-DSC), and vibrating sample magnetometer (VSM). After annealing the precursors at different temperatures for 60 min, nanocrystrals with orthorhombic perovskite structure were obtained. Crystallite size ( D PXRD = 22.13–53.74 nm), particle size ( D TEM/SEM = 20–60 nm), and lattice volume ( V = 223.65–224.99 Å 3 ) increased with the annealing temperature. The optimal annealing temperature for obtaining the single crystalline phase of o -HoFeO 3 was ≥ 750 °C, and the o -HoFeO 3 crystalline phase remained stable at temperatures ≥ 1050 °C. The synthesized o -HoFeO 3 nanoparticles exhibited a uniform spherical shape, with a size of 20–60 nm, and exhibited the properties of a paramagnetic material at 300 K. Notably, the coercive force and residual magnetism of the synthesized material were much smaller than those reported in previous studies for similar materials. The experimental results in this work may provide fundamental support to the research and development of magnetic material.

In order to enhance the efficiency of heavy metal ion extraction from aqueous medium, new nanocomposite magnetic sorbents were synthesized on the base of natural zeolite (Zt) and nanoparticles of ZnFe2O4 (F). The composition, structure and physical–chemical properties of new composites with 2% (Zt-2F), 8% (Zt-8F) and 16% (Zt-16F) of zinc ferrite were characterized by XRD, BET adsorption–desorption of nitrogen, SEM with elemental mapping, TEM and magnetometry. The sorption capacity of materials was assessed towards Cu2+ ions in aqueous solutions, for which kinetic and equilibrium features of sorption were established. The maximal sorption capacity (amax, mg/g) of the studied materials increased in the order: Zt (19.4) < Zt-2F (27.3) < Zt-8F (30.2) < Zt-16F (32.8) < ZnFe2O4 (161.3). The kinetics of the sorption process followed a pseudo-second order kinetic model. The sorption equilibrium at zinc ferrite was successfully described by the Langmuir model, while the Freundlich model better fitted the sorption equilibrium on zeolite and composites. The efficiency of Cu2+ ion extraction from 320 mg/dm3 aqueous solution was 63% for composite Zt-16F and 100% for a sample of ZnFe2O4. It was established that the proposed composite sorbents provide the operation of several cycles without regeneration, they can be easily recycled with 0.1 N HCl solution and are capable of magnetic separation. The advantages of new composites and the proposed method of synthesis allow recommending these materials as effective sorbents of heavy metals from wastewater.

Recent studies have shown that nanomaterials, including carbon nanotubes, are associated with a wide range of effects on living organisms, from stimulation to toxic effects. Plants are an important object of such research, which is associated with the potential use of carbon nanomaterials in agriculture and environmental protection. At the same time, the specific mechanisms of formation of plant resistance to the effects of carbon nanotubes remain not fully understood, especially in woody plants. Therefore, we studied the effect of aqueous colloids of multi-walled carbon nanotubes (MWCNTs) with an outer diameter of 10–30 nm and a length of about 2 μm at a concentration of 1, 10, 50, and 100 mg/L on morphometric parameters and the level of expression of stress resistance genes in Betula pubescens Ehrh. and B. pendula Roth. plants in greenhouse conditions. The results showed an increase in the length and diameter of the shoot in the studied plants. The dry biomass of the leaf increased by 30%, the stem by 42%, and the root by 49% when using MWCNTs at a concentration of 10 mg/L. The expression of the stress resistance genes DREB2 and PR-10 significantly increased under the influence of 1 mg/L MWCNTs on plants of both species. At the same time, the use of 100 mg/L nanoparticles led to a decrease in the studied parameters in Betula pendula, which may be associated with the negative effect of MWCNTs in high concentrations. The revealed positive effects of low concentrations of MWCNTs on morphometric parameters and stimulation of stress resistance genes by nanotubes open up prospects for their use in woody plant biotechnology.

Microwave and ultrasonic radiation-activated synthesis of YVO4-based phosphors doped with Bi3+ and Eu3+ is proposed. XRD and LXRSMA results confirm the incorporation of Bi3+ and Eu3+ ions into the YVO4 crystal lattice. The particles of the obtained powders have a pronounced spherical shape with a predominant diameter in the range of 20–40 nm. For samples co-doped with Bi3+ and Eu3+, the band at λ = 616–620 nm (5D0→7F 2 3+ ) is the strongest in comparison with the other bands of the series 5D0→ 7FJ (J = 0, 1, 2, 3, 4), which indicates that the position of Eu3+ within the YVO4 matrix is considerably deviated from the centrally symmetric one. The Bi3+ ions have an effective sensitizing effect on Eu3+ radiation due to charge transfer from the 6s orbital of Bi3+ to the 3d orbital of V5+ and then to the Eu3+ ion. The efficiency of energy transfer is about 50

Following the co-precipitation method for producing terbium orthoferrite (TbFeO3), the final products were denoted as TbFeO3-650, -750, and -850. A single-phase of orthorhombic TbFeO3 crystals (o-TbFeO3) was obtained with a calcination temperature of up to 850 degrees C, while in the range of 650-750 degrees C there was still a small amount of terbium and iron oxide phases. The average size of o-TbFeO3 crystallites for the TbFeO3-850 sample was about 76 nm and was larger than that of TbFeO3-650 (similar to 45 nm) and TbFeO3-750 (similar to 47 nm). The o-TbFeO3 crystal structure in all samples was found to be distorted. In the applied field from -15 to +15 kOe, all of the samples had low values of coercive field (5-11 center dot 10(-3) Oe) but high values of net magnetization (2.06-2.40 emu center dot g(-1)); the samples appeared to behave as paramagnetic materials. It was shown that the TbFeO3-850 sample has slightly better magnetic properties than the two others. An average grain size of about 79 nm was found in the TbFeO3-850 sample, which exhibited a morphology of sphere-like shapes with highly agglomerated grains. The TbFeO3-850 sample demonstrated a high absorbance at wavelengths of 400-600 nm, with a direct bandgap of about 2.68 eV.

By using the co-precipitation method, the orthorhombic structure of YbFeO3 (o-YbFeO3) was obtained. To investigate the effect of different synthesis conditions on the resulting samples, NaOH (SH) and (NH4)(2)CO3 (AC) were used as precipitants, and a temperature range of 750-950 degrees C (t(c)) was applied for calcining the assynthesized products. Depending on the synthesis conditions, the samples can be monophasic or diphasic and exhibit crystalline structure distortion. As the t(c) increases, the average size of o-YbFeO3 crystallites increases, which is in the 30-60 nm range. The samples' magnetism was not significantly affected by the synthesis conditions, and all displayed paramagnetic behavior, as evidenced by low values of coercive force (0.02-150.01 Oe) and net magnetization (0.41-0.54 emu.g(-1)); in this regard, the YbFeO3-AC-850 sample appeared to be superior, and the oxygen element preferred to face the sample's surface. The sample's morphology consists of ovalspherical-like grains with high agglomeration.

Water pollution and deterioration of air and water quality is a rapidly growing problem directly related to the generation of waste water and the accumulation of significant amounts of wastewater sludge (WWS). One of the methods for recycling WWS is their pyrolytic processing into biochar adsorbents for purification from various pollutants. The type of adsorbent and its properties play a key role in the efficiency of the purification process, which explains the relevance of the search for alternative materials for water treatment processes. The purpose of the study was to create a biocarbon sorbent during the pyrolysis of wastewater sludge and determine its sorption capacity for the methylene orange dye. To obtain samples of biocarbon sorbent, dried and crushed samples of wastewater sludge were exposed to a temperature of 500 °C for 1.5 hours in a vacuum chamber with a heating rate to a given temperature of 5°C/min. Elemental analysis of the resulting sorbent allowed to establish a decrease in the content of carbon, oxygen, and sulphur: for C by 2.50 at.%, for O by 9.91 at.%, for S by 0.4 at.%, relative to WWS. Scanning electron microscopy confirmed a significant reduction in the particle size of biochar compared to the original WWS sample. In the initial WWS sample, after the sample preparation stage, the dispersion of particle sizes was 10-70 µm, and after pyrolysis of the sediment, the dispersion decreased to the range of 10-45 µm. The percentage of biochar yield was calculated, constituting 42% of the weight of the initial WWS and studies on the sorption of methylene orange were carried out. The sorption capacity of biochar for the anionic dye methylene orange after 120 min of sorption was 4.9 mg/g, the degree of solution purification reached 82%. The kinetics of dye sorption was correctly described by a pseudo-second-order equation and indicated the polymolecular nature of sorption.