Ion Exchange Treatment Research Articles

Improving the wear performance of feldspathic veneering porcelain by ion-exchange strengthening

ObjectivesThe present study examined the effects of Na+→K+ ion-exchange on the wear performance of feldspathic veneering porcelain. MethodsBar and disk specimens were prepared using IPS classic as the feldspathic veneering porcelain. After ion-exchange by immersion of the specimens in melted KNO3 at two temperatures for different time-periods, the bars were tested for flexural strength and Vickers surface hardness. The disks were paired with zirconia antagonists and tested with a pin-on-disk tribometer with 10 N for 70☓104 wear cycles in artificial saliva. Wear analysis of the porcelain and zirconia was performed using 3D profilometer and analysed with one-way analysis of variance and Tukey’s post-hoc pairwise comparison procedures. Worn surfaces were examined with scanning electron microscopy. ResultsThe feldspathic veneering porcelain exhibited strong time-dependent wear behaviour, with typical running-in and steady wear stages. Ion-exchange treatments at 380 °C and 440 °C both enhanced the mechanical properties, decreased the wear rates of running-in wear and steady wear. The wear performance of porcelain treated by ion-exchange at lower temperature (380 °C) was improved significantly, especially reducing the wear rate of the running-in stage. ConclusionA thicker ion-exchange layer with less stress relaxation may be obtained by ion-exchange at lower exchange temperature for a long processing time. Such a protocol improves the wear performance of the porcelain effectively. Clinical significanceRestorations with veneering porcelain may fail prematurely due to excessive wear. It important to improve the wear performance of the porcelain. Ion-exchange has the potential to strengthen dental veneering porcelain. Understanding the effect of ion-exchange on the wear performance of porcelain provides insight improving the wear performance of these restorations.

Problems of Ion-Exchange and Membrane Water Treatment Technologies in Power Engineering

The demineralization of clarified water is carried out in TPPs, NPPs, and combined-cycle boiler houses in Russia, as a rule, using a chemical or membrane method. Conventional chemical demineralization prevails, and the number of reverse osmosis plants is constantly increasing. When choosing the demineralization technology, the main criteria are economic. When comparing the reduced costs for water demineralization, chemical ion exchange methods take precedence over others for low-mineralized waters prevailing in the central and northern parts of Russia. For medium-mineralized waters, the economic indicators of ion-exchange and reverse osmosis demineralization are close. In terms of environmental performance, membrane water treatment technologies have significant advantages over the ion-exchange method; however, they require more thorough water pretreatment and are characterized by an increased sewage flow rate of up to 40% of the capacity. The introduction of more advanced technologies on conventional water treatment plants with parallel-flow filters reduces water consumption for plant demand, ion exchangers and reagents, primarily acids, and alkalis. This article uses the results of a survey of water treatment plants at some TPPs. Technical and economic indicators are given for groups of power plants that are grouped according to the same principle of water treatment technology. It is concluded that conventional chemical water demineralization plants with straight-flow filters have not exhausted their capabilities. Counter-current ionization technologies can successfully compete with conventional installations, provided domestic enterprises master the production of complete filters, including the automatic control system. Membrane water demineralization technologies can be effectively used in the energy sector for the development of industrial design, application, and process flow tests’ regulations for reverse osmosis plants.

Na2Ti3O7 nanowires with TiO2 and N-doped carbon dual-shells as binder-free electrodes for efficient sodium storage

Insufficient electronic/ionic conductivities and structural deformations upon sodiation/desodiation of layered Na2Ti3O7 severely hinder its full application in sodium-ion batteries. Na2Ti3O7 nanowires with TiO2 and N-doped carbon dual-shells are synthesized by hydrothermal synthesis to construct conductive interpenetration network anode for efficient sodium storage. The Na2Ti3O7-based interpenetrating network is sequentially subjected to controllable H+-Na+ ion exchange, dopamine/pyrrole modification, and thermal treatment to form the Na2Ti3O7@TiO2@N-doped carbon nanowires. Because of the rigid TiO2 shell to protect the Na2Ti3O7 core, the nitrogen-doped carbon shell with high specific surface area to enhance the conductivity, and the interpenetrating network to provide direct and fast diffusion pathways, the resultant NTO@TiO2@N-doped carbon electrode exhibits excellent electrochemical performances. Even at a high current density of 80 C (1 C = 177 mA g−1), the reversible capacity of the electrode is up to 78.3 mA h g−1, 6.6 times that of bare Na2Ti3O7 electrode. Further kinetic analyses of the CV curves at various scan rates reveal that the pseudocapacitive process contributes as high as 88.4% of the total capacity at the high scan rate of 10 mV s−1.

Visible light active titanoniobate nanosheets for efficient photocatalytic H2 production from water

Titanoniobate nanosheets with thickness down to a few nanometers have been prepared by ion exchange and subsequent exfoliation treatment on a bulk layer compound KTiNbO5. Superior photocatalytic H2 production activity has been realized on these nanosheets, surpassing their mother compound KTiNbO5. More interestingly, their photocatalytic activity has been successfully extended into visible light region when Cr/Nb co-dopants are introduced into nanosheets. The Cr/Nb modified nanosheets show apparent quantum efficiency as high as 2.75% at 420 ± 20 nm for H2 production, outperforming a number of doped metal oxides photocatalysts. Such high photocatalytic activity origins from their tiny thickness and a much enlarged surface area that favors charge separation and transfer. Their little dependence on cocatalyst for H2 production suggest that dopants Cr may also serve as catalytic reaction sites as a substantial fraction of Cr dopants are accommodated at the surface. This facile approach to fabricate ultrathin 2D semiconductor as well as versatility of doping strategy open new playground for the design and development of efficient visible light active photocatalysts.

CATALYST SYNTHESIS FOR THE PROCESS OF LIQUID-PHASE ALKYLATION OF BENZENE BY ETHYLENE

As a result of the research, a catalyst was synthesized for the alkylation of benzene with ethylene based on zeolite Y without binders. To obtain the catalyst НY-BS, the zeolite NaY-BS, which does not contain binders, was used with a crystallinity level close to 100 % and a SiO2 / Al2O3 mole ratio of 5.5. The zeolite was converted to the acid H+-form by replacing Na+ cations with NH + in three stages of ion exchange in an ammonium nitrate solution with a concentration of 25 g/dm3 (in terms of NH +). Each ion exchange treatment was carried out at a temperature of 70 °C for 1.0 h and a ratio of zeolite (g) / solution (cm3) equal to 1/7. The treatments were alternated with calcinations in air at a temperature of 600 °C for 3 h. After the last ammonium treatment, the granules were washed with demineralized water, dried and calcined in air at 600 °C for 3 h. Using the synthesized catalyst, the reaction of alkylation of benzene with ethylene is carried out at a temperature of 200 °C, a pressure of 2.5 MPa, a molar ratio of benzene: ethylene of 5 : 1, a volumetric flow rate of benzene of 5 h-1. The catalyst provides a high content (12,77 wt. %) of ethylbenzene in the alkylate.

Enhanced intercalation of organo-muscovite prepared via hydrothermal reaction at low temperature

Muscovite clay is an ideal reinforcing filler due to its high-aspect ratio. However, it does not swell in water, making it hard to be treated and intercalated. In this study, ion exchange treatment is carried out on muscovite clay using cetyltrimethylammonium bromide (CTAB) cations via two-step intercalation method. The intercalation steps included: inorganic–inorganic ion exchange treatment and inorganic–organic ion exchange treatment under hydrothermal conditions. The intercalation of muscovite particles was examined with various techniques to analyse the physical and chemical changes. Furthermore, the hydrothermal conditions for effective $$\hbox {CTA}^{+}$$ ion intercalation within muscovite interlayers prepared via the hydrothermal process at low temperature, $$180{^{\circ }}\hbox {C}$$ , under different hydrothermal reaction times and CTAB/Li-Mus mass ratio were investigated. Fourier transform infra-red (FTIR) analysis revealed that the $$\hbox {CTA}^{+}$$ ions are diffused into the interlayers of aluminosilicate and formed a strong electrostatic bond with the clay surface. X-ray powder diffraction analysis showed that the interplanar spacing in the organo-muscovite samples is almost identical as the hydrothermal reaction time is prolonged beyond 12 h. An optimum limit of the CTAB to Li-Mus ratio is observed as the $$d_{002}$$ plane spacing is increased with an increase of the mass ratio of CTAB to Li-Mus up to 1.0 C and decreased with a further increase in the mass ratio. In addition, the intercalated $$\hbox {CTA}^{+}$$ chains are homogenously distributed and formed a paraffin-like arrangement in the muscovite clay. Besides, the structure of aluminosilicate layers is not affected or damaged after both treatments according to FTIR analysis.

Eco-efficient treatment of ion exchange spent brine via electrodialysis to recover NaCl and minimize waste disposal

Natural organic matter (NOM) is removed from potable water for aesthetic, operational and indirect health concerns. NOM removal via ion exchange (IX) resins is receiving increasing attention owing to its simple operation. However, production of a spent brine during IX regeneration is the main drawback due to strict discharge regulations and limited and costly brine management options. In this study, the viability of desalinating the IX brine was assessed via electrodialysis (ED). ED desalination of the IX brine led to the production of highly pure NaCl and NOM-rich solutions which can be used for the IX regeneration and agricultural applications, respectively. Of particular interests were the impacts of the membrane permselectivity and implementation of pulsed electric field (PEF) on membrane fouling, desalination, purity of the NaCl solution and energy consumption. Our results demonstrated that ED desalination with monovalent ion permselective membranes consumed approximately 2 Wh per g of produced NaCl, achieved 88.8% desalination, produced pure NaCl solution with negligible membrane fouling. Furthermore, for the first time, we demonstrated that the PEF-ED intensified the process and decreased membrane fouling only when the conventional ion-exchange membranes were used; while no significant difference was detected when the PEF-ED was operated with the monovalent ion permselective membranes.

Enhanced bio-oil upgrading in biomass catalytic pyrolysis using KH-ZSM-5 zeolite with acid-base properties

Biomass catalytic pyrolysis has been investigated using wheat straw, previously subjected to acid washing to remove the mineral matter, as raw material with the goal of producing upgraded bio-oils with potential applications as liquid biofuels or as a source of bio-based chemicals. The catalyst employed consisted in zeolite ZSM-5 having nanocrystalline properties to enhance the accessibility towards the active sites, which was partially ion exchanged with K+ cations (KH-ZSM-5). Characterisation of this catalyst denoted that, although most of the strong acid sites were removed during the ion exchange treatment, it possesses a well-balanced combination of acid and basic properties. The biomass catalytic pyrolysis tests were performed in a two-step (thermal/catalytic) fixed bed reactor operating with temperatures of 550 and 450 °C, respectively, and different catalyst to biomass ratios (C/B). Compared with the parent acidic zeolite, the KH-ZSM-5 sample exhibited lower activity for the conversion and upgrading of the bio-oil. However, the removal of most of the strong acid sites by ion exchange with K+ resulted in a more efficient deoxygenation pathway, with lower contribution of decarbonylation. Moreover, the KH-ZSM-5 catalyst showed a reduced extension of cracking reaction into gases and of coke formation, whereas it promoted the conversion of the oligomeric species present in the bio-oil. As a consequence, the KH-ZSM-5 sample led to a more favourable relationship between the bio-oil oxygen content and the bio-oil yield when varying the C/B ratio in respect to the parent H-ZSM-5 zeolite.

Parameters of the Porous Structure Formed as a Result of the Ion-Exchange Treatment of Potassium-Barium Silicate Glass in a Sodium Nitrate Melt

Parameters of the Porous Structure Formed as a Result of the Ion-Exchange Treatment of Potassium-Barium Silicate Glass in a Sodium Nitrate Melt

Operating Experience with Fire Resistant Turbine Control Fluid at Ramin Power Plant

In the last 30 years, the phosphate ester fire resistant fluid, OMTI, has been used in the electrohydraulic control systems at Ramin power plant. Difficulties in obtaining supplies of the fluid led to efforts to extend its service life of the fluid by on-site conditioning and, eventually, to searching for a replacement. This paper surveys the operating experience obtained during the past ten years with the different forms of treatment and the replacement of OMTI by an alternative phosphate ester fluid. Different methods for conditioning of waste oil has been used from alkaline washing to ion exchange treatment. In alkaline washing process, an aqueous potassium hydroxide (KOH) solution was used to neutralise the acidity of the fluid. Any potassium soaps that are formed partition into the aqueous phase and can then be moved. Since it was done on a small-scale batch process, a static separation process was used. But in ion exchange treatment adsorption of acidic material of waste oil on ion exchange resins was used for reclamation of the oil. In view of concerns expressed over the conditioning of the used fluid and trade restrictions on purchasing the new fluid, the availability of a phosphate ester fire–resistant fluid from other sources was investigated and a different fluid, Turbex F46, was identified as potentially suitable.

Industrial experiment on electrodialized separation of highly concentrated multicomponent technological solutions at thermal power plants

The main sources of highly concentrated multicomponent technological solutions at thermal power plants (TPPs) are water treatment plants. Analysis of operation of the ion-exchange water treatment plant at the Nizhnekamsk Thermal Power Plant-1 showed that half of alkali supplied to regeneration of the anion-exchange alkali filters is not used, but is discharged for neutralization and then to wastewater. Due to the fact that the cost of alkali used in technological processes is quite high, it is economically feasible to process the alkaline waste with the alkali extraction and its reuse in the production cycle. The article presents the experimental results on the electro-membrane separation of alkaline waste regeneration solutions and wash water after anion-exchange filter regeneration. The revealed differences in the selectivity of various ion transfer through the electrodialysis apparatus membranes, depending on time and amount of transmitted electricity, allowed us to establish the possibility of obtaining an alkaline solution purified from impurities.

The composition of natural waters of some source rivers of the republic of Uzbekistan, used in the thermal power engineering and the results of the experimental researches at preliminary and ion exchange treatment of water

The article describes the possibility of use of the natural waters for generation of steam at thermal electric power stations. The chemical composition of some source rivers of the Republic of Uzbekistan is provided as well as its influence to the processing of water and contamination of the steam in the thermal energy engineering. The conditions of the preliminary chemical treatment of the natural water at TashTPP with the use of aluminum sulphate are described, as well as the experimental unit for production of the coagulant in the preliminary treatment and clarification of water; the experimental data on treatment of water with ions of chloride using the new ionites of type ASH-64 and ASH-64M, which were synthetized by the scientists of the Tashkent national university.

Очистка сточных вод гальванических цехов от ионов меди модифицированным карбонатным шламом

The article presents a technique of the granulated sorption material production based on the chemical water treatment slurry. The sorption has been studied in statical and dynamic conditions. The sorption effectiveness by copper ions was 90.5 %. The isotherm of adsorption and a curve of adsorption in dynamic conditions of cations of copper has been plotted by the granulated material. During the experiment the dynamic exchange capacity, full exchange capacity of the granulated material has been determined. The filtrate quality indicators in water passage through sorption material loads in accordance with MPC of domestic drinking and recreational purposes water bodies. The granulated sorption material extract was tested for acute lethal toxicity for Poecilia Reticulate Peters fish and Daphnia Magna Crustacea. The obtained results affirmed that the granulated sorption material was not practically hazardous and did not bring secondary pollution to wastewaters. The authors have presented a technological scheme of electroplating wastewaters ion-exchange treatment.

Blue/red dual color up-conversion emission from Tm3+, Yb3+ co-activated nephelline particles derived from LTA zeolites

Up-converted blue/red dual color emitting Tm3+, Yb3+ co-activated crystalline phosphor derived from LTA zeolites have been fabricated via a facile, highly controllable, and cost-effective method, that is, the combination of ion exchange and thermal treatment in air. Under the 980 nm laser excitation, the Tm3+,Yb3+ co-activated nepheline phosphor powders showed bright blue (480 am) and red(650 nm) emission, which were attributed to the 1G4 → 3H6 and 1G4 → 3F4 transitions of Tm3+ ion, respectively. The blue/red dual color up-conversion emission from this kind of phosphor may have applications in bio-imaging and optogenetics.

PbSe Quantum Dot Passivated Via Mixed Halide Perovskite Nanocrystals for Solar Cells With Over 9% Efficiency

PbSe quantum dots (QDs) have stronger electronic coupling resulting from a large Bohr exciton radius, suggesting PbSe QDs may be able to achieve superior charge separation and transport in optoelectronic devices compared with PbS QDs. However, PbS QDs solar cell have achieved a certified 12.01% power conversion efficiency (PCE), whereas PbSe QD photovoltaics lag behind at 8.2% PCE. One reason for this difference is that there has been significantly less work done on surface passivation of PbSe QDs. Here, the surface passivation of chlorinated PbSe QDs is optimized via a halide ion exchange treatment using mixed halide CsPb(Br/I)3 perovskite nanocrystals. Champion devices made from treated QDs achieved a PCE of 9.2%, Voc of 0.56 V, Jsc of 25.7 mA cm−2, and fill factor of 64%. Average PCEs for optimized cells are 8.9%. Detailed physical characterizations including capacitance‐voltage (C‐V), Voc, and Jsc as a function of light intensity, transient photovoltage, and photocurrent measurements are all carried out to investigate the mechanism of the improvement in the PCE and to understand the role of the mixed halide perovskites in providing superior surface passivation for PbSe solar cells. At this time, 9.2% is the highest PCE yet reported for PbSe QDs solar cells.

Impact of a commercially available ion-exchange resin used in red wines to reduce toxic compounds: effect on pH, oxidation–reduction potential, color, and sensory attributes

This research was performed to evaluate the impact of a novel ion-exchange treatment on the organoleptic, pH, color (hue and intensity), and oxidation-reduction potential (ORP) properties of commercial red wines. The ion-exchange treatment used in this study is a commercially available device containing a double cation-anion exchange resin. The device is applied, directly by the consumer, to finished bottled wines with the purpose of mitigating the effects of potentially noxious compounds such as biogenic amines and sulfites. Sensory evaluation tests included discriminative, affective, and Quantitative Descriptive Analysis sensory tests were employed to evaluate the impact on the perceived taste of treated wines. The pH, ORP and color parameters (hue and intensity) of wines were measured to assess any physicochemical alterations that may help to explain the results of the sensory evaluation. While no significant changes in color hue or intensity were found, the results showed a reduction in pH (0.07-0.12) and an increase in ORP (2.667-6.666mV). However, the changes in pH and ORP did not result in a detectable change in wine taste for the sensory panelists. These findings have important implications for the wine industry, where many consumers select wines for their characteristic taste qualities. Thus, any treatment to potentially remove noxious compounds should not impact the characteristic organoleptic properties of a chosen wine.

Stability, Structural, and Electronic Properties of Hausmannite (Mn3O4) Surfaces and Their Interaction with Water

Hausmannite (Mn3O4) is the stable phase of manganese oxides and has attracted interest due to its technological applications such as in molecular adsorption, ion exchange, catalysis, and water treatment. Hausmannite is a normal spinel structure that presents the formula A2+B23+O4, where the tetrahedral sites are occupied by Mn2+ and the octahedral sites by Mn3+ cations. The present work intends to fulfill the lack of information about the electronic and structural properties of hausmannite surfaces and their interaction with water. This is an important aspect for understanding the reaction mechanism occurring at the hausmannite–water interface. Density functional calculations have been employed to investigate the structural and electronic properties of hausmannite. Energy surfaces have been estimated for the low Miller indexes, and the water adsorption on the most favored surface was investigated in detail. The results indicate that the (001) cleavage surface is the most favored, in good agreement with th...

Removal of N-nitrosodimethylamine precursors by cation exchange resin: The effects of pH and calcium

Cation exchange resins have proved to be efficient in removing precursors of N-nitrosodimethylamine (NDMA). NDMA is a probable human carcinogen with a calculated lifetime cancer risk of 10−6 at 0.7 ng/L in drinking water. This paper investigated the effect of pH and calcium levels on the removal of NDMA precursors using a cation exchange resin. At pH 5 and 7, 30–50% of NDMA precursors, measured by formation potentials (FPs) changes before and after the treatment, were removed by Plus resin. However, increases in NDMA FPs were observed after the treatment at pH 10 indicating that NDMA precursors were released from the resin. NDMA FPs removals in samples containing 15 and 115 mg/L Ca2+ were 40% and −10% after the ion exchange treatments at pH 7, respectively. It was found that in the presence of high concentration of calcium only one out of four cation exchange resins released NDMA precursors (probably due to manufacturing impurities). Also, the release of NDMA precursors depended on the calcium concentration and the contact time of the resin with the solution containing calcium. Nonetheless, NDMA precursors release from the resin subsided significantly with increasing the number of regeneration cycles of the resin.

Improving the Flexural Properties of Abs/Muscovite Composites by Introducing Modified Muscovite

This paper reports the effect of unmodified and modified muscovite on the flexural properties of acrylonitrile–butadiene–styrene (ABS) composites. The composites were prepared by using melt compounding in an internal mixer. The morphologies of the composites were examined using field emission scanning electron microscopy (FESEM) whereas the structural characteristics of unmodified and modified muscovite were investigated by X-ray diffraction (XRD). The XRD results indicated that by modifying muscovite via two-stage ion exchange treatment, the basal spacing of muscovite was enlarged. The incorporation of treated muscovite (TM) in ABS matrix improved the flexural strength and modulus by 9% and 28%, respectively, compared to neat ABS strength of composites. The FESEM results showed that the fracture surface of ABS/TM composite indicated better interfacial adhesion between the filler and the matrix.

Homogeneous distribution of nanosized ZnO in montmorillonite clay sheets for the photocatalytic enhancement in degradation of Rhodamine B

Nanosized ZnO intercalated in montmorillonite (ZnO-MMT) was successfully prepared by two-step preparation: ion exchange and thermal treatment. It was found that the structure of the obtained composite was arranged in the house-of-cards structure with the homogeneous distribution of nanosized ZnO in the clay sheets, according to the XRD, SEM–EDX, TEM, XAS analyses. Importantly, as-obtained ZnO-MMT showed the small domains of crystalline ZnO with less particle aggregation. The particle size of ZnO defined by TEM was in the range of 1.8–3.0 nm. In addition, XAS results suggested the presence of short-range structural order in wurtzite ZnO crystalline. The photocatalytic activity of ZnO-MMT over Rhodamine B solution was remarkably enhanced with the normalized quantity of 8.4 mmol g−1 compared with a physical mixture of ZnO and montmorillonite (ZnO@MMT) (1.8 mmol g−1) and commercial ZnO (1.1 mmol g−1). This photocatalytic enhancement was attributed to the strong synergistic interaction of nanosized ZnO that was homogeneously embedded in the montmorillonite structure.