Calcium Compounds Research Articles

Effect of Calcium Salts Concentration on the Viscoelastic Properties of Sintered Tablets from Flours and Tortillas Evaluated by Stress-Relaxation Tests.

This research aimed to evaluate the effect of different calcium compounds and their concentration on the viscoelastic parameters of flours and tortillas obtained with traditional and ecological nixtamalization. Specimens (tablets) of nixtamalized flours and tortillas (14% moisture) prepared with three different calcium sources and four concentrations were sintered using a die and a hydraulic press and were evaluated by stress-relaxation tests with a texturometer. Data collected from the stress-relaxation curve were fitted into a three-element generalized Maxwell model (r2 = 0.9999), allowing the detection of significant differences in the estimated viscoelastic parameters. When flours are processed into tortillas, the most notable change was the increase of +88.44% and +73.44%, respectively, in the summation of the elastic modulus, and the compressional viscosity in samples produced with CaCO3. On the contrary, tablets from samples with Ca(OH)2 presented a sharp diminishing (loss) in both of the evaluated viscoelastic parameters, accounting a decrease of -39.82% and -46.28% for the elastic modulus and compressional viscosity summations, respectively. Highly significant correlations were found among viscoelastic parameters when a slight proportional increase was observed in the specific elastic moduli, meaning that the energy was stored by each elastic element in the tablets, while the compressional viscosity coefficients varied as a function of time. Finally, it was found that the residual spring due to the pure elastic component (E0 ) stored energy during the entire test. PRACTICAL APPLICATION: There is no published information about a simple methodology for the evaluation of the viscoelastic properties of dry nixtamalized flours (powder) with a texturometer. The method proposed was sensitive and accurate, since it was capable of detecting differences among samples processed under distinct processing factors conditions. The study of viscoelastic properties of grain foods contributes to the construction of molecular theories occurring in their chemical compounds, which is strongly related to food texture. Those theories are handy to improve nutritional and textural properties of grain foods and are essential to powder handling, processing, and transportation, which allows the processing factors optimization.

Development of magnetically separable Cu catalyst supported by pre-treated steel slag

Wastewater contaminated with organic compounds is a serious problem; therefore, many catalysts, especially copper catalysts, have been developed to treat it and remove contaminants before discharge. However, such separation and reuse of these catalysts is often challenging. Steel slag (SS), a by-product of steel production, is produced in large quantities and requires careful disposal. Therefore, in this study, we developed a magnetically recyclable copper catalyst utilizing pre-treated magnetic steel slag (MSS) as a support. First, magnetic separation was carried out to remove calcium silicate impurities such as alite and belite in MSS up to five times, thus increasing the Fe content of the MSS. We synthesized the Cu catalyst supported by MSS (donated as Cu@MSS) and characterized the catalyst by various surface analysis techniques, showing the presence of CuO and CuCO3 nanoparticles on the MSS surface. In catalytic reduction tests of para-nitrophenol using sodium borohydride in the presence of Cu@MSS, the reaction was accelerated when using the five-times pre-treated MSS because of the removal of inhibitors such as calcium compounds, as well as the high content of iron oxides leading to a synergetic effect with metallic Cu in this study. In addition, we investigated the effects of various factors, including Cu loading, sodium borohydride concentration, and catalyst dosage, on the catalytic activity of Cu@MSS. The catalyst was found to be stable and reusable. In summary, these results suggest that treated SS can be used as a support material for copper catalysts for the treatment of contaminated wastewater and the easy separation and reuse of the catalyst.

A Review of Mineral Carbonation from Industrial Waste

For relieving CO2 emissions and climate change, carbon sequestration and storage has been paid more attention. Mineral carbonation technology is a process that the calcium and/or magnesium-containing minerals react with CO2 to form stable carbonate precipitation, which in turn fixes CO2. It originates from natural rock weathering process that calcium and magnesium-containing rocks react with CO2 dissolved in rain water to form carbonate minerals. The source of mineral carbonation is the solid containing calcium and magnesium compound. The classification of mineral carbonation including direct and indirect mineral carbonation is indicated, and the descriptions of extraction by different extract agent have been given. The pretreatments, operation conditions and reaction kinetics are also discussed. Furthermore, the different processes by carbonizing from industrial waste are reviewed and the energy loss and cost are also described.

Alkali metals association in biomass and their impact on ash melting behaviour

Selected agricultural and energy crop biomass ashes represented by two mixed cereal straws, corn straw, Miscanthus × Gigantus and Salix Viminalis were chosen for ash behaviour investigation and prediction of operating problems during biomass combustion. The presence of aggressive species in the ash generate operational problems of heat exchanging surfaces in power boilers connected with slagging and fouling processes, limiting the use of biomass direct combustion for energy production. In this work, thermal behaviour characteristics, transformation properties of the inorganic components and ash fusion temperatures of biomass ashes were investigated using thermal analysis (STA), X-ray diffraction (XRD) and high-temperature microscope. The special attention was focused on the evaluation of potassium compounds presented in ashes. Potassium was detected as KCl, K2SO4, K2CO3 and K3PO4. It was noted, that presence and concentration of alkali metals, silicon and calcium compounds has the major impact on fusion temperatures of studied ashes. Leaching process of ash elements using water, ammonium acetate and hydrochloric acid solutions was performed to determine the association of alkali metals in the raw material. Based on the results, a mineral matter composition recalculation model was proposed to predict alkali compounds concentration in the fuel. The model might be also used to determine the risk of eutectics formation, which have the strongest influence on ash melting behaviour.

Промывка смешанного сульфатного мыла нейтрализованной кислой водой

Sulfate soap, being a valuable by-product of pulp production by the sulfate process, is a mixture of saponified resin and fatty acids and unsaponifiables (sterols, fatty alcohols, aliphatic hydrocarbons, etc.). Sulfate soap micelles enlarge and during surfacing may entrain a portion of black liquor containing dissolved lignin, as well as impurities of calcium compounds; when settling the liquor formed in pulp washing. The main method of removing black liquor is additional settling of sulfate soap prior its processing. It is reasonable and cost effective to use for washing a solution of salts formed in decomposition of soap or spent acid neutralized to pH = 8–14. The article shows the necessity of washing of sulfate soap obtained from different wood species in pulping. Neutralized spent acid received in soap decomposition was used as a washing solution in an amount of 10, 20, and 30 % of sulfate soap volume. Washing was carried out at a temperature of 20–80 °C. The optimal conditions for mixed sulfate soap washing were determined: temperature (20–40 °C), and flow rate of the washing solution (10–20 %). It was found that under optimal washing conditions of mixed sulfate soap with neutralized spent acid, the yield of crude tall oil and its acid number increase, the alkali and lignin content decrease, and the decrease of resin acids in tall oil is prevented.For citation: Starzhinskaya E.V., Kryazhev A.M., Tret’yakov S.I., Glukhanov A.A. Mixed Sulfate Soap Washing with Neutralized Spent Acid. Lesnoy Zhurnal [Forestry Journal], 2019, no. 5, pp. 194–202. DOI: 10.17238/issn0536-1036.2019.5.194

Evaluation of the Leachability of Contaminations of Fly Ash and Bottom Ash from the Combustion of Solid Municipal Waste before and after Stabilization Process

The aim of this work was to check the possibility of using a concrete matrix to immobilize contaminants from ash (fly and bottom) originating from the combustion of solid municipal waste. This work presents tests of ash from a Polish incineration plant. Nowadays, the management of ash poses a big problem with respect to the high concentration of contaminants that constitutes an environmental nuisance (heavy metals, chlorides, sulfates, etc.). The excessive leaching of contaminants disqualifies ash from being deposited in landfills for hazardous wastes. Bottom ash following the combustion of solid municipal waste mainly contains calcium (23.81%), chlorine (5.44%) and heavy metal (Σ 11.27 g/kg) compounds, while fly ash is characterized by a high content of chlorine (7.22%) and heavy metals (Σ 7.83 g/kg). In the next stage, two concrete mixtures were designed and prepared, containing 30% of ash from combustion of solid municipal waste. The most advantageous physicomechanical properties had concrete mortars that contained 30% of bottom ash: compressive strength—29.48 MPa, bending strength—1678 kN. The performed tests showed that immobilization of dangerous compounds through the C-S-H phase of the concrete significantly decreases the migration of dangerous substance into the environment and minimizes its toxicity. Approximately 97% of the chloride and sulfate salt content was immobilized, and the heavy metal content was immobilized by the C-S-H phase to a degree of 90%. The results obtained provide the option of conveniently managing dangerous wastes with the use of a tight and durable concrete. In many cases, such technology may constitute the best and the cheapest long-term solution in the waste management economy. It may also fill a market gap in this field.

One-part geopolymers from mining residues – Effect of thermal treatment on three different tailings

Use of mine tailings as an aluminosilicate precursor in alkali activation is becoming an interesting alternative to manage the high-volume of waste generated from mining industries. However, very few tailings have so far been studied for their mineralogical properties and alkali activation potential. This study aims at understanding the ability of mine tailings from phosphate, kaolinite and lithium mines for their efficient participation in alkali activation. Biotite, muscovite, kaolinite, albite, and quartz were found to be the major minerals present in them. The impact of variation in mineralogy on silica and alumina solubility of these tailings was analyzed. The solubility was found to be high in impure kaolinite compared to the other two. Effectiveness of thermal treatment (750 °C and 900 °C) on improving the reactivity of these tailings in alkaline condition was also investigated. It was observed from the results that the effect of thermal treatment on the crystalline structure and solubility of an aluminosilicate material mainly depends on the mineral structure of the material, as well as the treatment temperature. Interestingly, thermal treatment reduced the solubility of lithium tailings with albite and quartz mineral. Effort has been made to relate the strength attained by alkali activation of mine tailings to their solubility values. However, despite of the higher solubility offered by impure kaolinite, phosphate tailings gives the maximum strength improvement by 62%. This can be due to the presence of calcium compounds in phosphate tailings that resulted in additional hydration products.

МИКРОБИОЛОГИЧЕСКИЕ УСЛОВИЯ РАСПРЕДЕЛЕНИЯ ХИМИЧЕСКИХ ЭЛЕМЕНТОВ ПО ГЛУБИНЕ ТОРФЯНОЙ ЗАЛЕЖИ В ЭКОСИСТЕМАХ ВОСТОЧНОЙ ЧАСТИ ВАСЮГАНСКОГО БОЛОТА (ЗАПАДНАЯ СИБИРЬ)

Актуальность определяется необходимостью учета взаимосвязей между распределением химических элементов по глубине торфяной залежи, процессами формирования, эволюции и деградации болот при решении целого ряда фундаментальных и прикладных задач изучения, использования и охраны болот. Цель: оценка микробиологических условий распределения химических элементов по глубине торфяной залежи и выявление связей между геохимическими и микробиологическими показателями торфов в восточной части Васюганского болота. Методы: методы химического и микробиологического анализа (включая масс-спектрометрический с индуктивно связанной плазмой), статистические методы. Результаты и выводы. Выполнен химический, минералогический и микробиологических анализ проб торфов и минерального грунта, отобранных 09.11.2018 г. в восточной части Васюганского болота (граница водораздела рек ключ и Гавриловка – элементов речной сети: (Ключ–Бакчар; Гавриловка–Икса) – Чая–Обь; внутриболотные экосистемы: олиготрофный грядово-мочажинный комплекс, гряда; олиготрофное сосново-кустарничково-сфагнового болота – рям; мезотрофное сосново-кустарничковое болото на границе ряма с заболоченным лесом – мезотрофная окраина. Показано, что, во-первых, болотная микрофлора является очень важным фактором распределения химических элементов по глубине торфяной залежи в различных внутриболотных экосистемах восточной части Васюганского болота. Вероятность накопления в торфах малорастворимых соединений кальция, железа и редкоземельных элементов возрастает по мере усиления анаэробных условий развития болотной микрофлоры, определяющих увеличение рН болотной среды до 7,8 и выше, что приводит к смещению карбонатного равновесия и выпадению малорастворимых соединений кальция. Во-вторых, возможность выведения из раствора гидроксидов железа является характерной особенностью геохимии торфяных болот на фоне незначительной, но постоянно наблюдаемой активности железобактерий, образующих гидроксиды железа. В-третьих, вследствие сорбционных процессов на гидроокислах железа (и малорастворимых соединениях кальция в нижних слоях торфяной залежи) происходит осаждение гидроокислов, фосфатов и карбонатов (возможно – сульфатов и сульфидов) ряда микроэлементов, включая редкоземельные элементы.

Particulate Matter in a Hospital Environment: as Potential Reservoir for Hospital Strains

Relevance. For decades, many aspects of aerosol transmission of hospital pathogens have been and remain the subject of scientific debate. Despite fairly detailed studies of the mechanism of microbial aerosols formation, distribution, the role of particulate matter in the formation of antibiotic resistance and multidrug-resistant hospital clones of microorganisms is still unclear. Aim. To investigate physicochemical properties and microbiological diversity of hospital particulate matter. Materials and Methods. Shape and size of particulates was assessed by means of scanning electron microscopy and dynamic light scattering while elemental analysis was performed using energy-dispersive X-ray spectroscopy and high-temperature catalytic oxidation. Microbial profiling was conducted using polymerase chain reaction and Vitek 2 biochemical analyzer. Results. Hospital particulate matter included globular and fibrillary particles consisting of carbon, oxygen, calcium, silicon, aluminium, and sulfur. Intriguingly, microfiber particles had higher oxygen and calcium content along with the lower level of carbon in mineral but not organic component. Differential localisation of silicon and calcium in elemental mapping suggested that hospital particulate matter was composed of aluminosilicate minerals and calcium compounds. Among the microorganisms, we found multidrug-resistant strains Raoultella ornithinolytica, Staphylococcus pseudintermedius, Pantoea spp., Pseudomonas aeruginosa, Enterococcus faecium and additionally Pasteurella canis in hospital particulate matter samples. Conclusions. Particulate matter in the hospital environment might be considered as a potential reservoir for the evolution of antibiotic resistance and multidrug-resistant strains.

Thermodinamical Analyse the Formation of Phosphates Copper, Zinc and Cobalt on the Base Double Superphosphate and Sulphates of Copper, Zinc and Cobalt

In this article the relationship between the entropies of crystalline calcium compounds and copper, zinc and cobalt compounds were analyzed. Thermal capacity dependence of temperature for acidic phosphates of copper, zinc and cobalt, determining value of enthalpy and entropy of copper, zinc and cobalt phosphates have been determined and the possibility to conduct thermodynamic analysis of reactions for their formation were established. Accordingly the data of thermodynamic analysis of temperature conditions for obtaining double superphosphate, the most formation of monosubstituted phosphates of copper, zinc and cobalt, and possibility of formation disubstituted of copper phosphates.

Flame inhibition by calcium compounds: Effects of calcium compounds on downward flame spread over solid cellulosic fuel

Owing to depletion risks and the rising cost of phosphate rock, phosphorus-free fire-extinguishing agents are in growing demand. This paper aims to develop a new fire suppressant that does not use phosphates and reports the flame-inhibition properties of calcium compounds: calcium acetylacetonate (Ca(acac)2), calcium acetate (Ca(OAc)2), calcium hydroxide (Ca(OH)2), calcium carbonate (CaCO3), calcium nitrate (Ca(NO3)2), and calcium oxide (CaO). Their flame-inhibition capabilities were evaluated by measuring the downward flame-spread rates over cellulosic fuels on which each calcium compound was adsorbed. Suppression experiments demonstrated that Ca(acac)2, Ca(OAc)2, Ca(OH)2, and CaCO3 extinguished flames. Ca(OAc)2 and Ca(acac)2 were more effective by factors of approximately 1.6 and 1.4, respectively, than ammonium dihydrogen phosphate. To elucidate the influences of the calcium compounds on the pyrolysis of cellulose and char combustion, the activation energy (E) and pre-exponential factor (A) associated with the pyrolysis of cellulose and the char yield (Y) were determined by kinetic analyses involving thermogravimetric measurements. The kinetic analysis permitted us to conclude that none of the calcium compounds hindered cellulose pyrolysis or char combustion. A positive correlation between the bond energy of the compound and minimum extinction concentrations was found, thus suggesting that compounds that easily release atomic calcium effectively inhibit flames.

EFFECT OF FOLIAR SPRAY WITH AMINO ACIDS , CITRIC ACID, SOME CALCIUM COMPOUNDS AND MONO-POTASSIUM PHOSPHATE ON PRODUCTIVITY, STORABILITY AND CONTROLLING GRAY MOULD OF STRAWBERRY FRUITS UNDER SANDY SOIL CONDITIONS

A filed experiment was carried out during the two successive seasons of 2016/2017 and 2017/2018 at the Experimental Farm of El-Kassasein, Hort. Res. Station, Ismailia Governorate, Egypt, to investigate the effect of foliar spray with amino acids, citric acid, some calcium compounds and mono-potassium phosphate (MKP) on vegetative growth, early and total yield, yield components, storability and gray mould disease reduction of strawberry Festival cultivar under sandy soil conditions. The obtained results showed that, spraying strawberry plants with CaCl2 at 20 ml/l, amino acids at 10 ml/l, citric acid at 2 g/l, calcium amino acids chelate at 20 ml/l and calcium citric acid chelates at 20 ml/l and mono-potassium phosphate (MKP) at 20 ml/l increased yield, yield components and decreased incidence and severity of gray mould disease compared to control. Spraying with amino acids or calcium amino acids chelate increased plant height, number of leaves/ plant, shoot dry weight/ plant, average yield/plant, total yield/fad., and decreased weight loss (%) and decay (%) during cold storage periods. Spraying with MKP recorded minimum incidence (12.6 and 18.3 %) and severity (13.9 and 13.2%) of gray mould disease in fruits at the 1st and 2nd seasons, respectively, followed by spraying with calcium amino acids chelate. In addition, incidence and severity of gray mould disease decreased with increasing TSS and vitamin C in strawberry fruits.

Insight of particulate arsenic removal from coal-fired power plants

Arsenic is easily volatilized as vapors during coal combustion and predominantly transferred into particulate forms. The removal of particulate arsenic together with fine fly ash particles is essential to control arsenic emission during coal combustion. In this study, fly ashes and different size fraction samples (PM2.5, PM10, and PM20) were collected or prepared from four Chinese coal-fired power plants, with objectives of studying the arsenic distribution and speciation in fly ash, and understanding the retention relationship between the removal of ash particles and particulate arsenic. The results demonstrated that the concentration of arsenic of the first two ESP (electrostatic precipitator) hoppers was at similar level, then followed by a substantial increase in the rear hoppers. And the particle size distribution of fine fly ash particles from various ESP systems presented essentially similar trend. Furthermore, particulate arsenic was mainly present as arsenates probably through the interactions between arsenic vapors and accessory Ca/Fe/Al-minerals. Arsenic associated with calcium compounds tended to be enriched in coarse particles, while arsenic bound with Fe/Al-compounds was enriched in fine particles. Meanwhile, arsenic associated with calcium sulfate compounds was easier to be captured by ESP compared to calcium silicate-bound arsenic. The interactions between arsenic vapors and various accessory minerals not only affected the size distribution characteristics of particulate arsenic, but also had a great effect on its removal efficiency of ESP. Specifically, based on the ash resistivity calculation, arsenic-bearing fine particles with certain amount of Fe had suitable conductivity and favored the capture of particulate arsenic by ESP.

Thermodynamic Analysis of the Oxidation of Radioactive Graphite in Molten Na2CO3–K2CO3–Sb2O3 in a Carbon Dioxide Atmosphere

More than 100 power reactors, reactors for plutonium production, and research reactors are presently available in the world. In these reactors, graphite is used as a reflector, moderator, and cladding of fuel elements. Flameless combustion is a promising method for reducing the amount of solid radioactive waste. The method is based on the oxidation of solid radioactive waste in oxide–carbonate melts and makes it possible to reduce the radioactive graphite volume considerably. Thermodynamic simulation and analysis of the oxidation of radioactive graphite in molten Na2CO3–K2CO3–Sb2O3 in a carbon dioxide atmosphere are performed using the TERRA software package. The thermodynamic simulation is conducted at a pressure of 1 atm and initial and final temperatures of 273 and 3273 K, respectively. The step of temperature changing is 100 K. Based on these data, the distributions of elements between condensed and gas phases are examined. The simulation results show that carbon disappears at a temperature of 873 K. Heating of the system up to 1073 K leads to the evaporation of condensed antimony compounds. Heating of the system up to 1673 K leads to the evaporation of condensed potassium, sodium, chlorine, uranium, and cesium compounds. Heating of the system up to 2273 K leads to the evaporation of condensed nickel compounds. Heating of the system up to 2573 K leads to the evaporation of condensed calcium, plutonium, beryllium, strontium, americium, and europium compounds. Only a vapor–gas phase is observed at temperatures above 2573 K.

Experiment of Partial Replacement of Egg Shell Powder and Coconut Fibre in Concrete

India is in fifth position in the world annual egg production. About 1.61 million tons of egg shells are being waste annually by disposing it as a landfill, which attracts vermin due to attached membrane and causes problems to human health and environment.It is scientifically known that the eggshell is mainly composed of compounds of calcium. Calcium carbonate, (CaCO3), is the major composition of the eggshell, accounting for 93.70% of the total composition of the eggshell. Similarly, calcium carbonate (CaCO3), is the primary raw material in the production of cement. The produced OPC is composed of four main Calcium compounds in the forms of di calcium silicates, (C2S), tri calcium silicate, (C3S), tri calcium aluminate, (C3A), and tetra-calcium aluminoferite, (C4AF). It is, therefore, indicated that cement and eggshells have the same primary composition in calcium compounds. Calcium rich egg shell is a poultry waste with chemical composition nearly same as that of limestone. Use of eggshell waste instead of natural lime to replace cement in concrete can have benefits like minimizing use of cement, conserving natural lime and utilizing waste material. Eggshell waste can be used as fertilizer, animal feed ingredients and other such uses

Catalytic effect of representative calcium salts on the steam gasification of a Shengli lignite

CaCO3, Ca(CH3COO)2 and Ca(C6H5COO)2 were selected as representatives of calcium species formed by calcium ions with organic structures and added to an acid-leached Shengli lignite (SL+) to study the catalytic mechanism of calcium on the steam gasification. The main gasification temperature range of the calcium-added samples was surprisingly consistent with the specific thermal decomposition temperature of the added calcium compounds. XPS and FTIR revealed that the added calcium interacted strongly with the oxygen-containing functional groups in lignite to form calcium-carboxylate, which were further converted to CaCO3 analogous structure during the thermal process (confirmed by XRD). The significant catalytic effect of calcium on the steam gasification all occurred simultaneously with the decomposition of CaCO3 analogous. The formed calcium species from the decomposition of in-situ formed CaCO3 could interact with the adjacent carbonaceous organic structures in lignite under the presence of gaseous water molecules to form calcium-centered complexes. The calcium-catalyzed effects on the steam gasification were depended on the decomposition processes of in-situ formed CaCO3 species. Finally, the possible mechanism for the catalytic effect of calcium on the steam gasification of Shengli lignite was proposed.

Calcium Bioaccumulation by Pleurotus ostreatus and Lentinus squarrosulus Cultivated on Palm Tree Wastes Supplemented with Calcium-Rich Animal Wastes or Calcium Salts

Calcium assimilated by edible fungi cultivated on two palm tree wastes viz.; coconut husk with coir (CH), and palm kernel fibre (PK) supplemented with egg shell of chicken (ES), snail shell (SS), bone shaft of cow (BS) at different ratios or with 1.5% w/w calcium compounds as a calcium-rich substrate was investigated. Pleurotus ostreatus cultivated on (CH + ES + SS) and (CH + 1.5% w/w CaCO3) have the highest (P < 0.05) biological efficiency of 57.70% and 56.91%, respectively. Lentinus squarrosulus from (PK + ES) and (CH + 1.5% w/w CaCO3) also has relatively high (P < 0.05) biological efficiency of 54.09 and 53.41%. Lentinus squarrosulus harvested from (CH + ES + SS + BS) have the highest protein content of 6.50%, followed by P. ostreatus harvested from (PK + ES + SS + BS) with 6.40%. Pleurotus ostreatus and L. squarrosulus harvested from non-calcium supplemented substrates respectively have the lowest calcium content of 125.0–133.0 mg/100 g and 105.0–185.0 mg/100 g. P. ostreatus harvested from (CH + ES + SS) have the highest calcium content of 596.6 mg/100 g with Absorption Ratio (AR) of 4.6, while L. squarrosulus cultivated on (PK + ES + SS + BS) have calcium content of 510.6 mg/100 g with the highest AR of 4.8. Fortification of lignocellulosic wastes with calcium salts or animal wastes that are rich in calcium is a good substrate mixture to produce calcium-enriched mushrooms, which will pacify calcium deficiency aliments.

Incorporation of Ca ions into anodic oxide coatings on the Ti-13Nb-13Zr alloy by plasma electrolytic oxidation

The present work concerns the surface modification of The Ti-13Nb-13Zr alloy by electropolishing and plasma electrolytic oxidation (PEO) process in Ca-containing electrolytes: calcium formate and calcium lactate solutions (0.1-1.0 mol dm-3) under voltages of 200 and 400 V. As a result of the PEO process, a porous oxide layer containing incorporated calcium compounds was formed on the Ti-13Nb-13Zr alloy surface. The morphology and chemical composition of the modified Ti-13Nb-13Zr alloy were investigated using scanning electron microscopy (SEM + EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). An increase in the applied voltage caused an increase in the number of pores and an increase in the amount of calcium incorporated in the oxide layer. Analysis showed that all samples were covered by titanium oxide, which was present in the form of anatase and/or rutile. In course of the experiments, it was showed that the proposed procedure has a positive effect on the overall bioactivity of the Ti-13Nb-13Zr alloy. Bioactivity investigations using simulated body fluid (SBF) confirmed the formation of apatite on the anodized surfaces. The cell adhesion results obtained by the use of human bone marrow mesenchymal stem cells (hBMSC) demonstrated that the PEO coatings on the Ti-13Nb-13Zr alloy remarkably enhanced the cytocompatibility of the substrate, indicating a potential application in orthopedic surgeries. The incorporation of Ca into the oxide layer proceeded to a higher extent when the PEO treatment was performed in the calcium lactate bath. The oxide layers formed in the calcium lactate solution exhibited also superior biological behavior towards hBMSC. This can be ascribed to the presence of carboxylic groups onto coatings' surface (as identified by XPS), which facilitated the anchoring of cells and tissues.

Steel converter slag as an oxygen carrier in a 12 MWth CFB boiler – Ash interaction and material evolution

Steel converter slag or LD slag is a byproduct of the basic oxygen steel production process, where raw iron from the blast furnace is converted to steel. LD slag contains mainly calcium and iron compounds and smaller amounts of magnesium, silicon, manganese and vanadium. The iron content, about 17 wt.% of the slag, makes this material a potential oxygen carrier for combustion processes such as Oxygen Carrier Aided Combustion (OCAC) or Chemical Looping Combustion (CLC). This study will present an investigation of the use of LD slag as an oxygen carrier in OCAC at semi-industrial scale. The Chalmers 12 MWth biomass circulating fluidized bed boiler was operated using LD slag as bed material under OCAC conditions. During the operation, bed samples from the boiler were extracted and analyzed with ICP-SFMS, SEM-EDS, XRD and different mechanical tests to analyze chemical and physical changes of the bed material as a function of time. The samples were also investigated in a laboratory fluidized bed reactor to determine the change in reactivity towards common volatile fuel components, i.e. CO, H2, CH4 and C6H6. It was found that LD slag can be utilized as an oxygen carrier in a combustion process for biofuel. However, the reactivity towards syngas, CH4 and C6H6 is reduced as a function of time in the boiler, which is believed to be caused by accumulation of, and interaction with, alkali from the biofuel ash. Sulfur addition may decrease the adverse effects of alkali on combustion efficiency, but not eliminate them completely.

Кремнийсодержащие соединения в составе хвощей (Equisetum Equisetaceae)

The article presents the results of a chemical and phase composition study of ash obtained from the aerial parts of three horsetail species growing in different regions of Primorsky Krai, namely forest (Equisetum sylvaticum L.), wintering (Equisetum hyemale L.) and field (Equisetum arvense L.) horsetail. It is shown that the conditions for processing raw materials affect the content of silicon dioxide (32–98%) in the ash residues. X-ray phase analysis has shown that the amorphous or amorphous-crystalline state of ash residues depends on the conditions of their production. The absorption bands typical for amorphous silicon dioxide are observed in the IR spectra of ash samples, which correspond to bending (467 cm-1 ) and stretching vibrations (802 and 1092 cm-1 ) of Si-O-Si siloxane bonds. The elemental analysis of silicon-containing products indicates an increase of silicon dioxide content in the samples with an increase in acid concentration during the processing of the aerial part of the horsetails, which also depends on the plant species: the field horsetail contains the lowest quantity of SiO2 as compared to the forest and wintering horsetails, but is characterised by a high content of potassium and calcium compounds. The sorption characteristics of ash obtained from the aerial part of horsetails are assessed: iodine adsorption capacity (5–42%) and methylene blue (164–260 mg/g) and methyl orange (40–241 mg/g) organic dye adsorption capacities. The obtained information can be used in the development of sorbents from vegetable raw materials for the purification and after-purification treatment of natural and waste waters from pollutants of various types.