Raw Material Ratio Research Articles

Defect regulation of a distinctive synthetic Eu2+-doped SiAlON S-phase towards controllable spectra and thermal quenching for white-light-emitting diode

Targeted control of the luminescent properties of phosphors for white-light-emitting diode (WLED) applications, particularly spectral position and thermal stability, is crucial. In this study, a newly developed Eu2+-doped sialon S-phase BaAl1+ySi5-yO2-y/2N7 with intrinsic O vacancy (Vo) defects was synthesised using a special raw material ratio with an O deficiency. A series of structure–performance characterisations and density functional theory (DFT) calculations were performed. It was found that the spectral position and thermal stability of the samples could be realised by defect regulation using two approaches: regulation of the Eu2+ content and Al/Si ratio. Consequently, the emitting colour of the samples could be adjusted from green to yellow, leading to a lower colour temperature and higher colour rendering in the assembled WLED. The abnormal thermal quenching effect can also be suppressed with less variation in the emission intensity and colour purity at high temperatures. The defect regulation process investigated in this study will hopefully offer novel ideas for improving the luminescence properties of phosphors for extensive WLED applications.

Influence of iron substitution on the microstructure and properties of ettringite in calcium sulfoaluminate cement: A comprehensive study on the Al/(Fe+Al) ratios

Ettringite, as the dominant hydration product of calcium sulfoaluminate cement, significantly contributes to cement strength. Its formation is closely related to the Fe and Al ratio in raw materials. During cement hydration, Fe present in ferrite can replace some of the Al in ettringite, which notably affects the microstructure and properties of the latter. To understand the relationship between the Al/(Fe + Al) ratios and the ettringite phase, we synthesized ettringite with varying Al/(Fe + Al) ratios using a chemical synthesis method. The microstructure was then characterized to determine the formation process of this phase. Various analysis methods, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscope (TEM), and N2 adsorption-Brunauer Emmett Teller (BET), were used to study the solid phases. For aqueous solutions, inductively coupled plasma emission spectroscopy (ICP-OES) was employed. Our results reveal that Fe replacing Al leads to regular changes in the ettringite crystal's microstructure. As the Al/(Fe + Al) ratio decreases, there is a reduction in the ettringite unit cell parameter a, an increase in c, and an enlargement of the unit cell volume. Concurrently, Fe substitution shrinks the crystallinity and grain size of ettringite crystals. SEM-TEM and BET demonstrate that Fe substitution boosts ettringite's particle size and aspect ratio, while the specific surface area contracts with a decreasing Al/(Fe + Al) ratio. Moreover, Fe substitution tends to lower ettringite's thermal stability and OH group binding ability. When the Al/(Fe + Al) ratio reached 80%, the ettringite crystal exhibited optimal thermal stability.

Development of an Efficient Synthetic Process for Irisquinone

AbstractIrisquinone is a tumor radiotherapy sensitizer and has been found to have broad-spectrum antitumor activity in recent years. The current acquisition method of extracting and purifying from semen irisis has greatly limited its wide application and activity study deeply. In this work an efficient route for the synthesis of the irisquinone was investigated to solve the source of it. The target compound was synthesized by 5-step reactions to Wittig reaction, reduction, oxidation, Wittig reaction, and oxidation using 3,5-dimethoxycarboxaldehyde as the starting material with an overall yield of 48%. The key factors such as the ratio of raw materials, temperatures, solvents, reaction times, and types of base for the main reactions were optimized. In addition, the deprotection and reduction were completed with Pd/C catalytic simultaneously when compound 2 was synthesized from compound 1. In the last reaction, the 3,5-dimethoxybenzene moiety of compound 4 was directly oxidized to 6-methoxy-1,4-benzoquinone by K3[Fe(CN)6]/H2O2 without the need to selectively remove the methyl protecting group, which were the innovative points in the experimental route design of the irisquinone synthesis. This work has opened new perspectives for the artificial synthesis and the development of irisquinone.

Recovery of sulphur dioxide by converter dust synergistic coke decomposition of phosphogypsum

To further improve the decomposition ratio and sulfur dioxide mass yield of coke-reduced solid waste phosphogypsum (PG), converter dust (CD) is proposed as a novel additive. The effects of raw material ratio, time and temperature for roasting on the decomposition process of PG were inspected by simulation calculations and fluidized bed experiments. It turns out that the optimized reaction conditions are Fe3O4/Ca of 0.6, C/Ca of 0.4 at 1100 °C for 24 min, under which the PG decomposition ratio and SO2 mass yield are 99.56 % and 97.64 %, respectively. The addition of CD is able to reduce the initial reaction temperature from 975 °C to 914 °C, and promote the release of SO2. Kinetic analysis shows the mechanistic equation for this process is obtained as G(α) = [−ln(1 − α)]3/2, indicating that the decomposition reaction mechanism is a crystal nucleation and growth-controlled process. The chemical mechanism of the process is that coke and Fe3O4 in the CD convert CaSO4 to the intermediate CaS, and Fe3O4 is oxidized to Fe2O3. Then CaS and CaSO4 continue to react with Fe2O3 to form Ca2Fe2O5 and SO2. The presence of Fe2O3 accelerations the rate of CaS and CaSO4 roasting reaction and lowers the reaction temperature. Meanwhile, the self-decomposition of PG also produces CaO and SO2. Finally, a process for SO2 recovery from CD synergized with coke decomposition of PG is proposed.

Investigation effect of Lu-substitution on structural, morphological, magnetic, and dielectric properties of BaM hexaferrite synthesized using a co-precipitation method

In this paper, we synthesized Lu-substituted M-type barium ferrites (BaLuxFe12-xO19, x = 0, 0.2, 0.4, 0.6, 0.8) by chemical co-precipitation using a non-stoichiometric ratio of raw materials. We investigated their structure, XPS, and EDX spectra, morphology, and magnetic and dielectric properties. The XRD patterns showed that the diffraction peaks shifted toward a lower angle and the lattice constant ratio (c/a) was less than 3.98, which was within the allowable range of magneto-plumbite structure. XPS and EDX spectra confirmed the presence of O, Fe, Ba, and Lu elements in the samples. SEM images revealed that the ceramic samples sintered at 1330 °C had a regular and obvious hexagonal structure. Lu substitution promoted grain growth, with an average grain size increase of 163% and a maximum grain size of 21.77 µm. Hysteresis loops indicated the formation of a multi-domain structure in the samples. The coercivity decreased from 2035.82 Oe to 574.84 Oe and the saturation magnetization decreased as well but still exceeded 58 emu/g. The dielectric constants of all the samples were in the order of 103 to 104 and the substitution of Lu significantly increased it to about 16k. The tangent loss could be maintained below 0.5, with a minimum of approximately 0.1. The Lu-substitution barium ferrites with high saturation magnetization, low coercivity, high dielectric constant, and low tangent loss coexistence may be a potential candidate for application in low-frequency wireless communication with miniaturization and multifunction.

Utilizing waste pomelo peel to develop activated-doped porous biomass carbon as electrode materials: Study of activation mechanism, evaluation of electrochemical properties and assembly of symmetric supercapacitors

To prepare electrode materials with excellent comprehensive properties for supercapacitor applications, and to promote the reuse of waste fruit peels. This work used waste pomelo peel as a carbon source for high-temperature carbonization, and a series of porous biomass carbon materials (YB-K) was prepared using a combination of freeze-drying and activation pore-making. The relationship between the structure of YB-K materials and the amount of activator was investigated by characterization. The results show that the YB-K materials (YB-K5) with the mass ratio of raw materials to activator of 1:5 have the best overall properties, and their specific surface area is as high as 1277.14 m2/g. Notably, the YB-K5 materials can be doped with nitrogen to prepare electrode materials (YB-K5-N) with excellent electrochemical properties. The specific capacitance of YB-K5-N electrode materials reaches 247.26 F/g at 0.5 A/g current density. Importantly, the YB-K5-N symmetric (button type) supercapacitor assembled with YB-K5-N materials showed good cycling stability with 87.58% specific capacitance retention after 3000 cycles. The YB-K5-N electrode materials prepared in this work have potential applications in energy conversion, energy storage and electrochemistry, which provide a new idea for utilizing waste fruit peels.

Preparation and performance study of SiO2 aerogel thermal insulation coating with nanoporous structure for wind turbine blade surface

To prepare a base layer of thermal insulation for the surface of wind turbine blades, we utilized SiO2 aerogel material with a nanoporous structure as the thermal insulation layer of an inorganic composite photothermal de-icing coating. We further investigated the influence of raw material ratio and process on the thermal insulation layer’s performance. By adjusting the process parameters, the microstructure and characteristics of the SiO2 aerogel thermal insulation coating were controlled. Microstructure scanning and EDS analysis were employed to assess the results. The results of the experiment suggest that, as opposed to brush coating, atomized spraying is a better technique for creating SiO2 aerogel thermal insulation coating. The coating possesses excellent mechanical stability and applicability, maintaining a coating wear rate within 5% after 20 wear cycles under a load of 1734 N/m2, and the coating achieves the highest class 0 surface adhesion to the substrate surface. The coating exhibits exceptional heat insulation performance, reaching a temperature of 32.7 °C after five spraying cycles, which is 20.0 ∼ 29.4 °C higher than the surface without producing a complete heat insulation layer. The SiO2 aerogel aqueous slurry has a viscosity of 31.3 ∼ 36.9 mPa∙s, which is capable of forming a uniform membrane surface when sprayed at a 60° angle at 0.95 MPa pressure. Consequently, this paper’s design of photothermal thermal insulation offers strong anti-abrasion and excellent thermal insulation, presenting a new avenue for scientific investigation into coating photothermal de-icing.

ПОЛУЧЕНИЕ ПРОЛОНГИРОВАННЫХ КАРБАМИДОФОРМАЛЬДЕГИДНЫХ УДОБРЕНИЙ И ОЦЕНКА ИХ ВЛИЯНИЯ НА РАЗВИТИЕ СУДАНСКОЙ ТРАВЫ В ВЕГЕТАЦИОННЫХ И ПОЛЕВЫХ ОПЫТАХ

The results of studies on the production of prolonged urea-formaldehyde fertilizers (UFFs) in the interaction of carbamide (urea) with formalin («carbamide:formaldehyde» = 1:(0.15÷0.4) mol). It is shown that the rate of dissolution of UFFs granules is significantly lower (10-50 times relative to carbamide). It was found that in the soil, carbamide nitrogen transforms into an alkaline hydrolyzable form within 2 weeks by 30 %, and UFFs nitrogen by only 10 %. It is shown that the value of the «digestibility index» (the main indicator of fertilizer quality) is primarily determined by the ratio of raw materials and decreases uniformly with an increase in the amount of formalin. According to the data of the thermal behavior curves (melting point, loss of mass), it was found that the residual urea content and the amount of the resulting target product, methylenediocarbamide (MDС), in the obtained UFFs samples differ slightly from the calculated values. Despite the insignificant amount of the initial formalin, a small number of other dicarbamide derivatives (monomethylolcarbamide, dimethylolmethylenecarbamide, etc.) are also formed. The number of these compounds is determined not only by the ratio «carbamide:formaldehyde», but also other technological parameters (type of catalyst, pH value, duration of interaction). In order to optimize the composition of UFFs , vegetation and field experiments were conducted (on gray forest soil of experimental fields of Kazan State Agrarian University) with Sudanese grass. The same agrochemical effect of using UFFs in vegetation and field experiments (an increase in green mass to «+ 20-21%» relative to urea) shows that in the field, due to the low rate of dissolution of granules, nitrogen leaching from fertilizers by precipitation is practically absent

Improvement of magnesium oxysulfide cement used in geological environment of oil and gas wells

Magnesium oxysulfide cement (MOS) has excellent acid solubility properties and can be used for severe loss plugging in oil and gas wells. However, the solidification time of MOS cement is fast, making it difficult to be used in the geological environment of oil and gas wells. The MOS suitable for construction operation in oil and gas wells under a temperature of 60 ℃ was studied by optimizing the raw material ratio and modification. The influence of MgO/MgSO4 and H2O/MgSO4 mole ratios on the compressive strength of MOS was studied by a single-factor experiment. The response surface methodology (RSM) was used to optimize the raw material ratio. The sodium hexametaphosphate (SHMP) was applied to adjust the thickening time of MOS, and its effect on MOS was studied. The microstructure and phase composition of different MOS were analyzed. The results show that under hydrothermal conditions at 60 ℃, the optimal mole ratio of MgO: MgSO4: H2O of MOS is 11.39:1:19.26, and the 24-hour compressive strength of MOS is 12.89 MPa. The thickening time of MOS was extended by 100 min, and the compressive strength increased by 25.26% in 72 h with 6 wt% SHMP at 60 ℃. The SHMP-modified MOS has high compressive strength and a longer thickening time, and its strength develops steadily with time. The short rod-shaped 517 phase connected in MOS is beneficial for improving the strength. SHMP can regulate the stability of MOS, promote the formation of the 517 phase, and improve the strength of MOS. The research results support the application of magnesium oxysulfide cement in oil and gas wells.

The mechanism of NOx removal in the sintering process based on source reduction of carbon emissions.

This study systematically investigates the mechanism of NOx emissions during the sintering process, with a focus on the utilization of biochar as an auxiliary fuel to replace a portion of the coke traditionally used in iron ore sintering. The research involved the simulation of sintering raw material ratios using iron ore, biochar, and coke powder. Substitution levels of biochar for coke were set at 0%, 20%, 40%, 50%, 60%, 80%, and 100%. NOx emissions during the sintering process were monitored using a sintering flue gas detection system. Simultaneously, a comprehensive analysis of the sintered ore was conducted with the aim of producing samples that meet sintered ore requirements while reducing NOx emissions. Experimental results revealed that when biomass charcoal substitution for coke reached 50%, the lowest NO emissions were observed during the sintering process, with a reduction of over 90% in accumulated NO emissions in the exhaust gas. In this process, due to the participation of biochar, CO2 emissions were reduced by approximately 50% compared to traditional sintering processes. The study also analyzed the physicochemical properties of the sintered ore using methods such as XRD, Raman, FTIR, and Vickers hardness testing. The results indicated that the hardness fluctuated within the range of 610 to 710N for sintered products with different levels of biochar substitution, and there were minimal changes in Fe element content and crystal phase transformations.

Magnesium Oxychloride and Magnesium Oxysulfate Cements as Temporary Plugging Agents in Geothermal Drilling.

The development and utilization of geothermal resources are effective ways to alleviate the current haze situation, adjust the energy structure, and achieve energy conservation and emission reduction. Geothermal formations typically contain extensive fracture networks, with fracture openings. These fracture networks can result in substantial losses of the drilling fluid and increased costs for geothermal drilling. Temporary plugging cements are used to solve the problem of lost circulation due to their high strength and high acid solubility. In this paper, two types of temporary plugging materials, magnesium oxysulfate (MOS) cement and magnesium oxychloride (MOC) cement, were prepared. The influence of the plugging agent on the flow field and the force exerted on the solid under the action of the fluid was analyzed using fluid-solid coupling software. The simulation results show that when subjected to a flow rate of 10 m/s, the edge of the cement experiences a significant force, while the stress is not widely transmitted to the middle and rear of the cement. This indicates that the cement has a strong resistance to the fluid flow. The fundamental characteristics of MOC cement and MOS cement, such as compressive strength and setting time, were investigated. The test results show that adjusting the molar ratio of the two types of cements can shorten the setting time by 60% and increase the compressive strength to up to 23 MPa. In addition, the acid solubility of the cement with different ratios of raw materials is above 95%. The plugging performance of these two cements as loss circulation materials was evaluated by using a physical simulation device. The pressure bearing capacity of the MOC cement with different MgO/MgCl2·6H2O/H2O molar ratios ranged between 13.4 and 23.6 MPa. The maximum bearing capacity of the MOS cement can reach up to 18.6 MPa. The results showed that both cements possess excellent plugging and pressure bearing capacity.

Development of industrial technology of plant substance of viburnum opulus fruit liquid extract

Nowadays, the development of domestic herbal medicines for the treatment of diseases of the cardiovascular system remains one of the current problems in the health care system of Ukraine. Some types of plant raw materials that can be successfully used in the complex therapy of cardiovascular diseases include viburnum fruits (Viburnum opulus L.). Pharmacological activity, the antimicrobial, antioxidant and cardioprotective properties of the extract developed on their basis from the fruits of the viburnum opulus fruit liquid extract (VOFLE) have studied by preclinical in vitro researches.
 The aim of the work was the development of industrial technology of the domestic plant substance Viburnum opulus fruit liquid extract (VOFLE) for the purpose of it further introduction into the tablet dosage form.
 Experimental samples of viburnum opulus fruits of domestic origin were used as object of research, harvested in the experimental fields of the Institute of Vegetable and Melon growing of the National Academy of Agrarian Sciences of Ukraine (Kharkiv region) to obtain the plant substance VOFLE. Physicochemical and pharmacotechnological methods of research have been used in our work.
 As a result of physical, chemical and pharmacotechnological researches, a domestic plant substance – Viburnum opulus fruit liquid extract (VOFLE) has been developed and standardized by extracting viburnum fruits (Viburni opuli fructus) by water-ethanol mixture 50% at the general ratio of raw material: extractant – 1:10, the analysis of each production stage of the technological process was carried out in order to establish the main technological parameters that are subjected to monitoring during the introduction of plant substances in industrial production and during the validation of the technological process.
 The technology of the domestic herbal substance viburnum opulus fruit liquid extract (VOFLE) obtaining was theoretically justified and experimentally developed with the aim of its further introduction into a tablet medicinal form of cardioprotective and membrane-stabilizing activity. A technological block diagram was developed with the definition of its main critical stages of the production process of the herbal substance, as well as a production equipment scheme, which was tested in industrial conditions of the LLC «Pharmaceutical Company "Zdorovya"», Kharkiv.

Design of remoldable, shape-memory, welded biomass composites based on the acetal bond of the cellulose chain

The growing environmental concern over petrochemical-based plastics continuously promotes the exploration of green and sustainable biomass-based covalent adaptable networks composites (CANs). Compared with petrochemical products, cellulose and its derivatives have overwhelming superiority in terms of availability, cost and biodegradability; nevertheless, CANs using the abundant acetal bonds in the cellulose chain rather than elaborately designing other types of dynamic covalent bonds still have not received sufficient attention. Herein, we report acetal-based cellulose covalent adaptable networks (ACC) synthesized with poly(ethylene glycol) diglycidyl ether as the crosslinker for hydroxypropyl cellulose and tetrabutylammonium bromide (TBAB) as an accelerant. For the first time, exchangeability of the cellulose chain acetal reversible bonds at elevated temperature have been demonstrated to endow ACC reprocessability, shape memory and welding. The TBAB has been used as an accelerant of dynamic exchange for acetal bonds first and its accelerating mechanism and advantages have also been investigated. In addition, the thermal, mechanical and hydrophilic properties of ACC can be adjusted by simply adjusting the raw material ratio and the ACC has excellent chemical and biodegradability. Hence, ACC will provide new ideas for solving white pollution and building new CANs.

Fabrication of Biobriquettes from Mixture of Palm Fronds and Palm Shells with Varying Binders of Tapioca and Sago Flour

Biobriquettes are products obtained from the compaction process of biomass residue used as fuel and formed by using a binding agent. In this study, the biomass used comprised palm fronds and palm shells. The objective was to determine the characteristics of biobriquettes. The research methodology adopted was quantitative experimentation. Results showed that the highest calorific value of biobriquettes was 6729.92 cal/g (1:3-sago 15%), the lowest moisture content was 1.1168% (1:3-tapioca 10%), the lowest ash content was 9.5232% (1:3-sago 10%) and the highest density was 0.9927 g/cm3 (1:3-tapioca 20%). Based on the test results, it can be concluded that the optimal ratio of raw materials palm fronds to palm kernel shells for biobriquette fabrication is 1:3 with 10% tapioca flour and 10-15% sago flour as binders.

Development of technology production of soft cheese "Mozzarella" on the basis of goat's milk

Among variety of food products, cheeses occupy one of the leading places. It is a concentrated protein product that is easily absorbed by body and has good organoleptic properties. The purpose of research is to develop technology for the production of soft cheese "Mozzarella" based on the optimal ratio of dairy raw materials (cow's and goat's milk) and enriched by food additive - paprika. Soft cheese product "Mozzarella" made from 50 % goat's milk: 50 % cow's milk became the best example. Standard and generally accepted research methods were used in work in accordance with technological scheme and taking into account latest achievements of science and technology. Physico-chemical indicators of finished products are presented. An x-ray spectroscopic analysis of the composition of chemical elements of soft cheese "Mozzarella", made in ratio of goat and cow milk, with addition of paprika, was carried out. The results of research showed that soft cheese contains many macro- and microelements. The product is rich in valuable proteins, vitamins and minerals, such as calcium - 27.21%, phosphorus - 18.80 %, and has high nutritional value. The implementation of the proposed technology in production allows to obtain products oriented to the domestic market. The developed cheese "Mozzarella" expands range of products, has increased nutritional and biological value, improves organoleptic and functional properties of product.

OPTIMIZATION OF NATURAL CATALYSTS IN OIL PRODUCTION FROM PLASTIC WASTE PYROLYSIS

This study was conducted to determine the effect of the amount of catalyst on yield from the pyrolysis of Polypropylene (PP) type plastic waste and to determine the characteristics of plastic waste pyrolysis oil which includes the physical and chemical properties of pyrolysis oil. The physical properties tested include viscosity, fire point, flash point, pour point, density, and water content while the chemical properties are compounds contained in pyrolysis oil using Gas ChromatoChromatography -Massmetry (GCMS) and knowing its calorific value. The research was conducted on the type of High-Density Polyethylene (HDPE), namely Polypropylene (PP) which was hydrolyzed in a batch reactor using an incinerator where heating originated from outside using wood powder and LPG. The ratio of raw materials used is as much as 1 kg of plastic with a variation of zeolite catalyst 0.25; 0.5; 0.75; 1 in kg. The results showed that the more catalysts added, the more pyrolysis oil was produced. The results of measuring oil at LEMIGAS kinematic viscosity at 40oC are 1.556 cST, 42 oC fire point, PMCC 26 o C flash point, pour point -42 o C, density at 15 o C 0.7857 g / cm3, and water content is 507.54 ppm . While the hydrocarbon compounds produced are pentene, heptane, and cyclohexane which have flammable properties. The calorific value produced from this pyrolysis oil is 40.947 Mj / Kg. The maximum amount of plastic oil volume is obtained by using 1 kg of raw material with 1 kg of 955 ml zeolite catalyst.

CHEMICAL STRUCTURE OF THE POLYPHENOL COMPOSITION IN THE LEAVES OF PONTAIN HAWTHORN CRATAEGUS PONTICA

The chemical composition (polyphenols) of the leaves of the Crataegus pontica K. Koch plant has been studied. The process of isolating polyphenols from plant raw materials includes several stages: extraction of raw materials, processing of the extract with organic solvents, evaporation, precipitation of the sum of polyphenols, purification. The increase in the efficiency of the use of raw materials is achieved mainly at the first stage – extraction. The yield of the sum of polyphenols was studied depending on: the composition of the extractant, the extraction modulus, the multiplicity of extraction, the ratio of raw materials – extractant, temperature, thickening conditions, treatment of the aqueous residue with organic solvents, the conditions of precipitation of the sum of polyphenols and their drying. As a result, optimal conditions for the isolation of polyphenols from plant raw materials were selected, and the found condition obtained the sum of polyphenols from the autumn leaves of pontic hawthorn with a yield of 4.5%. Chromatographic study of the isolated fractions revealed that the polyphenols of the ethyl acetate fraction are mainly represented by monomeric catechins, flavonolams and tannins. The sum of polyphenols from the ethyl acetate fraction was divided on a column with sephadex LH-20 using chloroform-methanol as an eluent in various ratios (10 : 1→3 : 1). The structures of the isolated compounds were determined using physicochemical methods. As a result, more than 12 polyphenols were isolated from the leaves of pontic hawthorn, such as quercetin-3-O-β-D-galactopyranoside (hyperoside), quercetin-3-rutinoside, 3,5,7,3',4'-pentaoxyflavone (quercetin), 2-(3,4-dimethoxyphenyl)-7methoxy-3,4-dihydro-2H-chromene-3,4,5,6-tetrol, aрigenin-6-C-glycoside, procyanidin B, (+)-catechin (5,7,3',4'-tetraoxyflavan-3-ol), (-)-epicatechin (5,7,3',4'-tetraoxyflavan-3-ol), ellagic acid, gallic acid, 1-O-galloyl-4-O-catechin-β-D-glucose and caffeic acid ester with 2,3-dihydroxyglutaric acid. Of these, the last two substances were first isolated from this plant.

Optimization of ultrasonic-assisted extraction of polysaccharides from Ulva rigida and evaluation of their antioxidant activity

Ultrasonic-assisted extraction (UAE) of sulfated polysaccharides from the cell walls of Ulva rigida green macroalgae was performed with a central composite design using the independent variables (pH 2–10, extraction temperature 40–80 °C, time 50–130 min and liquid/solid ratio of raw material 15–75 mL/g) with response surface methodology. Optimum conditions were obtained as pH 4.92, extraction temperature 73 °C, time 126 min, and the liquid/solid ratio of the raw material as 68 mL/g. Under these optimum conditions, the experimental yield was obtained as 13.22 %, and the results were close and in harmony with the estimated value of 12.91 %. FT-IR results, especially at the peaks corresponding to wave numbers 850 cm−1 and 1256 cm−1, the tension vibrations of sulfated esters in C-O-S and SO bonds were more clearly observed in the extracted ulvan components. As a result of the SEM images obtained by considering the surface morphology, it was observed that the sulfated polysaccharides from the cell wall were more prominently removed after the lipids were removed and as a result of the precipitation process. While the extracted sulfated polysaccharides showed higher antioxidant activity, although the results were close to each other. The total phenolic content was higher in the extracted sulfated polysaccharides.

Effect of MgO and Al2O3 on High-temperature Stability Performance of High-alumina Cement

High-alumina cement has an important position in refractory materials with its good performance at high temperatures, but its disadvantages such as strength inversion and unstable transformation of hydration products have always limited its development. To clarify the working mechanism of high-alumina cement and improve its high temperature resistance, MgO and Al2O3 were added to the high-alumina cement paste. The optimal design method was used to determine the influence of each factor on the high temperature stability of the cement paste. The mix ratio of raw materials was optimized and the strength change patterns of the specimens under the optimal ratio were verified. From a microstructure perspective, the high temperature evolution of the hardened paste of high-alumina cement was explored using X-ray diffraction, scanning electron microscopy, thermogravimetry, and differential scanning calorimetry. The results show that the introduction of refractory powders, especially Al2O3, can significantly improve the volumetric stability of the cement paste at high temperatures. When the water-cement ratio is 0.20, the admixture of MgO is 5 % or 10 %, and Al2O3 is 20 %, the high temperature volume stability of the cement paste is the best. However, its corresponding mechanical strength is weakened to some extent with an increase in calcinating temperature. Moreover, the structure-property evolution process of cementite under high temperature calcinating conditions was verified by microstructural characterization, especially the influence of the powder on the volume and strength of the cement block at high temperatures. The results of this study can serve as a guide for the development of high-alumina cement and its cementing materials, as well as for the improvement of their properties.

The Effects of Raw Material Ratio and Calorific Value on Gasification Rate from Co-Gasification of Coal and Biomass (Bagasse)

To reduce greenhouse gas pollution by 29% in 2030 and actively fight climate change, Indonesia uses biomass as an alternative energy which can be combined with coal. Bagasse is a relatively abundant biomass that has not been effectively utilized. Bagasse can be used as a more effective alternative energy source if it is processed with co-gasification, which is the conversion of solid fuel into gas from two different fuel materials at the same time to produce syngas. The characteristics of biomass and coal co-gasification are closely linked to reactor type and gasification parameters such as temperature, gasifying agent, and mass ratio. The composition of the produced syngas changes depending on the calorific value of the coal used and the raw material ratio. The amount of syngas produced rises in direct proportion to the amount of biomass, and the quantity of air supplied causes complete combustion, so the syngas content decreases. The impact of the calorific value of the coal used, as well as variations in the ratio of the composition of coal and bagasse, on the supply of oxygen in downdraft type gasification equipment is investigated in this study. Bagasse characteristics identified by proximate and ultimate analysis indicate that this biomass can be used as an alternative source of renewable energy. The co-gasification process with 100% coal raw material has the highest temperature and the longest time; the co-gasification process with 100% sugarcane bagasse raw material has the lowest temperature and the shortest time; and the duration of the flame produced in syngas ranges from 5-6 minutes. The 25% bagasse and 75% coal ratio provided the fastest high temperature in this testing, making it more efficient. The calorific value of coal and biomass determines combustion efficiency, with 5300 cal/gr coal producing heat that lasts longer than 3800 cal/gr and 4500 cal/gr.