Pub Date : 2021-01-01DOI: 10.2298/hemind210409018p
J. Petrović, S. Mladenović, A. Ivanović, I. Marković, S. Ivanov
In this work, the stir casting method was applied to obtain composites based on the alloy AN EW 6061 used as a metal base, and Al2O3 particles as a reinforcement. Composites play a significant role as engineering materials. Therefore, it is necessary to study, in detail, the production methods and the factors that affect their mechanical properties. For this purpose, we have carried out a planned experiment wi ASM International th the aim to use regression analysis to predict the influence of particle size and mass fraction on hardness of the obtained composites. The full factorial experimental design with two factors was used, which was analyzed at three levels. Hardness was observed as a system response, while particle size and mass fraction were set as influencing factors. Influencing factors were observed at three levels: 50, 80 and 110 ?m for the particle size and 2, 5 and 8 mass%. Measured hardness values of the composites ranged from 72 HV10 to 80 HV10. Based on the probability values (p<0.05), it was determined which factors are important for the system response. Statistical analysis has shown that linear terms of the influence factors (size and mass fraction of reinforcement particles) and the square term of the mass fraction have statistical significance on the hardness change. The square term of the particle size and the interaction term of the influencing parameters do not have a statistically significant contribution in predicting the hardness value. Thus, a second-order polynomial model was obtained by the regression analysis. Influence of input factors on the system response and the adequacy of the obtained mathematical model were determined by using the Analysis of Variance (ANOVA). Based on the statistical data analysis, it was established that, the particle mass fraction has a greater influence on hardness of the obtained composite in relation to the particle size. By comparing the experimental and predicted values, a high degree of agreement was achieved so that the chosen model of the factorial experiment was adequate (R2=0.989). It can be also concluded that the developed regression model can be applied to predict hardness of the aluminum composite reinforced by Al2O3 particles in the chosen variation interval of particle size and mass fraction.
{"title":"Correlation of hardness of aluminum composites obtained by stir casting technology and the size and weight fraction of reinforcing Al2O3 particles","authors":"J. Petrović, S. Mladenović, A. Ivanović, I. Marković, S. Ivanov","doi":"10.2298/hemind210409018p","DOIUrl":"https://doi.org/10.2298/hemind210409018p","url":null,"abstract":"In this work, the stir casting method was applied to obtain composites based on the alloy AN EW 6061 used as a metal base, and Al2O3 particles as a reinforcement. Composites play a significant role as engineering materials. Therefore, it is necessary to study, in detail, the production methods and the factors that affect their mechanical properties. For this purpose, we have carried out a planned experiment wi ASM International th the aim to use regression analysis to predict the influence of particle size and mass fraction on hardness of the obtained composites. The full factorial experimental design with two factors was used, which was analyzed at three levels. Hardness was observed as a system response, while particle size and mass fraction were set as influencing factors. Influencing factors were observed at three levels: 50, 80 and 110 ?m for the particle size and 2, 5 and 8 mass%. Measured hardness values of the composites ranged from 72 HV10 to 80 HV10. Based on the probability values (p<0.05), it was determined which factors are important for the system response. Statistical analysis has shown that linear terms of the influence factors (size and mass fraction of reinforcement particles) and the square term of the mass fraction have statistical significance on the hardness change. The square term of the particle size and the interaction term of the influencing parameters do not have a statistically significant contribution in predicting the hardness value. Thus, a second-order polynomial model was obtained by the regression analysis. Influence of input factors on the system response and the adequacy of the obtained mathematical model were determined by using the Analysis of Variance (ANOVA). Based on the statistical data analysis, it was established that, the particle mass fraction has a greater influence on hardness of the obtained composite in relation to the particle size. By comparing the experimental and predicted values, a high degree of agreement was achieved so that the chosen model of the factorial experiment was adequate (R2=0.989). It can be also concluded that the developed regression model can be applied to predict hardness of the aluminum composite reinforced by Al2O3 particles in the chosen variation interval of particle size and mass fraction.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82705566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind211227032p
E. Editorial
This article has been published under the category Technical paper instead of Original scientific paper by mistake made by the Editorial Office of the journal Hemijska industrija during the proofreading process. Apologies are offered to authors and readers of the journal Hemijska industrija.
{"title":"Errata in the article: Upgrading fuel potentials of waste biomass via hydrothermal carbonization","authors":"E. Editorial","doi":"10.2298/hemind211227032p","DOIUrl":"https://doi.org/10.2298/hemind211227032p","url":null,"abstract":"This article has been published under the category Technical paper instead of Original scientific paper by mistake made by the Editorial Office of the journal Hemijska industrija during the proofreading process. Apologies are offered to authors and readers of the journal Hemijska industrija.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82012570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind210507025p
J. Petrović, M. Simić, M. Mihajlovic, M. Koprivica, M. Kojić, I. Nuić
In recent decades, massive exploitation of fossil fuels caused a growing demand for the production of energies from renewable sources. Hydrochar obtained from waste biomass via hydrothermal carbonization (HTC) possesses good potentials as a biofuel. Therefore, we performed HTC of corn cob, paulownia leaves, and olive pomace at different temperatures (180, 220, and 260 oC). The main goal of this study was to comparatively evaluate the influence of HTC conditions on the structure and fuel characteristics of the obtained solids. The results showed that the yields of hydrochar decrease significantly with increasing temperature in all samples. The carbon content and higher heating value increased and reached the highest values in hydrochars obtained at 260 oC, while the content of volatile matter decreased. Furthermore, the Van Krevelen diagram reveals that the transformation of feedstock to lignite-like products upon HTC was achieved. In this study, the results showed that processes of dehydration and decarboxylation during HTC provoke intensive biomass transformation and that hydrochars obtained at higher temperatures have significantly enhanced fuel properties and fewer volatiles compared to the feedstock.
{"title":"Upgrading fuel potentials of waste biomass via hydrothermal carbonization","authors":"J. Petrović, M. Simić, M. Mihajlovic, M. Koprivica, M. Kojić, I. Nuić","doi":"10.2298/hemind210507025p","DOIUrl":"https://doi.org/10.2298/hemind210507025p","url":null,"abstract":"In recent decades, massive exploitation of fossil fuels caused a growing demand for the production of energies from renewable sources. Hydrochar obtained from waste biomass via hydrothermal carbonization (HTC) possesses good potentials as a biofuel. Therefore, we performed HTC of corn cob, paulownia leaves, and olive pomace at different temperatures (180, 220, and 260 oC). The main goal of this study was to comparatively evaluate the influence of HTC conditions on the structure and fuel characteristics of the obtained solids. The results showed that the yields of hydrochar decrease significantly with increasing temperature in all samples. The carbon content and higher heating value increased and reached the highest values in hydrochars obtained at 260 oC, while the content of volatile matter decreased. Furthermore, the Van Krevelen diagram reveals that the transformation of feedstock to lignite-like products upon HTC was achieved. In this study, the results showed that processes of dehydration and decarboxylation during HTC provoke intensive biomass transformation and that hydrochars obtained at higher temperatures have significantly enhanced fuel properties and fewer volatiles compared to the feedstock.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88992113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/HEMIND200809009N
Nurazira Nor Mohd, N. Salih, J. Salimon
Jatropha curcas oil is one of interesting renewable resources for preparation of biolubricants. However, direct application of this oil as a biolubricant is restricted due to its low oxidative stability. This drawback can be overcome by molecule structural redesign through a chemical modification process at its unsaturated functional groups. Jatropha curcas oil was modified via epoxidation, ring opening and esterification processes. Its conversion to the epoxidized oil was performed by using in situ performic acid as a catalyst, then reaction with oleic acid in the presence of p-toluenesulfonic acid as a catalyst in the ring opening process. The final esterification process with oleic acid was catalyzed by sulfuric acid. Molecular structures of the modified oil were determined by measurements of the oxirane oxygen content and by Fourier-transform infrared (FTIR), proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR) spectroscopy analyses. The results showed that the oxidative stability, viscosity, flash point and pour point of the final product were significantly improved. In specific, the ring opening and esterification processes inducing branching and bending in the final oil molecular structure have resulted in the improved viscosity index of 135, the pour point of -29?C and the increased flash point of 250?C.
{"title":"Chemically modified Jatropha curcas oil for biolubricant applications","authors":"Nurazira Nor Mohd, N. Salih, J. Salimon","doi":"10.2298/HEMIND200809009N","DOIUrl":"https://doi.org/10.2298/HEMIND200809009N","url":null,"abstract":"Jatropha curcas oil is one of interesting renewable resources for preparation of biolubricants. However, direct application of this oil as a biolubricant is restricted due to its low oxidative stability. This drawback can be overcome by molecule structural redesign through a chemical modification process at its unsaturated functional groups. Jatropha curcas oil was modified via epoxidation, ring opening and esterification processes. Its conversion to the epoxidized oil was performed by using in situ performic acid as a catalyst, then reaction with oleic acid in the presence of p-toluenesulfonic acid as a catalyst in the ring opening process. The final esterification process with oleic acid was catalyzed by sulfuric acid. Molecular structures of the modified oil were determined by measurements of the oxirane oxygen content and by Fourier-transform infrared (FTIR), proton and carbon nuclear magnetic resonance (1H NMR and 13C NMR) spectroscopy analyses. The results showed that the oxidative stability, viscosity, flash point and pour point of the final product were significantly improved. In specific, the ring opening and esterification processes inducing branching and bending in the final oil molecular structure have resulted in the improved viscosity index of 135, the pour point of -29?C and the increased flash point of 250?C.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75911973","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind210514029l
Zorica R. Lopičić, J. Avdalović, J. Milojković, Ana Antanasković, Marija Lješević, N. Lugonja, T. Šoštarić
Water contaminated with diesel oil represents one of the greatest challenges in waste water management. Water soluble fraction (WSF) is of particular interest because of its toxicity to aquatic organisms and discharge regulations set by environmental authorities. Biochar sorbents have attracted great attention, due to their low cost origin and advantageous properties as well as high sorption capacities in sorption processes. In this study, we have reported the synthesis and characteristics of novel biochar sorbent made from waste lignocellulosic biomass (peach stones (PS)) and evaluated its possible application in removal of diesel WSF from synthetic water. Physiochemical characteristics of the biochar sample were analysed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) method, and Fourier-transform infrared spectroscopy (FTIR), along with the elemental analysis. Characterisation of PS biochar (PS-B) indicated high multi porous surface area (159.1 m2 g-1) with the average pore diameter 2.7 nm. FTIR results indicated higher presence of aromatic compounds in PS-B as compared to PS. The sorption experiments performed in a batch system using PS-B resulted in more than 95 % removal of diesel WSF, reaching equilibrium after 5 h. Equilibrium data were well fitted by Freundlich isotherm, while the pseudo-second order equation fitted well the kinetic data, indicating chemisorption involving valency forces through the sharing/exchange of electrons between the sorbent and PS-B. Applications of ecotoxicology tests based on a microbial biosensor (Aliivibrio fischeri) have shown a significant toxicity reduction of water sample after the treatment with biochar.
{"title":"Removal of diesel pollution by biochar - support in water remediation","authors":"Zorica R. Lopičić, J. Avdalović, J. Milojković, Ana Antanasković, Marija Lješević, N. Lugonja, T. Šoštarić","doi":"10.2298/hemind210514029l","DOIUrl":"https://doi.org/10.2298/hemind210514029l","url":null,"abstract":"Water contaminated with diesel oil represents one of the greatest challenges in waste water management. Water soluble fraction (WSF) is of particular interest because of its toxicity to aquatic organisms and discharge regulations set by environmental authorities. Biochar sorbents have attracted great attention, due to their low cost origin and advantageous properties as well as high sorption capacities in sorption processes. In this study, we have reported the synthesis and characteristics of novel biochar sorbent made from waste lignocellulosic biomass (peach stones (PS)) and evaluated its possible application in removal of diesel WSF from synthetic water. Physiochemical characteristics of the biochar sample were analysed by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) method, and Fourier-transform infrared spectroscopy (FTIR), along with the elemental analysis. Characterisation of PS biochar (PS-B) indicated high multi porous surface area (159.1 m2 g-1) with the average pore diameter 2.7 nm. FTIR results indicated higher presence of aromatic compounds in PS-B as compared to PS. The sorption experiments performed in a batch system using PS-B resulted in more than 95 % removal of diesel WSF, reaching equilibrium after 5 h. Equilibrium data were well fitted by Freundlich isotherm, while the pseudo-second order equation fitted well the kinetic data, indicating chemisorption involving valency forces through the sharing/exchange of electrons between the sorbent and PS-B. Applications of ecotoxicology tests based on a microbial biosensor (Aliivibrio fischeri) have shown a significant toxicity reduction of water sample after the treatment with biochar.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77739215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind210526028v
Ana V. Veličković, Jelena M. Avramović, Milan Kostic, J. Krstić, Olivera Stamenković, V. Veljković
Wheat straw ash (WSA) was investigated as a new catalyst in biodiesel production from sunflower oil. The catalyst was characterized by temperature-programmed decomposition, X- ray powder diffraction, Hg porosimetry, N2 physisorption, and scanning electron microscopy - energy dispersive X-ray spectroscopy methods. The methanolysis reaction was tested in the temperature range of 55?65?C, the catalyst loading range 10?20 % of the oil weight, and the methanol-to-oil molar ratio range 18 : 1?24 : 1. The reaction conditions of the sunflower oil methanolysis over WSA were optimized by using the response surface methodology in combination with the historical experimental design. The optimum process conditions ensuring the highest fatty acid methyl esters (FAME) content of 98.6 % were the reaction temperature of 60.3?C, the catalyst loading of 11.6 % (based on the oil weight), the methanol-to-oil molar ratio of 18.3 :1, and the reaction time of 124 min. The values of the statistical criteria, such as coefficients of determination (R2 = 0.811, R2 = 0.789, R2 = 0.761) and the mean relative percent deviation (MRPD) value of 10.6 % (66 data) implied the acceptability and precision of the developed model. The FAME content after 4 h of reaction under the optimal conditions decreased to 37, 12, and 3 %, after the first, second, and third reuse, respectively.
{"title":"Modeling the biodiesel production using the wheat straw ash as a catalyst","authors":"Ana V. Veličković, Jelena M. Avramović, Milan Kostic, J. Krstić, Olivera Stamenković, V. Veljković","doi":"10.2298/hemind210526028v","DOIUrl":"https://doi.org/10.2298/hemind210526028v","url":null,"abstract":"Wheat straw ash (WSA) was investigated as a new catalyst in biodiesel production from sunflower oil. The catalyst was characterized by temperature-programmed decomposition, X- ray powder diffraction, Hg porosimetry, N2 physisorption, and scanning electron microscopy - energy dispersive X-ray spectroscopy methods. The methanolysis reaction was tested in the temperature range of 55?65?C, the catalyst loading range 10?20 % of the oil weight, and the methanol-to-oil molar ratio range 18 : 1?24 : 1. The reaction conditions of the sunflower oil methanolysis over WSA were optimized by using the response surface methodology in combination with the historical experimental design. The optimum process conditions ensuring the highest fatty acid methyl esters (FAME) content of 98.6 % were the reaction temperature of 60.3?C, the catalyst loading of 11.6 % (based on the oil weight), the methanol-to-oil molar ratio of 18.3 :1, and the reaction time of 124 min. The values of the statistical criteria, such as coefficients of determination (R2 = 0.811, R2 = 0.789, R2 = 0.761) and the mean relative percent deviation (MRPD) value of 10.6 % (66 data) implied the acceptability and precision of the developed model. The FAME content after 4 h of reaction under the optimal conditions decreased to 37, 12, and 3 %, after the first, second, and third reuse, respectively.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88981147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind201128020m
Yam Morales, N. Herrera, K. Pérez
Lithium has become a metal of enormous interest worldwide. The extensive use of rechargeable batteries for a range of applications has pushed for rapid growth in demand for lithium carbonate. This compound is produced by crystallization, by reaction with lithium chloride (in solution) and by adding sodium carbonate. Low sedimentation rates in the evaporation pools present a problem in the crystallization process. For this reason, in this work, mineral sedimentation tests were carried out with the use of two flocculant types with different ionic charges. The tests were carried out at a laboratory level using different dosages for each flocculant and measurements were performed to obtain the increase in the content of solids in the sediment. The anionic flocculant had better performance as compared to that of the cationic flocculant, increasing the sedimentation rate of lithium carbonate by up to 6.5. However, similar solids contents were obtained with the use of the cationic flocculant at 3.5 times lower dosage making it the flocculant of choice regarding the economic point of view.
{"title":"Lithium carbonate sedimentation using flocculants with different ionic bases","authors":"Yam Morales, N. Herrera, K. Pérez","doi":"10.2298/hemind201128020m","DOIUrl":"https://doi.org/10.2298/hemind201128020m","url":null,"abstract":"Lithium has become a metal of enormous interest worldwide. The extensive use of rechargeable batteries for a range of applications has pushed for rapid growth in demand for lithium carbonate. This compound is produced by crystallization, by reaction with lithium chloride (in solution) and by adding sodium carbonate. Low sedimentation rates in the evaporation pools present a problem in the crystallization process. For this reason, in this work, mineral sedimentation tests were carried out with the use of two flocculant types with different ionic charges. The tests were carried out at a laboratory level using different dosages for each flocculant and measurements were performed to obtain the increase in the content of solids in the sediment. The anionic flocculant had better performance as compared to that of the cationic flocculant, increasing the sedimentation rate of lithium carbonate by up to 6.5. However, similar solids contents were obtained with the use of the cationic flocculant at 3.5 times lower dosage making it the flocculant of choice regarding the economic point of view.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89387295","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind210527030r
Andjela Radisavljevic, Milica Milutinović, S. Dimitrijević-Branković, P. Uskoković, M. Rajilić-Stojanović
In this study, a spray drying process of yarrow (Achillea millefolium L.) liquid extracts was optimized by using the response surface methodology. The study aimed to determine the influence of temperature (120-195?C), liquid flow rate (3-16.5 cm3 min-1) and dry matter content in the liquid extract (0.3-1.5 %) on the yield of the drying process, the total polyphenols content and the antioxidant activity of the dry powder. Under the tested conditions the yield varied dramatically and ranged from 8 to 75%, while the effects on the polyphenol content and antioxidant activity were lower. The optimized conditions for the maximum antioxidant activity and maximal yield of the dried extract were as follows: temperature of 130?C, liquid flow rate of 7.5 cm3 min-1 and dry matter content of 1.2%. Under the optimal conditions, the yield was 66 %, while there was a slight decrease in the polyphenol content in the dried extract as compared to that in the liquid extract (145 mg of gallic acid equivalents [GAE] per g of the total dry matter vs. 152 mg GAE g-1, respectively). Consequently, antioxidant activity of the dry powder was only slightly reduced as compared to that of the liquid extract (DPPH neutralization was 58 vs. 64 %, respectively). The dried yarrow powder preserved its antimicrobial activity against pathogenic bacteria Staphylococcus aureus (MIC value of 10 mg cm-3) and Pseudomonas aeruginosa (MIC value of 20 mg cm-3).
{"title":"Optimization of spray drying conditions for production of Achillea millefolium extract powder","authors":"Andjela Radisavljevic, Milica Milutinović, S. Dimitrijević-Branković, P. Uskoković, M. Rajilić-Stojanović","doi":"10.2298/hemind210527030r","DOIUrl":"https://doi.org/10.2298/hemind210527030r","url":null,"abstract":"In this study, a spray drying process of yarrow (Achillea millefolium L.) liquid extracts was optimized by using the response surface methodology. The study aimed to determine the influence of temperature (120-195?C), liquid flow rate (3-16.5 cm3 min-1) and dry matter content in the liquid extract (0.3-1.5 %) on the yield of the drying process, the total polyphenols content and the antioxidant activity of the dry powder. Under the tested conditions the yield varied dramatically and ranged from 8 to 75%, while the effects on the polyphenol content and antioxidant activity were lower. The optimized conditions for the maximum antioxidant activity and maximal yield of the dried extract were as follows: temperature of 130?C, liquid flow rate of 7.5 cm3 min-1 and dry matter content of 1.2%. Under the optimal conditions, the yield was 66 %, while there was a slight decrease in the polyphenol content in the dried extract as compared to that in the liquid extract (145 mg of gallic acid equivalents [GAE] per g of the total dry matter vs. 152 mg GAE g-1, respectively). Consequently, antioxidant activity of the dry powder was only slightly reduced as compared to that of the liquid extract (DPPH neutralization was 58 vs. 64 %, respectively). The dried yarrow powder preserved its antimicrobial activity against pathogenic bacteria Staphylococcus aureus (MIC value of 10 mg cm-3) and Pseudomonas aeruginosa (MIC value of 20 mg cm-3).","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87308985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-01DOI: 10.2298/hemind210402022d
N. Djordjevic, M. Vlahović, Sanja Martinović, Slavica Mihajlović, Nenad Vušović, M. Sokić
In this study, a mixture of magnesium oxide and titanium dioxide was mechanically activated in order to investigate the possibility of mechanochemical synthesis of magnesium titanate. Mechanical activation was performed for 1000 min in a high-energy vibro mill (type MH954/3, KHD Humboldt Wedag AG, Germany). The mill is equipped with housing having a horizontally placed shutter. The cylindrical stainless steel working vessel, with inner dimensions of 40 mm in height and 170 mm in diameter, has working elements consisting of two free concentric stainless steel rings with a total weight of 3 kg. The engine power is 0.8 kW. Respecting the optimal amount of powder to be activated of 50-150 g and the stoichiometric ratio of the reactants in the equation presenting the chemical reaction of magnesium titanate synthesis, the starting amounts were 20.2 g (0.5 mol) of MgO and 39.9 g (0.5 mol) TiO2. During the experiments, X-ray diffraction analysis of the samples taken from the reaction system after 60, 180, 330, and 1000 min of mechanical activation was performed. Atomic absorption spectrophotometry was used for chemical composition analysis of samples taken at different activation times. Based on the X-ray diffraction analysis results, it can be concluded that the greatest changes in the system took place at the very beginning of the mechanical activation due to the disturbance of the crystal structure of the initial components. X-ray diffraction analysis of the sample after 1000 min of activation showed complete amorphization of the mixture, but diffraction maxima characteristic for magnesium titanate were not identified. Therefore, the mechanical activation experiments were stopped. Evidently, the energy input was not sufficient to overcome the energy barrier to form a new chemical compound - magnesium titanate. The failure to synthesize magnesium titanate is explained by the low negative Gibbs energy value of -25.8 kJ/mol (despite the theoretical possibility that the reaction will happen), as well as by the amount of mechanical energy entered into the system during activation which was insufficient to obtain the reaction product. Although the synthesis of MgTiO3 was not achieved, significant results were obtained which identify models for further investigations of the possibility of mechanochemical reactions of alkaline earth metals and titanium dioxide.
在本研究中，为了探讨机械化学合成钛酸镁的可能性，机械活化氧化镁和二氧化钛的混合物。机械活化在高能振动磨机(MH954/3型，KHD Humboldt Wedag AG，德国)中进行了1000分钟。磨机配备有一个水平放置的百叶窗的外壳。圆柱形不锈钢工作容器，内部尺寸为40毫米高，直径170毫米，工作元件由两个自由同心不锈钢环组成，总重量为3公斤。发动机功率为0.8 kW。根据钛酸镁合成化学反应方程中反应物的化学计量比和最佳活化粉量50 ~ 150 g，起始量为MgO 20.2 g (0.5 mol)， TiO2 39.9 g (0.5 mol)。实验中，对机械活化60、180、330和1000 min后的反应体系样品进行x射线衍射分析。采用原子吸收分光光度法对不同活化时间的样品进行化学成分分析。根据x射线衍射分析结果可以得出，由于初始组分的晶体结构受到干扰，在机械活化的一开始，体系发生了最大的变化。活化1000 min后样品的x射线衍射分析显示混合物完全非晶化，但没有确定钛酸镁的衍射最大值特征。因此，机械活化实验停止。显然，能量输入不足以克服能量势垒形成新的化合物-钛酸镁。钛酸镁合成失败的原因是-25.8 kJ/mol的负吉布斯能值很低(尽管理论上有可能发生反应)，以及在活化过程中进入系统的机械能不足以获得反应产物。虽然没有实现MgTiO3的合成，但获得了重要的结果，为进一步研究碱土金属与二氧化钛机械化学反应的可能性确定了模型。
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Pub Date : 2021-01-01DOI: 10.2298/HEMIND200710015M
Miona Miljkovic, Sladjana Davidović, A. Djukić‐Vuković, M. Ilić, Milica Simović, M. Rajilić-Stojanović, S. Dimitrijević-Branković
Dextransucrase (DS) is a glucosyltransferase (E. C. 2.4.1.5) that catalyzes the transfer of glucosyl residues from sucrose to dextran polymer and liberates fructose. This enzyme isassociated with a wide application range of dextran and oligosaccharides. DS production by Leuconostoc mesenteroidesT3 was optimized using a Central Composite Design under the Response Surface Methodology. Three variables were chosen for optimization: distillery stillage, sucrose and manganese concentration. The results showed that sucrose and manganese concentrations had a positive linear effect on DS production while all variable interactions (stillage-manganese, stillage-sucrose, and sucrose-manganese) had significant influences on the DS production. The maximal DS yield of 3.391?0.131 U cm-3, was obtained in the medium with 64.33 % distillery stillage concentration, 5.30% sucrose concentration and 0.022 % manganese concentration. Our study revealed the potential of distillery stillage combined with sugar beet molasses, supplemented with sucrose and manganese to be employed as a valuable medium growth for lactic acid bacteria and production of DS. Also, taking into consideration the origin of the substrates, utilization of industrial by-products in this way has a great environmental relevance and is in accordance with circular economy.
右旋蔗糖酶(DS)是一种葡萄糖基转移酶(e.c. 2.4.1.5)，它催化葡萄糖基残基从蔗糖转移到右旋糖酐聚合物并释放果糖。该酶与葡聚糖和低聚糖有广泛的应用范围。采用响应面法下的中心复合设计对Leuconostoc mesenteroidesT3产DS进行优化。选择了3个变量进行优化:蒸馏液、蔗糖和锰浓度。结果表明，蔗糖浓度和锰浓度对稻瘟病菌产量有显著的线性正相关影响，而所有变量交互作用(枯草-锰、枯草-蔗糖和蔗糖-锰)对稻瘟病菌产量均有显著影响。在酒糟浓度为64.33%、蔗糖浓度为5.30%、锰浓度为0.022%的培养基中，DS产率最高为3.391 ~ 0.131 U cm-3。我们的研究揭示了在甜菜糖蜜中添加蔗糖和锰作为乳酸菌生长和DS生产的培养基的潜力。此外，考虑到基材的来源，以这种方式利用工业副产品具有很大的环境相关性，并且符合循环经济。
{"title":"Utilization of agro-industrial by-products as substrates for dextransucrase production by Leuconostoc mesenteroides T3: Process optimization using response surface methodology","authors":"Miona Miljkovic, Sladjana Davidović, A. Djukić‐Vuković, M. Ilić, Milica Simović, M. Rajilić-Stojanović, S. Dimitrijević-Branković","doi":"10.2298/HEMIND200710015M","DOIUrl":"https://doi.org/10.2298/HEMIND200710015M","url":null,"abstract":"Dextransucrase (DS) is a glucosyltransferase (E. C. 2.4.1.5) that catalyzes the transfer of glucosyl residues from sucrose to dextran polymer and liberates fructose. This enzyme isassociated with a wide application range of dextran and oligosaccharides. DS production by Leuconostoc mesenteroidesT3 was optimized using a Central Composite Design under the Response Surface Methodology. Three variables were chosen for optimization: distillery stillage, sucrose and manganese concentration. The results showed that sucrose and manganese concentrations had a positive linear effect on DS production while all variable interactions (stillage-manganese, stillage-sucrose, and sucrose-manganese) had significant influences on the DS production. The maximal DS yield of 3.391?0.131 U cm-3, was obtained in the medium with 64.33 % distillery stillage concentration, 5.30% sucrose concentration and 0.022 % manganese concentration. Our study revealed the potential of distillery stillage combined with sugar beet molasses, supplemented with sucrose and manganese to be employed as a valuable medium growth for lactic acid bacteria and production of DS. Also, taking into consideration the origin of the substrates, utilization of industrial by-products in this way has a great environmental relevance and is in accordance with circular economy.","PeriodicalId":9933,"journal":{"name":"Chemical Industry","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89956638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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