the Chemical Technology最新文献

{"title":"MgO-based cement as an inorganic binder for hemp hurds composites","authors":"N. Stevulova, I. Schwarzová, A. Eštoková, M. Holub","doi":"10.5755/J01.CT.67.1.15000","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.15000","url":null,"abstract":"The aim of this work is to study the suitability of the MgO-based cement as an inorganic binder instead of the traditional Portland cement into composites with an organic filler material such as hemp hurds. MgO-based cements, in contrast to Portland cement which requires high temperatures (about 1450 °C) during its production, demand less energy (the maximum temperature for the controlled calcination to obtain MgO from magnesium carbonate is 750 °C), becoming a more efficient cement from the environmental point of view. The first part of this paper summarises the results of physico-mechanical properties such as density, thermal conductivity, water absorbability and compressive strength of hardened hemp hurds composites that make this material useful and interesting mainly for its thermal insulating properties which can be improved by hemp hurds treatment processes. The second part of this work is devoted to the characterization of the MgO–cement matrix in the 28-day hardening stage. The MgO-based cement as an alternative binder appears to be suitable for the preparation of biocomposites based on hemp hurds. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15000","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"72 1","pages":"24-29"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73870634","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}

{"title":"Influence of silica fume on the workability and hydration process of ultra-high performance concrete","authors":"Evaldas Šerelis, V. Vaitkevičius, Vidas Kerševičius","doi":"10.5755/j01.ct.67.1.15825","DOIUrl":"https://doi.org/10.5755/j01.ct.67.1.15825","url":null,"abstract":"The present article reviews the influence of silica fume on the workability and hydration process of ultra-high performance concrete (UHPC). Silica fume, also known as microsilica (MS) or condensed silica fume, is a by-product of the production of silicon metal or ferrosilicon alloys. Silica fume is one of the most effective pozzolanic additives which could be used for ultrahigh-performance and other types of concrete. According to the literature review, it is not entirely clear which amount of silica fume is optimal, how silica fume affects the hydration process; although the literature is rich in reporting on silica fume, however, most of the scientists are concentrated on workability and compressive strength. The purpose of this research is to extend knowledge on the workability and hydration process of ultra-high performance concrete affected by different amounts of silica fume. For investigation, slump, viscosity, qualitative and quantitative XRD analysis and compression strength tests were applied. The hydration time was reduces by 4.5 hours, and the compressive strength was increased by 30 % (from 95 MPa up to 127 MPa). DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15825","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"35 1","pages":"58-65"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83106164","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}

{"title":"Influence of firing temperature on the chemical properties of hydraulic dolomitic binder","authors":"I. Kiriloviča, I. Vītiņa, S. Igaune-Blumberga, L. Lindiņa","doi":"10.5755/J01.CT.67.1.14986","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.14986","url":null,"abstract":"The synthesis of a binder from the mixture of dolomite flour and clay is investigated. The main anticipated usage of the binder is for the restoration of historical dolomitic Roman cement objects. During the 19 th /20 th century, in the territory of Latvia dolomitic Roman cement was the main hydraulic binder applied for the construction of buildings. It was processed in Riga since 1865 by firing the local raw material dolomitic marlstone below its sintering temperature (800–900 °C) and by fine milling. Because of its fast setting and good water resistance, the material was used mostly for decorative elements of facades. However, since the middle of the 20 th century its production has been stopped. With the aim to provide a compatible material for restoration needs, compositions from dolomite flour and clay were investigated as a perspective raw material for the synthesis of a low-temperature hydraulic binder. Mixtures from two types of clay and dolomite flour in powder state were synthesized. Clay content in the compositions varied from 13 to 30 %. Samples were prepared by mixing the raw materials, semi-dry pressing and firing at 750–950 °C. The study gives an insight into the chemical processes that occur during the synthesis of a binder from a mixture of clay and dolomite flour. Thermochemical processes in the obtained binder depending on production temperature and clay type were compared by using the XRD analysis and a full chemical analysis. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.14986","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"72 1","pages":"19-23"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79212988","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}

{"title":"Quality parameters of fermented kvass extract","authors":"I. Līdums, D. Kārkliņa, A. Ķirse","doi":"10.5755/J01.CT.67.1.15828","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.15828","url":null,"abstract":"The aim of this research was to compare the commercially available kvass concentrate to the kvass extract which was experimentally produced from the naturally fermented kvass. Dry matter was determined according to the standard ISO 2173:2003, active acidity – ISO 10523:2012, and apparent viscosity was measured with a DV-III Ultra Brookfield rheometer, using a spindle SC4-18 with the speed 50 rpm at 26.9 °C. Sugars were determined using high-performance liquid chromatography. The sensory evaluation of kvass drinks (recombined kvass concentrate and extract) was performed according to the ISO 4121:2003. The dry matter content in the kvass concentrate (Ltd. Ilgzeem) was 69 %; it was diluted with distilled water to the dry matter content 32.4 ± 0.2 % of kvass extract (made from Ltd. Liepzeme kvass). Active acidity in the kvass concentrate was significantly ( p = 0.012) lower ( pH 2.86) than in the kvass extract ( pH 4.18). Apparent viscosity in the kvass extract was 13.68 mPa×s and in the kvass concentrate 5.22 mPa×s. Major sugars in the kvass extract were fructose and glucose and in the commercial kvass concentrate – fructose. Hedonic evaluation showed that there were no significant differences ( p > 0.05) in the preference of kvass drinks. The intensity of aroma, flavour and acidity was significantly more pronounced in the kvass drink made from the commercial kvass concentrate. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15828","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"1 1","pages":"73-76"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79742487","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}

{"title":"Investigation of the use of enzyme preparations in leather manufacture","authors":"K. Beleška, J. Širvaitytė, R. Alaburdaitė, I. Komiciute, V. Valeika","doi":"10.5755/J01.CT.67.1.15826","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.15826","url":null,"abstract":"An important component in tanning is the removal of hair from the hide (unhairing), a process which generates considerable amounts of toxic effluent characterized by a high concentration of sulphur, rich mineral compounds, a high alkalinity, and a high organic load. Herewith, the cleaning of unhairing solutions, polluted with lime, sulphides and products of protein degradation remains, is very complicate and expensive. Special attention is paid to lime and sulphides, which are used for beamhouse processes, trying to decrease their amounts or replace them by systems of other materials. Developing new and less polluting technologies of leather processing, it is supposed that components of more environmentally friendly unhairing systems may be enzymatic preparations characterized by a wide spectrum of effects, and, also, oxidizing materials. The presented research is aimed to develop an efficient unhairing system for hides, which contains the oxidation material and the enzyme. Hydrogen peroxide was chosen as a comparatively cheap and environmentally friendly material. Since the action of hydrogen peroxide in the unhairing system depends on its decomposition duration, the decomposition of hydrogen peroxide has been investigated with a modelling medium in the presence of metal ions (Mn 2+ , Fe 2+ , Cu 2+ ). The addition of 28–56 μmol/L of Mn 2+ or Fe 2+ leads to a complete decomposition of hydrogen peroxide during 5–6 hours. The investigation of the unhairing process has shown that the separate use of hydrogen peroxide or the enzyme preparation does not lead to a qualitative unhairing of the hide. An environment-friendly and effective unhairing system has been prepared using hydrogen peroxide 2–4 % on hide mass, the enzyme preparation Aquaderm A 0.2 % on hide mass, and divalent manganese or iron salt in the range of concentration from 28 to 56 μmol/L. A good unhairing effect has been achieved in the following case: a full degradation of the epidermis; an easy hair removal by a slight mechanical action; no damage of the hide surface. The use of the developed unhairing system allows avoiding wastewater pollution by dangerous sulphides and lime. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15826","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"27 1","pages":"66-72"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84664176","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}

{"title":"Synthesis of {2-[1-(4-bromophenyl)-5-oxopyrrolidin-3-yl]-1H -benzimidazol-1-yl}acetic acid hydrazide derivatives","authors":"G. Toliušytė, K. Anusevičius, V. Mickevičius","doi":"10.5755/J01.CT.67.1.15829","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.15829","url":null,"abstract":"First of all, condensation reactions of acetohydrazide with different aldehydes were carried out, 7 hydrazones were obtained. In the presence of acetic acid as a catalyst, reactions of acetohydrazide with 2,4-pentanedione and 2,5-hexanedione yielded pyrazole and pyrrole derivatives, respectively. The reaction of acetohydrazide and carbon disulphide in the presence of potassium hydroxide was carried out, and potassium dithiocarbazate was obtained. The cyclization reaction of potassium dithiocarbazate with hydrazine monohydrate gave 4-amino-1,2,4-triazole. The cyclization reaction of potassium dithiocarbazate was investigated in an acidic medium; 1,3,4-oxadiazole was formed. By the use of regular heating, in the reaction of acetohydrazide with triethyl orthoformate ethyl formohydrazonate was obtained. Triazine was prepared by heating at reflux a mixture of acetohydrazide, ammonium acetate, 1,2-diphenyl-1,2-ethanedione and using 2-propanol as a solvent. In reactions of acetohydrazide with phenyl isocyanate or phenyl thiocyanate, the N -substituted semicarbazide or thiosemicarbazide derivatives were synthesized, respectively. The cyclization reactions of semicarbazide and thiosemicarbazide were carried out in acidic medium - 1,3,4-oxadiazole and 1,3,4-thiadiazole were obtained. Also cyclization reactions of semicarbazide and thiosemicarbazide were investigated in alkaline medium – 1,2,4-triazole derivatives were forme. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15829","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"20 1","pages":"77-85"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85367080","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}

{"title":"Potential utilization of recycled waste paper fibres in cement composites","authors":"N. Stevulova, V. Hospodárova, J. Junák","doi":"10.5755/J01.CT.67.1.15001","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.15001","url":null,"abstract":"This paper deals with the utilization of waste paper fibres in cement composites. The characterization of  waste cellulosic fibres, their processing methods as well as the density and mechanical properties of cement-based composites with the 2 and 5 wt% fibre content of three fibre kinds compared to a composite based on 99.5 wt.% cellulosic fibre and the control sample without fibres are presented. It is shown that the density and mechanical properties of tested fibre-cement composites are affected by cellulosic fibre content and depend on the nature of fibres, their dimension and dispersion in the matrix. The density of each composite with fibre content was checked in a narrow range (1921–1968 kg/m 3 at 2 % and 5 % replacement of the filler). Composites with recycled waste paper fibres had an increasing character in the values of flexural strength up to 14.9 % in comparison with the wood pulp mortar sample. The compressive strength of composites with 2 % of filler replacement reached up to 18 MPa. However, the 5 % replacement of the filler caused a reduction in the compressive strength values to 7.5 % in comparison with the sample containing wood pulp after 28 days of hardening. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15001","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"101 1","pages":"30-34"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80913459","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}

{"title":"Application of waste materials as potential biosorbents for Cu(II) and Zn(II) removal","authors":"M. Holub, M. Bálintová, S. Demcak, P. Pavlíková","doi":"10.5755/J01.CT.67.1.15003","DOIUrl":"https://doi.org/10.5755/J01.CT.67.1.15003","url":null,"abstract":"Mining is probably the most common activity that fundamentally impacts the country. The problems connected with the extraction of sulphide ores arise especially during the final stage of mining, closure and abandonment of the extraction area, when the conditions for the generation of strong acid water are most likely to occur. With respect to the diversity of compounds in acid mine drainage (AMD) and its low pH values it is hard to find an effective and inexpensive “active” treatment process. Recently, numerous approaches have been studied for the development of cheaper and more effective technologies, both to decrease the amount of heavy metals and to improve the quality of the treated effluent. Adsorption has become one of the alternative treatments; in the recent years, the search for low-cost adsorbents that have metal-binding capacities has intensified. Adsorption of heavy metals (Cu and Zn) from single-component aqueous solutions onto non-modified poplar sawdust, hemp shives and peat has been studied using the batch-adsorption techniques. For this purpose, solutions with different concentrations ranging from 10 to 150 mg/L have been used. The study was carried out to examine the adsorption capacity of the low-cost waste materials as potential biosorbents for the removal of heavy metals from acid mine drainage. The adsorption isotherms could be better fitted by the Langmuir model (values of the correlation factor range from 0.974 to 0.997). The values of the separation factor ( R L ) in the present study were found to be within 0.037–0.728, indicating the favorable adsorption process. From the comparison of maximum sorption capacities, it is evident that the best adsorption properties are exhibited by the hemp shives, and copper is overall better adsorbed than zinc ( Q max = 12.84 mg/g and 8.28 mg/g for copper and zinc, respectively). The results indicate that these freely abundant, low-cost waste materials can be treated as economically viable for the removal of metal ions in acidic conditions. DOI: http://dx.doi.org/10.5755/j01.ct.67.1.15003","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"98 1","pages":"40-45"},"PeriodicalIF":0.0,"publicationDate":"2016-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83649443","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}

{"title":"SORPTION CAPACITY INCREASING OF SPENT CATALYST ZEOLITE BY USING H2O2 AND ULTRASOUND","authors":"D. Vaičiukynienė, A. Kantautas, L. Jakevicius, V. Godvišaitė, J. Mockienė, V. Vaičiukynas","doi":"10.5755/J01.CT.66.1.13384","DOIUrl":"https://doi.org/10.5755/J01.CT.66.1.13384","url":null,"abstract":"The synthetic zeolite Y (Na 56 [(AlO 2 ) 56 (SiO 2 ) 136 ]×250H 2 O) is used as an adsorbent for petroleum refining during catalytic cracking, and after a certain time it contaminates and becomes a waste. This waste in Lithuania can make up to 200 tons per year. The EU environmental requirements are becoming stricter, and it is necessary to create the retired absorbent processing methods for the further rational use in manufacturing various products and materials. The waste in this research was activated by integrating in 15 % H 2 O 2 aqueous solution, using 20 kHz ultrasonic processing of 200 W powers. Gas-vapor bubbles are formed in the suspension after the treatment with ultrasound. The temperature inside increases to several thousand degrees and the pressure to thousands of atmospheres. Shock waves appear after the collapse of bubbles. The process in the fluid during cavitation helps crushing zeolite particles, facilitates the separation of impurities and accelerates their oxidation reaction. The zeolite sorption capability increases after treatment with ultrasound, especially using ultrasonic treatment in a hydrogen peroxide solution. In this case, the sorption capacity increases about 2.18 times. Thus, the investigated zeolite waste can be used in environmental protection programs for heavy metal sorption. DOI: http://dx.doi.org/10.5755/j01.ct.66.1.13384","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"24 1","pages":"55-59"},"PeriodicalIF":0.0,"publicationDate":"2015-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78164829","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}

{"title":"FACULTATIVE THERMOPHILIC MICROORGANISMS IN POTATO PRODUCTS IN RETORT PACKAGING","authors":"A. Ruzaike, S. Muizniece-Brasava, K. Kovalenko","doi":"10.5755/J01.CT.66.1.12363","DOIUrl":"https://doi.org/10.5755/J01.CT.66.1.12363","url":null,"abstract":"Thermally treated potato products in retort packaging with an extended shelf-life (up to 90 days before opening) at room temperature (20 ± 1 °C) from two Latvian vegetable processing companies (A and B) were analysed in this research. The aim of this research was to determine the presence of thermotolerant microbial contamination in thermally treated potato products in retort packaging, to ensure their safety and suitability for immediate consumption. Samples from three production batches were used. The total plate count was determined, and a microscopic examination of potato product samples was performed. Microscopic examination of microorganisms showed the presence of microbial vegetative forms in potato products from company B, but the standard investigation did not register them; therefore, Tryptone Glucose Yeast Extract Agar (TGYA), TGYA enriched with 1 % starch solution and TGYA enriched with 5 % starch solution were used for potential microorganism isolation. Samples were incubated at 25 °C; 37 °C; 41.5 °C; 50 °C; 55 °C and 60 °C temperatures under aerobic and anaerobic conditions, incubation time 12, 24 and 48 h. Facultative thermophilic Bacillus licheniformis bacteria which produce thermotolerant spores were isolated from thermally treated potato products in retort packaging from company B. The average colony count in company B samples was 1.27´100 CFU/g (SD = 78.25). The presence of microorganisms was not detected in potato products produced at company A, while facultative thermophilic and thermotolerant microorganisms were found in potato products produced at company B. DOI: http://dx.doi.org/10.5755/j01.ct.66.1.12363","PeriodicalId":22505,"journal":{"name":"the Chemical Technology","volume":"69 1","pages":"19-23"},"PeriodicalIF":0.0,"publicationDate":"2015-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75965477","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}