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Dissolution of glass made from coal fly ash, glass cullet and calcium carbonate
No full textCoal fly ash represents huge ecological problem and its reutilization should be considered. Vitrification of coal fly ash could be one of the solutions. The glass was obtained by melting a mixture of coal fly ash, glass cullet and CaCO3 at T = 1500 oC and quenching the melt in air. The chemical durability of the glass was determined by dissolution test in distilled water, HCl and NaOH at T = 95 0C for t = 2 h. It was shown that dissolution rate of glass in distillated water and NaOH is negligible, while in HCl solution was shown significant mass loss
Soil erodibility in European mountain beech forests
No full textForests in Europe are currently not endangered by soil erosion. However, this can change with climate change or with intensified forest management practices. Using a newly established network of plots in beech forests across Europe, the aims of this study were to (i) distinguish soil properties and erodibility indices in relation to bedrock, (ii) determine geochemical properties and organic carbon (C-org) influencing erodibility, and (iii) assess the effect of soil depth on erodibility indices. Seventy-six soil samples from 20 beech forests were collected in 11 countries to quantify soil properties influencing erodibility indices: clay ratio, modified clay ratio, sodium adsorption ratio, and oxides ratio. The results indicate that the dominant soil properties, determined by bedrock, that correlate with forest soil erodibility indices are C-org, pH, electrical conductivity, calcium and sodium ions concentrations, total water-soluble cations, and the percentage of sand. According to the tested indices, soil susceptibility to erosion follows the order granite > andesite > sandstone > quartzite > limestone. Deeper soil horizons on granite are more susceptible to erosion than surface horizons are, but this is not the case for soils on limestones. In conclusion, forest management should consider the predisposition of different soil types to erosion
Optimization of the active component grinding process and hydrophobization of the obtained powder fire extinguisher
No full textThis work presents a grinding process of monoammonium phosphate (MAP) as an active component in a powder fire extinguisher (PFE). The aim was to determine the grinding time for reaching the optimal particle size of MAP necessary for permanent fire extinguishing. MAP grinding was performed by using a laboratory ceramic ball mill and a vibrating cup mill. The grinding process was controlled by sieving using a 100 mu m sieve at precisely defined time intervals. The efficiency of a PFE depends on the share of the-100 mu m fraction of the active component, which has to exceed 60 %. The optimal grain size with 64 % of fraction of particle size-100 mu m was obtained after 33 min of grinding of =3000 mu m mm grain size MAP by using a ball mill (single-stage grinding). In two-stage process, by grinding the same initial MAP sample (=3000 mu m) in the vibro mill for 10 min, powder with the upper limit grain size of 300 mu m and the mean grain diameter of 120 mu m was obtained. This sample with a reduced size was further ground in the ceramic ball mill yielding 67.5 % of the fraction of particle size 100 mu m after 19 min. The total time of the two-stage grinding process was 29 min. By analyzing the grinding time of MAP required to get the lowest required share of the fraction of particle size-100 mu m that provides the effectiveness of formed PFE it can be concluded that 64 % of this fraction was obtained after 33 min of single-stage grinding, while only after 26 min in the two-stage process. Thus, the grinding time was reduced by 7 min indicating certain energy savings. Stability and hydrophobicity of the obtained PFE were achieved by coating with magnesium stearate (MgSt) at the content of 2 % in a ball mill for 15 min. The coating was confirmed by the standardized procedure for verification of PFE hydrophobic properties in contact with water drops. To obtained PFE had component mass ratios of MAP:AS:CC:QS:MgSt=55:20:18:5:2 (AS-ammonium sulfate; CC-calcium carbonate, QS-quartz sand) and was further characterized by chemical and granulometric analyses. The fire extinguishing efficiency of the PFE was tested in controlled conditions, whereby fires were initiated by burning solid materials and flammable liquids. In both cases, immediate elimination of flames was achieved, thus proving the efficiency of the PFE obtained in this work for practical applications.
A nappies management by-product for the treatment of uranium-contaminated waters
No full textThe direct disposal of municipal solid waste such as nappies to the environment may create serious pollution problems. Based on the circular economy and waste management concepts, the conversion of nappies and/or their ingredients (such as super absorbent polymer (SAP)) to high added value products is of great importance. In this work, a modified SAP (MSAP) was examined as an adsorbent for treatment of contaminated waters and uranium recovery. Batch experiments and spectroscopic techniques were used to examine the effect of various parameters (pH, contact time, temperature, initial concentration, and ionic strength), and the mechanism of adsorption U(VI) and desorption process. The U(VI) concentration was determined by alpha spectroscopy after addition of U-232 standard tracer solution to account for possible interferences during electrodeposition and alpha particle counting. The maximum adsorption monolayer capacity was found to be 217.4 mg/g at pH 4.0 and at 298 K. The adsorption of U(VI) on MSAP seems to occur mainly via the formation of inner-sphere surface complexes between U(VI) and the carboxylic surface moieties of MSAP. The MSAP could satisfactorily be regenerated with 0.1 M Na2CO3 (>90%) and it also shows a promising applicability to real wastewaters contaminated with U(VI)
Effect of sintering temperature on the compressive strength and microstructure of glass foam made from waste materials
No full textGlass foams were produced from a green beer bottle and sugar beet factory lime (SBFL) as the foaming agent. The sintering temperature was in 750-900 oC range. Porosity and compressive strength were determined. Results showed that glass foam sintered at 750 °C has the best compressive strength and even distribution of pores throughout the volume of the sample. The increase of temperature from 800 to 900 °C compressive strength was improved while porosity has slightly dropped. Pores with diameters greater than 1000 µm were formed due to pore agglomeration. Obtained glass foams have properties comparable to commercial ones and could be used for sound and thermal insulation
Manufacture and characteristics of shape memory alloys for electronic purposes
No full textAmong the variety of advanced materials with exceptional properties and applications, shape
memory alloys (SMAs) have a unique ability to return to previously defined shapes or sizes if subjected
to the relevant thermal treatment. The memory effect can be reached only in the presence of
specific phase transformation, reversible austenite to the martensite phase. There are several basic
types of SMAs, such as Ni-Ti (nitinol), Cu-based, and Fe-based alloys. The economic effect (low
price) is the main advantage of Cu-based SMAs compared with other SMAs. Namely, these Cu-Al-Ni
alloys can be applied in various industrial fields, especially when high transformation temperatures
are required (near 200 °C), thanks to their excellent thermal stability and high transformation temperatures.Među mnogim naprednim materijalima sa izuzetnim svojstvima i primenom, legure sa memorijom
oblika (SMA) imaju jedinstvenu sposobnost da se vrate prethodno definisanim oblicima ili
veličinama ako su podvrgnute odgovarajućoj termičkoj obradi. Memorijski efekat se može postići
samo u prisustvu specifične fazne transformacije, reverzibilnog prelaza iz austenita u martenzit. Postoji
nekoliko osnovnih tipova SMA, kao što su Ni-Ti (nitinol), legure na bazi Cu i legure na bazi Fe.
Ekonomski efekat (niska cena) je glavna prednost SMA na bazi Cu u poređenju sa drugim SMA.
Naime, ove Cu-Al-Ni legure mogu se primeniti u različitim industrijskim poljima, posebno kada su
potrebne visoke temperature transformacije (blizu 200 ° C), zahvaljujući njihovoj odličnoj termičkoj
stabilnosti i visokim temperaturama transformacije
Močvarna zemljišta kao prirodna zaštita od poplava
No full textБорба против поплава је велики изазов људске заједнице од формирања првих насеља. У превенцији поплава изузетан значај имају мочварна земљишта, због своје способности да упијају огромне количине воде. Поред тога, мочварна земишта су станишта великог броја животињских и биљних врста, а веома значајна је и њихова
економска, културна, научна и рекреативна вредност. Упркос свему, мочварна
земљишта су масовно исушивана и превођена у друге намене, што је нанело непоправљиву штету по биодиверзитет и довело до повећања опасности од поплава.
Тек у последњих педесетак година чине се напори на глобалном нивоу како би се
заштитиле мочваре и биодиверзитет у њима.The fight against floods has been a great challenge for the human community since
the formation of the first settlements. Wetlands are extremely important in flood prevention due to their ability to absorb huge amounts of water. In addition, wetlands are habitats for numerous animal and plant species, and their economic, cultural, scientific and recreational
value are also significant. Despite everything, the wetlands had been massively drained and transferred to other purposes, which caused irreparable damage to biodiversity and which brought to an increased risk of floods. Only in the last fifty years have efforts been made at
the global level to protect wetlands and biodiversity in them
Application of medicinal plants in phytoremediation technologies
No full textSociety intensively attempts to face worldwide environmental health issues menacing soil, water, and other
environmental media, especially in the last decades. One of the major threads and the most substantial
concerns are heavy metals, known for their high toxicity and difficult degradability. The need for an
efficient, low-cost, and sustainable approach to this problem led to the development of phytoremediation.
This promising remediation strategy implies plant species utilization to isolate contaminants and minimize
environmental risks. Plants able to inhabit contaminated sites and accumulate extraordinarily high
concentrations of heavy metals, with no toxic effects, are called hyperaccumulators. Some of them belong
to the group of aromatic and medicinal plants, containing natural substances widely used in food, cosmetics,
and farmaceutical industries. Owing to the secondary metabolites biosynthesis and distinctive
morphological features, medicinal plants with phytoremediation capabilities seem to be one of the possible
choices for utilization in the remediation of contaminated lands. According to the published data, the most
suitable aromatic plants for heavy metal contaminated soils remediation belong to the families: Asteraceae,
Geraniaceae, Poaceae, and Lamiaceae. As researches revealed, the percentage yield of the essential oil
(EO) distilled from the medicinal plants enhances with the increased heavy metal stress. Besides, it has
turned out that heavy metals do not significantly contaminate essential oils, contrary to the expected. Thus,
medicinal and aromatic plants hold great phytoremediation potential while simultaneously enabling the
production of essential oils. Their usage has been proposed as feasible and profitable, providing multiple
benefits from both environmental and economic aspects
Preparation and Characterization of the Sulfur-Impregnated Natural Zeolite Clinoptilolite for Hg(II) Removal from Aqueous Solutions
No full textSulfur-impregnated zeolite has been obtained from the natural zeolite clinoptilolite by chemical modification with Na2S at 150 degrees C. The purpose of zeolite impregnation was to enhance the sorption of Hg(II) from aqueous solutions. Chemical analysis, acid and basic properties determined by Bohem's method, chemical behavior at different pH(o) values, zeta potential, cation-exchange capacity (CEC), specific surface area, X-ray powder diffraction (XRPD), scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), as well as thermogravimetry with derivative thermogravimetry (TG-DTG) were used for detailed comparative mineralogical and physico-chemical characterization of natural and sulfur-impregnated zeolites. Results revealed that the surface of the natural zeolite was successfully impregnated with sulfur species in the form of FeS and CaS. Chemical modification caused an increase in basicity and the net negative surface charge due to an increase in oxygen-containing functional groups as well as a decrease in specific surface area and crystallinity due to the formation of sulfur-containing clusters at the zeolite surface. The sorption of Hg(II) species onto the sulfur-impregnated zeolite was affected by the pH, solid/liquid ratio, initial Hg(II) concentration, and contact time. The optimal sorption conditions were determined as pH 2, a solid/liquid ratio of 10 g/L, and a contact time of 800 min. The maximum obtained sorption capacity of the sulfur-impregnated zeolite toward Hg(II) was 1.02 mmol/g. The sorption mechanism of Hg(II) onto the sulfur-impregnated zeolite involves electrostatic attraction, ion exchange, and surface complexation, accompanied by co-precipitation of Hg(II) in the form of HgS. It was found that sulfur-impregnation enhanced the sorption of Hg(II) by 3.6 times compared to the natural zeolite. The leaching test indicated the retention of Hg(II) in the zeolite structure over a wide pH range, making this sulfur-impregnated sorbent a promising material for the remediation of a mercury-polluted environment
The effect of composition on chemical durability of phophate glass fertilizers
No full textPhosphate glassy fertilizers are the new type of advanced and controlled released fertilizer, whose glassy matrixes consist of macroelements (K, P, Mg, Ca) most useful for plants and microelements (Fe, Cu, Zn, Mn) which are important to the growth and development of plants. The flexibility of glasses enables the variation of their composition and properties over a wide range. The dissolution behavior of glasses from the P2O5-SiO2-K2O-CaO-MgO system doped with various microelements in bidistilled water and the 2% aqueous solution of citric acid under static conditions was studied. The leaching tests were performed with glass powder samples (0.3–0.65 mm) at T=37 °C for periods up to 480 h. The samples mass loss, the changes of pH, as well as the concentration of elements in solution were determined