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Reactivity of polyphosphate glass in different medium
No full textInformation about the dissolution process and ion release of phosphate glasses in different environments is important for a wide range of engineering applications, from biomaterial design to environmental technologies. The dissolution of glass is a complex phenomenon and the kinetics of this process depend on the glass properties (composition, structure, surface condition, etc.) and environment (the type of solvent, leaching solution volume, pH, temperature, etc.). The dissolution behavior of glass is determined by the reactions of the glass network and the release of different ions to the solution. Surface conditions and layer formation, saturation effects, and solution chemistry must also be taken into account when describing the dissolution processes. Mechanism of chemical reactivity of a polyphosphate glass (45P2O5·3SiO2·25K2O·15CaO·10MgO·1ZnO·1MnO (mol %)) in distilled water, an aqueous solution of 2% citric acid and SBF, under static and non-saturated conditions were presented. The leaching tests were performed with glass powder samples (0.3–0.65 mm) at T=37 °C for times up to 720 h. The mass loss of the samples, the changes of pH, the concentration of elements (P, K, Ca, Mg, Zn, and Mn) in solution, and the initial release rates (r0i) and rate of glass hydrolysis (rhi) were determined. The time dependence of the normalized concentration of ions in solution indicates that the dissolution of examined glass, for all investigated environments, occurs in three stages. For shorter times (stage I), the changes of the normalized concentration of ions in solution were linear with time, corresponding to the highest dissolution rates. During stage II, the changes of the normalized concentration of ions in solution with time were smaller due to lower dissolution rates. In stage III, the changes of the normalized concentration of ions in solution were very small and the dissolution rates were more than ten times lower compared to the initial rates. The initial release rates of cations were determined in the range of 0.1712.92 g/m2h. The release rates of cations rhi by hydrolysis were determined in the range of 0.13×10-2-2.31×10-2 g/m2h. The time dependence of the solutions' pH is not the same for all of the three solvents. pH value decreased in the initial stage and then remained constant in distilled water and SBF, while in the aqueous solution of 2% citric acid pH value increased in the initial stage and then remained constant
The impact of mineral resources exploitation on the environment
No full textThe paper shows how the exploitation of mineral resources may lead to environmental
degradation. Planning the exploitation of certain mineral raw materials requires a detailed analysis of all
the necessary works in order to fully eliminate or reduce to a minimum any negative impact on the area
where the mining activity is performed. Also, it is important to emphasize that natural resources are very
difficult to renew, so in case of uncontrolled exploitation, danger of permanent loss occurs. Therefore,
the exploitation of mineral raw materials should be based on the principles of sustainable development,
and the measures for the protection of the space where the exploitation is performed should be carried
out according to the prescribed rules and legal provisions
List paulovnije i njegove hidročađi kao potencijalni adsorbenti za uklanjanje jona bakra iz vodenih rastvora
No full textAdsorpcija predstavlja korisnu metodu za uklanjanje zagađivača rastvorenih u vodi. U drvnoj industriji, list paulovnije je bio-otpad koji se dalje može iskoristiti kao biosorbent ili kao izvor za efikasne adsorpcione proizvode. List paulovnije i njegove hidročađi dobijene hidrotermalnom karbonizacijom na tempe- raturama 180, 200 i 220°S su proučavani kao potencijalni adsorbenti jona bakra iz vodenih rastvora. U preliminarnim adsorbcionim testovima je primećeno da je list bez prethodnog tretmana bio efikasniji adsorbent nego njegove hidročađi (qPL=14,75 mg/g; EpL=48,44%). Kinetika adsorbcije korišćenjem lista sledila je model pseudo- drugog reda (R2=0,9984), koji podrazumeva da brzinu procesa kontroliše hemijska adsorpcija
Effective sorption of toxic brilliant green using lignocellulosic waste biomasses and derived biochar samples
No full textLignocellulosic waste biomass (LCW) certainly represents a part of the solutions to the lowcarbon
future. LCW could serve as a base for a variety of sustainable fuels and bio based
materials, whose proper implementation could help in economic and environmental growing
world demands. Fruit stones, wastes from food processing industries, are contributing toward
negative effects on the environment systems through the impacts associated with both waste
production and its disposal. This waste type can be converted into value-added products
using thermochemical methods, such as pyrolysis, where the biomass is efficiently converted
into biofuels, biochars and different value added products. In this paper, two LCW materials,
peach (PS) and cherry stones (CS) and their derived biochars (PS-B and CS-B), have been
successfully applied for the removal of the hazardous water-soluble cationic dye, brilliant
green (BG). Functional groups present in LCWs and related biochars were analysed using
Fourier transform infra-red (FTIR) technique. Bio based sorbents were also characterized by
determination of pHsus and pHpzc. The pristine LCWs, PS and CS, were first milled to
desired dimensions, washed and dried at 60 oC. Pyrolysed samples, PS-B and PS-C, were
obtained by heating in oxygen limited conditions from 25 to 500 оС (10 оС/min heat flow),
and kept at 500 °C for 2 h. The contact pH (pHsus) as well as pHpzc were higher in both
cases for the biochar samples, indicating higher –OH content (confirmed also by FTIR
analysis) and favourable surface for cationic sorbate types. The experimental sorption results
indicated that biochars have almost two times higher sorption capacities than the native
materials, under the same operational conditions, while the highest binding was achieved by
cherry stone biochar, 135.3 mg/g (experimental data modelled by Sips isotherm).
Conclusively, the LCWs derived biochars can be efficiently used as an alternative to
conventional sorbents in contaminated water treatment
Synthesis and characterization of cobalt ferrite/ expanded vermiculite as a sorbent of nickel ions
No full textThe minerals with unique properties such as mica minerals have promising approach in
environmental and industrial sphere. In this study, cobalt ferrite/expanded vermiculite (CoFe2O4/EV)
composite was prepared by in-situ method. Both composite and base materials are characterized by FTIR,
XRD and SEM techniques, while the CEC and point of zero charge (pHPZC) was also determined. The
adsorption properties of CoFe2O4/EV and EV have been investigated in a batch system, for the Ni (II)
sorption from water. Adsorption experimental results were fitted by kinetic and adsorption models, and
resulted in ionic exchange mechanism with maximum adsorption capacity of 23.2mg g-1 (298 K)
Efficiency of water pollution treatment by various adsorption methods - a review
No full textPollution of the environment, especially the water as one of the integral ecosystem's constituents, is a problem of high significance, escalating on a global level. Watercourses are often contaminated by heavy metals, originating from various anthropogenic sources. This study aimed to give a survey on studies conducted on wastewater treatment technologies based on the adsorption mechanism using diverse sorbent types, such as inorganic composite materials, plant biomass, and nanomaterials. Further researches, development of new technologies, and optimization of the existing ones are required for the successful overcoming of the water contamination problem and their wide application in practice
Karakterizacija uzoraka peleta dobijenih postupkom peletizacije krečnjaka i morske alge u različitim odnosima za upotrebu u poljoprivredi
No full textU ovom radu predstavljeni su rezultati fizičko-hemijske karakterizacije kako polaznih uzoraka litotamnijskog krečnjaka i morske alge (ascofyllum nodosum), tako i proizvoda okrupnjavanja njihovih mešavina u različitim odnosima postupkom peletizacije. Polazne uzorke su predstavljali otpadni krečnjak iz filterskih postrojenja, kao i sušena morka alga. Krajnji proizvod okrupnjavanja postupkom peletizacije treba da služi za potrebe poljoprivrede, kao sredstvo za biostimulaciju I ujedno sredstvo za podizanje pH kiselih zemljišta. Dobijeno je nekoliko različitih formulacija peleta postupkom diskontinualne peletizacije, kao i simulacijom kontinualnog procesa peltizacije na peletizacionom tanjiru. Ispitivanja mehaničkih osobina peleta su pokazala da najbolje rezultate pokazuju peleti uzorka 4K, koji su dobijeni kontinualnim postupkom peletizacije sa međusobnim odnosom morske alge i krečnjaka 70:30%
Corn Silk as Biosorbent for Pb, Zn and Cu Removal: Batch and Fixed-bed Column Study
No full textIn this study, the minimization of heavy metal pollution was investigated. Accordingly, potential of corn silk as biosorbent of Pb, Zn and Cu from multimetal solution was considered in batch and fixed-bed column experiments. Structural changes of corn silk before and after heavy metal removal were determined using SEM-EDX and FTIR analyses. For investigation of biosorption performance the Langmuir and Freundlich isotherm models were applied at batch experimental results. Fast biosorption process and high adsorption capacity (0.382; 0.200 and 0.171 mmol g-1 for Pb2+, Cu2+ and Zn2+, respectively) confirmed that the corn silk is suitable for heavy metals removal. In order to produce a novel and improved column package for fixed-column bed study implementation, the corn silk was immobilized with alginate. The fixed-bed column was saturated with Pb-Cu-Zn multimetal solution. The breaktrought time is 95, 100 and 90 min for Pb2+, Cu2+ and Zn2+ respectively, where 87.5, 81.9 and 95.5% Pb2+, Cu2+ and Zn2+ was removed, respectively. Desorption sudy was performed in HNO3 (p.a.) solution where high desorption efficiency (>94%) confirmed that imobilized corn silk can be used as alternative material for metal adsorption and could be applied in purification systems
Copper removal by pelletized fly ash
No full textThe increasing levels of industrial wastewater that are released to the environment present a serious
threat to human health, living resources, and ecological systems. Fly ash was tested for removal of Cu2+ from
contaminated water in in a micronized and pelletized form. Experiments were performed for wide range of initial
concentration of Cu 25-600 mg dm-3. Pellets fraction size was 2.0-3.5 mm, while the content of cement, as a binder
was 10%. Under applied experimental conditions pellets manifested exceptional adsorption capacity (25.64 mg/g)
that was three times higher compared to the micronized fly ash (8.85 mg/g)
DTA/TG analysis and phase changes of activated Na2CO3
No full textSodium carbonate material is used as a good sorbent of carbon dioxide from the atmosphere,
and has gained increasing importance in environmental protection.In order to enhance its
sorption ability, mechanochemicaly activatied sodium carbonate was investigated,and the
occurred changes after the activation and the relaxation time in a controlled environment were
monitored. Activation was performed in a vibro-mill for 2 and 7 minutes, and the activated
samples were placed in an atmosphere of carbon dioxide at a humidity of 95 % for 96 hours,
(the relaxation time). Differential thermal and thermogravimetric analyses were applied with
the aim of determining the changes that occurred on the activated samples during the
relaxation period.The decomposition temperature change of activated Na2CO3 samples, mass
loss, and conversion degree of Na2CO3 to NaHCO3 was monitored depending on activation
and relaxation time periods