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Synthesis and characterization of composites based on expanded vermiculite and ferrite spinels
No full textExpanded vermiculite (EV) is clay, a typical 2:1 phyllosilicate which may be
easily produced from the mineral vermiculite. After expansion EV withholds vermiculites
physical structure but becomes far more porous than vermiculite which is
accredited to the huge increase in the intercalation layer thickness. This feature in
conjunction with the fact that the intercalation layer enriched by intercalation cations
and water was the initial motive for this research, which opened a novel method
for spinels synthesis. Intercalation layer of the EV is utilized as a reaction medium
for the synthesis of Fe3O4, MnFe2O4, CoFe2O4, and FeCrFeO4. While magnetite
is synthesized using the co-precipitation method, others are synthesized using
hydrothermal co-precipitation method. Composites are then characterized by XRD
(X-ray diffraction), FTIR (Fourier transformed infrared spectroscopy), SEM/EDS
(scanning electron microscopy with energy dispersing microscopy) that confirmed
the presence of the ferrite spinels inside the intercalation layer. After performed
synthesis of the spinels, further parameters were determined: the isoelectric point
(IEP), the capacity of cation exchange (CEC) and specific surface area (SSA) is
calculated using Brunauer–Emmett–Teller (BET) adsorption isotherm of each
composite together with matrix material (EV). The composites could be used as
potential adsorbents of heavy metals and/or organic pollutants, and this synthesis
method could be used for producing numerous compounds that are mainly being
produced by solvothermal method or co-precipitation method
Removal of Mn(II) ions from synthetic solution using adsorbents based on apricot and peach shells
No full textManganese occurs naturally in surface and groundwater due to mineral dissolution
and leaching process, but also as a result of human activities such as manganese
ore mining and processing, different alloys and salts production. It is also used as a gasoline
additive, a component in ceramic/glass manufacturing, some agrochemicals (fungicides and
fertilizers). Manganese is an essential element for the functioning of many enzymes and can
serve as an activator of many others, but manganese is not biodegradable, and its bioaccumulation
in living organisms can cause many diseases and disorders. In the present study,
the biosorption efficiency for the manganese ions from synthetic solution by raw and modified
apricot and peach shells has been investigated. These lignocellulosic materials were
obtained from local juice factory, where they have been discharged as the waste. Removal
of manganese ions was investigated using the following biosorbents: raw apricot shells (KK)
(particle size <0.65 mm), modified KK with mixture of 2% alginate and bentonite (KKAlB),
raw peach shells (particle size <100 μm) modified by: 2% alginate (KBAl), 2 mol/L HNO3
(KBM) and with the mixture of 10% FeCl3×6H2O and 0.1 mol/L KOH (KBFe). Experimental
biosorption parameters were: initial concentration of manganese ions: 35 mg/L; m/V ratio: 5
g/L; contact time: 24h and initial pH value of the solutions: 4.5. The results have shown that
KK is the most suitable and cost-effective biosorbent for the removal of manganese ions
from aqueous solution. As apricot shells are widely available in the Republic of Serbia as
food industry waste, application of this biosorbent can help in minimizing waste disposal and
in water treatment at the same time
Kinetika i termodinamika procesa adsorpcije as(v)iz vodenih rastvora na modifikovanom adsorbentu SiO2/APTES/GT
No full textSposobnost adsorpcije silicijum-dioksida, modifikovanog sa (3-aminopropil)trietoksisilanom
(APTES), a zatim sa oksidom železa u obliku getita (GT), korišćene su za uklanjanje As(V). Fazni
sastav, strukturna i površinska/teksturalna svojstva dobijenog adsorbenta analizirani su FE-SEM i
FTIR tehnikama. Adsorpcija As(V) ispitana je u šaržnim uslovima korišćenjem različitog vremena
kontakta, mase adsorbenta i temperature. Koncentracije oksi anjona određene su primenom
atomske apsorpcione spektroskopije (AAS). Za određivanje adsorpcionih kapaciteta korišćeni su
različiti modeli, u kojima se najbolje uklapaju Frojndlihov i Lengmirov model. Dobijen je visok
adsorpcioni kapacitet od 55,987 mgg–1 na 45 °C, što ukazuje da je dobijeni adsorbent efikasan, dok
su termodinamički parametric pokazali spontani endoterman proces
Inovativna i ekološki prihvatljiva tehnologija za dobijanje gelnih premaza na bazi nezasićenih poliestarskih smola sa primenom u građevinskoj industriji
No full textEfficient mercury removal from wastewater by pistachio wood wastes-derived activated carbon prepared by chemical activation using a novel activating agent
No full textAmmonium nitrate (NH4NO3) with explosive characteristics at high temperatures was used as a novel activating reagent to prepare a surface-engineered activated carbon derived from pistachio wood wastes (PWAC). PWAC was characterized and compared with commercial activated carbon (CAC) by textural and morphological properties, surface chemistry, crystal structure, and surface elemental composition. The results indicated that the optimal conditions of PWAC preparation to obtain the highest mercury adsorption capacity were pyrolysis temperature (800 degrees C), pyrolysis time (2 h), and impregnation ratio (5%). PWAC was of highly regular-shaped and well-developed pores and possessed a large surface area (1448 m(2)/g) and high total pore volume (0.901 cm(3)/g). The batch experiments indicated that the adsorption process of Hg(II) was strongly dependent on the solution pH and reached fast equilibrium at approximately 30 min. PWAC (202 mg/g) exhibited a significantly higher maximum adsorption capacity than commercial activated carbon (66.5 mg/g). Adsorbent-adsorbate dispersion interaction plays a major role in the adsorption mechanism, compared to the minor role played by pore filling and reduction mechanism. Overall, ammonium nitrate can be considered a newer activating reagent to prepare promising and low-cost PWAC for effectively Hg(II) removal from water media
Surface-modified phillipsite-rich tuff from the Campania region (southern Italy) as a promising drug carrier: An ibuprofen sodium salt trial
No full textThe encapsulation and delivery of drugs often involves the use of expensive microporous materials, and we have investigated the potential for natural zeolites from the widespread volcanic formations of southern Italy as alternatives to these carriers. Surface-modified natural zeolites (SMNZs) with diverse micellar structures (patchy and complete bilayers) were obtained by using different cationic surfactants [cetylpyridinium chloride (CP-Cl), benzalkonium chloride (BC-Cl), hexadecyltrimethylammonium chloride (HDTMA-Cl), and bromide (HDTMA-Br) with phillipsite-rich tuff from the Campania region (southern Italy)]. Loading and release kinetics tests of sodium ibuprofen (IBU) were carried out with organo-phillipsite composites using Fourier transform infrared spectroscopy (FTIR) and thermal analysis coupled with evolved gas analysis (EGA). Results from these tests were mathematically modeled to evaluate IBU adsorption and release mechanisms. The maximum loaded amount of IBU was attained for organo-phillipsite modified with HDTMABr (PHB), which showed a complete bilayer micellar structure. Whenever a patchy bilayer micellar structure formed, the lowest adsorptions of IBU were observed. Equilibrium adsorption results were fit using Langmuir, Sips, and Toth models. Pseudo-first-order and pseudo-second-order fits to the loading kinetic data provided significant goodness of fit. Good fits to the release kinetic data were obtained using first-order and Weibull equations, shedding new light on the release mechanism of IBU from phillipsite. The active amount of IBU on the modified zeolite surface was almost totally available for pharmaceutical purposes
The effect of CaO and MgO addition and cooling rate on stability of slag obtained after jarosite and neutral leaching residue treatment in the Waelz process
No full textJarosite and neutral leaching residue (NLR) are the greatest environmental problems of hydrometallurgical zinc production due to their high quantity and hazardous content. Pyrometallurgical processes, such as the Waelz process, could be applied to recover valuable metals present in this waste. The paper investigates the possibility of forming environmentally stable Waelz slag after the Waelz process of jarosite and NLR. Waelz slag, obtained using CaO as a conventional alkaline additive in the Waelz process, showed high As and Sb release after the EN 12457-4 standard leaching test. Multiphase equilibrium composition calculations indicated that As and Sb were present as volatile and migratory species in the slag. In order to obtain Waelz slag with more stable matrices that would encapsulate and immobilize pollutants, MgO additions to CaO and different cooling conditions of the slag were further investigated. The efficiency of modification in additives composition and cooling conditions was assessed by EN 12457-4 leaching test and chemical and microstructural characterization (XRF and SEM-EDS analyses) of the Waelz slags. The results show that addition of MgO does not reduce the efficiency of the process, even more it increases leaching resistance of the slags. Concentrations of all investigated metals (As, Ba, Cu, Mo, Pb, Sb, Zn) after the leaching test were below defined limits for non-hazardous waste. Microstructural analyses revealed that MgO remained inert during Waelz process, and thus favoring the formation of amorphous stable structure, which was enhanced by increased cooling rate. All investigated Waelz slags with MgO additions are suitable for further use or safe disposal
Dissolution properties of bioactive glasses containing strontium
No full textBecause of their potential application in bone tissue repair and regeneration, different types of bioactive glasses have been extensively studied. This study has been focused on examination of the dissolution process of two bioactive glass compositions, 42P2O5·40CaO·5SrO·10Na2O·3TiO2 (GSSR5) and 46P2O5·40CaO·SrO·10Na2O·3TiO2 (GSSR1) (mol%). Powdered glass samples were immersed in simulated body fluid (SBF) and kept in a water bath at 37 °C for 21 days under semi-dynamic conditions. The mass loss of glass, normalized concentration of ions and pH values of solutions were determined. Dissolution rates for both glasses were increasing until the 5h mark and after that time the dissolution rates decreased. After the 48 h glass dissolution rates reached the steady state. Measured dissolution rates after 168h for GSSR5 and GSSR1 were 1.13·10-4 gh-1 and 3.61·10-4 gh-1, respectively
Corn silk as a biosorbent for the metal ions removal from the mining, smelting and electroplating wastewater
No full textHeavy metals are widely used in different industries and large volumes of wastewater are discharged in the environment. The agricultural waste materials are efficient for removal the heavy metals ions from the water solutions. In this work, corn silk was used as a biosorbent for the Pb2+, Cu2+ and Zn2+ ions removal from the wastewater originated from the Trepča Mines, Mining and Smelting Basin Bor and electroplating. Corn silk was characterized by a SEM-EDX. The experimental results show that the corn silk can be used as an efficient biosorbent for removal the heavy metals removal from water as well as wastewater solutions
Hydrothermal carbonization of Miscanthus x giganteus: Structural and fuel properties of hydrochars and organic profile with the ecotoxicological assessment of the liquid phase
No full textIn this study, hydrothermal carbonization (HTC) was employed for thermochemical conversion of energy crop Miscanthus x gigcuiteus GREEF et DEU. The effect of process temperatures, in the range between 180 and 220 degrees C, on the relevant characteristics of the obtained products, hydrochars and process waters, was investigated. The obtained results showed that the HTC promotes fuel properties and energy density of the solids regarding the feedstock. Furthermore, temperature governs the lowering of the volatiles, ash, and moisture in hydrochars, making its potential use as solid fuels more beneficial than the miscanthus. FT-IR spectroscopy and thermal analysis confirmed degradation of hemicellulose at temperatures above 200 degrees C, and an increase of the total content of cellulose and lignin in the hydrochars. In general, hydrochar obtained at 220 degrees C exhibited the best combustion characteristics and is, therefore, the most suitable for use as a solid biofuel. However, in the residual liquids, some amounts of fluorene, phenanthrene, fluoranthene, and pyrene were detected. The polluting potential, visible through the growth of TOC, COD and BOD values, of the analyzed process waters, increases with the rise in carbonization temperature. The TOC values (5.8-9.9 gC L-1) were on average lower than those reported for organic wastewaters (> 10 gC L-1). The proportion of hydrocarbons in the process water increases with the increase in the carbonization temperature from 2.92 to 20.9%. Consequently, bioassays with Vibrio fischeri showed a relatively high toxicity of the liquid phase, where a concentration of about 1% was causing bacteria inhibition of 50%