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Alkali modified corn cob hydrochar as biosorbent of Mn2+ ions from aqueous solutions
No full textIn this study corn cob hydrochar was investigated as potential material for
the biosorption process. The corn cob hydrochar obtained at different carbonization
temperatures (180, 200 and 220°C) were examined as potential adsorbent of Mn2+
from aqueous solution.
The adsorption capacity of corn cob hydrochar obtained at different carbonization
temperatures followed the decreasing order: 220°C > 200°C > 180°C
To enhance adsorption potential, hydrochar with best adsorption abilities obtained
at 220°C (HC) was subjected to cold alkaline modification. The modified
corn cob (M-HC) was prepared through a chemical treatment process using 2M
KOH solution. Preliminary results showed that the M-HC exhibited excellent adsorption
characteristics for Mn2+ removal from aqueous solution. The maximum
adsorption capacity (qmax) of M-HC and HC was 31.83 and 7.83 mg/g, respectively.
It can be concluded that modified corn cob hydrochar can be used as a lowcost,
eco-friendly and promising adsorbent with a good adsorption capacity for Mn
ions removal from aqueous solutions
Toxicity/bioavailability assessment of pesticide contaminated sediments amended with carbonized sugar beet pulp and miscanthus
No full textAquatic sediment represents a sink for toxic and persistent chemicals such as hexachlorobenzene (HCB) and lindane
(γ-HCH). This paper investigates the possibility of reducing the environmental risks associated with the presence of
these pollutants in sediments by amending the sediment with carbonized waste biomass to sequester the contaminants
and render them biologically unavailable. Sugar beet pulp (SB) and miscanthus (M) waste biomass were converted by
thermochemical methods: (1) hydrochar (HTC) - hydrothermal carbonation at three temperatures (180oC, 200oC, 220oC)
and (2) biochar (BC) - slow pyrolysis up to 400oC. The effects of the dose and contact time between the sediment and
the carbon-rich amendments on the effectiveness of the imobilization are estimated. Three doses of carbonized biomass
(1%, 5% and 10%), and three equilibration contact times (14, 90 and 180 days) were investigated. Results have shown
that the bioavailable fraction of γ-HCH and HCB decreased significantly in comparison to the unamended sediment
(from 66.4% for γ-HCH, and 74.6% for HCB, to <2% for both compounds). The sequestration potential of amended
sediment increases in the sequence HTC_SB <HTC_M <BC_SB <BC_M. Additionally, the increase in the HTC prepa⁃
ration temperature further increases sequestration potential and reduction of bioavailable fractions both compounds in
sediment. The increase in the applied dose and the aging time of the prepared mixtures further reduce the bioavailable
fraction, compared to the untreated sediment. Toxicity of amended sediment assessed by Vibrio fishery luminescence in⁃
hibition test and by measuring Zea mays germination and biomass yield was significantly reduced in the BC amended
sediment and increased in the HTC amended sediment. γ-HCH and HCB accumulation in the Zea mays biomass in the
unamended sediment were significantly higher than in the all HTC and BC amended sediment. The obtained results
showed that the remediation potential of the produced biochars and hydrochars significantly depends on (1) the feed⁃
stock characteristics, (2) the process conditions for the conversion of biomass, and (3) the physicochemical properties of
the pollutants
Ispitivanje mehanizma jonske izmene u toku biosorpcije Pb2+, Cu2+ i Zn2+ jona na oklasku kukuruza
No full textU ovom radu ispitan je mehanizam koji se dešava prilikom interakcije jona olova, bakra i cinka sa oklaskom kukuruza. Svi eksperiment izvođeni su u šaržnom sistemu. Kako bi se ispitao sadržaj izmenljivih katjona koji se nalaze u strukturi oklaska kukuruza: K+, Na+, Ca2+, Mg2+ i H+ određen je kapacitet katjonske izmene (KKI). Morfološke karakteristike oklaska kukuruza i promene nastale nakon procesa biosorpcije jona metala ispitane su analizom Skenirajuće Elektronske Mikroskopije sa Energijskom Disperzijom X-zraka (SEM–EDX). Eksperimentalni rezultati ukazuju da se proces biosorpcije Pb2+, Cu2+ i Zn2+ jona na oklasku kukuruza odvija mehanizmom jonske izmene, pri čemu se joni metala najviše izmenjuju sa jonima kalijuma i vodonika
Modified tannins for alkyd based anticorrosive coatings
No full textU ovom radu prikazana je sinteza antikorozionih aditiva na bazi hemijski modifikovanog tanina i njihova primena u alkidnim premazima u cilju poboljšanja antikorozionih svojstava. Prikazane su dve metode modifikacije tanina: direktna modifikacija tanina primenom amonijum-hidroksida, amonijum-hidroksid/amonijum-hlorid pufera ili dietilentriamina (DETA); i dvostepena modifikacija tanina koja u prvom stupnju uključuje modifikaciju epihlorhidrinom sa ciljem da se dobije tannin sa epoksi terminiranim funkcionalnim grupama, ET, i modifikaciju ET tanina sa heteroaromatičnim aminima ili masnim kiselinama izolovanim iz lanenog ulja (LFA) u drugom stupnju. Sintetisani antikorozioni aditivi su okarakterisani primenom ATR-FTIR, 1H i 13C NMR spektroskopija, i elementalnom analizom. Sadržaj epoksi, amino, hidroksilnih i karboksilnih grupa i vrednost jodnog broja sintetisanih aditiva određen je prema standardnim metodama. Alkidni premazi koji sadrže antikorozione aditive na bazi modifikovanog tanina ispitani su prema standardnoj SRPS EN ISO 4628 metodi. Antikorozivni alkidni premazi na bazi modfikovanih tanina pokazali su poboljšane antikorozione karakteristike i adheziju u poređenju sa alkidnim premazom na bazi cink-fosfata. Alkidni premazi koji sadrže dvostepeno modifikovani tanin sa LFA i 2-amino-5-merkapto-1,3,4-tiadiazolom pokazali su najbolje antikorozione karakteristike.The study of the synthesis of anticorrosive inhibitors, based on chemically modified tannins, and their use in alkyd based coatings to improve anticorrosive properties is presented in this work. Two methods of tannin modification were applied: direct method using ammonium hydroxide, ammonium hydroxide/ammonium chloride buffer or diethylenetriamine (DETA); and a two-step method including tannin modification with epichlorohydrin (ECH) in first step to produce epoxy modified tannin, ET, and further modification with heteroaromatic amines or linseed oil fatty acids (LFA) in second step. The obtained anticorrosive additives were characterized using ATR-FTIR, 1H and 13C NMR spectroscopies and elemental analysis. Epoxy, amino, hydroxyl, acid and iodine values of the synthesized inhibitors were determined according to standard methods. The prepared alkyd coating with tannin inhibitors was tested according to standard SRPS EN ISO 4628 method. Anticorrosive coating containing modified tannin based additive showed increased anticorrosive properties, good adhesion and coverage comparing to the coating with zinc phosphate additive. The alkyd coating films based on ET-LFA and ET modified with 2-amino-5-mercapto-1,3,4-thiadiazole showed best anticorrosive results
On the properties of hot forged ti-6al-4v alloy aimed for surgical implants
No full textThe investigation here is aimed to examine the structural and mechanical changes that might have occurred during the hot forging process, a process to obtain a surgical hip implant, and the subsequent heat treatment. Microstructural characterization, morphological and semi-quantitative chemical analyses have been accomplished using an optical and scanning electron microscope. Chemical analyses of all surfaces obtained by the dotted method in all analyzed samples have shown the approximate equal content of aluminum, titanium, vanadium, iron, and silicon. Tensile testing and measurements were following obtained microstructure, showing the uniformity of microstructure and properties along the forging part, as well as over its cross section. All tests proved that hot forging could be a suitable procedure for surgical implants processing
Removal of Cd(II) using hydrochars prepared from substrate for cultivating mushrooms
No full textIn this study, the sorption capacity of Cd (II) removal from aqueous solution was investigated using
hydrochar obtained from substrate for cultivating mushrooms. In order to increase the adsorption
capacity, hydrochar was previously modified with 2M KOH. The obtained results showed that alkally
modification increased the sorption capacity from 41.5 mg/g to 53.5 mg/g. Structural
characterization of alkally modified and unmodified hydrochars were performed by Fourier transform
infrared spectroscopy (FTIR). According to obtained results of FTIR analysis, the increased of the
oxygen functional groups (OFG) in alkally modified hydrochars was observed, which is contributed to
the increase in the adsorption capacity of this hydrochar. Results indicated that substrate for
cultivating mushrooms can be converted into hydrochar as a sorbent for sorption of Cd (II), and the
presence of OFGs play important role in the hydrochar’s high adsorption capacity
Karakterizacija hidročađi poreklom od rezanca šećerne repe i biljke miskantus
No full textCilj ovog rada bila je fizičko-hemijska karakterizacija hidročađi dobijene od rezanca šećerne
repe i biljke miskantus. Fizičko-hemijska karakterizacija je obuhvatala određivanje specifične
površine, zapremine pora, srednjeg radijusa svih pora i površinskog sadržaja ugljenika
ispitivanih materijala. Poređenjem specifičnih površina hidročađi rezanca šećerne repe može se
uočiti da sa porastom temperature raste specifična površina ispitivanih adsorbenata, dok kod
miskantusa sa porastom reakcione temperature specifična površina hidročađi opada. Zapremina
mikro- mezo- kao i ukupna zapremina pora za sve hidročađi raste sa porastom temperature od
180°C do 220°C. Hidročađi miskantusa pokazale su veću zapreminu pora (mikro- mezo- i
ukupnu zapreminu) u odnosu na hidročađ rezanca šećerne repe. Srednji radijus pora hidročađi
poreklom od miskantusa raste sa porastom temperature, dok jasan trend za hidročađ poreklom od
rezanca šećerne repe nije uočen. Na osnovu EDS analize uočeno je da tokom termalne
konverzije raste sadržaj ugljenika za hidročađ rezanca šećerne repe kako raste temperatura
konverzije biomase, dok za hidročađ poreklom od miskantusa nije uočena značajnija promena
sadržaja ugljenika
Organophillipsite as potential low cost adsorbent for removal of ibuprofen
No full textZeolite – phillipsite was modified with long chain organic surfactant – hexadecyltrimethyl-ammonium bromide (HB). Two different amounts of HB were used to modify the zeolitic surface (150 % and 200% of phillisite external exchange capacity - ECEC). Adsorption of non-steroidal antiinflam matory drug – ibuprofen (IBU) was studied at pH 7, at different initial drug concentrations. Adsorption increased with increasing the initial drug concentrations as well as with increasing amounts of organic phase at the phillipsite surface. From the Langmuir model, the maximum IBU adsorption capacity for phillipsite modified with surfactant at 150 % of ECEC was 12.72 mg/g, while for organophillipsite containing surfactant in amount of 200 % of ECEC, the maximum adsorption capacity was 18.25 mg/g
Surface modification of Ti implants by electrophoretic deposition of hydroxyapatite/chitosan/graphene/gentamicin coating
No full textBone diseases and especially prevalent surgical procedures of total joint replacements in
aging population, cause the need for swift development of new biomaterials for bone tissue
implants. Nowadays, Ti implants are by far most commonly used in orthopedics, due to their
excellent mechanical properties and biocompatibility. Having in mind that biomaterials
should stimulate bone tissue regeneration while providing strong support, the Ti implant
surface requires modifications to facilitate improved osteointegration. In this work,
modification of the titanium surface was carried out by depositing novel composite
hydroxyapatite/chitosan/graphene (HAP/CS/Gr) and
hydroxyapatite/chitosan/graphene/gentamicin (HAP/CS/Gr/Gent) coatings. Deposition was
performed by single-step electrophoretic deposition (EPD) technique from aqueous
suspension at constant voltage on pure titanium plates. X-ray diffraction (XRD), Fourier
transform infrared spectroscopy (FT-IR) and field-emission scanning electron microscopy
(FE-SEM) were used to characterize obtained composites and to explore the graphene
influence on the composites properties. The results of all performed analyses confirmed the
formation of new composite HAP/CS/Gr and HAP/CS/Gr /Gent coatings on Ti. Antibacterial
activity kinetics against Staphylococcus aureus and Escherichia coli was performed in order
to evaluate the antibacterial properties of obtained composites. HAP/CS/Gr/Gent coating
exhibited excellent antibacterial properties, justifying the gentamicin addition to composites.
Encouraging results for potential applications were obtained for cytotoxicity testing towards
MRC-5 and L929 cell lines. Good biocompatibility of composites was proven towards both
cell lines, with slightly more pronounced effect for human MRC-5 cell line. Summarizing the
obtained results it could be safe to state that HAP/CS/Gr/Gent composite represents a
prospective material for bone implant coating
Determination of the cavitation resistance of glass-ceramic samples based on raw basalt and industrial waste raw materials for use in metallurgy
No full textThe paper presents the results of the investigation of cavitation resistance of glass-ceramics based on basalt rocks from the Vrelo Kopaonik deposit and various waste industrial raw materials. The aim was to determine the possibility of using glass-ceramics as a substitute for metallic materials in the production of structural elements of mining and metallurgy equipment. The ultrasonic vibration method (with a stationary samples) was used for cavitation resistance testing, according to the ASTM G-32 standard. A change in the sample mass in function of the cavitation time was monitored for the evaluation of cavitation resistance. The level of degradation of the surface of the sample was quantified using the image analysis. The change in the morphology of the sample surface with the test time was followed by scanning electron microscopy