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The removal of organic and inorganic sulfur from the Bogovina Basin subbituminous coal by electrochemical redox reactions was performed. The effect of presence of active bromine species on the desulfurization process was monitored. The desulfurization was performed in inorganic acidic solutions that contained different bromide concentrations and in pure acid solution. To determine the optimal conditions for the desulfurization process, polarization curves were recorded in three different electrolytes: 0.1 M H2SO4, 0.1 M H2SO4 + 0.01 M KBr, and 0.1 M H2SO4 + 0.1 M KBr using graphite and dimensionally stable anode (DSA) electrodes as the anode, while in all cases stainless steel S31603 electrode was used as cathode. By analyzing the results obtained from the polarization curves, 0.1 M H2SO4 and 0.1 M H2SO4 + 0.1 M KBr were chosen as the most suitable electrolytes. Also, it was found that the DSA anode showed better results in terms of energy efficiency of the process compared to the graphite anode and therefore it was selected for the coal desulfurization process. It is considered that finely suspended coal particles in an electrolyte can behave according to bipolar electrochemistry. Coal was treated for 4 hours in two selected electrolytes. The suspension was sampled at different times up to 240 min from the beginning of the process. Sulfur content in coal was determined by elemental analysis. The results showed that the sulfur content decreases faster in the case of the electrolyte containing KBr, i.e. that the desulfurization effect is significantly better than in the case of the system containing only H2SO4. It can be concluded that active bromine species accelerate the desulfurization process and thus improve energy efficiency.

Pseudocapacive reaction of ruthenium oxide was investigated by cyclic voltammetry (CV) measurements combined with electrochemical quartz-crystal nanobalance. RuO2 was synthesized by one-pot microwave assisted hydrothermal method. CV measurements were conducted in H2SO4 and Na2SO4 solutions. The ruthenium oxide electrode as a working electrode was prepared by drop casting the water suspension of RuO2 on Au covered quartz electrode. Beside influence of different electrolyte, the effect of thermal treatment of RuO2 was also investigated since pseudocapacitive behaviour of RuO2 strongly depends on its hydrous form. The obtained results were compared to those of commercial RuO2. The results indicate that during the redox reaction of RuO2, various types of charge occur simultaneously. The mass loss or mass gain depends on the specific potential applied and the electrolyte employed., Pseudokapacitivna reakcija rutenijum oksida ispitivana je metodom ciklične voltametrije (CV) u kombinaciji sa primenom elektrohemijske kvarc-kristalne nanovage. RuO2 je sintetizovan jednostepenom hidrotermalnom metodom, pomoću mikrotalasne tehnike. CV merenja su sprovedena u rastvorima H2SO4 i Na2SO4. Elektroda od rutenijum oksida kao radna elektroda je pripremljena nakapavanjem vodene suspenzije RuO2 na zlatom prekrivenu kvarcnu elektrodu. Pored uticaja različitih elektrolita, istražen je i efekat termičkog tetmana RuO2 jer seudokapacitivno ponašanje RuO2 u velikoj meri zavisi od njegovog hidratisanog oblika. Dobijeni rezultati su upoređeni sa rezultatima ispitivanja komercijalnog RuO2. Rezultati pokazuju da se tokom redoks reakcije RuO2 istovremeno javljaju različite vrste naelektrisanja. Gubitak mase ili povećanje mase zavisi od primenjenog potencijala i upotrebljenog elektrolita.

Pseudocapacitance reaction of ruthenium oxide was investigated by cyclic voltammetry (CV) measurements combined with electrochemical quartz-crystal nanobalance. RuO2 was synthesized by one-pot microwave assisted hydrothermal method. CV measurements were conducted in H2SO4 and Na2SO4 solutions. The ruthenium oxide electrode as a working electrode was prepared by drop casting the water suspension of RuO2 on Au covered quartz electrode. Beside influence of different electrolyte, the effect of thermal treatment of RuO2 was also investigated since pseudocapacitive behaviour of RuO2 strongly depends on its hydrous form. The obtained results were compared to those of commercial RuO2. The results indicate that during the redox reaction of RuO2, various types of charge occur simultaneously. The mass loss or mass gain depends on the specific potential applied and the electrolyte employed.

Recently there is an effort to reach highly reversible and stable materials for energy storage processes. Novel materials used in electrochemistry-based energy storage as a suitable supports for noble ones, has been predominant in the past few years. Supercapacitors, as a bridge between batteries and traditional capacitors, have attracted significant attention as new promising energy storage devices. Hybrid nanomaterials based on manganese, cobalt, and lanthanum oxides of different morphology and phase compositions were prepared using a facile single-step ultrasonic spray pyrolysis (USP) process. Transition metal oxides are considered as an ideal electrode materials for electrochemical redox transitions-based pseudocapacitors, because they can provide a variety of oxidation states for rather fast and efficient redox transitions. Strontium-doped lanthanum cobaltites (La1-xSrxCoO3- , LSCO) have shown promising catalytic performance for ORR in alkaline media. The aim of this investigation was to bring detailed insights of supercapacitive potentials of pure LSCO and LSCO hydrothermally doped by RuO2. Also, to separate influences of constituting oxides to this issue, in order to reveal the redox electrochemistry behind perovskite structures as supports for supercapacitive applications.

This paper deals with the deposition of calcium phosphate and hybrid coatings based on calcium phosphate ceramics on titanium with improved properties by in situ anodization/anaphoretic deposition process. Hybrid coatings consisted of chitosan oligolactate (ChOL) and ChOL with Se as immunomodulatory oligoelement. The paper contributes to solving the problem of multi-stage pre-treatment and post-treatment of titanium and oxidized titanium surface to obtain a coating on the substrate, adhesion of the coating, antimicrobial and cytotoxic properties that occur in biomaterials, as well as reduced immune inflammatory response of the organism. The in situ method results in improved adhesion bioactive coating, increased bioactivity and biocompatibility with increased antimicrobial properties and absence of cytotoxicity. The studied biomaterials have improved properties such as: corrosion resistance, absence of toxicity to the human body and adequate strength, which enables their potential use in medicine and dentistry. The innovation is reflected in combining calcium phosphate coating synthesis and surface modification by partially incorporating a ceramic coating into the crystalline structure of the substrate. The characterization of the coatings obtained in this manner was performed by various physico-chemical, biochemical and biological methods. These characterization techniques included: FE-SEM, XRD, FTIR, cytotoxicity and in vivo testing.

This paper deals with the issue of defining a new method of anodizing/anaphoretic deposition for the application of calcium phosphate and hybrid coatings based on calcium phosphate ceramics on titanium and anodized titanium coatings with improved properties. Hybrid coatings consisted of chitosan oligolactate (ChOL) and ChOL with Se as immunomodulatory oligoelement. The paper contributes to solving the problem of multi-stage pre-treatment and posttreatment of titanium and oxidized titanium surface to obtain a coating on the substrate, adhesion of the coating, antimicrobial and cytotoxic properties that occur in biomaterials, as well as reduced immune inflammatory response of the organism. It primarily deals with the creation and optimization of a new in situ anodizing/anaphoretic deposition process for obtaining multifunctional composite biomaterials. The in situ method results in improved adhesion bioactive coating, increased bioactivity and biocompatibility with increased antimicrobial properties and absence of cytotoxicity. The studied biomaterials have improved properties such as: corrosion resistance, absence of toxicity to the human body and adequate strength, which enables their potential use in medicine and dentistry. The aim of the research was to define new in situ anodizing/anaphoretic deposition process and adequate modification of process parameters for application of composite calcium phosphate coatings on titanium and its alloys, wherein innovation is reflected in combining calcium phosphate coating synthesis and surface modification by partially incorporating a ceramic coating into the crystalline structure of the substrate. The characterization of the coatings obtained in this manner was performed by various physico-chemical, biochemical and biological methods. These characterization techniques included: AFM, SEM, FE-SEM, roughness testing, XRD, FTIR, bioactivity, biocompatibility, cytotoxicity, antimicrobial activity and in vivo testing.

The influence of different hydroxides, applied to activate carbon black, on the electrochemical properties of activated carbon was investigated. The carbon material was prepared by hydrothermal treatment of sucrose and afterwards thermally activated using KOH, NaOH and LiOH. The electrochemical properties of the obtained samples were examined by cyclic voltammetry and electrochemical impedance spectroscopy and correlated to their physicochemical properties. All samples showed characteristic capacitor-like behaviour. The highest specific capacitance was obtained for the KOH-treated sample, while the increase in capacitance follows the sequence of the growth of ionic radius of a metal from an alkali which is used for activation. It was found that the dependence on the type of hydroxide is due to differences in the radii of a metal. The alkalies of larger radii of metal generated make pores wider and consequently the structure of a porous layer become more accessible to the charge transfer of capacitive response.

Determination of the extractive behavior of ionic species from lateritic ore leachates is complex, since the leachates are pregnant with tens of different ions in, as a rule, multiple oxide states. To examine the possible pathways of intrinsic electrochemical extraction of the crucial elements Ni and Co, it was necessary to make model solutions of these elements and to subject them to electrochemical examination techniques in order to obtain a benchmark. Beside Ni and Co, the model system for Fe had to be evaluated. Iron, as a dominant ore component by far, is the main interfering factor in the extraction processes of Ni and Co in rather low amounts from leaching solution. The leachate examination results were compared to separate model solutions, as well as to their combinations in concentrations and to pH values comparable to those of the leachate. The separation of the leachate components was initially performed by continuous increase in pH upon leaching with NaOH solution, and afterwards the pH-adjusted solutions were subjected to electrochemical investigation. With the purpose of connecting and quantifying the visual changes in leachate upon increase in pH, conductometric measurements were performed. Reactions of oxidation/precipitations were indicated, which led to the essential Fe removal by precipitation. Resulting solutions were found suitable for Ni and Co electrochemical extraction.

Polygonal Pt nanoparticles were synthesized using ultrasonic spray pyrolysis (USP) at different precursor concentrations. Physicochemical analysis of the synthesized Pt particles involved thermogravimetric, microscopic, electron diffractive, and light absorptive/refractive characteristics. Electrochemical properties and activity in the oxygen reduction reaction (ORR) of the prepared material were compared to commercial Pt black. Registered electrochemical behavior is correlated to the structural properties of synthesized powders by impedance characteristics in ORR. The reported results confirmed that Pt nanoparticles of a characteristic and uniform size and shape, suitable for incorporation on the surfaces of interactive hosts as catalyst supports, were synthesized. It is found that USP-synthesized Pt involves larger particles than Pt black, with the size being slightly dependent on precursor concentration. Among ORR-active planes, the least active (111) structurally defined the synthesized particles. These two morphological and structural characteristics caused the USP-Pt to be made of lower Pt-intrinsic capacitive and redox currents, as well as of lower ORR activity. Although being of lower activity, USP-Pt is less sensitive to the rate of ORR current perturbations at higher overpotentials. This issue is assigned to less-compact catalyst layers and uniform particle size distribution, and consequently, of activity throughout the catalyst layer with respect to Pt black. These features are considered to positively affect catalyst stability and thus promote USP synthesis for improved properties of host-supported Pt catalysts.

Ispitivana su svojstva titan(IV)-oksida i njegove karakteristike kao mogućeg interaktivnog i stabilnog nosača za RuO2 i Pt kao elektrokatalizatora u reakcijama od značaja za industrijsku elektrohemiju i alternativne izvore energije. Analizirano je i razmatrano kako u slučaju kompozita RuO2/TiO2 i Pt/TiO2, sintetizovanih na takav način da se dobijaju njihove uređene strukture, TiO2 služi kao stabilišuće i interaktivno jezgro, a RuO2, odnosno Pt, kao elektrokatalitički aktivna komponenta. Kompoziti RuO2/TiO2 i Pt/TiO2 su sintetizovani različitim hidrotermalnim metodama, koje uključuju temperaturno kontrolisan prelaz aerosolova i hidrosolova u čvrstu fazu. Kod kompozita RuO2/TiO2 se ispitivao uticaj temperature u pirolitičkom reaktoru na morfologiju dobijenog kompozita RuO2/TiO2 i stabilnost anoda koje su dobijene nanošenjem ovako dobijenog kompozita na Ti podlogu. Svojstva dobijenih kompozita analizirana su u zavisnosti od toga da li su sve faze sintetizovane u jednom koraku (in-situ) ili je faza nosača TiO2 sintetizovana prethodno (ex-situ). Strukturno-morfološka svojstva dobijenih materijala ispitivana su mikroskopskim tehnikama (SEM, TEM), analizom interakcije materijala sa elektromagnetnim zračenjem (FTIR, XRD, DLS, ramanska spektroskopija) i termogravimetrijskom analizom. Elektrohemijske karakteristike ispitivane su analizom nefaradejskog odziva i elektrokatalitičke aktivnosti i stabilnosti u reakcijama izdvajanja hlora i kiseonika (RuO2/TiO2), odnosno redukcije kiseonika i izdvajanja vodonika (Pt/TiO2). Nađeno je da se svi kompoziti dobijaju u obliku sferoidnih čestica/aglomerata, bez obzira na postupak dobijanja. Uređenost i ravnomernost strukture zavise od primenjenog postupka pripreme, kao i temperature prelaza u čvrstu fazu. Elektrohemijskim karakteristikama RuO2/TiO2 pogoduje niža temperatura pirolitičke sinteze, iako je utvrđeno da u tom slučaju izostaje potpuna konverzija prekursora rutenijuma u odgovarajući oksid. RuO2/TiO2 dobijen na nižoj temperaturi s, Properties and characteristics of titanium(IV) oxide, as posible interactive and stable support for RuO2 and Pt electrocatalysts, are studied. RuO2 and Pt are important electrocatalytic materials, often used in industrial electrochemistry and alternative power sources. It was found that in Pt/TiO2 and RuO2/TiO2 composites synthesized in a way which enables highly ordered structures TiO2 acts like a stabilising and interactive core, while Pt and RuO2 are electrocatalyticaly active components encapsulating the core. As supporting component in both Pt/TiO2 and RuO2/TiO2 composites, TiO2 synthesis and its characterisation is performed separately. RuO2/TiO2 and Pt/TiO2 composites are synthesiezed using varouis hydrothermal approches consisting of temperature-controled conversion of aerosols and hydrosols to the solid phase. In the case of RuO2/TiO2 composite, influence of synthesis temperature on the morphology of the obtained composites was studied. Influence of the synthesis temperature on the stability of activated Ti anodes coated by obtained composites was examined as well. Dependance of the properties of the obtained composites on the applied synthesis approach was investigated. In-situ approach as one-step synthesis is applied along with the ex-situ approach, which implies that at least supporting component, TiO2, has been prepared prior to the composite synthesis. Strucutral and morphological properties of the obtained materials were tested using SEM, TEM, FTIR, XRD, DLS, Raman and TGA techniques. Electrochemical characterization involved the analysis of non-Faradaic response and electrocatalytic activity and stability in chlorine and oxygen evolution reactions (RuO2/TiO2), as well as oxygen reduction and hydrogen evolution reactions (Pt/TiO2). It was found that all synthesized composites had spherical shape, independently of the synthesis method. Structure arrangement and uniformity depend on the applied approach, as well as on the synthesis temperature. Althoug

The aim of this work was to investigate corrosion resistivity, bioactivity, and antibacterial activity of novel nano-amorphous calcium phosphate (ACP) potentially multifunctional composite coatings with and without chitosan oligosaccharide lactate (ChOL), ACP + ChOL/TiO2 and ACP/TiO2 ACP + ChOL/TiO2, respectively, on the titanium substrate. The coatings were obtained by new single-step in situ anodization of the substrate to generate TiO2 and the anaphoretic electrodeposition process of ACP and ChOL. The obtained coatings were around 300 ± 15 μm thick and consisted of two phases, namely, TiO2 and hybrid composite phases. Both ACP/TiO2 and ACP + ChOL/TiO2 have improved corrosion stability, whereas the ACP + ChOL/TiO2 coating showed better corrosion stability. It was shown that at the very start of the deposition process, the formation of the ChOL/TiO2 layer takes place predominantly, which is followed by the inclusion of ChOL into ACP with simultaneous growth of TiO2. This deposition mechanism resulted in the formation of strongly bonded uniform stable coating with high corrosion resistance. In vitro bioactivity was investigated by immersion of the samples in simulated body fluid (SBF). There is in-bone-like apatite formation on both ACP/TiO2 and ACP + ChOL/TiO2 surfaces upon immersion into SBF, which was proven by X-ray diffraction and Fourier transform infrared spectroscopy. While ACP/TiO2 shows no antibacterial activity, ACP + ChOL/TiO2 samples exhibited three- to fourfold decreases in the number of Staphylococcus aureus and Pseudomonas aeruginosa, respectively, after 420 min. The probable mechanism is binding ChOL with the bacterial cell wall, inhibiting its growth, altering the permeability of the cell membrane, and leading to bacterial death.

Electrochemical measurements were employed to study the possibility of the extraction of metal ions from lateritic ore leachates predominantly rich in Fe in order to separate more noble cobalt and nickel metals. Lateritic ore was leached in 1 M H2SO4 solution at 70 °C by standard leaching process. The leachate was afterwards subjected to the pH adjustment that led to the removal of Fe ions by precipitation. Results obtained from cyclic voltammetry and chronamperometry measurements in native leachate and those with adjusted pH showed that optimal pH value for Fe removal was 3.7., Elektrohemijskim merenjima je ispitivana mogućnost izdvajanja kobalta i nikla iz lužine lateritne rude bogate sa Fe. Rastvorne komponente lateritne rude su standardnim procesom luženja, tretiranjem u 1 M rastvoru H2SO4 na povišenoj temperaturi, prevedene u rastvor. U sledećoj fazi prečišćavanja dobijenom rastvoru je podešavana pH vrednost kako bi se joni Fe preveli u talog. Cikličnom voltametrijom i hronoamperometrijom je pokazano da je optimalna vrednost za uklanjanje jona Fe 3,7.

Hydrometallurgical procedure and chemical measurements were employed to study the precipitation behavior of different metals in a lateritic ore pregnant leach solution (PLS). Lateritic ore was leached in 1 M H2SO4 solution at 70 oC by standard leaching process. The leachate was afterwards subjected to the pH adjustment that led to the removal of metal ions by precipitation. Measurements of pH as well as chemical analysis show characteristic values of metal ion removal from the PLS., Hidrometalurški postupak luženja lateritne rude uz hemijske analize u rastvoru luženja su korišćeni kako bi se ispitalo ponašanje različitih metala u koncentrovanom rastvoru luženja (PLS). Lateritna ruda podvrgnuta je standardnom postupku luženja u rastvoru 1 M H2SO4 na 70 oC. Iz dobijene lužine su nakon toga taloženi joni metala tokom menjanja pH vrednosti prvobitnog PLS rastvora. Rezultati merenja pH, kao i hemijskih analiza dali su karakteristične vrednosti na kojima je moguće iz PLS rastvora odstraniti određene jone metala.

The aim of this work was to investigate corrosion resistivity, bioactivity, and antibacterial activity of novel nano-amorphous calcium phosphate (ACP) potentially multifunctional composite coatings with and without chitosan oligosaccharide lactate (ChOL), ACP + ChOL/TiO2 and ACP/TiO2 ACP + ChOL/TiO2, respectively, on the titanium substrate. Supplementary information: The ANOVA results of antimicrobial activity on S. aureus are shown in Table S1 and the ANOVA results of antimicrobial activity on P. aeruginosa are shown in Table S2. The analysis showed significant difference at the 5% level of confidence.

Owing to a wide range of application in kinetics (photocatalysis, electrocatalysis, etc.), it is of high importance to define in details corelation between structure and synthesis of TiO2 particles. The aim is to elucidate the kinetics of TiO2 solid phase formation by sol-gel approach as newly-structured suitable carrier of batteries/fuel cells electrocatalytic materials. TiO2 nanoparticles were synthesized from TiCl3 precursor under different conditions (concentration, pH) in an aqueous medium. Formation of a new solid phase was continuously monitored by a dynamic conductometric measurements induced by high frequency impedance sinusoidal voltage perturbations of a conductometric cell. The particle size distributions of the obtained TiO2 sols were characterized by the dynamic light scattering method, while the microstructure data were obtained by the scanning electron microscopy. The typical change of high frequency impedance during TiO2 synthesis is presented in Figure 1. It was found that the process proceeds through at least five phases (I–V, Figure 1, seen as high frequency impedance decrease) of different rates and durability, which depend on synthesis conditions.

Calcium phosphates (CP), amongst which amorphous calcium phosphate (ACP) and hydroxyapatite (HAp), along with Ti and TiO2 layers, have found vast applications in preventive and regenerative medicine due to their excellent biocompatibility, nontoxic properties and ability to participate in the normal metabolism of organisms. In this paper cytotoxicity of amorphous calcium phosphate (ACP) and chitosan lactate (ChOL) multifunctional and hybrid composite coatings on MRC-5 human lung fibroblast cell line is presented. ACP/TiO2 and ACP/TiO2/ChOL are deposited by coatings new in situ anodization/anaphoretic deposition process at constant voltage of 60 V for 180 s at 25 °C. Cytotoxicity tests showed that there was no significant decrease in the survival of healthy MRC-5 cells in the Ti and ACP/TiO2 composite samples, while there was an increase in the number of viable cells in the ACP/TiO2/ChOL sample. There is improved cell proliferation, differentiation and cell viability in the later. Sample containing ACP/TiO2/ChOL coating showed negative cytotoxicity in both DET and MTT tests. Greater recovery of MRC-5 human lung fibroblasts cells was observed compared to the control sample after 48 h of recovery. From these results, it can be concluded that not only the ACP/TiO2/ChOL multifunctional composite coating is non-cytotoxic, but the presence of ChOL in the coating improves cell proliferation, differentiation and cell viability. Based on the obtained results, it can be concluded that both composite materials used in the studies are non-cytotoxic to the cell lines used, and that 5 wt.% of ChOL has a positive effect on the non-toxicity of the material. Based on presented results in this paper and previous published results of the physicochemical and bioactive properties of the ACP/TiO2/ChOL composite material, it can be concluded that further development as well as potential preclinical studies would be largely justified.