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In the present work, beta-calcium pyrophosphate (β-Ca2P2O7) was investigated as a potential adsorbent for the removal of heavy metal ions from water. Single-phase β-Ca2P2O7 powders were synthesized by a simple, scalable and cost-effective wet precipitation method followed by annealing at 800 °C, which was employed for the conversion of as-precipitated brushite (CaHPO4∙2H2O) to β-Ca2P2O7. Physicochemical properties of the sorbent were characterized by means of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA/DSC), scanning electron microscopy (SEM) and low temperature adsorption–desorption of nitrogen (BET method). The synthesized powders consisted of porous plate-like particles with micrometer dimensions. Specific surface area calculated by the BET method was found to be 7 m2 g−1. For the estimation of sorption properties, the aqueous model solutions containing different metal ions (Al3+, Cd2+, Co2+, Cu2+, Fe2+, Mn2+, Ni2+, Pb2+, Sn2+, Sr2+ and Zn2+) were used. The adsorption test revealed that β-Ca2P2O7 demonstrates the highest adsorption capacity for Pb2+ and Sn2+ ions, while the lowest capacity was observed towards Sr2+, Ni2+ and Co2+ ions. The optimal pH value for the removal of Pb2+ ions was determined to be 2, which is also related to the low solubility of β-Ca2P2O7 at this pH. The adsorption capacity towards Pb2+ ions was calculated as high as 120 mg g−1.
Diana Griesiute; Justina Gaidukevic; Aleksej Zarkov; Aivaras Kareiva. Synthesis of β-Ca2P2O7 as an Adsorbent for the Removal of Heavy Metals from Water. Sustainability 2021, 13, 7859 .
AMA StyleDiana Griesiute, Justina Gaidukevic, Aleksej Zarkov, Aivaras Kareiva. Synthesis of β-Ca2P2O7 as an Adsorbent for the Removal of Heavy Metals from Water. Sustainability. 2021; 13 (14):7859.
Chicago/Turabian StyleDiana Griesiute; Justina Gaidukevic; Aleksej Zarkov; Aivaras Kareiva. 2021. "Synthesis of β-Ca2P2O7 as an Adsorbent for the Removal of Heavy Metals from Water." Sustainability 13, no. 14: 7859.
This work focused on the kinetic analysis of the thermal reduction reaction of graphene oxide (GO) both with and without carbon suboxide (C3O2) by using Borchardt-Daniels, Kissinger, and Ozawa models. The effect of C3O2 on the thermal decomposition of GO was investigated by thermogravimetry (TG), derivative thermogravimetry (DTG), and differential scanning colorimetry (DSC) analysis. It was noticed that C3O2 tends to increase the chemical reactivity of GO due to the decreasing of the reaction activation energy Ea. The apparent reaction order is determined to be 0.7 for the thermal decomposition of both studied samples. This value evidences the complex mechanism of the thermal decomposition of GO that includes consecutive zero-order and first-order processes. Finally, by comparing the enthalpy values of GO thermal decomposition, it was determined that GO sample with the additive of C3O2 releases a lower amount of energy comparing to that of pure GO during the thermal reduction.
Ruta Aukstakojyte; Justina Gaidukevic; Jurgis Barkauskas. Thermal Reduction of Graphene Oxide in the Presence of Carbon Suboxide. Journal of Solid State Chemistry 2021, 301, 122365 .
AMA StyleRuta Aukstakojyte, Justina Gaidukevic, Jurgis Barkauskas. Thermal Reduction of Graphene Oxide in the Presence of Carbon Suboxide. Journal of Solid State Chemistry. 2021; 301 ():122365.
Chicago/Turabian StyleRuta Aukstakojyte; Justina Gaidukevic; Jurgis Barkauskas. 2021. "Thermal Reduction of Graphene Oxide in the Presence of Carbon Suboxide." Journal of Solid State Chemistry 301, no. : 122365.
A series of N-doped graphene-based materials was prepared from thermally reduced graphene oxide (TRGO) at elevated temperature (850 or 950 °C) under ammonia flow, and by impregnation of TRGO with melamine followed by subsequent thermal treatment. The performed analyses revealed efficient doping of TRGO with N functionalities of different types, the content of which was found to be between 3.4 wt% and 12.3 wt%, depending on the modification route and conditions. The functionalization of TRGO with NH3 was considerably less effective than that with melamine, however, the NH3-treated carbons were significantly more basic in nature (basicity up to 0.77 mmol g−1) due to the presence of quaternary N (NQ). It was also found that NQ was preferentially formed under more severe conditions, i.e., higher temperature and longer reaction time. The catalytic performance of the prepared samples was investigated in the transesterification of rapeseed oil with methanol under elevated pressure at 130 °C. The activity of carbons was strongly related to the content of NQ, and the highest yield of fatty acid methyl esters (of 65%) was obtained in the process performed with TRGO functionalized with ammonia at 950 °C for 8 h, which showed the highest number of quaternary nitrogen.
Justina Gaidukevič; Jurgis Barkauskas; Anna Malaika; Vitalija Jasulaitienė; Mieczysław Kozłowski. Preparation and characterization of basic graphene-based catalysts and their application in biodiesel synthesis. Applied Surface Science 2021, 554, 149588 .
AMA StyleJustina Gaidukevič, Jurgis Barkauskas, Anna Malaika, Vitalija Jasulaitienė, Mieczysław Kozłowski. Preparation and characterization of basic graphene-based catalysts and their application in biodiesel synthesis. Applied Surface Science. 2021; 554 ():149588.
Chicago/Turabian StyleJustina Gaidukevič; Jurgis Barkauskas; Anna Malaika; Vitalija Jasulaitienė; Mieczysław Kozłowski. 2021. "Preparation and characterization of basic graphene-based catalysts and their application in biodiesel synthesis." Applied Surface Science 554, no. : 149588.
The control of glucose concentration is a crucial factor in clinical diagnosis and the food industry. Electrochemical biosensors based on reduced graphene oxide (rGO) and conducting polymers have a high potential for practical application. A novel thermal reduction protocol of graphene oxide (GO) in the presence of malonic acid was applied for the synthesis of rGO. The rGO was characterized by scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and Raman spectroscopy. rGO in combination with polyaniline (PANI), Nafion, and glucose oxidase (GOx) was used to develop an amperometric glucose biosensor. A graphite rod (GR) electrode premodified with a dispersion of PANI nanostructures and rGO, Nafion, and GOx was proposed as the working electrode of the biosensor. The optimal ratio of PANI and rGO in the dispersion used as a matrix for GOx immobilization was equal to 1:10. The developed glucose biosensor was characterized by a wide linear range (from 0.5 to 50 mM), low limit of detection (0.089 mM), good selectivity, reproducibility, and stability. Therefore, the developed biosensor is suitable for glucose determination in human serum. The PANI nanostructure and rGO dispersion is a promising material for the construction of electrochemical glucose biosensors.
Anton Popov; Ruta Aukstakojyte; Justina Gaidukevic; Viktorija Lisyte; Asta Kausaite-Minkstimiene; Jurgis Barkauskas; Almira Ramanaviciene. Reduced Graphene Oxide and Polyaniline Nanofibers Nanocomposite for the Development of an Amperometric Glucose Biosensor. Sensors 2021, 21, 948 .
AMA StyleAnton Popov, Ruta Aukstakojyte, Justina Gaidukevic, Viktorija Lisyte, Asta Kausaite-Minkstimiene, Jurgis Barkauskas, Almira Ramanaviciene. Reduced Graphene Oxide and Polyaniline Nanofibers Nanocomposite for the Development of an Amperometric Glucose Biosensor. Sensors. 2021; 21 (3):948.
Chicago/Turabian StyleAnton Popov; Ruta Aukstakojyte; Justina Gaidukevic; Viktorija Lisyte; Asta Kausaite-Minkstimiene; Jurgis Barkauskas; Almira Ramanaviciene. 2021. "Reduced Graphene Oxide and Polyaniline Nanofibers Nanocomposite for the Development of an Amperometric Glucose Biosensor." Sensors 21, no. 3: 948.
Thermal reduction of graphite oxide (GO) is considered as a prospective method for the preparation of high-performance graphene-based materials. However, this method has certain limitations, and the major is that this exothermic process is difficult to control. In this research, we focused on the kinetic studies of the reduction of graphite oxide using non-isothermal differential calorimetry (DSC) method. Six GO nanocomposites with dyes were tested to study the shift in kinetic parameters. The apparent reaction order is determined to be ca 0.7 for the thermal decomposition of pure GO, while in the presence of dye molecules it increases sometimes reaching a value of 2.0 for higher dye concentrations. Decisively, the thermal decomposition of pure GO can be presented as an intermediate between a zero- and first-order reaction, while the introduction of dye molecules turns a certain part of the energy consumption via the bimolecular pathway. Our research revealed that the process of GO thermal decomposition can be operated and properties of the final product (reduced graphene oxide (rGO) and its derivatives) can be adjusted more precisely using additive molecules, which interact with GO sheets.
Jurgis Barkauskas; Justina Gaidukevič; Gediminas Niaura. Thermal reduction of graphite oxide in the presence of nitrogen-containing dyes. Carbon Letters 2021, 1 -14.
AMA StyleJurgis Barkauskas, Justina Gaidukevič, Gediminas Niaura. Thermal reduction of graphite oxide in the presence of nitrogen-containing dyes. Carbon Letters. 2021; ():1-14.
Chicago/Turabian StyleJurgis Barkauskas; Justina Gaidukevič; Gediminas Niaura. 2021. "Thermal reduction of graphite oxide in the presence of nitrogen-containing dyes." Carbon Letters , no. : 1-14.
The melt of H₃BO₃ was used to reach a controllable reduced graphene oxide (rGO) synthesis protocol using a graphene oxide (GO) precursor. Thermogravimetric analysis and differential scanning calorimetry (TG/DSC) investigation and scanning electron microscopy (SEM) images have shown that different from GO powder, reduction of GO in the melt of H₃BO₃ leads to the formation of less disordered structure of basal graphene planes. Threefold coordinated boron atom acts as a scavenger of oxygen atoms during the process of GO reduction. Fourier-transform infrared (FTIR) spectra of synthesized products have shown that the complex of glycerol and H₃BO₃ acts as a regioselective catalyst in epoxide ring-opening reaction and suppress the formation of ketone C=O functional groups at vacancy sites. Thermal treatment at 800 °C leads to the increased concentration of point defects in the backbone structure of rGO. Synthesized materials were tested electrochemically. The electrochemical performance of these materials essentially differs depending on the preparation protocol. The highest charge/discharge rate and double-layer capacitance were found for a sample synthesized in the melt of H₃BO₃ in the presence of glycerol and treated at 800 °C. The effect of optimal porosity and high electrical conductivity on the electrochemical performance of prepared materials also were studied.
Justina Gaidukevič; Rasa PauliukaitĖ; Gediminas Niaura; Ieva Matulaitienė; Olga Opuchovič; Aneta Radzevič; Gvidas Astromskas; Virginijus Bukauskas; Jurgis Barkauskas. Synthesis of Reduced Graphene Oxide with Adjustable Microstructure Using Regioselective Reduction in the Melt of Boric Acid: Relationship Between Structural Properties and Electrochemical Performance. Nanomaterials 2018, 8, 889 .
AMA StyleJustina Gaidukevič, Rasa PauliukaitĖ, Gediminas Niaura, Ieva Matulaitienė, Olga Opuchovič, Aneta Radzevič, Gvidas Astromskas, Virginijus Bukauskas, Jurgis Barkauskas. Synthesis of Reduced Graphene Oxide with Adjustable Microstructure Using Regioselective Reduction in the Melt of Boric Acid: Relationship Between Structural Properties and Electrochemical Performance. Nanomaterials. 2018; 8 (11):889.
Chicago/Turabian StyleJustina Gaidukevič; Rasa PauliukaitĖ; Gediminas Niaura; Ieva Matulaitienė; Olga Opuchovič; Aneta Radzevič; Gvidas Astromskas; Virginijus Bukauskas; Jurgis Barkauskas. 2018. "Synthesis of Reduced Graphene Oxide with Adjustable Microstructure Using Regioselective Reduction in the Melt of Boric Acid: Relationship Between Structural Properties and Electrochemical Performance." Nanomaterials 8, no. 11: 889.
Production of biodiesel by the transesterification process using different modified graphene-based materials as catalysts was studied. Solid acid graphene-based samples were prepared by grafting sulfonic or phosphate groups on the surface of thermally reduced graphene oxide. The obtained materials were thoroughly characterized using scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, N2 adsorption-desorption measurements, potentiometric titration, elemental analysis, and Fourier transform infrared spectroscopy. The prepared catalysts were tested in the transesterification of rapeseed oil with methanol at 130 °C under pressure, and their activities were compared to the performance of a commercially available heterogeneous acidic catalyst, Amberlyst-15. All modified samples were active in the transesterification process; however, significant differences were observed in the yield of biodiesel, depending on the method of catalyst preparation and strength of the acidic sites. The highest yield of fatty acid methyl esters of 70% was obtained for thermally reduced graphene oxide functionalized with 4-benzenediazonium sulfonate after 6 h of processing, and this result was much higher than that obtained for the commercial catalyst Amberlyst-15. The results of the reusability test were also promising.
Justina Gaidukevič; Jurgis Barkauskas; Anna Malaika; Paulina Rechnia-Gorący; Aleksandra Możdżyńska; Vitalija Jasulaitienė; Mieczysław Kozłowski. Modified graphene-based materials as effective catalysts for transesterification of rapeseed oil to biodiesel fuel. Chinese Journal of Catalysis 2018, 39, 1633 -1645.
AMA StyleJustina Gaidukevič, Jurgis Barkauskas, Anna Malaika, Paulina Rechnia-Gorący, Aleksandra Możdżyńska, Vitalija Jasulaitienė, Mieczysław Kozłowski. Modified graphene-based materials as effective catalysts for transesterification of rapeseed oil to biodiesel fuel. Chinese Journal of Catalysis. 2018; 39 (10):1633-1645.
Chicago/Turabian StyleJustina Gaidukevič; Jurgis Barkauskas; Anna Malaika; Paulina Rechnia-Gorący; Aleksandra Możdżyńska; Vitalija Jasulaitienė; Mieczysław Kozłowski. 2018. "Modified graphene-based materials as effective catalysts for transesterification of rapeseed oil to biodiesel fuel." Chinese Journal of Catalysis 39, no. 10: 1633-1645.
Justina Gaidukevič; Julija Razumienė; Ieva Šakinytė; Susana L.H. Rebelo; Jurgis Barkauskas. Study on the structure and electrocatalytic activity of graphene-based nanocomposite materials containing (SCN)n. Carbon 2017, 118, 156 -167.
AMA StyleJustina Gaidukevič, Julija Razumienė, Ieva Šakinytė, Susana L.H. Rebelo, Jurgis Barkauskas. Study on the structure and electrocatalytic activity of graphene-based nanocomposite materials containing (SCN)n. Carbon. 2017; 118 ():156-167.
Chicago/Turabian StyleJustina Gaidukevič; Julija Razumienė; Ieva Šakinytė; Susana L.H. Rebelo; Jurgis Barkauskas. 2017. "Study on the structure and electrocatalytic activity of graphene-based nanocomposite materials containing (SCN)n." Carbon 118, no. : 156-167.
Aiming to create reagentless amperometric D-fructose biosensor, graphene based electrode materials have been synthesized by newly proposed thermal reduction of graphene oxide. The method allowed to separate and collect different fractions of thermally reduced graphene oxide (TRGO) with different physicochemical properties. The structural characteristics and surface morphologies of TRGO fractions were evaluated using SEM, XRD, TGA analysis, Raman spectroscopy and BET measurements. Three different fractions of TRGO were tested as electrode materials for D-fructose amperometric biosensors. The direct electron transfer (DET) from the active site of D-fructose dehydrogenase (FDH) to the electrode was achieved with all TRGO fractions. High values of the sensitivity (up to 14.5 μA mM(-1) cm(-2)) are of the same order as these for other D-fructose sensors based on the synergistic mediated processes. The relationships between the structure of TRGO fractions and the molecular processes determining the effect of DET in bioelectrocatalysis by FDH have been studied. Stability of the D-fructose biosensors was also assessed. The best results were achieved when immobilization of FDH was performed using a crosslinking with glutaraldehyde. For the best group, after a period of 5 days the sensitivity of the biosensor for D-fructose determination decreased by less than 20%.
Ieva Šakinytė; Jurgis Barkauskas; Justina Gaidukevič; Julija Razumienė. Thermally reduced graphene oxide: The study and use for reagentless amperometric d-fructose biosensors. Talanta 2015, 144, 1096 -1103.
AMA StyleIeva Šakinytė, Jurgis Barkauskas, Justina Gaidukevič, Julija Razumienė. Thermally reduced graphene oxide: The study and use for reagentless amperometric d-fructose biosensors. Talanta. 2015; 144 ():1096-1103.
Chicago/Turabian StyleIeva Šakinytė; Jurgis Barkauskas; Justina Gaidukevič; Julija Razumienė. 2015. "Thermally reduced graphene oxide: The study and use for reagentless amperometric d-fructose biosensors." Talanta 144, no. : 1096-1103.