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Menya, E., Olupot, P. W., Storz, H., Lubwama, M., Kiros, Y. & John, M. J. (2019). Effect of alkaline pretreatment on the thermal behavior and chemical properties of rice husk varieties in relation to activated carbon production. Journal of thermal analysis and calorimetry (Print)
Open this publication in new window or tab >>Effect of alkaline pretreatment on the thermal behavior and chemical properties of rice husk varieties in relation to activated carbon production
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2019 (English)In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926Article in journal (Refereed) Published
Abstract [en]

Thermal behavior and chemical properties of selected raw and NaOH-pretreated rice husk varieties were investigated. NaOH-pretreatment process involved soaking 5 g rice husk samples in 40 mL of 2%w/v NaOH, shaking (400 rpm) and heating (50 °C) for 3 h. NaOH-pretreated samples were water-washed, oven-dried, and milled for use in the determination of their thermal behavior and surface functional groups. Alkaline wash-water was also analyzed for sugar components. Thermal decomposition temperatures, degradation rates, and the subsequent mass losses varied from one rice husk variety to another. These thermal properties increased after NaOH-pretreatment of the rice husk varieties, reducing their char yields (17.1–20.4% db). These changes mainly had to do with the lignin, hemicellulose, and ash removal from the rice husk varieties, as confirmed by their FTIR analysis, as well as by the sugar composition analysis of their alkaline wash-water. Consequently, the FTIR spectra differed between the raw and NaOH-pretreated rice husk varieties.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
NaOH-pretreatment, Rice husk varieties, Sugar composition, Surface functional groups, Thermal behavior, Activated carbon, Alkalinity, Decomposition, Degradation, Fourier transform infrared spectroscopy, NaOH pretreatment, Rice husk, Thermal behaviors, Sodium hydroxide
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-263275 (URN)10.1007/s10973-019-08553-6 (DOI)2-s2.0-85069521253 (Scopus ID)
Note

QC 20191105

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-05Bibliographically approved
Paulraj, A. R., Kiros, Y., Chamoun, M., Svengren, H., Noréus, D., Göthelid, M., . . . Johansson, M. B. (2019). Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes. Batteries (1)
Open this publication in new window or tab >>Electrochemical Performance and in Operando Charge Efficiency Measurements of Cu/Sn-Doped Nano Iron Electrodes
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2019 (English)In: Batteries, E-ISSN 2313-0105, no 1Article in journal (Other academic) Published
Abstract [en]

Fe-air or Ni-Fe cells can offer low-cost and large-scale sustainable energy storage. At present, they are limited by low coulombic efficiency, low active material use, and poor rate capability. To overcome these challenges, two types of nanostructured doped iron materials were investigated: (1) copper and tin doped iron (CuSn); and (2) tin doped iron (Sn). Single-wall carbon nanotube (SWCNT) was added to the electrode and LiOH to the electrolyte. In the 2 wt. % Cu + 2 wt. % Sn sample, the addition of SWCNT increased the discharge capacity from 430 to 475 mAh g−1, and charge efficiency increased from 83% to 93.5%. With the addition of both SWCNT and LiOH, the charge efficiency and discharge capacity improved to 91% and 603 mAh g−1, respectively. Meanwhile, the 4 wt. % Sn substituted sample performance is not on par with the 2 wt. % Cu + 2 wt. % Sn sample. The dopant elements (Cu and Sn) and additives (SWCNT and LiOH) have a major impact on the electrode performance. To understand the relation between hydrogen evolution and charge current density, we have used in operando charging measurements combined with mass spectrometry to quantify the evolved hydrogen. The electrodes that were subjected to prolonged overcharge upon hydrogen evolution failed rapidly. This insight could help in the development of better charging schemes for the iron electrodes.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Iron electrodes, Cu and Sn-doped iron, SWCNT and LiOH additives, charge efficiency, hydrogen evolution, GC-MS analysis
National Category
Chemical Process Engineering
Research subject
Chemistry; Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-241278 (URN)10.3390/batteries5010001 (DOI)000464125800001 ()2-s2.0-85068355323 (Scopus ID)
Note

QC 20190121

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-10-04Bibliographically approved
Solis, J. L., Davila, R., Sandoval, C., Guzmán, D., Guzmán, H., Alejo, L. & Kiros, Y. (2019). Ethanol Production from Schinus molle Essential Oil Extraction Residues. Waste and Biomass Valorization
Open this publication in new window or tab >>Ethanol Production from Schinus molle Essential Oil Extraction Residues
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2019 (English)In: Waste and Biomass Valorization, ISSN 1877-2641, E-ISSN 1877-265XArticle in journal (Refereed) Published
Abstract [en]

Abstract: The present study determines the best conditions for the fermentation of Schinus molle drupes by the combination of different types of hydrolysis with the search for an adequate yeast strain. Schinus molle seed residues from an essential oil extraction plant (EOEP) have a high potential for ethanol production. Native yeast strains were isolated from the residues and were used to ferment the lignocellulosic residues, along with baker’s yeast (Saccharomyces cerevisiae) at 30 °C and pH 5.5 for comparison. Morphological and biochemical characterizations were carried out on the isolated yeast strains. Thermogravimetric and high-performance liquid chromatography analyses were done on the S. molle seeds (fresh and residue) to determine the ethanol production potential. The followed methodology included increasing the sugar content by hydrolysis with chemical (sulphuric acid, acetic acid, and sodium hydroxide), physical (thermal, vacuum, and ultrasound), and enzymatic treatments (amyloglucosidase and α-amylase). Once the optimum combination of yeast-hydrolysis was determined, a comparison of the greenhouse gas emissions between the original and proposed processes was done. The fermentation of the residues might replace methane from uncontrolled decomposition and reduce the solid residues in 50%/day, hence the EOEP global warming potential is reduced by 47%. The yearly income was estimated to increase by USD 2592.50 from 6302.6 L of ethanol produced from the residues.

Place, publisher, year, edition, pages
Springer Netherlands, 2019
Keywords
Essential oil extraction, Ethanol, Native yeast, Schinus molle, Waste treatment, Essential oils, Extraction, Fermentation, Gas emissions, Global warming, Greenhouse gases, High performance liquid chromatography, Hydrolysis, Seed, Sodium hydroxide, Biochemical characterization, Enzymatic treatments, Ethanol production, Global warming potential, Lignocellulosic residues, Oil extraction, Optimum combination, Yeast
National Category
Bioenergy
Identifiers
urn:nbn:se:kth:diva-263283 (URN)10.1007/s12649-019-00737-3 (DOI)2-s2.0-85068322618 (Scopus ID)
Note

QC 20191105

Available from: 2019-11-05 Created: 2019-11-05 Last updated: 2019-11-05Bibliographically approved
Soroka, I., Bjervås, J., Ceder, J., Wallnerström, G., Connan, M., Tarakina, N. V., . . . Kiros, Y. (2019). Particle size effect of Ag-nanocatalysts deposited on carbon as prepared by γ-radiation induced synthesis. Radiation Physics and Chemistry, Article ID 108370.
Open this publication in new window or tab >>Particle size effect of Ag-nanocatalysts deposited on carbon as prepared by γ-radiation induced synthesis
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2019 (English)In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, article id 108370Article in journal (Refereed) Published
Abstract [en]

The effect of silver particle sizes on the catalytic performance of Ag/C electrodes for oxygen reduction reaction (ORR) was studied. The Ag particles were precipitated from AgNO3 solutions on Vulcan XC-72 carbon as support by γ-radiation induced synthesis method. The structural and morphological characterizations of the electrode materials were done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that particles with smaller diameters, 11 ± 6 nm, possess higher catalytic activity for ORR (50 mA/cm2 at 0.3 V) as compared to those with larger diameters, 41 ± 5 nm, ORR activity is 25 mA/cm2 at 0.3 V. The observed effect may be explained by an increased amount of low coordinated atoms in smaller particles as compared to the larger ones.

Place, publisher, year, edition, pages
Elsevier Ltd, 2019
Keywords
Carbon, Catalyst activity, Electrodes, Electrolytic reduction, Gamma rays, High resolution transmission electron microscopy, Nanocatalysts, Silver compounds, Catalytic performance, Effect of silvers, Electrode material, Morphological characterization, Orr activities, Oxygen reduction reaction, Particle size effect, Radiation-induced synthesis, Particle size
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-261243 (URN)10.1016/j.radphyschem.2019.108370 (DOI)2-s2.0-85068784720 (Scopus ID)
Note

QC 20191003

QC 20191015

Available from: 2019-10-03 Created: 2019-10-03 Last updated: 2019-11-05Bibliographically approved
Menya, E., Olupot, P. W., Storz, H., Lubwama, M. & Kiros, Y. (2018). Characterization and alkaline pretreatment of rice husk varieties in Uganda for potential utilization as precursors in the production of activated carbon and other value-added products. Waste Management, 81, 104-116
Open this publication in new window or tab >>Characterization and alkaline pretreatment of rice husk varieties in Uganda for potential utilization as precursors in the production of activated carbon and other value-added products
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2018 (English)In: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 81, p. 104-116Article in journal (Refereed) Published
Abstract [en]

In this study, 13 rice husk (RH) varieties from 4 agro-ecological zones in Uganda were characterized, NaOH-pretreated, and evaluated for their potential utilization as precursors for production of bio-oil, ash, char, and activated carbon for selected applications. RH varieties were characterized through particle size analysis, bulk density, proximate and ultimate analyses, specific surface area, pore volume, as well as lignocellulosic and inorganic compositions. Selected RH varieties were subsequently pretreated at NaOH concentrations of 1-4%w/v, using pretreatment ratios of 5 g RH: 40 mL NaOH. Properties varied among RH varieties, suiting them as feedstocks for different applications. Upland rice husk varieties are more suited precursors for production of bio-oil, and activated carbon due to their relatively lower ash content, higher specific surface area, as well as higher volatile matter and fixed carbon contents. Upland rice husks could as well be employed in the preparation of electrodes for electrochemical devices, due to their relatively higher specific surface area. A high ash content (21-32% dry basis) of lowland rice husks presents good prospects for their calcination, since larger amounts of rice husk ash could be obtained, and employed in different applications. Lowland rice husk varieties could also be more suited precursors for production of char for soil amendment, due to their relatively higher ash content, which subsequently increases their char yields. However, alkaline pretreatment of rice husks using 2-4%w/v NaOH can reduce the ash content by as much as 74-93%, depending on the rice husk variety, which paves way for utilizing rice husks with a high ash content in different applications. Aside from ash reduction, the enhanced specific surface area (1.2-1.7 m(2) g(-1)), volatile matter (68-79%db) and fixed carbon (19-24%db) contents of NaOH-pretreated rice husks suggests they are more suited feedstocks than when employed in their raw form, for production of bio-oil, as well as activated carbon.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Rice husk varieties, Characterization, Alkaline pretreatment, Activated carbon, Uganda
National Category
Bioenergy
Identifiers
urn:nbn:se:kth:diva-241342 (URN)10.1016/j.wasman.2018.09.050 (DOI)000455061800012 ()30527026 (PubMedID)2-s2.0-85054336541 (Scopus ID)
Note

QC 20190121

Available from: 2019-01-21 Created: 2019-01-21 Last updated: 2019-04-08Bibliographically approved
Paulraj, A. R. & Kiros, Y. (2018). La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte. Journal of Solid State Electrochemistry, 1-14
Open this publication in new window or tab >>La0.1Ca0.9MnO3/Co3O4 for oxygen reduction and evolution reactions (ORER) in alkaline electrolyte
2018 (English)In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, p. 1-14Article in journal, Editorial material (Refereed) Published
Abstract [en]

Non-precious metal bifunctional catalysts are of great interest for metal–air batteries, electrolysis, and regenerative fuel cell systems due to their performance and cost benefits compared to the Pt group metals (PGM). In this work, metal oxides of La0.1Ca0.9MnO3 and nano Co3O47 catalyst as bifunctional catalysts were used in oxygen reduction and evolution reactions (ORER). The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption isotherms. The electrocatalytic activity of the perovskite-type La0.1Ca0.9MnO3 and Co3O4 catalysts both as single and mixtures of both were assessed in alkaline solutions at room temperature. Electrocatalyst activity, stability, and electrode kinetics were studied using cyclic voltammetry (CV) and rotating disk electrode (RDE). This study shows that the bifunctional performance of the mixed La0.1Ca0.9MnO3 and nano Co3O4 was superior in comparison to either La0.1Ca0.9MnO3 or nano Co3O4 alone for ORER. The improved activity is due to the synergistic effect between the La0.1Ca0.9MnO3 and nano Co3O4 structural and surface properties. This work illustrates that hybridization between these two metal oxides results in the excellent bifunctional oxygen redox activity, stability, and cyclability, leading to a cost-effective application in energy conversion and storage, albeit to the cost of higher catalyst loadings.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2018
National Category
Chemical Engineering
Research subject
Chemical Engineering; Chemistry
Identifiers
urn:nbn:se:kth:diva-222516 (URN)10.1007/s10008-017-3862-2 (DOI)000431668000007 ()2-s2.0-85040363046 (Scopus ID)
Funder
Swedish Energy Agency, 39078-01
Note

QC 20180212

Available from: 2018-02-12 Created: 2018-02-12 Last updated: 2019-01-24Bibliographically approved
Paulraj, A. R., Kiros, Y., Göthelid, M. & Johansson, M. B. (2018). NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media. catalyst, 8(8)
Open this publication in new window or tab >>NiFeOx as a Bifunctional Electrocatalyst for Oxygen Reduction (OR) and Evolution (OE) Reaction in Alkaline Media
2018 (English)In: catalyst, Vol. 8, no 8Article in journal (Refereed) Published
Abstract [en]

This article reports the two-step synthesis of NiFeOx nanomaterials and their characterization and bifunctional electrocatalytic activity measurements in alkaline electrolyte for metal-air batteries. The samples were mostly in layered double hydroxide at the initial temperature, but upon heat treatment, they were converted to NiFe2O4 phases. The electrochemical behaviour of the different samples was studied by linear sweep voltammetry and cyclic voltammetry on the glassy carbon electrode. The OER catalyst activity was observed for low mass loadings (0.125 mg cm−2), whereas high catalyst loading exhibited the best performance on the ORR side. The sample heat-treated at 250 °C delivered the highest bi-functional oxygen evolution and reduction reaction activity (OER/ORR) thanks to its thin-holey nanosheet-like structure with higher nickel oxidation state at 250 °C. This work further helps to develop low-cost electrocatalyst development for metal-air batteries

National Category
Other Chemical Engineering Chemical Process Engineering
Research subject
Chemical Engineering; Chemistry
Identifiers
urn:nbn:se:kth:diva-241281 (URN)10.3390/catal8080328 (DOI)000442517100033 ()2-s2.0-85052506473 (Scopus ID)
Funder
Swedish Energy Agency, 39078-01
Note

QC 20190124

Available from: 2019-01-17 Created: 2019-01-17 Last updated: 2019-08-20Bibliographically approved
Menya, E., Olupot, P. W., Storz, H., Lubwama, M. & Kiros, Y. (2018). Production and performance of activated carbon from rice husks for removal of natural organic matter from water: A review. Chemical engineering research & design, 129, 271-296
Open this publication in new window or tab >>Production and performance of activated carbon from rice husks for removal of natural organic matter from water: A review
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2018 (English)In: Chemical engineering research & design, ISSN 0263-8762, E-ISSN 1744-3563, Vol. 129, p. 271-296Article, review/survey (Refereed) Published
Abstract [en]

Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. To address these limitations, research efforts have been focused on finding low cost materials that can be transformed into activated carbon. Rice husk is one of such materials of research focus, especially in the developing countries, where over 96% of rice husks are generated globally. Although numerous investigations have been made concerning the production of activated carbon from rice husks, the existing scientific information still remains widely scattered in literature. Furthermore, the scientific information regarding performance of rice husk activated carbon during NOM removal from water still remains poorly documented. This review article therefore provides ample information on efforts made by various researchers concerning production of activated carbon from rice husks and its adsorption performance in relation to NOM removal from water. Properties and pretreatment of rice husks in relation to production of activated carbon are discussed. Activation of rice husks by physical and chemical methods under numerous conditions is reviewed. Factors affecting NOM adsorption by activated carbon are briefly discussed. Adsorption performance of rice husk activated carbon is also reviewed with respect to NOM removal from water, and where possible compared with other source derived activated carbons. The data from literature revealed that NOM removal by rice husk activated carbon can be as effective as commercial activated carbon. Consequently, rice husk activated carbon has potential to serve as an alternative to commercial activated carbon.

Place, publisher, year, edition, pages
Institution of Chemical Engineers, 2018
Keywords
Activated carbon, Activation, Natural organic matter, Rice husk, Water
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-219638 (URN)10.1016/j.cherd.2017.11.008 (DOI)000424855100024 ()2-s2.0-85035358676 (Scopus ID)
Note

QC 20171211

Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-03-05Bibliographically approved
Soroka, I., Tarakina, N. V., Hermansson, A., Bigum, L., Widerberg, R., Andersson, M. S., . . . Kiros, Y. (2017). Radiation-induced synthesis of nanoscale Co- and Ni-based electro-catalysts on carbon for the oxygen reduction reaction. Dalton Transactions, 46(30), 9995-10002
Open this publication in new window or tab >>Radiation-induced synthesis of nanoscale Co- and Ni-based electro-catalysts on carbon for the oxygen reduction reaction
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2017 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 46, no 30, p. 9995-10002Article in journal (Refereed) Published
Abstract [en]

A facile synthesis of 3d-metal based electro-catalysts directly incorporated into a carbon support was carried out by.-radiation. Transition metals of period 4, i.e. Ni and Co, were precipitated and reduced from their respective salt solutions. The obtained materials were characterized by XRD, SEM, SQUID and the BET methods. Thereafter, the electrodes for fuel cells were fabricated out of synthesized material and their electrochemical performance for the oxygen reduction reaction in 6 M KOH was measured. Although the concentrations of Co and Ni in the electrode material were low (3.4% Co and 0.4% Ni) after reduction by irradiation, both the Ni and Co-based gas diffusion electrodes showed high catalytic activity for oxygen reduction both at room temperature and at 60 degrees C.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:kth:diva-214894 (URN)10.1039/c7dt01162h (DOI)000408695300030 ()28726886 (PubMedID)2-s2.0-85026821480 (Scopus ID)
Note

QC 20171023

Available from: 2017-10-23 Created: 2017-10-23 Last updated: 2018-02-26Bibliographically approved
Jukka-Pekka, S., Petri, K., Tanja, K., Jorma, S., Kiros, Y., Kari, S. & Martti, L. (2017). Towards an Efficient Direct Glucose Anion Exchange Membrane Fuel Cell System with Several Electro-Oxidation Units. International Journal of Electrochemical Science, 12(5), 3697-3708
Open this publication in new window or tab >>Towards an Efficient Direct Glucose Anion Exchange Membrane Fuel Cell System with Several Electro-Oxidation Units
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2017 (English)In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 12, no 5, p. 3697-3708Article in journal (Refereed) Published
Abstract [en]

This work covers the direct glucose anion exchange membrane fuel cell (AEMFC) with near-neutralstate electrolyte of 0.1 M [PO4] (tot) having two high-performing anode electrocatalysts (Pt and PtNi) at 37 degrees C and at a glucose concentration of 0.1 M. The cathode catalyst in each test was a Pt supported on carbon (60 wt.%). The PtNi/C had a total metal content of 40 wt.% and the Pt/C 60 wt.%. The operation of the AEMFC was controlled by means of an in-house made electronic load with PI-controller (i.e. a feedback controller, which has proportional and integral action on control error signal). There were two primary objectives with this study. At first, to find out how the electrode modifications of the anode (i.e. by increasing the thicknesses of these electrodes by adding extra carbon) affect the Coulombic efficiency (CE, based on the exchange of two electrons) and the specific energy (SPE, Wh kg(-1)) values of the direct glucose AEMFC. Secondly, investigate how a two-stage fuel cell system with two fuel cells concatenated and used one after the other for the electrochemical oxidation of glucose, influence the CE and SPE values. The results show that the modified PtNi anode shows superior results for the AEMFC compared to our earlier results. As for the two-stage fuel cell system, it increased the average electric power (mWh) and SPE when compared to single fuel cell systems except when the higher selective anode catalyst (Pt) was used in the first fuel cell prior to the fuel cell in the second fuel cell containing the lower selective anode catalyst (PtNi).

Place, publisher, year, edition, pages
ESG, 2017
Keywords
glucose, anode electrocatalysts, anion exchange membrane fuel cell, near-neutral-state electrolyte, multistage fuel cell system
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-210503 (URN)10.20964/2017.05.41 (DOI)000402485100012 ()2-s2.0-85019646346 (Scopus ID)
Note

QC 20170704

Available from: 2017-07-04 Created: 2017-07-04 Last updated: 2017-11-29Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-6212-4194

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