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Publications (10 of 43) Show all publications
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
Tehrani, N. F., Aznar, J. S. & Kiros, Y. (2015). Coffee extract residue for production of ethanol and activated carbons. Journal of Cleaner Production, 91, 64-70
Open this publication in new window or tab >>Coffee extract residue for production of ethanol and activated carbons
2015 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 91, p. 64-70Article in journal (Refereed) Published
Abstract [en]

Biomass as a waste product in the form coffee extract residue (CER) has been shown to have potential for the dual purpose of ethanol production and preparation of activated carbons. A straightforward method of direct hydrolysis and fermentation (DHF) is considered as the main option utilized in this study for the generation of fuel ethanol from the biomass waste. Factors such as loadings of saccharomyces cerevisiae, temperatures (21 and 30 degrees C) and substrate content were investigated to maximize the yield of ethanol. Ethanol production rates between 1.1 g and 0.70 g h(-1) kg(-1) without pretreatment and 2.7 and 23 g h(-1) kg(-1) dry substance with mild treatment were obtained, respectively. The CER was also used to prepare activated carbons using both chemical and physical activation methods. The effects of process parameters such as temperatures and concentrations of acid were varied and determined as to the yield, BET-surface areas and porosities of the final product. H3PO4 treatment at 600 degrees C and steam treatment at 700 degrees C show maximum surface area of >640 m(2) g(-1) with increased total pore and micropore volumes. (C) 2014 Elsevier Ltd. All rights reserved.

National Category
Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-164448 (URN)10.1016/j.jclepro.2014.12.031 (DOI)000350940400007 ()2-s2.0-84923116542 (Scopus ID)
Note

QC 20150423

Available from: 2015-04-23 Created: 2015-04-17 Last updated: 2017-12-04Bibliographically approved
Burks, T., Akthar, F., Saleemi, M., Avila, M. & Kiros, Y. (2015). ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI). Journal of Environmental and Public health, 2015, Article ID 687094.
Open this publication in new window or tab >>ZnO-PLLA Nanofiber Nanocomposite for Continuous Flow Mode Purification of Water from Cr(VI)
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2015 (English)In: Journal of Environmental and Public health, ISSN 1687-9805, E-ISSN 1687-9813, Vol. 2015, article id 687094Article in journal (Refereed) Published
Abstract [en]

Nanomaterials of ZnO-PLLA nanofibers have been used for the adsorption of Cr(VI) as a prime step for the purification of water.The fabrication and application of the flexible ZnO-PLLA nanofiber nanocomposite as functional materials in this well-developedarchitecture have been achieved by growing ZnO nanorod arrays by chemical bath deposition on synthesized electrospun poly-Llactidenanofibers. The nanocomposite material has been tested for the removal and regeneration of Cr(IV) in aqueous solutionunder a “continuous flow mode” by studying the effects of pH, contact time, and desorption steps.Theadsorption of Cr(VI) speciesin solution was greatly dependent upon pH. SEM micrographs confirmed the successful fabrication of the ZnO-PLLA nanofibernanocomposite.Theadsorption and desorption of Cr(VI) species were more likely due to the electrostatic interaction between ZnOand Cr(VI) ions as a function of pH.The adsorption and desorption experiments utilizing the ZnO-PLLAnanofiber nanocompositehave appeared to be an effective nanocomposite in the removal and regeneration of Cr(VI) species.

Place, publisher, year, edition, pages
Hindawi Publishing Corporation, 2015
Keywords
Chromium, nanofibers, water purification
National Category
Materials Chemistry
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-179870 (URN)10.1155/2015/687094 (DOI)26681961 (PubMedID)2-s2.0-84949238526 (Scopus ID)
Note

QC 20160111

Available from: 2016-01-04 Created: 2016-01-04 Last updated: 2017-12-01Bibliographically approved
Ossman, M. E., Mansour, M. S., Fattah, M. A., Taha, N. & Kiros, Y. (2014). Peanut shells and talc powder for removal of hexavalent chromium from aqueous solutions. BULGARIAN CHEMICAL COMMUNICATIONS, 46(3), 629-639
Open this publication in new window or tab >>Peanut shells and talc powder for removal of hexavalent chromium from aqueous solutions
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2014 (English)In: BULGARIAN CHEMICAL COMMUNICATIONS, ISSN 0324-1130, Vol. 46, no 3, p. 629-639Article in journal (Refereed) Published
Abstract [en]

In this work, talc powder and peanut shells were investigated as potential adsorbents for the removal of hexavalent chromium from aqueous solutions. The effect of important parameters, such as contact time, solution pH and adsorbent dosage were also evaluated for the adsorption process of chromium (IV). The experimental data showed that a contact time of 30 min for peanut shells and 70 min for talc powder and pH of 4 were optimum for the adsorption to reach equilibrium. Furthermore, FT-IR, SEM and BET measurements were made in order to assess the physicochemical properties of the substrates. Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were used to fit the equilibrium data, heat and energy of adsorption of both adsorbents. Determinations of the rate of adsorption using kinetic models follow pseudo-first order for peanut shells and talc powder with intraparticle diffusion.

Keywords
Talc powder, peanut shell, hexavalent chromium, removal, wastewater
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-172197 (URN)000358337200005 ()
Note

QC 20150817

Available from: 2015-08-17 Created: 2015-08-14 Last updated: 2015-08-17Bibliographically approved
Eriksson, T. & Kiros, Y. (2014). Temperature swing adsorption device for oxygen-enriched air. Journal of Cleaner Production, 76, 174-179
Open this publication in new window or tab >>Temperature swing adsorption device for oxygen-enriched air
2014 (English)In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 76, p. 174-179Article in journal (Refereed) Published
Abstract [en]

In connection with a project aimed at producing oxygen-enriched air from ambient air using temperature differences in the so-called temperature swing adsorption (TSA), a device was designed and constructed that took into consideration most of the conceivable parameters governing such a process. While designing the device, care was taken so that it was adaptable to different operating modes, fulfilling high versatility and extending to more processes than producing oxygen-enriched air. The device was small-scale, mounted on a movable table. It was equipped with a total of 54 individually controllable on/off valves. The valves could be controlled at a resolution of 1 s using a programmable logic controller, controlled by a personal computer, so the time program for the valves could be easily exchanged for a readymade program. The device had six cylinders, with removable lids filled with zeolite and easily maintained plastic tubing, which could therefore be changed or replaced without much difficulty. The results show that 15 L of oxygen could be produced at a concentration of 30% in the oxygen-enriched air per kg zeolite and hour. Equipping the device in the future with valves that close and open securely in both directions would vastly extend the possibility of using this technology to other applications, in addition to this method of TSA process for air separation.

Keywords
Temperature swing adsorption, Desorption, Zeolite, Oxygen enrichment
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-148344 (URN)10.1016/j.jclepro.2014.04.024 (DOI)000338002300019 ()2-s2.0-84901839806 (Scopus ID)
Note

QC 20140805

Available from: 2014-08-05 Created: 2014-08-05 Last updated: 2017-12-05Bibliographically approved
Spets, J.-P. -., Lampinen, M. J., Kiros, Y., Rantanen, J. & Anttila, T. (2013). Effect of temperature on a direct glucose anion exchange membrane fuel cell in a near-neutral-state electrolyte. International Journal of Electrochemical Science, 8(1), 1226-1236
Open this publication in new window or tab >>Effect of temperature on a direct glucose anion exchange membrane fuel cell in a near-neutral-state electrolyte
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2013 (English)In: International Journal of Electrochemical Science, ISSN 1452-3981, E-ISSN 1452-3981, Vol. 8, no 1, p. 1226-1236Article in journal (Refereed) Published
Abstract [en]

A direct glucose anion exchange membrane fuel cell (AEMFC) with a near-neutral-state electrolyte was studied at varying temperatures of 20, 30 and 37 ° C at two different concentrations of glucose of 0.1 and 0.3 M and with three concentrations of electrolyte of 0.1, 0.2 and 0.3 M [PO4]tot. The prime objective was to show how specific energy (W kg-1 glucose) of the direct glucose AEMFC is related to the operation temperature and concentrations of the species. Current and voltage values were measured together with the pHs and conductivities of the electrolytes. No component analysis of the final products after the fuel cell operation were done as the oxidation products of glucose is believed to be mainly gluconic acid and unreacted glucose as shown in the low Coulombic efficiency based on the exchange of 24 e-. Temperature, electrolyte and glucose concentrations have shown to have pronounced effect for the achievement of the highest energy capacity of 5.15 Wh kg-1 glucose.

Keywords
Anion exchange membrane, Direct bioorganic fuel cell, Glucose, Near-neutral-state electrolyte, Temperature
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-119363 (URN)000316562800096 ()2-s2.0-84873807827 (Scopus ID)
Note

QC 20130314

Available from: 2013-03-14 Created: 2013-03-14 Last updated: 2017-12-06Bibliographically approved
Marini, S., Salvi, P., Nelli, P., Pesenti, R., Villa, M. & Kiros, Y. (2013). Oxygen evolution in alkali with gas diffusion electrodes. International journal of hydrogen energy, 38(26), 11496-11506
Open this publication in new window or tab >>Oxygen evolution in alkali with gas diffusion electrodes
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2013 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 26, p. 11496-11506Article in journal (Refereed) Published
Abstract [en]

Progresses in the area of the oxygen evolution reaction (OER) are now occurring at a much faster rate relative to few years ago. For this reason, it has been deemed appropriate to present a critical review of the major and most recent contributions towards a fundamental understanding of what determines the OER electrocatalytic properties of a material. Furthermore, the technologies used to produce practical OER electrodes with top activities are assessed and the current benchmarks of performance are identified. Furthermore, results pertaining to our work on Raney-Ni gas diffusion anodes, which have been optimized in thickness and composition, are presented. An addition of 10 wt.% of a Co3O4 micrometric powder as co-catalyst (with Raney Ni-Fe) was found to enhance the polarization behavior and performance. The electrode so obtained achieves activities comparable with those of the best electrodes reported in the literature. Great emphasis has been placed in the analysis of the stability of the prepared Gas Diffusion Electrodes. Most of the GDEs were found to be stable in weeks long experiments with intermittent operation. The issue of integrating several functional layers (gas diffusion layer, active layer with current collector, separator layer) within a single, mechanically strong electrode assembly is briefly addressed.

Keywords
Electrochemical water splitting, Oxygen evolution reaction (OER), Gas diffusion electrodes, Alkaline electrolysis, Raney-Ni
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-129626 (URN)10.1016/j.ijhydene.2013.04.160 (DOI)000324014600033 ()2-s2.0-84882453488 (Scopus ID)
Note

QC 20131003

Available from: 2013-10-03 Created: 2013-10-03 Last updated: 2017-12-06Bibliographically approved
Marini, S., Salvi, P., Nelli, P., Pesenti, R., Villa, M. & Kiros, Y. (2013). Stable and inexpensive electrodes for the hydrogen evolution reaction. International journal of hydrogen energy, 38(26), 11484-11495
Open this publication in new window or tab >>Stable and inexpensive electrodes for the hydrogen evolution reaction
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2013 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 38, no 26, p. 11484-11495Article in journal (Refereed) Published
Abstract [en]

The HER activities of Raney-Ni electrodes obtained by partial leaching of Al in a Ni-Al-Fe alloy doped with Mo, Cr or Pd were studied in 28% KOH. PTFE bonded Gas Diffusion Electrodes (GDEs) were prepared by the rolling method before sintering at 300 degrees C under N-2. Ni in alkaline electrolyte has a lower intrinsic HER activity than Pt in acid. However, the spongy and highly porous character of Raney-Ni greatly enhances HER resulting in a cheap material with outstanding catalytic performance. The polarization behavior of GDEs consisting mainly of Raney-Ni catalysts with optional addition of co-catalyst or conductivity enhancing powders, such as carbonyl iron, carbonyl nickel, copper and molybdenum oxide are studied as a function of temperature and time in order to determine activities, behavior in the high current density regime, and long term stability in view of potential exploitation in industrial electrolysis. Cr and Pd-doped Raney-Ni initially achieve outstanding performances with unusually low "Tafel slopes". After weeks long cathodic treatments, these GDEs eventually attain inferior but stable activities due to an apparently irreversible aging of Raney-Ni. The aging of Mo-doped Raney-Ni is less conspicuous, and relevant performances are sometimes improved by additives. A clear picture is emerging of the mechanisms controlling polarization and aging behavior of Raney-Ni GDEs. From this picture, suggestions are put forward on how to improve stability and performances of full electrode assemblies and make them suitable for use in advanced alkaline electrolyzers.

Keywords
Raney-Ni, Additives, Alkaline electrolysis, Hydrogen evolution, Tafel plots
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-129625 (URN)10.1016/j.ijhydene.2013.04.159 (DOI)000324014600032 ()2-s2.0-84882456379 (Scopus ID)
Note

QC 20131003

Available from: 2013-10-03 Created: 2013-10-03 Last updated: 2017-12-06Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6212-4194

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