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  • 1.
    Arfan, Muhammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Soam, Shveta
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Life cycle assessment and life cycle costing of hydrogen production from biowaste and biomass in Sweden2023Ingår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 291, artikel-id 117262Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, an environmental and economic assessment of hydrogen production from biowaste and biomass is performed from a life cycle perspective, with a high degree of primary life cycle inventory data on materials, energy, and investment flows. Using SimaPro LCA software and CML-IA, 2001 impact assessment method, ten environmental impact categories are analyzed for environmental analysis. Economic analysis includes capital and operational expenditures and monetization cost of life cycle environmental impacts. The hydrogen production from biowaste has a high climate impact, photochemical oxidant, and freshwater eutrophication than biomass while it performs far better in ozone depletion, terrestrial ecotoxicity, abiotic depletion-fossil, abiotic depletion, human toxicity, and freshwater ecotoxicity. The sensitivity analysis of LCA results indicates that feedstock to biogas/pyrolysis-oil yields ratio and the type of energy source for the reforming process can significantly influence the results, particularly climate change, abiotic depletion, and human toxicity. The life cycle cost (LCC) of 1 kg hydrogen production has been accounted as 0.45–2.76 € with biowaste and 0.54–3.31 € with biomass over the plant's lifetime of 20 years. From the environmental impacts of climate change, photochemical oxidant, and freshwater eutrophication hydrogen production from biomass is a better option than biowaste while from other included impact categories and LCC perspectives it’s biowaste. This research contributes to bioresources to hydrogen literature with some new findings that can be generalized in Europe and even globally as it is in line with and endorse existing theoretical and simulation software-based studies.

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  • 2.
    Arfan, Muhammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Soam, Shveta
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Biogas as a transport fuel—a system analysis of value chain development in a Swedish context2021Ingår i: Sustainability, E-ISSN 2071-1050, Vol. 13, nr 8, artikel-id 4560Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biofuels policy instruments are important in the development and diffusion of biogas as a transport fuel in Sweden. Their effectiveness with links to geodemographic conditions has not been analysed systematically in studying biogas development in a less urbanised regions, with high potential and primitive gas infrastructure. One such region identified is Gävleborg in Sweden. By using value chain statistics, interviews with related actors, and studying biofuels policy instruments and implications for biogas development, it is found that the policy measures have not been as effective in the region as in the rest of Sweden due to different geodemographic characteristics of the region, which has resulted in impeded biogas development. In addition to factors found in previous studies, the less-developed biogas value chain in this region can be attributed particularly to undefined rules of the game, which is lack of consensus on trade-off of resources and services, unnecessary competition among several fuel alternatives, as well as the ambiguity of municipalities’ prioritization, and regional cultural differences. To strengthen the regional biogas sector, system actors need a strategy to eliminate blocking effects of identified local factors, and national policy instruments should provide mechanisms to process geographical conditions in regulatory, economic support, and market formation.

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  • 3.
    Carlos-Pinedo, Sandra
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Assessment of a full-scale solid-state anaerobic co-digestion: A multi-component substrate analysis by using ORWARE2022Ingår i: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 146, s. 36-43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Long-term sustainable biogas production requires different raw material alternatives, especially when reducing the most desirable organic substrate, food waste, which has been set as a goal in the 2030 Agenda. In Sweden, horse manure (HM) is generated in large quantities, and due to its physical and chemical characteristics, it has the potential to be used as a raw material to produce biogas through anaerobic digestion (AD). In order to investigate the challenges that HM digestion can impose in terms of methane yield and/or digestate quality, the modified ORganic WAste REsearch (ORWARE) AD model was applied. The aim was to study the effects of different substrates and combinations of these on the AD process during a full-scale solid-state (SS)-AD. In this sense, the model allows for the analysis of the digestion process of multicomponent substrates at the element level. The simulation results suggested that the replacement of green waste (GW) by HM with wood chips as bedding material gave the best improvement in terms of energy turnover; the liquid fraction of the digestate of this mixture of substrates presented the highest concentration in all the nutrients analyzed, specifically in total carbon-biological and phosphorus. The nutrient concentrations in the digestate from the aforementioned scenario are in line with the SPCR120 certification.

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  • 4.
    Carlos-Pinedo, Sandra
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Methane yield from SS-AD: Experiences to learn by a full spectrum analysis at laboratory-, pilot- and full-scale2019Ingår i: Biomass and Bioenergy, ISSN 0961-9534, E-ISSN 1873-2909, Vol. 127, artikel-id 105270Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Solid-state anaerobic digestion (SS-AD) takes place when solid content of the substrate is higher than 15%. Some advantages of this technology have been recognized as e.g., less required water added to raw feedstock and consequently minimized digester size and cost, higher volumetric organic loading rates (OLR) that may lead to higher efficiency methane yield and better acceptance of a wide range of feedstocks. However, scientific studies of SS-AD at pilot- and full-scale are very few and difficulties have been reported in operating SS-AD, especially when the system undergoes a scale-up, where methane production is the purpose. As a result, this review gives a summary of scientific studies for SS-AD processes at laboratory-, pilot- and full-scale, where a great diversity of substrate composition, reactor design and operational parameters have been categorized, and their performances in terms of methane yield have been analyzed. This, in turn, helps to identify that factors affecting methane yields at different scales arise mainly from operational conditions as well as the characteristic of feedstocks. This review even contributes to suggest several strategies for improvement of methane yield at full-scale.

  • 5.
    Carlos-Pinedo, Sandra
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Systems analysis of biogas and digestate utilization pathways with carbon capture: A Life Cycle Assessment and a Material and Energy Balance approachManuskript (preprint) (Övrigt vetenskapligt)
  • 6.
    Carlos-Pinedo, Sandra
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Energisystem och byggnadsteknik.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Soam, Shveta
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Study of the digestion process at a full-scale solid-state biogas plant by using ORWARE: Model modification and implementation2020Ingår i: Waste Management, ISSN 0956-053X, E-ISSN 1879-2456, Vol. 107, s. 133-142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The configuration of the reactor influences the digestion process and thus the product yields; other factors such as the rate of biogas production or biogas loss also affect the process specifically with high solid configuration. With these in mind, the ORganic WAste REsearch (ORWARE) anaerobic digestion sub-model was modified to be able to study solid-state anaerobic digestion (SS-AD) (using plug-flow reactor). The simulation results from the updated model agreed with the operational data with respect to methane yield, digestate yield and energy turnover. The model was found to be sensitive to changes in feedstock composition but to a lesser extent to changes in process temperature and retention time. By applying the model on several cases of liquid anaerobic digestion (L-AD), it was noticed that L-AD at mesophilic condition with 25 retention days seemed to be superior to other cases of L-AD with regard to energy turnover. However, even if similar methane production were observed for L-AD and SS-AD, the model suggested higher energy turnover for the case of SS-AD at thermophilic condition, being 10% more in average in comparison with cases of L-AD.

  • 7.
    Guven, Huseyin
    et al.
    Istanbul Technical University, Civil Engineering Faculty, Environmental Engineering Department, Ayazaga Campus, Maslak, Istanbul, Turkey.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Ozturk, Izzet
    Istanbul Technical University, Civil Engineering Faculty, Environmental Engineering Department, Ayazaga Campus, Maslak, Istanbul, Turkey.
    Life cycle assessment of upgrading options of a preliminary wastewater treatment plant including food waste addition2018Ingår i: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 145, s. 518-530Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Life cycle assessment (LCA) is a beneficial tool to evaluate the performance of wastewater treatment plants (WWTPs) and to compare different upgrading options. The main objective of this study is to investigate the environmental impact of upgrading options of a preliminary WWTP in Istanbul, Turkey. The preliminary plant currently consists of mechanical treatment units and various upgrading options including primary treatment and high-rate activated sludge system (HRAS) process as well as the addition of food waste to wastewater were compared. Results showed that the baseline scenario (S0) had worse performance than all future scenarios (S1-3) except for climate change. The scenario of adding food waste to wastewater (S3) has the best performance in climate change, terrestrial acidification, terrestrial ecotoxicity and fossil depletion. Increased addition of food waste was also tested in the sensitivity analysis, and major improvements were obtained especially in climate change and terrestrial ecotoxicity.

  • 8.
    Guven, Huseyin
    et al.
    Istanbul Technical University, Civil Engineering Faculty, Environmental Engineering Department, Istanbul, Turkey.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Eriksson, Ola
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Evaluation of future food waste management alternatives in Istanbul from the life cycle assessment perspective2019Ingår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 239, artikel-id 117999Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In developing countries like Turkey, food waste has the highest share compared to other municipal solid waste components. A detailed life cycle assessment has been performed to evaluate different food waste management options (i.e., landfilling, anaerobic digestion, thermal treatment, co-treatment with municipal wastewater) for Istanbul which is the largest city of Turkey and Europe. The current waste management has the worst environmental performance compared to proposed waste management scenarios as follows: Anaerobic digestion, thermal treatment and co-treatment with municipal wastewater. The thermal treatment scenario has been found to have the best environmental performance in most of the impact categories including climate change. The anaerobic digestion scenario ranks in the first place only in freshwater eutrophication, which is attributed to avoided fertilizer use in this scenario. A drastic improvement with 866% has been found in this category if the anaerobic digestion scenario was followed. Co-treatment with municipal wastewater refers to use of food waste disposers at households and provides improvements especially in marine eutrophication and ecotoxicity. Lower effluent emissions by means of biological wastewater treatment in the co-treatment scenario compared to other proposed scenarios lead to better performance in these categories. Various sub-scenarios have also been investigated such as using biogas as vehicle fuel, replacing a combined heat and power with a condensing plant and increasing food waste addition to sewer lines. Important improvements are not achievable in the first two sub-scenarios; however, increasing food waste addition to sewer lines reduces various environmental impact categories by −41% and −60%. © 2019 Elsevier Ltd

  • 9.
    Pavlova, Anastasia
    et al.
    ITMO University, Russia.
    Sergienko, Olga
    ITMO University, Russia.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Heikinheimo, Lea
    LAB University of Applied Sciences, Finland.
    Obuka, Vaira
    University of Latvia, Latvia.
    Creating aligned studies in resource efficiency and circular economy in the Baltic sea region2020Ingår i: 20th International Multidisciplinary Scientific GeoConference SGEM 2020, SGEM , 2020, s. 685-692Konferensbidrag (Refereegranskat)
    Abstract [en]

    Both in the Central Baltic (CB) countries and Russia, there is a need to develop current education regarding resource efficiency, which is a relatively new and complex issue. The aim of the paper is to present the results of the two parallel twinning international projects "CREA-RE" (Creating aligned studies in Resource Efficiency) and "CREA-RE-RU" (Creating aligned studies in Resource Efficiency in Sweden and Russia), which has been realized from 2018 to 2020. The main goal of the projects was to produceup-to-date aligned training materials for the higher vocational education training (VET) institutions around the CB and enhance cooperation between companies and higher VET. The project promoted the mainstreaming process in the region and best practices through addressing companies and future workers, i.e. students. The overall objective has been achieved through 1) Aligning and producing learning content to be used in higher environmental VET studies; 2) Producing a channel to share aligned materials; 3) Implementing joint innovative cooperation between companies and higher VET to ensure better matching of work opportunities in sustainable business. The activities enabled the creation of a holistic view of students and companies in the theme of resource efficiency and circular economy. Based on different know-how of the partners on the relatively new and complex issues within the theme of resource efficiency and circular economy, the project created aligned e-learning material with a new perspective in the area. Joint practice-oriented case studies promoted companies’ awareness on resource efficiency and enhance their competitiveness, meanwhile enable institutions’ better understanding of the needs in the working life. New information produces a competent labor force to support the integration of the CB labor market, also including Russia. 

  • 10.
    Rambaree, Komalsingh
    et al.
    Högskolan i Gävle, Akademin för hälsa och arbetsliv, Avdelningen för socialt arbete och kriminologi, Socialt arbete.
    Sundström, Agneta
    Högskolan i Gävle, Akademin för utbildning och ekonomi, Avdelningen för ekonomi, Företagsekonomi.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Wright, Sandra A. I.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektroteknik, matematik och naturvetenskap, Biologi.
    Qualitative stakeholder analysis for a Swedish regional biogas development: A thematic network approach2021Ingår i: Sustainability, E-ISSN 2071-1050, Vol. 13, nr 14, artikel-id 8003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The creation of pathways toward a societal transition to clean energy requires the engagement of multiple stakeholders with different and sometimes conflicting interests. In this connection, stakeholder analysis (SA) offers a technique for identifying, assessing and structuring different needs, interests and concerns related to different stakeholders within the context of sustainability. This article aims to present the findings from a qualitative stakeholder analysis (QSA) by using a thematic network approach (TNA), with the help of the ATLAS.ti software. It focuses on Project X, which was aimed at engaging multiple stakeholders and creating favorable conditions for small and medium-sized companies in a region situated in the central part of Sweden, with the potential to start biogas production. In this work, the findings and discussions of the QSA using TNA are structured by using the political, economic, social, technological, environmental and legal (PESTEL) themes of the model. The present study concludes that for the small-scale biogas industry to successfully develop an understanding of the possibilities of the biogas value chain, it is necessary to have analyzed the nature of the main themes by which various stakeholders relate to biogas production and envision their contribution to creating a sustainable society. Herein, we demonstrate that QSA by a TNA, combined with the application of a PESTEL model, are valuable analytical tools in sustainable project management. The lessons from Project X can be applied to other local biogas initiatives, as many identified threats and opportunities are shared by others. 

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  • 11.
    Rueda-Avellaneda, Juan Felipe
    et al.
    Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, Mexico.
    Gomez-Gonzalez, Ricardo
    Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, Mexico.
    Rivas-García, Pasiano
    Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, Mexico;Centro de Investigación en Biotecnología y Nanotecnología, Facultad de Ciencias Químicas, Universidad de Nuevo León, Apodaca, Nuevo León, Mexico.
    Benitez-Bravo, Reyes
    Facultad de Ciencias Químicas, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, Mexico.
    Botello-Álvarez, José Enrique
    Departamento de Ingeniería Bioquímica, Instituto Tecnológico de Celaya, Celaya, Guanajuato, Mexico.
    Wang, Zhao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, Miljövetenskap.
    Application of a sustainable location index approach to landfill site selection in Monterrey, Mexico2023Ingår i: Waste Management & Research, ISSN 0734-242X, E-ISSN 1096-3669, Vol. 41, nr 5, s. 1014-1025Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Landfilling is the main method to manage municipal solid waste (MSW) in Latin America due to the economic, technological and political characteristics of the region. The disposal of MSW in landfill sites may affect the quality of the environment and compromise a considerable share of the municipal budgets. The selection of suitable sites reduces the environmental and economic impact of landfills. In the present study the sustainable location index (SLI) is proposed as a methodology to assess environmentally, and economically, sanitary landfill site selection in the Metropolitan Area of Monterrey, a representative large-size city of Latin America. EVIAVE methodology was modified to include administrative and economic dimensions, which are assessed as a sustainable approach using together the SLI integrated with geospatial and multicriteria analysis tools. The assessment showed that the zones with the lowest SLI changes drastically when the importance of the economic or environmental factor varies. This result suggest that the inclusion of sustainability in landfill site selection decision-making is complex and it may requires the inclusion of local particularities such as municipal budgets, policies of MSW management and public perception about environmental deterioration.

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  • 12.
    Wang, Zhao
    KTH.
    A weighted correlation approach of the density functional theory for an inhomogeneous fluid at an interface2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This doctoral thesis presents a newly developed density functional theory (DFT), i.e., the weighted correlation approach (WCA), to study the structural and thermodynamic properties of an inhomogeneous fluid at an interface. The WCA approach provides a generic formulation to evaluate the change of the single-particle direct correlation function in terms of a series of pair direct correlation functions weighted by different correlation-weight functions with adjustable correlation-weight factors. When applied practically, however, an approximation of the pair direct correlation function has to be made, together with appropriate definitions of the weighted densities and the choices of the correlation-weight functions. Despite this seeming complexity, it is shown that the WCA approach can be regarded as a generalization of the classic density functional approaches and this enables us to develop and apply DFT methods in different ways. For demonstration purposes, several implementations of the WCA approach are proposed and applied to predict the density distribution of an inhomogeneous fluid at an interface. The WCA approach is also employed with a novel pressure expression to investigate the inhomogeneous fluid-mediated interaction pressure for different cases. The WCA calculations from the above applications suggest that it is a successful approach for describing the structural and thermodynamic properties of an inhomogeneous fluid at an interface, as compared to the published results of the Monte Carlo simulations, density functional methods and experimental data.

  • 13.
    Wang, Zhao
    et al.
    KTH, Kemisk apparatteknik.
    Liu, Longcheng
    KTH, Kemisk apparatteknik.
    Hard-sphere fluid-mediated interaction: a novel pressure expression with application of the weighted correlation approachManuskript (preprint) (Övrigt vetenskapligt)
  • 14.
    Wang, Zhao
    et al.
    KTH, Kemisk apparatteknik.
    Liu, Longcheng
    KTH, Kemisk apparatteknik.
    The swelling pressure of Na-bentonite: Study with a density functional approach2012Ingår i: Chemistry Letters, ISSN 0366-7022, E-ISSN 1348-0715, Vol. 41, nr 10, s. 1346-1348Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The combination of the fundamental measure theory (FMT) and the weighted correlation approach (WCA) within the framework of the density functional theory, i.e., the FMT/ WCA approach, is applied to study the swelling pressure of Nabentonite at different salt conditions. Good agreement between the FMT/WCA simulations and the results from both experiments and a Donnan-equilibrium-based DLVO model suggests that the hydration repulsion between charged surfaces can be well accounted by the ionion correlations effect.

  • 15.
    Wang, Zhao
    et al.
    KTH, Kemisk apparatteknik.
    Liu, Longcheng
    KTH, Kemisk apparatteknik.
    Weighted correlation approach: An extended version with applications to the hard-sphere fluid2012Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 86, nr 3, artikel-id 031115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study is to extend the weighted correlation approach (WCA) for inhomogeneous fluids. It now introduces a generic expression to evaluate the single-particle direct correlation function in terms of a series of pair direct correlation functions weighted by different correlation-weight functions and adjustable weight factors. When applied for practical use, however, approximations of the pair direct correlation functions have to be made, together with appropriate definitions of the weighted densities and the choices of the correlation-weight functions. The WCA approach would, then, not only help us to connect and compare different strategies and their underlying assumptions in the density functional approaches, but also enable us to propose and apply density functional theory methods to predict the density profile of, e. g., the hard-sphere fluid confined between a pair of parallel planar hard walls. Numerical results of the extended WCA approach, against the Monte Carlo (MC) simulations in a range of surface separations and bulk densities, suggest that it is capable of representing the fine features of the hard-sphere density distributions. The WCA results also agree well with the calculations from the fundamental measure theory. In addition, the thermodynamic self-consistency of the WCA approach is confirmed by its fairly good agreement with the MC fitted data for the surface tension of a hard-sphere fluid at a planar hard wall. All these tests show that a pure WCA approach can be constructed to investigate the states of ionic hard-sphere fluids.

  • 16.
    Wang, Zhao
    et al.
    KTH.
    Liu, Longcheng
    KTH, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Kemisk apparatteknik.
    A novel method to describe the interaction pressure between charged plates with application of the weighted correlation approach2011Ingår i: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 135, nr 24, s. 244107-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on the Euler-Lagrange equation for ion density distribution in an inhomogeneous, charged, and hard-sphere fluid, a novel method is proposed to determine the interaction pressure between charged plates. The resulting expression is a sum of distinct physical contributions to the pressure, which involves different contributions to the single-particle direct correlation function. It can, therefore, be conveniently used in any density functional approach to facilitate analysis of the pressure components. In this study, the so-called fundamental measure theory (FMT)/weighted correlation approach (WCA) approach is applied to estimate both the hard-sphere and the electric residual contributions to the single-particle direct correlation function, upon the calculation of the ionic density profiles between charged plates. The results, against the Monte Carlo simulations, show that the FMT/WCA approach is superior to the typical FMT/mean spherical approximation approach of the density functional theory in predicting the interaction pressure between charged plates immersed in an electrolyte solution upon various conditions in the primitive model. The FMT/WCA approach can well capture the fine features of the pressure-separation dependence, to reproduce not only the shoulder shape and the weak attractions in monovalent electrolytes but also the strongly oscillatory behavior of pressure in divalent electrolytes where pronounced attractions are observed. In addition, it is found that the FMT/WCA approach even has an advantage over the anisotropic, hyper-netted chain approach in that it agrees with the Monte Carlo results to a very good extent with, however, much less computational effort.

  • 17.
    Wang, Zhao
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Liu, Longcheng
    Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.
    Neretnieks, Ivars
    Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.
    Hard-sphere fluid mediated interaction: a pressure expression with application of the weighted correlation approach2016Ingår i: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 114, nr 5, s. 599-607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By using a so-called differential-integral method on the chemical potential of a hard-sphere fluid, a special variant of our previously developed expression that describes the interaction between charged plates immersed in an electrolyte, is introduced to examine the hard-sphere fluid mediated pressure in a slit. The resulting expression consists of a kinetic contribution and a hard-sphere contribution, and it is formulated as a function of the single-particle direct correlation function and the density distribution of a hard-sphere fluid. It allows us to conveniently apply the classic density functional theory to explicitly investigate the influence of the hard-sphere excluded-volume effect on the interaction pressure between surfaces. In this study, a newly proposed weighted correlation approach (WCA)-Denton and Ashcroft (DA) method is employed to predict the interaction pressure as well as its pressure components for a hard-sphere fluid inside a slit pore. Comparisons with the results from the Monte Carlo simulations and the fundamental measure theory suggest that the WCA-DA method is able to accurately capture the detailed characteristic pattern of the pressure-separation curves at different fluid densities. It is also found, both qualitatively and quantitatively, that the hard-sphere pressure contribution dominates over the kinetic pressure contribution in determining the oscillatory behaviour of the interaction pressure curves, especially when a hard-sphere fluid of high density is concerned.

  • 18.
    Wang, Zhao
    et al.
    KTH.
    Liu, Longcheng
    KTH, Kemisk apparatteknik.
    Neretnieks, Ivars
    KTH, Kemisk apparatteknik.
    The weighted correlation approach for density functional theory: a study on the structure of the electric double layer2011Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, nr 17, artikel-id 175002Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Within the framework of density functional theory, a weighted correlation approach is developed in order to obtain the density distributions of an inhomogeneous fluid. It results in a formally exact expression, by means of the concept of a weighted pair correlation function, used to evaluate the change of the single-particle direct correlation function of the system relative to that of a reference state. When applying the approach for practical use, however, an approximation of the pair correlation function has to be made, along with an appropriate definition of a weight function. Noticeably, combining this approach with fundamental measure theory gives rise to a new method, which we call the FMT/WCA-k(2) approach, for studying the structural and thermodynamic properties of a charged hard-sphere fluid subjected to a spatially varying external potential. Application of the FMT/WCA-k(2) approach in a range of electrolyte concentrations and surface charge densities, against the Monte Carlo simulations, shows that it is superior to the typical approaches of density functional theory in predicting the ionic density profiles of both counter-ions and co-ions near a highly charged surface. It is capable of capturing the fine features of the structural properties of the electric double layers, to well reproduce the layering effect and the charge inversion phenomenon, also in strongly coupled cases where divalent counter-ions are involved. In addition, it is found that the FMT/WCA-k(2) approach even has an advantage over the anisotropic, hyper-netted chain approaches in giving better agreement with the Monte Carlo results.

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