Exchange Sites Research Articles

Ultra-fine potassium hexacyanoferrate(II) nanoparticles modified ZIF-67 for adsorptive removal of radioactive strontium from nuclear wastewater

Development of a material with high adsorption capacity and selectivity for removal of strontium ion (Sr2+) from nuclear wastewater is a challenge. Herein, dodecahedral zeolitic imidazolate frameworks-67 (ZIF-67) was successfully modified by potassium hexacyanoferrate(Ⅱ) (K4Fe(CN)6) nanoparticles, and used as an effective adsorbent for Sr2+ removal from model wastewater. In construction of adsorbent, methanol was used as the medium for assembly of ultra-fine and uniform 25 nm of K4Fe(CN)6 nanoparticles on ZIF-67, well maintaining the original dodecahedral morphology and mesoporous structure of ZIF-67 crystal. N in 2-methylimidazole (2-MI) bonded with Co to generate ZIF-67, while the unsaturated Co in ZIF-67 bonded with N in K4Fe(CN)6 to form spherical nanoparticles. Specific surface area of ZIF-67 were regulated by K4Fe(CN)6 to an appropriate value of 607.464 m2·g−1 for Sr2+ adsorption. Adsorption efficiency of K4Fe(CN)6 modified ZIF-67 for Sr2+ was significantly enhanced to 90 % within 2 h at ambient conditions, due to the improvement in morphology, structure and chemical property of adsorbent. K4Fe(CN)6 modified ZIF-67 exhibited high adsorption selectivity 45 mg·g−1 for Sr2+ in the presence of competing metal ions such as K+, Na+, Mg2+ and Ca2+, and thus achieved 40 mg·g−1 of adsorption capacity for Sr2+ in actual tap water. Adsorption kinetics and isotherms were well fitted with the second-order kinetics and the Langmuir model, respectively, suggesting a chemisorption process. Mechanism studies showed that the surface of ZIF-67 was uniformly covered by ultra-fine nanoparticles, on the outer layer of which K+ ions were distributed as the adsorption sites for ion exchange with Sr2+.

New insights into the mechanism of cesium sorption on titanium hexacyanoferrate: Experimental findings and model development

This study aimed to provide new insights into the mechanism of Cs+ sorption on titanium hexacyanoferrate (Ti–Fe PBA) focusing on the influence of the structure and vacancies. Ti–Fe PBA was synthesized with specific vacancies using a coprecipitation synthesis method. The study successfully demonstrated the unique structure of Ti–Fe PBA and determined the ratio of vacancies within its framework through various characterization techniques, including X-ray diffraction, Fourier transform-infrared spectrometry, thermogravimetry, scanning electron microscopy, X-ray photoelectron spectroscopy and sodium hydroxide titration. The synthesized Ti–Fe PBA exhibited an impressive Cs+ sorption capacity of 3.53 mmol g−1 and demonstrated high selectivity, with a Kd value 1.5 × 106 for Cs+ sorption. In addition, Ti–Fe PBA displayed excellent stability, rapid uptake kinetics and maintained high selectivity, even in the presence of high concentrations of coexisting ions. Moreover, our new findings revealed that K–Cs ion exchange specifically occurring at the interstitial sites within the framework structure accounted for ∼35 % of the total Cs+ sorption. A sorption-surface complexation model utilizing a coupling technique that integrated PHREEQC with Python enabled in-depth analysis of titration, pH effects and sorption isotherms. The modelling results revealed that the strong ion exchange sites ≡SsOH and ≡SsONa on surfaces and vacancies contributed ∼65 % of the total Cs+ sorption.

Researching Latin America in Liverpool: Transnational Connections of Hope and Solidarity

This article examines archival collections at the University of Liverpool and local community archives documenting academic, political, cultural and personal links between Liverpool and Latin America in the second half of the twentieth century. Centring on collections related to Chile and Central America between the 1960s and 1990s, the analysis highlights hidden histories of transnational solidarity, human rights campaigns and academic research connecting Liverpool with Latin America during a turbulent period of dictatorship, repression and opposition. The varied records – from institutional papers to exile ephemera and cultural artefacts – provide multilayered grassroots perspectives on resistance in Latin America and abroad, revealing the diverse motivations underpinning local solidarity activism. Ongoing digitization and community collaborations based on these archives underline their contemporary significance for research and education. This article argues that as key sites of exchange across activist, academic and migrant communities in Liverpool the archival collections represent vital tools for preserving diasporic heritage, as well as raising awareness of the importance of solidarity with Latin America.

THE IMPACT OF CLIENT COMPANY SIZE, TIME BUDGET PRESSURE AND AUDITOR FREE ON AUDIT QUALITY IN PHARMACEUTICAL SUB-SECTOR COMPANIES LISTED ON THE INDONESIA STOCK EXCHANGE (IDX) PERIOD 2017-2021

This study aims to determine the effect of the variables Client Company Size, Time Budget Pressure and Auditor Fee on Audit QualityThe information utilized in this examination was procured from the Consolidated and Yearly Fiscal Summaries accessible on the Indonesia Stock Exchange (IDX) site. The technique of investigation executed is logistic regression analysis, tested jointly with the overall model fit test which has a significant effect on audit quality. The results of this study indicate that of the three independent variables analyzed, The quality of audit is considerably impacted by the pressure of time and budget, as well as the fee charged by the auditor. However, the magnitude of the client company does not seem to significantly affect the audit quality. The Nagelkerke R Square value indicates that 91.2% of the dependent variable's variability can be explained by the independent variables, whereas the remaining 8.8% is attributed to other variables beyond the research model.

Photochromic hierarchical (NH4)xWO3 nanocrystals with bronze tunnel structure for energy-saving windows

Understanding photochromism is crucial for developing new ways to modulate the optical responses of materials. Here, we prepared ammonium tungsten bronze (NH4)xWO3, representing a significant advance in photochromism over the rarely chromogenic tungsten bronze. The high color difference, 12.89 and 30.49 for 10 s and 90 s exposure, respectively (AM 1.5G), was due to the large surface area created by the distinctive flower-like hierarchical structure, which exposed more photoactive sites, as well as to the highly efficient adsorption of the proton-coupled electron as a color center on the surface to trapped electrons. The elucidation of NH4+ protonation under the light field and/or chemical interactions with neighboring protonated species was revealed by the ion exchange sites in hexagonal, trigonal, and square sites, suggesting an essential surface structure-breaking behaviors of hydrogen bonds between NH4+ and tunneled WO3 frameworks. In particular, the created energy-saving window, based on hydrogen ammonium tungsten bronze (NH4)yWO3:nH/polyvinyl alcohol/polyvinylpyrrolidone coating, enabled a reduction of indoor air temperature by 6.3 °C in hot weather and reduced temperature difference between various indoor areas. The modification of the chemical environment of WO3 and the identification of the photochromism mechanism hold promise for the development of energy-saving windows using chromogenic nanomaterials.

Adsorption of Ba and 226Ra on illite: A comparative experimental and modelling study

Illite, smectite and illite/smectite mixed layers are major phases in various argillaceous rock formations foreseen as potential host rocks for the deep geological disposal of high-level radioactive waste and are important sorbents for cationic radionuclides potentially released in the repository. 226Ra is a critical radionuclide in the safety analysis and an important source of radioactivity in technically enhanced naturally occurring radioactive materials. A comprehensive study was carried out on the adsorption of Ba and Ra on purified homoionic Na-illite (Illite du Puy) over a wide range of experimental conditions (pH, concentration, ionic strength) allowing for the development of a quasi-mechanistic Ba/Ra adsorption model for illite. Ba adsorption isotherms obtained at fixed ionic strength and pH exhibit a non-linear behaviour in the Ba equilibrium concentration range between ∼10−7 and ∼10−2 M. The pH dependent adsorption of trace 226Ra and Ba was investigated at different ionic strengths and evidenced a more pronounced adsorption of 226Ra than Ba on illite. Finally, a competition experiment of trace 226Ra in the presence of increasing Ba concentrations showed an unexpected 226Ra adsorption behaviour which was not observed for montmorillonite in earlier studies. This large set of experimental data could be successfully modelled by Ba/226Ra exchange reactions against Na, together with selectivity coefficients, on two different site types, namely planar sites and high affinity sites. The modelling of the pH dependent adsorption of Ba and 226Ra at high ionic strength and high pH required an additional surface complexation reaction. Two additional exchange sites had to be introduced to quantitatively describe the 226Ra uptake on illite in the 226Ra/Ba competition experiment. The nature of these sites, however, remains unclear. The implementation of the 226Ra adsorption model into predictive transport modelling codes is of key importance for the safety analysis of deep geological disposal of radioactive waste.

Methylation of benzene with methane induced by strong adsorption of benzene on Co ion at α-position in zeolite with moderate Al−Al distance

First principles calculations are applied to find a pathway for methylation of benzene with methane into toluene and dihydrogen catalyzed by MFI type zeolite-supported Co species. On Co2+ at the α-position of MFI framework which is exposed to relatively large space, benzene is strongly adsorbed, while the adsorption on Co at the β-position is weak due to steric hindrance. Energy required for dissociation (activation) of methane was high, but the large energy evolved by adsorption of benzene on Co cancels the activation energy for the methane dissociation to suppress the energies of this step and following formation of toluene precursor. The activation energy of methane dissociation is sensitively changed by Al−Al distance also. Short distance results in difficulty of cleavage of Co–O bond, because Co is fully and strongly coordinated to basic oxygen atoms next to Al atoms, i.e., O in Al–O–Si. On the contrary, Co is partly coordinated to O in Si–O–Si with moderate Al−Al distance, and the cleavage of coordination bond is easy. Too long distance causes difficulty for hopping H+ to reach base site apart from the reaction field. At an appropriate Al−Al distance, the activation energies of the methane dissociation and toluene precursor formation are low. The latter is the rate-determining of benzene methylation with methane, and its energy, i.e., the apparent activation energy is in agreement with the experimental measurements. Experimentally, high activity at the α-position, strong dependence of activity on the framework Al content and the high activity at a moderate framework Al content were observed, supporting the theoretical conclusions. The driving force of benzene methylation with methane, a reaction between a pair of inactive reactants (methane and benzene), is thus clarified to be the strong adsorption of benzene. The origin of catalytic activity is therefore proposed to be strong electron withdrawing nature (Lewis acidity) of Co species held by the ion exchange site of zeolite.

A blockchain‐based user authorization management method for information exchanging of federation of industry and commerce

AbstractThe blockchain does not need the central organization to make trust endorsement, which is suitable for large scale information exchange between different regions. In addition, blockchain has the characteristics of decentralization and tamper resistant, so that it no longer needs an intermediary platform. A blockchain‐based user authorization management method is proposed, which applies blockchain as an underlaying security mechanism for distributed user authorization management within a trusted community of a distributed information exchange sites of federation of industry and commerce. This method can ensure the reliability, consistency, and integrity of user authorization information. With this method, an elastic data exchange trusted community can be built between the data owner and the authorized data user according to the data exchange needs to achieve reliable distributed access authorization.

A potential-driven NiO/NiCo LDH film electrode for highly efficient extraction of Br- via electrochemical coordination and anion exchange

A potential-driven nickel oxide/NiCo layered double hydroxide (NiO/NiCo LDH) composite film was deposited within the stainless steel wire mesh, showing excellent Br− extraction in an electrochemically switched ion exchange (ESIX) system. In this composite film, NiO with a high specific surface area and porous structure served as the lower layer to improve the electrical conductivity and ion storage capacity of the film, while NiCo LDH served as the main selective separation layer to selectively adsorb the target Br−. The film electrode extracted Br− up to 159.25 mg·g−1 and the separation factors of Br−/Cl−, Br−/NO3−, and Br−/I− were 2.04, 8.89, and 5.45, respectively. The film electrode showed excellent adsorption–desorption cyclability and electrochemical stability since the NiO increased the binding force and electrical conductivity between NiCo LDH and substrate, and its porous structure accommodated Br−. The highly efficient extraction of Br− in neutral solution was attributed to the electrochemical coordination and interlayer anion exchange sites of NiO/NiCo LDH. This study provided a deep understanding of the ion selective extraction mechanism of LDH-based materials by ESIX technology and the novel electrochemical reaction design of electrodes, which could be used in other fields such as supercapacitors, sensors, and batteries.

How Shifts in Economic Policy Affect Infrastructure Firm Performance ?

This quantitative research was conducted on companies in the infrastructure sector in Indonesia, Singapore, the Philippines, and Vietnam to see a comparison of economic policies in influencing company performance, the progress of the infrastructure sector, and good implementation in each country. The company performance measurement variables used are ROE and ROA. This research was conducted in a prescriptive way by collecting secondary data from official stock exchange sites, namely the Indonesia Stock Exchange (IDX), Singapore Exchange Limited (SGX), Philippine Stock Exchange (PSE), and Hanoi Stock Exchange (HNX). To find out the relationship between variables, analysis, and data processing in this study we used the Vector Autoregressive (VAR) method. The results of this study are that the economic policies implemented by each country have different impacts according to the economic conditions in the country so they have different impacts on the implementation of monetary and fiscal policies. In Indonesia and the Philippines, the impact of interest rate monetary policy can significantly affect company performance (positive effect), while in Vietnam and Singapore, it is not proven to have a significant effect. In Indonesia and the Philippines, the impact of fiscal policy shows that the performance of companies in the infrastructure sector appears to be positively influenced by the State Budget and IR, but in Vietnam and Singapore, it does not appear to be positively affected.

Influential factors of long-term and seasonal 137Cs change in agricultural and forested rivers: Temperature, water quality and an intense Typhoon Event

In this study, the effect of temperature, water quality, and the impact of an intense typhoon event on change in 137Cs concentration in the water of agricultural and forested rivers near the Fukushima Daiichi nuclear power plant (Japan) was evaluated using monthly stationary observations obtained under baseflow conditions 2.8–10.6 years after the nuclear accident in 2011. The dissolved 137Cs concentration fluctuated seasonally with water temperature in all rivers, and the increase in dissolved 137Cs concentration for unit increase in temperature was higher in forested rivers than in agricultural rivers. The relationship between water temperature and the apparent distribution coefficient of 137Cs well followed the van ’t Hoff equation in the two agricultural rivers, where the enthalpy of reaction was estimated as −15.6 and −19.6 kJ mol−1. The van ’t Hoff equation was not well followed for a forested river, where the suspended solids mainly comprised organic matter, suggesting that the dominant process determining dissolved 137Cs concentrations in forested rivers is not only water temperature effect on ion exchange, but rather the input of 137Cs and K+ (competing with 137Cs for exchange sites on mineral particles) into the water phase via litter leaching. Suspended solids concentrations in agricultural rivers correlated negatively with 137Cs concentrations in suspended solids, suggesting an increased proportion of coarse particles or the input of soils with low 137Cs concentration from decontaminated agricultural land. At some sites, 137Cs concentrations in dissolved form and in suspended solids were reduced sharply in association with the passage of Typhoon Hagibis in October 2019, suggesting that Typhoon Hagibis caused large-scale surface erosion that removed the source of 137Cs.

Reaffirming the Campus as a Sacred Space: A Japanese Case Study

In light of the considerable transformations in higher education that have had an impact on traditional campus experiences, this paper explores the role of university campuses as sacred spaces for young people. In particular, it examines the significance of the material environment in shaping young peoples’ experiences and social memberships within higher education institutions. Drawing on qualitative research, namely digital walkthrough interviews conducted at a Japanese institution during the COVID-19 pandemic, this paper argues that the physical spaces of a university produce special meaning and unexpected attachments for young people, and thus warrants greater attention as a site for social interaction and exchange. It will be shown that there is a need to look beyond the instrumental and purely pedagogic needs of students and place a greater emphasis on efforts to build more socially supportive campus environments. As universities continue the process of reinventing themselves to better fit the ‘new normal’ in a post-pandemic environment, this paper advocates for more consideration of the everyday needs of young people with regard to meaningful interaction, connection and belonging, and how regarding the campus as a sacred space for practices of placemaking and shared experience offers a pathway to fulfill these needs.

The effect of calcium silicate and ground magnesium limestone (GML) on the chemical characteristics of acid sulfate soil.

Acid sulfate soil characterized by pyrite (FeS2) which produces high acidity (soil pH < 3.5) and release high amount of Al3+ and Fe2+. Application of 4 t ha-1 Ground Magnesium Limestone (GML), is a common rate used for acid sulfate soil by the rice farmers in Malaysia. Therefore, this study was conducted to evaluate the integral effect of ground magnesium limestone (GML) and calcium silicate and to determine the optimal combination on acid sulfate soils in Malaysia. The acid sulfate soils were incubated under the submerged condition for 120 days with GML (0, 2, 4, 6 t ha-1) in combination with calcium silicate (0, 1, 2, 3 t ha-1) arranged in a Completely Randomized Design (CRD). The soil was sampled after 30, 60, 90 and 120 days of incubation and analyzed for soil pH, exchangeable Al, Ca, Mg, K and available Si. A total of 2 out of 16 combinations met the desired soil requirement for rice cultivation. The desired chemical soil characteristics for rice cultivation are soil pH > 4, exchangeable Al < 2 cmolc Kg-1, exchangeable Ca > 2 cmolc kg-1, exchangeable Mg > 1 cmolc kg-1 and Si content > 43 mg kg-1. The combinations are i) 2 t ha-1 calcium silicate + 2 t ha-1 GML, and ii) 3 t ha-1 calcium silicate + 2 t ha-1 GML, respectively. These combination rates met the desired requirement of soil chemical characteristics for rice cultivation. Soil acidity was reduced by a gradual release of Ca2+ and SiO32- from calcium silicate continuously filling the exchange sites and reducing the potential of extra (free) H+ availability in the soil system. Combination of calcium silicate and GML, shows the ameliorative effect with; i) release of Ca, ii) binding of Al3+ making it inert Al-hydroxides and, iii) bind H+ to produce water molecules.

Emotions in Crisis: Consequences of Ceremonial Refugee Camp Visits to Bhutanese Refugee Camps in Nepal

Research on refugee resettlement frequently overlooks the larger context of the experience of forced migration. As a result, the micro-level interactions between refugees and the bureaucrats who make resettlement decisions are obscured. We can better understand the socio-political dynamics between refugees and the officials deciding their resettlement cases if we approach encounters between refugees and migration officials during ceremonial visits as sites of emotional exchange. This article examines the complex socio-political emotional exchanges of power and vulnerability that underpin the refugee resettlement process through an ethnographic analysis of Bhutanese refugee camps in Nepal.

Detection of sparse differential dependent functional brain connectivity.

Functional brain connectivity analysis is an increasingly important technique in neuroscience, psychiatry, and autism research. Functional connectivity can be measured by considering co-activation of brain regions in resting-state functional magnetic resonance imaging (rs-fMRI). We propose a novel Bayesian model to detect differential connections in cross-correlated functional connectivity between region of interest (ROI) pairs. The proposed sparse clustered neighborhood model induces a lower-dimensional sparsity and clustering based on a nonparametric Bayesian approach to model sparse differentially connected ROI pairs. Second, it induces a structured dependence model for modeling potential dependence among ROI pairs. We demonstrate Bayesian inference and performance of the proposed model in simulation studies and compare with a standard model. We utilize the proposed model to contrast functional connectivities between participants with autism spectrum disorder and neurotypical participants using cross-correlated rs-fMRI data from four sites of the Autism Brain Image Data Exchange.

A new formulation of the surface charge/surface potential relationship in electrolytes with valence less than three

AbstractSurface complexation models (SCMs) based on Gouy-Chapman theory are often used to describe adsorption of ions onto mineral surfaces. To compensate for the buildup of charge at a solid surface, the composition of the electric diffuse layer next to the surface must balance the surface charge. To calculate the diffuse layer composition, several nonlinear equations and integrals must be solved, usually with an iterative approach. Before convergence, charge balance is typically not fulfilled. One numerical difficulty is that, because of these charge balance errors, the iterative solver may attempt to take the square root of a negative number. Herein, we show that for electrolytes containing only monovalent or divalent ions (i.e., most electrolytes encountered in practice), we can greatly simplify the integrals and eliminate the appearance of complex-valued integrands; it is even possible to derive explicit analytical formulas. Furthermore, using the new method prevents converging to non-physical roots of the Grahame equation, which links surface potential to surface charge. To the best of our knowledge, the presented formulation has not been implemented in geochemical modelling software before, although similar mathematical expressions have been presented in the literature. In Gouy-Chapman theory, ions can only be distinguished by their charges, but this is not consistent with all experimental findings. We present a model that allows for the preferential accumulation of ions in the diffuse layer. The model, which is implemented mathematically by including ion exchange sites with a variable exchange capacity, is flexible and more numerically tractable than the standard models for the diffuse layer.

Reactive Force-Field Molecular Dynamics and Experimental FTIR Analyses of the Impact of State-of-Hydration on Nafion Morphology

For any average value of H2O/exchange-site (λave) for a hydrated Nafion membrane, we show that there exists a wide distribution of local (λlocal) values at any instant. These distributions can be quantified by site-by-site analyses of exchange site environments characterized by molecular dynamics. Reactive force field molecular dynamics (ReaxFF MD) enables consideration of bond breaking events (sulfonic acid dissociation) that occur at λlocal values of 4 or greater. We use ReaxFF MD to predict the distribution λlocal values at any λave, and show how the dynamics elucidate water-rich, hydrophobic and interphasial regions of hydrated membranes. Each λlocal contributes to the vibrational spectrum of the polymer. The overall spectrum of the polymer electrolyte is correlated to the distribution of λlocal. Figure 1

Siting Islamic feminism: The Indonesian Congress of Women Islamic Scholars and the challenge of challenging patriarchal authority

ABSTRACTThis article takes the first ever Indonesian Congress of Women Islamic Scholars (Kongres Ulama Perempuan Indonesia, KUPI), and its methodology for formulating religious opinions, as an entry point for analysing the challenge of challenging male, male-centred, and patriarchal authority in Islam. Although a recent initiative, KUPI must be understood in the context of a long and often contentious history of Indonesian secular activists and Islamic scholars (men and women) sounding each other out and seeking common ground in their efforts to reinterpret religious sources and develop new ideas about the position of women in society. Studying the event ethnographically as a site of public communication and exchange – of religious knowledge, views, and experiences – , and contextualizing it in the history of Indonesian Islamic practices and institutions, we argue that the main significance of KUPI lies in the way in which it expands the global Islamic feminist project from a scholarly and intellectual movement into a locally resonant and potentially impactful social movement.

Introduction. Unsettling encounters: Sites, knowledge exchange, and the making of religion in Southeast Asia and the Caribbean

ABSTRACTThis article introduces a special issue on practices of religious and scholarly knowledge exchange in Southeast Asia and the Caribbean. In both regions, the makings of religion have been informed by unsettling encounters between religious experts on the one hand and academic scholars of, and in, religion on the other. These encounters, we argue, can be revealed and productively analyzed through a focus on sites of learning and exchange, such as schools and universities, temples and monasteries, holy shrines, conferences and workshops, but also texts and archives. At such sites, alternative actors, referred to in this special issue as ‘strategic amateurs and accidental experts’, often emerge as unexpected agents of religious change. After explaining the central theme and approach, we draw together and synthesize two strands of argument found in the separate articles, respectively the centrality of moral geographies and geographic imaginations to the making of religion and the intriguing role played by performances of expertise, either as a form of gatekeeping in religious communities and institutions or as alternative sources of religious knowledge and authority. The article concludes with a reflective note on the role of scholars in both fortifying and destabilizing understandings of region and religion.

Migration of the Cu species by alkali metal potassium on the reaction of NH3 with NOx over Cu-SSZ-13 catalyst

Cu/SSZ-13 catalyst, as an efficient SCR catalyst, may suffer from the environment of complex alkali metal poisoning. Therefore, it is crucial to understand the effect of impregnation alkali metal on a catalyst for NH3-SCR. To explore the role of impregnation potassium on Cu/SSZ-13 catalysts, experiments were carried out to investigate fresh and different potassium content on Cu/SSZ-13 catalysts combined with the simulated gas experimental platform and some characterization methods. The results showed that the NOx conversion was slightly affected by the impregnation potassium content of 0.5 wt%. However, a notable decline in catalytic activity, particularly at elevated temperatures, was observed when the potassium content was increased to 3.0 wt%. In addition, XRD and BET results showed that the surface area of the catalyst was decreased by the blockage of pore channels, especially for the impregnation content of 3.0 wt% potassium, but the structure of the catalyst was not collapsed. The XPS characterization results showed that the impregnation of potassium led to the transformation of isolated Cu2+ species into CuO species on the surface of the catalyst. This transformation was driven by the smaller size of K+ ions, replacing Cu2+ species at exchange sites and forming CuO clusters at higher temperatures. However, the formation of CuO clusters led to a blockage in molecular sieve channels, resulting in decreased catalyst activity.