Separation Cost Research Articles

Continuous electrophoretic separation of submicron-microplastics from freshwater

Anthropogenic and natural weathering processes have produced submicron microplastics (MPs), an emerging contaminant. Due to small size, the treatment of submicron plastics particles by membrane processes requires small cutoff membranes, which necessitates great pressure gradient and suffers from clogging. The present study aims to develop an electrophoretic separation system for the separation of negatively charged submicron plastics particles from water. An electric field was supplied to produce an electrostatic force to counter the drag force in the permeation stream, thereby, preventing submicron plastics particles from entering the permeate. The critical electric field (Ec) for complete particles removal was estimated based on the dilute-to-influent flow rate ratio (qd), zeta potential, and size of submicron plastics particles. The result showed that at steady-state, particle removal could reach 99% at E > Ec at qd = 0.5. The distribution of plastics particles during electrophoretic separation was analyzed considering electrophoresis and particle deposition. The particle removal efficiency can be modelled by hydraulic condition and critical electric field. Finally, the engineering aspects such as long-term operation, electrode degradation and influence of coexisted constituents were evaluated. The operation cost of electrophoretic separation was calculated to be USD 0.48/m3, which is cost-effective at small scales compared to conventional membrane processes.

Modelling hydrogen deblending from natural gas using Pd-based dense metallic membranes with an empirical polarization model

Low carbon hydrogen can be produced using excess of electric power and further stored into the existing natural gas grid. Deblending processes are required at the end-users side. However, conventional technologies such as adsorption methods can be complex, especially at the small scales, making the investment not convenient. Membrane technology is gaining interest. In scientific literature, Pd-based dense metallic membranes were already identified as a potential solution to separate high purity hydrogen. They can also be coupled with electrochemical hydrogen pump and TSA. However, Pd-based membrane potentiality had not yet been deeply investigated. In this article, a new empirical correlation for concentration polarization losses is found. Thanks to its simplicity and flexibility, it is used to show how an appropriate design of the separation modules can lead to outperform benchmark performance. Different scenarios, with blending at 5%, 10% and 20% and at low (8 bar), mid (40 bar) and high (66 bar) grid pressure are studied to separate 25 kg/day of pure hydrogen. Separation costs obtained with 10% hydrogen blending are below 4.44 €/kg even at low pressure, outperforming benchmark estimations using PSA, that resulted 7.64 €/kg. Polarization correlation is recommended to further improve module design in H2 deblending.

Advances in the catalytic promiscuity of nitrilases

As important biocatalysts, nitrilases can efficiently convert nitrile groups into acids and ammonia in a mild and eco-friendly manner, being widely used in the synthesis of important pharmaceutical intermediates. Early studies reported that nitrilases only had the hydrolysis activity of catalyzing the formation of corresponding carboxylic acid products from nitriles, showing catalytic specificity. However, recent studies have shown that some nitrilases exhibit the hydration activity for catalyzing the formation of amides from nitriles, showing catalytic promiscuity. The catalytic promiscuity of nitrilases has dual effects. On the one hand, the presence of amide by-products increases the difficulties and costs of subsequent separation and purification of carboxylic acid products. On the other hand, however, if the catalytic reaction pathways of nitrilases can be precisely regulated to reshape enzyme functions, the reactions catalyzed by nitrilases can be broadened to provide new ideas for the biosynthesis of high-value amides, which is crucial for the development of artificial enzymes and biocatalysis. This review summarized the research progress in the catalytic promiscuity of nitrilases and discussed the key regulatory factors that may affect the catalytic promiscuity of nitrilases from the evolutionary origin, catalytic domains, and catalytic mechanisms, hoping to provide reference and inspiration for the application of nitrilases in biocatalysis.

Green Ammonia, Nitric Acid, Advanced Fertilizer and Electricity Production with In Situ CO2 Capture and Utilization by Integrated Intensified Nonthermal Plasma Catalytic Processes: A Technology Transfer Review for Distributed Biorefineries

An Integrated Process Intensification (IPI) technology-based roadmap is proposed for the utilization of renewables (water, air and biomass/unavoidable waste) in the small-scale distributed production of the following primary products: electricity, H2, NH3, HNO3 and symbiotic advanced (SX) fertilizers with CO2 mineralization capacity to achieve negative CO2 emission. Such a production platform is an integrated intensified biorefinery (IIBR), used as an alternative to large-scale centralized production which relies on green electricity and CCUS. Hence, the capacity and availability of the renewable biomass and unavoidable waste were examined. The critical elements of the IIBR include gasification/syngas production; syngas cleaning; electricity generation; and the conversion of clean syngas (which contains H2, CO, CH4, CO2 and N2) to the primary products using nonthermal plasma catalytic reactors with in situ NH3 sequestration for SA fertilizers. The status of these critical elements is critically reviewed with regard to their techno-economics and suitability for industrial applications. Using novel gasifiers powered by a combination of CO2, H2O and O2-enhanced air as the oxidant, it is possible to obtain syngas with high H2 concentration suitable for NH3 synthesis. Gasifier performances for syngas generation and cleaning, electricity production and emissions are evaluated and compared with gasifiers at 50 kWe and 1–2 MWe scales. The catalyst and plasma catalytic reactor systems for NH3 production with or without in situ reactive sequestration are considered in detail. The performance of the catalysts in different plasma reactions is widely different. The high intensity power (HIP) processing of perovskite (barium titanate) and unary/binary spinel oxide catalysts (or their combination) performs best in several syntheses, including NH3 production, NOx from air and fertigation fertilizers from plasma-activated water. These catalysts can be represented as BaTi1−vO3−x{#}yNz (black, piezoelectric barium titanate, bp-{BTO}) and M(1)3−jM(2)kO4−m{#}nNr/SiO2 (unary (k = 0) or a binary (k > 0) silane-coated SiO2-supported spinel oxide catalyst, denoted as M/Si = X) where {#} infers oxygen vacancy. HIP processing in air causes oxygen vacancies, nitrogen substitution, the acquisition of piezoelectric state and porosity and chemical/morphological heterogeneity, all of which make the catalysts highly active. Their morphological evaluation indicates the generation of dust particles (leading to porogenesis), 2D-nano/micro plates and structured ribbons, leading to quantum effects under plasma catalytic synthesis, including the acquisition of high-energy particles from the plasma space to prevent product dissociation as a result of electron impact. M/Si = X (X > 1/2) and bp-{BTO} catalysts generate plasma under microwave irradiation (including pulsed microwave) and hence can be used in a packed bed mode in microwave plasma reactors with plasma on and within the pores of the catalyst. Such reactors are suitable for electric-powered small-scale industrial operations. When combined with the in situ reactive separation of NH3 in the so-called Multi-Reaction Zone Reactor using NH3 sequestration agents to create SA fertilizers, the techno-economics of the plasma catalytic synthesis of fertilizers become favorable due to the elimination of product separation costs and the quality of the SA fertilizers which act as an artificial root system. The SA fertilizers provide soil fertility, biodiversity, high yield, efficient water and nutrient use and carbon sequestration through mineralization. They can prevent environmental damage and help plants and crops to adapt to the emerging harsh environmental and climate conditions through the formation of artificial rhizosphere and rhizosheath. The functions of the SA fertilizers should be taken into account when comparing the techno-economics of SA fertilizers with current fertilizers.

Preparation and Characterization of High-entropy Alloys for Electrocatalysis

High-entropy alloys (HEAs), due to their exceptional mechanical properties, thermal stability, and corrosion resistance, have garnered significant attention in the field of materials science. This paper reviews the primary preparation methods of HEAs, such as carbothermal shock, electrochemical synthesis, and spark plasma sintering, and analyzes the characteristics of these methods in terms of compositional control and synthesis efficiency. Through various characterization techniques, researchers can gain an in-depth understanding of the microstructure and elemental distribution of HEAs, thereby enhancing their performance in applications such as catalysis. Although substantial progress has been made in HEA research, challenges such as phase separation and equipment costs continue to hinder large-scale industrial applications. Future studies should focus on improving the controllability and environmental sustainability of preparation processes to advance the widespread application of HEAs in energy, catalysis, and electronics.

Biogas upgrading using aqueous bamboo-derived activated carbons.

CO2/CH4 separation is crucial for biogas upgrading. In this study, the bamboo-derived activated carbons (BACs) were prepared with different ratios of potassium hydroxide (KOH)/bamboo charcoal (BC), and the hybrid sorbents of aqueous BACs were developed for CO2/CH4 separation. Both the gas solubility and sorption rate were measured, and Henry's constant and liquid-side mass-transfer coefficient as well as the CO2/CH4 selectivity were calculated. Meanwhile, the comprehensive performances of aqueous BACs were evaluated using a novel index, and the cost of biogas upgrading using the aqueous BACs was estimated and compared to the commercialized technology. The results proved the effectiveness of aqueous BACs, and the comprehensive performance of 7.0 wt% aqueous BAC with the KOH/BC mass ratio of 2:1 was 4.2 times than that of H2O, having the potential to decrease the average CO2/CH4 separation cost by 65.0% compared to the commercialized technology.

BOTP: 이더리움 블록체인의 최신 블록 해시를 활용한 이중-요소 기반의 예측 불가능한 OTP

A service providing server seeks to achieve enhanced security by requesting the user for presenting an OTP value before executing a critical transaction such as money transfer. The OTP method by a separate token-type battery-powered device is not expected to always work due to the limited battery lifetime of the device, and when a problem occurs, it needs to be replaced for a fee. Other method of generating OTP by executing a mobile app is useful because no separate device is required, but it does not provide the security of the level of two-factor authentication. We propose an OTP scheme that uses the latest block of the Ethereum blockchain to generate and verify unpredictable OTPs by referring to a secret value within a mobile app and other secret stored on a separate media such as a paper. The proposed scheme achieves the high security of dual-factor authentication at no additional cost, without expiration of validity, while ensuring the currency and unpredictability of the generated OTP. Therefore, the introduction of the proposed scheme makes it possible to force the use of OTP in more diverse areas, which can add additional security to various authentication such as passwords, smart keys, and biometric recognition. As a result, it is expected that strengthened authentication can be applied without separate equipment, infrastructure, or cost, which will greatly contribute to the revitalization of Internet commerce and the creation of new business models relied on strong security for user authentication.

Fabrication and enhanced photocatalytic performance of sodium alginate/polyacrylamide hydrogel-supported ZnOVS photocatalysis

Photocatalysis technology, as an environmentally friendly and efficient means of water purification, has shown great potential for the degradation of organic pollutants, but its application is limited by the low efficiency of photocatalysis, the difficulty of catalyst regeneration and the high separation cost. In this study, we innovatively developed a composite photocatalyst supported by low surface oxygen vacancy zinc oxide (ZnOVS) on sodium alginate polyacrylamide hydrogel (ZnOVS/SA/PAM). The reduction in surface oxygen vacancies in ZnO was found to enhance the photocatalytic activity. By incorporating the catalyst into sodium alginate polyacrylamide hydrogel (SA/PAM), the catalyst's reusability can be significantly improved. The experimental results confirmed that the methylene blue (MB) removal efficiency of ZnOVS/SA/PAM was as high as 94.2 % within 120 min, and the adsorption-photocatalytic degradation efficiency remained at a high level of 73.6 % after 10 cycles of use. Therefore, ZnOVS/SA/PAM exhibits great potential as a low-cost, easily recoverable, and efficient photocatalytic composite, which provides a new solution for the efficient removal of organic pollutants in water bodies.

On variants of a load-balancing problem with unit-load jobs

AbstractIn this paper, we reconsider an offline load-balancing problem with unit-time jobs that require one unit from a common resource throughout their execution. In the unit-time case, the jobs have to be assigned to time-slots such that a separable convex function of the load of the resource has to be minimized. Variants of this problem have been studied extensively in the literature under different names. We briefly discuss these problems and give a new implementation for one of them with a better worst-case time complexity than any of the known methods. We also consider the more general preemptive problem in which the execution of the jobs can be interrupted and resumed later. Furthermore, we divide the time horizon into disjoint time intervals, and for each interval, a separable convex cost function is given. The jobs have to be scheduled within their feasible intervals preemptively such that the total cost is minimized, where the cost is determined separately for each interval by the corresponding cost function. We show how to solve this problem in polynomial time by a single minimum-cost-flow computation. For the preemptive problem with one cost function only, we propose a proprietary algorithm for finding a feasible solution which is optimal for any convex cost function. We also present some qualitative computational results.

Optimisation of retailer take-back of low and medium-value products for a circular economy

Used product take-back plays a significant role in the transition to a Circular Economy. Many businesses are introducing retailer-level take-back schemes for low and medium-value products by deploying collection bins for customers to drop off used products. However, the literature has not given much attention to these schemes compared to those with high recovery value products. The viability of such schemes depends on several factors, including the volume of returns and the contamination in the collection bins. We consider a two-echelon reverse supply chain consisting of a retailer taking back low and medium-value used products and delivering them to a recycler for value recovery. We mathematically model the optimal retailer decisions, including the return incentive paid to customers, investment in contamination reduction, the number and capacity of bins, their product assignment, and time between shipments from the retailer to the recycler, and apply the optimisation model to a case study. In addition, our numerical experiments with globally representative parameter value combinations provide generalisable insights for theory and practice. For example, recycling low-value products like plastic containers is economically infeasible for retailers under all conditions. However, including at least one medium-value product, such as apparel, in a take-back programme aids in offsetting its costs. Investing in reducing contamination for any product type is financially unwarranted unless the costs of separation and disposal exceed that of contamination reduction investment. Furthermore, combining multiple product streams into fewer bins could improve financial results, but keeping bins separate may offer psychological benefits to users.

Dynamic modeling and modification of ternary semicontinuous distillation without a middle vessel for improved controllability and energy performance

Ternary distillation conventionally requires two sequential columns. In a process intensification technique, the second column is eliminated by operating the first column in a cyclic manner, where the intermediate component is withdrawn periodically from a side stream. This process, called semicontinuous distillation (SCD) without a middle vessel, can lower the separation costs significantly. However, it exhibits controllability challenges due to the periodic recycling of the side stream. In this work, the process controllability is improved by adding a surge tank in the side stream recycle path. The modification increases significantly the process robustness without changing the operation recipe. Also, the modified SCD can lower maintenance costs as the manipulated variables experience milder oscillations. Moreover, it is shown to have a faster startup than the original design, yielding about 13 % energy saving per feed processed and processing about 25 % more feed during the startup compared with the original design. The case studies show the surge tank volume should be chosen based on the trade-off between attenuation of undesired disturbances and slow-down of desired control actions. Also presented in this article is detailed hybrid discrete-continuous dynamic modeling of the SCD and how the resulting model is implemented in the open-source software OpenModelica.

Techno-Economic Analysis of a Carbon Molecular Sieve-Based Xylene Isomer Purification Process.

The separation and purification of xylene isomers is critical to the production of polyethylene terephthalate (PET). These separations are complex to operate and demand tremendous amounts of energy and thus are an opportunity for reducing industrial energy consumption. Membranes provide a low-energy footprint technology with simpler operation, and recently, membrane materials have been developed that are capable of separating xylene isomers. While these materials have demonstrated the ability to separate xylenes, they have yet to be commercially deployed. This work conducts a techno-economic analysis (TEA) to provide insight on the commercial attractiveness of a p-xylene selective carbon molecular sieve (CMS) membrane from both a cost and energy standpoint. This TEA was conducted through the pairing of a Maxwell-Stefan transport framework for rigid microporous materials with process modeling. Single-stage organic solvent reverse osmosis (OSRO) and pervaporation processes were used to evaluate the effects of recovery, selectivity, and diffusivity on the energy intensity and cost of the xylene separation. The final analysis used two systems, a single pervaporation stage followed by two OSRO stages, which was compared against a three-stage OSRO cascade. These were benchmarked against the commercial Parex process. We estimate that the membrane processes have the potential to enable impressive cost savings compared to the Parex process. While both systems outperformed the Parex process in terms of cost, the pervaporation/OSRO hybrid process was able to achieve the lowest cost of all due to its reduced membrane surface area compared to standalone OSRO. These findings demonstrate the potential of membrane systems in the field of difficult small molecule solvent separations.

Enhanced biomass densification pretreatment using binary chemicals for efficient lignocellulosic valorization

Many effective pretreatment methods (such as dilute acid, dilute alkali, ionic liquids, etc.) have been developed for lignocellulose upgrading, but several defaults of low working mass, high sugar loss and extra cost of solid-liquid separation and water washing hinder their large-scale application in industry. Besides, the valorization of lignin-rich residue from pretreated biomass after hydrolysis or fermentation greatly contributes to the economy and sustainability of lignocellulosic biorefinery, which is usually underestimated. This study developed a densification pretreatment with binary chemicals (densifying lignocellulosic biomass with sulfuric acid (SA) and metal salt (MS) followed by autoclave treatment ((DLCA(SA-MS)), which was conducted under mild condition (121 °C) with a biomass working mass as high as 400 kg/m3. The DLCA(SA-MS) biomass achieved over 95% sugar retention, 90% enzymatic sugar conversion and a high concentration of fermentable sugar (212.3 g/L) with superior fermentability. Furthermore, bio-adsorbent derived from DLCA(SA-MS) biomass residue was highly adsorptive and suitable for dyeing wastewater treatment, providing a feasible and eco-friendly method for lignin-rich residue valorization. These findings indicated that DLCA(SA-MS) pretreatment enables the full-component utilization of biomass and boosts the economic viability of lignocellulosic biorefinery.

Extraction of sustainable and low-emission hydrogen from hydrogen-blended natural gas driven by multi-product sequential separation

Blending hydrogen in natural gas, taking advantage of the readily available pipeline transportation, is considered as a highly promising means of sustainable hydrogen deployment on a vast scale. However, re-obtaining hydrogen from the mixture for end users via conventional separation technologies could pose practical challenges both energetically and economically, due primarily to the relatively low blending ratio (<30 vol%). In contrast to the commonly adopted pressure swing adsorption (PSA) separation, we propose a thermochemical approach of deriving hydrogen with synergistic capture of CO2 by steam reforming of the mixture to tackle such challenges. The process is simulated by a two-dimensional model validated by experimental data. Three typical scenarios with hydrogen blending ratios of 0–30 vol% are investigated in the operating temperature range of 300–400 °C and natural gas pipeline pressure of ≤ 40 bar. Results show that in all scenarios the amount of hydrogen recovered can exceed the amount of renewable hydrogen initially blended and additional hydrogen could be contributed thermochemically, all at relatively low energy cost. Thermochemical methods increase the partial pressure of target products, reducing separation energy and increasing yield. For the typical 10 vol% blending ratio (widely adopted), when considering the separation of hydrogen at the end user and compressing the separated off-gas before transporting it to the next end user, the hydrogen separation cost, after counterbalancing with the revenue from carbon dioxide, is only 1.33$/kgH2 with the new approach. This corresponds to a decrease by over 70.2 % as compared with that of the PSA separation cost (4.45$/kgH2). The captured CO2 in its high-purity form helps to reduce the final cost of hydrogen by a maximum of 0.33$/kgH2. The new route shows great potential for integrated hydrogen production, hydrogen purification and carbon capture for the promotion of renewable energy, green hydrogen and related technologies.

Prioritizing industrial wastes and technologies for bioenergy production: Case study

Energy supply stability in the industrial sector is crucial to maintain operational efficiency and avoiding costly disruptions. In the face of pressing environmental challenges, transitioning to sustainable, efficient, and eco-friendly energy sources is imperative. This study aims to assess the potential of industrial waste for bioenergy production in Khorasan Province, Iran, addressing the research gap of developing a comprehensive framework of criteria that was lacking in previous studies. Employing a combined technology and material assessment methodology, the research began with the collection and analysis of questionnaires to identify and weight critical criteria using Shannon Entropy and expert insights. The Additive Ratio Assessment method was then used to rank various types of industrial waste and technologies according to established value criteria. The Findings reveal that anaerobic digestion of organic waste emerges as the most viable bioenergy solution with an 85 % desirability score, followed by anaerobic digestion of sewage sludge and gasification of plastic waste, scoring 77.31 % and 69.41 %, respectively. The innovative aspect of this study is the development and implementation of five novel evaluation criteria, including process temperature, technology lifetime, production cost, waste collection cost, and waste separation cost, which have not been previously applied to the assessment of industrial waste for renewable energy production, especially in developing countries.

In vitro digestion and fecal fermentation of Tremella fuciformis exopolysaccharides from basidiospore-derived submerged fermentation

Tremella fuciformis polysaccharides (TFPS) belong to natural bioactive macromolecule with both edible and medicinal value, possessing much bioactivities such as anti-tumor, antioxidant, antidiabetics, and immunomodulatory. Currently, the production of TFPS through submerged fermentation (TFPS-1) is gradually replacing the polysaccharides extracted from the fruiting body due to improved fermentation efficiency and reduced separation costs. However, it is still unclear about the effect of TFPS-1 on gastrointestinal digestion and gut microbial fermentation, which is directly related to the function of its biological activity. This study aimed to illustrate the effect of TFPS-1 on digestive process through in vitro digestion and fecal fermentation. TFPS-1 was indigestible during the simulated gastrointestinal tract. But TFPS-1 can be digested by intestinal flora leading to alterations in the total polysaccharides content, molecular weight, and apparent viscosity. Moreover, TFPS-1 regulated the composition of gut microbial, lowering the proportion of Firmicutes to Bacteroidetes and enhancing the abundances of Parabacteroides and Bacteroides. The change of intestinal flora produced more short chain fatty acids and lowered the pH. The KEGG metabolic pathway analysis indicated that TFPS-1 enriched lipid metabolism, glycan biosynthesis and metabolism, and biosynthesis of other secondary metabolites. This study demonstrated that T. fuciformis fermented polysaccharide can be a potential prebiotic to optimize intestinal flora homeostasis and maintain host intestinal health.

Soft and diffusion-controlled Sr-MOF for efficient separation of H2O/D2O

Heavy water (D2O) electrolysis is the primary technology for D2 production, playing an irreplaceable role in fields such as nuclear fusion research and isotope tracing. However, the inherent similarity in chemical properties between H2O and D2O (with only a 1.4 °C difference in boiling points) poses significant challenges to their separation. Furthermore, the extremely low natural abundance of D2O (0.015 %) increases the difficulty and cost of separation, while traditional electrolysis and distillation techniques are highly energy intensive. Therefore, there is an urgent need to develop novel adsorbents for efficient and environmentally sustainable H2O/D2O separation. Herein, we used polydentate ligand 2, 5-dihydroxyterephthalic acid (DOBDC) and its derivatives 4,4́-(anthracene-9,10-diyl) bis (2-hydroxybenzoic acid (ABHB) as raw materials to prepare two novel high coordination Sr-MOFs namely IPE-1 and IPE-2, respectively. These MOFs were applied for efficient separation of H2O and D2O at room temperature. X-ray diffraction results reveal that one Sr atom in IPE-1 is coordinated with 9 oxygen atoms. This high coordination number results in the formation of ultra-small rectangular pores of approximately 2.5 Å. Adsorption isotherms of N2, CO2, H2O, and D2O indicate that the ultramicroporous structure of IPE-1 precludes efficient diffusion of CO2 and H2O molecules into the MOF channels. In contrast, the activated IPE-2 exhibits good CO2, H2O, and D2O uptake capacities of 3 mmol/g, 8.38 mmol/g, and 6.51 mmol/g at 298 K, respectively. The Qst values and Ksap values of H2O and D2O indicate that the adsorption rates of H2O were much higher than D2O under 0.2 < P/P0 < 0.7, with a calculated ratio of approximately 1.26. This study not only provides appealing MOFs materials for efficient H2O/D2O separation at room temperature but also provides a new avenue for preparing adsorbents with high stability and high separation performance.

Mathematical analysis of a mesoscale model for multiphase membranes

AbstractIn this article, we introduce a mesoscale continuum model for membranes made of two different types of amphiphilic lipids. The model extends work by Peletier and the second author (Arch. Ration. Mech. Anal. 193, 2009) for the one‐phase case. We present a mathematical analysis of the asymptotic reduction to the macroscale when a key length parameter becomes arbitrarily small. We identify two main contributions in the energy: one that can be connected to bending of the overall structure and a second that describes the cost of the internal phase separations. We prove the ‐convergence towards a perimeter functional for the phase separation energy and construct, in two dimensions, recovery sequences for the convergence of the full energy towards a 2D reduction of the Jülicher–Lipowsky bending energy with a line tension contribution for phase separated hypersurfaces.

The Heterogeneity of Turn-over Number in Electrocatalysis

Chemical catalysts dominate the multi-billion global revenue of the chemical industry because they accelerate the time it takes a particular reaction to reach equilibrium without altering the equilibrium constant. Electrocatalysis can provide significant benefits compared to other methods, as it has minimal purification and separation costs, is operational at low temperatures and pressures, replaces hazardous and toxic chemical sources with electric current, and can be integrated with renewable energy sources. From a techno-economical point of view, some considerations are critical during a catalyst design: cost, activity, and durability. One useful metric to quantify catalyst durability is turn-over number (TON), which represents the maximum yield of products attainable from a catalytic center. Mathematically speaking, the TON is defined as: TON = ∫0 ∞ TOF(t) dt, where TOF is the turn-over frequency, which is the rate of turn-overs (N) per active site. Currently, without any exception, the TON is given as a fixed number describing the total amount of substrate converted until the catalysts fully degrade. Our approach studies electrocatalytic deactivation processes at the single catalyst level using a technique entitled single-entity electrochemistry for freely diffusing catalysts. The hydrogen evolution reaction (HER) is investigated with platinum nanoparticles as the model catalyst because it deactivates at the nanoscale when the catalytic activity decreases over time. At specific applied potentials, the current measured when a single platinum nanoparticle impacts the electrode creates a transient spike and decay back to the baseline current. TON is quantified by fitting the current decay response and integrating above the fit to find the charge transferred to catalyze the reaction. Our results show that electrocatalyst degradation and TON have a distribution, where some catalysts are more stable than others, and depends on the applied potential and size of the nanoparticles. In order to study how the surface facets of platinum affect the TON, SECCM was coupled with scanning electron microscopy (SEM) to compare the deactivation of a polycrystalline platinum surface in the macro scale with immobilized platinum nanoparticles on a glassy carbon surface. Combining local structural, electrochemical activity, and durability will bridge our fundamental understanding of macro and nanoscale catalyst deactivation processes to assist in the bottom-up approach of material development and design of large-scale industrial electrocatalysts.

COST AND MANAGEMENT ACCOUNTING PRACTICES OF 4 AND 5 STAR HOTELS IN KONYA PROVINCE

In the tourism sector today, where competition is intensely felt and high risk and uncertainty are present, businesses need to effectively and efficiently use their resources to sustain their existence. Hotel busineses, established with high capitals, aim to increase their profitability by controlling costs in these challenging market conditions. Especially, hotel businesses facing situations such as seasonal fluctuations in demand and changing customer needs and expectations, need good management and accounting systems for both performance evaluation and strategic planning. At this point, the presence of management accounting, which provides all the financial and non-financial information needed by the managements and affects decision-making, is of great importance for hotel businesses. Thus, the aim of this study is to examine the management accounting practices of 4 and 5-star hotel businesses in Konya province and to determine their current situation. According to the findings of the research, it has been determined that 50% of the hotel businesses have a separate management accounting department, and 58.3% have a separate cost accounting department. In terms of costing approaches, 66.7% have adopted activity-based costing, 58.3% have adopted full costing approach, and the standard costing approach, at 33.3%, is relatively lower compared to others. Moreover, it has been found that the use of actual costing, budgeting activities, performance evaluation methods, and strategic management accounting practices have a high level of benefit for the businesses.