Influence Of Operating Parameters Research Articles

Optimizing Operational Parameters for Lithium Hydroxide Production via Bipolar Membrane Electrodialysis

Traditional lithium hydroxide production techniques, like lithium sulfate and lithium carbonate causticizing methods, suffer from drawbacks including high specific energy consumption, time-consuming processes, and low recovery rates. The conversion of lithium chloride to lithium hydroxide using bipolar membrane electrodialysis is straightforward; however, the influence of operational parameters on bipolar membrane electrodialysis performance have not been investigated. Herein, the impact of the current density (20 mA/cm2~80 mA/cm2), feed concentration (0.5 M~2.5 M), initial feed pH (2.5, 3.5 and 4.5), and the volume ratio of the feed and base solution (1:1, 2:1 and 3:1) on the current efficiency and specific energy consumption in the bipolar membrane electrodialysis was systematically investigated. The bipolar membrane electrodialysis process showed promising results under optimal conditions with a current density of 50 mA/cm2 and an initial lithium chloride concentration of 1.5 M. This process achieved a current efficiency of 75.86% with a specific energy consumption of 3.65 kwh/kg lithium hydroxide while also demonstrating a lithium hydroxide recovery rate exceeding 90% with a purity of about 95%. This work will provide valuable guidance for hands on implementation of bipolar membrane electrodialysis technology in the production of LiOH.

Experimental study on wavy fin desiccant coated heat exchanger for hybrid air conditioning systems

The desiccant-coated heat exchanger (DCHE) is an energy-efficient alternative dehumidification equipment for humidity control in air conditioning. It exhibits a higher dehumidification performance than other solid desiccant systems and can simultaneously handle both latent and sensible loads. Taking the clue of research outcomes from the alternative heat exchangers to enhance the performance, a wavy fin DCHE is designed, fabricated and tested. Objectives of the study are to (i) analyse the dynamic performance of DCHE, (ii) compare the heat and mass transfer characteristics of plain and wavy fin-type DCHEs, and (iii) examine the influence of different operating parameters on the performance. The experimental investigation shows that the dehumidification capacity and thermal coefficient of performance of the proposed wavy fin DCHE are 0.34 g/s and 1.041, respectively, which are 75 % and 60 % higher than the conventional plain fin type. In addition, the developed DCHE has an average cooling capacity of 0.85 kW, which is 42 % higher. Besides, the total quantity of moisture adsorbed also increased by 35 %. Furthermore, the sensitivity analysis of the parametric study identified air velocity, cold water temperature, and inlet humidity ratio as the most influential operating parameters on the performance of wavy fin DCHE.

Investigation of the Influence of Operating Parameters on the Settling Performance of a Vertical Sedimentation Tank Through Computational Fluid Dynamics Simulations

Investigation of the Influence of Operating Parameters on the Settling Performance of a Vertical Sedimentation Tank Through Computational Fluid Dynamics Simulations

Optimizing energy efficiency in brackish water reverse osmosis (BWRO): A comprehensive study on prioritizing critical operating parameters for specific energy consumption minimization

Reverse osmosis (RO) systems offer a viable solution for treating brackish water (BW), a common but underutilized water resource. However, the energy-intensive nature of brackish water reverse osmosis (BWRO) systems poses affordability challenges to water supply, necessitating a focus on minimizing their energy consumption to support SDG6's goal of providing safe and affordable drinking water for all. This study addresses the critical need to minimize the specific energy consumption (SEC) of a typical BWRO system, defined as the energy consumed per unit of water recovered, mathematically and experimentally. Empirical models were developed proving there is a global minimum SEC while adjusting the operating conditions. Furthermore, we identified the key operating factors influencing SEC and their priority levels, along with their interactive effects. Notably, no prior study has discussed the significance and interaction of these operating factors (e.g., feed water salinity, temperature, pressure, flowrate and membrane permeability) on SEC of a BWRO system. Employing a full factorial experimental design with mixed levels of operating parameters, the study developed regression models that elucidate the mechanistic interaction between these parameters and system performance. Moreover, the models were validated experimentally, with a new dataset demonstrating their accuracy and reliability. ANOVA statistical analysis identified feed salinity, pressure, flow rate, feed flow rate×pressure, salinity×pressure, and temperature as influential operating parameters in reducing SEC, in descending order of importance. Operating within the determined optimum range resulted in a 36 % decrease in SEC and a more than fourfold increase in water recovery. The study's systematic approach and findings can be extrapolated to optimize the performance of other desalination technologies and diverse feed water types, contributing significantly to global water sustainability efforts.

Experimental Study of Electrical-Assisted Nanomachining of Monocrystalline Copper Using Customized Tungsten Tip

As a promising micro/nanofabrication method, electrical-assisted nanomachining has obtained substantial attention due to its high material removal rate and attainable superior surface quality. In this study, a rectangular wave electrical signal was applied for nanomachining by a customized tungsten tip. Owing to the coupling effect between the electric field and mechanical force, the cutting depth of the machined grooves can be expanded. In electrical-assisted groove processing, a depth of 270 nm and an aspect ratio of 0.6 on the copper sample can be achieved. The influence of operation parameters including applied voltage, frequency, duty ratio, normal force and cutting speed on the machining performance was investigated in terms of the groove depth, width, aspect ratio, and surface roughness. The potential machining mechanisms should be a combination of electric field force, nanoscale electric discharge, electric contact thermal effects, possible annealing behavior, and scraping and plowing actions induced by mechanical forces.

Interactions between bacteria and microalgae in microalgal-bacterial symbiotic wastewater treatment systems: mechanisms and influencing factors

Microalgal-bacterial symbiotic wastewater treatment systems (MBSWTSs) have received widespread attention due to their capacity to achieve high pollutant removal efficiency during wastewater treatment, with low energy consumption requirements, efficient carbon sequestration, and wastewater resource utilization. This paper provides an overview of the treatment performance and current research status of MBSWTSs, including a detailed summary of the mechanisms of nitrogen, phosphorus, and carbon removal by MBSWTSs and the interactions between bacteria and microalgae. In particular, this review focuses on the influence of operational parameters on the regulation of the symbiotic system, such as the microalgal:bacterial ratio, N:P ratio, external carbon source, dissolved oxygen concentration, aeration mode, and light availability. Among these factors, the microalgal:bacterial ratio, carbon source, and light availability have an important influence on microalgal-bacterial competition, as well as the trophic mode of the system, biomass production, and the capacity for the process to be practically applied on a large scale. MBSWTSs still have some challenging aspects that have hindered their development and application, such as the unknown mechanism of microalgal-bacterial co-metabolism, limited previous practical applications, algal contamination, and harvesting difficulties. To overcome these challenges, future research requires a multidisciplinary approach, incorporating life sciences, material science, and other disciplines. Comprehensive research should be conducted on the metabolic mechanisms of MBSWTSs, the optimization of process performance and waste resource utilization, providing a theoretical and practical foundation for the practical application of MBSWTSs.

Assessment of Performance and Deactivation Resistance of Catalysts in the Pyrolysis of Polyethylene and Post‐Consumer Polyolefin Waste

AbstractIn the present work, the catalyst performances of USY and REY zeolites and MgO, ZnO, and MgxAlOy oxides are investigated in the pyrolysis of virgin high‐density polyethylene (HDPE) and of post‐consumer polyolefin waste. The influence of operation parameters and catalyst deactivation resistance over four reaction cycles are evaluated. The results indicate that basic oxides do not show relevant cracking activity, so that the only identified effect for these catalysts is the production of liquid products with higher contents of paraffins when compared to thermal pyrolysis. Among the evaluated oxides, MgxAlOy is the most active and resistant to deactivation. The zeolites promote cracking and secondary reactions of isomerization, cyclization, and aromatization. Particularly, USY promotes the production of higher‐quality oils and shows higher deactivation resistance, when compared to REY. Additionally, a significant loss of catalyst activity is identified in reactions conducted with post‐consumer polyolefin wastes. However, increase in rates of coke formation and the presence of contaminants (such as halogens and metals) are not detected in the catalysts after the reactions.

Efficient degradation of naproxen in wastewater using Ag-deposited ZnO nanoparticles anchored on a house-of-cards-like MFI-type zeolite: Preparation and physicochemical evaluations of the photocatalyst

We utilized Pr6-diquat-5 as an organic structure-directing agent (OSDA) to synthesize hierarchically intergrown ZSM-5 (HI-ZSM-5) as a catalytic support. ZnO particles were deposited onto HI-ZSM-5 via precipitation to remediate naproxen (NPX) in wastewater, while Ag was photo-deposited onto ZnO to prevent electron-hole pair recombination. XRD analysis revealed crystalline structures and particle sizes influenced by synthesis temperatures, and FT-IR confirmed ZnO and Ag deposition onto HI-ZSM-5 surfaces. Based on N2 adsorption-desorption isotherms, all samples exhibited Type I and IV isotherms with H4-type hysteresis loops, indicating the presence of both micro- and mesopores within HI-ZSM-5. XPS analysis confirmed the presence of peaks indicating Zn in ZnO and metallic Ag interacting with ZnO. TEM analysis identified aggregated Ag/ZnO nanoparticles in the photocatalysts, while EDX confirmed uniform element distribution. FE-SEM images revealed a uniform distribution of ZnO and Ag on HI-ZSM-5 with “house-of-cards” morphologies. PL analysis indicated reduced electron-hole recombination and an extended lifespan. NPX photodegradation experimental results showed that the reaction rate constant of the 3 %AZ composite was 2.8 times higher than that of ZnO/HI-ZSM-5 (0.0163 vs. 0.059 min−1, respectively). Evaluation of influential operating parameters demonstrated 90.8 % elimination of NPX under optimum conditions: a catalyst dosage of 1.5 g L−1 at pH 5 within 120 min. The impact of common anions on NPX decontamination and the catalyst's capability for COD and TOC removal (up to 62.6 and 53.4 %, respectively) was also discussed. The 3 %AZ optimum catalyst could be recycled for 5 cycles with remarkable reusability, maintaining 80.1 % removal efficiency after five regeneration cycles.

Innovatively-synthesized α-Fe2O3/Ti3C2Tx MXene nanocomposite by dry-impregnation method: Photocatalyst characterization and influence of operational parameters on highly efficient tetracycline degradation

Herein, a facile and cost-effective dry-impregnation method was employed to impregnate α-Fe2O3 onto Ti3C2Tx MXene (Ti3C2). The synthesized α-Fe2O3/Ti3C2Tx MXene (FeTM) photocatalyst with a narrow band gap (2.1 eV) was characterized using XRD, EDS, SEM, UV–Vis, TEM, and BET techniques. The photocatalyst was applied for the optimization degradation condition of tetracycline (TC) under visible light irradiation by measuring the absorbance at a wavelength of 357 nm via Response Surface Methodology (RSM)-Central Composite Design (CCD) method. Maximum degradation rate of pollutant (99.13 %) was achieved under optimized condition (Catalyst dosage: 0.606 g/L, tetracycline concentration: 21.67 mg/L, irradiation time: 93 min, and pH: 3.4). The correlation coefficients, F-value, and p-value are determined to be 99.35, 163.35, and < 0.0001, respectively, confirming the validity of the proposed model. Moreover, the reusability test demonstrates the favorable nanocomposite’s stability in the degradation of tetracycline from wastewater. After four cycles, a degradation efficiency of up to 81.4 % is maintained. The photodegradation kinetics was investigated and the result showed R2 = 0.9887 and K value equal to 0.0183 min−1, which represents a reaction with a quick kinetic. The α-Fe2O3/Ti3C2Tx MXene nanocomposite demonstrates remarkable degradation efficiency and high stability, positioning it as a highly promising candidate for wastewater treatment process.

Design of Experiments for Increasing of Methylene Blue Adsorption onto Cellulose Derivative-Based Composites

Hematite-cellulose acetate composite membranes (M1, M2, and M3) were evaluated for their performance in methylene blue (MB) adsorption. Box-Behnken design was used to evaluate the influence of operational parameters on the adsorption of MB by these adsorbents. The idea was to optimize the process with maximum efficiency on adsorption, through identification of the influential factors to the process, evaluation of interactions between these factors, and modeling mathematical expressions. Adsorption experiments versus time were better described by the non-linear pseudo-first-order model, followed by the pseudo-second-order model, and then the non-linear pseudo-first-order model. The R2 and chi-square values corroborate this finding. Equilibrium data was also evaluated and modeled to the linear and non-linear Langmuir and Freundlich isotherm models. The linear isotherm models were better models to fit the adsorption equilibrium data on the membranes, followed by the non-linear Langmuir model. Thus, it was presumed that chemisorption was the prevailing adsorption mechanism. Additionally, adsorption proved to be exothermic and spontaneous. A quadratic model equation was found to describe the interaction between factors. The coefficients of pH and MB concentration were positive, thus positively affecting the adsorption of MB, but those of the temperature were negative, justifying the negative effect on the adsorption process. Analysis of variance (ANOVA) showed a high coefficient of determination value and a high prediction of the regression model was derived. The highest adsorption capacity was found at the optimum experimental conditions of pH = 9.0, MB initial concentration = 100 mg · L-1 and temperature = 20 ℃. Finally, the composites provided 5 use cycles which is good when considering the adsorbents used in removing textile dyes from wastewater.

The influence of operation parameters on concentration ratio of multi-effect evaporation system with mechanical vapor compression

MVC (mechanical vapor compression) evaporation technology has become a hot research topic due to low energy consumption and high efficiency. Based on conservations of energy and mass, the mathematical model of a multi-effect evaporation system with mechanical vapor compression (MEE-MVC) is established to analyze the effects of key operating parameters. The relationship between concentration ratio (CR) and specific power consumption (SPC) is revealed. Results indicate that more evaporator effects can promote the CR when the total heat transfer temperature difference keeps constant. It can be found that when the total heat transfer temperature difference is greater than approximately 10°C, the CR of different systems are almost fixed between 1.2 and 2.5, but the SPC can reach more than 15kWh/t. CR gradually increased as the temperature of last-effect evaporator secondary vapor increased, and the increase is about 0.3. In particular, by changing the total heat transfer temperature difference or the temperature of secondary vapor of the last effect to increase the CR, the SPC can be reduced and better energy-saving effects be obtained. The change of the CR with the final secondary vapor temperature is the combined effect of boiling point elevation (BPE) and latent heat of the secondary vapor.

Degradation of Stains from Metal Surfaces Using a DBD Plasma Microreactor.

The surface cleaning of metals plays a pivotal role in ensuring their overall performance and functionality. Dielectric barrier discharge (DBD) plasma, due to its unique properties, has been considered to be a good alternative to traditional cleaning methods. The confinement of DBD plasma in microreactors brings additional benefits, including excellent stability at high pressures, enhanced density of reactive species, reduced safety risks, and less gas and energy consumption. In the present work, we demonstrated a DBD plasma-based method for the degradation of stains from metal surfaces in a microreactor. Aluminum plates with capsanthin stains were used to investigate the influence of operational parameters on the decolorization efficiency, including plasma discharge power, plasma processing time, and O2 content in the atmosphere. The results revealed that an increase in plasma discharge power and plasma processing time together with an appropriate amount of O2 in the atmosphere promote the degradation of capsanthin stains. The optimum processing condition was determined to be the following: plasma power of 11.3 W, processing time of 3 min, and Ar/O2 flow rate of 48/2 sccm. The evolution of composition, morphology, bonding configuration, and wettability of aluminum plates with capsanthin and lycopene stains before and after plasma treatment were systematically investigated, indicating DBD plasma can efficiently degrade stains from the surface of metals without damage. On this basis, the DBD plasma cleaning approach was extended to degrade rhodamine B and malachite green stains from different metals, suggesting it has good versatility. Our work provides a simple, efficient, and solvent-free approach for the surface cleaning of metals.

Solar-activated and hydrothermally synthesized effective rGO/Ag2S composites for the destruction of naphthol green B dye and antibacterial applications.

Graphene-based nanocomposites are developing as a new class of materials with several uses. The varied weight percentages of rGO on Ag2S catalysts were synthesized using a simple hydrothermal process and employed for the decomposition of anionic dye naphthol green B (NGB) under solar light. The reduced graphene oxide-based silver sulfide (rGO/Ag2S) nanoparticles were then examined using XRD, SEM, EDS, HR-TEM, XPS, UV-DRS, and PL analysis. Using solar light, the photocatalytic activity of the produced catalyst was examined for the degradation of naphthol green B (NGB) in an aqueous solution. At pH 9, rGO/Ag2S is discovered to be more effective than the other catalysts for the NGB dye mineralization. Analyses have been conducted on the influence of operational parameters on the photo-mineralization of NGB, including the initial pH, initial dye concentration, and catalyst dosage. The dye concentration increased; the efficiency of photocatalytic degradation tended to decrease. Chemical oxygen demand (COD)studies have verified the NGB dye mineralization. Active species trapping revealed that holes, hydroxyl radicals, and superoxide radicals all played major roles in the photocatalytic deterioration of NGB processes. Additionally, a potential mechanism of NGB dye degradation by rGO/Ag2S catalyst is presented. The synthesized compound was further evaluated for antibacterial activity, and the results indicated that rGO/Ag2S were potentially effective antibacterial agents.

Pb (II) Adsorption over Activated Carbon Prepared from Cedrus Deodara Bark by Na2CO3 Activation: Optimal Design for Modelling and Process Optimization

AbstractCedrus deodara is an evergreen cone‐bearing tree and its bark is a common timber industry waste. Activated carbon (CDAC) was prepared from Cedrus deodara bark through Na2CO3 – activation for efficient adsorption of Pb (II) ions. D‐optimal design based on RSM revealed that optimum conditions for preparation of activated carbon involved impregnation ratio=1.02 : 1 (w/w) and pyrolysis temperature=604.7 °C. Using 0.1 g CDAC in 200 ml of 10 ppm Pb (II) solution provided 99.4 % removal at pH 6. D‐optimal design was also employed to optimize the adsorption process and to examine influence of operational parameters including pH, initial Pb (II) concentration and contact time. CDAC was characterized using FE‐SEM, EDS, FTIR, XRD and BET analysis. Adsorption followed pseudo‐second‐order kinetic model and Langmuir isotherm model with maximum monolayer adsorption capacity 236.41 mg g−1. The free energy change (▵G̊=−12.66 kJ mol−1), entropy change (▵S̊=0.28 kJ K−1 mol−1), and enthalpy change (▵H̊=72.07 kJ mol−1) revealed spontaneous and endothermic characteristics of adsorption. For evaluating the performance of CDAC, river water samples from Sangam, a pilgrimage site of India, were treated using a vertical column packed with CDAC. Additionally, the effective cost of CDAC was also evaluated.

Health care utilisation of asylum seekers and refugees in the South-West of Germany.

Limited evidence on utilisation of health care by recently arrived asylum seekers and refugees in high-income countries is available. This study aims to describe the implementation of an integrated care facility (ICF) in an initial reception centre and measure the utilisation of care and the influence of operational parameters. In a retrospective cohort study design, using medical records, we followed inhabitants of a reception centre in Germany between 11.10.2015 and 30.05.2018. We assessed frequency of visits and revisits to a newly established integrated care facility (ICF), and the effects of the ICF on visits to the local emergency department (LED) in the regional tertiary hospital using survival analysis and time series regression. We also explore the influence of operational parameters on the different implementation phases; phase 1: provisional clinic with 1-2 hours of physician presence daily, phase 2: implementation of ICF with 2-4 hours of care by a team of doctors and nurses daily, phase 3: routine running of ICF with daily operational hours of 10am-2pm with care provided by an interdisciplinary team of doctors and nurses. 14,419 total medical visits were recorded from 1,883 persons seeking health care in the ICF. The absolute number of visits per day remained similar over the study period (19·9/day), yet the relative number of visits changed from 2·2 to 15 per 100 inhabitants from phase 2 to 3, respectively. Most visits were due to respiratory infections (612/3080, 20%), and trauma and musculoskeletal conditions (441/3080, 14%). The rate of revisits to ICF was 2·9 per person per month (95%CI 2·9-3), more for those older, female, from North Africa and those with a translator present. The ratio of visits to the LED changed from 0·3/100 inhabitants per day to 0·14/100 inhabitants after implementation of the ICF and back to 0·3/100 inhabitants during the routine running. Though seasonal variation and referral practices must be considered, a high rate of revisits to the ICF were recorded. While visits to the LED decreased after the implementation of the ICF, visits returned to the pre-ICF levels during the routine running of the ICF. The results show that AS&R require reliable access to health care, yet the needs of specific groups of migrants may be different, especially those with language barriers, minority groups or those from certain regions. As such, care should be migrant sensitive and adapt to the changing needs of the population. Though more research is required to better understand the differing needs of migrants, this study may help to inform guidelines surrounding migrant sensitive standards of care in Germany.

Photo-electrocatalytic degradation of remdesivir from aqueous solutions using Ni-doped ZnO nanocomposite: Kinetic, degradation pathway, toxicity reduction and reusability

Currently, there has been increasing interest in developing active photocatalysts for the treatment of wastewaters. In this study, Nickel (Ni)-doped Zinc oxide on a fluorine tin oxide (ZnO/FTO) was synthesized and utilized as an electrocatalyst for efficient degradation and mineralization of remdesivir (REMD). Ni-ZnO/FTO electrode was characterized using XRD, SEM, EDX, LSV, and DRS analyses. The influence of operational parameters on the degradation efficiency procedure was explored in a batch photo-reactor and their optimum values were selected. At optimized conditions (e.g. initial REMD concentration = 1 mg/L, electrolyte concentration = 0.1 g/L, current intensity = 0.03 A, and pH = 7), within 2 h under UV-A, the removal efficiency of initial REMD concentration was 92 %, whereas TOC and COD removal efficiency were found as 80.1 % and 69.5 %, respectively. The assessment of the degradation rate within 2 h indicates that REMD degradation obeyed first order kinetic model. Additionally, in the comparison of degradation and mineralization efficiency of electrolysis, photolysis and photocatalytic and photoelectrocatalysis (PECP) processes for REMD removal, PECP gave the highest efficiency. The toxicity evaluations showed that the toxicity of solutions treated by the proposed PEC process significantly decreased in comparison with untreated controls. Based on reusability investigations, Ni-ZnO/FTO can be reused for at least five repetitive times with suitable efficiency. Moreover, by taking into account all results, it was concluded that the affordability, high potentiality, and well regenerability of Ni-ZnO/FTO make it an attractive electrocatalyst in terms of drug-containing wastewater treatment.

Parametric Investigation of the Effects of Electrical Discharge Machining on Plain D2 Steel

Electrical discharge machining (EDM) has emerged as a pivotal non-conventional production technique due to its unique capability to machine without the cutting tool’s physical contact with the workpiece, making it apt for brittle, delicate, and complex materials. This research delved into the influence of operational parameters—pulse duration (Ton), peak current (Ip), duty cycle (T), and gap voltage (Vg)—on machining attributes, namely material removal rate (MRR), electrode wear rate (EWR), and radial overcut (ROC) for AISI D2 steel. Utilizing the Taguchi L9 orthogonal array for experimental design, nine experiments were conducted, followed by signal-to-noise ratio (S/N ratio) computations. Key findings highlighted a 4.02 dB improvement in the S/N ratio for MRR, leading to a 29.13% improvement; a 10.35 dB enhancement in the S/N ratio for EWR, resulting in a 33.33% reduction; and a 2.20 dB increase in the S/N ratio for ROC, leading to a 28.57% increment. ANOVA analyses further underscored the predominant influence of all four parameters. The significance of these findings lies in optimizing the EDM process for increased efficiency, reduced tool wear, and enhanced precision, potentially leading to cost savings and improved production quality in industrial applications.

Exploring chlorination as a removal process for antiretroviral drugs (Nevirapine and Efavirenz) from water: Effect of operational parameters, kinetics, and trihalomethane formation

This study investigates the removal of antiretroviral drugs (ARVs), Nevirapine (NVP) and Efavirenz (EFV), from drinking water through chlorination, focusing on the influence of pH, temperature, chlorine concentration, and ARV initial concentration on the degradation kinetics and trihalomethane (THM) formation. At 25 °C and an initial concentration of 100 μg/L, the degradation trends for both ARVs were examined across varying pH levels. EFV exhibited greater pH sensitivity, with removal increasing from 37 % at pH 5.5 to 68 % at pH 8, while NVP removal increased only from 40 % at pH 5.5 to 48 % at pH 8. Temperature also played an essential role, as the removal of both ARVs increased with rising temperature, indicating an endothermic reaction. Higher chlorine concentrations resulted in increased removal, >90 % at 5 mg/L for both ARVs. Kinetic analysis revealed second-order behaviour, with higher rate constants observed at pH 5.5–7 for NVP and pH 7–8 for EFV. The intrinsic chlorination rate constants for both ARVs were estimated. The calculated half-lives indicated slow removal. The study also assessed contact time for NVP and EFV in a plug-flow reactor (PFR) and continuous stirred tank reactor model (CSTR). Also considering hydraulic residence time (HRT) rather than reaction time to assess the average amount of time that the ARVs spent in the selected reactors. The HRT for a CSTR was lower than the PFR, and the estimated HRT for a CSTR was a feasible value. The minimum HRT came out to 1.56 h (pH 7.5 and a temperature of 25 °C) for NVP and 1.07 h (pH 7 and a temperature of 25 °C) for EFV. Finally, THM formation was observed, with chloroform, dibromochloromethane and bromoform detected. Among the three THMs, the most significant change occurred between 4 and 6 h, with chloroform levels increasing from 31.59 μg/L to 63.49 μg/L. This study underscores the influence of operational parameters on ARV removal via chlorination. Highlighting pH sensitivity, temperature control, precise chlorine dosage, and environmental concerns such as trihalomethane formation ensures effective disinfection while minimizing negative impacts on both water quality and the environment. Emphasizing the importance of a comprehensive approach to ARV removal in water treatment processes is a proactive measure that integrates considerations of environmental impact, public health, regulatory compliance, and long-term sustainability into the design and operation of water treatment facilities.

Optimizing biogas methanation over nickel supported on ceria-alumina catalyst: Towards CO2-rich biomass utilization for a negative emissions society

Biogas methanation emerges as a prominent technology for converting biogas into biomethane in a single step. Furthermore, this technology can be implemented at biogas plant locations, supporting local economies and reducing dependence on large energy producers. However, there is a lack of comprehensive studies on biogas methanation, particularly regarding the technical optimization of operational parameters and the profitability analysis of the overall process. To address this gap, our study represents a seminal work on the technical optimization of biogas methanation obtaining an empirical model to predict the performance of biogas methanation. We investigate the influence of operational parameters, such as reaction temperature, H2/CO2 ratio, space velocity, and CO2 share in the biogas stream through an experimental design. Based on previous research we selected a nickel supported on ceria-alumina catalyst; being nickel a benchmark system for methanation process such selection permits a reliable data extrapolation to commercial units. We showcase the remarkable impact of studied key operation parameters, being the temperature, the most critical factor affecting the reaction performance (ca. 2 to 5 times higher than the second most influencing parameter). The impact of the H2/CO2 ratio is also noticeable. The response surfaces and contour maps suggest that a temperature between 350 and 450 °C and an H2/CO2 ratio between 2.5 and 3.2 optimize the reaction performance. Further experimental tests were performed for model validation and optimization leading to a reliable predictive model. Overall, this study provides validated equations for technology scaling-up and techno-economic analysis, thus representing a step ahead towards real-world applications for bio-methane production.

Experimental Study of the Influences of Operating Parameters on the Performance, Energy and Exergy Characteristics of a Turbocharged Marine Low-Speed Engine

With appropriate strategy of EVC timing and fuel injection, the engine NOx emission could be reduced with acceptable deterioration of fuel consumption. However, for the mechanism of these favorable results, few studies focus on improving the fuel economy from the perspective of energy and exergy analysis, which could be helpful for providing a deeper comprehensive to researchers. Therefore, an experimental study for the combination of EVC timing and fuel injection strategy is conducted based on a marine low-speed engine with 340 mm bore, then the energy and the exergy analysis are separately carried out according to the obtained experimental results. The experimental results show that delaying the exhaust valve closing (EVC), complemented with an appropriate injection strategy, could improve the marine low-speed diesel engine brake specific fuel consumption (BSFC) with the NOx emission almost kept constant. The following energy balance analysis demonstrates that the losses from exhaust gas and heat transfer account for about 50% of total energy. However, from the perspective of exergy analysis, an opposite conclusion could be obtained; the proportion of exhaust gas and heat transfer exergy could reach about 15%, and the ratio of heat transfer could be higher relatively. The losses caused by irreversibility is the biggest source of all, and the irreversibility from combustion could takes about 70% of the total irreversibility. Finally, the reduction of total irreversibility could reach about 4% by optimizing the parameters of marine low-speed engines.