Band 22, Heft 2

Hydrogen is projected as a key energy vector to achieve aspiring global decarbonization goals mainly for those sectors where greenhouse gas emissions are highly challenging to reduce. Therefore, green hydrogen production using water PEM electrolysis has become the aim of numerous recent studies. One of the crucial challenges for improving hydrogen production is reaching a deep knowledge of the role of anodes electrocatalysts. In this investigation we studied and modeled the effect of different anode electrocatalysts and solid electrolyte’s configurations in a single-cell PEM electrolyzer performance, using EIS. We assembled and tested PEM electrolysis MEAs with two different configurations. MEA-1 comprises in catalyst-coated membrane (MEA)-type with a geometric area of 25 cm 2 containing Nafion™ 115, 3.0 mg cm −2 IrRuOx as the anode, and 3.0 mg cm −2 PtB for the cathode. MEA-2 involves catalyst-coated membrane (MEA)-type with a geometric area of 25 cm 2 containing Nafion™ 117, and 3.0 mg cm −2 PtB both for the anode and cathode. Sintered Ti plates were used as gas diffusion layers. After hydration and activation steps at room temperature, the polarization curve was performed. Hysteresis curves were achieved to provide information on thermal equilibrium during the measurements. The oxygen and hydrogen production rate were measured and compared to theoretical values. Experiments were carried out at 20  and 40 °C. EIS measurements were performed at different points of the polarization curve, sweeping a frequency range between 10 kHz and 10 mHz, with an amplitude of 5 mV and taking 10 points per decade. To avoid electrocatalysts area effects in charge transfer reaction, time constants were calculated. It can be clearly observed the trend of resistances and overpotentials according to different process control. Low onset potential for oxygen evolution reaction depicts for MEA-1 means that there will be less power consumption to achieve the same efficiency or same amount of gas generation rate compared to high onset potential case depicted for MEA-2. Although different membrane thicknesses would result in different electrochemical performances due to the change in the ionic resistance, for the thickness studied we did not observe a change in the ionic resistance. The experimental results show an increase in efficiency with temperature, reflected in higher currents for a given potential and lower time constants resulting in the EIS runs.

The superoleophobic, superhydrophilic, and flame-retardant coatings were obtained through layer-by-layer (LBL) technology using fly ash (FA) as the core. Chitosan (CS), phytic acid (PA), and fluorosurfactant (FS50) were assembled onto FA by LBL assembly using the principle of electrostatic adsorption. The CS and PA were recycled assembled on FA core for 10 layers, which was further deposited with FS50 molecules as the final layer (marked as FA@CS-PA 10 @FS50). Multifunctional coatings consisted of the FA@CS-PA 10 @FS50 powders and polymer binders were formed and could be used on a variety of substrates of various shape and size. The obtained coatings presented superoleophobicity, superhydrophilicity, and flame retardance. The contact angles (CAs) of coated substrates were all greater than 150° towards various oils (rapeseed oil, diesel, hexadecane, and dodecane), while achieved water CAs as low as 0°. The as-fabricated coatings could efficiently separate different oil/water mixtures and lotions while avoiding pollution of the separated materials. The coatings also achieved superior flame retardance, and the fire was self-extinguished within 13 s. Moreover, it also obtained excellent mechanical durability.

Microbial fuel cell (MFC) employs microbial communities as biocatalysts to convert chemical energy from organic substrates to electrical energy. The investigation of MFC incorporated with anaerobic mixed cultures and sulfonated polystyrene (SPS) membrane is of interest for this research due to its competency in generating renewable biological energy and wastewater treatment. Methylene blue was an effective redox mediator in this study. The reactor optimization was performed via the Design of Experiments (DOE) approach using Minitab software. The performance of the batch reactor was optimal with the operating conditions of temperature 30 °C, pH 7, and mediator concentration 250 μM. The contour plots and ANOVA specified that mediator concentration was the most influential parameter that affects MFC performance. MFC fed with 250 μM methylene blue concentration generated a maximum voltage of 0.33 V, current (density) of 4.08 A/m 2 , power (density) of 1.34 W/m 2 . The COD removal was 82.4 % at the end of the batch cycle of seven days. The data obtained from the experiments showed that small amounts of a mediator (250 μM) in wastewater elevate the bio-electricity output of the MFC reactor by 1.22 folds.

Nowadays, the world is facing critical situations such as fossil fuel decline and global warming due to the gradual increase in consumption and release of harmful gases from engines. Therefore, there has been a need for alternative fuels to improve the efficiency of compression ignition (CI) engines and reduce harmful pollutants. Mango seed methyl ester (MSME), obtained from mango seed oil waste through transesterification processes, was used as biodiesel. For best results, 20 % MSME is mixed with 80 % diesel. However, in this experiment, the nanoparticles zinc oxide (ZnO) and graphene were used to improve the emission and vibration properties of MSME20 biodiesel. The results showed about 0.23 % less CO emissions from MSME20 with 100 ppm and 200 ppm ZnO blend than regular diesel. In addition, the graphene nanoparticles in MSME20 also reduced NO x emissions. At full load (100 %), very high NO x emissions of 1235 ppm were observed for the graphene mixture MSME20 at 200 ppm, about 6 % lower than MSME20. Better performance was recorded for the MSME20 100 ppm ZnO and MSME20 200 ppm graphene blends. All other blends, including MSME20, were found to have a higher vibration frequency than conventional diesel at a compression ratio (CR) of 18.

The As (III) uptake capacity of Fe-impregnated AC greatly depends on the availability of active surface sites of iron oxide. In this context, utilizing aluminium as a surface regulator, we proposed a process to attach linked fibrils of FeHO 2 to develop an adsorbent with enhanced As (III) adsorption capacity. The procedure was based on the hydrothermal process using paddy husk-based activated carbon, and both Iron and aluminium ions in the test hydrolysis solution. The exhaust time was observed to rise with increasing dose, falling flow rate, and influent concentration. The CCD optimization result showed that the FeAlPBC was an efficient and cost-effective adsorbent with a maximum response of 1681 min when the independent parameters were retained at 15.0 g FeAlPBC dose, 500 μg/L influent concentrations, 2.0 mL/min flow rate, and a desirability value of 0.986. The experimental results and Thomas and advection-diffusion models were in good agreement. The FeAlPBC samples can be recycled for four cycles with little to no reduction in adsorption capacity. Also, the TCLP test demonstrated that the used FeAlPBC were inert and could be put into landfills without risk. In conclusion, FeAlPBC is a strong contender for removing As (III) from potable water and has a wide range of potential future applications.

High temperature and humidity of many reason of India in the summer season is the major challenge for human comfort also in the drying. In the present work, experiments have been performed to examine the cooling and dehumidification process in the summer season for human comfort and industrial application with the help of calcium chloride (CaCl 2 ) based desiccant material solid desiccant wheel integrated with solar heating arrangements. In this study experimental findings are also evaluated by the mathematical model. During the dehumidification of air in the process unit humidity changes from 17.75 to 29.03 g H 2 O/kg dry air to 2.8–3.9, 6.8–8.15, 8.92–10.9 & 9.79–11.87 g H 2 O/kg dry air for flow rate at 1, 2, 3 & 4 m/s, respectively. The process air outlet temperature is increased in the range of 2.58–3.53 K for all air flow rates. After humidification of process outlet air, human comfort condition (HCC) is produced with temperature and humidity in the range of 30–33 °C and 7.77–12.47 g H 2 O/kg dry air for different air flow rates. Overall airflow for velocity 2–4 m/s can be recommended for the HCC condition. The proposed modelled expression indicates less than 10 % error between the actual and modelled value for different sections.

In this study, rice husk was the precursor for a KOH-activated carbon with high surface area and high micro-porosity. CO 2 adsorption capacity of this material was measured by thermogravimetric analysis. The CO 2 adsorption kinetic showed that equilibrium was reached 30 min after the solid-gas phases came into contact and is well-described by the pseudo-first order model ( R 2  > 0.99 and 95 % confidence level). Intraparticle diffusion model revealed multilinearity over the CO 2 adsorption range. Isotherm data at 25, 35, and 45 °C were well-fitted by the Freundlich model, revealing the adsorbent’s surface heterogeneity and the exothermic behavior of the process. The material reached a maximum CO 2 adsorption capacity of 2.54 mmol/g. A comparison with literature data showed a good agreement.

An investigation was conducted to examine the adsorption of eosin Y (EY) from aqueous solution using Powdered Activated Charcoal (PAC) obtained from Biochem Chemopharma (Quebec, Canada) with a surface area of 270 mg/g using the methylene blue method. The adsorption experiments showed that a contact time of 60 min resulted in a high removal efficiency of 98.25 % for EY at a concentration of 10 ppm. The study also offered insights into the effectiveness of different treatment processes and described the main physicochemical processes involved. Various parameters such as adsorbent dosage, contact time, substrate concentration, and pH were evaluated, and the data were analyzed using Freundlich, Langmuir, and Temkin isotherms. The study found that the pseudo-second-order kinetic model provided a better fit to the experimental data compared to the pseudo-first-order model. To optimize the process parameters and enhance overall efficiency, contour plots were employed in the experimental design, considering variables such as adsorbent dosage, contact time, and pH levels. These plots visually represented the relationship between the variables and the removal efficiency of EY, enabling the identification of optimal operating conditions. The investigation’s findings contribute valuable insights into the adsorption of EY using PAC and offer practical implications for improving the efficiency of EY removal in various applications. The use of contour plots in experimental design was highlighted as a crucial tool for refining adsorption process parameters.

Esterification of acetic acid with methanol to produce methyl acetate and water has been studied in a continuous packed bed catalytic reactive distillation. The key challenge is the startup method of the experiments fora continuous reactive distillation as well as reactive zone height selection. In the present study, the effect of various operating conditions on the methyl acetate composition (mole fraction) is studied. Indion 180 ion-exchange resin solid catalyst is used in the reactive zone. The catalyst is immobilized by using a novel equivalent Katapak-S in the reactive section. Experiments were performed under different operating conditions to find the high purity methyl acetate product in the distillation. The experiments were performed for various conditions like total feed flow rate, reboiler temperature, reflux ratio, methanol to acetic acid mole ratio and catalyst loading with the time. The experiments were carried out till the system reaches to the steady state under different conditions. The maximum methyl acetate concentration is obtained at 80 °C reboiler temperature, 2.01 reflux ratio, 16.3 g/min flow rate, 60 g catalyst loading and 1 mol ratio of methanol to acetic acid. The highest purity of methyl acetate obtained under optimal condition is 95 % by mole.

This work presents a pH control approach, robust to model uncertainties including the scaling-up process. The algorithm is based on a master-slave synchronization, where the real process is taken as the slave, and the master is generated by the real-time simulation of the closed-loop mathematical model of the process. In that sense, the objective is to control the pH value, under minimal process information and subject to perturbations and time-varying references ranging between the basic and acid regions, at laboratory and industrial scales.