The development of effective gas-liquid mixing systems in mechanically agitated vessels is typically evaluated in terms of the degree of bubbles dispersion. For instance, adequate gas distribution reduces the formation of oxygen-deficient regions and ensures suitable metabolic pathways in bioreactors. In this regard, the gas holdup is a direct measurement of the process performance because the bubbles’ arrangement determines the gas volume fraction inside the vessel. The accurate estimation of this parameter using empirical correlations provides a rapid prediction of the mixing characteristics, which is crucial for designing stirred tanks. However, a challenge in obtaining empirical correlations is related to the experimental ranges of geometrical and process system conditions. In fact, the existing gas holdup correlations have not considered gas dispersion in yield pseudoplastic fluids using a coaxial mixer that comprises concentric shafts rotating independently. As an opportunity in mixing process system design, this study aims to develop empirical gas holdup correlations for an aerated anchor-PBT coaxial mixing system containing a xanthan gum solution, which behaves as a yield stress fluid. The electrical resistance tomography technique was employed to measure the gas holdup based on the conductivity variation throughout the vessel. A central composite design of experiments was conducted to account for the effect of central impeller speed, anchor speed, and gas flow rate on the mixing performance. The tridimensional surface graphs demonstrated a non-monotonic effect of the central impeller speed on the gas holdup, which indicates a variation in the flow regime. Furthermore, the results showed that an increase in the anchor speed either increases or decreases the gas holdup depending on the aeration rate applied to the system. The developed correlations were statistically assessed and a good agreement with the experimental data was verified, which enabled us to accurately predict optimum process conditions that enhance the mixing effectiveness.

Probiotic beverages made from cereals are vital alternatives to the current growing drawbacks associated with dairy-based products. Accordingly, this study aimed to evaluate teff-based substrate for its applicable potential to delivering beneficial probiotics, Lactobacillus rhamnosus GG (LGG) and Lactobacillus plantarum A6 (LA6) with a view to develop fermented probiotic beverage. Also, two-dimensional fluorescence spectroscopy was applied to monitor the fermentation process, and the spectral data were analyzed using partial least squares regression (PLSR) and artificial neural network (ANN). The process parameters, time and inoculum were optimized to 15 h and 6 log cfu/mL, respectively. The 15 h fermentation of teff-based substrate, which was inoculated with 6 log cfu/mL mixed-strains of LA6 and LGG was run without pH adjustment. During fermentation, growth of LA6 and LGG increased to 8.416 and 8.247 log cfu/mL, respectively, which are above the minimum required counting of 6 to 7 log cfu/mL. Maltose and glucose were consumed during fermentation, and hence their amounts were decreased. However, lactic and acetic acids produced with fermentation time, therefore their concentrations were increased. Values of pH, titratable acidity, lactic acid, and acetic acids were measured between 6.3–3.9, 0.33–1.5 g/L, 0–1.7 g/L, and 0.04–0.231.5 g/L, respectively. Quantification of metabolites such as glucose and lactic acid with high performance liquid chromatography is challenging since it needs long time, high capital cost, and it is labor-intensive. Also, microbial counting with traditional methods such as plate counting technique is so tedious work. An alternative for this purpose would be the application of two-dimensional fluorescence spectroscopy (Masiero et al., 2013). It is an ideal instrument for the on-line supervision of fermentation processes. In addition, its measurement is non-invasive and does not have interference with the fermenting medium. The prediction abilities of PLSR and ANN models were evaluated by cross validation, and also their predicted values were compared with the actual measurements. This research findings verified that growth of LA6 and LGG, and concentrations of glucose and lactic acid could be predicted by two-dimensional fluorescence spectroscopy combined with PLSR and ANN. In conclusion, whole teff flour without supplement would be used as a substrate to produce probiotic beverage, and also the fermentation process could be supervised using two-dimensional fluorescence spectroscopy.

Green hydrogen is the term used to reflect the fact that hydrogen is generated from renewable energies. This process is commonly performed by means of water electrolysis, decomposing water molecules into oxygen and hydrogen in a zero emissions process. Proton exchange membrane (PEM) electrolyzers are applied for such a purpose. These devices are complex systems with non-linear behavior [1,2] which impose the measurement and control of several magnitudes for an effective [3] and safe operation [4]. In this context, the modern paradigm of digital twin is applied to represent and, even, predict the electrolyzer behavior under different operating conditions. To build this cyber replica, a paramount previous stage consists of characterizing the device by means of the curves that relate current, voltage and hydrogen flow. To this aim, this paper presents a processes supervision system focused on the characterization of a modular experimental PEM electrolyzer. This device is integrated in a microgrid for production of green hydrogen using photovoltaic energy [5]. Three main functions must be performed by the supervision system: measurement of the process magnitudes, data acquisition and storage, and real-time visualization [6,7]. To accomplish these tasks, firstly, a set of sensors measure the process variables. In second place, a programmable logic controller is responsible of acquiring the signals provided by the sensors. Finally, LabVIEW implements the user interface as well as data storage functions. The process evolution is observed in real-time through the user interface composed by graphical charts and numeric indicators. This way, the operator is informed about the process status in a continuous and user-friendly manner, being data stored for further development of the digital twin. The deployed process supervision system is reported together with experimental results to prove its suitability.

References

1. Atlam, O.; Kolhe, M. Equivalent electrical model for a proton exchange membrane (PEM) electrolyser. Energy Convers. Manag. 2011, 52, 2952–2957, doi:10.1016/j.enconman.2011.04.007.
2. Guilbert, D.; Vitale, G. Dynamic emulation of a PEM electrolyzer by time constant based exponential model. Energies 2019, 12, doi:10.3390/en12040750.
3. Scheepers, F.; Stähler, M.; Stähler, A.; Rauls, E.; Müller, M.; Carmo, M.; Lehnert, W. Improving the efficiency of PEM electrolyzers through membrane-specific pressure optimization. Energies 2020, 13, doi:10.3390/en13030612.
4. Frensch, S.H.; Fouda-Onana, F.; Serre, G.; Thoby, D.; Araya, S.S.; Kær, S.K. Influence of the operation mode on PEM water electrolysis degradation. Int. J. Hydrogen Energy 2019, 44, 29889–29898, doi:10.1016/j.ijhydene.2019.09.169.
5. Portalo, J.M.; González, I.; Calderón, A.J. Monitoring system for tracking a pv generator in an experimental smart microgrid: An open-source solution. Sustain. 2021, 13, doi:10.3390/su13158182.
6. Mancera, J.J.C.; Manzano, F.S.; Andújar, J.M.; Vivas, F.J.; Calderón, A.J. An optimized balance of plant for a medium-size PEM electrolyzer. Design, control and physical implementation. Electron. 2020, 9, doi:10.3390/electronics9050871.
7. Hosseinzadeh, N.; Al Maashri, A.; Tarhuni, N.; Elhaffar, A.; Al-Hinai, A. A real-time monitoring platform for distributed energy resources in a microgrid—pilot study in oman. Electron. 2021, 10, doi:10.3390/electronics10151803.

The winery wastewater (WW) generally presents a high organic load and phytotoxicity, constituting an environmental problem if disposed directly to natural water courses or soils. Therefore, suitable treatment processes must be applied to reduce their pollutant load. In this work, it was performed the treatment of WW by employing a modified photo-Fenton process. The aim of this work was (1) application of Ethylenediamine-N,N’-disuccinic acid (EDDS) to reduce the precipitation of iron, (2) evaluate the application of different radiation types (UV-C, UV-A and solar). The results showed that under the best operational conditions, as follows: [Fe²⁺] = 5 mM, [H₂O₂] = 175 mM, [EDDS] = 1 mM, [HA] = 1mM, pH 3.0, agitation 350 rpm, temperature 298 K, UV-C (254 nm), reaction time 240 min, it was achieved a chemical oxygen demand (COD) removal of 99.5%. The pH of the WW was varied from 3.0 to 6.0, and results showed that at pH 6.0 it was achieved a COD removal of 93.2 % (UV-C) > 81.6% (solar radiation) > 60.6% (UV-A) > 8.5% (dark). Therefore, it is concluded that using a pH higher (pH = 6.0) than that usually used for the photo-Fenton process (pH = 3.0) because of EDDS, which reveals the potential application of this process.

The winery wastewater (WW) is characterized for high content of soluble sugars, organic acids, alcohols and high-molecular-weight compounds, such as polyphenols. A coagulation-flocculation-decantation (CFD) process can be applied in combination with a photo-Fenton and adsorption process to remove the organic matter from the WW. Therefore, the aim of this work is (1) study the performance of polyvinylpolypyrrolidone (PVPP) in CFD process, (2) optimize photo-Fenton process and (3) evaluate the efficiency of combined CFD/photo-Fenton/adsorption process. The CFD process was optimized by varying (1) pH (4.0 – 7.0) and (2) [PVPP] (0.5 – 2.0 g/L) and under the best operational conditions ([PVPP] = 0.5 g/L, pH = 6.0, rapid mix (rpm/min) = 150/3, slow mix (rpm/min) = 20/20, sedimentation = 12 h) it was achieved a total organic carbon and total polyphenols removal of 46.9 and 63.3%, respectively. The photo-Fenton process was optimized by varying the Fe²⁺ concentration (1.0 – 2.5 mM) and radiation type (no radiation, UV-C, UV-A). Under the best UV-A-Fenton conditions ([Fe²⁺] = 2.5 mM, [H₂O₂] = 225 mM, pH = 3.0, agitation = 350 rpm, time = 150 min) it was achieved a 69.1 and >99.5%, respectively. To increase the removal efficiency, an adsorption process was applied ([Bentonite] = 1.5 g/L, pH = 6.0, agitation = 350 rpm, sedimentation = 2 h) and it was achieved a 72.0 and >99.5%, respectively. The energy consumption was evaluated, and results showed an Electric energy per Order (E_EO) of 641 and 170 kWh m^-3 order^-1 for UV-A and UV-C respectively. In conclusion, the combination of CFD-photo-Fenton-adsorption is an efficient process for WW treatment.

Human activities have led to environmental pollution also industrial growth and the gradual transition to urbanization are the main causes of the growth of different types of environmental pollutants. The continuation of studies on air quality biomonitoring in the context of “green revolution” have renew the way to use "green tools" using higher plants with specific capabilities-as biomonitors. In the experiments carried out in several locations, with different degrees of pollution, the aim was to assess the responses of plants, aspect and biochemical composition of the biomonitors exposed to various pollutants compared to the unexposed ones, the activity, the methodology and the results obtained being the subject of this paper. These secondary air pollutants are dangerous for living organisms because of their high oxidative potential. In this paper, studies were performed based on the analysis of antioxidant compounds that represent a structural class of chemicals (enzymes) with a wide range of biological functions, with the role of inhibiting free radicals. The experience gained in the study of plant biomonitoring is the basis for the development of new methods of use and study with applicability in research projects due to the immediate, multiple and distinct benefits and as well as the development of efficient and accessible methods.

Polymer nanocomposites with incorporated inorganic nanoparticles are interesting materials for study because of their unique properties. Such hybrid nanomaterials find many applications in various fields of technologies. The properties of polymer nanohybrids are combination of polymeric matrix and inorganic nanoparticles [1].

Nanocomposite hybrid powders of meta-Polybenzimidazole/Titanium dioxide containing 20 wt.% of titania were synthesized by a new in situ sol-gel process with the use of different potassium hydroxide PBI low-alcohol mixtures and titanium (IV) isobutoxide precursor. The phase composition and structure of the prepared hybrid polymer nano powders before and after calcination were characterized by powder X-ray diffraction analysis and Fourier-transform infrared spectroscopy. The photocatalytic ability of the obtained Polybenzimidazole/Titania hybrid nanomaterials were investigated for photocatalytic degradation of Reactive Black 5 (RB5) azo dye as model contaminant from aqueous solution under UV illumination. The degree of degradation of Reactive Black 5 dye at 120 minutes UV irradiation is 58-90 %, using synthesized PBI/TiO₂ nanocomposites as photocatalysts.

References

[1] C. Cazan, A. Enesca, L. Andronic, Synergic effect of TiO₂ filler on the mechanical properties of polymer nanocomposites, Polymers 2021, 13(12), 2017.

Sodium tetradecyl sulfate (STS) is a synthetic organic compound that is prepared by the aldol condensation of methyl isobutyl ketone and 2-ethylhexanal, followed by sulfonation of the resulting alcohol. STS is the largest and most important class of synthetic surfactant used in medicine. It is utilised exclusively as an active ingredient with sclerosing effects. This treatment, called sclerotherapy, has shown efficacy in a number of conditions.

This work, in the form of a patent analysis, presents the state by introducing what has been innovated and patented concerning STS. Furthermore, a detailed analysis of the patentability by using the "chemical compounds search" of the PATENTSCOPE database, has been provided regarding publication years, inventors, applicants, owners, jurisdictions, and classifications.

The scale-up of the gas-liquid mixing process is a challenging task. Some of these challenges are associated with the fluid’s non-Newtonian behavior resulting in oxygen depletion zones upon scale-up. Coaxial mixers have shown a uniform energy dissipation rate throughout the tank and a superior mass transfer rate. However, no investigation has been conducted on the scale-up of the aerated coaxial mixers to the best of our knowledge. Therefore, a scale-up study of an aerated coaxial mixer comprised of a single central impeller and an anchor filled with a non-Newtonian fluid was conducted using the constant mass transfer (k_La) method. In this study, to maintain the large-scale mixer’s k_La the same as its small-scale counterpart, the gas hold-up profile, energy dissipation rate profile, power consumption, and mixing hydrodynamics were investigated. The effects of the impeller type, impeller speed, pumping direction, and aeration rate were explored on the reliability of the scale-up technique through electrical resistance tomography, simplified dynamic pressure method, and computational fluid dynamics. It was found that at the same central impeller tip speed and anchor impeller rotational speed, the flow regime attained by the large-scale mixer was the same as its small-scale counterpart. Furthermore, it was found that the anchor impeller speed should be kept constant in both small-scale and large-scale mixing systems. This was due to the fact that in the large-scale mixer, the central impeller pumping capacity decreased by increasing the anchor impeller speed. Finally, it was observed that keeping both the aeration rate per working fluid volume and the specific power consumption constant between the two scales was the optimum approach to preserve the mass transfer coefficient constant upon scaling-up of the coaxial mixer.

Today, the increase in the need for quality and potable water resources is one of the most crucial issues that all countries of the world are focused on. Particularly, large amounts of highly polluted wastewater are formed together with water consumption that need to be treated in every sector. The toxic and harmful effects of pollutants such as lead still pose a challenge in terms of both environmental and human health in wastewater. Pb⁺² ion is an amphoteric, toxic and bioaccumulative type of primary pollutant commonly found in industrial wastewater. The adsorption process for Pb⁺² treatment is a basic method, and in recent years, adsorption studies have been carried out with various waste adsorbents from the aquatic system. Adsorption is considered the most widely used environmental and green process to remove heavy metal ions among the different processes. So, waste-based adsorbents that do not induce pollution have been evaluated. Therefore, unmodified tea waste, banana, almond, and eggshells were studied for the removal of Pb⁺² ions from the aqueous matrix. With the current process, Pb⁺² removal capacities were investigated by utilizing tea waste, banana, almonds, and eggshells in the aqueous solution. The effects of adsorbent concentrations (0.5-10 g), contact time (5-120 minutes), pH (2-12), and temperature (283.15-308.15 K) on removal efficiency of Pb⁺² were evaluated by batch mode adsorption experiments. Adsorption capacities were calculated using different isotherm and kinetic models due to the experimental datas. The maximum removal efficiencies of Pb⁺² were obtained as 89%, 93%, 98%, and 99% for the four adsorbents under optimum operating conditions respectively. Adsorption was fitted with Langmuir and pseudo-second-order kinetics at the equilibrium state. Experimental results showed that the selected adsorbents are environmentally friendly, economical, and easily obtainable for Pb⁺² removal compared to other adsorbent types.