Search Results (503)

Dissolved inorganic nitrogen (DIN) species are key components of the nitrogen cycle and are the main nitrogen pollutants in groundwater. This study investigated the interconversion and removal of the principal DIN compounds (${\mathrm{NO}}_3^{-}$, ${\mathrm{NO}}_2^{-}$ and ${\mathrm{NH}}_4^{+}$) via UV light irradiation using a medium-pressure mercury lamp. The experiments were carried out systematically at relatively low nitrogen concentrations (1.5 mM) at varying pHs in the presence and absence of oxygen to compare the reaction rates and suggest the reaction mechanisms. ${\mathrm{NO}}_3^{-}$ was fully converted into ${\mathrm{NO}}_2^{-}$ at a pH > 3 in both oxic and anoxic conditions, and the reaction was faster when the pH was increased following a first-order kinetic at pH 11 (k = 0.12 min⁻¹, R² = 0.9995). ${\mathrm{NO}}_2^{-}$ was partially converted into ${\mathrm{NO}}_3^{-}$ only at pH 3 and in the presence of oxygen and was stable at an alkaline pH. This interconversion of ${\mathrm{NO}}_3^{-}$ and ${\mathrm{NO}}_2^{-}$ did not yield nitrogen loss in the solution. The addition of formic acid as an electron donor led to the reduction of ${\mathrm{NO}}_3^{-}$ to ${\mathrm{NH}}_4^{+}$. Conversely, ${\mathrm{NH}}_4^{+}$ was converted into ${\mathrm{NO}}_2^{-}$, ${\mathrm{NO}}_3^{-}$ and to an unidentified subproduct in the presence of ${\mathrm{O}}_2^{ }$ at pH 10. Finally, it was demonstrated that ${\mathrm{NO}}_2^{-}$ and ${\mathrm{NH}}_4^{+}$ react via UV irradiation with stoichiometry 1:1 at pH 10 with the total loss of nitrogen in the solution. With these results, a strategy to remove DIN compounds via UV irradiation was proposed with the eventual use of solar light. Full article

Stabilization of condensate is a highly energy-consuming process compared to other oil and gas processes. There is a need to reduce this energy consumption. Therefore, the present work aims to simulate the stabilization unit in terms of available energy and on-spec stabilized condensate products. Natural gas condensate liquids (NGL) need to be stabilized by eliminating lighter hydrocarbon gases and acid gases before being sent to the refinery. Stabilized NGL has the vapor pressure determined as a Reid vapor pressure of 7 psia, showing that light components did not evolve as a separate gas phase. Stabilization and CO₂ removal was performed through the distillation method by heating and pressure reduction using steady state and dynamic simulation through Aspen HYSYS. Different process alterations around the exchanger and column have been studied based on the utilities available for the stabilization and CO₂ removal process. Sensitivity studies, including the impact of CO₂ concentration, the temperature at the inlet of the stabilizer flash separator, and the dynamic simulation for the PID controller, have been performed to analyze the impact on the process parameters, such as Reid vapor pressure (RVP) and CO₂ of the rundown air cooler and heat duties of the exchangers. Actual plant data have been used for the validation of process simulation values for the accuracy of the condensate stabilization unit model. Based on the scenarios analyzed, it can be concluded that the nitrogen stripping method achieved 7 ppmv CO₂ and 7 psia RVP in the condensate from the cooler outlet, while a variation of 29 bpd was observed for the stabilized condensate flowrate throughout all scenarios with data validation showing 0.24% discrepancy between Aspen Hysys data and actual plant data. Full article

Methylene blue (MB) is a hazardous chemical that is widely found in wastewater, and its removal is critical. One of the most common methods to remove MB is adsorption. To enhance the adsorption process, magnetic adsorbents, particularly those based on superparamagnetic iron oxide nanoparticles (SPION), play a vital role. This study focuses on comparing recent novel SPION-based MB adsorbents and how to acquire the critical parameters needed to evaluate the adsorption and desorption mechanisms, including isotherms, kinetics, and thermodynamic properties. Moreover, the review article also discusses the future aspects of these adsorbents. Full article

In this work, a safety assessment was carried out for the suspension polymerization method, known for the lack of studies about its sustainable performance and long history of chemical accidents. Therefore, a safety analysis was conducted using the inherent safety methodology to assess and determine the inherent risks of the poly(vinyl chloride) (PVC) suspension production process using computer-aided process engineering (CAPE). The indicators were calculated using data from safety databases and the specialized literature, considering downstream stages like vinyl chloride monomer (VCM) recovery, PVC purification and PVC drying. The obtained indicators revealed that the process has a negative performance regarding inherent safety, with a total inherent safety index of 30. The chemical inherent safety index had a value of 19, with the main chemical risk of the process being presented by the vinyl chloride monomer (with a value of 11), along with the risk of the exothermic reactions. The process safety index had a value of 15, highlighting the inventory as the primary concern of the process (with a value of 5), followed by the presence of unsafe equipment such as furnaces, burners, and dryers. The safety structure index had a score of 3, categorizing the process as probably risky, with the reaction and purification stages being more susceptible to accidents. Lastly, it is recommended to reduce the size of the process inventory and to substitute out unsafe process units. Full article

The availability of fossil energy is dwindling, so renewable fuels are the alternative choices, one of which is bioethanol. To increase the purity of the ethanol produced via the fermentation process, activated carbon (AC) was made from durian (Durio zibethinus) peel. The steps for making AC consist of carbonization (300 °C and 400 °C), chemical activation using phosphoric acid (10–40%), pyrolysis (700 °C and 800 °C), and neutralization. The results showed that the maximum surface area (326.72 m²/g) was obtained from 400 °C carbonization, 800 °C pyrolysis, and activation using a 40% phosphoric acid solution. Other characteristics are the surface area of 326.72 m²/g, pore radius of 1.04 nm, and total pore volume of 0.17 cc/g with phosphate residue in the form a P₂O₅ molecule of 3.47% by weight, with COOH, OH, CO, C=C, C=O, P-OC, and Fe-O groups with wavenumbers (cm⁻¹), respectively, of 3836, 3225, 2103, 1555, 1143, and 494. The AC also demonstrated the highest number of carbon (86.41%) upon detection using EDX, while XRF analysis verified an average carbon content of 94.45 wt%. The highest ethanol adsorption efficiency (%) and the lowest yield (%) of AC (%) were 90.01 ± 0.00 and 23.26 ± 0.01. This study shows that durian peel has great potential as the raw material for the activated carbon manufacture of ethanol adsorbents. Full article

The dynamics of a quadruple tank system (QTS) represent an extensive class of multivariate nonlinear uncertain systems found in the industry. It has been established that changes in split fractions affect the transmission zero location, thereby altering the operating conditions between the minimum and non-minimum phase regions. The latter is difficult to control as more fluid flows into the two upper tanks than into the two bottom tanks, resulting in competing effects between the initial and final system responses. This attribute, alongside nonlinearity, uncertainties, constraints, and a multivariate nature, can degrade closed-loop system performance, leading to instability. In this study, we addressed the aforementioned challenges by designing controllers for the regulation of the water flow in the two bottom tanks of the QTS. For comparative analysis, three controller algorithms—a nonlinear model predictive controller (NMPC), NMPC augmented with an extended Kalman filter (i.e., NMPC-EKF) and linear model predictive controller (LMPC)—were considered in the analysis and design of the control mechanism for the quadruple water level system in a non-minimum phase condition via the Matrix Laboratory (MATLAB) simulation package environment. The simulated and real-time results in the closed loop were analyzed, and the controller performances were considered based on faster setpoint responses, less oscillation, settling time, overshoot, and smaller integral absolute error (IAE) and integral square error (ISE) under various operational conditions. The study showed that the NMPC, when augmented with an EKF, is effective for the control of a QTS in the non-minimum phase and could be designed for more complex, nonlinear, and multivariable dynamics systems, even in the presence of constraints. Full article

This work presents the electrochemical degradation of the herbicide Diuron by anodic oxidation on a Ti/Ru_0.3Ti_0.7O₂ metal mixed oxide anode using sulfate as the electrolyte. The study includes the influence of Diuron concentration and current density on anodic oxidation. The results evidence a first-order degradation, with the highest capacity achieved at 40 mA cm⁻² and at an initial Diuron concentration of 38 mg L⁻¹. Nevertheless, in terms of efficiency and energy demand, the operation at 10 mA cm⁻² is favored due to the more efficient and less energy-consuming condition. To discern the optimum design and operation conditions, this work presents the results of a preliminary technical–economic analysis, demonstrating that, to minimize the total costs of the system, it is recommended to seek the most efficient conditions, i.e., the conditions demanding the lowest applied charges with the highest Diuron degradation. At the same time, attention must be given to the required cell voltage to not increase excessively the operating costs. Full article

The examination presented herein sought to establish a novel methodology for the efficient recovery of polyphenolic antioxidants from coffee processing residues, namely coffee silverskin (CSS). The process developed was an ethanol-based organosolv treatment, assisted by acid catalysis, using sulfuric acid or oxalic acid as the catalyst. The first approach was modeling treatment based on severity, where it was found that treatment dependence on time and temperature may well be described by linear relationships. Response surface methodology was then deployed as a consecutive stage, to optimize treatments with regard to catalyst concentration and resident time. In this case, again, linear models could effectively predict polyphenol recovery yield (Y_TP). For the sulfuric-acid-catalyzed treatment, the maximum theoretic Y_TP was found to be 10.95 ± 0.44 mg caffeic acid equivalent (CAE) g⁻¹ DM, achieved at C_SuAc = 1.5% and t = 300 min. On the other hand, the maximum Y_TP of 10.30 ± 0.53 could be attained at C_OxAc = 4%, and t = 300 min. Considering treatment severity, it was concluded that the use of oxalic acid, a food-grade organic acid, instead of sulfuric acid, a corrosive acid, would afford equivalent effects at lower severity. The high-performance liquid chromatography analyses also revealed that the extract produced through the oxalic-acid-catalyzed treatment was more enriched in neochlorogenic and chlorogenic acids, and it exhibited stronger antiradical activity, but weaker ferric-reducing effects. It is proposed that the methodology developed may contribute towards the use of coffee processing wastes as potential sources of bioactive ingredients and the design of novel functional products, in the frame of a more sustainable strategy for coffee processing companies. Full article

This study revealed an increased reactivity of centrifugally thermoactivated products of gibbsite toward aqueous solutions of nickel nitrate at room temperature as well as under hydrothermal conditions. X-ray, thermal, microscopy, adsorption and chemical analysis methods were used to investigate and demonstrate the possibility of obtaining highly loaded mixed aluminum–nickel oxide systems, with a nickel content of ca. 33 wt.%, using a hydrochemical treatment at room temperature or a hydrothermal treatment of suspensions of the product of the centrifugal thermal activation of gibbsite in aqueous solutions of nickel nitrate. It was shown that the thermal treatment of xerogels—hydrochemical interaction products—in the range of 350–850 °C led to the formation of NiO phases and highly dispersed solid solutions of nickel based on the NiAl₂O₄ spinel structure, with different ratios and a high specific surface area of 140–200 m²/g. A hydrochemical treatment of suspensions at room temperature ensures that the predominant formation of the NiO phase is distributed over the surface of the alumina matrix after calcination, whereas hydrothermal treatment at 150 °C leads to a deeper interaction of the suspension components at the treatment step, which occurs after the thermal treatment of the formed xerogel in the predominant formation of poorly crystallized NiAl₂O₄ spinel (“protospinel”). The considered method makes it possible to obtain complex aluminum–nickel oxide systems with different phase ratios, decreases the number of initial reagents and synthesis steps, completely excludes waste and diminishes the total amount of nitrates by 75 wt.% compared to the classical nitrate scheme for the coprecipitation of compounds with a similar elemental composition. Full article

The viscosity models for concentrated suspensions of unimodal hard spheres published in the twenty-first century are reviewed, compared, and evaluated using a large pool of available experimental data. The Pal viscosity model for unimodal suspensions is the best available model in that the predictions of this model agree very well with the low (zero)-shear experimental relative viscosity data for coarse suspensions, nanosuspensions, and coarse suspensions thickened by starch nanoparticles. The average percentage error in model predictions is less than 6.5%. Finally, the viscous behavior of concentrated multimodal suspensions is simulated using the Pal model for unimodal suspensions. Full article

Sacha inchi oil (SIO) extraction has been extensively studied using various oil extraction techniques to achieve a high oil recovery. However, most studies relied on heat-based methods, which led to compromised oil quality and reduced nutritional values, particularly polyunsaturated fatty acids (omega-3 and omega-6), vitamin E, and phenolic compounds. To address these concerns, this study employed a hydraulic cold-pressed extraction (HCPE) technique for extracting SIO aiming to enhance oil yield while preserving its nutritional integrity. During the HCPE process of sacha inchi seeds (SIS), conducted at a constant temperature of 25 ± 1 °C, pressures and pressing times were varied within the range of 30–50 MPa and 10–30 min, respectively, to determine their impact on SIO yields. The results revealed that both pressure and pressing time significantly influenced the yields of SIO (p < 0.05), with the highest oil recovery of 86.31 wt.% on a wet basis achieved at 50 MPa for 30 min. Regarding physicochemical properties, the peroxide values (5.71–9.07 meq/kg), iodine values (176.22–197.76 g I₂/100 g), acid values (1.82–2.16 mg KOH/g), and percentage of free fatty acids (0.91–1.08 wt.% as oleic acid) were found to be influenced by pressure and pressing time (p < 0.05). Additionally, the color variation by L* (34.22–35.17), −a* (0.39–0.81), and b* (3.48–5.62) changed with each oil yield. Notably, the high iodine value in SIO indicated a substantial content of polyunsaturated fatty acids, including omega-3 (40.86%), omega-6 (40.87%), and omega-9 (10.20%). Furthermore, a comparison with solvent extraction methods demonstrated that HCPE exhibited similar efficiency in extracting SIO, offering additional advantage in terms of its cold-pressed condition, eliminating of solvent use, simplicity, short extraction time, and higher oil recovery. Full article

For an in-depth investigation of the separation process in small-scale distillation columns, knowledge about the exact vapor load inside the column is highly important. However, since columns with small diameters have a comparatively high surface-to-volume ratio, heat losses have a significant impact on fluid dynamics, as they lead to unwanted condensation, and thus, to changes in the internal flows. This work presents a procedure used to measure heat losses in a 9.6 m high distillation column with three partially parallel segments (multiple dividing wall column). The evaporator is made of stainless steel, and the column walls are made of double-walled, evacuated, mirrored glass, and additionally, these can be heated. It is found that significant amounts of heat are lost in the evaporator. Throughout the column height, around 0.8 kW are additionally lost, even with external wall heating. To determine the main reason for this significant loss, thermal images are taken, indicating that the problem mainly arises because of the flanges. Based on this, it can be concluded that proper insulation and additional heating jackets for the column walls are highly recommended for small-scale distillation columns in order to increase their thermal efficiency. Full article

This study aimed to evaluate the extraction of Corymbia citriodora (Hook.) K.D.Hill and L.A.S.Johnson essential oil by steam distillation under reduced pressure. Yield and composition of the essential oils obtained at different system pressures were analyzed. System pressure had a significant influence on essential oil yield, resulting in a reduction of 78.6% when the pressure was reduced from 690 Torr to 240 Torr. There were also changes in essential oil composition, with an increase in citronellol content (oxygenated monoterpene). However, the major compound (citronellal) remained at a high content in all tests. Regarding the extracted mass of the major compounds (citronellal, citronellol), there was a significant reduction for all when the system pressure was reduced. Although the reduction in the pressure of the system caused a reduction in oil yield, it was possible to carry out the steps of extraction and purification of the major compound simultaneously. Reduced pressure extraction may decrease process time, increasing its efficiency and reducing costs in the extraction of essential oils. Full article

Cosmetics have always been in demand across the globe among people of all age groups. In the modern cosmetic world, nanostructured materials have proven hugely advantageous in producing cosmeceuticals or ‘nano-cosmeceuticals’ and various beauty products. The application of nanostructured materials in cosmetic products possesses some challenges in terms of short- and long-term safety and environmental issues, despite their growing popularity. The nanostructured particles in cosmeceuticals provide a targeted route of administration due to their high penetrability, site selectivity, high effectiveness, prolonged activity, and drug encapsulation potential. However, standard methods for toxicity evaluation may not be relevant for cosmeceuticals, leading to the need for an alternative methodology. This review article compiles detailed descriptions of all significant aspects of nanostructured materials in the cosmetics industry, which include the synthesis and characterization of relevant nanostructured materials for cosmeceuticals, state-of-the-art practices, mechanisms for the synthesis of advanced materials, toxicological concerns in terms of health risks in humans, and environmental concerns. Also, a proposal for new approaches in terms of regulatory measures to mitigate these problems has been suggested. The primary focus of this article is to provide a comprehensive outlook on this subject area and contribute to the exploration of new prospects and emerging roles of nanostructured materials in the cosmetics industry. Full article

In the present investigation, response surface methodology (RSM) and machine learning (ML) are applied to the biodiesel production process via acid-catalyzed transesterification and esterification of triglyceride (TG). In order to optimize the production of biodiesel from used cooking oil (UCO) in a microwave reactor, these models are also compared. During the process, Box–Behnken design (BBD) and an artificial neural network (ANN) were used to evaluate the effect of the catalyst content (3.0–7.0 wt.%), methanol/UCO mole ratio (12:1–18:1), and irradiation time (5.0–9.0 min). The process conditions were adjusted and developed to predict the highest biodiesel yield using BBD with the RSM approach and an ANN model. With optimal process parameters of 4.94 wt.% catalyst content, 16.76:1 methanol/UCO mole ratio, and 8.13 min of irradiation time, a yield of approximately 98.62% was discovered. The coefficient of determination (R²) for the BBD model was found to be 0.9988, and the correlation coefficient (R) for the ANN model was found to be 0.9994. According to the findings, applying RSM and ANN models is advantageous when optimizing the biodiesel manufacturing process as well as making predictions about it. This renewable and environmentally friendly process has the potential to provide a sustainable route for the synthesis of high-quality biodiesel from waste oil with a low cost and high acid value. Full article