Band 22, Heft 10

The dye-contaminated industrial effluent causes serious health issues when it gets mixed with underground water without primary treatment. The current project was designed to treat reactive blue-19 dye aqueous solutions in the presence of hydrogen peroxide (H 2 O 2 ) and titanium dioxide (TiO 2 ) under UV-LED light. The characterization of the photocatalyst was carried out via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) for structure, purity, and surface study. The effect of various factors such as pH, TiO 2 dose, UV-LED light exposure time, H 2 O 2 , and dye concentration, on the degradation rate and cytotoxicity reduction was evaluated and optimized through the Response Surface Methodology (RSM). The maximum degradation of dye solution and chemical oxygen demand (COD) reduction was achieved at 98.81  and 86.22 %, respectively for 50 ppm solution, using UV-LED/H 2 O 2 (3 %)/TiO 2 (6  g/L) hybrid process. The toxicity evaluation through the Allium cepa test demonstrated a 62.40, 65.2, and 56.97 % increase in root length (RL), root count (RC), and mitotic index (MI), respectively, following treatment with the UV-LED/H₂O₂/TiO₂ combined process for 150 min. The hemolytic and brine shrimp tests revealed a reduction in toxicity up to 92.18  and 84.08 %, respectively, after applying the same treatment. Additionally, the Ames test indicated up to 80.94 % reduction in mutagenicity for TA98 and an 84.04 % reduction for TA100 strain when dye samples were treated with UV-LED light in the presence of H₂O₂ and TiO₂ for 150 min. The findings suggested that UV-LED light in conjunction with H 2 O 2 and TiO 2 can be a useful tool for the degradation and detoxification of toxic pollutants found in textile wastewater.

This laboratory-scale study investigated the removal of Malachite Green (MG) dye using the goethite composite (α-FeOOH) (GOE). In the dark, an interaction between MG and GOE, attributed to physical adsorption, was observed, reaching 28 % after 4 h and confirmed by FTIR analysis. The addition of hydrogen peroxide (H 2 O 2 ) enhanced the thermal process in the MG-GOE system. By varying parameters such as pH, GOE concentration, and H 2 O 2 amount, the MG disappearance rate increased with higher GOE and H 2 O 2 concentrations. Alkaline pH favored dye removal. Under UV light (365 nm), GOE effectively degraded MG, especially at pH 9 (97 % degradation in 180 min). The scavenging of hydroxyl radicals (˙OH) by tert-butanol in the GOE-MG-UV 365nm system indicated ˙OH-dominated degradation. Fe(II) formation monitoring supported this result. Additionally, H 2 O 2 addition significantly enhanced photodegradation. Partial mineralization of dye molecules was observed via Total Organic Carbon (TOC) analysis. The kinetics of MG degradation followed pseudo-first order behavior. Overall, this promising process holds potential for recalcitrant environmental pollutant removal.

In order to enhance the efficiency of diphenyldimethoxysilane preparation in microreactors, this study utilized the computational fluid dynamics simulation based on the finite element method to explore the impact of the internal structural parameters of the spiral two-step microreactor (STMR) on the reaction outcomes, with the aim of optimizing its structure for high-performance catalytic reactions. By designing a microreactor based on the Archimedean spiral shape and introducing two ribbed obstacles, the structure was optimized through adjusting the relevant ratios. The effects of different-sized structures and obstacles within the reaction zone and non-reaction zone on the product concentration and reaction results were discussed. The results demonstrate that lower obstacle heights and smaller aspect ratios ( P  = 2:7, R  = 5:6) are beneficial for improving the reaction efficiency and product concentration. This study offers a theoretical foundation for microreactor design and is anticipated to further drive the development of microreactor technology.

The residual manganese concentration from groundwater treatment plants normally exceeds the limit of 0.1 mg L −1 , which is the maximum permissible manganese content set by the Ministry of Health. A new biological activated carbon fiber technology is described in this paper, in which filtration columns filled with ACF and inoculated manganese oxidizing bacteria ( Citrobacter sp. FM-2) were used in an attempt to effectively remove the Mn 2+ in groundwater using a biological method. By researching the various factors that influence biological manganese removal, a new kinetics model of BACF filtering with multiple influencing factors that incorporates the key factors of the process, such as the temperature, pH and empty bed contact time (EBCT), was established, and the accuracy of the model was verified. The study further extends the research on biological manganese removal and provides a reference and basis for production practice to some extent.

This study investigated the most influential composting parameters (temperature, pH, humidity, C/N ratio, and CO 2 emissions) on final compost quality. Composting bags (turned daily) containing prunings, lignocellulose material, cattle manure, and household organic waste were monitored for eight weeks across three batches. All the temperature data registered daily were statistically analyzed with one-way ANOVA to verify the consistency between batches. This study employs a first-order kinetic model to quantify the decomposition of organic matter in composting, revealing the influence of temperature on the decomposition rate. Principal component analysis was conducted for these factors and their interactions with respect to the final compost quality. Finished compost showed a significantly high nitrogen, phosphorus, and potassium content compared with that in the feedstock of the initial compost mixture, while there was constant organic carbon content. In addition to the control of key parameters, a linear regression analysis allowed us to identify the factors that most influenced temperature. We identified two key models: one including pH, humidity, C/N ratio, and CO 2 emissions, and another focusing only on CO 2 . This study emphasized the importance of monitoring and controlling the crucial parameters of the composting process in order to obtain quality compost suitable for application in soil use. Moreover, high temperatures possibly attained in the process of aerobic decomposition destroy the pathogens, making the end products safer for uses in agriculture.

The residence time distribution (RTD) has an important impact in the performance of chemical reacting systems. The segregated fluid assumption is commonly used to assess the analysis and design of chemical reactors. Models derived from the segregated fluid assumption for continuously stirred tank reactors (CSTR) rely on batch reactor models. A drawback of such assumption is that the CSTR model structure is not recovered in the limit when the RTD becomes very narrow (e.g., a Dirac delta). The aim of the present work is to propose a nonlocal modeling approach that is consistent with the CSTR model structure. The main idea is to represent the reactor as a continuum of tiny differential CSTRs determined by the RTD. The resulting nonlocal model is expressed as integrodifferential equations representing the interaction of reactive molecules of a given residence time with molecules of all residence times. By doing this, the nonlocal model is reduced to the usual CSTR model in the limit when the RTD is very narrow. The methodology was illustrated with three worked cases of dimerization, autocatalytic and series reaction schemes, and the results were compared with that obtained with the segregated fluid assumption. It was found that nonlocal models predict lower conversions than the segregated fluid models.

The tribological characteristics of biodiesel blends containing corn oil and nanoparticles of copper oxide and titanium dioxide were examined in this study. The prepared biodiesel blends along with nanopowders are blended with 20W-40 lubricant. The aim was to explore the potential of these blends as lubricants in various mechanical systems. A pin-on-disk equipment was used to perform the tribological tests under different stresses. The optimal outcomes were achieved with the incorporation of 100 ppm CuO with BD20, which reduced the coefficient of friction by as much as 80 % and decreased the wear rate by up to 75 % in comparison to pure biodiesel. There is also a decrease in frictional force for the sample BD20 with 100 ppm CuO and pin temperature was minimum for the sample BD20. The results indicate the viability of using corn oil biodiesel mixtures containing CuO and TiO 2 nanoparticles as eco-friendly lubricants in diverse industrial applications.

A maximum sensitivity constrained modified Smith predictor consisting of two PD controllers is developed for integrating type continuously stirred tank reactors (CSTRs) model. This CSTR type model approximated as integrating first order plus time delay with and without inverse response processes is challenging to control as it contains integrating term, process time delay and a zero lying in the right half of s-plane. The inner and outer loop PD blocks are tuned to achieve the desired set-point tracking and load disturbance rejection responses using direct synthesis approach. The proposed control is free from integrating action and therefore, smooth setpoint tracking response with no overshoot is obtained which is highly desirable in the process industries. Two design parameters λ and τ are involved in the suggested control whose suitable values are recommended to achieve the desired robustness level by specifying the maximum sensitivities of the inner and outer loop transfer functions. Various illustrative models are considered to show the effectiveness and superiority of the proposed control structure. The system robustness towards process parameter perturbations and load disturbances are investigated in all the examples. Performance of the suggested modified Smith predictor is found superior as compared to the other recently published works.

Water contamination is increasing drastically today, and the government consistently works to reduce water pollution. This paper focuses on desalinating saline water using a capacitive deionization technique using activated carbon electrodes and ion exchange resin membranes. The developed model of the capacitive deionization cell works within 1.2 V, and the potential difference between the electrodes is varied within the threshold voltage of water. The concentrations of magnesium, sodium, and chlorine are measured in this investigation. The performance of the system was analyzed with a varied concentration of resin ion exchange membrane and various potential differences. The behavior of the capacitance deionization cell and rate with the conductance of water-electrolyte was studied. After the removal of ions, the conductivity of the electrolyte was reduced. Ion exchange resins are utilized to increase the electrical conductivity, which leads to an increase in the deionization rate. The ion exchange is carried out through the activated porous carbon electrodes. The experiment was carried out with varied voltages in saline streams, and the concentration of ions was evaluated. Due to the migration of positive and negative ions to the respective electrodes. The portable desalination model of efficient desalination level is derived. The energy and performance efficiencies are taken into consideration to evaluate the developed model. The cost of deionization is reduced compared with the reverse osmosis process. The deionization rate is high, leading to the production of a vast quantity of conditioned water for irrigation purposes. The study demonstrated that capacitive deionization (CDI) with activated carbon electrodes and ion exchange resin membranes effectively removes ions like magnesium, sodium, and chlorine, reducing water conductivity. Operating efficiently within a low-voltage range, the CDI system showed a high deionization rate suitable for large-scale applications, with lower costs than traditional reverse osmosis.

Investigating thermodynamic and kinetic aspects is crucial for assessing efficiency of converting biomass into energy. This study presents kinetic and thermodynamic characteristics of maize stalk using thermogravimetric analysis. The novelty of this research stems from the combination of kinetic and thermodynamic analysis, the application of multiple kinetic models and understanding of pyrolysis-based bioenergy production process from maize stalk. Analysis was performed using a temperature range of 25–650 °C employing 5, 10, 15 and 20 °C/min heating rate. The temperature range of 250–650 °C was selected to analyze the complete decomposition of the three main components of maize stalk i.e. hemicellulose, cellulose and lignin and to prevent the decomposition of inorganic substances such as CaCO 3 which decompose at high temperature. The apparent activation energy values were evaluated using Kissinger-Akahira-Sunose (KAS), Friedman and Ozawa-Flynn-Wall (OFW) models. The resulting mean apparent E a values calculated for KAS, Friedman and OFW were 167.86, 177.34 and 162.96 kJ/mol, accordingly. Additionally, Gibbs free energy (ΔG) values were 164.17 kJ/mol, enthalpy (ΔH) −178.31 J/molK and entropy (ΔS) 285.59 kJ/mol, respectively. These findings suggest that maize stalk holds promise as a potential bioenergy source, aligning with sustainable goals and waste-to-energy strategies.