Naveed Ramzan

The escalating energy crisis and environmental concerns associated with fossil fuel consumption have intensified the search for sustainable alternatives. This study reports the synthesis of a sulfonated heterogeneous catalyst derived from spent tea waste for biodiesel production via transesterification of waste cooking oil. The catalyst was prepared through sulfonation of spent tea waste with concentrated sulfuric acid and characterized using FT-IR, TGA, and XRF techniques. FT-IR analysis confirmed the successful grafting of sulfonic acid (-SO3H) functional groups onto the sulfonated carbonaceous framework, as evidenced by diagnostic S=O stretching bands at 1170 cm⁻¹ and 1030 cm⁻¹. XRF analysis revealed a substantial sulfur loading of 8.79 wt% in the sulfonated catalyst compared to 2.12 wt% in raw tea waste, while TGA demonstrated enhanced thermal stability of the catalyst up to 300 °C. The catalytic activity was systematically optimized through single-factor screening of reaction parameters. Under optimized conditions, 40 °C reaction temperature, 60 min reaction time, 2 wt% catalyst loading, and 12:1 methanol-to-oil molar ratio, a maximum biodiesel yield of 95.65% was achieved. The produced biodiesel exhibited favorable fuel properties, including a calorific value of 36.9 MJ kg⁻¹, cloud point of 11.8 °C, and pour point below 1.3 °C, all conforming to ASTM D6751 specifications. This study demonstrates that sulfonated spent tea waste is a promising, cost-effective, and environmentally benign catalyst for biodiesel production, offering a sustainable solution for valorizing tea waste while contributing to renewable energy development.

To use renewable energy and mitigate the greenhouse gas effect on the environment, carbon dioxide (CO₂) separation is crucial. Recent research has shown that using membranes for CO₂ separation is a vital option, but challenges remain with permeability and selectivity. Blend hollow fiber membranes offer a solution to these challenges. In this study, a blend of hollow fiber membranes made of polyether sulfone (PES) and polyvinyl acetate (PVAc) was developed, along with the incorporation of fillers, to overcome the permselectivity challenge. This resulted in the creation of mixed matrix blend hollow fiber membranes by using the phase inversion method. The membranes that were developed were examined using FESEM, FTIR, XRD, TGA, and pure-gas permeation analysis. The polymer blend demonstrated miscibility and preserved strong morphological and structural stability during CO₂ and CH₄ separation tests, exhibiting little deformation and reliable performance across different feed pressures ranging from 2 to 8 bar. The addition of TiO₂ improved the compatibility of the polymer blend and increased the mobility of CO₂. At 8 bar, the optimized PES/PVAc–5 wt.% TiO₂ hollow fiber membrane reached a CO₂ permeance of 92.22 GPU, representing an enhancement of about 24.7% in CO₂/CH₄ selectivity compared to the standard membrane. This emphasizes its potential for effective biogas upgrading under high pressure.

The purpose of this work was to consider the decolorization efficiency of reactive yellow 160 (Ry-160) dye utilizing cobalt aluminum oxide (AlCo₂O₄)-anchored Multi-Walled Carbon Nanotubes (AlCo₂O₄/MWCNTs) nanocomposites as catalysts for the first time in a photocatalytic process under natural sunlight irradiation. The compositional, morphological, and functional group analyses of AlCo₂O₄ and AlCo₂O₄/MWCNTs were performed by utilizing Energy Dispersive Spectroscopy (EDS), Field Emission Scanning Electron Microscopy (FE-SEM), and Fourier Transform Infrared (FTIR) Spectroscopy, respectively. A UV-Vis (UV-Vis) spectrophotometer was used to investigate degradation efficiency. The results exhibited a reduction in the optical bandgap for AlCo₂O₄/MWCNTs nanocomposites as catalysts from 1.5 to 1.3 eV compared with pure spinel AlCo₂O₄ nanocomposites. AlCo₂O₄/MWCNTs nanocomposites showed excellent photocatalytic behavior, and around 96% degradation of Ry-160 dye was observed in just 20 min under natural sunlight, showing first-order kinetics with rate constant of 0.151 min⁻¹. The results exhibited outstanding stability and reusability for AlCo₂O₄/MWCNTs by maintaining more than 90% photocatalytic efficiency even after seven successive operational cycles. The betterment of the photocatalytic behavior of AlCo₂O₄/MWCNTs nanocomposites as compared to AlCo₂O₄ nanocomposites owes to the first-rate storage capacity of electrons in MWCNTs, due to which the catalyst became an excellent electron acceptor. Furthermore, the permeable structure of MWCNTs results in a greater surface area leading to the onset of more active sites, and, in turn, it also boosts conductivity and reduces the formation of agglomerates on the surface of catalysts, which inhibits e−/h⁺ pair recombination. Concisely, the synthesis of a novel AlCo₂O₄/MWCNTs catalyst with excellent and fast photocatalytic activity was the aim of this study.

The integration of optimization techniques and deep learning models, which offer a promising avenue for improving the efficiency and sustainability of biodiesel production processes from baobab seed oil (BSO), is rare. This study utilized a multi-input-multioutput (MIMO) deep learning technique and the most recent central composite design (CCD) optimization tool to model and optimize the yield and properties of biodiesel produced from BSO. First, the baobab seed oil was extracted using a solvent extraction method. BSO was subsequently analyzed and converted to biodiesel by reacting CH₃OH catalyzed by waste banana bunch stalk biochar activated by KOH. Multiobjective optimization and prediction of the biodiesel yield (Y) and several key fuel properties, including the cetane number (CN), kinematic viscosity (VS), and purity (P), were achieved. With better correlation coefficients of 0.9709, 0.9464, and 0.9714 for response training, response testing, and response validation, respectively, and a root-mean-square error of 0.00755, the MIMO model on the logsig transfer function accurately predicted the biodiesel yield and properties more than did the MISO and response surface methodology models. The optimum Y (96 wt %), CN (48), VS (3.3 mm²/s), and P (98.3%) were concurrently accomplished at a reaction temperature of 56 °C, a reaction time of 115 min, a CH₃OH/BSO molar ratio of 15:1, a catalyst dosage of 6 wt %, and a stirring speed of 400 rpm with 98% optimal validation accuracy. CCD sensitivity analysis revealed that the CH₃OH/BSO ratio was the most sensitive (50.9%) input predictor among the other input variables studied.

Doping with heteroatoms is the main method used to enhance energy storage with carbon materials, and polyatomic doping is one of the main challenges. Hydrothermal carbonization of cellulose was performed at 240 °C for 1 h. Ammonium sulfate and thiourea dopants were selected as the sources of inorganic nitrogen and organic nitrogen in the preparation of supercapacitor carbon. The effects of boric acid on the properties of the resulting hydrochar after KOH activation were examined. The results showed that the proportion of functional groups and the specific surface area of the activated hydrochar were reduced by the addition of boric acid, and the formation of micropores was inhibited. The hydrochar obtained from the reaction of cellulose and organic nitrogen compounds had a better pore size distribution and electrochemical properties after activation. The largest specific surface area (952.27 m²/g) was obtained when thiourea was used as the sole dopant. In a three-electrode system, the specific capacitance of the activated hydrochar reached 235.8 F/g at a current density of 1 A/g. After 20,000 charging and discharging cycles at a current density of 10 A/g, the capacitance retention rate was 99.96%. Therefore, this study showed that supercapacitor carbon with good electrochemical properties was obtained by the direct reactions of cellulose with organic nitrogen compounds.

This study aims to investigate the treatment of real textile wastewater using a novel bentonite clay/TiO₂/ZnO-based ozonation catalyst. In this study, synergic electroflocculation/catalytic ozonation, catalytic ozonation, and ozonation processes are applied in a modified hybrid reactor. To the authors’ knowledge, this is the first application of bentonite clay/TiO₂/ZnO as an ozonation catalyst for treating real textile wastewater. The four operational variables—ozone dose (0.2–0.8 mg/min), reaction time (0–120 min), DC voltage supply (5–15 V), and catalyst dose (0.5–2 g/L)—were studied for decolorization and for the removal of chemical oxygen demand (COD). The results showed that the combined process (electroflocculation + clay/TiO₂/ZnO/O₃) had the highest removal efficiencies for COD and color (97.86% and 97.90%, respectively) at optimum parameters of 10 DC volts. an ozone dose of 0.8 mg/min, and a catalyst dose of 2 g/L in textile wastewater. The results further revealed that the initial pH of wastewater plays an essential role in the process’s overall performance. The studied synergic process was efficient for real wastewater treatment under alkaline pH (6–9). Based on empirical work, we established that the synergic process is suitable for effectively treating textile wastewater.

Dyes are the most carcinogenic organic compounds that are discarded by most of the textile industries without any prior treatment, which is harmful for the environment. This study aims to develop a bentonite-clay/carbon-nanotube (CNT)-based adsorbent to treat textile wastewater for water sustainability. The preliminary and post-characterization of adsorbent involves scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) and energy-dispersive X-ray (EDX) analysis to determine the changes in surface morphology, functional group, and surface area of the adsorbent. Linear and nonlinear isotherms and kinetic studies were performed to explore the sorption mechanism. The results show that the nonlinear form of the Langmuir isotherm best fits adsorption with a qmax of 550 mg/g. The adsorption followed the nonlinear pseudo-first-order kinetics, favoring chemisorption with R² ≈ 1 and X₂ = 0.22. Maximum dye removal (89.9%) was achieved under the optimum conditions of pH 3, an adsorbent dose of 100 mg, and a contact time of 120 min, with an initial COD concentration of 1140 mgL⁻¹. This study has demonstrated the successful application of a bentonite-clay/CNT-based adsorbent on textile wastewater treatment.

Hydrothermal carbonization of cellulose was examined at 240 ℃ for 1 h. Ammonium sulfate and thiourea were selected as the doping sources of inorganic nitrogen and organic nitrogen for the preparation of supercapacitor carbon. The effect of boric acid on the properties of the resulting hydrochar after KOH activation was examined. The results showed that the proportion of functional groups and the specific surface area of the activated hydrochar would be reduced after the addition of boric acid, and the pore-forming process of the micropores would be inhibited. The hydrochar obtained from the reaction of cellulose and organic nitrogen compounds had better pore size distribution and electrochemical properties after activation. The largest specific surface area (952.27 m2 g-1) was obtained when only thiourea was used as the only doping source. In the three-electrode system, the specific capacitance resulting activated hydrochar reached 236.25 F g-1 at a current density of 1 A g-1. After 20,000 cycles of charging and discharging at a current density of 10 A g-1, the capacitance retention rate reached 99.96%. Therefore, this study proves that the supercapacitor carbon with good electrochemical properties could be obtained by the direct reaction of cellulose with organic nitrogen compounds.