Sustainable Chemical Engineering

Sustainable Removal of Methyl Violet from Aqueous Solution Using Banana Peel Extract-Modified Magnetite Adsorbent

Addina Husna Fillah — 2025-10-15

The textile industry generates large volumes of dye-containing effluents, with Methyl Violet (MV) among the most toxic and persistent pollutants due to its carcinogenicity and resistance to degradation. In this study, a green adsorbent based on magnetite (Fe₃O₄) modified with Banana Peel (BP) extract was synthesized via reverse co-precipitation, where BP functions simultaneously as a natural reducing, stabilizing, and surface-functionalizing agent. Structural characterization using X-Ray Diffraction (XRD) and Fourier-Transform Infrared (FTIR) spectroscopy confirmed the crystalline spinel structure of Fe₃O₄ and the incorporation of organic functional groups (-OH, C=O) from BP onto its surface. Adsorption experiments demonstrated a maximum capacity of 135 mg·g^-1 for MV at pH 6.0, with data fitting well to the Langmuir isotherm model, indicating monolayer adsorption. Furthermore, Fe₃O₄-BP achieved over 95% MV removal in simulated wastewater and could be magnetically separated and reused. These findings emphasize the dual role of agricultural waste as both a sustainable reagent in nanoparticle synthesis and as a performance enhancer for adsorption, underscoring the potential of Fe₃O₄-BP as a cost-effective and eco-friendly material for wastewater treatment.

Eco-Friendly Synthesis of Silver Nanoparticles Using Brown Sugar and Their Potential to Inhibit the Growth of Escherichia Coli

David Omar Oseguera-Galindo — 2025-11-04

Silver Nanoparticles (AgNPs) were synthesized in a brown sugar solution at three different temperatures (23 °C, 40 °C and 60 °C) with a concentration of 2.5 mM of AgNO₃ and 0.02 g·mL^-1 of brown sugar. The sample prepared at 60 °C exhibited the highest nanoparticle yield, with an average diameter of 22 nm, as determined by analyses of micrographs. The bactericidal effect of these nanoparticles was evaluated against Escherichia coli American Type Culture Collection (ATCC) 25922 using the microdilution method, monitoring bacterial growth via absorbance at 600 nm. After 24 hours, nanoparticles formed at 60 °C demonstrated a significant inhibitory effect on E. coli growth when used at volumes of 300 µL and 400 µL in the assay.

Performance Evaluation of a Repurposed LPG Gas Cylinder as a Compact Household Anaerobic Digester

Abubakar R. A. — 2025-11-06

Access to clean and affordable household energy remains a pressing challenge in many low-income regions, where dependence on firewood and fossil fuels contributes to deforestation, indoor air pollution, and greenhouse gas emissions. Biogas technology offers a renewable and decentralized alternative, yet the affordability, durability, and safety of small-scale digesters remain barriers to widespread adoption. This study presents the design, construction, and performance evaluation of a small-scale biogas digester repurposed from a decommissioned 50 L Liquefied Petroleum Gas (LPG) steel cylinder. The conceptual design incorporated an airtight slurry inlet, digestate outlet, and gas outlet fitted with a pressure relief valve, non-return valve, and gas purification system (moisture trap and H₂S scrubber). To enhance durability, the interior was coated with food-grade epoxy resin, and the vessel was insulated with polyurethane foam to maintain mesophilic conditions (30-40 °C). Engineering analyses guided reactor volume sizing, retention time (20-30 days), biogas production estimation, thermal insulation design, and pressure safety limits. The construction process emphasized leak prevention and corrosion resistance, while experimental testing was conducted over 30 days using cow dung and kitchen waste at a 1 : 1 feedstock-to-water ratio. Daily monitoring recorded slurry temperature, biogas yield, and methane concentration. Results showed cumulative biogas production of 268.6 L (0.537 m³·kg⁻¹ Volatile Solids (VS)) and methane yield of 163.3 L (0.327 m³·kg⁻¹ VS), corresponding to an energy output of ~11.7 MJ·kg⁻¹ VS (3.25 kWh·kg⁻¹ VS). Methane concentration increased steadily from 54% to 66% during the first 15 days, stabilizing thereafter before declining in the final phase due to substrate depletion. Statistical analysis indicated a positive correlation between slurry temperature and daily gas yield, confirming the importance of thermal regulation. The findings demonstrate that repurposed gas cylinders can provide a low-cost, portable, and pressure-rated solution for decentralized biogas production.

Effect of Substrate on Active Material and Dynamic Performance Enhancement in Supercapacitor Devices Based on Graphite-Clay Composite Electrodes

Pannilage M. H. Madhushanka — 2025-11-06

Graphite-clay composite electrodes are promising candidates for fabricating energy storage devices with Polyaniline (PANI) as the active material. Well-performing homogeneous symmetric supercapacitors made from graphite-clay electrodes open a new pathway to construct heterogeneous symmetric supercapacitors, providing a novel technological perspective on supercapacitors. The present study demonstrates the fabrication of three different supercapacitors, including a PANI-coated graphite-Montmorillonite (MMT) composite electrode and graphite-kaolinite-cement composite electrode-based supercapacitor (PANI-GMMTCE_GKCeCE), a PANI-coated graphite-MMT-cement composite electrode and graphite-kaolinite-cement composite electrode-based supercapacitor (PANI-GMMTCeCE_GKCeCE), and a PANI-coated graphite-kaolinite composite electrode and graphite-kaolinite-cement composite electrode-based supercapacitor (PANI-GKCE_GKCeCE), and their performance evaluation using various electrochemical and analytical techniques. Supercapacitors were constructed based on four different PANI-coated graphite-clay composite electrodes, each consisting of PANI-GKCeCE, with the remaining section from each of the other electrodes. Each electrode surface facilitated the formation of conductive PANI coating via aniline electropolymerization, as evidenced by well-characteristic Cyclic Voltammograms (CV) with dominant peaks. The morphological structures of PANI coating on each electrode are unique from one another, but all have a PANI nanofiber network with uniform or irregular distribution. Synergistic interactions of two different PANI networks in a supercapacitor contribute to the charge transfer and storage mechanisms. Both (PANI-GMMTCE_GKCeCE) and (PANI-GMMTCeCE_GKCeCE) supercapacitors outperformed in capacitance, producing more than 390 F·g^-1 of specific capacitance in CV and charge-discharge tests. All three supercapacitors follow pseudocapacitive behavior in charge-discharge as well as in CVs. However, each supercapacitor displayed combined properties of double-layer and pseudocapacitor, indicating a constant phase element in each impedance spectrum. The ionic diffusion process contributed to the charge transport and storage mechanism due to the heterogeneous nature on both sides, which is similar to previously fabricated PANI-coated graphite-clay-based supercapacitors. Charge-discharge curves of each supercapacitor exhibited cyclic stability with higher Coulombic efficiency, and all supercapacitors achieved considerably higher energy and power densities, indicating the high performance of heterogeneous symmetric graphite-clay-based supercapacitors. Further modifications of heterogeneous symmetric supercapacitors are essential to improve their performance for commercial-scale development.

Effect of Annealing on Structural, Optical, and Magnetic Properties of Zn_0.90Ni_0.10P₂ Nanoparticles

Nakka Praveenkumar — 2025-12-05

Zinc phosphide nanoparticles doped with Nickel (Zn_0.90Ni_0.10P₂) were created via a solid-state process and then vacuum-annealed at two distinct temperatures (573 K and 873 K) and pressures of 2 × 10^-2 mbar. The impact of different annealing conditions on the synthetic materials' optical, magnetic, and structural properties was examined. The produced samples clearly maintained a tetragonal structure, as shown by the X-Ray Diffraction (XRD) analysis, and the diffraction peaks show no observable signs of extra nickel or other impurities. As the annealing temperature was raised from 573 K to 873 K, the crystallite size increased from 31.597 nm to 32.019 nm, and the lattice parameters showed a positive correlation from a = 8.1096Å, c = 11.1098Å to a = 8.1722Å, c = 11.1286Å. According to the Energy-Dispersive X-ray Spectroscopy (EDS) analysis, the dopant concentration closely resembles the intended atomic ratio. As the annealing temperature was raised, the Zn_0.90Ni_0.10P₂ nanoparticles' optical band gap increased from 1.443 eV to 1.449 eV. The analysis of the Vibrating Sample Magnetometer (VSM) data shows that the annealing temperatures and saturation magnetization are positively correlated. The values of saturation magnetization, coercivity, and retentivity at 573 K and 873 K Zn_0.90Ni_0.10P₂ are 0.1499 emu/g, 69.52 Oe, 0.0039 emu/g,0.1676 emu/g, 65.46 Oe, and 0.0040 emu/g, respectively.

Influence of Carbon Chain Length of Silicates on Visible Light Transmittance and Infrared Light Transmittance of Photovoltaic Glass

Sun Guodong — 2025-11-19

To address Photovoltaic (PV) glass solar energy loss (reflection) and efficiency degradation induced by infrared light absorption (which causes increased battery temperature and thereby exacerbates carrier recombination), this study examines silicate precursors (Tetramethoxysilane (TMOS), Tetraethoxysilane (TEOS), Tetrabutoxysilane (TBOS)) with varying carbon chain lengths on coating performance. X-Ray Diffraction (XRD)/Scanning Electron Microscopy (SEM) characterization results show all coatings are amorphous, but TMOS yields higher crystallinity and denser microstructures; TEOS/TBOS form defective structures via longer chains. Optical tests indicate that all coatings have 90%-96% Visible Light (VL, 300-800 nm) transmittance (TMOS: up to 96%, with the least fluctuation); TMOS has the lowest infrared (IR, 2.5-25 μm) transmittance (~ 40%). In addition, TMOS coatings retain > 90% VL transmittance over 24 months, and TEOS and TBOS show shows ultra-low aging attenuation. These results demonstrate that TMOS is the optimal precursor for preparing high-performance PV glass coatings, which can effectively reduce solar energy loss and mitigate efficiency degradation of PV modules, providing technical support for the development of high-efficiency photovoltaic systems.