Engineering Chemistry Vol. 11

Abstract: Marine oil spills negatively impact human health and aquatic ecosystems, causing biodiversity loss and reduce water quality. A range of mechanical, chemical, and biological methods have been employed to address oil spills in marine environments. As science and technology advance, there is a high demand for affordable and effective oil-absorbing materials. Oil absorbers using sponges with solar heat can be a solution to overcome the problem of oil spills at low cost and can be recycled. In this study, we combined the sponge with carbon dots from graphite pencils to improve the sponge's ability to absorb oil. The electrochemical method successfully synthesized carbon dots with particle sizes ranging from 1 to 5 nm. UV-Vis absorption, photoluminescence intensity, and FTIR spectra have revealed transition energies, peak intensities, and functional groups characteristic of carbon dots, respectively. We used sponges with and without carbon dots to compare their performance in absorbing oils. In addition, we also compared sponge performance when exposed to temperatures of 60 to 65 °C. Sponges with carbon dots have high absorbency. The absorbency of the sponge increases by 28% when combined with a carbon dot. A higher temperature can also increase the absorbency of the sponge.

Abstract: Oil contamination from petroleum hydrocarbons and other sources poses significant environmental and health risks due to its persistence and toxicity. This study developed polyethylene-calcium carbonate (PE-CC) composites with tailored structural and surface properties to enhance oil adsorption. The composites were fabricated through melt blending (PE:CC = 40:60), with the calcium carbonate (CC) filler first modified using oleic acid (OA) (0, 0.5, and 1.5 wt.%) to improve hydrophobicity and dispersion, followed by citric acid (1 M) treatment of the composites to induce porosity and optimize oil adsorption. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed successful surface modification of CC, as evidenced by reduced diffraction peak intensities and the emergence of new functional groups at 2970 cm^-1 and 1395.12 cm^-1. Citric acid treatment led to partial CC dissolution, resulting in up to 8.96 % weight loss, as confirmed by XRD and energy-dispersive spectroscopy (EDS). Scanning electron microscopy (SEM) revealed increased porosity (up to 40 μm) and enhanced surface roughness, particularly in TE 3. Wettability analysis demonstrated a maximum contact angle of 160.80° following OA modification of CC, while oil adsorption tests of the PE-CC composites showed substantial improvements in oil uptake, with vegetable oil adsorption increasing from 5.21 % (NE) to 18.75 % (TE 3), and hexane and diesel reaching 18.4 % and 12.5 % respectively, in TE 3. Photoluminescence analysis revealed wavelength-dependent blue-violet emissions with broad peaks at 405 and 570 nm when excited at 255 and 405 nm, respectively, indicating potential optical applications. These findings show the potential of OA and citric acid modifications in enhancing the surface properties, photoluminescence, and adsorption efficiency of PE-CC composites, positioning them as promising candidates for oil remediation and multifunctional industrial applications.

Abstract: Methylene Blue (MB) waste is damaging to both humans and the environment. Chitosan is one of the MB adsorbents that may be made from green mussel shells. Because CS compounds have a limited adsorption capacity for MB, a restricted surface area, and poor chemical stability, thus necessitating modification. CS/XG was created by combining the three chemicals silica (SiO₂), tofu pulp, and the anionic substance Xanthan Gum (XG). SiO₂ hydrogel bio-composite with the aid of UV light, can absorb MB by photodegradation. The objective of this paper is to analyze the regeneration and photocatalysis kinetics based on the kinetic rate constant of the bio-composite photodegradation, and to identify the ideal circumstances of MB photodegradation by CS/XG.SiO₂ hydrogel bio-composite with Box-Behnken design. The CS/XG bio-composite was synthesized from chitosan (green mussel shell waste) and xanthan gum (tofu dregs waste) with added SiO₂ to adsorb methylene blue via photodegradation. The use of green mussel shells and tofu dregs is significant as it turns abundant waste into valuable materials, reducing pollution and supporting low-cost, eco-friendly wastewater treatment.The variables were pH, MB concentration, and photodegradation time. The results showed that the optimum condition occurred at pH 9.43; MB concentration 5.054 ppm; and irradiation time 119.67 minutes with % degradation of 94.2%. After the 5th reuse of CS/XG.SiO₂, the % degradation only decreased from 94.2% to 79.4%, indicating good regeneration ability. Analysis of photodegradation kinetics showed accurate modelling using the Modified Elovich model with an R² value of 0.9805 and a photodegradation kinetic rate constant of 0.0010 min^-1.

Abstract: Water pollution by heavy metals constitutes a significant environmental and health risk, necessitating efficient and reusable adsorbents. The current study investigates the application of inexpensive biopolymer chitosan to extract Ni²⁺ and Cd²⁺ ions from aqueous solutions. Material characterization using X-ray diffraction (XRD) showed the amorphous nature (absence of peak at 10°), and Brunauer-Emmett-Teller (BET) analysis exhibited the mesoporous surface area of 302.12 m²/g, suitable for the adsorption of metal ions. The Swan model was parameterized with batch-derived adsorption parameters (i.e., Qₘₐₓ = 220 mg/g for Ni²⁺, 226 mg/g for Cd²⁺) and successfully predicted packed-bed breakthrough curves at optimum pH (7 for Ni²⁺, 6 for Cd²⁺), with transport rates of 3.65 × 10^-11 m²/s (Ni²⁺) and 3.14 × 10^-11 m²⁺/s (Cd²⁺) for a 1.2 m column. The material retained over 95% removal efficiency after five regeneration cycles. These findings show the potential of chitosan for large-scale water treatment with high efficiency, model-driven design, and strong reusability.

Abstract: Biomass has recently become attractive as a feedstock for ‘green’ graphene oxide (GO) as it promotes an environmentally friendly route. Here, we report a novel approach in the synthesis of large-sized GO from biomass using a simple single pyrolysis step, followed by processing via a modified Tour method. The single pyrolysis process produces a thin carbon layer with amorphous character, which is then further exfoliated using the permanganate oxidation method in a mixture of hydrochloric acid and phosphoric acid at low temperature. The novelty of this research lies in the combination of an efficient biomass pyrolysis process with a customised chemical approach to produce high-quality GO sustainably. XRD, SEM-EDX, and FTIR analyses showed that the modified GO has a more regular structure, contains fewer secondary phases, and has lower non-carbon functionalities compared to the untreated large-sized GO. The obtained GO materials have potential applications in the fields of energy storage, sensors, and environmentally friendly composite materials.

Abstract: The composite nanofibers of PVDF/BiFeO₃ (PVDF/BF) signify a notable advancement in the domain of piezoelectric nanogenerators (PENGs), providing a high surface area alongside enhanced physicochemical properties for energy harvesting and storage applications. These nanofibers were synthesized through the electrospinning technique, which enables the creation of porous fibers by the dissolution of polymers in volatile solvents. This study investigates the crystalline and chemical structures of PVDF/BF nanofibers with modified formulations. X-ray diffraction (XRD) analysis has confirmed the presence of a rhombohedral (R3c) phase, characteristic of both BiFeO₃ and the PVDF phase. The measured fiber diameters for pure PVDF and PVDF/BF composites varied from approximately 400 nm to 950 nm. Fourier-transform infrared (FTIR) spectroscopy has identified absorption bands at 410–555 cm^-1, which correspond to the functional groups of BiFeO₃, as well as at 612–1430 cm^-1 for PVDF. Moreover, Raman spectroscopy has validated molecular vibrational shifts for BiFeO₃ (4A1+9E) and PVDF within the range of 2973–2977 cm^-1. The incorporation of BiFeO₃ within the PVDF/BF nanofibers enhances the formation of the electroactive β-phase, thereby potentially improving their electrical properties.