Volume 96, Issue 8 - Special Issue: Advanced materials for environmental protection

Immense research efforts on graphene or graphene oxide have led to the formation of unique nanocarbon derived nanomaterials. Graphene and graphene oxide have been reinforced in polymeric matrices to form high performance nanocomposites. Significant applications of polymer nanocomposites with graphene or graphene oxide were experiential for nanofiber formation and ensuing membranes. This overview highlights design, essential features, and potential of graphene or graphene oxide derived nanocomposite nanofibrous membranes for water remediation permeation towards contaminates, salts, toxins, microbials, and other separation purposes. Here, polymer filled graphene or graphene oxide nanocomposites have been processed into nanofibers using appropriate techniques such as electrospinning, wet spinning, template method, etc. Afterwards, polymer/graphene and polymer/graphene oxide nanofiber nanocomposites were applied to form the nanocomposite membranes using appropriate techniques like solution processing, casting methods, infiltration, etc. Consequently, high performance membranes have been researched for technological purposes, especially water management competence. Future research on polymer/graphene nanofibrous membranes may lead to highly efficient systems for commercial and industrial level uses.

The use of graphene (GE) as a conductive additive for activated carbon (AC) electrode in capacitive deionization (CDI) has attracted much attention due to its high electrical conductivity. However, self-agglomeration by π–π interactions between individual GE sheets required the use of high content to ensure an efficient conductive network in the electrode, which limited its practical application. This work proposed an approach to reduce the GE content in the fabrication of biomass-based activated carbon electrode for CDI application. The stacking effect of GE sheets is inhibited when GE sheets functionalize with oxygen groups via acid treatment under ultrasonic condition. This helps to reduce GE content to less than 2 wt% in the fabrication of CDI electrodes. The electrode fabricated using 2 wt% treated GE (T-GE) achieved the superior capacitance of 54 F/g, twice that of the pristine AC. The desalination process using as-prepared electrodes was evaluated by batch-mode CDI system with the initial NaCl solution of 2000 ppm and 3000 ppm at various applied voltages. The AC/T-GE 2 % electrode showed excellent performance with a desalination capacity greater than 10 mg/g, and reached an adsorption rate of 1.93 mg/g.min in both solutions under an applied voltage 1.2 V.

In this study, the plant biomass from the phytoremediation was recovered, prepared, and investigated catalytic ability for the α-pinene isomerization. The results show that the Fe_loaded AAL biochar can catalyze the isomerization of a-pinene, with the α-pinene conversion of 90.5 % and the selectivities for monocyclic terpenes (limonene, terpinolene and γ-terpinene) of 57.1 %, bicyclic terpene (camphene) of 24.6 %. Iron in the plant biomass from phytoremediation is considered a decisive factor that heightened the conversion of α-pinene and the yield of isomers. This research has initially opened up a new application for the plant biomass absorbing heavy metal from the phytoremediation stage to resolve contaminants efficiently.

Biomass-based aerogels are of interest due to their abundant precursors, ease of functionalization, eco-friendliness, low cost, and effectiveness in dye-contaminated water treatment. Coconut pith (CP) known as a by-product after coconut processing is a sponge-like and lightweight material discarded in large volumes. For the first time, carbon micro-particles resulting from two-step treatment and pyrolysis of CP have been successfully incorporated with chitosan to produce aerogel composites by high-speed homogenization and freeze-drying. After pretreatment, holocellulose content and crystallinity index of the recovered CP pulp are respectively 75.4 and 58.6 % along with a solid recovery rate of 27.5 %. Characteristic properties of the aerogel composites are featured by their density as low as 15.23–28.17 mg/cm 3 , remarkably high porosity of 98.17–99.05 %, and Young’s modulus of 1.64–12.23 kPa. Synergistic effects of the porous network, electrostatic interactions between both amine groups in chitosan and carbon surface with methyl orange (MO) cause the as-fabricated aerogel composites to achieve an extremely high adsorption capacity of 454.13 mg/g and removal efficiency of 92.32 % at initial MO concentration of 500 mg/L. Therefore, the CP-derived carbon/chitosan aerogel composites synthesized from a feasible procedure exhibit their great potential in enhancing the value of coconut waste and dealing with dye-contaminated water pollution by simple and economical adsorption.

This study aims to synthesize inclusion complex derived from sorafenib (Sor) and hydroxypropyl-β-cyclodextrin (HPβCD) (denoted as [Sor-HPβCD]). The complex of Sor with HPβCD has been synthesized in a mixed solvent of H 2 O-DMSO, with a DMSO volume fraction of 80 %. The results of FTIR, DSC, and UV–Vis analysis have demonstrated the success of complex formation: the intensity of some characteristic peaks for the Sor binding decreased after complex formation, indicating that a part of the guest molecule has entered the cavity of the HPβCD molecule. This is further supported by the DSC analysis results, showing the transformation of the complex’s crystalline form to an amorphous form. The phase solubility diagram study also indicates that the solubility of Sor significantly increases, approximately 7 times higher than pure Sor, after complex formation. The results of the cell growth inhibition activity test in a water environment show that the complex inhibits the growth of Hep-G2 cells with an IC 50 value of 62.4 μg/mL, while pure Sor does not exhibit activity as it is practically insoluble in water.

The purpose of this work is to fabricate the advanced organic antibacterial coating containing the strong photocatalytic nanomaterials. For this purpose, firstly the TiO 2 –Ag hybrid nanoparticles are synthesized by chemical reduction method. Then, the antibacterial coating based on acrylic polyol, polyisocyanate, and these TiO 2 –Ag hybrid nanoparticles has been prepared. Mechanical properties show that the optimal content of TiO 2 –Ag hybrid nanoparticles in the coating matrix is 2 wt%, with its abrasion resistance of 166.2 L/mil; impact strength of 195 kg cm; adhesion of size #1 and relative hardness of 0.78. In addition, FE-SEM analysis shows that the nanocomposite coating has a tight structure with homogeneous dispersion of TiO 2 –Ag nanoparticles in the polymer matrix. The paint film has good antibacterial activity and has great application prospects. Data from the antibacterial test indicates that in the presence of an acrylic polyurethane coating containing 2 wt% TiO 2 –Ag, the number of viable Escherichia coli decreased from 3.4 × 10 5 CFU/ml to 1.5 × 10 2 CFU/ml after 24 h of culture.

This study presents a short communication on exploring, for the first time, a simple approach for the selective and highly effective synthesis of tricaproin by synergistically combining silicon tripolyphosphate and phosphoric acid in the catalytic esterification of glycerol with caproic acid. Results reveal that within the initial hour of the synthesis, the conversion in the presence of the proposed mixture achieved an efficiency of 62.99 %, whereas this figure for individual catalysts only modestly stopped at 27.50 and 11.74 %, respectively. Furthermore, the inherent shortcomings in the tricaprion synthesis, such as catalyst deactivation, resinification of the reaction solution, and generation of numerous by-products, were successfully addressed. The structure of the resultant tricaproin and the possible absence of undesired by-products were confirmed by NMR, mass spectrometry, FT-IR, and TLC. The optimal conditions for the synthesis were also investigated. The study not only contributes a practical and selective synthetic approach for tricaproin but also paves the way for exploring novel avenues to enhance the efficiency of the catalytic esterification.

Silver–zirconia nanoparticles (Ag–ZrO 2 NPs) were synthesized via an in situ strategy at room temperature using NaBH 4 as a reducing agent. The surface modification of ZrO 2 nanoparticles with nano silver was confirmed through various characterization techniques including Fourier Transform Infrared Spectroscopy (FTIR), UV–vis Diffuse Reflectance Spectroscopy (UV–vis DRS), X-ray Diffraction (XRD), and Field Emission Scanning Electron Microscopy (FESEM). The obtained results demonstrated that Ag nanoparticles, with a crystallite size of approximately 12 nm, were uniformly distributed on the surface of ZrO 2 nanoparticles. The incorporation of Ag nanoparticles to the ZrO 2 nanoparticles led to increasing the light absorption ability and reducing the band gap of Ag–ZrO 2 nanoparticles, thereby enhancing their photocatalytic performance under infrared lamp exposure. When 1 g/L of Ag–ZrO 2 nanoparticles was employed to methylene blue (MB) solution, the degradation of MB reached 90 % after 5 h of exposure. Additionally, the Ag–ZrO 2 nanoparticles exhibited a high antibacterial activity against two bacterial strains, E. coli and S. aureus . These findings highlight the potential of Ag–ZrO 2 nanoparticles as effective materials for environmental pollution treatment through advanced oxidation processes.

Sulfur nanoparticles (SNPs) in chitosan-copper (CS-Cu 2+ ) complex solution were prepared by hydrolysis of sodium thiosulfate (Na 2 S 2 O 3 ) in an acidic medium of CS-Cu 2+ complex. The size of SNPs was inversely proportional to the Cu 2+ /−NH 2 molar ratio, decreasing from 35 to 22 nm corresponding to the Cu 2+ /−NH 2 molar ratio increasing from 0/1 to 1/1. The SNPs/CS-Cu 2+ complex was characterized by Ultraviolet-Visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) spectroscopy. The nematicidal activity against Pratylenchus pratensis in vitro was investigated by treating the CS-Cu 2+ complex and SNPs/CS-Cu 2+ complex with Cu 2+ /−NH 2 molar ratio of 0.5/1. Results showed that the nematicidal activity of the SNPs/CS-Cu 2+ complex was higher than that of the CS-Cu 2+ complex, particularly the 50 % lethal dose (LC 50 ) after 48 h of treatment was 77 and 89 mg/L, respectively. The results demonstrated that the prepared SNPs/CS-Cu 2+ complex can be used as a nematicide for plants.

Recently, hybrid capacitive deionization (HCDI) has been a promising desalination technology because of its low cost and effective ion removal ability. The electrode material is an important factor to affect to desalination capacity of HCDI technology. In this study, the nanocomposite electrodes were fabricated successfully based on activated carbon and reduced-graphene oxide/cobalt oxide (rGO-Co 3 O 4 ) and polymeric binders which were used as cathode electrodes for Hybrid capacitive deionization (HCDI) technology. The effect of polyvinyl alcohol (PVA) and polyvinylidene fluoride (PVDF) polymeric binders and the amount of rGO-Co 3 O 4 on characteristic as well as specific capacitance of the nanocomposite electrodes were investigated. The nanocomposite electrode combined hydrophilic binder of PVA-based and 50 % rGO-Co 3 O 4 has a specific capacitance of 15.3 mg/g in 200 ppm NaCl solution after 25 min at 1.2 V, which is 1.67 times higher than that of the AC-based electrode.

This study investigates the development of polylactic acid (PLA) by incorporating thermochromic black pigments (TCB) at varying concentrations of 0, 0.5, 1, 2 and 3 wt% through the process of melt blending. The color transition and reversion behaviors of the resulting specimens were examined at different temperatures (−10, 10, 30, 35 and 50 °C) using colorimetric analysis. Additionally, mechanical properties, thermal characteristic and thermal stability were assessed through tensile testing, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. The study revealed that an increase in TCB concentrations led to a reduction in lightness (L*). Higher pigment content enhanced thermochromic properties, resulting in more pronounced color changes. The total color difference (ΔE) remained reproducible over five cycles of heating and freezing, and this reproducibility persisted after thermal aging. Tensile strength and elongation at break exhibited improvement with increasing pigment content. Glass transition temperature (T g ) and melting temperature (T m ) of the thermochromic samples showed minimal reduction compared to that of neat PLA, which is 64.2 °C. Crystallinity degree (X c ) increased slightly by 0.2–0.92 %. The thermal stability of the PLA matrix was only marginally affected by the presence of thermochromic pigments.

In this investigation, we study the influence of the loading of ground tyre rubber (GTR), referred to as rubber dust 40 mesh (RD40), on the intrinsic self-healing natural rubber (NR) based on metal-thiolate ionic networks. The loading of RD40 particles was varied at 10, 20, and 30 phr to assess the optimum amount for interfacial bonding, mechanical and dynamic properties, and healing efficiency. The quantitative measurement of metal-thiolate ion networks and covalent crosslinks was assessed through swelling tests. The effects of RD40 loading on the dynamic mechanical properties and morphological characteristics were also investigated. Tensile properties of the rubbers before and after healing were measured using universal testing tester to obtain healing efficiency of the materials. The results showed that the developed materials have the ability to autonomously repair themselves at room temperature without the need for manual intervention. The results also revealed the tensile strength and elongation at break of self-healing NRs filled with 10 phr of RD40 were recovered 92 % and 93 %, respectively. The findings demonstrated the benefits of utilizing GTR as an effective sustainable filler and advanced the understanding of self-healing strategies and the interaction between ground tyre rubber and rubber matrices.

MXenes is a new two-dimensional material which is gaining more attention in recent years for applications in catalysis, energy storage, and environmental remediation. In this study, MXene-Ti 3 C 2 is synthesized from precursor MAX-Ti 3 AlC 2 via etching method and then combined with coconutshell-derived activated carbon to provide a highly conductive and porous composite. The composite will be later employed as electrode materials in capacitive deionization for water desalination. The results have shown an increase in specific capacitance by 3.7 times in the composite (0.5 wt% MXene-Ti 3 C 2 ) when compared with pure activated carbon. These promising results have proved the possibility to use MXenes-based composites for desalination and other treatment techniques for salted water.

This work aims to fabricate the antibacterial coating with green biocide successfully. For this purpose, mimosa tannins were acylated with lauroyl chloride’s aid and pyridine’s support as a catalyst in the 1,4-dioxane, hexane and xylene solvents. Infrared analysis showed that mimosa tannins synthesized in the 1,4-dioxane were acylated better than in the other two solvents. FE-SEM analysis of the paint film showed that the acylated mimosa tannins at a content of 5 % dispersed quite well in the polymer matrix. The results of analyzing the mechanical properties of the paint film containing acylated mimosa tannins with contents ≤5 % show that the mechanical properties of the paint film are only slightly reduced compared to the mechanical properties of the pure coating, reaching the values: adhesion of size #1; abrasion resistance of 132.8 L/mil; impact strength of 170 kg cm and a relative hardness of 0.78. Antibacterial testing shows that the paint film containing 5 wt% acylated mimosa tannins have good antibacterial activity.

This work is motivated by the desire to restore the quality of rubber-based product properties with the intention of prolonging the service life period, thus helping create a sustainable environment by proposing effective rubber waste management. This study experimentally investigated an intrinsically self-healing zinc thiolate grafted natural rubber (NRZT) compound filled with multi-walled carbon nanotubes (MWCNT) to assess its influence on mechanical properties and self-healing performance. The MWCNT loading varied to 0, 2, 4, 6, and 8 phr. The Equilibrium swelling test was used to quantify the amount of ionic and covalent crosslinks formed. Fourier Transform Infrared (FTIR) spectra were used to detect the presence of MWCNT in the compound. The mechanical properties computed by the tensile and tear strength tests showed that the incorporation of MWCNT increased both properties up to three and twofold, respectively. However, as expected, the elongation at break (Eb) value was reduced. The unfilled sample showed that it can heal up to ∼98 %, measured from the tensile strength. However, the healing efficiency obtained from tensile strength reduces to ∼88 % by incorporating 2 phr MWCNT. The Eb and its self-healing efficiency gradually decreased as the MWCNT amount increased. All samples showed outstanding properties under the tearing mode, where the healed samples produced higher tear strength (>100 % healing) than the initial value. Scanning Electron Microscopy (SEM) micrographs revealed a noticeable gap along the healed cut line with increased MWCNT numbers, possibly due to the lower reaction between polymerized zinc thiolate (PZTh) radicals with zinc thiolate (ZT) and rubber molecules. The work aims to investigate the influence of MWCNTs on the mechanical and healing performance of self-healing NR composites by comparing them to their unfilled sample.

This study investigates the mechanical properties of hybrid composites composed of web kapok fibers and fiberglass reinforced with epoxy for potential application in the marine industry. The web kapok fibers were carefully processed using a carding technique to ensure better alignment and consistency. Various composite configurations were produced, and extensive mechanical testing was conducted, including flexural, tensile, and impact tests. The results revealed that the presence of two web kapok fiber layers within the composite significantly increased flexural strength and flexural modulus compared to pure fiberglass laminates. However, a single layer of web kapok fabrics exhibited the highest tensile strength, although it decreased with additional layers. The impact strength of these hybrid composites also showed promising results, especially when compared to raw fiberglass composites. Moreover, these composites exhibited improved resistance to water absorption and corrosion, making them potentially suitable for marine applications. This research highlights the potential of web kapok/fiberglass hybrid composites as an eco-friendly alternative for marine engineering, with implications for reduced environmental impact and sustainable technology in the industry.

Natural rubber (NR) is a complex material that is often discarded due to its three-dimensional structure. Recycling of rubber is difficult due to its complex structure, and only 1.7 million tonnes of waste, such as tyres and gloves, are considered recyclable. This study aims to develop self-healing rubber, which allows a product to recover without affecting structural reliability. Commercial NR was ionically crosslinked with zinc thiolate, forming an ionic crosslink network between rubber chains and zinc thiolate ions. The ionic crosslinks allow the rearrangement of rubber molecular chains under external heat, providing self-healing capabilities. The highest ionic crosslink density was found in NR with 35 phr zinc thiolate. The self-healing NR can recover 90 % of its initial properties at room temperature for 10 min and can be reprocessed and recycled three times without compromising its properties. It also shows excellent weldability, making it a promising material for repairing existing rubber products in heavy engineering applications.