New strategy of improving the dispersibility of acrylamide-functionalized graphene oxide in aqueous solution by RAFT copolymerization of acrylamide and acrylic acid

On the performance of Sargassum-derived calcium alginate ion exchange resins for Pb2+ adsorption: batch and packed bed applications

Driven by climate change and human activity, Sargassum blooming rates have intensified, producing copious amount of the invasive, pelagic seaweed across the Caribbean and Latin America. Battery recycling and lead-smelter wastes have heavily polluted the environment and resulted in acute lead poisoning in children through widespread heavy metal contamination particular in East Trinidad. Our study details a comprehensive investigation into the use of Sargassum (S. natans), as a potential resource-circular feedstock for the synthesis of calcium alginate beads utilized in heavy metal adsorption, both in batch and column experiments. Here, ionic cross-linking of extracted sodium alginate with calcium chloride was utilized to create functional ion-exchange beads. Given the low quality of alginates extracted from Sargassum which produce poor morphological beads, composite beads in conjunction with graphene oxide and acrylamide were used to improve fabrication. Stand-alone calcium alginate beads exhibited superior Pb2+ adsorption, with a capacity of 213 mg g-1 at 20 °C and pH 3.5, surpassing composite and commercial resins. Additives like acrylamide and graphene oxide in composite alginate resins led to a 21-40% decrease in Pb2+ adsorption due to reduced active sites. Column operations confirmed Alginate systems' practicality, with 20-24% longer operating times, 15 times lower adsorbent mass on scale-up and 206% smaller column diameters compared to commercial counterparts. Ultimately, this study advocates for Sargassum-based Alginate ion-exchange beads as a bio-based alternative in Trinidad and developing nations for dealing with heavy metal ion waste, offering superior heavy metal adsorption performance and supporting resource circularity.

Synthesis, Characterization, and CO2/N2 Separation Performance of POEM-g-PAcAm Comb Copolymer Membranes

Alcohol-soluble comb copolymers were synthesized from rubbery poly(oxyethylene methacrylate) (POEM) and glassy polyacrylamide (PAcAm) via economical and facile free-radical polymerization. The synthesis of comb copolymers was confirmed by Fourier-transform infrared and proton nuclear magnetic resonance spectroscopic studies. The bicontinuous microphase-separated morphology and amorphous structure of comb copolymers were confirmed by wide-angle X-ray scattering, differential scanning calorimetry, and transmission electron microscopy. With increasing POEM content in the comb copolymer, both CO₂ permeability and CO₂/N₂ selectivity gradually increased. A mechanically strong free-standing membrane was obtained at a POEM:PAcAm ratio of 70:30 wt%, in which the CO₂ permeability and CO₂/N₂ selectivity reached 261.7 Barrer (1 Barrer = 10⁻¹⁰ cm³ (STP) cm cm⁻² s⁻¹ cmHg⁻¹) and 44, respectively. These values are greater than those of commercially available Pebax and among the highest separation performances reported previously for alcohol-soluble, all-polymeric membranes without porous additives. The high performances were attributed to an effective CO₂-philic pathway for the ethylene oxide group in the rubbery POEM segments and prevention of the N₂ permeability by glassy PAcAm chains.

Graphene oxide aerogel assembled by dimethylaminopropylamine /N-isopropylethylenediamine for the removal of copper ions

Graphene Oxide Monolith composites (GOMs) were prepared using dimethylaminopropylamine (DMPDA) and N-isopropylethylenediamine (IPEDA) with one-step method in water medium, respectively. Fourier transform-infrared (FTIR), X-Ray Diffraction (XRD) tests proved the formation of new structure and credible interactions between crosslinkers and GO. Scanning electron microscopy (SEM) showed distinct change of morphology after complexing. Bath adsorption tests suggested that the fast adsorption of copper ions (II) was strongly affected by pH, ionic strength, temperature, and concentration, etc.. Isothermal Langmuir and Freundlich kinetic model showed the different degree of fitting conformity according to different conditions. SEM and XRD further provided a supporter of adsorption of copper ions onto GOMs, and Density functional theory (DFT) was used to analyze the crosslinking details of DMPDA and GO and the adsorption mechanism of copper ions. The theoretical calculation results clarified an efficacious and quantitative understanding for the crosslinking and adsorption mechanism.

Corrosion resistance of itaconic acid doped polyaniline /nanographene oxide composite coating

Graphene oxide (GO) and polyaniline (PANI) are very unique materials with broad potential in corrosion protection coating. To achieve the maximum stability and anti-corrosion effect in a polar medium, firstly itaconic acid doped PANI (DP) was readily prepared by a one-step method, followed by forming a GO and DP composite (GODP). Characterization by Fourier transform infrared spectroscopy and ultraviolet-visible absorption spectra provides evidence for the successful doping of itaconic acid in PANI. X-ray diffraction analysis shows that the d-spacing of the GO sheets increases slightly with the intercalation of DP. The morphological studies show disordered structures in GODP compared with the original GO sheets due to the introduction of PANI molecules and the interaction of functional groups on the surface of the GO sheets. Thermogravimetric analysis reveals the good thermal stability of DP and GODP. Quantum calculation further confirms the successful doping of itaconic acid, and the effective complex of GO and DP, providing a quantitative understanding of the curing mechanism. The crosslinking interaction among the GODP, curing agent, and epoxy resin facilitates the formation of a compact coating, leading to excellent corrosion resistance toward Mg alloy.