Polyethylenimine-Grafted-Corncob as a Multifunctional Biomaterial for Removing Heavy Metal Ions and Killing Bacteria from Water

Preparation of amino-functionalized yeast/yam starch composite adsorption gel and its mechanism for the adsorption of Congo red and copper ions

Water resource pollution is a major global challenge that poses a serious threat to human health and the environment. In this study, glutaraldehyde was used to cross-link polyethyleneimine (PEI) with yeast and starch. The PEI-modified yeast was attached to the yam starch adsorption gel using the gel properties of starch to prepare a novel starch-based composite adsorbent material (NH2(Gl)-YSA@SZ410). Owing to its porous interconnected structure, the material exhibited optimal adsorption performance, wettability, and mechanical properties. NH2(Gl)-YSA@SZ410 could remove Congo red (CR), Cu2+, and coexisting pollutants (CR and Cu2+ mixture) from solutions. At 308 K, in single CR- or Cu2+-contaminated solutions, the maximum adsorption capacities were 293.52 and 50.34 mg/g, respectively, whereas in the binary-pollutant system, the maximum adsorption capacities were 363.15 and 149.50 mg/g, respectively. Additionally, an in-depth study of single-pollutant and binary-pollutant systems was conducted using adsorption kinetics, isotherms, and adsorption mechanisms. Theoretical calculations indicated that CR and Cu2+ interacted with NH2(Gl)-YSA@SZ410 composite materials through forces such as hydrogen bonding and electrostatic interactions. Furthermore, NH2(Gl)-YSA@SZ410 exhibited excellent stability and practicality. The adsorbent can be effectively applied to wastewater containing both heavy metals and dyes, offering novel ideas for biobased adsorbents.

Copper-Binding Properties of Polyethylenimine-Silica Nanocomposite Particles

Increasing demand for copper resources, accompanied by increasing pollution, has resulted in an urgent need for effective materials for copper binding and extraction. Polyethylenimine (PEI) is one of the strongest copper-chelating agents but is not suitable directly (as is) for most applications due to its high solubility in water. PEI-based composite materials show potential as efficient and practical alternatives. In the present work, the interaction of copper ions with PEI-silica nanocomposite particles and precursor PEI microgels (as a reference) is investigated. It is hypothesized that the main driving force of the reaction is chelation of copper ions by amino groups in the PEI network. The presence of silica in the PEI-silica composites was shown to increase the copper-binding capacity in comparison with the parent microgel. The copper-binding behavior of etched (PEI-free "ghost") composite particles in comparison with the original composites and microgel particles shows that silica nanoparticles in the composite structure increase the number of copper-binding sites in the PEI network rather than adsorbing copper themselves. PEI-silica composites can be easily recycled after copper adsorption by simply washing in 1 M nitric acid, which results in complete copper extraction. Employing this recovery method, PEI-silica composite particles can be used for multiple, efficient cycles of copper removal and extraction.

Ferric iron loaded porphyrinic zirconium MOFs on corncob for the enhancement of diuretics extraction

Herein, corncob waste was used as a scaffold for the fabrication of effective adsorbents. Porphyrinic zirconium metal-organic frameworks (MOFs) PCN-223 and PCN-224 constructed by different numbers of Zr6 cluster nodes were grown on the surface of the corncob. Fe (Ш) ions were implanted in the porphyrin ring by post-synthesis modification. The results showed that the extraction capacity of diuretics on PCN-224@corncob containing suitable pore size was larger than that of PCN-223@corncob. The adsorption of diuretics was further enhanced because of the electrostatic effect caused by implantation of Fe (Ш) ions. PCN-224-Fe@corncob was recyclable and selective for the extraction of furosemide (Fur) and bumetanide (Bum). Coupled in-syringe solid phase extraction (IS-SPE) with ultra-performance liquid chromatography (UPLC), an efficient, sensitive, and stable method was established. With a sensitivity between 0.6 and 1.0 μg/L and a recovery between 83.2% and 119.2%, it is used for the analysis of trace amounts of Fur and Bum in weight loss products and environmental water. The functionalized corncob has potential application for the adsorption of diuretics, and the metal ions implantation in MOFs provides a promising strategy for enhancing extraction capacity.

Polyethyleneimine grafted starch nanocrystals as a novel biosorbent for efficient removal of methyl blue dye

In this paper, a novel biosorbent of SNCs-PEI was successfully prepared by grafting polyethylenimine (PEI) onto the starch nanocrystals (SNCs) using glutaraldehyde as a crosslinking agent. The optimal preparation conditions of SNCs-PEI were determined by the orthogonal experiments of the three-factor and three-level, and the SNCs-PEI was characterized by Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy (EDAX), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The zeta potential of SNCs-PEI was +26.3 mV (pH 7), which had a good adsorption performance for the anionic dye methyl blue (MB). The adsorption kinetics and isotherm of MB by SNCs-PEI were studied. At the temperature of 25, 30 and 35 °C, its maximum adsorption capacity was 337.84, 377.36 and 383.14 mg g^-1, respectively. The adsorption of MB by the SNCs-PEI was a spontaneous and endothermic process according to the thermodynamic analysis.