EDTA-Cross-Linked β‑Cyclodextrin: An Environmentally Friendly Bifunctional Adsorbent for Simultaneous Adsorption of Metals and Cationic Dyes

The discharge of metals and dyes poses a serious threat to public health and the environment. What is worse, these two hazardous pollutants are often found to coexist in industrial wastewaters, making the treatment more challenging. Herein, we report an EDTA-cross-linked β-cyclodextrin (EDTA-β-CD) bifunctional adsorbent, which was fabricated by an easy and green approach through the polycondensation reaction of β-cyclodextrin with EDTA as a cross-linker, for simultaneous adsorption of metals and dyes. In this setting, cyclodextrin cavities are expected to capture dye molecules through the formation of inclusion complexes and EDTA units as the adsorption sites for metals. The adsorbent was characterized by FT-IR, elemental analysis, SEM, EDX, ζ-potential, and TGA. In a monocomponent system, the adsorption behaviors showed a monolayer adsorption capacity of 1.241 and 1.106 mmol g^–1 for Cu­(II) and Cd­(II), respectively, and a heterogeneous adsorption capacity of 0.262, 0.169, and 0.280 mmol g^–1 for Methylene Blue, Safranin O, and Crystal Violet, respectively. Interestingly, the Cu­(II)–dye binary experiments showed adsorption enhancement of Cu­(II), but no significant effect on dyes. The simultaneous adsorption mechanism was further confirmed by FT-IR, thermodynamic study, and elemental mapping. Overall, its facile and green fabrication, efficient sorption performance, and excellent reusability indicate that EDTA-β-CD has potential for practical applications in integrative and efficient treatment of coexistenting toxic pollutants

Green Synthesis of Magnetic EDTA- and/or DTPA-Cross-Linked Chitosan Adsorbents for Highly Efficient Removal of Metals

The present paper describes a green and economic approach to explore EDTA/DTPA-functionalized magnetic chitosan as adsorbents for the removal of aqueous metal ions, such as Cd­(II), Pb­(II), Co­(II), and Ni­(II). EDTA and DTPA play roles not only as cross-linkers but also as functional groups in chelating metal ions. The morphology, structure, and property of the magnetic adsorbents were characterized by SEM, TEM, XRD, EDS, FT-IR, TGA, and VSM techniques. Their adsorption properties for the removal of metal ions by varying experimental conditions were also investigated. The kinetic results revealed that the transportation of adsorbates from the bulk phase to the exterior surface of adsorbents was the rate-controlling step. The obtained maximum adsorption capacities of magnetic adsorbents for the metal ions ranged from 0.878 to 1.561 mmol g^–1. Bi-Langmuir and Sips isotherm models fitting well to the experimental data revealed the surface heterogeneity of the adsorbents. More significantly, the resulting EDTA-/DTPA-cross-linked magnetic chitosan adsorbents had selectivity to Cu, Pb, Zn, Fe, and Ni from a practical industrial effluent. Furthermore, their good reusability and convenient magnetic separation makes them viable alternatives for real wastewater treatment

Pressure-Induced Enhancement of Photoelectric Properties of ZnO Nanoparticles in the Ultraviolet Band: Implications for Electronic Device Applications

We report the photoelectric properties and structural changes of ZnO nanoparticles (∼63 nm) under pressures of up to 22.9(5) GPa using in situ Raman spectroscopy, photocurrent measurements, and theoretical calculations. The ZnO nanoparticles show enhanced photocurrent (2.8 mA) and responsivity (4.78 × 106 mA W–1) under 365 nm irradiation in the wurtzite (B4) phase. On the contrary, the rock-salt (B1) phase, emerging post the wurtzite phase, exhibits a smaller band gap and decreased absorption coefficient, leading to reduced photocurrents and responsivity. These findings highlight the potential of high-pressure modulation to optimize the photoelectronic properties of ZnO nanoparticles for electronic device applications