Stable and recyclable polyporous polyurethane foam highly loaded with UIO-66-NH2 nanoparticles for removal of Cr(Ⅵ) in wastewater

Multinetwork Aerogels with In-situ Grown UiO-66: Efficient Adsorption of Diclofenac Sodium and Mechanism Decoding

Diclofenac sodium (DCF) is a novel pollutant that poses a significant environmental threat. Aerogels effectively adsorb diclofenac sodium, but their low density and high porosity exhibit poor adsorption and mechanical properties during adsorption. To overcome the limitations of traditional aerogels, specifically their poor structural integrity and inadequate adsorption performance, multinetwork aerogels were fabricated through successive integration of sodium alginate (SA) with Ca2+, chitosan (CS) with SA, and polyethyleneimine (PEI) with CS, followed by in situ formation of UiO-66@SA/CS/PEI. The results show that the multinetwork structure in the material dramatically enhances the aerogel's stability, which has been greatly improved. After amino modification, the maximum adsorption capacity reached 775.9 mg/L, 2.6 times that of the single network aerogel. A combination of adsorption modeling, molecular simulation and material structure characterization was used to analyze the adsorption mechanism in depth. Analysis revealed that the adsorption mechanism involved a heterogeneous endothermic process, predominantly governed by chemisorption accompanied by synergistic physicochemical interactions. The π-π EDA interaction, metal (Zr)-π interaction, electrostatic interaction, coordination of Zr with O and Cl, and hydrogen bonding were identified. Interference experiments show that UiO-66@SA/CS/PEI has good stability in different environments. This study provides new ideas for the synthesis and adsorption mechanism research of MOF-based poly-network aerogels, as well as theoretical support for the direction of material structure optimization and selective adsorption of DCF.

Nanocellulose encapsulated nZVI@UiO-66-NH2 aerogel for high-efficiency p-chloronitrobenzene removal with selective reduction

A poriferous nZVI aerogel (nZVI@UiO-66-NH2/TCNF) was elaborately constructed by in-situ deposition of nZVI on UiO-66-NH2 and coupling with a bio-based TEMPO oxidized cellulose nanofiber (TCNF) substrate, followed by freeze-drying process for p-chloronitrobenzene (p-CNB) degradation. With degradation efficiency of above 85 % within 3 h under a wide pH range of 3-9, the nZVI@UiO-66-NH2/TCNF aerogel presented better p-CNB removal performance than other developed aerogels. Extended to 24 h, superior p-CNB removal performance (99.83 %) and 4-chloroaniline (p-CAN) selectivity (98.84 %) were successfully achieved. This could be attributed to 1) the facilitated mass transfer via concentration-gradient driving force with buffering and drag-reducing hydrated shear layer from porous channels of hydrophilic TCNF; 2) the enhanced adhesion of p-CNB onto UiO-66-NH2 and accelerated electron transfer by Fe-O-Zr bonds, synergistically improving the nitro- reduction of p-CNB using nZVI. This work pioneered a unique paradigm, providing nZVI with both solid bio-based moldability and highly-selective removal for the treatment of chloronitrobenzene containing wastewater.

Develop Reusable Carbon Sub-Micrometer Composites with Record-High Cd(II) Removal Capacity

Cd(II)-induced pollution across diverse water bodies severely threatens ecosystems and human health. Nevertheless, achieving ultra-efficient and cost-effective treatment of trace amounts of heavy metals remains a major challenge. Herein, the novel carbon sub-micrometer composites (CSMCs) supported Fe0@γ-Fe2O3 core-shell clusters nanostructures are designed and synthesized through a series of universally applicable methods. Research data on adsorption behavior clearly revealed that resorcinol/formaldehyde 1.25-basic ferric acetate (RF-1.25BFA) and RF-1.25BFA-540 have surprising adsorption capacities. Employing the adsorbent dosage of 0.025 g L-1, the adsorption capacities for 10 mg L-1 Cd(II) reached 400.00 mg g-1 with ultrafast adsorption kinetics, alongside theoretical maximum adsorption capacities for Cd(II) of 1108.87 and 1065.06 mg g-1 using 0.025 g L-1 adsorbent, respectively, setting a new record-high level. Additionally, they demonstrated exceptional stability and reusability, maintaining Cd(II) removal efficiency above 95% even after 15 adsorption-desorption cycles. Importantly, this study is the first to unveil a new ultrafast successive two-step enrichment-hydrolysis adsorption mechanism for Cd(II) removal, emphasizing the critical role played by iron clusters nanostructures in constructing a high-alkalinity adsorption microenvironment on the surface of the materials. The findings reported pioneered a new avenue for the rational design of high-performance environmental remediation materials, aiming to overcome the limitations of traditional mine drainage treatment.

Adsorption Performance for Chromium(VI) of a UiO-66-Ce Metal-Organic Framework Built by DL-Aspartic Acid

Metal-organic frameworks (MOFs) have recently received a lot of interest for their use in adsorbing and eliminating hexavalent chromium from water. Obtaining low-cost, biocompatible, and environmentally friendly MOFs for research in this field is vital. One very stable three-dimensional UiO-66-Ce(IV) MOF, Ce-asp, was synthesized with a high yield using an amino acid ligand, DL-aspartic acid. As a result, the adsorption characteristics of the MOF against hexavalent chromium ions in aqueous solution were examined. The effects of time, solution pH, MOF dose, and beginning chromium(VI) content in aqueous solution were investigated on adsorption. More crucially, the adsorption mechanism of this MOF for chromium(VI) was proposed, setting the groundwork for its future use in chromium(VI) removal in real-world waters.

ZnO/PUF composites with a large capacity for phosphate adsorption: adsorption behavior and mechanism studies

Phosphate is present in all kinds of industrial wastewater; how to remove it to meet the strict total phosphorus discharge standards is a challenge. This study used a one-step foaming technique to fill polyurethane foam (PUF) with ZnO, taking advantage of PUF's excellent features like its porous network, lightweight, hydrophilicity, and abundance of binding sites to create ZnO/PUF composites with high adsorption capacity and exceptional separation properties. The adsorption isotherms, kinetics, starting pH, and matrix impacts of ZnO/PUF composites on phosphate were examined in batch studies. The results showed that the composites had good adsorption performance for phosphate with a saturated adsorption capacity of 460.25 mg/g. The quasi-secondary kinetic and Langmuir models could better describe the adsorption process, which belonged to the chemical adsorption of monomolecular layers. The composites' ability to treat phosphates in complicated waters was shown by their ability to retain a high adsorption capacity in the pH range of 3-6. In column experiments, the composite also maintains a good affinity for phosphate during dynamic adsorption. Multiple characterizations indicate that the adsorption mechanism is a combined effect of ligand exchange and electrostatic interactions. Therefore, this study provides valuable insights for practical phosphorus-containing wastewater treatment.

Removal of Hg2+ in wastewater by grafting nitrogen/sulfur-containing molecule onto Uio-66-NH2: from synthesis to adsorption studies

The remediation of heavy metal deserves to be on the agenda, with the adsorbent design bearing the brunt of it. In this study, the molecule (4, 6-diamino-2-mercaptopyrimidine, DMP) containing thiol (-SH) and amino (-NH₂) functional groups was grafted onto Uio-66-NH₂, and a composite metal-organic framework nanomaterial (Zr(NH₂)-DMP) was synthesized via a facile post-modification scheme. The morphological characteristics and structural features of the modified adsorbent were characterized by XRD, FT-IR, FE-SEM, EDS, BET, and XPS. The characterization results verified that the post-modification scheme was successfully achieved. The adsorption experiments were carried out to investigate the removal performance of the Zr(NH₂)-DMP towards Hg²⁺ under different influencing parameters. The maximum adsorption capacity of 389.4 mg/g was obtained, and the adsorption equilibrium was achieved within 30 min at pH 6 at room temperature. Adsorption thermodynamic study indicated that the adsorption process was exothermic and spontaneous. The Zr(NH₂)-DMP exhibited excellent selectivity for Hg²⁺, and also has the potential to remove Cu²⁺, Fe²⁺, and Zn²⁺ ions. The introduction of Cl^- inhibited the removal of Hg²⁺ due to the formation of mercuric chlorides (removal efficiency reduced from 97.8 to 95.6%). The removal efficiency of up to 86.7% was obtained after four cycles. The Langmuir isotherm and Pseudo-second kinetic were more suitable for fitting the adsorption process of Hg²⁺ by Zr(NH₂)-DMP. The main removal mechanism could be attributed to the chelation between Hg²⁺ (soft acid) and nitrogen/sulfur (soft base) elements. These findings convinced that the successful synthesis of Zr(NH₂)-DMP provides an option for Hg²⁺ removal from wastewater.