Facile fabrication of a noval melamine derivative-doped UiO-66 composite for enhanced Co(II) removal from aqueous solution

Enhanced Ni(II) Removal from Wastewater Using Novel Molecular Sieve-Based Composites

This study focuses on the efficient removal of Ni(II) from spent lithium-ion batteries (LIBs) to support environmental conservation and sustainable resource management. A composite material, known as molecular sieve (MS)-based metal-organic framework (MOF) composites (MMCs), consisting of a synthesized MS matrix with integrated MOFs, was developed for the adsorption of Ni(II). The structural and performance characteristics of the MMCs were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and N2 adsorption-desorption isotherms (BET). Batch adsorption experiments were conducted to assess the Ni(II) adsorption performance of the MMCs. The results revealed that, under conditions of pH 8 and a temperature of 298 K, the MMCs achieved near-equilibrium Ni(II) adsorption within 6 h, with a maximum theoretical adsorption capacity of 204.1 mg/g. Further analysis of the adsorption data confirmed that the adsorption process followed a pseudo-second-order kinetic model and Langmuir isotherm model, indicating a spontaneous, endothermic chemical adsorption mechanism. Importantly, the MMCs exhibited superior Ni(II) adsorption compared to the MS. This study provides valuable insights into the effective recovery and recycling of Ni(II) from spent LIBs, emphasizing its significance for environmental sustainability and resource circularity.

Facile Prepared MOF-OH-PAN Nanofiber for Separation Co(II) from Waste Batteries

Recovering cobalt from waste batteries is crucial for resource recycling and environmental protection. Here, MOF-OH, a Zr-based MOF, was synthesized and merged into a polyacrylonitrile (PAN) matrix to create MOF-OH-PAN nanofibers (NFs). These NFs showed a high cobalt ion adsorption capacity of 33.1 mg/g, retaining over 90% of the capacity after six cycles. The adsorption mechanism involves Co(II) surface diffusion followed by strong bonding with functional groups. This technology enables efficient cobalt recovery from waste batteries, supporting reuse and reducing resource depletion and environmental pollution. The study provides insights into waste battery resource management, highlighting environmental and economic benefits and contributing to green resource recovery and circular economy initiatives.

Facile preparation of UiO-66-Lys/PAN nanofiber membrane by electrospinning for the removal of Co(II) from simulated radioactive wastewater

In this study, metal-organic framework (MOF) nanofiber membranes (NFMs) UiO-66-Lys/PAN were prepared by electrospinning using polyacrylonitrile (PAN) as the matrix, UiO-66-NH2 as the filler, and lysine (Lys) as the functional monomer. The membranes were subsequently employed to extract cobalt ions from simulated radioactive wastewater. The findings showed that the best performance of the membrane was obtained with a 3 % MOF content (3%UiO-66-Lys/PAN). Specifically, the pure water flux (PWF) of the 3 % UiO-66-Lys/PAN membrane reached 872 L m-2 h-1 with a cobalt ion retention of 45.4 %. In addition, adsorption experiments indicated that the NFMs had a theoretical maximum adsorption capacity of 41.4 mg/g for cobalt ions. The Langmuir isotherm model and the pseudo-second-order kinetic model were observed in the adsorption process, suggesting that the membrane material showed uniform adsorption of cobalt ions on a monolayer level, with an endothermic absorption process. XPS analysis confirmed that 3%UiO-66-Lys/PAN facilitated the adsorption of cobalt ions through a coordination effect, with the N and O atoms serving as coordinating atoms. Moreover, the material displayed excellent radiation stability even when exposed to doses ranging from 20 to 200 kGy. This study validated the stability of the MOF NFMs under real irradiation with radioactive nuclides (60Co) and demonstrated efficient cobalt ion separation. This study has important practical implications for the treatment and disposal of small volumes of 60Co-containing radioactive wastewater for engineering applications.

Schiff base-functionalized metal-organic frameworks as an efficient adsorbent for the decontamination of heavy metal ions in water

Adsorptive removal of heavy metal ions from water is an energy- and cost-effective water decontamination technology. Schiff base functionalities can be incorporated into the pore cages of metal-organic frameworks (MOFs) via direct synthesis, post-synthetic modification, and composite formation. Such incorporation can efficiently enhance the interactions between the MOF adsorbent and target heavy metal ions to promote the selective adsorption of the latter. Accordingly, Schiff base-functionalized MOFs have great potential to selectively remove a particular metal ion from the aqueous solutions in the presence of coexisting (interfering) metal ions through the binding sites within their pore cages. Schiff base-functionalized MOFs can bind divalent metal ions (e.g., Pb(II), Co(II), Cu(II), Cd (II), and Hg (II)) more strongly than trivalent metal ions (e.g., Cr(III)). The adsorption capacity range of Schiff base-functionalized MOFs for divalent ions is thus much more broad (22.4-713 mg g-1) than that of trivalent metal ions (118-127 mg g-1). To evaluate the adsorption performance between different adsorbents, the two parameters (i.e., adsorption capacity and partition coefficient (PC)) are derived and used for comparison. Further, the possible interactions between the Schiff base sites and the target heavy metal ions are discussed to help understand the associated removal mechanisms. This review delivers actionable knowledge for developing Schiff-base functionalized MOFs toward the adsorptive removal of heavy metal ions in water in line with their performance evaluation and associated removal mechanisms. Finally, this review highlights the challenges and forthcoming research and development needs of Schiff base-functionalized MOFs for diverse fields of operations.

Synthesis and Application of a Novel Metal-Organic Frameworks-Based Ion-Imprinted Polymer for Effective Removal of Co(II) from Simulated Radioactive Wastewater

In this work, a novel metal-organic frameworks (MOFs)-based ion-imprinted polymer (MIIP) was prepared to remove Co(II) from simulated radioactive wastewater. The batch experiments indicated that the sorption was well described by the pseudo-second-order kinetic and Langmuir models, and it is monolayer chemisorption. The theoretical maximum sorption capacity was estimated to be 181.5 mg∙g^-1, which is by far the reported maximum value of Co(II) sorption by the imprinted materials. The MIIP presented an excellent selectivity for Co(II) in the presence of common monovalent and divalent metal ions, and the selectivity coefficients were 44.31, 33.19, 10.84, 27.71, 9.45, 16.25, and 7.60 to Li(I), K(I), Mg(II), Ca(II), Mn(II), Ba(II), and Cd(II), respectively. The sorption mechanism was explored by X-ray photoelectron spectroscopy (XPS) technology and density functional theory (DFT) calculations, suggesting that Co(II) was adsorbed by the MIIP via the chelation of 4-vinylpyridine (VP) ligands with Co(II), which was a spontaneous process, and the optimal coordination ratio of VP to Co(II) was 6. This work suggested that the MIIP has a high sorption capacity and excellent selectivity for Co(II), which is of great significance for the selective separation of Co-60 from radioactive wastewater.

One-pot synthesis of porous N-doped hydrochar for atrazine removal from aqueous phase: Co-activation and adsorption mechanisms

KOH-activated N-doped hydrochar (KHCN) was synthesized via co-activation method to eliminate atrazine (AT) in water efficiently. Compared to primitive HC, KHCN had advantages of splendid specific surface area (1205.82 m2/g) and developed microsphere structures on the surface. Specially for KHCN, the extra melamine added strengthened and preserved partial structure of polar oxygen-containing groups that were decomposed in the process of pore making. Besides, the estimated uptake amount of AT onto KHCN (216.50 mg/g) was remarkably superior to KHC (114.25 mg/g). KHCN exhibited the pH-dependence for AT removal, and presented excellent uptake capacity at a relatively neutral environment. Notably, the proposed mechanisms for AT removal by KHCN included electrostatic attraction, pore filling, π-π EDA, H-bond as well as hydrophilic effect. Hence, the porous N-doped hydrochar was a kind of adsorbent which was easy to prepare and had the application prospect for AT removal in natural water.

Enhanced adsorption performance of UiO-66 via modification with functional groups and integration into hydrogels

University of Oslo-66 (UiO-66) was a potential adsorbent for removing various pollutants from wastewater. Modifying the UiO-66 surface with different functional groups could enhance the adsorption performance. In this study, the UiO-66 modified with a functional group of -NH₂ or -NO₂ was prepared and tested to adsorb different pollutants. The results showed that -NO₂ modified UiO-66 increased the adsorption capacity of tetracycline by 17 times to 94.08 mg g^-1 compared with unmodified UiO-66. The adsorption process of UiO-66-NO₂ followed the pseudo-second-order adsorption kinetic model and Langmuir isotherm model with a maximum isotherm adsorption capacity of 127.32 mg g^-1. The adsorption interaction was hydrogen bonding and electrostatic attraction. The UiO-66-NO₂ also showed good adsorption performance to Co²⁺, Methylene blue, Congo red. Fixing UiO-66-NO₂ into hydrogel performed a stable absorption performance with a high absorption capacity (71.56 mg g^-1) to TC and a good regeneration rate (85%) after five cycles, providing a novel applicable way to remove pollutants from wastewater.