Preparation of novel ZnO-NP@Zn-MOF-74 composites for simultaneous removal of copper and tetracycline from aqueous solution

Carboxymethyl chitosan modification of cobalt-zinc bimetallic MOF for tetracycline hydrochloride removal: Exploration of the enhancement mechanism of the process

This study synthesized a carboxymethyl chitosan-modified bimetallic Co/Zn-ZIF (CZ@CMC) with strong hydrophilicity and adsorption performance via the one-pot method. Tetracycline hydrochloride (TCH) was used as the model contaminant to evaluate the adsorption and peroxymonosulfate (PMS) activation properties of CZ@CMC. Mechanism showed that the adsorption behavior occurred through pore filling, electrostatic attraction, surface complexation, hydrogen bonding, and π-π stacking. In addition, a CZ@CMC/PMS system was constructed, which had excellent catalytic performance. The hydrophilicity and selective adsorption properties of CMC conferred a greatly accelerated CZ@CMC in catalyzing the PMS process with kobs of 0.095 min-1, in which OH, 1O2, SO4-, O2-, and Co(III) were the main ROS which quenching tests, EPR, and chemical probe experiments verified. In addition, the degradation pathways of TCH were obtained utilizing DFT and HPLC-MS and analyzed to show that the system possessed a good detoxification capacity. This work is expected to provide a green, efficient, and stable strategy to enhance the adsorption properties of catalytic materials and subsequently their co-catalytic properties.

MWCNTs and ZnO-based Ce-MOF nanocomposites as enhanced sensing platform for electrochemical detection of carbendazim in Chinese traditional herbs samples

A facile and novel Ce-MOF@MWCNTs@ZnO-modified glassy carbon electrode was prepared through drop coating and used for accurate and sensitive electrochemical detection of carbendazim. The modification of ZnO nanospheres and Ce-based metal-organic frameworks (Ce-MOFs), which possess vast surface/bulk ratio, large surface area, and excellent catalytic ability, provided more active sites for reaction. The combination of multi-walled carbon nanotubes endowed the modified electrode with excellent conductivity and greatly accelerated the electron transfer. The promotion of electrochemical response and the significant improvement of peak current indicated the outstanding electrocatalytic ability of the modified electrode. The oxidation peak current of carbendazim which was measured by DPV in a potential range from 0.5 to 1.0 V produced a good linear relationship in the concentration ranges 0.05-10.0 μM and 10.0-50.0 μM under  optimized experimental conditions. The detection limit was 13.2 nM (S/N = 3). The constructed electrode was successfully applied to the detection of carbendazim in Lithospermum and Glycyrrhiza uralensis real samples and exhibited satisfactory RSD (2.7-3.6% and 1.6-4.8%, respectively) and recovery (102-106% and 97.7-107%, respectively).

Fabricating Materials of Institute Lavoisier-53(Fe)/zeolite imidazolate framework-8 hybrid materials as high-efficiency and reproducible adsorbents for removing organic pollutants

Environmental pollution by emerging contaminants has become an urgent problem. Herein, novel binary metal-organic framework hybrids were constructed from Materials of Institute Lavoisier-53(Fe) (MIL-53(Fe)) and zeolite imidazolate framework-8 (ZIF-8) for the first time. A battery of characterizations were employed to determine the MIL/ZIF hybrids' properties and morphology. Furthermore, the MIL/ZIF towards toxic antibiotics (tetracycline, ciprofloxacin and ofloxacin) were studied to explore their adsorption abilities. The present work disclosed that the obtained MIL-53(Fe)/ZIF-8 = 2:3 possessed an eminent specific surface area with an admirable removal efficiency of tetracycline (97.4%), ciprofloxacin (97.1%) and ofloxacin (92.4%), respectively. The tetracycline adsorption process conformed to the pseudo-second-order kinetic model and this process was more compatible with the Langmuir isotherm model with the highest adsorption capacity of 215.0 mg g^-1. Moreover, the process of removing tetracycline was proved to be spontaneous and exothermic by the thermodynamic results. Furthermore, the MIL-53(Fe)/ZIF-8 = 2:3 towards tetracycline exhibited significant regeneration ability. The effects of pH, dosage, interfering ions and oscillation frequency on tetracycline adsorption capacity and removal efficiency were also investigated. The primary factors contributing to the decent adsorption ability between MIL-53(Fe)/ZIF-8 = 2:3 and tetracycline included electrostatic, π-π stacking, hydrogen bonding and weak coordination interactions. Additionally, we also investigated the adsorption ability in real wastewater. Thus, the proposed binary metal-organic framework hybrid materials can be deemed a promising adsorbent in wastewater purification.

Superhydrophobic cellulose paper with sustained antibacterial activity prepared by in-situ growth of carvacrol-loaded zinc-based metal organic framework nanorods for food packaging application

Cellulose paper packaging materials have gained considerable attention as substitutes for petroleum-based plastics owing to their biodegradability, renewability, flexibility, and good mechanical strength. However, high hydrophilicity and the absence of essential antibacterial activity limit their application in food packaging. In this study, a facile and energy-saving method was developed to improve the hydrophobicity of cellulose paper and endow it with a long-acting antibacterial effect by integrating cellulose paper substrate with metal-organic frameworks (MOFs). A dense and homogenous coating of regular hexagonal ZnMOF-74 nanorods was in-situ formed on a paper surface by layer-by-layer assembly followed by low-surface-energy polydimethylsiloxane (PDMS) modification to prepare a superhydrophobic PDMS@(ZnMOF-74)₅@paper. Excellent anti-fouling, self-cleaning, and antibacterial adhesion performances were obtained for this superhydrophobic paper. In addition, active carvacrol was loaded into the pores of ZnMOF-74 nanorods on PDMS@(ZnMOF-74)₅@paper to combine antibacterial adhesion together with bactericidal ability, ultimately resulting in a completely "bacteria-free" surface and sustained antibacterial performance. The resultant superhydrophobic papers not only showed overall migration values within the limit of 10 mg/dm² but also good stability against various harsh mechanical, environmental, and chemical treatments. This work gave insights into the potential of in-situ-developed MOFs-dopped coating as a functionally modified platform for preparing active superhydrophobic paper-based packaging.

H2O2 modified peanut shell-derived biochar/alginate composite beads as a green adsorbent for removal of Cu(II) from aqueous solution

In this study, a novel composite bead (MPB-ALG) was prepared by encapsulating H₂O₂ modified peanut shell-derived biochar (MPB) into alginate matrix through a facile method. The structure and properties of prepared materials were characterized using FTIR, BET, SEM, and XPS. Batch adsorption experiments were performed to compare Cu(II) adsorption performance of MPB, plain alginate beads (ALG) and MPB-ALG. The effect parameters of the components, solution pH, contact time, initial concentration and coexisting ions were studied systematically. The results showed that the maximum adsorption capacity of the optimized MPB-ALG-1 (MPB/alginate = 1:1 w/w%) was 117.4 mg g^-1 at pH 5, which was much higher than that of MPB (37.4 mg g^-1). The adsorption kinetics and isotherms data of Cu(II) on MPB-ALG-1 were well described by Elovich kinetic model and Freundlich adsorption isotherm. Compared with plain ALG beads, MPB-ALG-1 exhibited better reusability and anti-interference of coexisting ions. Finally, the adsorption mechanisms of Cu(II) on MPB-ALG-1 beads were revealed by FTIR and XPS analysis. The experimental results demonstrated that MPB-ALG-1 beads can be used as an environmentally friendly and efficient adsorbent for the removal of Cu(II) from wastewater.

Nitrogen-doped magnetic porous carbon material from low-cost anion-exchange resin as an efficient adsorbent for tetracyclines in water

In this work, nitrogen-doped magnetic porous carbon material (N-MPC) was prepared through the high-temperature calcination of low-cost [Fe(CN)₆]^3--loaded anion-exchange resin, which was experimentally demonstrated to have significant adsorption performance for tetracycline (TC) in water. The N-MPC adsorbent with a large specific surface area (781.1 m² g^-1) was able to maintain excellent performance in a wide pH range from 4 to 10 or in high ionic strength solution. The adsorption of TC on N-MPC was found to be more consistent with the pseudo-second-order model and Langmuir adsorption model, and the maximum adsorption capacity (q_{m, cal}) was calculated to be 603.4 mg g^-1. As a recoverable magnetic adsorbent, the N-MPC remained a TC removal rate higher than 70% after four adsorption cycles. The adsorption mechanism was speculated on the basis of characterizations, where pore filling, hydrogen bonding interaction, and π-π electron donor-acceptor (EDA) interaction were crucial adsorption mechanisms. A variety of antibiotics were selected for adsorption, and excellent performance was found especially for TCs, indicating that the N-MPC can be used for the efficient removal of TCs from water.

Fabrication of a waste cotton fabrics-based nanosystem for simultaneous removal of Cu(II) and Pb(II)

Herein, a waste cotton fabrics-based nanosystem was fabricated to simultaneously remove copper (Cu(II)) and lead ions (Pb(II)) from water and soil. Therein, carboxyl-functionalized zinc oxide microsphere (ZnO-COOH) with peanut shape was carried by cotton fabric (CF) to get CF/ZnO-COOH nanosystem. CF/ZnO-COOH with a good foldable property possessed a high removal capacity for Cu(II) and Pb(II) via electrostatic attraction and chelation. The result indicated that their removal efficiencies of CF/ZnO-COOH could reach over 95% after 2 h. The adsorption process was consistent with Langmuir (R² = 0.9905 of Cu(II) and R² = 0.9846 of Pb(II)) and pseudo-second-order kinetic models (R² = 0.9999 of Cu(II) and R² = 0.9999 of Pb(II)). The thermodynamic data showed that the adsorption process was spontaneous and exothermic. Additionally, CF/ZnO-COOH also possessed a high fixation ability for Cu(II) and Pb(II) in sand-soil column, especially for Pb(II) (15 cm, 0.4 μg kg^-1). Therefore, this wok provides an environmentally friendly and efficient way to remove Cu(II) and Pb(II) from water and soil concurrently.

Synchronous removal of tetracycline and copper (II) over Z‑scheme BiVO4/rGO/g-C3N4 photocatalyst under visible-light irradiation

The combined pollution of heavy metals and organic pollutants in water body has become one of vital environmental issues. Herein, a series of BiVO₄/rGO/g-C₃N₄ nanocomposites were synthesized for concurrent removals of organic pollutant and heavy metal. Results showed that using the optimized photocatalyst BiVO₄/rGO/g-C₃N₄-28, tetracycline (TC) removal of 87.3% and copper (Cu (II)) removal of 90.6% were achieved under visible-light irradiation within 3 h, respectively; much higher than those using BiVO₄ and g-C₃N₄. More importantly, synergistic effect of TC and Cu (II) removals occurred on the surface of BiVO₄/rGO/g-C₃N₄ in the TC-Cu (II) coexistence condition. Additionally, the ·OH and ·O₂- were the most important active species for TC oxidation, while photogenerated electrons were the most responsible for Cu (II) reduction. Results of various characterizations and electron spin resonance test demonstrated that BiVO₄/rGO/g-C₃N₄ was a Z-scheme photocatalyst. Based on the identified intermediates, possible degradation pathways and mechanisms for photocatalytic degradation of TC were proposed. This study advances the development and mechanism of photocatalysts for collaborative removal of pollutants.

Porous multifunctional phenylcarbamoylated-β-cyclodextrin polymers for rapid removal of aromatic organic pollutants

In this work, polymers containing a large number of benzene rings and multiple functional groups were designed to remove aromatic organic pollutants. Using tetrafluoroterephthalonitrile (TFTPN) as a rigid crosslinking agent to crosslink different functionalized phenylcarbamoylated-β-cyclodextrin derivatives to prepare a series of porous multifunctional cyclodextrin (CD) polymerizations, including three preliminary polymerized adsorption materials and a mix β-cyclodextrin polymer (X-CDP) prepared via a secondary crosslinking procedure of the above three materials. The X-CDP preparation process connects the pre-formed nanoparticles and increases the presence of linkers inside the particles. At the same time, X-CDP exhibited porous structure with various functional groups such as nitro, chlorine, fluorine, and hydroxyl. Those special characteristics render this material with good adsorption ability towards various aromatic organic pollutants in water, including tetracycline, ibuprofen, dichlorophenol, norfloxacin, bisphenol A, and naphthol. Especially, the maximum adsorption capacity for tetracycline at equilibrium reached 110.56 mg·g^-1, which is competitive with the adsorption capacities of other polysaccharide adsorbents. X-CDP removed organic contaminants much more quickly than other adsorbents, reaching almost ~95% of its equilibrium in only 30 s, and the rate constant reaches 2.32 g·mg^-1·min^-1. The main adsorption process of the pollutants by X-CDP fitted the pseudo-second-order kinetic and Langmuir isotherm well, indicating that the adsorption process is monolayer adsorption. Moreover, X-CDP possessed the good reusability where the pollutant removal rate was only reduced 8.3% after five cycles. Such advantages render the polymer great potential in the rapid treatment of organic pollutants in water bodies.