Capture of iodide from wastewater by effective adsorptive membrane synthesized from MIL-125-NH2 and cross-linked chitosan

Preparation of a novel citric acid-crosslinked Zn-MOF/chitosan composite and application in adsorption of chromium(VI) and methyl orange from aqueous solution

A novel citrate-crosslinked Zn-MOF/chitosan (ZnBDC/CSC) composite was successfully prepared by immobilizing Zn-MOF (ZnBDC) on citrate-crosslinked chitosan (CSC) using citric acid as a chemical bridge. ZnBDC/CSC was characterized by XRD, FT-IR, solid-state ¹³C NMR, BET and SEM. The adsorption of ZnBDC/CSC for Cr(VI) and MO from aqueous solutions were studied at pH 5.0. The adsorption conditions, such as adsorption time and initial concentration of Cr(VI) and MO solutions were investigated. The results indicated that ZnBDC/CSC showed high adsorption capacity for both Cr(VI) (225 ± 4 mg g^-1) and MO (202 ± 3 mg g^-1), respectively. The adsorption of Cr(VI) on ZnBDC/CSC could be well described by Langmuir isotherm model, while MO followed Freundlich model. The adsorption kinetic of Cr(VI) and MO demonstrated a better fitness to the pseudo-second order kinetic model. Thermodynamic parameters (enthalpy (ΔH), entropy (ΔS) and Gibbs free energy (ΔG)) demonstrated that the adsorption processes of Cr(VI) and MO on ZnBDC/CSC were exothermic, disordered and spontaneous at 298-318 K. The adsorption mechanism of ZnBDC/CSC for Cr(VI) could be mainly explained by electrostatic attraction and cation-π interaction, while for MO, it could be assigned to n-π and π-π interactions, electrostatic attraction and hydrogen bonding. ZnBDC/CSC could be recycled and reused for the removal of Cr(VI) and MO.

Silver chromate doped Ti-based metal organic framework: synthesis, characterization, and electrochemical and selective photocatalytic reduction properties

Ag₂CrO₄@NH₂-MIL-125 has excellent not only photocatalytic activity toward nitroaniline selective reduction but also electrochemical properties.

Development of biological macroalgae lignins using copper based metal-organic framework for selective adsorption of cationic dye from mixed dyes

The chemical compositions of macroalgae are protein; cholesterol, fatty acid, and lignin which mostly construct from hydroxyl and amine groups. The lignin as a key structure in the tissues of macroalgae was modified using the sulfation pathway. A novel environmental friendly adsorbent Cu-BTC@Algal was synthesized by incorporated Cu-BTC nanoparticles onto sulphated-Macroalgae biomass under solvothermal conditions and characterized by XRD, FTIR, and N₂ adsorption-desorption isotherms. The removal rate of Cu-BTC@Algal was quite greater than that of Cu-BTC, showing that the adsorption performance of porous Cu-BTC can be improved through the modification of algal. Further study revealed that Cu-BTC@Algal exhibited a fast adsorption rate and selective adsorption ability towards the cationic dyes in aqueous solution. The removal rate was up to 97% for cationic dyes methylene blue (MB) and 68% for methyl orange (MO) at intervals 10 min. The influences including initial concentration, and contact time of MB/MO adsorption onto modified algal biomass, Cu-BTC and Cu-BTC@Algal were investigated in detail. The kinetic study indicated that the adsorption of MB/MO onto Cu-BTC@Algal followed the pseudo second-order model. The isotherm obtained from experimental data fitted the Langmuir model, yielding maximum adsorption capacity of 42, 73 and 162 mg g^-1 for algal, Cu-BTC and Cu-BTC@Algal, respectively.

Selective separation of hibiscus acid from Roselle extracts by an amino-functionalized Metal Organic Framework

The separation and purification of biologically-active compounds from natural sources is of interest because such molecules find wide application in the pharmaceutical sector and in other industrial areas. Roselle (Hibiscus sabdariffa) plants are a good source of anthocyanins, flavonoids, hydroxycitric acid, tartaric acid, ascorbic acid and hibiscus acid. The separation of hibiscus acid from the Roselle extract is very challenging, requiring the use of selective methods. It is accomplished here by means of the indium-bearing Metal Organic Framework MIL-68-NH₂. Before and after exposure to MIL-68-NH₂, the Roselle extract is analyzed by thin-layer chromatography, ultraviolet-visible spectrophotometry, gas chromatography-mass spectrometry, and high-performance liquid chromatography. The structural integrity of MIL-68-NH₂ after the separations is investigated by powder X-ray diffraction, nuclear magnetic resonance and infrared spectroscopy, confirming the adsorption selectivity of MIL-68-NH₂ towards hibiscus acid.

HKUST-1 modified ultrastability cellulose/chitosan composite aerogel for highly efficient removal of methylene blue

A novel composite HKUST-1/cellulose/chitosan aerogel (HKUST-1/CCSA) as an efficient adsorbent with hierarchical pores was prepared through a facile in situ growth way combining covalent cross-linking, vacuum freeze-drying, and solvothermal methods. By incorporating with cellulose (CE), covalently cross-linked cellulose (CE)/chitosan (CS) composite aerogel exhibits good stability, maintaining fine morphology and structures in acidic solutions under solvothermal conditions. Meantime, a high content of CS is beneficial to enhancing the growth of HKUST-1. Finally, the mass loading ratio of HKUST-1 is as high as 42.54 % in HKUST-1/CCSA. The BET specific surface area of HKUST-1/CCSA reaches 457.75 m² g^-1, which is much larger than that of CCSA (9.74 m² g^-1). HKUST-1/CCSA was applied to remove methylene blue with high adsorption capacity (526.3 mg g^-1) and good recycling capability. This strategy can provide an effective and facile pathway to prepare ultra-stable polysaccharide-based composite aerogel with high specific surface area and hierarchical pores, branching out more applications in pollutant treatment fields.

Recent Advances in Affinity MOF-Based Sorbents with Sample Preparation Purposes

This review summarizes the recent advances concerning metal-organic frameworks (MOFs) modified with several biomolecules (e.g., amino acids, nucleobases, proteins, antibodies, aptamers, etc.) as ligands to prepare affinity-based sorbents for application in the sample preparation field. The preparation and incorporation strategies of these MOF-based affinity materials were described. Additionally, the different types of ligands that can be employed for the synthesis of these biocomposites and their application as sorbents for the selective extraction of molecules and clean-up of complex real samples is reported. The most important features of the developed biocomposites will be discussed throughout the text in different sections, and several examples will be also commented on in detail.

Neoteric approach for efficient eco-friendly dye removal and recovery using algal-polymer biosorbent sheets: Characterization, factorial design, equilibrium and kinetics

A new approach of algal-polymer -sheets was performed by the embedding of two algal seaweeds (Ulva fasciata and Sargassum dentifolium) into cellulose acetate (CA) polymer forming two types of cellulose acetate; Ulva (CA-U) and Sargassum (CA-S) sheets. Afterward, the two sheets were characterized then subjected to 3-Rs evaluation (Removal, Recovery, and Reuse) of methylene blue dye (MB). Characterization data exhibited good properties for biosorption process. Algal biosorbents achieved more than twice biosorption capacity (Qmax) after the embedding into the polymer sheet. Additionally, according to factorial design data, the contact time and the dose of biosorbents had positive effects on the biosorption in the two sheets. Freundlich, Langmuir, and pseudo-second order models displayed good represented data in the two sheets. Furthermore, the two sheets (CA-U, followed by CA-S sheet) were successfully given more than 98% adsorption of 273 mg/l MB concentration. Moreover, the recovery and reuse data proved that the two sheets can be performed in good behavior for more than three cycles.

N-Aminorhodanine modified chitosan hydrogel for antibacterial and copper ions removal from aqueous solutions

A novel adsorbent based on N-Aminorhodanine modified chitosan hydrogel was synthesized and evaluated for antibacterial and copper ions removal from aqueous systems. N-Aminorhodanine was reacted with glutaraldehyde to yield Schiff base followed by reaction with chitosan to obtain the new hydrogel adsorbent. The new adsorbent was analyzed using FTIR, 1H NMR, XRD, TGA, HR-SEM and EDX in addition to the swelling behavior. The maximum adsorption capacities of chitosan and modified chitosan for copper ions were 38 and 62.5 mg/g respectively. The adsorption isotherm belongs Freundlich model and pseudo second order kinetics regime. The adsorption was reach to maximum within 15 min for modified chitosan hydrogel while take about 360 min for chitosan. Regeneration of adsorbent showed only 23% decline after 6 cycles which indicate the stability of the new adsorbent and it can be reused several times with good efficiency. N-Aminorhodanine modified chitosan hydrogel showed good activity towards gram positive bacteria.