Trifunctional metal–organic platform for environmental remediation: structural features with peripheral hydroxyl groups facilitate adsorption, degradation and reduction processes

A Cd(ii)-based metal–organic framework (MOF) has been demonstrated to have trifunctional properties, namely as an efficient and selective adsorbent for dyes, a visible-light-active photocatalyst for the degradation of dyes and a photocatalyst for Cr(vi) reduction.

Two-fold 2D + 2D → 2D interweaved rhombus (4,4) grid: synthesis, structure, and dye removal properties in darkness and in daylight

A rhombus (4,4) grid showing two-fold 2D + 2D → 2D interweaved nets appeared to be a good adsorbent to selectively adsorb and separate anionic methyl orange (MO) and acid orange 7 (AO7) dyes over cationic methylene blue (MB) and malachite green (MG) from water with high adsorption capacities in both darkness and daylight.

New multifunctional 3D porous metal–organic framework with selective gas adsorption, efficient chemical fixation of CO2 and dye adsorption

A new porous Mn(ii)-based MOF was obtained. The studies indicated it exhibits an effective storage capacity for CO₂, highly efficient catalyst behavior for epoxides with different substituents and rapid adsorption behavior of different dyes.

Removal of Arsenic(III) from Aqueous Solution Using Metal Organic Framework-Graphene Oxide Nanocomposite

MIL-53(Al)-graphene oxide (GO) nanocomposites of different GO to MIL-53(Al) mass ratios (1% to 25% GO) were synthesized and tested for removal of arsenite (As(III)), which is a well-known groundwater contaminant. The properties of MIL-53(Al)-GO nanocomposites were characterized using X-ray Diffraction (XRD), Fourier Transform Infrared (FT-IR) Spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, and Scanning Electron Microscopy (SEM). Batch experiments were performed on MIL-53(Al)-GO nanocomposites for As(III) adsorption in aqueous solutions to investigate adsorption kinetics and isotherm behavior under varying environmental conditions. The effects of solution pH (2 to 11), initial As(III) concentrations (10–110 mg/L), adsorbent dosage (0.2–3.0 g/L), and temperature (298–318 K) on As(III) adsorption were investigated. MIL-53(Al)-GO nanocomposites showed higher adsorption of As(III) than pristine MIL-53(Al) and GO individually. As (III) removal was optimized at a ratio of 3% GO in the MIL-53(Al)-GO nanocomposite, with an adsorption capacity of 65 mg/g. The adsorption kinetics and isotherms followed pseudo-second-order and Langmuir isotherm models, respectively. Overall, these results suggest that MIL-53(Al)-GO nanocomposite holds a significant promise for use in the remediation of As (III) from groundwater and other aqueous solutions.

Rapid ultrasound assisted hydrothermal synthesis of highly pure nanozeolite X from fly ash for efficient treatment of industrial effluent

Nanoporous green materials like nanozeolite has been in focus for their superb efficiency to treat industrial wastewater. The study reports ultrasound assisted hydrothermal method as a very fast method to convert industrial fly ash from different sources of eastern India to nanozeolite X for efficient removal of toxic dyes and metals from industrial effluent. The pure nanosized zeolite X was synthesized rapidly at 20 min of ultrasound treatment after alkali fusion. The efficiency of nanozeolite X was determined in terms of the adsorption capacity towards various divalent ions such as Zn²⁺, Cu²⁺, Cd²⁺, Pb²⁺, Ni²⁺, Ca²⁺, and Mg²⁺ as well as various dyes such as methylene blue, crystal violet, indigo carmine, and Congo red. In comparison to commercially available microporous Zeolite X (a maximum of 120.43 mg g^-1 for Pb²⁺ and 134.62 mg g^-1 by for methylene blue), all synthesized nanozeolite X shows high adsorption capacity for metals (a maximum of 196.24 mg g^-1 for Pb²⁺) as well as dyes (193.45 mg g^-1 for methylene blue). Highly pure nanozeolite X has shown immense potential for treatment of real time industrial wastewater.

Efficient Capture of Organic Dyes and Crystallographic Snapshots by a Highly Crystalline Amino-Acid-Derived Metal-Organic Framework

The presence of residual organic dyes in water resources or wastewater treatment systems, derived mainly from effluents of different industries, is a major environmental problem with no easy solution. Herein, an ecofriendly, water-stable metal-organic framework was prepared from a derivative of the natural amino acid l-serine. Its functional channels are densely decorated with highly flexible l-serine residues bearing hydroxyl groups. The presence of such a flexible and functional environment within the confined environment of the MOF leads to efficient removal of different organic dyes from water: Pyronin Y, Auramine O, Methylene Blue and Brilliant Green, as unveiled by unprecedented snapshots offered by single-crystal X-ray diffraction. This MOF enables highly efficient water remediation by capturing more than 90 % of dye content, even at very low concentrations such as 10 ppm, which is similar to those usually found in industrial wastewaters. Remarkably, the removal efficiency is improved in simulated contaminated mineral water with multiple dyes.

Simultaneous removal of cationic methylene blue and anionic reactive red 198 dyes using magnetic activated carbon nanoparticles: equilibrium, and kinetics analysis

For the simultaneous adsorption of cationic dye (methylene blue, MB) and anionic dye (reactive red 198, RR198) from aqueous solution, magnetic activated carbon (MAC) nanocomposite as a promising adsorbent was prepared and used. The concentration of MB at different time intervals was determined using a UV-Vis spectrophotometer while the concentration of RR198 was determined using a high performance liquid chromatography (HPLC) system. The effect of solution pH, contact time, adsorbent amount, and dye concentration were investigated. Also, both kinetic and isotherm experiments were studied. The optimum pH was 10 and 5.5 for adsorption of MB and RR198, respectively, and the equilibrium status was achieved after 120 min. The adsorption kinetics was controlled by the pseudo-second order kinetic model more than pseudo-first order. The best-fitted isotherms were Freundlich and Langmuir models for MB and RR198, respectively. The higher values of Freundlich adsorption capacity (K_f) for MB in comparison with RR198 refer to MAC affinity to remove cationic dyes more than anionic dyes. Apparently, there was no substantial change in the adsorption efficiency among the 10 adsorption-desorption cycles. Overall, MAC can be considered as an effective and efficient viable adsorbent for cationic and anionic dyes removal from industrial wastewaters.

A Fully Noble Metal-Free Photosystem Based on Cobalt-Polyoxometalates Immobilized in a Porphyrinic Metal-Organic Framework for Water Oxidation

The sandwich-type polyoxometalate (POM) [(PW₉O₃₄)₂Co₄(H₂O)₂]^10- was immobilized in the hexagonal channels of the Zr(IV) porphyrinic MOF-545 hybrid framework. The resulting composite was fully characterized by a panel of physicochemical techniques. Calculations allowed identifying the localization of the POM in the vicinity of the Zr₆ clusters and porphyrin linkers constituting the MOF. The material exhibits a high photocatalytic activity and good stability for visible-light-driven water oxidation. It thus represents a rare example of an all-in-one fully noble metal-free supramolecular heterogeneous photocatalytic system, with the catalyst and the photosensitizer within the same porous solid material.

A new set of Cd(ii)-coordination polymers with mixed ligands of dicarboxylate and pyridyl substituted diaminotriazine: selective sorption towards CO2and cationic dyes

Pyridyl substituted diaminotriazine based three new Cd(ii)-CPs have been synthesized. CP3showed its potential for CO₂/N₂and CO₂/CH₄separation selectivity and its ability for selective adsorption to a cationic dye.