Selective adsorption of anionic and cationic dyes on mesoporous UiO-66 synthesized using a template-free sonochemistry method: kinetic, isotherm and thermodynamic studies

Innovative nanocomposites for pollutant capture: Adsorption of rhodamine B dye using polyaniline-coated chitosan trisodium citrate nanocomposites

Wastewater contamination by organic dyes, especially Rhodamine B (RhB), possess a significant environmental challenge. This study explores a novel bio sorbent for the removal of RhB dye from contaminated water, using chitosan trisodium citrate-modified magnetic nanoparticles (Fe₃O₄@CSTSC@PANI) coated with polyaniline. The nanocomposite was characterized by FT-IR, XRD, HRTEM, SEM, BET surface analysis. The UV-visible spectroscopy was used to monitor the adsorption of dye on the nanocomposite. The Fe₃O₄@CSTSC@PANI nanocomposite exhibits a spherical core-shell morphology with a size range of 29-53 nm, a BET surface area of 13.099 m2/g, and high reusability. The pore area of the material increased from 0.8058 m2/g at 15.29 Å radius to 10.65 m2/g at 1310.89 Å, with a corresponding change in pore volume from 0.0006.16 cc/g to 0.0227 cc/g. This shows the significant contribution of the porous and mesoporous structures of polyaniline-coated chitosan trisodium citrate (nanocomposites) to the adsorption performance for pollutant capture such as Rhodamine B dye. Adsorption studies showed optimal RhB removal of 97.2 % at near neutral pH. Adsorption was most optimal at pH 6-9, with the highest efficiency near neutral pH, which facilitates electrostatic interactions. High temperature (10-70 °C) promoted the endothermic adsorption process, improving the dye uptake. The optimal adsorbent dosage (0.21-1.6 g/L) and equilibrium contact time (30-840 min) were determined. The nanocomposite material showed good recovery, maintaining high efficiency after 4 reuse cycles, demonstrating its practicality in sustainable environmental remediation. The adsorption mechanism was elucidated by isotherm and kinetic studies, which revealed that the process followed a pathway dominated by chemisorption facilitated by the interaction between polyaniline-coated chitosan nanocomposites and Rhodamine B dye molecules. This is the synergistic effect of electrostatic attraction, hydrogen bonding and π-π interactions, confirming the strong affinity of the mixture for the dye.

Cost-effective adsorption of cationic dyes using ZnO nanorods supported by orange peel-derived carbon

Here, porous carbon (PC) and ZnO nanorods@PC (ZnO-NR@PC) composite derived from orange peel (OP) have been synthesized via a simple carbonization process. The prepared materials have been characterized by XRD, FT-IR, TEM, and BET analysis. The adsorptive properties of the prepared PC and ZnO-NR@PC composite have been investigated toward methylene blue (MB) and crystal violet (CV) cationic dyes from their aqueous solutions. The adsorption studies concluded that the maximum adsorption efficiency was achieved after 90 min in the basic conditions (pH = 10). Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin non-linear isotherm models were applied to fit the experimental data. The adsorption of MB and CV dyes by the OP is fitted with the Freundlich model, and the adsorption of both dyes by the PC and the ZnO-NR@PC composite fitted with the Langmuir model. The estimated maximum adsorption capacity estimated from the adsorption of MB and CV by the ZnO-NR@PC composite was 74.45 and 74.89 mg/g, respectively. The calculated adsorption free energy from D-R and Temkin models indicates the adsorption of MB, and CV dye molecules by the OP, PC, and ZnO-NR@PC composite may be physical. The kinetic studies revealed the adsorption of MB and CV dyes onto the OP, PC and ZnO-NR@PC composite fitted with the pseudo-second-order model. On the otherhand, the thermodynamic studies confirmed the adsorption of MB, and CV dyes onto ZnO-NR@PC composite is an endothermic and spontaneous process. Furthermore, the prepared materials displayed high adsorption stability with an overall removal efficiency of about 90% after five cycles. The mechanism of MB and CV dyes by the ZnO-NR@PC composite is proposed to be controlled by electrostatic bonding, π-π interactions, and ion exchange. The results indicated the potential ability of OP-derived porous carbons as adsorbents for cationic dyes from aqueous media.

Coupling UiO-66 MOF with a Nanotubular Oxide Layer Grown on Ti-W Alloy Accelerates the Degradation of Hormones in Real Water Matrices

To enable the photoelectrocatalytic treatment of large volumes of water containing low concentrations of pollutants, this study introduces a hybrid photocatalyst, composed of nanotubular oxides grown on TixW alloy (x = 0.5 and 5.0 wt %) modified with UiO-66 MOF, for degradation of estrone (E1) and 17α-ethinyl estradiol (EE2). The oxide layer (Nt/TixW) was prepared via anodization, while UiO-66 nanoparticles were synthesized by using a solvothermal process. Different techniques for modifying nanotubular oxides were evaluated to maximize the photocatalytic activity and the sorption process. In photo(electro)catalytic experiments using low concentrations of E1 and EE2 synthetic solutions and UV-vis radiation (100 W/cm2), all modified materials exhibited approximately 40% higher degradation compared to the unmodified photocatalyst, keeping the same sequential performance of the photocatalysts (Nt/TiO2 < Nt/Ti-0.5W < Nt/Ti-5.0W) independent of the treatment. This enhancement was attributed to the MOF's increased hormone sorption, with no synergistic interaction observed between the photocatalyst and the adsorbent. In real water supply matrices, the photoelectrocatalytic removal rate of E1 using Nt/Ti-5.0W modified UiO-66 under UV-vis radiation and 1.3 V was 0.168 s-1, while for EE2, it was 0.310 min-1, approximately 1.78 and 18.21 times faster than obtained with the unmodified photocatalyst. The slower degradation rate of EE2 compared to that of E1 is attributed to the formation of denser intermediates that compete with smaller organic molecules in the real matrix. The cooperative effect between NT/TixW and UiO-66 favored the confinement of pollutants and by-products within the UiO-66 cavity, minimizing the diffusion effects and promoting the degradation of these compounds by the OH· radical generated at the oxide/solution interface. Among the tested electrodes, NT/Ti5W modified with UiO-66 demonstrated the highest efficiency and stability during the recycle tests. This highlights its promise for applications in photocatalytic processes for treating water supplies with low pollutant concentrations.

UiO-66 MOF/Zr-di-terephthalate/cellulose hybrid composite synthesized via sol-gel approach for the efficient removal of methylene blue dye

This research addresses the issue of organic dye pollution in water by developing eco-friendly, cost-effective adsorbents. Zr-di-terephthalate organic-inorganic hybrid materials, with and without cellulose, were synthesized using a one-pot sol-gel method with zirconium butoxide and terephthalic acid. The materials were characterized by XRD, FTIR, XPS, SEM, EDS, TEM, and BET analysis and showed a crystalline structure with some amorphous content, high surface area, and small pores, indicative of a composite form containing UiO-66 metal-organic frameworks (MOFs). Adsorption studies on methylene blue dye showed that both materials followed Langmuir isotherms, with maximum adsorption capacities of 147.54 mg/g for Zr-(TPA)2-U and 151.38 mg/g for Zr-(TPA)2-UC. The materials exhibited rapid adsorption within a short period of 30 min and adhered to pseudo-second order kinetics. The adsorption process was spontaneous and endothermic, driven by electrostatic interactions, π-π stacking, pore filling, van der Waals forces, and hydrogen bonding. The fact that the composite materials contain the UiO-66 structure contributed to their effective adsorption by increasing the crystalline properties of the material. The hybrids also showed excellent reusability, maintaining high efficiency over multiple cycles. These findings highlight the potential of Zr-di-terephthalate hybrids as sustainable, high-performance adsorbents for water purification, addressing dye contamination effectively.

Enhanced adsorption of carbon sphere by doping with titania nanotubes for crystal violet removal: isotherm, kinetics, and thermodynamic studies

In this study, the carbon sphere (Cs) has been prepared and modified by titania nanotubes (TNTs) to be utilized as an adsorbent toward crystal violet (CV) dye as a model for cationic dyes from aqueous solution. The prepared TNTs@Cs composites has been characterized by various techniques such as XRD, SEM, and TEM analysis. The adsorption analysis displayed that the adsorption capacity of CV dye onto the modified Cs with TNTs is 92.5 mg g-1, which is much higher than that achieved by pristine Cs (12.5 mg g-1). Various factors that influence the overall adsorption processes, such as pH, contact time, initial CV dye concentration, adsorbent weight, and temperature, were studied. The TNTs@Cs76.7 composite showed the highest removal percentage of 99.00% at optimum conditions. The adsorption isotherm analysis showed that the experimental data of adsorption CV dye fitted better with the Langmuir isotherm model with R 2 of 0.999, and the estimated maximum adsorption capacity was 84.7 mg g-1. On the other hand, the adsorption kinetic study showed that the adsorption of CV follows the pseudo-second order kinetic model with an equilibrium adsorption capacity (q e) of 10.66, 18.622, 47.61, and 48.31 mg g-1 for Cs, TNTs@Cs93, TNTs@Cs86.8, and TNTs@Cs76.7 composites, respectively. The thermodynamic analysis showed negative free energy (ΔG) values, this indicates that the adsorption of CV is a spontaneous and feasible process. Furthermore, the ΔH and ΔS are positive values that indicate an endothermic adsorption process. Furthermore, the prepared TNTs@Cs76.7 composite displayed remarkable adsorption stability and the removal efficiency of CV remains at 96.3% after five cycles.

Synergistic Effect of UiO-66 Directly Grown on Kombucha-Derived Bacterial Cellulose for Dye Removal

Metal-Organic Frameworks (MOFs) are particularly attractive sorbents with great potential for the removal of toxic dye pollutants from industrial wastewaters. The uniform dispersion of MOF particles on suitable substrates then represents a key condition to improve their processability and provide good accessibility to the active sites. In this work, we investigate the efficiency of a natural bacterial cellulose material derived from Kombucha (KBC) as an active functional support for growing and anchoring MOF particles with UiO-66 structures. An original hierarchical microstructure was obtained for the as-developed Kombucha cellulose/UiO-66 (KBC-UiO) composite material, with small MOF crystals (~100 nm) covering the cellulose fibers. Promising adsorption properties were demonstrated for anionic organic dyes such as fluorescein or bromophenol blue in water at pH 5 and pH 7 (more than 90% and 50% removal efficiency, respectively, after 10 min in static conditions). This performance was attributed to both the high accessibility and uniform dispersion of the MOF nanocrystals on the KBC fibers together with the synergistic effects involving the attractive adsorbing properties of UiO-66 and the surface chemistry of KBC. The results of this study provide a simple and generic approach for the design of bio-sourced adsorbents and filters for pollutants abatement and wastewater treatment.

Preparation of UiO-66 loaded Letrozole nano-drug delivery system: enhanced anticancer and apoptosis activity

The use of drug delivery systems in targeting and achieving the targeting of drugs in treating diseases, especially cancer, has attracted the attention of researchers. Letrozole is one of the drugs for the treatment of breast cancer. In this study, the organic-metallic pharmaceutical porous nanostructure based on zirconium UiO-66 loaded letrozole was synthesized. Its cytotoxicity and effect on apoptosis and migration against breast cancer cell line were investigated. In this experimental study, the UiO-66 nanoparticle-loaded letrozole was synthesized using zirconium chloride (ZrCl4), dimethylformamide (DMF), and HCl. Its characteristics were determined by scanning electron microscopy, and its average size was determined by the DLS method. Also, the rate of letrozole drug release from the nanoparticle was investigated in 24, 48, and 72 h. In addition, its cytotoxicity effects were investigated using the MTT colorimetric method at concentrations of 3.125-100 µg/ml against the breast cancer cell line (MCF-7) in the periods of 48 and 72 h. Also, the expression level of apoptotic genes Bax and Bcl2 was investigated by the Real-Time PCR method. Also, the amount of cell migration was done by the migration assay method. The results showed that UiO-66 bound to letrozole had a spherical morphology and an average size of 9.2 ± 160.1. Also, the letrozole drug was loaded by 62.21 ± 1.80% in UiO-66 nanoparticles and had a slower release pattern than free letrozole in the drug release test, so within 72 h, 99.99% of free letrozole was released in If in UiO-66 containing letrozole, 57.55% of the drug has been released. Also, the cytotoxicity results showed that UiO-66 bound to letrozole has more significant cytotoxic effects than free letrozole (p < 0.05). Also, the results of Bax and Bcl2 gene expression showed that the treatment of MCF-7 cells with UiO-66 nanoparticles attached to letrozole increased the expression of Bax and Bcl2 genes compared to the reference gene Beta-actin in MCF-7 cell line, respectively. (p < 0.05) increased by 3.71 ± 0.42 and (p < 0.01) decreased by 0.636 ± 0.034 (p < 0.05). Cell migration results showed that the concentration of 50 µg/ml of UiO-66 bound to letrozole decreased the migration of MCF-7 cells. Generally, the results of this study showed that UiO-66 loaded letrozole can be used as a suitable drug carrier for cellular purposes, as it has increased the effects of cytotoxicity and the rate of apoptosis in breast cancer cell line (MCF-7), so it can be used with more studies used nanocarriers as a drug delivery system.

ZnO@ activated carbon derived from wood sawdust as adsorbent for removal of methyl red and methyl orange from aqueous solutions

Activated carbon (AC) and ZnO@AC composite derived from wood sawdust were prepared to be utilized as adsorbents for methyl red (MR) and methyl orange (MO) anionic dyes from the aqueous solutions. The maximum adsorption capacity of the AC and ZnO@AC composite toward both dyes was achieved in the strong acidic medium (pH = 3), and under stirring for 60 min. The kinetic studies revealed that the adsorption of MR and MO dyes onto the AC and ZnO@AC composite fitted well with the pseudo-second-order model. Furthermore, the intraparticle diffusion and Elovich kinetic models confirmed the adsorption is controlled by external surfaces, and the adsorption is chemisorption process. The isotherm results indicated that the MR and MO dye adsorption occurred via monolayer adsorption, and the estimated maximum adsorption capacities of both dyes onto the ZnO@AC composite were higher than those achieved by AC. Thermodynamic analysis suggested that the adsorption is endothermic and spontaneous. The mechanism for MR, and MO dyes adsorption onto the AC and ZnO@AC composite is proposed to be controlled by electrostatic bonding, π-π interactions, and ion exchange, while H-bonding and n-π interactions were minor contributors. This study reveals the potential use of carbon-based adsorbents derived from wood sawdust for the removal of anionic dyes from wastewater.

Adsorption and decolorization study of reactive black 5 by immobilized metal-organic framework of UiO-66 and Gloeophyllum trabeum fungus

This study aimed to investigate immobilized metal-organic framework (MOF) UiO-66 and brown-rot fungus Gloeophyllum trabeum (GT) in PVA-SA matrices for adsorption and decolorization of reactive black 5 (RB5). Furthermore, UiO-66/GT@PVA-SA composite was successfully fabricated and obtained by immobilizing UiO-66 and GT mycelia into a mixture of PVA-SA. This composite demonstrated a decolorization ability of 80.12% for RB5 after 7 days. The composite's reusability was assessed for three cycles; at last, it only achieved 21%. This study reported that adsorption of RB5 by the composite followed a pseudo-second-order kinetic model with a correlation coefficient (R2) of 0.9997. The Freundlich model was found to be suitable for the isotherm adsorption. The process was also spontaneous and feasible, as indicated by the negative ΔG value. Subsequently, four metabolite products resulting from decolorization of RB5 by UiO-66/GT@PVA-SA composite were proposed, namely: C24H19N5Na2O13S4 (m/z = 762), C10H13N2O8S2- (m/z = 353), C12H9N4O7S2- (m/z = 384), and C10H13O8S2- (m/z = 325).