Synthesis of novel zeolitic imidazolate framework (ZIF-67) – zinc oxide (ZnO) nanocomposite (ZnO@ZIF-67) and potential adsorption of pharmaceutical (tetracycline (TCC)) from water

Tetracycline decontamination from aqueous media using nanocomposite adsorbent based on starch-containing magnetic montmorillonite modified by ZIF-67

In the present study, starch/zeolitic imidazole framework-67 (ZIF-67) modified magnetic montmorillonite nanocomposite adsorbent to remove tetracycline (TC) as an emerging antibiotic-based contaminant from aqueous media. The surface properties of the adsorbents were investigated using FTIR, XRD, SEM, EDX-Map, XPS, TEM, BET, and VSM analysis. The specific surface area of MMT, St/MMT-MnFe2O4, and St/MMT-MnFe2O4-ZIF-67 magnetic nanocomposite samples were found to be 15.63, 20.54, and 588.41 m2/g, respectively. The influence of pH, adsorbent amount, initial TC concentration, temperature, contact time, and coexisting ions on TC elimination was explored in a batch adsorption system. The kinetic and equilibrium data were well matched with the pseudo-second-order and Langmuir isotherm models, respectively. The maximum monolayer adsorption capacities of TC were obtained to be 40.24, 66.1, and 135.2 mg/g by MMT, St/MMT-MnFe2O4, and St/MMT-MnFe2O4-ZIF-67 magnetic nanocomposite adsorbents, respectively. Also, thermodynamic studies illustrated that the TC adsorption process is exothermic and spontaneous. Furthermore, the magnetic nanocomposite adsorbent St/MMT-MnFe2O4-ZIF-67 showed good reusability and could be recycled for up to five cycles. This excellent adsorption performance, coupled with the facile separation of the magnetic nanocomposite, gave St/MMT-MnFe2O4-ZIF-67 a high potential for TC removal from aqueous media.

Removal of p-Nitrophenol by Adsorption with 2-Phenylimidazole-Modified ZIF-8

Petrochemical wastewater contains p-nitrophenol, a highly toxic, bioaccumulative and persistent pollutant that can harm ecosystems and environmental sustainability. In this study, ZIF-8-PhIm was prepared for p-nitrophenol removal from petrochemical wastewater using solvent-assisted ligand exchange (SALE) with 2-phenylimidazole(2-PhIm). The ZIF-8-PhIm's composition and structure were characterised using the XRD, SEM, FT-IR, ¹H NMR, XPS and BET methods. The adsorption effect of ZIF-8-PhIm on p-nitrophenol was investigated with the static adsorption method. Compared to the ZIF-8 materials, ZIF-8-PhIm exhibited stronger π-π interactions, produced a multistage pore structure with larger pore capacity and size, and had increased hydrophilicity and exposure of adsorption sites. Under optimised conditions (dose = 0.4 g/L, T = 298 K, C₀ = 400 mg/L), ZIF-8-PhIm achieved an adsorption amount of 828.29 mg/g, which had a greater p-nitrophenol adsorption capacity compared to the ZIF-8 material. The Langmuir isotherm and pseudo-second-order kinetic models appropriately described the p-nitrophenol adsorption of ZIF-8-PhIm. Hydrogen bonding and π-π interactions dominated the p-nitrophenol adsorption of ZIF-8-PhIm. It also had relatively good regeneration properties.

Bentonite binding with mercury(II) ion through promotion of reactive oxygen species derived from manure-based dissolved organic matter

This study reports the mercury binding by bentonite clay influenced by cattle manure-derived dissolved organic matter (DOM). The DOM (as total organic carbon; TOC) was reacted with bentonite at 5.2 pH to monitor the subsequent uptake of Hg²⁺ for 5 days. The binding kinetics of Hg²⁺ to the resulting composite was studied (metal = 350 µM/L, pH 5.2). Bentonite-DOM bound much more Hg²⁺ than original bentonite and accredited to the establishment of further binding sites. On the other hand, the presence of DOM was found to decrease the Hg²⁺ binding on the clay surface, specifically, the percent decrease of metal with increasing DOM concentration. Post to binding of DOM with bentonite resulted in increased particle size diameter (~ 33.37- ~ 87.67 nm) by inducing the mineral modification of the pore size distribution, thus increasing the binding sites. The XPS and FTIR results confirm the pronounced physico-chemical features of bentonite-DOM more than that of bentonite. Hydroxyl and oxygen vacancies on the surface were found actively involved in Hg²⁺ uptake by bentonite-DOM composite. Furthermore, DOM increased the content of Hg²⁺ binding by ~ 10% (pseudo-second-order q_e = 90.9-100.0) through boosting up Fe³⁺ reduction with the DOM. The quenching experiment revealed that more oxygen functionalities were generated in bentonite-DOM, where hydroxyl was found to be dominant specie for Hg²⁺ binding. The findings of this study can be used as theoretical reference for mineral metal interaction under inhibitory or facilitating role of DOM, risk assessment, management, and mobilization/immobilization of mercury in organic matter-containing environment.

Facile Synthesis of ZIF-67 for the Adsorption of Methyl Green from Wastewater: Integrating Molecular Models and Experimental Evidence to Comprehend the Removal Mechanism

Organic dyes with enduring colors which are malodorous are a significant source of environmental deterioration due to their virulent effects on aquatic life and lethal carcinogenic effects on living organisms. In this study, the adsorption of methyl green (MG), a cationic dye, was achieved by using ZIF-67, which has been deemed an effective adsorbent for the removal of contaminants from wastewater. The characterization of ZIF-67 was done by FTIR, XRD, and SEM analysis. The adsorption mechanism and characteristics were investigated with the help of control batch experiments and theoretical studies. The systematical kinetic studies and isotherms were sanctioned with a pseudo-second-order model and a Langmuir model (R² = 0.9951), confirming the chemisorption and monolayer interaction process, respectively. The maximum removal capacities of ZIF-67 for MG was 96% at pH = 11 and T = 25 °C. DFT calculations were done to predict the active sites in MG by molecular electrostatic potential (MEP). Furthermore, both Molecular dynamics and Monte Carlo simulations were also used to study the adsorption mechanism.

Extraction and separation feasibility of cerium (III) and lanthanum (III) from aqueous solution using modified graphite adsorbent

Graphite (GR) and graphite/alginate (GRA) composite were synthesized utilizing the thermal annealing technique and used as a new adsorbent material for the selective separation and removal of La(III) and Ce(III) from aqueous solutions. Fourier transform infrared (FTIR) spectroscopy, thermal analysis (DTA, TGA), X-ray diffraction (XRD), surface area, porosity, and scanning electron microscope (SEM) were also used to characterize the generated material. Distinct experiments were performed to test the ability of the GRA to La(III) and Ce(III) removal, which include the effect of pH, shaken time, initial concentration of La(III), and Ce(III) at different temperatures range. After 20 min, both ions have reached equilibrium. The pseudo second-order kinetic model was chosen as one which best fits the experimental evidence and better reflects the chemical sorption process. Adsorption isotherm was studied using the Langmuir, Freundlich, and D-R models. The Langmuir model was used to better fit the results obtained. At 25 °C, Ce(III) and La(III) have maximum monolayer capacities of 200 and 83.3 mg/g, respectively. The sorption was endothermic reaction and spontaneous, as illustrated by the data of thermodynamics studies. GRA has the ability to be used as a novel lanthanide adsorbent material, especially for selective separation between Ce(III) and La(III).

Construction of WO3 nanocubes@Loess for rapid photocatalytic degradation of organics in wastewater under sunlight

In nowadays, environmental pollution has been greatly improved, but the development of low-cost and environmentally friendly materials are still challenge in the field of water treatment. Herein, a cheap and eco-friendly natural loess particle (LoP) was used for in situ growth of tungsten trioxide nanocubes (WO3NCs) on its surface via a simple one-pot hydrothermal method, which afforded a stable loess-based photocatalyst (WO3NCs@LoP). It was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) analysis, UV-Vis diffuse reflectance spectra (UV-Vis DRS), and X-ray photoelectron spectroscopy (XPS). The photocatalytic performances of WO3NCs@LoP were applied to photodegradation of organics under visible-light illumination. It was found that the removal rate of methylene blue (MB) got to 99% within 20 min, which was higher than that of materials, such as pure LoP and WO3NCs. Moreover, the photocatalytic activity of WO3NCs@LoP remained 85% after 9 cycling times, indicating its high stability and reusability. It was suggested that the synergy of the well narrowed band gap and effectual control of e--h+ recombination in WO3NCs@LoP improve its photodegradation efficiency. In summary, using natural minerals (LoP) as carrier, a novel eco-friendly photocatalyst could be explored for photodegradation of organic pollutions in wastewater treatment.

Removal of arsenic by metal organic framework/chitosan/carbon nanocomposites: Modeling, optimization, and adsorption studies

In this work removal of the arsenic (As) spiked in water through adsorption using synthesized nanocomposites as a adsorbent. The Zn-BDC@chitosan/carbon nanotube (Zn-BDC@CT/CNT) and Zn-BDC@chitosan/graphene oxide (Zn-BDC@CT/GO) were synthesized from metal organic framework, carbon nanotube/graphene oxide and natural polysaccharide. Results of adsorption experiments showed that the Zn-BDC@CT/GO possessed a higher adsorption capacity than that of the Zn-BDC@CT/CNT. A study on the adsorption of As onto Zn-BDC@CT/GO was conducted and the process parameters were optimized by response surface methodology (RSM). A five-level, four-factor central composite design (CCD) has been used to determine the effect of various process parameters on As uptake from aqueous solution. By using this design a total of 20 adsorption experimental data were fitted. The regression analysis showed good fit of the experimental data to the second-order polynomial model with coefficient of determination (R²) value of 0.9997 and model F-value of 1099.97. The adsorption matched with the pseudo-second-order model and the Freundlich model. The thermodynamic parameters revealed that the nature of adsorption was feasible, spontaneous and endothermic process. Adsorption of As in the presence of other competitive ions was not significantly affected The effective adsorption performance also sustained even after ten adsorption-desorption cycles, indicating favorable reusability.