Metal-organic frameworks for wastewater treatment: Recent developments, challenges, and future prospects

A review on titanium oxide nanoparticles modified metal-organic frameworks for effective CO2 conversion and efficient wastewater remediation

Environmental pollution has been increasing since last decade due to increasing industrialisation and urbanisation. Various kinds ofenvironmental pollutants including carbon dioxide (CO2), dyes, pharmaceuticals, phenols, heavy metals along with many organic and inorganic species have been discovered in the various environmental compartments which possess harmful impacts tox human health, wildlife, and ecosystems. Thus, various efforts have been made through regulations, technological advancements, and public awareness campaigns to reduce the impact of the pollution. However, finding suitable alternatives to mitigate their impacts remained a challenge. Metal-organic frameworks (MOFs) are one of the advanced materials with unique features such as high porosity and stability which exhibit versatile applications in environmental remediation. Their composites with titanium oxide nanoparticles (TiO2) have been discovered to offer potential feature such as light harvesting capacity and catalytic activity. The composite integration and properties have been confirmed through characterization using surface area analysis, scanning electron/transmission electron microscopy, atomic force microscopy, fourier transformed infrared spectroscopy, X-ray diffraction analysis, X-ray photoelectron spectroscopy, thermogravimetric analysis, and others. Thus, this work rigorously discussed potential applications of the MOF@TiO2 nanomaterials for the CO2 capture and effective utilization in methanol, ethanol, acetone, acetaldehyde, and other useful products that served as fuel to various industrial processes. Additionally, the work highlights the effective performance of the materials towards photocatalytic degradation of both organic and inorganic pollutants with indepth mechanistic insights. The article will offer significant contribution for the development of sustainable and efficient technologies for the environmental monitoring and pollution mitigation.

Emerging iron-based mesoporous materials for adsorptive removal of pollutants: Mechanism, optimization, challenges, and future perspective

Iron-based materials (IBMs) have shown promise as adsorbents due to their unique physicochemical properties. This review provides an overview of the different types of IBMs, their synthesis methods, and their properties. Results found in the adsorption of emerging contaminants to a wide range of IBMs are discussed. The IBMs used were evaluated in terms of their maximum uptake capacity, with special consideration given to environmental conditions such as contact time, solution pH, initial pollutant concentration, etc. The adsorption mechanisms of pollutants are discussed taking into account the results of kinetic, isotherm, thermodynamic studies, surface complexation modelling (SCM), and available spectroscopic data. A current overview of molecular modeling and simulation studies related to density functional theory (DFT), surface response methodology (RSM), and artificial neural network (ANN) is presented. In addition, the reusability and suitability of IBMs in real wastewater treatment is shown. The review concludes with the strengths and weaknesses of current research and suggests ideas for future research that will improve our ability to remove contaminants from real wastewater streams.

Efficient Removal of Hazardous P-Nitroaniline from Wastewater by Using Surface-Activated and Modified Multiwalled Carbon Nanotubes with Mesostructure

P-nitroaniline (PNA) is an aniline compound with high toxicity and can cause serious harm to aquatic animals and plants. Multiwalled carbon nanotubes (MWCNTs) are a multifunctional carbon-based material that can be applied in energy storage and biochemistry applications and semiconductors as well as for various environmental purposes. In the present study, MWCNTs (CO2-MWCNTs and KOH-MWCNTs) were obtained through CO2 and KOH activation. ACID-MWCNTs were obtained through surface treatment with an H2SO4-HNO3 mixture. Herein, we report, for the first time, the various MWCNTs that were employed as nanoadsorbents to remove PNA from aqueous solution. The MWCNTs had nanowire-like features and different tube lengths. The nanotubular structures were not destroyed after being activated. The KOH-MWCNTs, CO2-MWCNTs, and ACID-MWCNTs had surface areas of 487, 484, and 80 m2/g, respectively, and pore volumes of 1.432, 1.321, and 0.871 cm3/g, respectively. The activated MWCNTs contained C-O functional groups, which facilitate PNA adsorption. To determine the maximum adsorption capacity of the MWCNTs, the influences of several adsorption factors-contact time, solution pH, stirring speed, and amount of adsorbent-on PNA adsorption were investigated. The KOH-MWCNTs had the highest adsorption capacity, followed by the CO2-MWCNTs, pristine MWCNTs, and ACID-MWCNTs. The KOH-MWCNTs exhibited rapid PNA adsorption (>85% within the first 5 min) and high adsorption capacity (171.3 mg/g). Adsorption isotherms and kinetics models were employed to investigate the adsorption mechanism. The results of reutilization experiments revealed that the MWCNTs retained high adsorption capacity after five cycles. The surface-activated and modified MWCNTs synthesized in this study can effectively remove hazardous pollutants from wastewater and may have additional uses.

Novel Hydrophobic Functionalized UiO-66 Series: Synthesis, Characterization, and Evaluation of Their Structural and Physical-Chemical Properties

A novel set of four functionalized hydrophobic UiO-66-NHR series were synthesized through postsynthetic procedures, utilizing various benzoyl chlorides and UiO-66-NH2 as starting materials. This synthesis method was carried out by employing p- (1) and o-toluoyl (2), as well as 2- (3) and 4-fluorobenzoyl (4) substituents. The analysis of the resulting compounds was performed using conventional spectroscopic methods such as FT-IR and 1H NMR to quantify the conversion rate into amide. Furthermore, SEM and XPS techniques were employed for morphological and surface analysis. Finally, the evaluation of the chemical stability and contact angle using the sessile drop method was performed to evaluate the technological potential of these compounds for application in aqueous and acidic media (such as selective separation of different metals and wastewater recovery).