Improving ZIF-8 stability in the preparation process of polyimide-based organic solvent nanofiltration membrane

Eco-friendly hydrophobic ZIF-8/sodium alginate monolithic adsorbent: An efficient trap for microplastics in the aqueous environment

Microplastics (MPs), a newly emerging class of environmental contaminants, pose a severe threat to the entire ecosystem. The development of efficient and environmentally responsible adsorbents for removing the MPs is a particularly urgent research. Herein, a kind of monolithic ZIF-8 based adsorbents featuring stable hydrophobicity and micropore-mesopore-macropore hierarchical porous structure were fabricated by in situ growth of ZIF-8 nanoparticles on sodium alginate (SA) framework, and using polydimethylsiloxane (PDMS) as a hydrophobic agent. The monolithic nature of ZIF-8/SA allowed an easy solid-liquid separation process for adsorbents from water environment compared to powdered materials. The hierarchical porous structure ensures a remarkable MPs removal performance. The ZIF-8/SA showed high adsorption capacities of 594, 585, and 282 mg/g for polymethyl methacrylate (PMMA), poly (vinylidene difluoride) (PVDF), and polyvinyl chloride (PVC) respectively, and rapid adsorption kinetic progress within 120 min. The ZIF-8/SA adsorbents also exhibited excellent stability in the presence of interfering ions, acid/alkali, and humic acid, and displayed adsorption performance of > 70 % even in actual aquatic environment such as tap water, river water, and seawater. The results of characterizations showed that the synergistic effect of electrostatic interaction, hydrogen bonding, hydrophobic force, and van der Waals force was the main adsorption mechanism. The well-designed hydrophobic ZIF-8/SA monolithic materials would be promising to rapidly remove the MPs from the water environment.

Nanocomposite membranes for organic solvent nanofiltration: Recent advances, challenges, and prospects

Organic solvent nanofiltration (OSN) is an emerging technology for the separation of organic solvents that are relevant to the petrochemical, pharmaceutical, food and fine chemical industries. The separation performance of OSN membranes has continued to push the boundary up through advanced membrane fabrication techniques and novel materials for fabricating the membranes. Despite the many advantages, OSN membranes still face such challenges as low solvent permeability and durability in harsh organic solvent conditions. To overcome these limitations, attempts have been made to incorporate nanomaterial fillers into OSN membranes to improve their overall performance. This review analyzes the potential and use of nanomaterials for OSN membranes, including covalent organic frameworks (COFs), metal-organic frameworks (MOFs), metal oxides (MOs) and carbon-based materials (CBMs). Recent advances in the state-of-the-art nano-based OSN membranes, in the form of thin-film nanocomposite (TFN) membranes and mixed matrix membranes (MMMs), are reviewed. Moreover, the separation mechanisms of OSN with nano-based membranes are discussed. The challenges faced by these OSN membranes are also elaborated, and recommendations for further research in this field are provided.

A Review on Mixed Matrix Membranes for Solvent Dehydration and Recovery Process

Solvent separation and dehydration are important operations for industries and laboratories. Processes such as distillation and extraction are not always effective and are energy-consuming. An alternate approach is offered by pervaporation, based on the solution-diffusion transport mechanism. Polymer-based membranes such as those made of Polydimethylsiloxane (PDMS) have offered good pervaporation performance. Attempts have been made to improve their performance by incorporating inorganic fillers into the PDMS matrix, in which metal-organic frameworks (MOFs) have proven to be the most efficient. Among the MOFs, Zeolitic imidazolate framework (ZIF) based membranes have shown an excellent performance, with high values for flux and separation factors. Various studies have been conducted, employing ZIF-PDMS membranes for pervaporation separation of mixtures such as aqueous-alcoholic solutions. This paper presents an extensive review of the pervaporation performance of ZIF-based mixed matrix membranes (MMMs), novel synthesis methods, filler modifications, factors affecting membrane performance as well as studies based on polymers other than PDMS for the membrane matrix. Some suggestions for future studies have also been provided, such as the use of biopolymers and self-healing membranes.

Metal-Organic Frameworks for Liquid Phase Applications

In the last two decades, metal-organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low-carbon footprint energy carriers and the separation of CO2-containing gas mixtures. With progressive success in the synthesis of water- and solvent-resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.