Rapid eco-friendly selective dye removal using modified chitosan-based sponges: Synthesis, characterization, and application.

The ongoing challenge of water scarcity persists alongside a concerning rise in water pollution driven by population expansion and industrial development. As a result, urgent measures are imperative to address the pressing need for a clean and sustainable water supply. In this study, a sustainable and green approach was utilized to prepare four chitosan-based sponges from a chemically modified chitosan with different alkyl chains in aqueous medium and at room temperature. The resulting sponges displayed excellent stability in water with outstanding dye removal efficiency. The adsorption capacity was associated with the alkyl chain length incorporated to the polymer backbone. All sponges displayed a high adsorption capacity of methyl orange (MO) ranges between 238 and 380 mg g-1, while a low capacity were obtained for methylene blue (MB) and Rhodamine B (RB). Competitive adsorption experiments were conducted on binary and ternary mixtures to assess the selective removal of MO from a mixture of dyes in which the separation factor was found to be ranging between 1.6 and 32. The adsorption kinetics isotherms of all sponges followed the pseudo-second-order, and the Langmuir model was found to be more suitable than the Freundlich for the adsorption of MO on the sponges. The chitosan-based sponges showed stable performance, robustness and reusability over 5 adsorption-desorption cycles, indicating their great potential for water treatment applications.

Water-soluble chitosan salt as ecofriendly corrosion inhibitor for N80 pipeline steel in artificial sea water: Experimental and theoretical approach.

Chitosan, as a proficient biopolymer, has enormous potential as an ecofriendly corrosion inhibitor (CI), but their limited solubility restricts practical applications. Herein, an eco-friendly and water-soluble chitosan salt (CS) was utilized as a green CI on N80 pipeline steel in artificial sea water. Several structural and surface analytical tools were engaged in describing the characteristics of novel CS polymer. The corrosion inhibition efficiencies of CS on steel at different concentrations were investigated through gravimetric, conventional and advanced electrochemical techniques along with the surface analyses. Tafel polarization tests specified that CS performed as mixed-type CI with prevalent anodic inhibition characteristics. At a concentration of 1000 ppm, CS provided an inhibition efficiency (IE) of 96.68 %, following physiochemical adsorptions of CS on N80 surface validated by fitting Langmuir adsorption isotherm. However, the reductions in the values of IE at high temperature specified that the CS is the temperature dependent CIs. Scanning electrochemical microscopic evaluation confirmed the formation of thin CS inhibitors films with high electrochemical stability on N80 steel in saline. The performed surface characterizations on inhibited surfaces validated the adsorption of CS on the N80 surface by forming thin inhibitor film to obstruct metal corrosion. The theoretical simulation studies using molecular dynamics and density functional theory corroborated the experimentally obtained results.

Optimization of water/oil emulsion preparation: Impact of time, speed, and homogenizer type on droplet size and dehydration efficiency.

Due to their distinctive physical and chemical properties, emulsions are widely used in various industries such as pharmaceuticals, cosmetics, food, energy, and oil. Emulsion preparation differs from one application to another due to the effect of multiple parameters that can control droplet size and stability. However, there is a lack of fundamental understanding of the effect of emulsion preparation on its stability and performance. The emulsion preparation protocols can directly affect dehydration efficiency and stability. Herein, we report the influence of preparation conditions on the properties of the formed emulsions; we investigated the effect of mixing time, speed, and mixer type on the synthetic crude oil emulsion's droplet size and dehydration efficiency.

Carboxyl-functionalized polyimides for efficient bisphenol A removal: Influence of wettability and porosity on adsorption capacity.

Bisphenol A (BPA) removal from drinking water is greatly concerned for human and living things' safety. In this study, we synthesized three carboxyl-functionalized copolyimides and their homopolymer counterparts and evaluated their potential for removing BPA from an aqueous solution. The polymers were prepared via polycondensation reaction by reacting 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with various ratios of 3,5-diaminobenzoic acid (DABA) and 3,5-diamino-2,4,6-trimethylbenzoic acid (TrMCA). The effect of porosity, hydrophilicity, and methyl group content on BPA adsorption capacity has been investigated systemically. 6FDA-DABA demonstrated the highest BPA adsorption capacity with maximum adsorption of 67 mg g-1 and removal efficiency of approximately 90%. The anti-synergistic regime was observed between polymer porosity and hydrophilicity. As the content of the methyl group increases, the Brunauer-Emmett-Teller (BET) surface area increases, and the polymer hydrophilicity decreases, leading to a notable reduction in BPA adsorption capacity. The adsorption kinetics isotherms of BPA on 6FDA-based polyimides followed the pseudo-first-order kinetics, except for 6FDA-DABA, which was found to follow the pseudo-second-order. The BPA removal capacity was determined using both Langmuir and Freundlich isotherm models. The Langmuir model was more suitable than the Freundlich for the adsorption of BPA on the carboxyl-functionalized polyimides. To our knowledge, the prepared polyimides represent the first examples of utilizing polyimides for BPA removal. Investigating the structure/property relationship between polymers and their performance will pave the way to molecular engineering state-of-the-art polymer materials for efficient environmental remediation applications.

Recent progress on electrospun nanofibrous polymer membranes for water and air purification: A review.

Developing new polymer membranes with excellent thermal, mechanical, and chemical stability has shown great potential for various environmental remediation applications such as wastewater treatment and air filtration. Polymer membranes have been widely investigated over the past years and utilized to overcome severe ecological issues. Membrane-based technologies play a critical role in water purification and air filtration with the ability to act efficiently and sustainably. Electrospun nanofiber membranes have displayed excellent performance in removing various contaminants from water, such as bacteria, dyes, heavy metals, and oil. These nanofibrous membranes have shown good potential to filter the air from tiny particles, volatile organic compounds, and toxic gases. The performance of polymer membranes can be enhanced by fine-tuning polymer structure, varying surface properties, and strengthening overall membrane porosity. In this review, we discuss the involvement of electrospun nanofibrous membranes in different environmental remediation applications. It further reviews the recent progress of polymer membrane development by utilizing nanoparticles and naturally occurring polymers.

Norbornane-based covalent organic frameworks for gas separation.

Covalent organic frameworks (COFs) have emerged as a new class of crystalline porous materials with distinct structural features, such as uniform pore distribution, tunable architecture, and modifiable skeletons. COFs hold significant promise for application in gas separation because of their high Brunauer-Emmett-Teller surface area and narrow pore-size distribution, which enable selective separation. The porosity and separation performance of COFs have been finely tuned by structurally modifying the starting materials. Along this direction, for the first time, we prepared W-shaped diamines by catalytic arene-norbornene annulation (CANAL) and then treated them with trialdehyde (Tp) to synthesize novel ß-ketoenamine-linked norbornane-based COFs, i.e., ND-COF-1 and ND-COF-2, via a solvothermal Schiff-base condensation approach. The pore interior was decorated with methyl groups attached to the norbornane unit of the COF skeleton. Both COFs exhibited high chemical stability in different organic solvents and acidic media. Additionally, they showed high CO2/N2 selectivity compared with those of previously reported COFs. Moreover, their CH4/N2 separation efficiency was investigated, and the results revealed that ND-COF-1 is more selective than ND-COF-2, which could be attributed to the less hindered pathway offered to methane gas molecules by the framework pore.

Nanofibrous membranes comprising intrinsically microporous polyimides with embedded metal-organic frameworks for capturing volatile organic compounds.

Here, we report the fabrication of nanofibrous air-filtration membranes of intrinsically microporous polyimide with metal-organic frameworks (MOFs). The membranes successfully captured VOCs from air. Two polyimides with surface areas up to 500 m2 g-1 were synthesized, and the impact of the porosity on the sorption kinetics and capacity of the nanofibers were investigated. Two Zr-based MOFs, namely pristine UiO-66 (1071 m2 g-1) and defective UiO-66 (1582 m2 g-1), were embedded into the nanofibers to produce nanocomposite materials. The nanofibers could remove polar formaldehyde and non-polar toluene, xylene, and mesitylene from air. The highest sorption capacity with 214 mg g-1 was observed for xylene, followed by mesitylene (201 mg g-1), toluene (142 mg g-1), and formaldehyde (124 mg g-1). The incorporation of MOFs drastically improved the sorption performance of the fibers produced from low-surface-area polyimide. Time-dependent sorption tests revealed the rapid sequestration of air pollutants owing to the intrinsic porosity of the polyimides and the MOF fillers. The porosity allowed the rapid diffusion of pollutants into the inner fiber matrix. The molecular level interactions between VOCs and polymer/MOFs were clarified by molecular modeling studies. The practicality of material fabrication and the applicability of the material were assessed through the modification of industrial N95 dust masks. To the best of our knowledge, this is the first successful demonstration of the synergistic combination of intrinsically microporous polyimides and MOFs in the form of electrospun nanofibrous membranes and their application for VOC removal.