Membrane Surface Functionalization with Imidazole Derivatives to Benefit Dye Removal and Fouling Resistance in Forward Osmosis

Abstract

Water contaminated with low concentrations of pollutants is more difficult to clean up than that with high pollutant content levels. Membrane separation provides a solution for removing low pollutant content from water. However, membranes are prone to fouling, losing separation performances over time. Here we synthesized neutral (IM-NH2) and positively charged (IL-NH2) imidazole derivatives to chemically functionalize membranes. With distinct properties, these imidazole grafts could tailor membrane physicochemical properties and structures to benefit forward osmosis (FO) processes for the removal of 20–100 ppm of Safranin O dyea common dye employed in the textile industry. The water fluxes produced by IM-NH2- and IL-NH2-modified membranes increased by 67% and 122%, respectively, with DI water as the feed compared to that with the nascent membrane. A 39% flux increment with complete dye retention (∼100%) was achieved for the IL-NH2-modified membrane against 100 ppm of Safranin O dye. Regardless of the dye concentration, the IL-NH2-modified membrane exhibited steadily higher permeation performance than the original membrane in long-term experiments. Reproducible experimental results were obtained with the IL-NH2-modified membrane after cleaning with DI water, demonstrating the good antifouling properties and renewability of the newly developed membrane.

Surface Mineralization of the TiO2–SiO2/PES Composite Membrane with Outstanding Separation Property via Facile Vapor-Ventilated In Situ Chemical Deposition

“…Meanwhile, the peaks with stronger intensities of TiO 2 –H 2 O (1.6) and SiO 2 –H 2 O (1.4) located at the position of r = 3.0 Å were much stronger than the value of PES–H 2 O (0.4) located at r = 3.0 Å (Figure b), suggesting that the water-bonding capability was on the order of TiO 2 –H 2 O > SiO 2 –H 2 O > PES–H 2 O. The results indicate that the intensities of the binding energy among TiO 2 , SiO 2 , and PES segments with water molecules were in the sequence of | E TiO 2 –H 2 O | > | E SiO 2 –H 2 O | > | E PES–H 2 O | (Figure d). , Consequently, the surface mineralization conducted via vapor-ventilated chemical deposition endows the membrane with enhanced surface hydrophilicity by absorbing more water molecules infiltrated into the membrane bulk, and the nanoheterogeneous TiO 2 –SiO 2 modification structure collectively results in ultrafast water transportation.…”

“…Polymers are the most employed materials for synthesizing membranes with high permselectivity, which easily suffer from membrane fouling under demanding conditions and cannot satisfy the practical applications of complicated natural organic matter (NOM) compositions . This is because the rejected foulants are prone to directly accumulating onto the relatively hydrophobic polymer surfaces and then deteriorate the permeability and filtration effectiveness of membranes. , Even though a variety of post-treatments, such as membrane cleaning, can be used to mitigate surface fouling, the permeating performance can only be partially restored; furthermore, the degradation of the polymeric matrix is inevitable . Inorganic membranes that constitute metal oxides have also been broadly utilized in treating wastewater containing various contaminants with better fouling-resistant and fouling-releasing advantages when compared to conventional polymer membranes. , This can be mainly ascribed to the metal oxides with high surface free energy in favor of capturing water molecules within their micro-/nanostructures to form a continuous hydration layer, serving as a physical barrier to inhibit the oil adhesion, protein adsorption, or cell attachments .…”

Zwitterionic and Photocatalytic Janus Membrane Based on Diethylamine N-Oxide Group and WS2 Nanosheets for Dye Removal in Forward Osmosis

“…Among all the water purification methods, using membranes has become one of the most successful techniques to decrease or eliminate the high concentration of pollutants. Particularly, forward osmosis (FO) systems have demonstrated the ability to remove organic dyes because of the functionalization of the membranes to increase their hydrophilicity, avoiding the formation of fouling and rejecting contaminants, such as organic pollutants. , Another important aspect in FO systems is the use of the osmotic pressure, where an osmotic gradient generated between a solution of higher water chemical potential (low osmotic pressure) to a solution of lower water chemical potential (higher osmotic pressure) drives the water molecules across the membrane, , and avoid the use of external mechanical pressure …”

Stimuli-Responsive Lysozyme Nanocapsule Engineered Microfiltration Membranes with a Dual-Function of Anti-Adhesion and Antibacteria for Biofouling Mitigation

“…In general, surface modification of the membrane is an attractive solution to promote anti-biofouling performance of the membrane since this approach has a minor impact on the operation of the membrane process. − Current methods can be generally categorized into two strategies. Most studies focus on anti-adhesion, i.e., the modification of the membrane surface to delay and/or prevent the deposition of organic foulants and bacteria, generally by increasing the surface hydrophilicity or altering the surface charge and roughness .…”