Poly-Lipoic Ester-Based Coacervates for the Efficient Removal of Organic Pollutants from Water and Increased Point-of-Use Versatility

Abstract

The increasing frequency with which organic pollutants can be found in global surface water poses a formidable threat to both our environment and its creatures. While the problem has attracted adequate attention, current water treatment tools such as commercially available active carbon still cannot satisfy the remediating necessity due to its unfavorable rate of uptake and high regenerating cost. Moreover, water-insoluble pollutant adsorbents typically suffer from poor processability, effectively decreasing their potential for increased point-of-use versatility. Herein, we report a solution processable poly-lipoic ester-based material that readily undergoes simple coacervation upon ultrasonic solution processing. This material exhibits excellent removal efficiencies (>90%) and material recyclability for the uptake of highly concentrated typical pollutants including a plastic component bisphenol A (BPA), a pharmaceutical residue valsartan, and an industrial dye fluorescein from water. The polymer is conveniently accessible by a solvent-free, thermally initiated disulfide exchange ring-opening polymerization of a lipoic ester derivative and is postfunctionalized with an amphiphilic, π-electron-deficient bipyridinium-based side chain. Solution processing of this material facilitated the development of a pollutant sponge, which operates via a dip-remove-squeeze action, with an adsorption rate constant for BPA ∼85 times greater than its progenitor and achieving 80% removal efficiency in 30 s. This approach is particularly promising for quick point-of-use treatment of wastewater with high chemical oxygen demand. These results highlight the importance for material processability in the development of water-insoluble molecular adsorbents and establish poly-lipoic ester-based materials as contending precursors for application-driven soft matter development.

Connecting primitive phase separation to biotechnology, synthetic biology, and engineering

“…Here, we discuss and give examples from two specific engineering disciplines, pollution and waste control in environmental engineering and flavor encapsulation in food engineering, to further demonstrate the wide applicability of LLPS in the modern day. Coacervates have also contributed to the removal of hazardous byproduct chemical dyes, plastics, and other small molecule organics (Luque et al 2007;Zhao et al 2017;Zhang et al 2019;Valley et al 2019) from industrial wastewater (figure 6). Such LLPS systems are of interest to environmental engineers as they can either be recycled or do not contribute to toxic waste (Raghavarao et al 2003).…”

“…The microstructure of food has been shown to impact the sensory and textural properties of food and its digestion. Utilization of various processing methods, combinations of macronutrients, and ingredients allow for the design of foods with different microstructures associated with novel sensory and functional properties (Zhang et al 2019). Copyright American Chemical Society 2019.…”

“…While some in engineering fields may argue that the exhibited functions of primitive LLPS systems are quite simple compared to what can be achieved through synthetic biology (Meng and Ellis 2020), some modern applied processes use structures and/or functions observed in primitive LLPS. For example, drug delivery (Mohamed and Van der Walle 2008;Johnson and Wang 2014) and biomolecule purification (Xu et al 2011) in biotechnology, synthetic microbioreactors (Garenne et al 2016) and membraneless cellular organelle mimics (Yewdall et al 2020;Deng 2020) in synthetic biology, pollution control systems in environmental engineering (Zhang et al 2019), and flavor encapsulation in the food industry (Yeo et al 2005;Madene et al 2006) have used LLPS to accomplish functions. Recent OoL research has also been heavily focused on increasing the structural complexity of primitive LLPS, such as lipid layer- (Tang et al 2014) and lipid vesicle-encapsulated (Pir Cakmak et al 2019) coacervates, co-assembly of DNA liquid crystals in coacervates (Jia and Fraccia 2020; Fraccia and Jia 2020), mineral particle pickering emulsions scaffolded by polyethylene glycol (PEG)/dextran ATPS (Pir Cakmak and Keating 2017), and multiphase membraneless droplets (Lu and Spruijt 2020).…”

Recent Advances in Complex Coacervation Design from Macromolecular Assemblies and Emerging Applications

“…Zhang et al. [ 92 ] synthesized a kind of water‐insoluble poly‐lipoic ester containing amphiphilic side chains that gave rise to simple coacervation upon ultrasonic solution processing in water. Functionalization of side chains by π‐electron‐deficient bipyridinium enable the coacervate to uptake considerable amount of π‐electron‐rich contaminants, such as bisphenol A, valsartan, and fluorescein from water driven by hydrophobic interaction, all displaying a more than 90% extraction efficiency.…”

Trimeric Cationic Surfactant Coacervation as a Versatile Approach for Removing Organic Pollutants

“…Much effort has been made to improve the performance of coacervate in removing wastewater pollutants. One of the strategies is to immobilize coacervate onto porous solid materials to adsorb organic pollutants in wastewater. − For example, Dubin group applied the coacervate of poly­(diallyldimethylammonium chloride) (PDADMAC) with mixed surfactant micelles onto glass and quartz sand, which exhibits great interception capability for Orange OT at a high ionic strength. Our group modified sand and melamine foam by the coacervation of pH-sensitive hydrolyzed polyacrylamide (HPAM) and cationic ammonium gemini surfactant, which acts as a recyclable absorbent with good removal efficiency for Methyl Orange (MO).…”