Self-coagulating polyelectrolyte complexes for target-tunable adsorption and separation of metal ions

Preparation of a covalent organic framework-modified silica-gel composite for the effective adsorption of Pd(II), Zr(IV) and Mo(VI) from nitric acid solution

In this study, a novel covalent organic framework-modified silica-gel composite (Si-COF) was synthesized for the adsorption of palladium [Pd(II)], zirconium [Zr(IV)], and molybdenum [Mo(VI)] from nitric acid solutions and its adsorption behaviors were systemically investigated under the effects of contact time, nitric acid concentration, solution temperature and others. The pseudo-second-order kinetic model governed the adsorption of these metal ions onto the Si-COF composite, and the Langmuir isotherm model well-matched with the experimental data, with maximum adsorption capacities of 0.588, 0.221, and 0.417 mmol/g for Pd(II), Zr(IV) and Mo(VI), respectively. The adsorption of these metal ions was clarified to originate from the interaction with the abundant nitrogenous groups on the Si-COF composite by the X-ray photoelectron spectroscopy (XPS) method.

Formation and Characterization of Chitosan-Based Polyelectrolyte Complex Containing Antifungal Phenylpropanoids

In this work, a novel chitosan-based polyelectrolyte complex (PEC) was prepared using chitosan as the cationic polyelectrolyte, while a potassium salt of poly(maleic anhydride-alt-tetradecene) (PMA-14) served as the anionic counterpart. These PECs were used for the encapsulation of two nitroeugenol derivatives: 4-allyl-2-methoxy-6-nitrophenol (3) and 2-allyl-6-nitrophenol (4). The results confirm complex formation and efficient encapsulation of active compounds. Encapsulation efficiency (EE) was influenced by the chemical structure of the compounds, with 32.18% EE for 3 and 20.36% EE for 4. The resulting systems were characterized by fluorescence probing techniques, dynamic light scattering (DLS), and zeta potential. On the other hand, antifungal assays revealed that, in free form, 3 exhibits a much higher activity against Botritys cinerea than 4. However, no effect of encapsulation of both compounds on antifungal performance was observed. Results from molecular dynamic studies indicate that a stabilization effect is induced by compounds 3 and 4 during PEC formation, which is attributed to specific interactions between polyelectrolytes and guest molecules. These results are in line with the EE values measured for 3 and 4 and explain the low release from PECs of these molecules. Thus, the potential development of PEC-based systems for the delivery of bioactive compounds requires a deeper comprehension of parameters determining the relationship between encapsulation efficiency and delivery kinetics.

Polyelectrolyte and polyelectrolyte complex-incorporated adsorbents in water and wastewater remediation - A review of recent advances

In recent years, polyelectrolyte-incorporated functional materials have emerged as novel adsorbents for effective remediation of pollutants in water and wastewater. Polyelectrolytes (PEs) are a special class of polymers with long chains of repeating charged moieties. Polyelectrolyte complexes (PECs) are obtained by mixing aqueous solutions of oppositely charged PEs. Herewith, this review discusses recent advances with respect to water and wastewater remediation using PE- and PEC-incorporated adsorbents. The review begins by highlighting some water resources, their pollution sources and available treatment techniques. Next, an overview of PEs and PECs is discussed, highlighting the evolving progress in their processing. Consequently, application of these materials in different facets of water and wastewater remediation, including heavy metal removal, precious metal and rare earth element recovery, desalination, dye and emerging micropollutant removal, are critically reviewed. For water and wastewater remediation, PEs and PECs are mostly applied either in their original forms, as composites or as morphologically-tunable complexes. PECs are deemed superior to other materials owing to their tunability for both cationic and anionic pollutants. Generally, natural and semi-synthetic PEs have been largely applied owing to their low cost, ready availability and eco-friendliness. Except dye removal and desalination of saline water, application of synthetic PEs and PECs is scanty, and hence requires more focus in future research.

High-efficiency adsorption removal for Cu(II) and Ni(II) using a novel acylamino dihydroxamic acid chelating resin

Cu/Ni-bearing wastewater contamination has recently been a challenge for the environmental protection worldwide. Herein, a novel poly(2-acrylamide-pentanedihydroxamic acid) (PAPDA) resin containing -CONHOH and -COOH groups was prepared and applied to effectively remove Cu²⁺ and Ni²⁺ from heavy metal wastewater. The batch adsorption experiments revealed that the maximum adsorption capacities of PAPDA resin for Cu²⁺ and Ni²⁺ were 436.08 and 195.05 mg·g^-1, respectively, which were 10.20 and 9.45 times higher than that of polyacrylic resin. Specifically, the adsorption kinetics and thermodynamics of PAPDA were respectively consistent with the pseudo-second-order kinetic model and the Langmuir isotherm model, indicating that the adsorption is a single-layer chemisorption process. Besides, the adsorption mechanism was investigated by SEM, XRD, FT-IR, XPS, DFT calculations, suggesting that the PAPDA resin possessing abundant active sites could effectively adsorb the heavy metal ions. Noticeably, the -CONHOH groups represented the strong affinity towards Cu²⁺ and Ni²⁺ by forming stable five-membered rings. In addition, column experiments were conducted to study the practical adsorption process of PAPDA resin to heavy metal ions. Overall, the results proved that the novel PAPDA resin as a green and highly efficient adsorbent has a promising potential for the treatment of heavy metals-containing wastewater.

Polyelectrolyte-Dye Interactions: An Overview

Polyelectrolytes are polymers with repeating units of ionizable groups coupled with counterions. Recently, polyelectrolytes have drawn significant attention as highly promising macromolecular materials with potential for applications in almost every sector of our daily lives. Dyes are another class of chemical compounds that can interact with substrates and subsequently impart color through the selective absorption of electromagnetic radiation in the visible range. This overview begins with an introduction to polyelectrolytes and dyes with their respective definitions, classifications (based on origin, molecular architecture, etc.), and applications in diverse fields. Thereafter, it explores the different possible interactions between polyelectrolytes and dyes, which is the main focus of this study. The various mechanisms involved in dye-polyelectrolyte interactions and the factors that influence them are also surveyed. Finally, these discussions are summarized, and their future perspectives are presented.

An Overview on Composite Sorbents Based on Polyelectrolytes Used in Advanced Wastewater Treatment

Advanced wastewater treatment processes are required to implement wastewater reuse in agriculture or industry, the efficient removal of targeted priority and emerging organic & inorganic pollutants being compulsory (due to their eco-toxicological and human health effects, bio-accumulative, and degradation characteristics). Various processes such as membrane separations, adsorption, advanced oxidation, filtration, disinfection may be used in combination with one or more conventional treatment stages, but technical and environmental criteria are important to assess their application. Natural and synthetic polyelectrolytes combined with some inorganic materials or other organic or inorganic polymers create new materials (composites) that are currently used in sorption of toxic pollutants. The recent developments on the synthesis and characterization of composites based on polyelectrolytes, divided according to their macroscopic shape-beads, core-shell, gels, nanofibers, membranes-are discussed, and a correlation of their actual structure and properties with the adsorption mechanisms and removal efficiencies of various pollutants in aqueous media (priority and emerging pollutants or other model pollutants) are presented.

Scale-up one-pot synthesis of waste collagen and apple pomace pectin incorporated pentapolymer biocomposites: Roles of waste collagen for elevations of properties and unary/ ternary removals of Ti(IV), As(V), and V(V)

Herein, hazardous solid particulate waste collagenic fibers (SWCFs) of leather industries were incorporated into apple pomace pectin (APPN)-grafted-pentapolymer, i.e., APPN-g-[sodium 2-methylidenebutanedioate(SMBD)-co-N-((3-(isopropylamino)-3-oxopropoxy) methyl) butyramide (CM1)-co-N-(hydroxymethyl)prop-2-enamide (NHMPE)-co-N-(hydroxymethyl)-4-(N-isopropylbutyramido)butanamide (CM2)-co-N-(propan-2-yl)prop-2-enamide NPYPE)/ PENP1], i.e., APPN-g-PENP1/ PENP2, prepared via one-pot facile polymerization of APPN and synthetic monomers, i.e., SMBD, NHMPE, and NPYPE, in aqueous medium, to fabricate an optimum multifunctional hybrid biocomposite adsorbent/ HCOM3. In PENP1, PENP2, and HCOM3, fourth/ CM1 and fifth/ CM2 multifunctional comonomers were anchored in situ. The structures of PENP1, PENP2, HCOM3, CM1, CM2, and metal-ion adsorbed HCOM3; APPN-grafting; SWCF incorporation; and surface properties were analyzed through NMR, XPS, FTIR, XRD, and SEM. The elevated adsorption efficiencies (AEs), reusability, thermostability, swelling, network durability, and crosslink density of HCOM3 were attributed to variable functionalities of SWCF/ APPN, explored by DLS and TGA, swelling, network, and thermodynamic parameters. Compared to SWCF, APPN, PENP1, and PENP2, the elevated AEs and reusability compelled HCOM3 as more suitable for scalable waste management. The maximum AEs, i.e., 171.79, 180.47, and 177.27 mg g^-1, for Ti(IV), As(V), and V(V) at pH_op = 7.0, 3.0, and 5.0, respectively, within 5-100 mg L^-1 and at 298 K for 25 mg HCOM3 deteriorated during ternary adsorption by the antagonistic effects.