Polymeric hydrogels-based materials for wastewater treatment

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

Polyvinyl alcohol/chitosan based nanocomposite organohydrogel flexible wearable strain sensors for sports monitoring and underwater communication rescue

Hydrogel-based flexible wearable sensors have garnered significant attention in recent years. However, the use of hydrogel, a biomaterial known for its high toughness, environmental friendliness, and frost resistance, poses a considerable challenge. In this study, we propose a stepwise construction and multiple non-covalent interaction matching strategy to successfully prepare dynamically physically crosslinked multifunctional conductive hydrogels. These hydrogels self-assembled to form a rigid crosslinked network through intermolecular hydrogen bonding and metal ion coordination chelation. Furthermore, the freeze-thawing process promoted the formation of poly(vinyl alcohol) microcrystalline domains within the amorphous hydrogel network system, resulting in exceptional mechanical properties, including a tensile strength (2.09 ± 0.01 MPa) and elongation at break of 562 ± 12 %. It can lift 10,000 times its own weight. Additionally, these hydrogels exhibit excellent resistance to swelling and maintain good toughness even at temperatures as low as -60 °C. As a wearable strain sensor with remarkable sensing ability (GF = 1.46), it can be effectively utilized in water and underwater environments. Moreover, it demonstrates excellent antimicrobial properties against Escherichia coli (Gram-negative bacteria). Leveraging its impressive sensing ability, we combine signal recognition with a deep learning model by incorporating Morse code for encryption and decryption, enabling information transmission.

Dual-Responsive Hydrogels for Mercury Ion Detection and Removal from Wastewater

This study describes the development of a fast and cost-effective method for the detection and removal of Hg2+ ions from aqueous media, consisting of hydrogels incorporating chelating agents and a rhodamine derivative (to afford a qualitative evaluation of the heavy metal entrapment inside the 3D polymeric matrix). These hydrogels, designed for the simultaneous detection and entrapment of mercury, were obtained through the photopolymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) and N-vinyl-2-pyrrolidone (NVP), utilizing N,N'-methylenebisacrylamide (MBA) as crosslinker, in the presence of polyvinyl alcohol (PVA), a rhodamine B derivative, and one of the following chelating agents: phytic acid, 1,3-diamino-2-hydroxypropane-tetraacetic acid, triethylenetetramine-hexaacetic acid, or ethylenediaminetetraacetic acid disodium salt. The rhodamine derivative had a dual purpose in this study: firstly, it was incorporated into the hydrogel to allow the qualitative evaluation of mercury entrapment through its fluorogenic switch-off abilities when sensing Hg2+ ions; secondly, it was used to quantitatively evaluate the level of residual mercury from the decontaminated aqueous solutions, via the UV-Vis technique. The ICP-MS analysis of the hydrogels also confirmed the successful entrapment of mercury inside the hydrogels and a good correlation with the UV-Vis method.

Agro-Waste Valorization into Carbonaceous Eco-Hydrogel: A Circular Economy and Zero Waste Tactic for Doxorubicin Removal in Water/Wastewater

The existing work aims to evaluate the efficiency of eco-hydrogel for adsorption of pollutants prepared from biopolymeric matrix and agricultural waste-derived biochar. An efficient and reusable adsorbent, designed from the integration of maize stalk activated carbon into a gelatin-alginate composite (MSAC@GE-SA) was explored for removal of doxorubicin hydrochloride (Doxo.HCL) from polluted water. The structural properties, presence of surface functional groups, and elemental composition were explored using XRD, SEM, BET, FTIR, and XPS techniques. The key adsorption parameters such as Doxo.HCL concentration, MSAC@GE-SA amount, solution pH, and the contact time between adsorbate and adsorbents were successfully optimized for the effective removal of Doxo.HCL (qmax = 239.41 mg g-1). The kinetic mechanism of MSAC@GE-SA fits well with a pseudo-second-order rate model (R2 = 0.980), followed by mono- and multilayered Langmuir and Freundlich isotherms with R2 values 0.991 and 0.993, respectively. The recyclability of MSAC@GE-SA showed great stability without any physical damage and having sustained removal efficiency up to 10 cycles (96.32 to 55.66%). The versatility of MSAC@GE-SA was further investigated for river, canal, and sewage water samples under identical experimental conditions. The practicality of the MSAC@GE-SA was evaluated by spiking Doxo.HCL into industrial effluents via the standard addition method. Subsequently, the chemical oxygen demand (COD) of the treated pollutants exhibited a notable reduction, decreasing significantly from 128 to 80 mg L-1. Following 10 successful adsorption-desorption cycles, the spent MSAC@GE-SA was utilized as a fertilizer for Vigna radiata plants, positively contributing to overall plant growth without causing harm. Hence, proposed adsorbent (MSAC@GE-SA) emerges as a viable and sustainable solution, demonstrating features of reusability and cost-effectiveness. It holds significant promise for the removal of pharmaceutical pollutants, aligning with the principles of circular economy and zero-waste tactics.

Chitosan-based oral hydrogel formulations of β-galactosidase to improve enzyme supplementation therapy for lactose intolerance

β-Galactosidase supplementation plays an important role in the life of people with lactose intolerance. However, these formulations are rendered ineffective by the low pH and pepsin in the stomach and pancreatic proteases in the intestine. Therefore, it is necessary to develop oral transport systems for carrying this enzyme in the active form up to the intestine, where the lactose digestion occurs. In this research, a new hydrogel was developed that could potentially be used for enzyme supplement therapy. In this regard, the chitosan-based β-Gal formulations described in the manuscript are an alternative long-acting preparation to the so far available preparations that allow for enzyme protection and mucosal targeting. These hydrogels were prepared from chitosan and polyethylene glycol and contained a covalently immobilized β-galactosidase from Aspergillus oryzae. The β-galactosidase in the hydrogel was protected from degradation in a gastric medium at a pH of 2.5 and retained 75 % of its original activity under subsequent intestinal conditions. In the case of a simulated gastric fluid with a pH of 1.5, a copolymer containing methacrylic acid functional groups was sufficient to protect the hybrid hydrogel from the extremely acidic pH. In addition, the surface of the hydrogel was chemically modified with thiol and amidine groups, which increased the binding to intestinal mucin by 20 % compared with the unmodified hydrogel. These results represent a promising approach for oral transport as a reservoir for β-galactosidase in the small intestine to reduce the symptoms of hypolactasia.

Chitosan Hydrogels for Water Purification Applications

Chitosan-based hydrogels have gained significant attention for their potential applications in water treatment and purification due to their remarkable properties such as bioavailability, biocompatibility, biodegradability, environmental friendliness, high pollutants adsorption capacity, and water adsorption capacity. This article comprehensively reviews recent advances in chitosan-based hydrogel materials for water purification applications. The synthesis methods, structural properties, and water purification performance of chitosan-based hydrogels are critically analyzed. The incorporation of various nanomaterials into chitosan-based hydrogels, such as nanoparticles, graphene, and metal-organic frameworks, has been explored to enhance their performance. The mechanisms of water purification, including adsorption, filtration, and antimicrobial activity, are also discussed in detail. The potential of chitosan-based hydrogels for the removal of pollutants, such as heavy metals, organic contaminants, and microorganisms, from water sources is highlighted. Moreover, the challenges and future perspectives of chitosan-based hydrogels in water treatment and water purification applications are also illustrated. Overall, this article provides valuable insights into the current state of the art regarding chitosan-based hydrogels for water purification applications and highlights their potential for addressing global water pollution challenges.