One-pot synthesis of sodium alginate-grafted-terpolymer hydrogel for As(III) and V(V) removal: In situ anchored comonomer and DFT studies on structures

pH-Responsive Biocompatible Fluorescent Hydrogel for Selective Sensing and Adsorptive Recovery of Dysprosium

The elevated accumulation of electronic wastes, especially containing Dysprosium ion [i.e., Dy(III)], is emerging as a potential environmental threat. To overcome the deleterious effects of Dy(III), detection and removal of Dy(III) is crucial. Moreover, recovery of high-value Dy(III) is economically beneficial. However, the availability of a single material, capable of sensing Dy(III) in nanomolar concentration and simultaneously adsorbing it with high adsorption capacity (AC), is rare. Therefore, to solve this problem, a pH-responsive fluorescent amino graphene oxide-impregnated-engineered polymer hydrogel (AGO-EPH) has been synthesized, suitable for selective sensing of Dy(III) in nanomolar concentration and adsorbing it from wastewater at ambient temperature. This terpolymeric hydrogel is synthesized from two nonfluorescent monomers, propenoic acid (PNA) and prop-2-enamide (PEAM), along with an in situ generated comonomer (3-acrylamidopropanoic acid/AAPPA) through N-H activation during polymerization. Surface properties and structural details of AGO-EPH are established using NMR, FTIR, XRD, TEM, SEM, EDX, Raman, MALDI-mass, and DLS studies. The AGO-EPH exhibits blue fluorescence with selective turn-off sensing of Dy(III) with the detection limit of 1.88 × 10-7 (M). The maximum AC of AGO-EPH is 41.97 ± 0.39 mg g-1. The developed AGO-EPH shows consistent adsorption-desorption property over five cycles, with more than 90% desorption efficiency per cycle, confirming significant recovery of the valuable Dy(III). From Logic gate calculations, complexation of Dy(III) and AGO-EPH may be the reason behind fluorescence quenching. The AGO-EPH also shows antibacterial action against ∼3 × 108 cells mL-1 of E. coli solution. Overall, the developed pH-responsive engineered hydrogel can be used as a potential low-cost sensing device and reusable adsorbent for Dy(III).

Modified sodium alginate-based three-dimensional network hydrogel dust suppressant: Preparation, characterization, and performance

Chemical dust suppression is typically associated with high economic costs, unclear efficacy, and poor degradability. In this study, sodium alginate (SA) was extracted from kelp and cross-linked with polyvinyl alcohol (PVA) and polyacrylamide (PAM). Sulfonated castor oil (CAS) was subsequently added to generate a three-dimensional network hydrogel dust suppressant (PVA-SA-PAM/CAS). Using single-factor experiments, the optimal reaction temperature (60 °C) and dosages of PVA, PAM, and the cross-linking agent (2.5, 4.5, and 0.1 g, respectively) were determined. The viscosity and compressive strength of the prepared hydrogel were 86 mPa·s and 218 kPa, respectively, which meet the requirements for mine dust suppression. Various analyses revealed the hydrogel's reaction process and microstructure changes. Additionally, thermogravimetric experiments proved that the hydrogel had good thermal stability. The specific surface area and pore size of the hydrogel were 0.0278 m2/g and 11.8 nm, respectively, improving its adsorption capacity. Additionally, PVA-SA-PAM/CAS exhibited a good water retention rate. The dust suppression efficiency of PVA-SA-PAM/CAS was >98 % under strong winds (12 m/s). Moreover, the degradation rate of PVA-SA-PAM/CAS was 37 % after eight cycles (56 d) under environmental conditions. Therefore, PVA-SA-PAM/CAS exhibits good wetting, dust suppression, and degradation properties, which can effectively alleviate mine dust pollution.

Efficient and Selective Removal of Heavy Metals and Dyes from Aqueous Solutions Using Guipi Residue-Based Hydrogel

The presence of organic dyes and heavy metal ions in water sources poses a significant threat to human health and the ecosystem. In this study, hydrogel adsorbents for water pollution remediation were synthesized using Guipi residue (GP), a cellulose material from Chinese herbal medicine, and chitosan (CTS) through radical polymerization with acrylamide (AM) and acrylic acid (AA). The characteristics of the hydrogels were analyzed from a physicochemical perspective, and their ability to adsorb was tested using model pollutants such as Pb2+, Cd2+, Rhodamine B (RhB), and methyl orange (MO). The outcomes revealed that GP/CTS/AA-co-AM, which has improved mechanical attributes, effectively eliminated these pollutants. At a pH of 4.0, a contact duration of 120 min, and an initial concentration of 600 mg/L for Pb2+ and 500 mg/L for Cd2+, the highest adsorption capabilities were 314.6 mg/g for Pb2+ and 289.1 mg/g for Cd2+. Regarding the dyes, the GP/CTS/AA-co-AM hydrogel displayed adsorption capacities of 106.4 mg/g for RhB and 94.8 mg/g for MO, maintaining a stable adsorption capacity at different pHs. Compared with other competitive pollutants, GP/CTS/AA-co-AM demonstrated a higher absorption capability, mainly targeted toward Pb2+. The adsorption processes for the pollutants conformed to pseudo-second-order kinetics models and adhered to the Langmuir models. Even after undergoing five consecutive adsorption and desorption cycles, the adsorption capacities for heavy metals and dyes remained above 70% and 80%. In summary, this study effectively suggested the potential of the innovative GP/CTS/AA-co-AM hydrogel as a practical and feasible approach for eliminating heavy metals and dyes from water solutions.

Banana Peel Derived Chitosan-Grafted Biocomposite for Recovery of NH4+ and PO43

Biomass-derived adsorbents afford accessible and inexpensive harvesting of nitrogen and phosphorus from wastewater sources. Human urine is widely accepted as a rich source of nitrogen and phosphorus. However, direct use of urine in agriculture is untenable because of its unpleasant smell, pathogen contamination, and pharmaceutical residues. In this work, we have grafted chitosan onto dried and crushed banana peel (DCBP) to generate the biocomposite DCBP/Ch. A combination of FTIR, TGA, XRD, FESEM, EDX, and NMR analyses were used to characterize DCBP/Ch and reveal condensation-aided covalent conjugation between O-H functionalities of DCBP and chitosan. The adsorption performance of DCBP/Ch toward NH4+ and PO43- is in sync with its attractive surface porosity, elevated crystallinity, and thermostability. The maximum adsorption capacity of DCBP/Ch toward NH4+/PO43- was estimated as 42.16/15.91 mg g-1 at an operating pH of 7/4, respectively, and ranks highly when compared to previously reported bioadsorbents. DCBP/Ch performs admirably when tested on artificial urine. While nitrogen and phosphorus harvesting from human urine using single techniques has been reported previously, this is the first report of a single adsorbent for recovery of NH4+ and PO43-. The environmental compatibility, ease of preparation, and economic viability of DCBP/Ch present it as an attractive candidate for deployment in waste channels.

Modified alginate materials for wastewater treatment: Application prospects

Sodium alginate is a natural macromolecule widely used because of its abundance, low cost of acquisition, and rich hydroxyl and carboxyl groups in the matrix. The physical modification of sodium alginate can be made by blending it with polymer materials. The so-yielded alginate complex is commonly unstable in an aqueous environment due to alginate backbones' high hydrophilicity. The chemical modification can remove its hydrophilic groups and introduce special functional groups or polymers onto the alginate backbones to provide excess reaction sites for specific reactions and effective complexation sites for accommodating antibiotics, dyes, heavy metal ions, and radioactive elements. Sodium alginate has been used in water treatment engineering under revised modification protocols. This article also reviews the latest modification protocols for sodium alginate and outlines the novel application of the modified materials. The limitations of modified sodium alginate materials are described, and research prospects are put forward.

An MXene-Grafted Terpolymer Hydrogel for Adsorptive Immobilization of Toxic Pb(II) and Post-Adsorption Application of Metal Ion Hydrogel

Toxic metal ions present in industrial waste, such as Pb(II), introduce deleterious effects on the environment. Though the adsorptive removal of Pb(II) is widely reported, there is a dearth of research on the suitable utilization and disposal of the Pb(II)-adsorbed adsorbent. In this work, an MXene-grafted terpolymer (MXTP) hydrogel has been designed for the adsorption of Pb(II) under ambient conditions of pH and temperature. The hydrogel MXTP was synthesized by facile one-pot polymerization in aqueous solvent, and the detailed structural characterization of terpolymer (TP), MXTP, and Pb(II)-loaded MXTP, i.e., Pb(II)-MXTP, was carried out by a combination of proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometric (XRD), thermogravimetric/differential thermogravimetric (TG/ DTG), and field emission scanning electron microscopic (FESEM) analyses. The specific capacitance and conductivities of Pb(II)-MXTP were studied with cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS), which unambiguously indicate successful post-adsorption application. The specific capacitance of MXTP decreased after Pb(II) adsorption, whereas the conductivity increased significantly after Pb(II) adsorption, showing that MXTP can be successfully deployed as a solid electrolyte/anode after Pb(II) adsorption. This study covers the synthesis of a novel MXene-grafted terpolymer hydrogel for adsorptive exclusion of Pb(II) and assessment of the as-adsorbed Pb(II)-loaded hydrogel as a solid electrolyte/anode material and is the first demonstration of such post-adsorptive application.

Functionalized Carbon Nanotubes Encapsulated Alginate Beads for the Removal of Mercury Ions: Design, Synthesis, Density Functional Theory Calculation, and Demonstration in a Batch and Fixed-Bed Process

Various nanomaterials have been envisaged mainly through batch studies for environmental remediation application. The real utilization of these new generation adsorbents in large scale pose a difficulty due to its low density and small size which makes it difficult for isolation after application. In this context, nanoadsorbents polymer composite beads can be seen as a way out. Here, functionalized CNTs (carbon nanotubes) have been fabricated into micro beads with sodium alginate. The alginate-functionalized CNT (Alg-f-CNT) beads were then comprehensively evaluated for batch and fixed-bed column separation of divalent mercury ions from an aqueous medium. The effects of process parameters such as pH, contact time, feed Hg2+ concentration, and temperature were studied. Simulation of the experimental data suggested that adsorption is an endothermic spontaneous process which follows the pseudo-second-order kinetic and Langmuir isotherm model. The desorption of the Hg2+ ion from used adsorbent was possible with 1 M HNO3. The breakthrough curves at different process parameters were investigated during fixed-bed column separation and found to be in good agreement with Thomas model. The regeneration and reusability of the adsorbent were tested up to five cycles without a significant decrease in the removal performance. Density functional theory studies revealed stronger interaction of Alg-f-CNT with Hg compared to free alginic acid and established the role of carboxyl and oxo groups present in the adsorbent in the coordination of the Hg2+ ions. The experimental results demonstrate that functionalized CNT-encapsulated alginate beads are a promising alternate material, which can be used to remove mercury in the fixed-bed column mode of the operation.

Polymeric hydrogels-based materials for wastewater treatment

Low-cost and reliable wastewater treatment is a relevant issue worldwide to reduce the concentration of environmental pollutants. Industrial effluents containing dyes, heavy metals, and other inorganic and organic compounds can pollute water resources; therefore, novel technologies are required to mitigate and control their release into the environment. Adsorption is one of the simplest methods for treating contaminated water in which a wide spectrum of adsorbents can be used to remove emerging compounds. Hydrogels are interesting materials with high adsorption capacities that can be synthesized via green routes. These adsorbents are promising for large-scale industrial wastewater treatment applications; however, gaps still exist in achieving sustainable commercial implementation. This review focuses on the discussion and analysis of preparation, characterization, and adsorption properties of hydrogels for water purification. The advantages of these polymeric materials for water treatment were analyzed, including their performance in the removal of different organic and inorganic contaminants. Recent advances in the functionalization of hydrogels and the synthesis of novel composites have also been described. The adsorption capacities of hydrogel-based adsorbents are higher than 500 mg/g for different organic and inorganic pollutants, and can reach values of up to >2000 mg/g for organic compounds, significantly outperforming other materials reported for water cleaning. The main interactions involved in the adsorption of water pollutants using hydrogel-based adsorbents were described and explained to allow the interpretation of their removal mechanisms. The current challenges in the implementation of hydrogels for water purification in real-life operations are also highlighted. This review provides an updated picture of hydrogels as interesting materials to address water depollution worldwide.

Manganese Sulfate Nanocomposites Fabricated by Hot-Melt Extrusion for Chemodynamic Therapy of Colorectal Cancer

The development of metal salts-based nanocomposites is highly desired for the Fenton or Fenton-like reaction-based chemodynamic therapy of cancer. Manganese sulfate (MnSO₄)-dispersed nanoparticles (NPs) were fabricated with a hot-melt extrusion (HME) system for the chemodynamic therapy of colorectal cancer in this study. MnSO₄ was homogeneously distributed in polyethylene glycol (PEG) 6000 (as a hydrophilic polymer) with the aid of surfactants (Span 80 and Tween 80) by HME processing. Nano-size distribution was achieved after dispersing the pulverized extrudate of MnSO₄-based composite in the aqueous media. The distribution of MnSO₄ in HME extrudate and the interactions between MnSO₄ and pharmaceutical additives were elucidated by Fourier-transform infrared, X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy analyses. Hydroxyl radical generation efficiency by the Fenton-like chemistry capability of Mn²⁺ ion was also confirmed by catalytic assays. By using the intrinsic H₂O₂ in cancer cells, MnSO₄ NPs provided an elevated cellular reactive oxygen species level, apoptosis induction capability, and antiproliferation efficiency. The designed HME-processed MnSO₄ formulation can be efficiently used for the chemodynamic therapy of colorectal cancer.

Pb2+-imprinted thermosensitive antibacterial adsorbent derived from sodium alginate and PNIPAM for Pb2+ recovery

Two sodium alginate-based Pb²⁺-imprinted thermosensitive hydrogels (SPIT (without ɛ-PL) and SPPIT (with ɛ-PL)) were synthesized, with sodium alginate and ɛ-polylysine (ɛ-PL) as the matrix, N-isopropylacrylamide as the monomer. Characterization with differential scanning calorimeter, Fourier transform infrared spectroscopy, thermogravimetric analyzer, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy confirmed the aimed structure of the hydrogels. The adsorption capacity of SPIT and SPPIT for Pb²⁺ was 98.64 mg/g and 153.49 mg/g, respectively. Washing the Pb²⁺-loaded adsorbent with 10 °C deionized water, SPIT and SPPIT achieved a desorption efficiency of 94.59 % and 97.51 %, respectively. After 10 cycles of adsorption-desorption process, the adsorption capacity and desorption efficiency remained at about 80-88 % of the original ones, expressing excellent reusability. In a mixture containing eight metal ions (Pb²⁺, Cu²⁺, Mg²⁺, Ca²⁺, Cd²⁺, Na⁺, K⁺, Fe³⁺), the adsorption capacity of SPIT to Pb²⁺ was 92.49 mg/g, and that of SPPIT was 102.49 mg/g, much higher than that to the other ions (1.50-11.38 mg/g on SPIT, 9.48-27.45 mg/g on SPPIT), showing excellent adsorption selectivity. The introduction of ɛ-PL enhanced the adsorption capacity, antibacterial ability and stability of the hydrogel, ensuring better application potential in real wastewater.

Grafted Pullulan Derivatives for Reducing the Content of Some Pesticides from Simulated Wastewater

The goal of the current article was to obtain data regarding the application of a series of grafted pullulan derivatives, as flocculating agents, for removal of some pesticide formulations from model wastewater. The pullulan derivatives are cationic polyelectrolytes, with various content and length of grafted poly[(3-acrylamidopropyl)-trimethylammonium chloride] chains onto the pullulan (P-g-pAPTAC)]. The commercial pesticides are either fungicide (Bordeaux Mixture) (BM) or insecticides (Decis (Dc)—active ingredient Deltamethrin, Confidor Oil (CO)—active ingredient Imidacloprid, Confidor Energy (CE)—active ingredients Deltamethrin and Imidacloprid and Novadim Progress (NP)—active ingredient Dimethoate). The removal efficiency has been assessed by UV-Vis spectroscopy measurements as a function of some parameters, namely polymer dose, grafted chains content and length, pesticides concentration. The P-g-pAPTAC samples showed good removal efficacy at dose_op, more than 94% for BM, between 84 and 90% for DC, CO and CE and around 93% for NP. The maximum percentage removal decreased with the pesticides (DC, CO, CE, NP) concentration declining; no effect of BM concentration in suspension on its removal efficiency process has been noted. Differences indicated by zeta potential and particle size distribution measurements regarding the pesticides removal mechanisms by pullulan derivatives (charge neutralization, bridging, etc.) are discussed.