Silver nanoparticle-embedded pectin-based hydrogel for adsorptive removal of dyes and metal ions

Pectin-nano zero valent iron nanocomposites for efficient heavy metal removal and bactericidal action against waterborne pathogens - Innovative green solution towards environmental sustainability

This study investigated the effectiveness of a pectin-nano zero-valent iron-based nanocomposite in adsorbing heavy metals in bimetallic form (chromium‑lead mixture), along with assessing its antibacterial properties. The nanocomposite was synthesized using a straightforward dispersion method, employing eco-friendly components like biocompatible pectin sourced from banana peels and nano-scale zero-valent iron. Analytical characterization confirmed the formation of stable, nano-crystalline particles with active interactions between the functional groups of pectin and nano iron. Batch adsorption experiments optimized various parameters such as pH, adsorbent dosage, contact time, metal ion concentration, and temperature to enhance bimetal removal from water. The optimal conditions were determined as pH 8.0, a temperature of 40 °C, 1.0 g/L adsorbent dosage, 75 mg/l initial bimetal concentration, and a contact time of 30 min. Further assessments revealed that the nanocomposite did not induce phytotoxic or ecotoxic effects, confirming its non-toxicity and environmental safety. Biocompatibility studies conducted using zebrafish models showed no adverse effects on hatching, survival, or heart rate. These findings underscore the potential of the nanocomposite as a sustainable and efficient solution for heavy metal remediation in water treatment process.

Evaluation of drug release efficiency and antibacterial property of a pH-responsive dextran-based silver nanocomposite hydrogel

The bioavailability of curcumin (CUR), a highly lipophilic and commonly used anticancer drug, is mainly affected by its poor solubility in aqueous environment and quick metabolism. These challenges can be met by employing delivery systems. Nanocomposite materials have been used as delivery systems to enhance the solubility and dissolution rate of the drug. This study aims to develop dextran-graft-poly(4-acryloylmorpholine) silver nanocomposite using a microwave-assisted method to evaluate its drug-release efficiency and antimicrobial activity. The materials were characterized by FT-IR, FE-SEM, EDS, XRD, HR-TEM, TGA, and BET techniques. Drug loading and release efficiency were evaluated using CUR as the model drug. The swelling and drug release studies were conducted in buffer solutions of pH 1.2 and 7.4. Staphylococcus aureus and Escherichia coli were employed to evaluate the antibacterial activity. The cytotoxicity was assessed by MTT assay against the breast MCF-10. Higher swelling and drug release were observed at pH 1.2 than 7.4. Nanocomposite hydrogel exhibited antibacterial activity against the tested bacterial strains. Cytotoxicity study proved the safety of the developed matrix. The results suggest the developed nanocomposite hydrogel to be a promising polymer matrix for the sustained release of CUR for cancer treatment that requires infectious control.

Three-Dimensional Printed Filters Based on Poly(ethylene glycol) Diacrylate Hydrogels Doped with Silver Nanoparticles for Removing Hg(II) Ions from Water

Nowadays, due to water pollution, more and more living beings are exposed to dangerous compounds, which can lead to them contracting diseases. The removal of contaminants (including heavy metals) from water is, therefore, a necessary aspect to guarantee the well-being of living beings. Among the most used techniques, the employment of adsorbent materials is certainly advantageous, as they are easy to synthesize and are cheap. In this work, poly(ethylene glycol) diacrylate (PEGDA) hydrogels doped with silver nanoparticles (AgNPs) for removing Hg(II) ions from water are presented. AgNPs were embedded in PEGDA-based matrices by using a photo-polymerizable solution. By exploiting a custom-made 3D printer, the filters were synthesized. The kinetics of interaction was studied, revealing that the adsorption equilibrium is achieved in 8 h. Subsequently, the adsorption isotherms of PEGDA doped with AgNPs towards Hg(II) ions were studied at different temperatures (4 °C, 25 °C, and 50 °C). In all cases, the best isotherm model was the Langmuir one (revealing that the chemisorption is the driving process and the most favorable one), with maximum adsorption capacities equal to 0.55, 0.57, and 0.61 mg/g, respectively. Finally, the removal efficiency was evaluated for the three temperatures, obtaining for 4 °C, 25 °C, and 50 °C the values 94%, 94%, and 86%, respectively.

The Synergistic Effect of Biosynthesized Silver Nanoparticles and Phytocompound as a Novel Approach to the Elimination of Pathogens

Due to the wide applications of silver nanoparticles (AgNPs), research on their ecological synthesis has been extensive in recent years. In our study, biogenic silver nanoparticles were synthesized extracellularly using the white rot fungus Trametes versicolor via two cultivation methods: static and shaking. The cell filtrate of the fungus was used as a reducing agent in the process of nanoparticle synthesis. Characterization of the obtained nanoparticles was carried out using UV-VIS spectroscopy and scanning electron microscopy. The biosynthesized nanoparticles have antimicrobial potential against pathogenic bacteria, particularly in Gram-negative strains. The bactericidal effect was obtained for E. coli at a concentration of 7 µg/mL. The use of higher concentrations of compounds was necessary for Gram-positive bacteria. Taking into account the problem of the risk of cytotoxicity of AgNPs, combined therapy using a phytochemical was used for the first time, which was aimed at reducing the doses of nanoparticles. The most representative synergistic effect was observed in the treatment of 5 µg/mL silver nanoparticles in combination with 15 µg/mL ursolic acid against E. coli and P. aeruginosa with a bactericidal effect. Moreover, the coadministration of nanoparticles considerably reduced the growth of both Staphylococcus strains, with a bactericidal effect against S. aureus. The viability test confirmed the strong synergistic effect of both tested compounds. Silver nanoparticles synthesized using the T. versicolor showed excellent antibacterial potential, which opens perspectives for future investigations concerning the use of the nanoparticles as antimicrobials in the areas of health.

Silver Nanoparticles for Waste Water Management

Rapidly increasing industrialisation has human needs, but the consequences have added to the environmental harm. The pollution caused by several industries, including the dye industries, generates a large volume of wastewater containing dyes and hazardous chemicals that drains industrial effluents. The growing demand for readily available water, as well as the problem of polluted organic waste in reservoirs and streams, is a critical challenge for proper and sustainable development. Remediation has resulted in the need for an appropriate alternative to clear up the implications. Nanotechnology is an efficient and effective path to improve wastewater treatment/remediation. The effective surface properties and chemical activity of nanoparticles give them a better chance to remove or degrade the dye material from wastewater treatment. AgNPs (silver nanoparticles) are an efficient nanoparticle for the treatment of dye effluent that have been explored in many studies. The antimicrobial activity of AgNPs against several pathogens is well-recognised in the health and agriculture sectors. This review article summarises the applications of nanosilver-based particles in the dye removal/degradation process, effective water management strategies, and the field of agriculture.

Recent advancements in engineered biopolymeric-nanohybrids: A greener approach for adsorptive-remediation of noxious metals from aqueous matrices

Industrial wastewater is causing serious health problems due to presence of large concentrations of toxic metals. Removal of these metals is still a big challenge using pristine natural biopolymers due to their low surface area, water solubility, and poor recovery. Developing biopolymeric composites with other materials has attained attention because they possess a high surface area and structural porosity, high reactivity, and less water solubility. In simple words, biopolymeric nanohybrids have great adsorption capacity for heavy metals. Biopolymeric materials are abundant, low cost, biodegradable, and possess different functional moieties (carboxyl, amine, hydroxyl, and carbonyl) which play a vital role to adsorb metal ions through various inter-linkages (i.e., electrostatic, hydrogen bonding, ion exchange, chelation, etc.). Biopolymeric nanohybrids have been proven a potent tool in environmental remediation such as the abatement of heavy metal ions from polluted water. Herein, we have reported the adsorption potential of various biopolymers (cellulose, chitosan, pectin, gelatin, and silk proteins) for the removal of heavy metals. This review discusses the suitability of biopolymeric nanohybrids as an adsorbent for heavy metals, their synthesis, modification, adsorption potential, and adsorption mechanism along with best fitted thermodynamic and kinetic models. The influence of pH, contact time, and adsorbent dose on adsorption potential has also been discussed in detail. Lastly, the challenges, research gaps and recommendations have been presented. This review concludes that biopolymers in combination with other materials such as metal-based nanoparticles, clay, and carbon-based materials are excellent materials to remove metallic ions from wastewater. Significant adsorption of heavy metals was obtained at a moderate pH (5-6). Contact time and adsorbent dose also affect the adsorption of heavy metals in certain ways. The Pseudo-first order model fits the data for the initial period of the first step of the reaction. Kinetic studies of different adsorption processes of various biopolymeric nanohybrids described that for majority of bionanohybrids, Pseudo-second order fitted the experimental data very well. Functionalized biopolymeric nanohybrids being biodegradable, environment friendly, cost-effective materials have great potential to adsorb heavy metal ions. These may be the future materials for environmental remediation.

Behavior and mechanism of the adsorption of lead by an eco-friendly porous double-network hydrogel derived from keratin

In this study, a novel eco-friendly porous double-network keratin/polyacrylic acid (keratin-PAA) hydrogel was prepared using the one-pot method to improve the adsorption performance of the hydrogel toward Pb(II). The obtained porous keratin-PAA hydrogel was then characterized using nitrogen adsorption-desorption isotherms, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The interaction mechanism of Pb(II) and the keratin-PAA hydrogel was further investigated using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The results showed that keratin-PAA hydrogel was successfully synthesized, with a specific surface area of 49.35 m²/g and a uniform pore distribution of 6.20 nm. The synthesized keratin-PAA hydrogel only took 6 min to adsorb nearly 70% of Pb(II) from the solution because of the interconnected porous network. The keratin-PAA hydrogel also showed a maximal adsorption amount of 234.6 mg/g, and satisfactory selectivity toward Pb(II). The adsorption kinetics of the keratin-PAA hydrogel binding to Pb(II) could be better described by the pseudo-second-order model, whereas the adsorption isotherms could be fitted using the Langmuir equation; this suggested that chemisorption was the main rate-limiting step. The XPS and FT-IR analysis results indicated that the sulfur-, nitrogen- and oxygen-containing groups in the keratin-PAA hydrogel were the main binding sites for Pb(II). In real aqueous samples, the keratin-PAA hydrogel could remove 93-104% of Pb(II). It is clear that the keratin-PAA hydrogel is an outstanding adsorbent material for the removal of Pb(II) from aqueous samples.

The role of surface functional groups of pectin and pectin-based materials on the adsorption of heavy metal ions and dyes

Natural macromolecules have been used to adsorb pollutants including heavy metal ions and organic dyes due to low-cost, accessible, biodegradable, and eco-friendly advantages. Pectin, an important natural polymer, possesses abundant carboxyl and hydroxyl functional groups that can interact with the metal and organic cations via electrostatic interaction; as well as be modified by other chemicals for preparing hybrid and composite materials. The resultant materials have been employed to remove pollutants from aqueous solution; the importance of chemical composition was unlocked. Here, we reviewed contaminant removal by pectin, and pectin-based hybrid and composite materials, and highlighted the role of functional groups on pollutant removal. The removal of heavy metal ions was mainly due to surface coordination, while that of organic cations to electrostatic interactions of the functional groups. Moreover, the influence of initial contaminant concentration was critically discussed. The comprehensive review can provide valuable information on pectin and its application in contaminant removal.

Application of the Zimm-Bragg Model to the Removal of Azo Dyes with Pectin

In this work, the ability of pectin (Pec) to remove direct red 80 (DR80), Congo red (CR), methyl orange (MO), and methyl red (MR) was studied. The removal percentages under adequate pH and ionic strength conditions were as follows: DR80 (99.5%), CR (99.8%), MO (88.6%), and MR (68%), showing that this methodology is efficient to remove azo dyes. The proposed method included the addition of native Pec to the dye aqueous solution and the formation of a gel that occurred when a calcium salt solution was added. This gel retains the molecules adsorbed onto the molecular surface of Pec through hydrogen bonds and electrostatic and hydrophobic interactions. To our knowledge, it is the first time that the Zimm-Bragg model is used to describe the removal of azo dyes with native Pec. This model includes two parameters: $K_u$ (nucleation constant), which is related to the tendency exerted by a dye molecule attached to the Pec to bind to other molecules present in the aqueous phase, and $U$ (cooperativity parameter), which determines the aggregation capacity of the dye molecules already attached to the Pec. This model fits the experimental isotherms very well, suggesting that Pec binds single molecules and dye aggregates. The obtained results in the values of $K_u$ ranged from 922 mol/kg (MR) to 1,157,462 mol/kg (CR), and $U$ varied from 2.51 (MR) to 169.19 (MO). These results suggest that the use of Pec is a viable option to remove azo dyes from aqueous effluents and that the Zimm-Bragg model fits adequately the isotherms of dyes that have a high tendency to form aggregates.

Silver Nanoparticles for Water Pollution Monitoring and Treatments: Ecosafety Challenge and Cellulose-Based Hybrids Solution

Silver nanoparticles (AgNPs) are widely used as engineered nanomaterials (ENMs) in many advanced nanotechnologies, due to their versatile, easy and cheap preparations combined with peculiar chemical-physical properties. Their increased production and integration in environmental applications including water treatment raise concerns for their impact on humans and the environment. An eco-design strategy that makes it possible to combine the best material performances with no risk for the natural ecosystems and living beings has been recently proposed. This review envisages potential hybrid solutions of AgNPs for water pollution monitoring and remediation to satisfy their successful, environmentally safe (ecosafe) application. Being extremely efficient in pollutants sensing and degradation, their ecosafe application can be achieved in combination with polymeric-based materials, especially with cellulose, by following an eco-design approach. In fact, (AgNPs)-cellulose hybrids have the double advantage of being easily produced using recycled material, with low costs and possible reuse, and of being ecosafe, if properly designed. An updated view of the use and prospects of these advanced hybrids AgNP-based materials is provided, which will surely speed their environmental application with consequent significant economic and environmental impact.

Alginate-based magnetic nanosorbent immobilized with aptamer for selective and high adsorption of Hg2+ in water samples

Alginate-coated magnetic nanocluster (MNC) immobilized with Hg²⁺-specific aptamer was synthesized to obtain the nanosorbent with high adsorption capacity and high selectivity for trace analysis of inorganic mercury (Hg²⁺) in water samples. Magnetite nanoparticle was first synthesized by a co-precipitation of iron precursors in the presence of alginate to obtain alginate-coated MNC, followed by immobilization with avidin. Hg²⁺-Specific DNA aptamer labeled with biotin was then conjugated on the MNC surface via specific avidin-biotin interaction to form aptamer-immobilized MNC. Coating the MNC with alginate can improve its water dispersibility and also increase its adsorption capacity toward Hg²⁺ (350 mg/g). It exhibited high selectivity through thymine-Hg²⁺-thymine (T-Hg²⁺-T) interaction with high tolerance to other foreign ions. This nanosorbent showed linearity over the Hg²⁺ concentration range of 0.2-10 μg/L with a correlation coefficient of 0.9977, limit of detection of 0.46 μg/L, and enrichment factor of 13. Moreover, it also showed a potential for detection of Hg²⁺ in drinking and tap water samples with satisfactory recoveries.