Extraction of cobalt ions from aqueous solution by microgels for in-situ fabrication of cobalt nanoparticles to degrade toxic dyes: A two fold-environmental application

Copper nanoparticles loaded gelatin/ polyvinyl alcohol/ guar gum-based 3D printable multimaterial hydrogel for tissue engineering applications

Hydrogels are becoming increasingly significant in tissue engineering because of their numerous benefits, including biocompatibility, biodegradability, and their ability to provide a supportive structure for cell proliferation. This study presents the synthesis and characterization of a new multimaterial hydrogel with 3D-printing capabilities composed of copper nanoparticle-reinforced gelatin, polyvinyl alcohol (PVA), and guar gum-based biomaterials intended for tissue engineering applications. Combining CuNPs aims to enhance the hydrogel's antibacterial properties, mechanical strength, and bioactivity, which are essential for successful tissue regeneration. Hydrogels are chemically cross-linked with glyoxal and analyzed through different assessments to examine the compressive behavior, surface morphology, sorbing capacity, biocompatibility, thermal stability, and degradation properties. The results demonstrated that including CuNPs significantly improved the hydrogel's compressive modulus (4.18 MPa) for the hydrogel with the CuNPs and provided better antibacterial activity against common pathogens with controlled degradation. All the hydrogels exhibited a lower coefficient of friction, which was below 0.1. In vitro cell culture studies using chondrocytes indicated that the CuNPs-loaded hydrogel supported cell proliferation and growth of chondrogenic genes such as collagen type II (COL2) and aggrecan (ACAN). The biocompatibility and enhanced mechanical properties of the multimaterial hydrogel make it a promising candidate for developing customized, patient-specific tissue engineering scaffolds.

Thermodynamic, kinetic, and equilibrium studies of Cu(II), Cd(II), Ni(II), and Pb(II) ion biosorption onto treated Ageratum conyzoid biomass

The issue of environmental contamination, particularly caused by the existence of heavy metal particles, is a major and widely recognized subject that receives substantial global attention. The remediation of Cu(II), Cd(II), Ni(II), and Pb(II) ionic metal particles from synthetic wastewater using chemically treated plant leaves of Ageratum conyzoides (TAC) as a biosorbent was investigated. The biosorption process was implemented utilizing a batch system, wherein several operational parameters were considered, including temperature, pH, agitation time, biosorbent dosage, and initial concentration of the metal ion. Langmuir, Freundlich, Temkin, and D-R isotherm models were used to evaluate equilibrium data. The analyzed parameter exhibits characteristics that were best fitted with the Langmuir isotherm. The observed biosorption capacities (qm) of Cu(II), Pb(II), Ni(II), and Cd(II) ions on the TAC were measured as 51.573, 30.49, 33.53, and 35.91 mg/g, respectively, at a temperature of 22 °C. The affinity sequence of these metal ions follows the order Cu(II) > Pb(II) > Ni(II) > Cd(II). The measured values for the biosorption free energy change (ΔG) of Cu(II), Pb(II), Cd(II), and Ni(II) metal ions ranged from -1.017 to -4.723, -1.368 to -3.612, -2.785 to -5.21, and -1.047 to -5.135 kJ/mol, respectively. The enthalpy (ΔH) for Cu(II), Pb(II), Cd(II), and Ni(II) were determined to be +19.33, +6.82, +14.83, and +38.07 kJ/mol, respectively. Similarly, the corresponding entropy changes (ΔS) for the same series of metal ions were recorded as +0.075, +0.064, +0.063, and +0.135 kJ/mol.K. The pseudo-second-order kinetic models yielded superior outcomes in comparison to the pseudo-first-order kinetic models. The findings of the experiment indicated that the TAC demonstrates favorable efficacy in extracting all four metal ions. Hence, the utilization of biomass derived from Ageratum conyzoides leaves has proven to be a viable and economically feasible approach for biosorption of all four metals.

Silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) microgels: Extraction of palladium (II) ions and in situ formation of palladium nanoparticles for pollutant reduction

Most of the transition metal ions and organic dyes are toxic in nature. Therefore, their removal from water is imperative for human health. For this purpose, various types of systems have been developed to tackle either transition metal ions or organic dyes individually. A core-shell microgel system is introduced which is capable of effectively removing both types (toxic organic dyes and transition metal ions) of pollutants. A long-rod-shaped silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) S@P(CS-NIPAM-MAA) S@P(CNM) core-shell microgel system was developed by free radical precipitation polymerization method (FRPPM). S@P(CNM) was utilized as an adsorbent for extracting palladium (II) (Pd (II)) ions from water under different concentrations of S@P(CNM), several agitation times, palladium (II) ion content, and pH levels. The adsorption data of Pd (II) ions on S@P(CNM) was evaluated by various adsorption isotherms. The kinetic study was investigated by employing pseudo-2nd order (Ps2O), Elovich model (ElM), intra-particle diffusion (IPDM), and pseudo-1st order (Ps1O). Additionally, palladium nanoparticles (Pd NPs) were generated via in-situ reduction of adsorbed Pd (II) ions within the P(CNM) shell region of S@P(CNM). The resulting Pd NPs loaded S@P(CNM) exhibited the capability to reduce organic pollutants like methyl orange (MeO), 4-nitrophenol (4NiP), methylene blue (MeB), and Rhodamine B (RhB) from aqueous medium. 0.766 min-1, 0.433 min-1, 0.682 min-1, and 1.140 min-1 were the values of pseudo 1st order rate constant (kobs) for catalytic reduction of MeB, 4NiP, MeO, and RhB respectively. The S@Pd-P(CNM) system exhibits significant catalytic potential for various organic transformations.

Exploring microgel adsorption: synthesis, classification, and pollutant removal dynamics

Microgels have gained significant importance for the removal of pollutants owing to their stimulus-responsive behavior, high stability, and reusable capacity. However, despite these advantages, several hurdles need to be overcome to fully maximize their potential as effective adsorbents for eradicating various contaminants from the environment, such as metallic cations, organic compounds, anions, harmful gases, and dyes. Therefore, a critical review on the adsorption of pollutants by microgels is needed. In this regard, this review presents the latest developments in the adsorptive properties of microgels. The synthetic methods, architectural structures, and stimulus-responsive behavior of microgels are explained in detail. In addition, this review explores various factors that directly influence the adsorption of pollutants by microgels, such as pH, feed composition, content of pollutants, content of comonomers, agitation time, temperature, microgel dose, nature of both adsorbates (pollutants) and adsorbents (microgels), nature of the medium, and ionic strength. Various adsorption isotherms are also explored together with the kinetic aspects of the adsorption process to provide a comprehensive understanding.

Chitosan-grafted hydrogels for heavy metal ion adsorption and catalytic reduction of nitroaromatic pollutants and dyes

Chitosan-grafted-poly(acrylic acid) (CS-g-PAA) and chitosan-grafted- poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (CS-g-P(AA-co-AMPS)) hydrogels were synthesized and then employed as adsorbents for the effective removal of Cu2+ and other heavy metal ions. The effect of hydrogel's composition on the Cu2+ adsorption was explored. The CS-g-PAA hydrogel demonstrated a superior adsorption capacity compared to pristine CS, PAA hydrogel, and CS-g-P(AA-co-AMPS) hydrogels. The adsorption followed the Langmuir isotherm model, and the pseudo-second order kinetic model. Additionally, the CS-g-PAA hydrogel exhibited relatively high adsorption performances toward Cr3+, Co2+, Ni2+, Pb2+, and Zn2+. Metal ions adsorbed within CS-g-PAA hydrogels underwent reduction to their corresponding metallic states and were reutilized as catalysts for the reduction of 4-nitrophenol. The comparative catalytic performances of the metal species in the hydrogel were in the order of Cu > Ni > Co > Zn. The reduction efficiency of Cu-CS-g-PAA increased with increased catalyst dosage, NaBH4 concentration, and temperature. A very low activation energy of 3.7 kJ/mol was observed. The catalyst maintained high catalytic performance even when subjected to real water samples and proved its reusability for up to three cycles. Moreover, the catalyst could effectively reduce 2-nitrophenol and methyl orange.

Microfluidic Fabrication of Monodisperse and Recyclable TiO2-Poly(ethylene glycol) Diacrylate Hybrid Microgels for Removal of Methylene Blue from Aqueous Medium

Nearly monodisperse titanium oxide-polyethylene glycol diacrylate [TiO2-P(EGDA)] hybrid microbeads containing 0.5 wt % TiO2 nanoparticles entrapped within a P(EGDA) cross-linked polymeric network were synthesized using a modular Lego-inspired glass capillary microfluidic device. TiO2-P(EGDA) hybrid microgels were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and thermogravimetric analysis. The fabricated TiO2-P(EGDA) hybrid microgel system showed 100% removal efficiency of methylene blue (MB) from its 1-3 ppm aqueous solutions after 4 h of UV light irradiation at 0.2 mW/cm2 at the loading of 25 g/L photocatalyst beads in the reaction mixture, corresponding to the loading of naked TiO2 of just 0.025 g/L. No decrease in photocatalytic efficiency was observed in 10 repeated runs with recycled photocatalyst using a fresh 1 ppm MB solution in each cycle. The rate of photocatalytic degradation was controlled by the UV light irradiance, catalyst loading, and the initial dye concentration. Physical adsorption of MB onto the surface of composite microgel was also observed. The adsorption data was best fitted with the Langmuir adsorption isotherm and the Elovich kinetic model. TiO2-P(EGDA) microgel beads are biocompatible, can be prepared with a tunable size in the microfluidic device, and can easily be separated from the reaction mixture by gravity settling. The TiO2-P(EGDA) system can be used for the removal of other toxic dyes and micropollutants from industrial wastewater.

Synthesis and Characterization of Iron-Rich Glauconite Nanorods by a Facile Sonochemical Method for Instantaneous and Eco-friendly Elimination of Malachite Green Dye from Aquatic Environments

Novel glauconite nanorods (GNRs) were synthesized by the sonication-induced chemical expansion and scrolling process of natural glauconite. The synthetic nanostructure was characterized by different analytical techniques as a superior adsorbent for the malachite green dye (MG). The synthetic GNRs were detected as porous nanorods with an average length of 150 nm to 5 μm, an average diameter of 25 to 200 nm, and a specific surface area of 123.7 m2/g. As an adsorbent for MG, the synthetic GNRs showed superior uptake capacity up to 1265.6 mg/g at the saturation stage, which is higher than most of the recently developed highly adsorbent dyes. The adsorption behavior and mechanistic properties were depicted by using modern and traditional equilibrium modeling. The kinetic assumption of the pseudo-first-order model (R2 > 0.94) and the classic isotherm of the Langmuir equilibrium model (R2 > 0.97) were used to describe the adsorption reactions. The steric investigation demonstrates that each active site on the surface of GNRs can adsorb up to three MG molecules (n = 2.19-2.48) in vertical orientation involving multimolecular mechanisms. Also, the determined active site density (577.89 mg/g) demonstrates the enrichment of the surface of GNRs with numerous adsorption receptors with strong affinity for the MG dye. The energetic study, including Gaussian energy (6.27-7.97 kJ/mol) and adsorption energy (9.45-10.43 kJ/mol), revealed that GNRs had physically adsorbed the dye, which might involve electrostatic attraction, hydrogen bonding, van der Waals forces, and dipole forces. The internal energy, enthalpy, and entropy determined the exothermic and spontaneous uptake of MG.

Dynamic Light Scattering and Its Application to Control Nanoparticle Aggregation in Colloidal Systems: A Review

Colloidal systems and their control play an essential role in daily human activities, but several drawbacks lead to an avoidance of their extensive application in some more productive areas. Some roadblocks are a lack of knowledge regarding how to influence and address colloidal forces, as well as a lack of practical devices to understand these systems. This review focuses on applying dynamic light scattering (DLS) as a powerful tool for monitoring and characterizing nanoparticle aggregation dynamics. We started by outlining the core ideas behind DLS and how it may be used to examine colloidal particle size distribution and aggregation dynamics; then, in the last section, we included the options to control aggregation in the chemically processed toner. In addition, we pinpointed knowledge gaps and difficulties that obstruct the use of DLS in real-world situations. Although widely used, DLS has limits when dealing with complicated systems, including combinations of nanoparticles, high concentrations, and non-spherical particles. We discussed these issues and offered possible solutions and the incorporation of supplementary characterization approaches. Finally, we emphasized how critical it is to close the gap between fundamental studies of nanoparticle aggregation and their translation into real-world applications, recognizing challenges in colloidal science.

State-of-the-art adsorption and adsorptive filtration based technologies for the removal of trace elements: A critical review

Water and wastewater are contaminated with various types of trace elements that are released from industrial activities. Their presence, at concentrations above the permissible limit, will cause severe negative impacts on human health and the environment. Due to their cost-effectiveness, simple design, high efficiency, and selectivity, adsorption, and adsorptive filtration are techniques that have received lots of attention as compared to other water treatment techniques. Adsorption isotherms and kinetic studies help to understand the mechanisms of adsorption and adsorption rates, which can be used to develop and optimize different adsorbents. This state-of-the-art review provides and combines the advancements in different conventional and advanced adsorbents, biosorbents, and adsorptive membranes for the removal of trace elements from water streams. Herein, this review discusses the sources of different trace elements and their impact on human health. The review also covers the adsorption technique with a focus on various advanced adsorbents, their adsorption capacities, and adsorption isotherm modeling in detail. In addition, biosorption is critically discussed together with its mechanisms and biosorption isotherms. In the end, the application of various advanced adsorptive membranes is discussed and their comparison with adsorbents and biosorbents is systematically presented.

π-Electron-Extended Triazine-Based Covalent Organic Framework as Photocatalyst for Organic Pollution Degradation and H2 Production from Water

Herein, we report the efficient preparation of π-electron-extended triazine-based covalent organic framework (TFP-TPTPh COF) for photocatalysis and adsorption of the rhodamine B (RhB) dye molecule, as well as for photocatalytic hydrogen generation from water. The resultant TFP-TPTPh COF exhibited remarkable porosity, excellent crystallinity, high surface area of 724 m2 g−1, and massive thermal stability with a char yield of 63.41%. The TFP-TPTPh COF demonstrated an excellent removal efficiency of RhB from water in 60 min when used as an adsorbent, and its maximum adsorption capacity (Qm) of 480 mg g−1 is among the highest Qm values for porous polymers ever to be recorded. In addition, the TFP-TPTPh COF showed a remarkable photocatalytic degradation of RhB dye molecules with a reaction rate constant of 4.1 × 10−2 min−1 and an efficiency of 97.02% under ultraviolet–visible light irradiation. Furthermore, without additional co-catalysts, the TFP-TPTPh COF displayed an excellent photocatalytic capacity for reducing water to generate H2 with a hydrogen evolution rate (HER) of 2712 μmol g−1 h−1. This highly active COF-based photocatalyst appears to be a useful material for dye removal from water, as well as solar energy processing and conversion.

Accelerating Density Functional Calculation of Adatom Adsorption on Graphene via Machine Learning

Graphene has attracted significant interest due to its unique properties. Herein, we built an adsorption structure selection workflow based on a density functional theory (DFT) calculation and machine learning to provide a guide for the interfacial properties of graphene. There are two main parts in our workflow. One main part is a DFT calculation routine to generate a dataset automatically. This part includes adatom random selection, modeling adsorption structures automatically, and a calculation of adsorption properties. It provides the dataset for the second main part in our workflow, which is a machine learning model. The inputs are atomic characteristics selected by feature engineering, and the network features are optimized by a genetic algorithm. The mean percentage error of our model was below 35%. Our routine is a general DFT calculation accelerating routine, which could be applied to many other problems. An attempt on graphene/magnesium composites design was carried out. Our predicting results match well with the interfacial properties calculated by DFT. This indicated that our routine presents an option for quick-design graphene-reinforced metal matrix composites.

Simultaneous removal of aqueous same ionic type heavy metals and dyes by a magnetic chitosan/polyethyleneimine embedded hydrophobic sodium alginate composite: Performance, interaction and mechanism

Heavy metals and azo dyes caused huge harm to the aqueous system and human health. A magnetic chitosan/polyethyleneimine embedded hydrophobic sodium alginate composite (MCPS) was designed and prepared to simultaneously remove aqueous same ionic type heavy metals and azo dyes. In mono-polluted system, the optimal pH for Cr(VI), MO (methyl orange), Cu(Ⅱ) and MB (methylene blue) were 3, 2, 6 and 12 with a saturated adsorption capacity of 87.53, 66.41, 351.03 and 286.54 mg/g, respectively. Pseudo-second-order was suitable to describe the adsorption kinetics of them and the adsorption isotherms were more consistent with the Langmuir isotherm model being a spontaneous, endothermic, and entropy-increasing process. In binary-polluted system, MCPS possessed simultaneous adsorption for Cr (Ⅵ)-MO and Cu(Ⅱ)-MB pollutants at their optimal pH, in addition, whether in anionic or cationic solution, the removal of heavy metals were promoted with the add of azo dyes but the removal of azo dyes were suppressed with the add of heavy metals. Both Cr (Ⅵ)-MO and Cu(Ⅱ)-MB pollutants could be effectively adsorbed and desorbed from MCPS by changing the pH of the aqueous solution to realize recyclability. Lastly, removal mechanism was revealed in detail by FT-IR, EDS and XPS.

Catalytic reduction of organic pollutants, antibacterial and antifungal activities of AgNPs@CuO nanoparticles-loaded mesoporous silica

In this work, the mesoporous silica MCM-41 was prepared by a hydrothermal method and then modified using silver and copper. The obtained samples were used as antibacterial/antifungal agents and as catalysts for the reduction of the following dyes: Methylene Blue (MB), Congo Red (CR), Methyl Orange (MO), and Orange G (OG). Several parameters affecting the reduction of dyes were investigated and discussed such as the catalyst nature, the initial concentration of the dye, the dye nature, the selectivity of the catalyst in a binary system as well as the catalyst reuse. The catalysts were characterized using XRD, nitrogen sorption measurements, XRF, FTIR, XPS, SEM/EDS, and TEM. XRD, XPS, and TEM analysis clearly showed that the calcination of copper- and silver-modified silica leads to the formation of well-dispersed CuO and AgNPs having sizes between 5 and 10 nm. As determined by XRF analysis, the content of silver nanoparticles was higher compared to CuO in all samples. It has been shown that the dye reduction is influenced by the size and the content of nanoparticles as well as by their dispersions. The catalytic activity was shown to be the highest for the Ag-Cu-MCM(0.05) catalyst with a rate constant of 0.114, 0.102, 0.093, and 0.056 s^-1 for MO, MB, CR, and OG dyes in the single-dye system, respectively. In the binary system containing MB/OG or MB/MO, the catalyst Ag-Cu-MCM(0.05) was more selective toward the MB dye. The reuse of the catalyst for three consecutive cycles showed higher MB conversion in a single system with an increase in reaction time. For antifungal and antibacterial properties, the application of calcined and uncalcined materials toward six different strains showed good results, but uncalcined materials showed the best results due to the synergistic effect between CuO and unreduced species Ag⁺ which are considered responsible for the antibacterial and antifungal action.

Influence of Stacking Sequence on Mechanical Properties of Basalt/Ramie Biodegradable Hybrid Polymer Composites

In this study, the mechanical properties of basalt/ramie/polyester hybrid composite laminates were investigated. A matrix of 45% polyester was used, as it has good bonding properties between fibers. The composite laminates were fabricated using a hand layup technique, with seven layers stacked in different sequences and impregnated in the polyester matrix to create a hybrid configuration. Tensile, flexural, impact, compression, and hardness tests were conducted according to ASTM standards for mechanical characterization. The results showed that the overall stacking sequence of sample number seven (BRBRBRB) had the highest tensile strength at 120 MPa, impact energy at 8 J, flexural strength at 115 MPa, compression strength at 70 MPa, and hardness of 77. Natural fiber-reinforced composites are being used in current automotive industry applications, such as in electric vehicles.

Study on the Adsorption Behavior of Polymeric Dispersants to S-ZnF Particles during Grinding Process

Three sodium polyacrylate copolymers PD0x (Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate or PD01; Poly acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD02 and Poly methyl methacrylate-co-acrylic acid-co-sodium 4-vinylbenzenesulfonate-co-hydroxyethyl methacrylate or PD03) were synthesized as water-based dispersants for grinding red-brown pigment ZnFe_1.2Cr_0.8O₄ particles prepared by the solid phase method (S-ZnF). The particle size distribution, viscosity of suspensions, and adsorption capacity of dispersants were explored by laser particle size analysis, viscometer, and thermogravimetry (TG), respectively. The application of 2 wt.% dispersant PD02 in the S-ZnF suspension ground for 90 min can deliver a finer product with the narrower particle size distribution. The added dispersant PD02 in the grinding process of the S-ZnF particles exhibits a suitable viscosity of the suspension and generates more hydrogen bonds on the S-ZnF particle surface. The sulfonic acid groups (SO₃^-) and carboxylic acid groups (-COO^-) in the dispersant PD02 can also provide a strong charge density, which is favorable for the dispersion and grinding of the S-ZnF particles in the suspensions. Furthermore, the adsorption behavior of polymeric dispersant PD02 adsorbed on the S-ZnF particles surface was simulated and analyzed by adsorption thermodynamic models and adsorption kinetic models. It is indicated that the adsorption thermodynamic behavior of dispersant PD02 adsorbed on the S-ZnF particles surface follows the Langmuir model, and the adsorption process is endothermic and a random process with increased confusion during the grinding process. In addition, the adsorption kinetics of dispersant PD02 adsorbed on the S-ZnF particles surface are more in line with the pseudo-first-order kinetic models. Therefore, the adsorption process of dispersant PD02 on the S-ZnF particles surface can be considered as a single-surface adsorption process.

Synthesis of Iron on Carbon Foam for Use in the Removal of Phenol from Aqueous Solutions

The potential use of magnetic nanopowder for phenol adsorption mobilised on natural grain carbon foam from an aqueous solution was studied. Phenolic compounds are priority pollutants with high toxicity even at low concentrations. A magnetic nanopowder was synthesised by dissolving an iron sponge in nitric acid to produce iron nitrate, which was added to a natural grain mixture with flour as the main ingredient. The synthesised carbon foam was investigated for the effects of initial concentration, time, and TEM (transmission electron microscopy) characterisation. The phenol adsorption increased as the iron content of the carbon foam and the initial concentration increased. A kinetic study showed that the phenol adsorption data adequately covered all the carbon foam samples tested using an equation corresponding to a pseudo-first order chemical reaction. The Freundlich, Langmuir, and Temkin equations were tested for modelling the adsorption isotherms at equilibrium, and it was concluded that the Temkin model fit the experimental data adequately. Due to its exceptional physical and chemical properties, carbon magnetic nanopowder is regarded as an outstanding pollutant absorber in environmental investigations. R² values derived from the pseudo-first-order model exceed 0.99. R² > 0.94 indicates that the Freundlich isotherm provides the best fit to the equilibrium data.

Catalytic degradation of azo dyes by bimetallic nanoparticles loaded in smart polymer microgels

The contamination of water by azo dyes is increasing rapidly due to their waste use in textile industries. These dyes are very toxic for living things. Therefore, it is very important to remove these dyes from water. Various materials are reported for this purpose. Here, the most effective system of bimetallic nanoparticles in smart polymer microgels was prepared. The microgel system of N-isopropylmethacrylamide (NMA) (monomer) and methacrylic acid (MAa) (comonomer) was synthesized by a free radical precipitation polymerization method and then bimetallic (Ag/Ni) nanoparticles were encapsulated into the P(NMA-MAa) microgels by in situ reduction of both silver and nickel salts by NaBH₄ (reductant) after insertion of both (Ag⁺/Ni²⁺) ions. The P(NMA-MAa) microgels and Ag/Ni-P(NMA-MAa) hybrid microgels were characterized with FTIR, UV-vis, TGA, XRD, DLS, EDX, and STEM. The pH and temperature responsive behavior of Ag/Ni-P(NMA-MAa) was also evaluated. The catalytic efficiency of Ag/Ni-P(NMA-MAa) was assessed for degradation of methyl orange (MOr), congo red (CRe), eriochrome black T (EBlT) and methyl red (MRe) dyes under various conditions in aqueous medium. The apparent rate constant (k ₀) value for MOr, CRe, EBlT and MRe was found to be 0.925 min^-1, 0.486 min^-1, 0.540 min^-1 and 0.525 min^-1 respectively. The Ag/Ni-P(NMA-MAa) was found to be an excellent recyclable catalyst.

Micron sized anionic poly (methacrylic acid) microgel particles for the adsorptive elimination of cationic water pollutants

In this article, we reported the micron sized particles of poly (methacrylic acid) (p [MAA]) microgel and explored their applications as anionic adsorbents. The micron sized particles of poly (methacrylic acid) microgel were prepared by a simple inverse suspension polymerization method. The adsorptive elimination of adsorbates of cationic nature including malachite green (MG) and methylene blue (MB) from the aqueous medium was studied systematically. The adsorption tests were carried out using various initial concentrations of dyes and with different amounts of adsorbents. The adsorption equilibrium was established in 60 min. The adsorption capacity of the p (MAA) microgel was found as high as 351 mg/g for MG and 65 mg/g for MB. The maximum removal percentage for MG and MB was recorded as 88 and 68%, respectively. The adsorption data was computed with adsorption isotherm models including Langmuir, Freundlich, and Temkin. The Langmuir model was observed to be more applicable for the adsorption of MG while the adsorption of MB was best matched with Temkin model. The adsorption data was also treated with pseudo first order and pseudo second order kinetic models along with intraparticle diffusion and Elovich models. The pseudo second order kinetic model was most suitable with adsorption of both the MG and MB.

Preparation of Copper Ion Adsorbed Modified Montmorillonite/Cellulose Acetate Porous Composite Fiber Membrane by Centrifugal Spinning

The natural adsorption material montmorillonite (MMT) was selected, and cellulose acetate (CA) was used as the loading substrate to design and prepare a kind of green and environment-friendly recyclable porous composite fiber membrane with good heavy metal ion adsorption performance. Acetic acid modified montmorillonite (HCl-MMT), sodium dodecyl sulfonate modified montmorillonite (SDS-MMT), and chitosan modified montmorillonite (CTS-MMT) were prepared by inorganic modification and organic modification, and the porous MMT/CA composite fiber membrane was constructed by centrifugal spinning equipment. The morphological and structural changes of MMT before and after modification and their effects on porous composite fiber membranes were investigated. The morphology, structure, and adsorption properties of the composite fibers were characterized by scanning electron microscopy (SEM) and atomic absorption spectrometry (ASS). The experimental results showed that the maximum adsorption capacity of Cu²⁺ on the prepared 5 wt% CTS-MMT composite fiber membrane was 60.272 mg/g after 10 h static adsorption. The adsorption of Cu²⁺ by a porous composite fiber membrane conforms to the quasi-second-order kinetic model and Langmuir isothermal adsorption model. The main factor of the Cu²⁺ adsorption rate is chemical adsorption, and the adsorption mechanism is mainly monolayer adsorption.

Construction and Adsorption Performance Study of GO-CNT/Activated Carbon Composites for High Efficient Adsorption of Pollutants in Wastewater

Based on the increasing application requirements for the efficient adsorption of wastewater pollutants, graphene oxide-carbon nanotube/activated carbon (GO-CNT/AC) composites are constructed from the optimal microstructure matching of GO, CNTs, and AC materials by solution impregnation and freeze-drying methods. Three-dimensional structures with nano-micro hierarchical pores are established, with GO and CNTs uniformly dispersed on the AC surface, effectively restrain the agglomeration. The added CNTs played a "spring" role, supporting the gap between the GO sheets and AC matrix. Meanwhile, stable links are formed between GO, CNTs, and AC, realizing the synergistic matching of the microstructure, which provides abundant active absorption sites beneficial for improving the adsorption performance. The influences of the CNT contents, adsorbent amounts, methylene blue (MB) concentrations, and pH values on the adsorption property of GO-CNT/AC composites are systematically investigated. The results show that when the pH value of the MB solution is 13, the CNT concentration is 3 mg/mL and the MB concentration is 200 mg/L, the adsorption property of the composite is the best, with an adsorption capacity of 190.8 mg/g and a removal percentage of 95.4%. Compared with the raw AC, the adsorption capacity and removal percentage of the composites are increased by 73.9% and 72.8%, respectively. The GO-CNT/AC composites exhibit excellent cyclic adsorption performance, with a cyclic stability of 91.8% after six rounds of adsorption-desorption cycles. The kinetic analysis shows that the adsorption process conforms to the PSO kinetic model. By fitting of the IPD model, the adsorption mechanisms of the GO-CNT/AC composites are divided into two adsorption stages and described respectively. This study provides a new way to achieve highly efficient adsorption of pollutants in wastewater.

Preparation of stimuli responsive microgel with silver nanoparticles for biosensing and catalytic reduction of water pollutants

Herein, we report poly(N-isopropylacrylamide/2-acrylamido-2-methylpropane sulfonic acid) microgel fabricated with silver nanoparticles. The identification of copolymerization and functional groups in the bare microgel and those fabricated with silver nanoparticles was examined by Fourier transform infrared spectroscopy. The pH and temperature sensitivity of microgels was studied using dynamic light scattering. Thermogravimetric analysis was carried out to study the thermal stability. X-Ray diffraction patterns indicated the amorphous nature of bare microgel and crystalline nature of those containing silver nanoparticles. A bathochromic shift was found in the surface plasmon resonance of silver nanoparticles present in microgel with increase in pH of the medium. Moreover, the microgel containing silver nanoparticles served as an effective catalyst for reducing the toxic nitroaromatic pollutants and carcinogenic dyes. The microgel containing silver nanoparticles also showed good capability to serve as biosensor for the detection of hydrogen peroxide.

Methacrylic acid based microgels and hybrid microgels

Methacrylic acid based microgels have got much consideration in the last two decades because of their potential uses in different fields owing to their responsive behaviour towards external stimuli. Synthesis, properties and uses of methacrylic acid based microgels and their hybrids have been critically reviewed in this article. With minute change in external stimuli such as pH and ionic strength of medium, these microgels show quick swelling/deswelling reversibly. The methacrylic acid based microgels have been widely reported for applications in the area of nanotechnology, drug delivery, sensing and catalysis due to their responsive behaviour. A critical review of current research development in this field along with upcoming perception is presented here. This discussion is concluded with proposed probable future studies for additional growth in this field of research.

Extraction of copper ions from aqueous medium by microgel particles for in-situ fabrication of copper nanoparticles to degrade toxic dyes

Most of the transition metal ions are toxic and their removal from water is important. For this purpose, nearly monodisperse spherical core shell microgel particles with diameter of 88 ± 3 nm have been synthesized by free radical precipitation polymerization method and characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Extraction of copper ions from water under several conditions of pH, copper ions content and core shell microgel concentrations was undertaken. Several adsorption isotherms were tested to explore the process of adsorption of copper ions on the microgel particles. Kinetics of adsorption process was examined by pseudo first order, pseudo second order, intra-particle diffusion and Elovich models. Copper ions adsorbed in shell region of core shell microgel were reduced to copper nanoparticles. The hybrid microgel was used to reduce organic pollutants such as 4-nitrophenol (4NP), methylene blue (MB), and methyl orange (MO) in aqueous medium. The value of pseudo first order rate constant for catalytic reduction of 4NP, MB, and MO was found 0.602, 0.831, and 0.874 min−1 respectively. The resultant core shell hybrid microgel system can serve as efficient catalyst for numerous other organic transformations.

Methacrylate-Based Polymeric Sorbents for Recovery of Metals from Aqueous Solutions

The industrialization and urbanization expansion have increased the demand for precious and rare earth elements (REEs). In addition, environmental concerns regarding the toxic effects of heavy metals on living organisms imposed an urgent need for efficient methods for their removal from wastewaters and aqueous solutions. The most efficient technique for metal ions removal from wastewaters is adsorption due to its reversibility and high efficiency. Numerous adsorbents were mentioned as possible metal ions adsorbents in the literature. Chelating polymer ligands (CPLs) with adaptable surface chemistry, high affinity towards targeted metal ions, high capacity, fast kinetics, chemically stable, and reusable are especially attractive. This review is focused on methacrylate-based magnetic and non-magnetic porous sorbents. Special attention was devoted to amino-modified glycidyl methacrylate (GMA) copolymers. Main adsorption parameters, kinetic models, adsorption isotherms, thermodynamics of the adsorption process, as well as regeneration of the polymeric sorbents were discussed.

Removal of Cr(VI) by polyaniline embedded polyvinyl alcohol/sodium alginate beads - Extension from water treatment to soil remediation

Efficient nano-scale chromium (Cr) remediating agents used in the water industry may find their application in soil difficult because of the strong aggregation effect. In this study, a millimeter-sized PANI/PVA/SA composite (PPS) was synthesized by embedding polyaniline (PANI) into polyvinyl alcohol (PVA)/sodium alginate (SA) gel beads. Additionally, the PPS was used to recover hexavalent chromium (Cr(VI)) contaminated water and soil to study the remediation impacts and mechanism. Results showed that the PPS was an irregular sphere with a pore size of 24.24 nm and exhibited strong adsorption capacity (83.1 mg/g) for removing Cr(VI) in water. The Cr(VI) adsorption by PPS could be well described with the pseudo-second-order kinetics and the Redlich-Peterson isotherm model, indicating that the chemical reactions were the controlling step in the Cr(VI) adsorption process. PPS also exhibited excellent physicochemical properties (< 13 mg/L TOC release) and reusability (efficiency of 95.25% after four runs) for Cr(VI) removal. Soil incubation results showed that the 5% PPS (5PPS) treatment could efficiently remove 24.17% of total Cr and 52.47% of Cr(VI) in the contaminated soil after 30 days. Meanwhile, the water-soluble and the leaching Cr contents were decreased by 43.37% and 61.78% in the 5PPS group, respectively. Elemental speciation by XPS revealed that Cr(VI) removal from solution and soil proceeded mainly by electrostatic attraction, reduction, and complexation/chelation. The study implied that PPS could be a useful amendment to remediate both the Cr(VI)-contaminated water and soil.

Catalytic behavior and antibacterial/antifungal activities of new MNPs/zeolite@alginate composite beads

In this paper, a new family of composite materials was prepared based on calcium alginate and metal nanoparticle-loaded zeolite omega. Different types of metal nanoparticles (MNPs), namely Cu, Co and Fe, were loaded onto zeolite omega to test the performance of the resulting metal/zeolite@alginate composites towards the catalytic reduction of methylene blue dye. To examine their application field as broadly as possible, these composite beads were also tested as antibacterial and antifungal agents against several types of bacteria. Several techniques such as XRD, XRF, FTIR, XPS, SEM and TGA were used to characterize the samples. The obtained results showed that all the composite bead samples were effective in the reduction of MB dye. The composite Co/Zeolite@ALG with relatively low Co nanoparticle (NP) content was selected as the best performing catalyst due to its reduction of MB dye being completely achieved in 3 min with a rate constant of 1.4 min-1, which was attributed to its highly porous structure. The reuse tests conducted on the best-performing catalyst showed good results which persisted through five successive cycles. For antibacterial and antifungal activities, the Cu/Zeolite@ALG and Fe/Zeolite@ALG composites showed good activity with significant inhibition zones.

Complete life of cobalt nanoparticles loaded into cross-linked organic polymers: a review

The synthesis and use of Co nanoparticles loaded into cross-linked polymers for generation of hydrogen is discussed in detail. The factors affecting hydrogen production have been discussed briefly. The catalytic reduction of dyes and nitroarenes is also discussed in detail.

Photocatalysis: an effective tool for photodegradation of dyes-a review

The disposal of dye-contaminated wastewater is a major concern around the world for which a variety of techniques are used for its treatment. The photocatalytic treatment of dye-contaminated wastewater is one of the treatment methods. Semiconductor-assisted photocatalytic treatment of dye-contaminated wastewater has gained pronounced attention recently. This review outlines the recent advancements in the photocatalytic treatment of dye-contaminated wastewater. The photocatalytic degradation of dyes follows three types of mechanisms: (1) dye sensitization through charge injection, (2) indirect dye degradation through oxidation/reduction, and (3) direct photolysis of dye. Several experimental parameters like initial concentration of dyes, pH, and catalyst dosage significantly affect the photocatalytic degradation of dyes. The photocatalytic materials can be categorized into three generations. The single-component (e.g., ZnO, TiO₂) and multiple component semiconductor metal oxides (e.g., ZnO-TiO₂, Bi₂O₃-ZnO) are categorized as first-generation and second-generation photocatalysts, respectively. The photocatalysts dispersed on an inert solid substrate (e.g., Ag-Al₂O₃, ZnO-C) are classified as third-generation photocatalysts. Finally, we reviewed the challenges that affect the photocatalytic degradation of dyes.

Novel Thermosensitive-co-Zwitterionic Sulfobetaine Gels for Metal Ion Removal: Synthesis and Characterization

Zwitterionic betaine polymers are promising adsorbents for the removal of heavy metal ions from industrial effluents. Although the presence of both negative and positively charged groups imparts them the ability to simultaneously remove cations and anions, intra- and/or inter-chain interactions can significantly reduce their adsorption efficiencies. Therefore, in this study, novel gels based on crosslinked co-polymers of thermosensitive N-isopropylacrylamide (NIPAAM) and zwitterionic sulfobetaine N,N-dimethylacrylamido propyl ammonium propane sulfonate (DMAAPS) were synthesized, characterized, and evaluated for ion removal. Fourier-transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) analyses confirmed the success of the co-polymerization of NIPAAM and DMAAPS to form poly(NIPAAM-co-DMAAPS). The phase transition temperature of the co-polymer increased with increasing DMAAPS content in the co-polymer, indicating temperature-dependent amphiphilic behavior, as evidenced by contact angle measurements. The ion adsorption analyses of the poly(NIPAAM-co-DMAAPS) gels indicated that co-polymerization increased the molecular distance and weakened the interaction between the DMAAPS-charged groups (SO3- and N+), thereby increasing the ion adsorption. The results confirmed that, with a low concentration of DMAAPS in the co-polymer gels (~10%), the maximum amount of Cr3+ ions adsorbed onto the gel was ~58.49% of the sulfonate content in the gel.

Antioxidant and Organic Dye Removal Potential of Cu-Ni Bimetallic Nanoparticles Synthesized Using Gazania rigens Extract

Copper-nickel bimetallic nanoparticles (Cu-Ni BNPs) were fabricated using an eco-friendly green method of synthesis. An extract of synthesized Gazania rigens was used for the synthesis of BNPs followed by characterization employing different techniques including UV/Vis spectrophotometer, FTIR, XRD, and SEM. Spectrophotometric studies (UV-Vis and FTIR) confirmed the formation of bimetallic nanoparticles. The SEM studies indicated that the particle size ranged from 50 to 100 nm. Analysis of the BNPs by the XRD technique confirmed the presence of both Cu and Ni crystal structure. The synthesized nanoparticles were then tested for their catalytic potential for photoreduction of methylene blue dye in an aqueous medium and DPPH radical scavenging in a methanol medium. The BNPs were found to be efficient in the reduction of methylene blue dye as well as the scavenging of DPPH free radicals such that the MB dye was completely degraded in just 17 min at the maximum absorption of 660 nm. Therefore, it is concluded that Cu-Ni BNPs can be successfully synthesized using Gazania rigens extract with suitable size and potent catalytic and radical scavenging activities.