Adsorption kinetics of methyl orange from water by pH-sensitive poly(2-(dimethylamino)ethyl methacrylate)/nanocrystalline cellulose hydrogels

Tailoring amino-functionalized n-alkyl methacrylate ester-based bio-hybrids for adsorption of methyl orange dye: Controllable macromolecular architecture via polysaccharide-integrated ternary copolymerization

Controllable macromolecular architecture formation via polysaccharide integrated ternary copolymerization was explored in the design of amino-functionalized n-alkyl methacrylate ester-based biohybrids. Ternary poly(dimethylaminoethyl methacrylate-co-glycidyl methacrylate-co-hydroxypropyl methacrylate)/sodium-alginate, PDGH/ALG, hybrids were designed using anionic polysaccharide through in-situ radical polymerization. An insight into the effect of ALG on physicochemical structure of ternary hybrids, particularly the interactions between polymeric chains, was created. In addition to incorporation of ALG, the effect of polymerization under cryocondition on mechanical stiffness of hybrids was investigated. Adding 0.5 % ALG to ternary PDGH matrix resulted in a 4.2-fold increase in compressive modulus. Swelling of hybrid hydrogels prepared at 1 °C decreased by 5 times, while a 3.4-fold decrease was observed in hybrid cryogels formed at -18 °C. ALG-rich hybrids showed "salting-in" behavior with increasing salt concentration in NaCl, KCl and MgCl2 solutions, while hybrids with low ALG-content exhibited "salting-out" behavior. The hybrid gels were applied to adsorption of anionic dye methyl orange (MO) from simulated dye wastewater. The adsorption was found to follow Freundlich mechanism and a pseudo-second-order kinetic model. ALG-integrated hybrid gels showed a high desorption efficiency and a longer lifespan during the regeneration process, thus showing potential to be used for anionic dye removal from textile wastewater in industry.

Bifunctional Nanocellulose@MOF composite aerogel for selective fluorescent detection and efficient removal of tetracycline

The antibiotic tetracycline (TC) significantly pollutes water bodies, adversely impacting ecosystems and human health. In this work, a bifunctional platform for simultaneous detection and removal of TC was successfully constructed by in-situ growth of Zr-MOF in BC microspheres. The in-situ growth ensured the stability, while the design of the aerogel microspheres improved the processability, convenience, and recyclability. The macropores and mesopores in the aerogel microspheres significantly improved the molecular mass transfer efficiency, and the sensitivity and selectivity of TC detection and adsorption were improved due to the size-sieving effect of the abundant micropores of Zr-MOF and the supramolecular interaction of the ligand. Owing to the hierarchical pore structure, the adsorption capacity reaches as high as 317.6 mg/g. The enrichment during the adsorption process enhances the interaction between TC and Zr-MOF, thereby significantly improving the detection sensitivity of TC. As expected, BMAT3H5 has a LOD as low as 28 ± 0.012 nM and a KSV as high as 1.89 ± 0.001 × 106 M-1, providing excellent detection performance compared to other work in recent years. The good selectivity to TC was theoretically validated through simulations with Materials Studio software (MS). It provides a novel and practical bifunctional platform for efficient fluorescence detection and adsorption of TC, which has a broad application prospect in the fields of environmental monitoring, water treatment, and food safety testing.

Recent advances and applications of stimuli-responsive nanomaterials for water treatment: A comprehensive review

The development of stimuli-responsive nanomaterials holds immense promise for enhancing the efficiency and effectiveness of water treatment processes. These smart materials exhibit a remarkable ability to respond to specific external stimuli, such as light, pH, or magnetic fields, and trigger the controlled release of encapsulated pollutants. By precisely regulating the release kinetics, these nanomaterials can effectively target and eliminate contaminants without compromising the integrity of the water system. This review article provides a comprehensive overview of the advancements in light-activated and pH-sensitive nanomaterials for controlled pollutant release in water treatment. It delves into the fundamental principles underlying these materials' stimuli-responsive behaviour, exploring the design strategies and applications in various water treatment scenarios. In particular, the article indicates how integrating stimuli-responsive nanomaterials into existing water treatment technologies can significantly enhance their performance, leading to more sustainable and cost-effective solutions. The synergy between these advanced materials and traditional treatment methods could pave the way for innovative approaches to water purification, offering enhanced selectivity and efficiency. Furthermore, the review highlights the critical challenges and future directions in this rapidly evolving field, emphasizing the need for further research and development to fully realize the potential of these materials in addressing the pressing challenges of water purification.

Synthesis of thermally and pH-responsive poly(2-(dimethylamino)ethyl methacrylate)-based hydrogel reinforced with cellulose nanocrystals for sustained drug release

Hydrogels are widely employed in biomedical applications due to their high swelling potential, tailored mechanical properties, biocompatibility, and ability to incorporate drugs to modify their release behavior. This study explored the synthesis of dual stimuli-responsive composite hydrogels by combining poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) with 4, 8, and 12 % (w/w) of cellulose nanocrystals (CNC) through in-situ free-radical polymerization, modifying their properties for topical anti-inflammatory release. Although PDMAEMA-based hydrogels have been known for their responsiveness to pH and temperature stimuli, which are useful for modulating the release profile of drugs, their use as a matrix for anti-inflammatory topical applications remains unexplored. Thus, a comprehensive analysis of CNC concentration's impact on PDMAEMA-based hydrogel structure and physicochemical properties is provided. The incorporation of ibuprofen as an anti-inflammatory model was assessed, providing insights into the potential of these composite hydrogels for sustained drug delivery applications. Overall, the hydrogels exhibited homogenous CNC dispersion, with gel fraction higher than 70 % and ibuprofen load higher than 90 %. The rise in CNC concentration led to an increase hydrogel stiffness. Finally, the CNC incorporation also modified the ibuprofen release to a more sustained profile, following the Peppas-Sahlin model, which may be attractive for developing pharmaceutical devices for different therapeutical scenarios.

An Efficient p-n Heterojunction Copper Tin Sulfide/g-C3N4 Nanocomposite for Methyl Orange Photodegradation

The discharge of toxic dye effluents from industry is a major concern for environmental pollution and toxicity. These toxic dyes can be efficiently removed from waste streams using a photocatalysis process involving visible light. Due to its simple synthesis procedure, inexpensive precursor, and robust stability, graphitic carbon nitride (g-C3N4, or CN) has been used as a visible light responsive catalyst for the degradation of dyes with mediocre performance because it is limited by its low visible light harvesting capability due to its wide bandgap and fast carrier recombination rate. To overcome these limitations and enhance the performance of g-C3N4, it was coupled with a narrow bandgap copper tin sulfide (CTS) semiconductor to form a p-n heterojunction. CTS and g-C3N4 were selected due to their good stability, low toxicity, ease of synthesis, layered sheet/plate-like morphology, and relatively abundant precursors. Accordingly, a series of copper tin sulfide/graphitic carbon nitride nanocomposites (CTS/g-C3N4) with varying CTS contents were successfully synthesized via a simple two-step process involving thermal pyrolysis and coprecipitation for visible-light-induced photocatalytic degradation of methyl orange (MO) dye. The photocatalytic activity results showed that the 50%(wt/wt) CTS/g-C3N4 composite displayed a remarkable degradation efficiency of 95.6% for MO dye under visible light illumination for 120 min, which is higher than that of either pristine CTS or g-C3N4. The improved performance is attributed to the extended light absorption range (due to the optimized bandgap), effective suppression of photoinduced electron-hole recombination, and improved charge transfer that arose from the formation of a p-n heterojunction, as evidenced by electrochemical impedance spectroscopy (EIS), photocurrent, and photoluminescence results. Moreover, the results of the reusability study showed that the composite has excellent stability, indicating its potential for the degradation of MO and other toxic organic dyes from waste streams.

Synthesis of multi-responsive poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles in aqueous solution for application as glucose-sensitive insulin-releasing nanoparticles

Objectives

This study aimed to present an innovative method for synthesizing pH-thermo-glucose responsive poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles via single-step aqueous free radical polymerization.

Methods

The synthesis process involved free radical polymerization in an aqueous solution, and the resulting nanoparticles were characterized for their physical and chemical properties by 1H NMR, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). Insulin-loaded poly(NIPA-co-DMAEMA)-PBA hydrogel nanoparticles were prepared and evaluated for their insulin capture and release properties at different pH and temperature, in addition to different glucose concentrations, with the release profile of insulin quantitatively evaluated using the Bradford method.

Results

1H NMR results confirmed successful PBA incorporation, and DLS outcomes consistently indicated a transition to a more hydrophobic state above the Lower Critical Solution Temperature (LCST) of NIPA and DMAEMA. While pH responsiveness exhibited variation, insulin release generally increased with rising pH from acidic to neutral conditions, aligning with the anticipated augmentation of anionic PBA moieties and increased hydrogel hydrophilicity. Increased insulin release in the presence of glucose, particularly for formulations with the lowest mol % PBA, along with a slight increase for the highest mol % PBA formulation when increasing glucose from 1 to 4 mg/mL, supported the potential of this approach for nanoparticle synthesis tailored for glucose-responsive insulin release.

Conclusions

This work successfully demonstrates a novel method for synthesizing responsive hydrogel nanoparticles and underscores their potential for controlled insulin release in response to glucose concentrations. The observed pH-dependent insulin release patterns and the influence of PBA content on responsiveness highlight the versatility and promise of this nanoparticle synthesis approach for applications in glucose-responsive drug delivery systems.

Graphical abstract

Poly(NIPA) nanoparticles containing PBA moieties are normally synthesized in two or more steps in the presence of organic solvents. Here we propose a new method for the synthesis of multiresponsive hydrogel poly(NIPA-co-DMAEMA)-PBA nanoparticles in aqueous medium in a single reaction to provide a fast and effective strategy for the production of glucose-responsive multi-systems in aqueous media from free radical polymerization.

g-C3N4 Based Photocatalyst for the Efficient Photodegradation of Toxic Methyl Orange Dye: Recent Modifications and Future Perspectives

Industrial effluents containing dyes are the dominant pollutants, making the drinking water unfit. Among the dyes, methylene orange (MO) dye is mutagenic, carcinogenic and toxic to aquatic organisms. Therefore, its removal from water bodies through effective and economical approach is gaining increased attention in the last decades. Photocatalytic degradation has the ability to convert economically complex dye molecules into non-toxic and smaller species via redox reactions, by using photocatalysts. g-C₃N₄ is a metal-free n-type semiconductor, typical nonmetallic and non-toxici polymeric photocatalyst. It widely used in photocatalytic materials, due to its easy and simple synthesis, fascinating electronic band structure, high stability and abundant availability. As a photocatalyst, its major drawbacks are its limited efficiency in separating photo-excited electron-hole pairs, high separated charge recombination, low specific surface area, and low absorption coefficient. In this review, we report the recent modification strategies adopted for g-C₃N₄ for the efficient photodegradation of MO dye. The different modification approaches, such as nanocomposites and heterojunctions, as well as doping and defect introductions, are briefly discussed. The mechanism of the photodegradation of MO dye by g-C₃N₄ and future perspectives are discussed. This review paper will predict strategies for the fabrication of an efficient g-C₃N₄-based photocatalyst for the photodegradation of MO dye.

Removal of methyl orange using combined ZnO/Fe2O3/ZnO-Zn composite coated to the aluminium foil in the presence of simulated solar radiation

In this paper, the optimal preparative conditions (current density, deposition temperature, calcination temperature) for the original electrochemical synthesis of ZnO-Zn coating on aluminum foil support (ZnAF) were examined and determined the application for the removal of methyl orange (MO). Optimal application conditions for removing MO (volume and concentration of a treated solution) were also determined. In the following, four immobilized ZnO/Fe₂O₃ photocatalysts with different molar ratios of Zn to Fe (0.42, 0.84, 1.68, and 3.36) were synthesized via the chemical precipitation method on optimized electrochemically synthesized ZnAF support. Characterization studies of synthesized materials included SEM-EDS and Raman scattering analyses. The efficiency of these catalysts for MO removal in the presence/absence of simulated solar radiation (SSR) was investigated. The adsorption isotherms were investigated, and the results show that the adsorption data were best fitted with the Freundlich adsorption isotherm model. Assessment of the thermodynamic parameters showed that although the adsorption process was weakly endothermic over the range of temperatures studied, the relatively high entropy change gave an overall negative change in Gibbs free energy making the processes spontaneous. In the presence of SSR, the optimal molar ratio of Zn to Fe was determined to be 1.68. The possibility of potential reusing the catalyst was examined six times in a row. The possibility for multiple uses of suspension, which is used for immobilization, was also examined. It was also determined that the application of the 1.68Zn/Fe/ZnAF/H₂O₂/SSR system after the dye removal generates hydrogen at a rate of 186.5 μmol g^-1 after 6 h. Furthermore, in the presence of SSR and using a suspended form of catalyst, the removal efficiency was 1.6 times higher than the efficiency achieved with immobilized ZnO/Fe₂O₃ catalyst. Using the HPLC method for 1.68Zn/Fe/ZnAF/SSR system, five primary intermediates were found to be formed. The applicability of ZnO/Fe₂O₃/ZnAF for removal of other dyes was also examined.

Biodegradable cellulose nanocrystals hydrogels for removal of acid red 8 dye from aqueous solutions

Biodegradable cellulose nanocrystals hydrogels (CNCsH) were synthesized from cellulose nanocrystals (CNCs) which were prepared from office wastepaper (OWP) by a chemical crosslinking method using epicholorohydrin (ECH) as a cross-linker. CNCsH were tested for their swelling behavior and biodegradability and the point of zero charge had been determined. The ability of CNCsH for removing the Acid Red 8 (AR8) anionic dye from its aqueous solution was evaluated. The different parameters affecting removal of the dye, such as pH, initial concentration of dye, content of CNCs, temperature and adsorbent dosage were investigated. The optimum conditions for 68% removal efficiency were pH = 1, initial concentration of dye = 10 ppm, contact time = 105 min, CNCs content = 5% and CNCsH dosage = 0.5 g at 30 °C. The adsorption isotherms, kinetics, and thermodynamic parameters have been studied. The results showed an appropriate fit for Langmuir adsorption isotherm and pseudo-second order kinetics model with an adsorption capacity of 17.12 mg/g. According to the obtained values of thermodynamic parameters, the removal of Acid red 8 by CNCs hydrogels was exothermic spontaneous process.

Water treatment using stimuli-responsive polymers

Stimuli-responsive polymers are a new category of smart materials used in water treatment via a stimuli-induced purification process and subsequent regeneration processes.

Efficient and Rapid Photocatalytic Degradation of Methyl Orange Dye Using Al/ZnO Nanoparticles

ZnO and Aluminum doped ZnO nanoparticles (Al/ZnO NPs) were successfully synthesized by the sol-gel method. Together with the effect of calcination temperatures (200, 300 and 400 °C) and Al dosage (1%, 3%, 5% and 10%) on structural, morphological and optical properties of Al/ZnO NPs, their photocatalytic degradation of methyl orange (MO) dye was investigated. The calcination temperatures at 200, 300 and 400 °C in forming structure of ZnO NPs led to spherical nanoparticle, nanorod and nanoflake structures with a well-crystalline hexagonal wurtzite, respectively. The ZnO NPs calcined at 200 °C exhibited the highest specific surface area and light absorption property, leading to the MO removal efficiency of 80% after 4 h under the Ultraviolet (UV) light irradiation. The MO removal efficiency was approximately two times higher than the nanoparticles calcined at 400 °C. Furthermore, the 5% Al/ZnO NPs exhibited superior MO removal efficiency of 99% in only 40 min which was approximately 20 times enhancement in photocatalytic activity compared to pristine ZnO under the visible light irradiation. This high degradation performance was attributed to the extended light absorption, narrowed band gap and effective suppression of electron-hole recombination through an addition of Al metal.

Modification of epoxy groups of poly(hydroxylmethyl methacrylate-co-glycidyl methacrylate) cryogel with H3PO4 as adsorbent for removal of hazardous pollutants

Poly(hydroxylmethyl methacrylate-co-glycidyl methacrylate) (p(HEMA-GMA)) macroporous cryogel with high density of epoxy groups was synthesized, and the epoxy groups of the cryogel were modified into phosphonate groups. The effects of dye concentrations, adsorption time, pH, salt concentration, and adsorption temperature on the adsorption of Direct Blue-53 (DB-53) and Reactive Blue-160 (RB-160) dyes were studied. The maximum adsorption capacity was found to be 245.3 and 155.8 mg/g (0.255 or 0.119 mmol/g) for the DB-53 and RB-160 dyes, respectively. The higher adsorption capacity achieved for the DB-53 compared with the RB-160 dye can result from the pendant primary amino groups of the DB-53 dye as well as the smaller size of the dye molecule. The Langmuir isotherm model and the pseudo-second-order kinetic model well described the experimental data. The p(HEMA-GMA)-PO₄^2- adsorbent has many operational advantages for the removal of pollutants. It could be a promising adsorbent to be used in industrial wastewater treatment.