Development and application of novel bio-magnetic membrane capsules for the removal of the cationic dye malachite green in wastewater treatment

Integration of metal organic framework nanoparticles into sodium alginate biopolymer-based three-dimensional membrane capsules for the efficient removal of toxic metal cations from water and real sewage

Sodium alginate (SA) biopolymer has been recognized as an efficient adsorbent material owing to their unique characteristics, including biodegradability, non-toxic nature, and presence of abundant hydrophilic functional groups. Accordingly, in the current research work, UiO-66-OH and UiO-66-(OH)2 metal organic framework (MOF) nanoparticles (NPs) have been integrated into SA biopolymer-based three-dimensional (3-D) membrane capsules (MCs) via a simple and facile approach to remove toxic metal cations (Cu2+ and Cd2+) from water and real sewage. The newly configured capsules were characterized by FTIR, SEM, XRD, EDX and XPS analyses techniques. Exceptional sorption properties of the as-developed capsules were ensured by evaluation of the pertinent operational parameters, i.e., contents of MOF-NPs (1-100 wt%), adsorbent dosage (0.001-0.05 g), content time (0-360 h), pH (1-8), initial concentration of metal cations (5-1000 mg/L) and reaction temperature (298.15-333.15 K) on the eradication of Cu2+ and Cd2+ metal cations. It was found that hydrophilic functional groups (-OH and -COOH) have performed an imperative role in the smooth loading of MOF-NPs into 3-D membrane capsules via intra/inter-molecular hydrogen bonding and van der waals potencies. The maximum monolayer uptake capacities (as calculated by the Langmuir isotherm model) of Cd2+ and Cu2+ by 3-D SGMMCs-OH were 940 and 1150 mg/g, respectively, and by 3-D SGMMCs-(OH)2 were 1375 and 1575 mg/g, respectively, under optimum conditions. The as-developed capsules have demonstrated superior selectivity against targeted metal cations under designated pH and maintained >80 % removal efficiency up to six consecutive treatment cycles. Removal mechanisms of metal cations by the 3-D SGMMCs-OH/(OH)2 was proposed, and electrostatic interaction, ion-exchange, inner-sphere coordination bonds/interactions, and aromatic ligands exchange were observed to be the key removal mechanisms. Notably, FTIR and XPS analysis indicated that hydroxyl groups of Zr-OH and BDC-OH/(OH)2 aromatic linkers played vital roles in Cu2+ and Cd2+ adsorption by participating in inner-sphere coordination interactions and aromatic ligands exchange mechanisms. The as-prepared capsules indicated >70 % removal efficiency of Cu2+ from real electroplating wastewater in the manifestation of other competitive metal ions and pollutants under selected experimental conditions. Thus, it was observed that newly configured 3-D SGMMCs-OH/(OH)2 have offered a valuable discernment into the development of MOFs-based water decontamination 3-D capsules for industrial applications.

An Updated Overview of Magnetic Composites for Water Decontamination

Water contamination by harmful organic and inorganic compounds seriously burdens human health and aquatic life. A series of conventional water purification methods can be employed, yet they come with certain disadvantages, including resulting sludge or solid waste, incomplete treatment process, and high costs. To overcome these limitations, attention has been drawn to nanotechnology for fabricating better-performing adsorbents for contaminant removal. In particular, magnetic nanostructures hold promise for water decontamination applications, benefiting from easy removal from aqueous solutions. In this respect, numerous researchers worldwide have reported incorporating magnetic particles into many composite materials. Therefore, this review aims to present the newest advancements in the field of magnetic composites for water decontamination, describing the appealing properties of a series of base materials and including the results of the most recent studies. In more detail, carbon-, polymer-, hydrogel-, aerogel-, silica-, clay-, biochar-, metal-organic framework-, and covalent organic framework-based magnetic composites are overviewed, which have displayed promising adsorption capacity for industrial pollutants.

Effect of biocomposite production factors on the development of an eco-friendly chitosan/alginate-based adsorbent with enhanced copper removal efficiency

Nowadays, wastewater treatment is a critical concern, particularly regarding the removal of heavy metals through adsorption methods. Extensive research has been conducted on obtaining high-yield and environmentally friendly adsorbents. Natural polymer adsorbents especially have shown promise in ion and organic molecule adsorption. To enhance the practical applicability of adsorbents, the combination of biopolymers to form biocomposites is a promising alternative. In this study, adsorbents based on a 1:1 wt./wt. of chitosan (CS) and alginate (SA) were prepared. The influence of the regeneration route and drying conditions on the copper adsorption capacity was investigated, along with reaction parameters such as contact time, adsorbent particle size, and pH. The highest adsorption capacity was observed in the composite material obtained through a one-pot regeneration process and freeze-dried. The CSAR3L sample exhibited a remarkable adsorption capacity of 288 mg Cu(II)/g after 360 min at 25 °C. The synergistic effect between the CS and SA precursors was confirmed by analyzing the individual precursors and their mechanical mixture. The initial adsorption rates at pH 6 followed the order: CSAR3-L > Bk-CSR3L > Bk-SAR3L + Bk-CSR3L > Bk-SAR3L. The physicochemical and morphological properties of the materials were studied by FTIR, XRD, DLS, XPS, optical microscopy, EDS-SEM, elemental chemical analysis, and TGA-DTG. The utilization of different drying methods resulted in the formation of calcium carbonate crystalline phases in the as-prepared materials, thus creating substantial adsorption active sites. After the adsorption process, hydroxylated copper sulfate phases and a significant decrease in calcium concentration were observed, indicating that an ion exchange adsorption mechanism occurred. The analysis of adsorption kinetics and the shape of the adsorption isotherms, in agreement with the characterization results, suggested the presence of multiple active sites and the formation of a chemisorption monolayer.

The Evaluation of Cellulose Acetate Capsules Functionalized for the Removal of Cd(II)

Cellulose acetate is derived from cellulose and has the characteristics of biodegradability and reusability. So, it has been used for the elimination of toxic compounds capable of producing different diseases, such as cadmium, that result from human and industrial activity. For this reason, capsules functionalized with Cyanex 923 were prepared and characterized by FTIR spectroscopy, Energy Dispersive X-ray Spectroscopy (EDX), and SEM. The functionalized capsules were used for removing and recovering Cd(II) by modifying variables such as HCl concentration in the extraction medium and carrier content in the capsules, among others. The extraction of cadmium from battery leachates and the three isotherm models, Langmuir, Freundlich, and Dubinin Radushkevich, were also tested to model the cadmium removal process. The results showed a favorable physical sorption with a good capacity for extraction and the possibility of reusing the capsules for up to seven cycles without a decrease in the percentage of cadmium recovery.

Triphenylmethane dye (C52H54N4O12) is potentially a hazardous substance in edible freshwater fish at trace level: toxicity, hematology, biochemistry, antioxidants, and molecular docking evaluation study

Malachite green (C₅₂H₅₄N₄O₁₂) is a synthetic dye that is used in textile industries as a colorant and in aquaculture sectors to contain microbial damage. Aquatic contamination of malachite green (MG) has been reported globally. Fish is the highest trophic organism among aquatic inhabitants, highly sensitive to waterborne contaminants (metals, coloring agents, etc.). Toxicity of waterborne chemicals on nontarget organisms can be determined by assessing biomarkers. Assessing blood parameters and tissue antioxidants (enzymatic and nonenzymatic) is useful to evaluate MG toxicity. To initiate the MG toxicity data for freshwater fish (Cyprinus carpio), the median lethal toxicity was primarily evaluated. Then, hematological, blood biochemical (glucose, protein, and cholesterol) and tissue biochemical (amino acids, lipids), and vital tissue (gills, liver, and kidney) antioxidant capacity (CAT, LPO, GST, GR, POxy, vitamin C, and GSH) of C. carpio were analyzed under acute (LC_50-96 h) and sublethal (Treatment I-1/10^th and Treatment II-1/5^th LC_50-96 h) exposure periods (28 days). Molecular docking for MG with hemoglobin was also obtained. Biomarkers examined were affected in the MG-treated groups with respect to the control group. Significant changes (p < 0.05) were observed in hematology (Hb, RBCs, and WBCs), glucose, proteins, lipids and tissue CAT, LPO, and GST activities under acute MG exposure. In sublethal treatment groups, biomarkers studied were significant (p < 0.05) throughout the study period. The potential for MG binding to hemoglobin was tested in this study. MG is potentially a multiorgan toxicant. Literally a chemical that is harmful to the aquatic environment if safety is concerned.

Development of novel MOF-mixed matrix three-dimensional membrane capsules for eradicating potentially toxic metals from water and real electroplating wastewater

The stability and applicability of UiO-66-(NH₂)₂ metal-organic framework (MOF) nanoparticles (NPs) were successfully improved in this study by incorporating them into alginate biopolymer during the manifestation of crosslinking agents-calcium chloride and glutaraldehyde-via a simple, environment-friendly, and facile approach to eradicate potentially toxic metals (PTMs) such as Cr⁶⁺, Cr³⁺, Cu²⁺, and Cd²⁺ from water and real electroplating wastewater. Hydrophilic functional groups (i.e., -OH, -COOH, and -NH₂) are imperative in the smooth loading of UiO-66-(NH₂)₂ MOF- NPs into three-dimensional (3-D) membrane capsules (MCs). The X-ray photoelectron spectroscopy (XPS) results suggested that UiO-66-(NH₂)₂ MOF was effectively bonded in/on the capsule via electrostatic crosslinking between -H₃N⁺ and -COO^-. Scanning electron microscopy results revealed a porous honeycomb configuration of the 3-D SGMMCs (S: sodium alginate, G: glutaraldehyde, M: MOF NPs, and MCs: membrane capsules). The maximum monolayer absorption capacities for Cr⁶⁺, Cr³⁺, Cu²⁺, and Cd²⁺ were 495, 975, 1295, and 1350 mg/g, respectively. The results of Fourier transform infrared spectroscopy and XPS analyses showed that electrostatic attraction and ion exchange were the main processes for PTM removal used by the as-developed 3-D SGMMCs. The as-developed 3-D SGMMCs exhibited outstanding selectivity for removing the targeted PTMs under the specified pH/conditions and maintained >80% removal efficiency for up to six consecutive treatment cycles. Notably, > 60% removal efficiencies for Cr⁶⁺ and Cu²⁺ were observed when treating real electroplating wastewater. Therefore, the as-developed 3-D SGMMCs can be used as an exceptional multifunctional sorbent to remove and recover PTMs from real electroplating wastewater.

Characterization of Immobilized Magnetic Fe3O4 Nanoparticles on Raoultella Ornithinolytica sp. and Its Application for Azo Dye Removal

A high-performance immobilized bacterial strain coated with magnetic iron oxide nanoparticles was used for Basic Blue 41 azo dye (BB 41 dye) decolorization. To create the coated bacterial strain, Raoultella Ornithinolytica sp. was isolated and identified under the accession number KT213695, then coated with manufactured magnetic iron oxide nanoparticles. SEM and SEM-EDX were used to characterize the coated bacteria and validate its morphological structure formation. The coated Raoultella Ornithinolytica sp. A1 (coated A1) generated a 95.20% decolorization for BB 41 dye at 1600 ppm starting concentration with an optimal dose of coated A1 5 mL/L, pH 8, under static conditions for 24 h at 37 °C. Continuous batch cycles were used, with BB 41 dye (1600 ppm) added every 24 h four times, to achieve a high decolorization efficiency of 80.14%. Furthermore, the metabolites of BB 41 dye biodegradation were investigated by gas chromatographic-mass spectrum analysis (GC-MS) and showed a less toxic effect on the bioindicator Artemia salina. Additionally, 5 mL/L of coated A1 demonstrated the highest decolorization rate (47.2%) when applied to a real wastewater sample after 96 h with a consequent reduction in COD from 592 to 494 ppm.

Mechanisms of chromium(VI) removal from solution by zeolite and vermiculite modified with iron(II)

Mechanisms of Cr(VI) reduction by Fe(II) modified zeolite (clinoptilolite/mordenite) and vermiculite were evaluated. Adsorbents were treated with Fe(SO4)·7H2O to saturate their exchange sites with Fe(II). However, this treatment decreased their CEC and pHPZC, probably due to the dealumination process. Vermiculite (V-Fe) adsorbed more Fe(II) (21.8 mg g-1) than zeolite (Z-Fe) (15.1 mg g-1). Z-Fe and V-Fe were used to remove Cr(VI) from solution in a batch test to evaluate the effect of contact time and the initial concentration of Cr(VI). The Cr(VI) was 100% reduced to Cr(III) by Z-Fe and V-Fe in solution at 18 mg L-1 Cr(VI) after 1 min. Considering that 3 mol of Fe(II) are required to reduce 1 mol of Cr(VI) (3Fe+2 + Cr+6 → 3Fe+3 + Cr+3), the iron content released from Z-Fe and V-Fe was sufficient to reduce 100% of the Cr(VI) in solutions up to 46.8 mg L-1 Cr(VI) and about 90% (V-Fe) and 95% (Z-Fe) at 95.3 mg L-1 Cr(VI). The Fe(II), Cr(III), Cr(VI), and K+ contents of the adsorbents and solutions after the batch tests indicated that the K+ ions from the [Formula: see text] solution were the main cation adsorbed by Z-Fe, while vermiculite did not absorb any of these cations. The H+ of the acidic solution (pH around 5) may have been adsorbed by V-Fe. The release of Fe(II) from Z-Fe and V-Fe involved cation exchange between K+ and H+ ions from solution, respectively. The reduction of Cr(VI) by Fe(II) resulted in the precipitation of Cr(III) and Fe(III) and a decrease in the pH of the solution to < 5. As acidity limits the precipitation of Cr(III) ions, they remained in solution and were not adsorbed by either adsorbent (since they prefer to adsorb K+ and H+). To avoid oxidation, Cr(III) can be removed by precipitation or the adsorption by untreated minerals.

Improving the decolorization activity of Bacillus pumilus W3 CotA-laccase to Congo Red by rational modification

Congo Red (CR) is a typical azo dye with highly toxic and carcinogenic properties. This study aimed to improve the decolorization activity of Bacillus pumilus W3 CotA-laccase for azo dye CR. This work analyzed the interaction between CotA-laccase and CR based on homology modeling and molecular docking. The three amino acids (Gly323, Thr377, Thr418) in the substrate-binding pocket were rationally modified through saturation mutation. Finally, the obtained multi-site mutants T377I/T418G and G323S/T377I/T418G decolorized 76.59% and 59.37% of CR within 24 h at pH 8.0 without a mediator, which were 3.15- and 2.44-fold higher than the wild-type CotA. The catalytic efficiency of the multi-site mutants T377I/T418G and G323S/T377I/T418G to CR were increased by 2.21- and 2.01-fold compared with the wild-type CotA, respectively. The mechanism of activity enhancement of mutants was proposed by structural analysis. This evidence suggests that the mutants T377I/T418G and G323S/T377I/T418G could be used as novel bioremediation tools.

Enhanced oil recovery using hyperbranched polyglycerol polymer-coated silica nanoparticles

Functionalized Fe₃O₄-SiO₂ magnetic nanoparticles (Fe-Si-MNPs) coated with hyperbranched polyglycerol polymer were prepared and tested for oil recovery from oil in water (O/W) emulsions. The structure, chemistry, and surface modifications of the newly developed demulsifier (PSiMNPs) were analyzed, and the percentage demulsification efficiency (%η_dem) was tested at differing concentrations of surfactant (C_sur), oil (C_oil), and demulsifier (D_PSiMNPs). The developed PSiMNPs can be separated from the solution by a magnetic field, regenerated using ethanol, and reused several times. The reported %η_dem was ≥80% for all the studied C_oil. The %η_dem improved as the C_sur and pH decreased, with maximum values of 98.8% and 98.5% achieved at C_sur = 0.05 g/L and a pH = 4, respectively. A D_PSiMNPs = 100 mg/L was sufficient to achieve %η_dem of 99.4% for C_oil = 100 mg/L and slightly decreased to ~93% for C_oil ~4000 mg/L. The PSiMNPs can be reused up to 15 times with a steady %η_dem of 89.1% for C_oil = 100 mg/L and 88.6% for C_oil = 4000 mg/L. The adsorption of oil on the PSiMNPs follows Freundlich isotherm with maximum adsorption capacity (q_max) of 192.8 g/mg and Langmuir constant (b) of 28.06 mg/L for C_oil = 900 mg/L. The q_max of the recycled PSiMNPs slightly decreased to 189.08 g/mg. The kinetic of oil recovery follows the PSO with a K₂ of 0.0169 g/mg. min. Surface modification of Fe-Si-MNPs enhanced the oil adsorption, increased the adsorption capacity, and extended the service life resulting in a better cost and process feasibility.

Environmentally Friendly Polyvinyl Alcohol-Alginate/Bentonite Semi-Interpenetrating Polymer Network Nanocomposite Hydrogel Beads as an Efficient Adsorbent for the Removal of Methylene Blue from Aqueous Solution

Hazardous chemicals like toxic organic dyes are very harmful to the environment and their removal is quite challenging. Therefore there is a necessity to develop techniques, which are environment friendly, cost-effective and easily available in nature for water purification and remediation. The present research work is focused on the development` and characterization of the ecofriendly semi-interpenetrating polymer network (semi-IPN) nanocomposite hydrogels composed of polyvinyl alcohol (PVA) and alginate (Alg) hydrogel beads incorporating natural bentonite (Bent) clay as a beneficial adsorbent for the removal of toxic methylene blue (MB) from aqueous solution. PVA-Alg/Bent nanocomposite hydrogel beads with different Bent content (0, 10, 20, and 30 wt%) were synthesized via external ionic gelation method. The designed porous and steady structure beads were characterized by the use of Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM). The performance of the beads as MB adsorbents was investigated by treating aqueous solutions in batch mode. The experimental results indicated that the incorporation of Bent (30 wt%) in the nanocomposite formulation sustained the porous structure, preserved water uptake, and increased MB removal efficiency by 230% compared to empty beads. Designed beads possessed higher affinity to MB at high pH 8, 30 °C, and fitted well to pseudo-second-order kinetic model with a high correlation coefficient. Moreover, the designed beads had good stability and reusability as they exhibited excellent removal efficiency (90%) after six consecutive adsorption-desorption cycles. The adsorption process was found be combination of both monolayer adsorption on homogeneous surface and multilayer adsorption on heterogeneous surface. The maximum adsorption capacity of the designed beads system as calculated by Langmuir isotherm was found to be 51.34 mg/g, which is in good agreement with the reported clay-related adsorbents. The designed semi-IPN PVA-Alg/Bent nanocomposite hydrogel beads demonstrated good adsorbent properties and could be potentially used for MB removal from polluted water.

Sunlight-assisted degradation of textile pollutants and phytotoxicity evaluation using mesoporous ZnO/g-C3N4 catalyst

Accessibility of adequate safe and fresh water for human consumption is one of the most significant issues throughout the world and extensive research is being undertaken to resolve it. Nanotechnology is now an outstanding medium for water treatment and remediation from microorganisms and organic dyes, as compared to conventional treatment methods. For this task graphitic carbon nitride (g-C3N4) is a potential nanomaterial for environmental remediation, but its photogenerated charge carrier recombination rate restricts its use in practical applications. Hence, in the current study, we used a simple one-step calcination method to synthesize various ratios of ZnO/g-C3N4 binary nanocomposites. The band gap of g-C3N4 is 2.70 eV, but it is shifted to 2.60 eV by the 0.75 : 1 ZnO/g-C3N4 binary nanocomposite. Moreover, phase structure, morphology, thermal stability, oxidation state, elemental analysis, and surface area were evaluated using XRD, SEM, TEM, TGA, XPS, and BET analysis. The optimal ZnO loading content was determined and the mechanism of enhanced photocatalytic activity was studied in detail. The photocatalytic efficiency of the best catalyst was employed for the degradation of textile effluent followed by phytotoxicity evaluation using methylene blue (MB), and rhodamine B (RhB) as a model substrate was tested. Furthermore, the textile effluent treatment analysis discovered that the 75 mg concentration of 0.75 : 1 ZnO/g-C3N4 catalyst degraded up to 80% within 120 min and significantly reduced the concentrations of different physico-chemical parameters of textile effluents. These treated effluents have no phytotoxic effects on fenugreek plants, according to a pot study. It was found that the mesoporous 0.75 : 1 ZnO/g-C3N4 catalyst can be used as an effective and low-cost technique for the degradation of azo dyes in textile wastewaters.

The "Lab4treat" Outreach Experience: Preparation of Sustainable Magnetic Nanomaterials for Remediation of Model Wastewater

The Lab4treat experience has been developed to demonstrate the use of magnetic materials in environmental applications. It was projected in the frame of the European project Mat4Treat, and it was tested several times in front of different audiences ranging from school students to the general public in training and/or divulgation events. The experience lends itself to discuss several aspects of actuality, physics and chemistry, which can be explained by modulating the discussion depth level, in order to meet the interests of younger or more experienced people and expand their knowledge. The topic is relevant, dealing with the recycling of urban waste and water depollution. The paper is placed within the field of water treatment for contaminant removal; therefore, a rich collection of recent (and less recent) papers dealing with magnetic materials and environmental issues is described in the Introduction section. In addition, the paper contains a detailed description of the experiment and a list of the possible topics which can be developed during the activity. The experimental approach makes the comprehension of scientific phenomena effective, and, from this perspective, the paper can be considered to be an example of interactive teaching.

Synchronous Construction of Hierarchical Porosity and Thiol Functionalization in COFs for Selective Extraction of Cationic Dyes in Water Samples

Pore size and functionalization are two critical factors for covalent organic frameworks (COFs) as effective adsorbents. However, due to the low crystallinity of COFs, it is a grand challenge to accomplish pore diameter adjustment and functionalization at the same time. In this work, we developed a simple and ingenious strategy, cutting off linkage, to synchronously construct hierarchical porosity and modify thiol groups in COFs under mild conditions. The hybrid COFs containing disulfide bonds were designed and synthesized, and then the disulfide bonds were cleaved by glutathione, resulting in the formation of thiol groups as well as the increase in pore size caused by skeleton defects. The pore diameter of thiol-functionalized hierarchical porous COFs (denoted as HP-TpEDA-SH) was concentrated at 2.6 and 3.5 nm. Thanks to the electrostatic attraction of thiol groups to cationic dyes and the higher number of available adsorption sites, the maximum extraction amounts of methylene blue (MB), malachite green (MG), and crystal violet (CV) by HP-TpEDA-SH were 2.6, 2.1, and 3.3 times those of microporous COFs under optimal extraction conditions, respectively. The proposed analytical method (solid-phase extraction-high-performance liquid chromatography/ultraviolet (SPE-HPLC/UV)) with HP-TpEDA-SH as the adsorbent showed low detection limits of 1.3, 0.13, and 0.12 μg·L^-1 for MB, MG, and CV, respectively. The recoveries of three spiked water samples ranged from 81.5 to 113.8%, with relative standard deviations (RSDs) less than 9.7%. This work not only opened a new avenue for the preparation of functionalized hierarchical porous COFs but also established an effective method for detecting trace cationic dyes in fishery water.

Improving decolorization of dyes by laccase from Bacillus licheniformis by random and site-directed mutagenesis

BACKGROUND

Dye wastewater increases cancer risk in humans. For the treatment of dyestuffs, biodegradation has the advantages of economy, high efficiency, and environmental protection compared with traditional physical and chemical methods. Laccase is the best candidate for dye degradation because of its multiple substrates and pollution-free products.

METHODS

Here, we modified the laccase gene of Bacillus licheniformis by error-prone PCR and site-directed mutagenesis and expressed in E. coli. The protein was purified by His-tagged protein purification kit. We tested the enzymatic properties of wild type and mutant laccase by single factor test, and further evaluated the decolorization ability of laccase to acid violet, alphazurine A, and methyl orange by spectrophotometry.

RESULTS

Mutant laccase Lacep69and D500G were superior to wild type laccase in enzyme activity, stability, and decolorization ability. Moreover, the laccase D500G obtained by site-directed mutagenesis had higher enzyme activity in both, and the specific activity of the purified enzyme was as high as 426.13 U/mg. Also, D500G has a higher optimum temperature of 70 °C and temperature stability, while it has a more neutral pH 4.5 and pH stability. D500G had the maximum enzyme activity at a copper ion concentration of 12 mM. The results of decolorization experiments showed that D500G had a strong overall decolorization ability, with a lower decolorization rate of 18% for methyl orange and a higher decolorization rate of 78% for acid violet.

CONCLUSION

Compared with the wild type laccase, the enzyme activity of D500G was significantly increased. At the same time, it has obvious advantages in the decolorization effect of different dyes. Also, the advantages of temperature and pH stability increase its tolerance to the environment of dye wastewater.

Polymer Capsules with Hydrophobic Liquid Cores as Functional Nanocarriers

Recent developments in the fabrication of core-shell polymer nanocapsules, as well as their current and future applications, are reported here. Special attention is paid to the newly introduced surfactant-free fabrication method of aqueous dispersions of nanocapsules with hydrophobic liquid cores stabilized by amphiphilic copolymers. Various approaches to the efficient stabilization of such vehicles, tailoring their cores and shells for the fabrication of multifunctional, navigable nanocarriers and/or nanoreactors useful in various fields, are discussed. The emphasis is placed on biomedical applications of polymer nanocapsules, including the delivery of poorly soluble active compounds and contrast agents, as well as their use as theranostic platforms. Other methods of fabrication of polymer-based nanocapsules are briefly presented and compared in the context of their biomedical applications.

A Sharp Jump in Photocatalytic Activity of Elemental Sulfur for Dye Degradation in Alkaline Solution

Elemental sulfur is a low-cost and abundant substance as one of the largest by-products of the oil industry which was widely used in many industrial activities. Cyclo-octasulfur (S₈ ) is one of the sulfur allotropes that is a very stable substance in standard conditions. In this study, we report a low-cost and fast method for the degradation of methyl violet in water under visible light and also sunlight by using elemental sulfur (S₈ ). The results show that sulfur is a good photocatalyst which operates under visible light and can be utilized for degradation of methyl violet. The photocatalytic degradation of methyl violet in acidic, neutral, and alkaline media was investigated, and it was found that the photocatalytic efficiency increases dramatically in alkaline solution. The effects of the initial concentration of the dye, photocatalyst dosage, solution pH, and photocatalyst reusability were investigated. The kinetics of the reaction were studied in detail, and the photocatalytic rate equation was presented.

Effect of Solvent-Derived Highly Luminescent Multicolor Carbon Dots for White-Light-Emitting Diodes and Water Detection

Recently, the multicolor fluorescent carbon dots (CDs) have drawn much attention due to their various applications. Herein, we report multicolor emissive CDs by solvent-controlled and solvent-responded approaches. The blue to red color emissive CDs are obtained by the solvothermal method by varying the solvent during the reaction. The red color emissive CDs (R-CDs) with good quantum yield is obtained in a water medium. The detailed characterization revealed that the solvent controls the particle size, band gap, and nitrogen doping concentration. Specifically, in the protic solvent, the high N content and presence of imine nitrogen are the reason for red emission. However, in an aprotic solvent, the least N doping and a lack of C-O groups are responsible for a blueshift. Interestingly, it was observed that the R-CDs provide a full range of visible color by dispersing in different immiscible solvents. The fluorescence emission in immiscible solvents is redshifted by enhancing the polarity. Moreover, the developed CDs detected the low water concentrations (≤0.2%, v/v) visually and fluorometrically in various organic solvents. Simultaneously, we have employed synthesized CDs in white-light-emitting diodes and fluorescent ink.

Humic acid functionalized magnetic nanomaterials for remediation of dye wastewater under ultrasonication: Application in real water samples, recycling and reuse of nanosorbents

Water pollution by industrial sector is a great problem which hampers the sustainable development goals. Dye containing water effluent poses vast challenge to clean water before its discharge in to the surrounding ecosystem. Herein, we prepared humic acid functionalized Fe₃O₄ nanosorbents through an eco-friendly route and applied for decolorization of carcinogenic dye from water. The nanosorbents was characterized by AFM, BET surface area analyzer, FTIR, SEM-EDX, TEM, TGA/DTG, VSM and XRD. Adsorption experiments were conducted by taking the appropriate amount of dye in different sources of water under ultrasonication. Adsorption process was controlled by chemisorption in nature making pseudo-second-order model most suitable. Multilayer adsorption was taking place on the active sites of nanosorbents showing applicability of Freundlich isotherm model with highest adsorbed amount of 199.986 mg g^-1 at 323 K. Rise in temperature favors the remediation of colored effluent thus positive value of ΔH° (74.234 kJ mol^-1) and negative value of ΔG° shows endothermic and spontaneous nature of adsorption system. Cationic surfactant CTAB favors the adsorption (<80%) while anionic SDS gives very low removal (>48%) because of the micelle formation at the surface of nanosorbents. Decolorization from real water samples shows that the adsorption of malachite green was 97, 90, 91, 87, and 86% for Ganga river water, tap water, well water, hand pump water and submersible water, respectively. The used Fe₃O₄/HA nanosorbents was easily recycled from water samples through 0.1 M HCl and nanosorbents was used up to five cycles with greater percentage of removal at 85%.

Nanomaterials with Tailored Magnetic Properties as Adsorbents of Organic Pollutants from Wastewaters

Water quality has become one of the most critical issue of concern worldwide. The main challenge of the scientific community is to develop innovative and sustainable water treatment technologies with high efficiencies and low production costs. In recent years, the use of nanomaterials with magnetic properties used as adsorbents in the water decontamination process has received considerable attention since they can be easily separated and reused. This review focuses on the state-of-art of magnetic core–shell nanoparticles and nanocomposites developed for the adsorption of organic pollutants from water. Special attention is paid to magnetic nanoadsorbents based on silica, clay composites, carbonaceous materials, polymers and wastes. Furthermore, we compare different synthesis approaches and adsorption performance of every nanomaterials. The data gathered in this review will provide information for the further development of new efficient water treatment technologies.

Development of a novel three-dimensional magnetic polymer aerogel as an efficient adsorbent for malachite green removal

A novel three-dimensional (3D) magnetic bacterial cellulose nanofiber/graphene oxide polymer aerogel (MBCNF/GOPA) composed of bacterial cellulose nanofibers (BCNFs), Fe₃O₄ nanoparticles, graphene oxide (GO) nano-sheets, and polyvinyl alcohol (PVA) was developed by combining a facile filler-loaded networks method with a vacuum freeze-drying process for the removal of malachite green (MG) dye from aqueous solution. The influence of various factors on adsorption, including initial dye concentration, adsorbent dosage, contact time, temperature, and pH of dye solution, was then investigated. The adsorbent preserved a high adsorption capacity over a wide range of pH conditions. Moreover, the adsorption isotherms data fitted well with the Langmuir isotherm model with a maximum adsorption capacity of 270.27 mg g^-1. Adsorption kinetics followed the pseudo-second-order model, and the thermodynamic parameters showed that the adsorption of MG dye was feasible and endothermic in nature and occurred spontaneously. Therefore, owing to its demonstrated properties such as 3D interconnected porous structure, lightweight, large specific surface area, superparamagnetic behavior at room temperature, excellent adsorbent efficiency (93% removal) and also its simple and eco-friendly synthesis process, MBCNF/GOPA could be considered a promising candidate for removing cationic dye pollutants from aqueous solution, which can easily be collected from aqueous solution by a small magnet. MBCNF/GOPA also showed favorable reusability for MG removal in wastewater treatment, and its application in different water samples for the removal of MG dye molecules from "real" samples was successfully performed.

Construction of a phosphate-rich polyacrylonitrile fiber surface microenvironment for efficient purification of crystal violet wastewater

Wastewater purification using fibrous adsorbents has received much attention due to their high efficiency, low cost, and recyclability. In this work, phosphate modified polyacrylonitrile fiber (B-PANEAPF) was prepared and used to remove cationic dyes. The B-PANEAPF showed the best adsorption capacity for crystal violet (CV) when compared with rhodamine B, methyl green, Victoria blue B, methylene blue, and neutral red. The adsorption tests revealed that the fiber possessed high adsorption efficiency and achieved semi-saturated adsorption within 15 min. The maximum adsorption capacity of 354.46 mg g-1 as calculated by the Langmuir adsorption model was higher than many other adsorbents. Furthermore, the B-PANEAPF was used to remove 210 mL of CV in a continuous-flow process with a high removal efficiency over 90%. Besides, the phosphate functionalized fiber could easily decrease the concentration of CV to below 0.5 mg L-1 which is below the maximum effluent discharge standard of 15 mg L-1 prescribed in China. It could also be fully recovered and easily separated from the solution to achieve re-use 10 cycles. Moreover, the adsorption mechanism indicated that the adsorption process of the fiber for CV was mainly attributed to electrostatic interaction and hydrogen bonding. In conclusion, the results suggested that the B-PANEAPF characterized by its simplicity, efficiency, eco-friendliness, and reusability, could be a promising candidate for CV removal.

Magnetically Navigated Core-Shell Polymer Capsules as Nanoreactors Loadable at the Oil/Water Interface

Polymer core-shell nanocapsules with magnetic nanoparticles embedded in their oil cores were fabricated and applied as nano(photo)reactors. Superparamagnetic iron oxide nanoparticles (SPIONs) coated with oleic acid were first synthesized and characterized structurally, and their magnetic properties were determined. The capsules with chitosan-based shells were then formed in a one-step process by sonication-assisted mixing of (1) an aqueous solution of the hydrophobically derived chitosan and (2) oleic acid containing the dispersed SPIONs. In this way, magnetic capsules with a diameter of approximately 500-600 nm containing encapsulated SPIONs with an average diameter of approximately 20-30 nm were formed as revealed by dynamic light scattering and scanning transmission electron microscopy measurements. The composition and magnetic properties of the formed capsules were also followed using dynamic light scattering, electron microscopies, and magnetic force microscopy. The water-dispersible capsules, thanks to their magnetic properties, were then navigated in a static magnetic field gradient and transferred between the water and oil phases, as evidenced by fluorescence microscopy. In this way, the capsules could be loaded in a controlled way with a hydrophobic reactant, perylene, which was later photooxidized upon transferring the capsules to the aqueous phase. The capsules were shown to serve as robust reloadable nanoreactors/nanocontainers that via magnetic navigation can be transferred between immiscible phases without disruption. These features make them promising reusable systems not only for loading and carrying lipophilic actives, conducting useful reactions in the confined environment of the capsules, but also for magnetically separating and guiding the encapsulated active molecules to the site of action.