Dye adsorption characteristics of magnetite nanoparticles coated with a biopolymer poly(γ-glutamic acid)

High-level production of poly-γ-glutamic acid by a newly isolated Bacillus sp. YJY-8 and potential use in increasing the production of tomato

Strain YJY-8, a new γ-polyglutamic acid producer, was separated from fermented soybean paste samples. The strain was identified as a genus of Bacillus by morphological and 16S rDNA sequence analysis and was named Bacillus sp. YJY-8. The optimal medium composition and cultural conditions were studied using a single-factor experiment and a response surface experiment. The optimized medium consisted of monosodium glutamate 70 g/L, glucose 54.3 g/L, glycerol 31.8 g/L, ammonium sulfate 11.1 g/L, yeast extract 3.2 g/L, tryptone 1.5 g/L, L-glutamic acid 6.8 g/L, MgSO4 7H2O 0.5 g/L, FeCl3 6H2O 0.02 g/L, KH2PO4 0.9 g/L, CaCl2 0.03 g/L, MnSO4 H2O 0.3 g/L, ammonium molybdate 0.02 g/L, pH 7.0. The optimal cultivation conditions were 35 °C and pH 7.0. Under the optimized conditions, after 48 hr of cultivation, the highest shaking flask fermentation level of γ-PGA reached 65.2 ± 0.36 g/L. In addition, through fed-batch fermentation in 30 L fermenters, the fermentation level of γ-PGA reached its highest level at 88.42 g/L and productivity was 1.23 g/(L hr) after 72 hr. Then, the effect of γ-PGA on tomato yield was investigated. At the seedling stage, the plant height and stem diameter of γ-PGA treated plants increased by 5.69 and 15.735% after spraying γ-PGA for 19 days. During the flowering and fruiting period, the stem diameter of the γ-PGA treatment group increased by 6.74%, with a maximum increase of 11.65%. The number of fruit branches increased by 0.56-16.29% and the number of fruit sets increased by 1.01-28.47%. At the fruit maturation stage, the yield of tomatoes increased by 10.51, 14.27, and 5.83%.

Heavy Metal Removal from Wastewater Using Poly(Gamma-Glutamic Acid)-Based Hydrogel

The removal of toxic heavy metal ions from wastewater is of great significance in the protection of the environment and human health. Poly(gamma-glutamic acid) (PGA) is a non-toxic, biodegradable, and highly water-soluble polymer possessing carboxyl and imino functional groups. Herein, water-insoluble PGA-based hydrogels were prepared, characterized, and investigated as heavy metal adsorbents. The prepared hydrogels were recyclable and exhibited good adsorption effects on heavy metal ions including Cu2+, Cr6+, and Zn2+. The effects of adsorption parameters including temperature, solution pH, initial concentration of metal ions, and contact time on the adsorption capacity of the hydrogel for Cu2+ were investigated. The adsorption was a spontaneous and exothermic process. The process followed the pseudo-first-order kinetic model and Langmuir isotherm model, implying a physical and monolayer adsorption. The adsorption mechanisms investigation exhibited that Cu2+ adsorbed on the hydrogel via electrostatic interactions with anionic carboxylate groups of PGA in addition to the coordination interactions with the -NH groups. Importantly, the PGA hydrogel exhibited good reusability and the adsorption capability for Cu2+ remained high after five consecutive cycles. The properties of PGA hydrogel make it a potential candidate material for heavy metal ion removal in wastewater treatment.

Enhanced photocatalytic degradation of polycyclic aromatic hydrocarbon by graphitic carbonitride-nickel (g-C3N4-Ni) nanocomposite

The objective of the present study is to synthesize g-C3N4-Ni nanocomposites composed of graphitic carbon nitride and magnetic nickel nanoparticles for benzopyrene degradation, which is one of the most potent polycyclic aromatic hydrocarbons (PAH) molecules. The concocted g-C3N4-Ni nanocomposites contained confined nanospheres with a mean particle dimension of 22 nm. Batch adsorption studies revealed that a rise in adsorbent dosage elevates benzopyrene degradation percentage in both water and soil samples with respect to time. The increase in the benzopyrene concentration did not have much influence on the degradation efficiency, and hence, the minimal concentration of PAH molecule is essential for the effective adsorption by g-C3N4-Ni nanocomposites. The rise in pH tends to increase the degradation of Benzopyrene till 3 h of the incubation period, and beyond 3 h, the degradation percentage declines. With regard to the effect of light source, UV light has been shown to accelerate the degradation of benzopyrene by g-C3N4-Ni nanocomposites than sunlight. The adsorption kinetic and isotherm investigations have proven that the Pseudo-second order kinetic model and Freundlich isotherm model were appropriate for our study. Thus, the g-C3N4-Ni nanocomposites were found to be efficient as a photocatalyst for the adsorption of benzopyrene from environmental samples.

Sustainable application of nanoparticles in wastewater treatment: Fate, current trend & paradigm shift

Existing water and wastewater treatment techniques are becoming increasingly difficult to employ due to the discovery of new toxins, the rapid development of population and industrial activities, and the limited quantity of water resources. Treatment of wastewater is a critical need in modern civilization due to a scarcity of water resources and rising industrial activity. Some of the techniques utilized include adsorption, flocculation, filtration, and others, although they are only used for primary wastewater treatment. However, the development and deployment of modern wastewater management with high efficiency and low capitalization are critical in terms of mitigating the environmental consequences of waste. The employment of different nanomaterials in the treatment of wastewater has opened up a world of possibilities for heavy metal and pesticide removal, as well as the treatment of microbes and organic contaminants in wastewater. Nanotechnology is a rapidly evolving technology because of certain nanoparticle's outstanding physiochemical and biological capabilities as contrasted to bulk counterparts. Secondly, it has been established that this is a cost-effective treatment strategy with significant potential in wastewater management, transcending the limitations imposed by currently existing technology. Advances in nanotechnology to reduce water contamination have been presented in this review, including the use of various nanomaterials such as nanocatalysts, nanoadsorbents, and nanomembranes in the treatment of wastewater containing organic contaminants, hazardous metals, and virulent pathogens.

Review on biopolymers and composites - Evolving material as adsorbents in removal of environmental pollutants

The presence of pollutants and toxic contaminants in water sources makes it unfit to run through. Though various conventional techniques are on deck, development of new technologies are vital for wastewater treatment and recycling. Polymers have been intensively utilized recently in many industries owing to their unique characteristics. Biopolymers resembles natural alternative to synthetic polymers that can be prepared by linking the monomeric units covalently. Despite the obvious advantages of biopolymers, few reviews have been conducted. This review focuses on biopolymers and composites as suitable adsorbent material for removing pollutants present in environment. The classification of biopolymers and their composites based on the sources, methods of preparation and their potential applications are discussed in detail. Biopolymers have the potentiality of substituting conventional adsorbents due to its unique characteristics. Biopolymer based membranes and effective methods of utilization of biopolymers as suitable adsorbent materials are also briefly elaborated. The mechanism of biopolymers and their membrane-based adsorption has been briefly reviewed. In addition, the methods of regeneration and reuse of used biopolymer based adsorbents are highlighted. The comprehensive content on fate of biopolymer after adsorption is given in brief. Finally, this review concludes the future investigations in recent trends in application of biopolymer in various fields in view of eco-friendly and economic perspectives.

Core-shell polygalacturonate magnetic iron oxide nanoparticles: Synthesis, characterization, and functionalities

This work aims to synthesize polygalacturonate-based magnetic iron oxide nanoparticles (INP-polyGalA). The synthesis consists of the diffusion of both Fe²⁺ and Fe³⁺ at a molar ratio of 1:2 through polyGalA solution followed by the addition of an alkaline solution. To form individual nanoparticle materials, the polyGalA concentration needs to be below its overlapping concentration (C*). The synthesized materials (INP-polyGalA) contain about 45 % of organic compound (polyGalA), and they have an average particle size ranging from 10 to 50 nm as estimated by several techniques (DLS, TEM and AFM) and their surfaces are negatively charged in pH range 2 to 7. The synthesized NPs showed magnetic characteristics, thanks to the formation of magnetite (Fe₃O₄) as confirmed by X-ray diffractions (XRD). Moreover, AFM combined with Infra-red mapping allowed us to conclude that polyGalA is located in the core of the nanoparticles but also on their surfaces. More specially, both carboxylate (COO^-) and carboxylic (COOH) groups of polyGalA are observed on the NPs surfaces. The presence of such functional groups allowed the synthesized material to (i) bind through the electrostatic interactions methylene blue (MB) which may have a great potential for r pollution control or (ii) to form hydrogel beads (ionotropic gelation) by using calcium as a crosslinking agent which can be used to encapsulate active molecules and target their release by using an external stimulus (magnetic field).

Effective Adsorption of Congo Red from Aqueous Solution Using Fe/Al Di-Metal Nanostructured Composite Synthesised from Fe(III) and Al(III) Recovered from Real Acid Mine Drainage

This study presents the first known exploration of Congo red dye (CR) adsorption by a polycationic Fe/Al Di-metal nanostructured composite (PDFe/Al) synthesised using Fe(III) and Al(III) recovered from authentic acid mine drainage (AMD). The PDFe/Al successfully removed CR from the aqueous solution. The mineralogical, microstructural, and chemical properties of the synthesised PDFe/Al adsorbent (before and after adsorption) were studied using state-of-the-art analytical instruments. The optimum conditions were observed to be 100 mg·L⁻¹ CR, 1 g of the PDFe/Al in 500 mL adsorbate solution, 20 min of shaking, pH = 3–8, and a temperature of 35 °C. At optimised conditions, the PDFe/Al showed ≥99% removal efficacy for CR dye and an exceptionally high Langmuir adsorption capacity of 411 mg·g⁻¹. Furthermore, a diffusion-limited adsorption mechanism was observed, with two distinct surfaces involved in the adsorption of CR from an aqueous solution. It was determined that the adsorption of CR induced internal strain and deformation within the matrices and interlayers of the PDFe/Al which resulted in a marked increase in the adsorbent pore surface area and pore volume. The remarkably high adsorption capacity could be attributed to the high surface area. A regeneration study showed that the adsorbent could be reused more than four times for the adsorption of CR. The findings from this study demonstrated the feasibility of recovering valuable minerals from toxic and hazardous AMD and demonstrated their potential for the treatment of industrial wastewaters.

Magnetic Poly(glycidyl methacrylate) Microspheres with Grafted Polypyrrole Chains for the High-Capacity Adsorption of Congo Red Dye from Aqueous Solutions

In this study, novel magnetic poly(glycidyl methacrylate) (PGMA) microspheres with grafted polypyrrole chains (magnetic PGMA-g-PPy) were developed for the high-capacity adsorption of Congo red (CR) from aqueous solutions. The magnetic PGMA-g-PPy was synthesized by the typical dispersion polymerization method and the ring-opening reaction of epoxy groups, producing abundant hydroxyls for the grafting polymerization of pyrrole in the presence of FeCl3 as an oxidizing agent on the surface of the microspheres. The characterization results showed that magnetic PGMA-g-PPy was successfully fabricated. The adsorption equilibrium data of the adsorbents could be well fitted by the Langmuir isotherm model, showing a high maximum adsorption capacity of 502.5 mg/g for CR. The adsorption followed pseudo-second-order kinetics with a fast speed. The adsorbents had no leaching of Fe in the solution at pH 1.0–11.0 for 24 h. The adsorption process was strongly pH-dependent and weakly ionic-strength-dependent. Furthermore, the magnetic microspheres could be easily regenerated, rapidly separated from the solution, and reused for wastewater treatment. The results suggest that magnetic PGMA-g-PPy microspheres are a promising efficient adsorbent for the removal of CR from wastewater.

Aptamer-functionalized metal-organic framework-coated nanofibers with multi-affinity sites for highly sensitive, selective recognition of ultra-trace microcystin-LR

A novel aptamer-functionalized metal-organic framework nanofibrous composite (viz. PAN/UiO@UiO2-N₃-aptamer) with a high aptamer coverage density was proposed based on the electrospinning and seeded growth method, and used for specific affinity recognition of trace Microcystin-LR (MC-LR). Heterobifunctional ligand was used to modify the metal-organic framework nanoparticles (MOF NPs) surface, which could passivate the MOF surface with respect to unmodified DNA, followed by coupling massive aptamers on MOF of the solid-phase microextraction (SPME) fiber using click chemistry. Characterizations including morphology, spectra analysis, mechanical stability, binding capacity and specificity were fulfilled. Applied to the analysis of MC-LR, the good selective and sensitive recognition were obtained with the detection limit as low as 0.003 ng/mL, which was better than most non-specific SPME or solid-phase extraction (SPE) protocols. The stability and reproducibility were acceptable, and the intra-day, inter-day and column-to-column relative standard deviations (RSDs) for the recovery of MC-LR were gained in the range from 2.5% to 14.3%, respectively. Satisfactory recoveries of MC-LR in environmental water samples were measured as 96.3 ± 4.7% - 98.9 ± 2.7% (n = 3) in tap water, 94.4 ± 2.5% - 96.1 ± 3.5% (n = 3) in pond water, and 97.0 ± 2.1% - 97.9 ± 3.1% (n = 3) in river water, respectively. This work demonstrated that the electrospun nanofibrous composite with massive aptamers would be a better alternative for ultra-trace MC-LR detection with good selectivity, matrix-resistance ability and high resolution.

Mechanistic evaluation of metformin drug confiscation from liquid phase on itaconic acid/kaolin hydrogel nanocomposite

Herein, kaolin (K) was amended by a novel gemini surfactant to attain nano-kaolin (nK), which was subsequently employed as a cross-linker in the preparation of itaconic acid/kaolin hydrogel nanocomposite (IA/nK) via free radical polymerization route employing the sonochemical technique, which has been used for the first time to extract metformin (MF) from water solution. The aspects which affect sorption behavior of IA/nK on metformin (MF) were systematically investigated via batch experiments, in harmony with effect of sorbent dosage, contact time, pH, MF concentration, equilibrium curves, kinetic behavior, and thermodynamic parameters. BET studies of IA/nK exhibited S_BET of 106.42 m²g^-1, pore volume 0.281 cm³ g^-1, and a pore radius of 16.627 Å. Kinetic and isotherm modelling portrayed that pseudo-second order and Freundlich model appropriated adsorption data with maximum sorption capacity of 278.35 mg g^-1. Thermodynamic parameters ΔH^O (13.67 kJmol^-1) and ΔG^O (-7.648 kJmol^-1) revealed that sequestration of MF on IA/nK was endothermic, spontaneous, and dominated by physisorption. Molecular docking study along with X-ray photoelectron spectroscopy inferred electrostatic interaction and hydrogen bonding as main mechanism of MF removal. IA/nK demonstrated dose-reliant inhibition of both gram-positive and gram-negative bacterial strains. IA/nK demonstrated good regeneration properties, up to four cycles without considerable decrease in its efficacy. The admirable sorption capacity coupled with good reusability, and low toxicity substantiates IA/nK as promising adsorbent for MF confiscation.

Development of efficient SALDI substrate based on Au-TiO2 nanohybrids for environmental and forensic detection of dyes and NSAIDs

Herein, a matrix-free approach is presented for comprehensive environmental and forensic analysis of dyes and nonsteroidal anti-inflammatory drugs (NSAIDs) using Au-TiO₂ nanohybrids coupled with surface-assisted pulsed laser desorption ionization-mass spectrometry (SALDI-MS). The Au-TiO₂ nanohybrids was prepared and characterized using inductively coupled plasma-optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), surface area measurements, ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). Initially, the optimal Au content was assessed using the survival yield (SY) method, confirming that 7.5% Au content on the TiO₂ surface offered the highest ionization efficiency. Subsequently, environmental analyses of dyes and NSAIDs in water samples were performed, and sensitive detection of all analytes was achieved with limits of detection (LODs) ranging from 10.0 ng mL^-1 to 10.0 fg mL^-1 and good spot-to-spot reproducibility. Additionally, the effect of potential contaminants commonly found in environmental samples, such as salts, surfactants and pesticides was also considered. Despite signal intensity reduction at high concentrations of some salts, the target analytes were detected, while the presence of surfactants and pesticides did not cause significant signal intensity reduction. Additionally, dyed and undyed Tetoron fibers and the effect of adhesive tape were evaluated. Direct analysis of the dyed Tetoron fibers on the target plate, using the nanohybrids, enabled higher detection sensitivity of the dyes, in addition to adducts of polystyrene and cellulose, the main components of the fiber. Finally, NSAIDs in oral fluid were analyzed and sensitive detection of the analytes was observed using the nanohybrids with LODs and LOQs in the range of 0.1-10 ng mL^-1 and 1-20 ng mL^-1, respectively. The trueness of the exact mass was in the range of 0.64-6.2 ppm while the recovery of the spiked samples was in the range of 82.90-107.54%% indicating the efficiency of the Au-TiO₂ nanohybrids as SALDI substrate. Thus, the Au-TiO₂ nanohybrids hold considerable promise in terms of sensitivity, reproducibility, and LOD, and may significantly contribute to environmental and forensic identification.

Removal of polycyclic aromatic hydrocarbons from water by magnetic activated carbon nanocomposite from green tea waste

This study aims to synthesize a magnetic activated carbon nanocomposite from green tea leaf waste (MNPs-GTAC) for evaluation of adsorption efficiency of 4 priority polycyclic aromatic hydrocarbons (PAHs). MNPs-GTAC contained spherically-shaped MNPs with cubic spinel structure, surface area at 118.8 m²/g, particle size at 8.6 nm and saturation magnetization at 34.2 emu/g. PAH adsorption reached a plateau at an MNPs-GTAC dose of 50 or 60 mg/L, pH of 2-4 and ionic strength of 0.1-10%, with PAH reduction in the presence of humic acid being compensated by addition of 0.1% sodium chloride. Kinetics was rapid attaining 80% removal within 5 min and the pseudo-second-order rate decreased in this order: Benzo[a]anthracene>Chrysene>Benzo[b]fluoranthene>Benzo[a]pyrene. Isotherm modeling revealed a Langmuir type-2 shape with the maximum adsorption capacity being 28.08, 22.75, 19.14 and 15.86 mg/g for Benzo[b]fluoranthene, Benzo[a]pyrene, Chrysene and Benzo[a]anthracene, respectively. Temperature study showed the PAH adsorption to be an endothermic and spontaneous process with increased randomness at solid-solution interface. Acetonitrile could completely recover the adsorbed PAH and MNPs-GTAC was successfully recycled 5 times with a minimum loss. Application to mineral water showed 86-98% and 72-89% removal for PAHs spiked respectively at 0.1 and 1 mg/L, while a complete removal was attained in tap and river waters.

Barium/Cobalt@Polyethylene Glycol Nanocomposites for Dye Removal from Aqueous Solutions

Dyes are known as one of the most dangerous industrial pollutants which can cause skin diseases, allergy, and provoke cancer and mutation in humans. Therefore, one of the important environmental issues is the effective removal of dyes from industrial wastewater. In the current work, BaFe₁₂O₁₉/CoFe₂O₄@polyethylene glycol (abbreviated as BFO/CFO@PEG) nanocomposite was synthesized and evaluated regarding its capacity for adsorptive removal of a model dye Acid Blue 92 (denoted as AB92) from aqueous solutions. The characteristics of the prepared nanocomposite was determined by tests such as X-ray diffraction (XRD), scanning electron microscope (SEM), vibration sample magnetization (VSM), and Fourier transform infrared spectroscopy (FTIR). The effects of conditional parameters including pH (2–12), initial concentration of dye (20–100 mg/L), adsorbent dosage (0.02–0.1 g/L) and contact time (0-180 min) on the adsorption of dye were investigated and then optimized. The results indicated that with the increase of the adsorbent dosage from 0.02 to 0.1 g/L, the removal efficiency increased from 74.1% to 78.6%, and the adsorbed amount decreased from 148.25 to 31.44 mg/g. The maximum removal efficiency (77.54%) and adsorption capacity (31.02 mg/g) were observed at pH 2. Therefore, the general optimization conditions revealed that the maximum adsorption efficiency of dye was obtained in condition of initial concentration of 20 mg/L, contact time of 1 h and pH of solution equal 2. The adsorption isotherm and kinetic data were evaluated using a series of models. The pseudo-second order kinetic model and Freundlich isotherm model show the best fitting with experimental data with R²∼0.999.

Improving enzyme activity, thermostability and storage stability of β-1,3-1,4-glucanase with poly-γ-glutamic acid produced by Bacillus sp. SJ-10

β-1,3-1,4-glucanase (BG) is an industrially important enzyme owing to its stringent specificity for β-glucan cleavage. In this study, poly-γ-glutamic acid (γ-PGA) was added to BG to investigate its effect on improving the activity and stability of the enzyme. The effect of γ-PGA was investigated by analyzing kinetic and thermodynamic parameters. Compared to control, significant differences (P < .05) in enzyme activity were observed when 1.0 %, 1.5 %, and 2.0 % γ-PGA was added, and the activities were increased 1.23 ± 0.05, 1.23 ± 0.07, and 1.31 ± 0.07-fold, respectively. Regarding thermostability, residual BG activity after a 1 h incubation at 60 °C was 12.53 ± 0.06 % without γ-PGA and 79.02 ± 5.76 % with 1% γ-PGA. The storage stability at 25 °C and 50 °C also increased when γ-PGA was present. The kinetics and thermodynamic investigations indicated that the increased activity and stability of BG when γ-PGA was added were due to increased values of the V_max, K_cat, and activation energy for denaturation. The findings of this study suggest that adding γ-PGA to BG increases the application value of this enzyme in the food and feed industries.

High-level production of poly-γ-glutamic acid from untreated molasses by Bacillus siamensis IR10

Background

Poly-γ-glutamic acid (γ-PGA) is a promising biopolymer and has been applied in many fields. Bacillus siamensis SB1001 was a newly isolated poly-γ-glutamic acid producer with sucrose as its optimal carbon source. To improve the utilization of carbon source, and then molasses can be effectively used for γ-PGA production, ⁶⁰cobalt gamma rays was used to mutate the genes of B. siamensis SB1001.

Results

Bacillus siamensis IR10 was screened for the production of γ-PGA from untreated molasses. In batch fermentation, 17.86 ± 0.97 g/L γ-PGA was obtained after 15 h, which is 52.51% higher than that of its parent strain. Fed-batch fermentation was performed to further improve the yield of γ-PGA with untreated molasses, yielding 41.40 ± 2.01 g/L of γ-PGA with a productivity of 1.73 ± 0.08 g/L/h. An average γ-PGA productivity of 1.85 g/L/h was achieved in the repeated fed-batch fermentation. This is the first report of such a high γ-PGA productivity. The analysis of the enzyme activities showed that they were affected by the carbon sources, enhanced ICDH and GDH, and decreased ODHC, which are important for γ-PGA production.

Conclusion

These results suggest that untreated molasses can be used for economical and industrial-scale production of γ-PGA by B. siamensis IR10.

Sonochemical versus reverse-precipitation synthesis of CuxO/Fe2O3/MoC nano-hybrid: removal of reactive dyes and evaluation of smartphone for colorimetric detection of organic dyes in water media

In the present work, an ultrasound-assisted reverse-precipitation method was applied as a new approach for the synthesis of Cu_xO/Fe₂O₃/MoC. In the sonication method, a bath type sonicator as a simple, cost-effective, and low intensity sonicator was used. To determine the influence of ultrasonic waves on the morphology and application of nano-hybrid as nano-sorbent, it was also synthesized using the reverse precipitation method. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), Zeta-potential measurement, and vibrating sample magnetometer (VSM) techniques. The XRD analysis confirmed that the sono-synthesized sample has higher crystallinity than the conventional one and CuO/Cu₂O/MoC/Fe₂O₃ phase was obtained under ultrasound. According to the TEM and FESEM, sono-synthesized nanoparticles were rod-like with a width and length of 3 nm and 40 nm, respectively. Also, a well-dispersed shape and uniform morphology of nanoparticles were obtained using sonication. In comparison with the conventional nano-hybrid, this structure results in more void and accessible sites for adsorption of pollutants. The efficiency of resulting nanoparticles in adsorption of reactive dyes as a model of the pollutant was evaluated by sorption and sono-sorption processes. The sono-synthesized sample removed the pollutants more efficient than the conventional sample. The removal efficiencies were about 99% for the removal of reactive dyes using the sono-synthesized sample and sono-sorption method. Besides, determining factors including pH, pollutant concentration, temperature, and contact time were optimized in the sono-sorption and sorption processes. A colorimetric method based on RGB value was used to determine dye concentration in aqueous media. The images were taken by a smartphone and analyzed by ImageJ software. The accuracy of RGB results was confirmed by a UV-Vis spectrophotometer. Graphical abstract The figures on the left side show the FESEM images of nano-sorbent synthesized in the presence of ultrasonic irradiation (US method) and the absence of it (MS method). A well-dispersed shape and uniform morphology of nanoparticles were obtained using sonication. The scheme on the right side illustrates the process of sono-sorption for the removal of dyes and determination of their concentration using the colorimetric method. A colorimetric method based on RGB value was used to determine dye concentration in aqueous media. The graph shows the removal efficiencies of RY84 onto nanosorbent. The removal efficiencies were about 99% for the removal of reactive dye using the sono-synthesized sample and sono-sorption method.

Data on the removal of Optilan Blue dye from aqueous media using starch-coated green synthesized magnetite nanoparticles

In this data article, we present supplementary data related to the research article entitled "Starch-coated green synthesized magnetite nanoparticles for removal of textile dye Optilan Blue from aqueous media" Stan et al., 2019. Data interpretations are included in the related research article Stan et al., 2019. The synthesized starch-coated Fe3O4 nanoparticles (ST-coated Fe3O4 NPs) were analyzed by scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) to illustrate the shape and surface coating of nanoparticles. Moreover, the Brunauer-Emmett-Teller (BET) technique was used to evidence starch deposition on magnetite nanoparticles. The obtained nanocomposites were used for adsorption of Optilan Blue (OB) in batch conditions and the optimum agitation speed and point of zero charge (pHpzc) were established. After OB adsorption on ST-coated Fe3O4 NPs, the nanocomposites were analyzed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The stability of starch coated Fe3O4 NPs in the acidic as well as alkaline pH was also evidenced by FTIR spectroscopy. In addition, to test the stability of ST-coated Fe3O4 NPs, leaching experiments were carried out. The experimental data were compared with isotherm and kinetic models in order to determine the most suitable for fitting.

Application of EDTA modified Fe3O4/sawdust carbon nanocomposites to ameliorate methylene blue and brilliant green dye laden water

This work explored the potential of magnetic sawdust carbon nanocomposites for cationic dyes removal from aqueous medium. EDTA modified magnetic sawdust carbon nanocomposites (EDTA@Fe₃O₄/SC ncs) were prepared by biogenic green reduction and precipitation approach. The surface properties, structure and composition of nanocomposites were characterized by HRTEM, FESEM, XRD, EDX, BET, FTIR etc. The Fe₃O₄ nanoparticles were 10-20 nm in diameters and having 14 m²/g surface area. Removal of Methylene blue (MB) and Brilliant green (BG) dyes from aqueous medium was studied in batch mode experiments. The maximum removal was achieved at neutral pH 7.0 with in 30 min. Adsorption capacity of EDTA@Fe₃O₄/SC for MB and BG dyes was 227.3 mg/g and 285.7 mg/g, respectively. Dye adsorption behaviour is well explained by Freundlich model. The rate of cationic dye adsorption is explained by pseudo-second order model. The value of thermodynamic parameters confirmed that adsorption process was spontaneous and favourable. Desorption and reusable efficiency of nanocomposites was also evaluated.

Preparation, performances and mechanisms of magnetic Saccharomyces cerevisiae bionanocomposites for atrazine removal

Saccharomyces cerevisiae and nanoparticles of iron oxide (Fe₃O₄) which were linked with chitosan (CS) through epichlorohydrin (ECH) were encapsulated in calcium alginate to prepare a novel type of bionanocomposites. Characterization results showed that the Fe₃O₄-ECH-CS nanoparticles were quasi-spherical with an average diameter of 30 nm to which chitosan was successfully attached through epichlorohydrin. The saturation magnetization value of the nanoparticles was 21.88 emu/g, and ferrous and ferric irons were simultaneously observed in the magnetic nanoparticles. Data of atrazine removal by yeasts showed that both inactivated and live yeasts could decrease the concentration of atrazine effectively. The inactivated yeasts achieved 20% removal rate, which indicated that adsorption by the yeasts also played a role in the removal. Removal efficiency of atrazine was maximized at 88% under 25 °C, pH of 7 and an initial atrazine concentration of 2 mg/L. When the magnetic bionanocomposite was recycled and reused twice, only 12% and 20% drop in removal efficiency was observed at the first time and the second time severally. So, atrazine could be used by the yeasts as the sole carbon source for growth and multiplication, and both adsorption and biodegradation by the bionanocomposite contributed to atrazine removal.

Simultaneous removal of cationic methylene blue and anionic reactive red 198 dyes using magnetic activated carbon nanoparticles: equilibrium, and kinetics analysis

For the simultaneous adsorption of cationic dye (methylene blue, MB) and anionic dye (reactive red 198, RR198) from aqueous solution, magnetic activated carbon (MAC) nanocomposite as a promising adsorbent was prepared and used. The concentration of MB at different time intervals was determined using a UV-Vis spectrophotometer while the concentration of RR198 was determined using a high performance liquid chromatography (HPLC) system. The effect of solution pH, contact time, adsorbent amount, and dye concentration were investigated. Also, both kinetic and isotherm experiments were studied. The optimum pH was 10 and 5.5 for adsorption of MB and RR198, respectively, and the equilibrium status was achieved after 120 min. The adsorption kinetics was controlled by the pseudo-second order kinetic model more than pseudo-first order. The best-fitted isotherms were Freundlich and Langmuir models for MB and RR198, respectively. The higher values of Freundlich adsorption capacity (K_f) for MB in comparison with RR198 refer to MAC affinity to remove cationic dyes more than anionic dyes. Apparently, there was no substantial change in the adsorption efficiency among the 10 adsorption-desorption cycles. Overall, MAC can be considered as an effective and efficient viable adsorbent for cationic and anionic dyes removal from industrial wastewaters.

A pure magnetite hydrogel: synthesis, properties and possible applications

A magnetite-only hydrogel was prepared for the first time by weak base mediated gelation of stable magnetite hydrosols at room temperature. The hydrogel consists of 10 nm magnetite nanoparticles linked by interparticle Fe-O-Fe bonds and has the appearance of a dark-brown viscous thixotropic material. The water content in the hydrogel could be up to 93.6% by mass while volume fraction reaches 99%. The material shows excellent biocompatibility and minor cytotoxic effects at concentrations up to 207 μg mL^-1. The gel shows excellent sorption capacity for heavy metal adsorption such as chrome and lead ions, which is 225% more than the adsorption capacity of magnetite nanoparticles. Due to thixotropic nature, the gel demonstrates mechanical stimuli-responsive release behavior with up to 98% release triggered by ultrasound irradiation. The material shows superparamagnetic behavior with a coercivity of 65 emu g^-1 at 6000 Oe. The magnetite gels prepared could be used for the production of magnetite aerogels, magnetic drug delivery systems with controlled release and highly efficient sorbents for hydrometallurgy.

Preparation of microscale zero-valent iron-fly ash-bentonite composite and evaluation of its adsorption performance of crystal violet and methylene blue dyes

New microscale zero-valent iron adsorbent on fly ash and bentonite matrix for removal of crystal violet (CV) and methylene blue (MB) was synthesized through direct reduction of iron oxide using coke and palm kernel shell. The adsorbent was prepared as cylindrical shaped pellets to remove the CV and MB from the aqueous solution. Nitrogen adsorption-desorption isotherm and scanning electron microscopy (SEM) studies showed that the adsorbent is highly porous, and the iron particles are finely dispersed on the supporting material surfaces. FTIR and UV studies indicated that the C=C bonds in CV and C=N⁺(CH₃)₂ bonds in MB were affected in the adsorption process. MB switched to the reduced MBH₂ species while CV was reduced to two small-size molecular compounds, explaining the higher CV adsorption in comparison to that of MB. The reduction of these compounds was coupled to the oxidation of Fe⁰ to Fe₂O₃ as revealed by XRD characterization of the adsorbent after adsorption. CV and MB adsorption isotherms fitted well with the Langmuir adsorption model. Different adsorption and reduction kinetic models were examined for the MB and CV removal processes. A better fit of the experimental data with the pseudo-second-order model was observed. CV and MB adsorption increased with temperature in the 30-50 °C range. At 50 °C, adsorption capacities of CV and MB reached to 89.9 and 42.8 mg/g, respectively. This new adsorbent showed a superior adsorption capacity for CV and MB when compared to other adsorbents.

Microwave assisted green synthesis of silver nanoparticles using leaf extract of elephantopus scaber and its environmental and biological applications

The fabrication of spherical silver nanoparticles using the phytoreducing agent Elephantopus scaber is reported here. Irradiation of the reaction mixture under a domestic microwave oven enabled the formation of stable silver nanoparticles and was confirmed by UV-vis spectral portrait. Chemical components inherent in the aqueous leaf extract which reduces the monovalent silver were identified by FT-IR spectroscopy. The crystal structure of the synthesized nanoparticles was established as face centred cube by the powder XRD analysis. The TEM images suggest an average particle size of 37.86 nm to the silver nanoparticles. The prepared silver nanocatalysts can successfully reduce various organic nitro compounds, namely, 4-nitrophenol, 2-nitroaniline and 4-nitroaniline. The environmental pollution caused by dyes like eosin Y is effectively wiped off within a short span of time using the prepared nanocatalysts. The free radical quenching efficacy of the plant extract and the silver nanoparticles were checked by employing DPPH assay bestowing ascorbic acid reference. The potential of the nanoparticles as antimicrobials against six human disease causing pathogens were tested through the well diffusion pathway. The newly developed silver nanoparticles produced IC₅₀ value 15.68 ± 0.15 μg/mL on human skin carcinoma cells, A375 and 65.49 ± 0.40 μg/mL on fibroblast cells, L929 when the cytotoxicity is studied employing MTT assay. Elephantopus scaber showed IC₅₀ value 50.55 ± 0.17 μg/mL against A375 cells.

Graphene oxide coated with porous iron oxide ribbons for 2, 4-Dichlorophenoxyacetic acid (2,4-D) removal

Graphene oxide (GO) was prepared from commercially available graphite powder. Porous iron oxide ribbons were grown on the surface of GO by solvothermal process. The prepared GO-Fe₃O₄ nanocomposites are characterized by FT-IR, XRD, VSM, SEM, TEM, Raman spectroscopy, surface functionality and zero point charge studies. The morphology of the iron oxide ribbons grown on GO is demonstrated with TEM at various magnifications. The presence of magnetite nanoparticles is evident from XRD peaks and the magnetization value is found to be 37.28emu/g. The ratio of intensity of D-peak to G-peak from Raman spectrum is 0.995. The synthesized Graphene oxide-Fe₃O₄ nanocomposites (GO-Fe₃O₄) were explored for its surface adsorptive properties by using a model organic compound, 2,4-Dichlorophenoxy acetic acid (2,4-D) from aqueous solution. Batch adsorption studies were performed and the equilibrium data are modelled with Langmuir, Freundlich and Temkin isotherms. The maximum monolayer capacity from Langmuir isotherm is 67.26mg/g. Kinetic studies were also carried out and the studied adsorption process followed pseudo second-order rate equation. Mechanism of the adsorption process is studied by fitting the data with intraparticle diffusion model and Boyd plot. The studied adsorption process is both by film diffusion and intraparticle diffusion.

Competitive removal of hazardous dyes from aqueous solution by MIL-68(Al): Derivative spectrophotometric method and response surface methodology approach

MIL-68(Al) as a metal-organic framework (MOF) was synthesized and characterized by different techniques such as SEM, BET, FTIR, and XRD analysis. This material was then applied for simulations removal of malachite green (MG) and methylene blue (MB) dyes from aqueous solutions using second order derivative spectrophotometric method (SODS) which was applied to resolve the overlap between the spectra of these dyes. The dependency of dyes removal efficiency in binary solutions was examined and optimized toward various parameters including initial dye concentration, pH of the solution, adsorbent dosage and ultrasonic contact time using central composite design (CCD) under response surface methodology (RSM) approach. The optimized experimental conditions were set as pH7.78, contact time 5min, initial MB concentration 22mgL(-1), initial MG concentration 12mgL(-1) and adsorbent dosage 0.0055g. The equilibrium data was fitted to isotherm models such as Langmuir, Freundlich and Tempkin and the results revealed the suitability of the Langmuir model. The maximum adsorption capacity of 666.67 and 153.85mgg(-1) was obtained for MB and MG removal respectively. Kinetics data fitting to pseudo-first order, pseudo-second order and Elovich models confirmed the applicability of pseudo-second order kinetic model for description of the mechanism and adsorption rate. Dye-loaded MIL-68(Al) can be easily regenerated using methanol and applied for three frequent sorption/desorption cycles with high performance. The impact of ionic strength on removal percentage of both dyes in binary mixture was studied by using NaCl and KCl soluble salts at different concentrations. According to our findings, only small dosage of the proposed MOF is considerably capable to remove large amounts of dyes at room temperature and in very short time that is a big advantage of MIL-68(Al) as a promising adsorbent for adsorptive removal processes.

Removal of cationic and anionic dyes from aqueous solution with magnetite/pectin and magnetite/silica/pectin hybrid nanocomposites: kinetic, isotherm and mechanism analysis

Novel adsorbents, magnetite nanoparticles modified with pectin shell and silica/pectin double shell, were fabricated and tested for single dye and dye mixture adsorption from water samples.

Removal of dyes from aqueous solutions using activated carbon prepared from rice husk residue

The treatment of dye wastewater by activated carbon (AC) prepared from rice husk residue wastes was studied. Batch adsorption studies were conducted to investigate the effects of contact time, initial concentration (50-450 mg/L), pH (3-11) and temperature (30-70 °C) on the removal of methylene blue (MB), neutral red, and methyl orange. Kinetic investigation revealed that the adsorption of dyes followed pseudo-second-order kinetics. The results suggested that AC was effective to remove dyes, especially MB, from aqueous solutions. Desorption studies found that chemisorption by the adsorbent might be the major mode of dye removal. Fourier transform infrared results suggested that dye molecules were likely to combine with the O-H and P=OOH groups of AC.

Poly(4-styrenesulfonic acid-co-maleic acid)-sodium-modified magnetic reduced graphene oxide for enhanced adsorption performance toward cationic dyes

PSSMA-modified magnetic reduced graphene oxide nanocomposites (PSSMA/M-rGO) were prepared and used for enhanced adsorption of cationic dyes.

Synthesis and characterization of poly(γ-glutamic acid)-based alumina nanoparticles with their protein adsorption efficiency and cytotoxicity towards human prostate cancer cells

Protein adsorption and cytotoxicity of poly(γ-glutamic acid) functionalized nanoalumina.

Supported and unsupported nanomaterials for water and soil remediation: are they a useful solution for worldwide pollution?

Remediation technologies for wastes generated by industrial processes include coagulation, reverse osmosis, electrochemistry, photoelectrochemistry, advanced oxidation processes, and biological methods, among others. Adsorption onto activated carbon, sewage sludge, zeolites, chitosan, silica, and agricultural wastes has shown potential for pollutants' removal from aqueous media. Recently, nanoscale systems [nanoparticles (NPs) supported on different inorganic adsorbents] have shown additional benefits for the removal/degradation of several contaminants. According to the literature, NPs enhance the adsorption capacity of adsorbent materials and facilitate degradation of pollutants through redox reactions. In this review we analyzed relevant literature from 2011 to 2013, dealing with water and soil remediation by nanomaterials (NMs), either unsupported or supported upon inorganic adsorbents. Despite the outstanding reported results for some NMs, the analysis of the literature makes clear the necessity of more studies. There is lack of information about NMs regeneration and reusability, their large-scale application, and their efficiency in actual industrial wastewaters and contaminated soils. Additionally, little is known about NMs' life cycle, release of metal ions, disposal of pollutant loaded NMs, and their impacts on different ecosystems.