Dye Concentration Research Articles

Ultrafiltration membrane based on chitosan/adipic acid: Synthesis, characterization and performance on separation of methylene blue and reactive yellow-145 from aqueous phase

Here, we report for the first time using of the nontoxic chitosan/adipic acid cross-linked membrane CS/AA in the separation of methylene blue and reactive yellow-145 from aqueous phase. The reason we chose adipic acid as a cross-linking agent is because it gives the cross-linked membrane moderate flexibility due to the presence of four methylene groups in its structure. The structure of the cross-linked membrane CS/AA and their properties were confirmed through, FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), atomic force microscopy (AFM), and BET analysis. The thermal properties of membrane indicated an improvement in its flexibility and hydrophobicity, but this improvement was accompanied by a decrease in its thermal stability. pHpzc value and porosity of the CS/AA were 7.88, and 73.95 % respectively. The average pore radius distribution ranged from 2 to 27 nm. The prepared cross-linked membrane provides spontaneous and continuous purification of water with a high efficiency. This is due to the membrane CS/AA ability to separate methylene blue and reactive yellow-145 from the aqueous phase almost completely. The results revealed that the removal efficiency and permeation flux for MB were 100 % and 1 L/m2.h respectively at initial dye concentration of (4,8) mg/L, at 1 bar, and the removal efficiency and permeation flux for RY-145 were (94,96) % and (1.06, 2.09) L/m2.h respectively at 100 mg/L and at (1,1.5) bar. Such cross-linked nanopore polymer membranes provide a new approach for emerging novel purification systems, principally in the field of environmental field.

Magnetic zinc oxide/silica microbeads for the photocatalytic degradation of azo dyes

Photocatalysis is a promising technique for the complete degradation of azo dyes that are present in wastewater. In this work, a new photocatalyst in the form of ZnO/Fe3O4/SiO2 hybrid microbeads was fabricated for the photocatalytic degradation of methylene blue. The microbeads were synthesised through self-assembly and subsequent agglomeration of nanoparticles within an aqueous phase of a water-in-oil emulsion template. Photocatalytic degradation experiments were conducted through exposure of a methylene blue solution to UV light. The hybrid microbeads performed better than ZnO powder at the same initial dye and ZnO concentration because of higher adsorption and degradation. The initial concentration of dye solution and catalyst dosage have a significant impact on the degradation. Higher degradation is seen with lower initial dye concentration and higher catalyst dosage. The presence of magnetic nanoparticles within the beads allows for their full recovery and reuse for degradation experiments. Complete degradation of dye was achieved using the new ZnO/Fe3O4/SiO2 microbeads.

Exploring the structural characteristics and dye removal capabilities of powder-, granule- and film- shaped magnetic activated carbon derived from Oleaster seed.

Dye pollution in water caused by excessive discharge of industrial effluent has become a major environmental problem in recent decades because of its irreversible effects on human health. In this study, low-cost carbon-based adsorbents synthesized from Oleaster seed (OS) were prepared in three forms of powder (PAC), film (FAC), and granule (GAC) and used for the removal of methylene blue dye. The properties of the synthesized adsorbents were characterized by SEM-EDX, BET, XPS and FTIR analyses. The maximum adsorption capacity (qmax) of PAC, FAC, and GAC adsorbents were obtained as 68.49, 32.25, and 15.10 mg/g, respectively at the optimum experimental conditions of pH = 10, adsorbent dosages of 0.5, 1, and 2 g/l, contact times of 60, 90, and 120 min, dye concentration of 10 mg/L, and temperature of 25°C. The Langmuir isotherm well described the equilibrium data for all three adsorbents. The pseudo-second-order kinetic model provided the best fit with the adsorption data obtained from all three adsorbents. Adsorption occurred spontaneously through a combination of chemical and physical mechanisms, with a thermodynamically exothermic process. The desorption experiments demonstrated that all the adsorbents have substantial potential for recovery. The novel activated carbon/alginate composite films are proposed as more promising biosorbents to remove MB dye from the aquatic environment compared to GAC adsorbents.

Crystallization-driven tuneable lasing of perylene doped into the nematic liquid crystal

Versatile devices with tunable capabilities for controlling lasing wavelength and intensity are in high demand. Liquid crystals (LCs) exhibit immense potential for such applications, offering fine-tuning possibilities through external factors. On the other hand, laser technology is currently a research hotspot in optoelectronics, and also in practical applications. The recent market introduction of laser television marks a significant stride toward making such advanced technology accessible in every household. In synergy with laser pumping, the LCs unquestionably can be rediscovered. This study presents a comprehensive investigation into the crystallization phenomenon within a host-guest device, compact in size, free from moving parts, and integrating the liquid crystalline (LC) matrix doped with 3,4,9,10-tetra-(3-alcoxy-carbonyl)-perylene (THCP) dye. The focus lies in examining the influence of varying dye concentrations on multicolor fluorescence, lasing behavior, and device morphology. The systematic analysis of Random Lasing (RL) energy thresholds and the impact of DC voltage on light intensity modulation is demonstrated. Morphological changes were monitored in real-time using optical microscopy techniques, including crossed polarizer, and fluorescence imaging under 450 nm excitation. Utilizing advanced Transmission Electron Microscopy (TEM) techniques, we explore exceptional insights into our set of devices, providing novel information about the THCP crystallization process for the first time in the literature. To gain a comprehensive understanding of the crystal forming and molecular geometry we examined additionally the THCP dye, using X-ray diffraction and Raman spectroscopy. Furthermore, we showcase that varying the pumping energy enables multicolor tuning in the fabricated systems, presenting an attractive feature in the context of laser display technologies.

Solvent Effects on the Absorption and Emission Spectra of the [5-amino-1-bromoindolizin-3-yl](4-bromophenyl)methanone Molecule.

The effects of solvent on the absorption and emission spectra and dipole moments of the 5ABBM have been extensively studied in a series of solvents. The dipole moments in the excited state are observed to be greater than those in the ground-state in all the solvents studied for the chosen molecule. The dipole moment increase in the excited singlet state ranges from 2.42 to 24.14 D. The experimentally calculated ground state and excited state dipole moments were determined using the solvatochromatic shifts in the absorption and emission spectra as a function of dielectric constant (ɛ) and refractive index (n). These data are used to estimate the excited-state dipole moment using the experimentally determined ground-state dipole moment. A series of fifteen different organic solvents (toluene, methanol, n-butyl alcohol, ethyl acetate, DMS, acetonitrile, benzene, isopropyl alcohol, water, DMF, DCM, DIO, THF, ethanol, and octanol) were investigated at constant dye concentrations. Small changes in the fluorescence spectrum were observed for the different solvents; the highest fluorescence intensity was observed for DMS, and the lowest was observed for water. The Stokes shift in different solvents was studied for the 5ABBM molecule. This results in molecule being more polar in the excited state than in the ground state for the solvents used. The ground state dipole moments, HOMO-LUMO, and molecular electrostatic potential maps were also computed via ab initio calculations and evaluated via Gaussian 09W software.

Semiconductor Catalyst: Investigation for the Degradation of BB9 Azo Dye by Sonophotocatalytic Process

AbstractThe degradability of an azo dye, Basic Blue 9 (BB9), by heterogeneous sonocatalytic, photocatalytic, and sonophotocatalytic oxidation process was examined using simultaneous irradiation of UV‐C at 254 nm and power ultrasound at 20 kHz accompanied with a heterogeneous catalyst zinc oxide (ZnO) in the study. The effect of ZnO dose and initial dye concentration was investigated on the dye degradation in sonocatalytic, photocatalytic, and sonophotocatalytic processes at pH 5.5 (natural pH). The results obtained from the experimental studies were evaluated with the parameters of color removal, pseudo‐first‐order rate constant, and half‐life time. It was observed that the degradation of BB9 dye by the sonophotocatalytic process was higher compared to both sonocatalytic and photocatalytic degradation. as follows: 97.46, 48.64 and 56.88 %. The combination of sono and photocatalytic showed a remarkable synergistic effect in BB9 degradation. The kinetics of sonophotocatalytic oxidations, depending on the initial BB9 dye concentration, were found to follow the Langmuir‐Hinshelwood model. In addition, the effect of ZnO on the sonophotocatalytic oxidation process was higher compared to titanium dioxide and zero‐valent iron as follows: 97.47, 80.77 and 80.62 %.

Furfuryl-pyridinium-functionalization of flaxseed gum for effective methylene blue removal from aqueous solution

This study describes the modification of flaxseed gum (FSG) via furfural to obtain a furfuryl-pyridinium modified adsorbent (Flax-Py) with improved adsorption characteristics towards methylene blue (MB) versus results obtained for unmodified FSG. Materials characterization was achieved via complementary spectral methods (NMR, XPS, FT-IR, Raman, and XRD) as well as thermogravimetric analysis (TGA) and ζ-potential measurements. Synthetic modification of FSG to yield Flax-Py that led to enriched N-content (2.75 atom-% versus 0.76 atom-% for FSG), and the conversion of furfuryl to pyridinium was incomplete (ca. 50 %), where both moieties were identified. The adsorption isotherms at pH 7 showed that FSG possessed favorably high MB adsorption capacity (ca. 540 mg/g); while Flax-Py was notably lower (167 mg/g). Flax-Py facilitated 100% MB removal at low dye concentrations (1-10 mg/L) versus 50 % MB removal for the FSG bioadsorbent. Further, Flax-Py showed moderate loss of adsorption with MB (ca. 12-16% dye removal) after five regeneration cycles. Flax-Py revealed improved settling characteristics (time, density, gelation, and solubility) that facilitate enhanced phase separation of FSG fractions by circumventing the need for centrifugation. The adsorption mechanism was attributed primarily to H-bonding effects with secondary contributions due to electrostatic interactions (negative ζ-potential above pH 4.2). This study successfully modified FSG to obtain an improved adsorbent (Flax-Py) attaining nearly quantitative MB dye removal at environmentally relevant concentrations (< 15 mg/L).

Activity, stability, and kinetic study of CuO/TiO2 Janus photocatalyst for rhodamine B degradation

ABSTRACT The CuO/TiO2 photocatalyst was synthesized using hydrothermal and sonochemical methods and subsequently applied to degrade rhodamine B in wastewater. The best synthesis conditions were established, determining Cu(NO3)2 solution concentration of 2.5 wt.% and calcination temperature of 500 °C. The CuO/TiO2 photocatalyst underwent characterization through various techniques, including inductively coupled plasma spectroscopy (ICP), photoluminescence, X-ray diffraction, ASAP, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy. TEM and SEM analyses revealed the presence of TiO2 nanowires and CuO nanoparticles. The Box–Behnken design, encompassing 27 experimental runs, assessed the impact of process variables such as initial dye concentration, pH, UV lamp power, and catalyst dose on the degradation process. The model's R2 value of 0.9893 indicated a high precision in fitting the predicted data to their actual values. Analysis of variance results highlighted UV irradiation power as the most significant variable within the design space. In addition, the CuO/TiO2 photocatalyst demonstrated efficacy under visible light irradiation. Light-expanded clay aggregate beads were chosen as the substrate for photocatalyst immobilization, which enhanced the reaction rate. The stability of CuO/TiO2 was evidenced by about 2% reduction in efficiency after four degradation cycles.

Heterojunction-Based Photocatalytic Degradation of Rose Bengal Dye via Gold-Decorated α-Fe2O3-CeO2 Nanocomposites under Visible-Light Irradiation

Developing photocatalytic nanomaterials with unique physical and chemical features using low-cost and eco-friendly synthetic methods is highly desirable in wastewater treatment. In this work, the magnetically separable α-Fe2O3-CeO2 nanocomposite (NC), with its respective metal oxides of α-Fe2O3 and CeO2 nanoparticles, was synthesized using a combination of hexadecyltrimethylammonium bromide (CATB) and ascorbic acid via the hydrothermal method. To tune the band gap, the heterojunction nanocomposite of α-Fe2O3-CeO2 was decorated with plasmonic Au nanoparticles (Au NPs). The various characterization methods, such as FTIR, UV-vis DRS, XRD, XPS, TEM, EDX, SEM, and PL, were used to determine the properties of the materials, including their morphology, elemental composition, optical properties, band gap energy, and crystalline phase. The nanocomposite of α-Fe2O3-CeO2@Au was utilized to remove Rose Bengal (RB) dye from wastewater using a photocatalytic technique when exposed to visible light. A comprehensive investigation of the impact of the catalyst concentration and initial dye concentration was conducted to establish the optimal photodegradation conditions. The maximum photocatalytic efficiency of α-Fe2O3-CeO2@Au (50 mg L−1) for RB (20 ppm) dye removal was found to be 88.9% in 120 min under visible-light irradiation at a neutral pH of 7 and 30 °C. Various scavengers, such as benzoquinone (BQ; 0.5 mM), tert-butyl alcohol (TBA; 0.5 mM), and ethylenediaminetetraacetic acid (EDTA; 0.5 mM), were used to investigate the effects of different free radicals on the photocatalytic process. Furthermore, the reusability of the α-Fe2O3-CeO2@Au photocatalyst has also been explored. Furthermore, the investigation of the potential mechanism demonstrated that the heterojunction formed between α-Fe2O3 and CeO2, in combination with the presence of deposited Au NPs, led to an enhanced photocatalytic efficiency by effectively separating the photogenerated electron (e−)–hole (h+) pairs.

A Sustainable Approach for Enhancing Cationic Dyes Adsorption in Single and Multiple Systems using Novel Nano Ferrites Modified with Walnut Shell

AbstractWalnut shell has been used in various experimental studies for different dyes removal, but it is exciting to study the adsorption behaviour of bio‐waste (walnut shell) in combination with spinel zinc ferrite which resulted in the formation of a novel material having magnetic properties and help in easy separation after the wastewater treatment. Novel magnetic walnut shell zinc ferrite (WSZF) composite has been synthesized and used to remove Malachite Green and Methylene Blue from aqueous solution in single and binary dye systems. Different techniques have been used to characterize the composite such as Fourier Transform Infrared Spectroscopy, X‐Ray Diffraction, Field Emission Scanning Electron Microscopy, Energy Dispersive Spectroscopy, Thermogravimetric Analysis and pHzpc. Adsorption of dyes were studied to see the effect of time, pH, adsorbent dose, dye concentration and temperature. The Lagergren pseudo second order model fitted well among various kinetic models employed. Langmuir adsorption isotherm best fitted with maximum adsorption capacities of 86.20 and 169.5 mg/g in single dye and 23.92 and 18 mg/g respectively in binary dye system for Malachite Green and Methylene Blue. Process was spontaneous and ΔH° were found positive, confirmed endothermic process of adsorption. The composite‘s regeneration capacity was studied for five cycles and at the end of five cycle the efficiency of the material was found to be around 80 % for both single as well as binary dye systems. It is concluded that the chosen WSZF will be the optimum solution for cationic dyes removal.

An Enhanced Optical Response and Interfacial Charge Separation Of rGO Supported Cu2+ Doped Co3O4 Heterojunction For Photo‐Fenton‐Like Activity

AbstractIn recent years, clean water and increasing the usage of renewable energy have been the two main goals to be focused on in developing a sustainable living environment. These goals can also be fulfilled by using photocatalytic processes which is a promising direction, photocatalyst is quite effective for water purification and sustainable energy resources. For the first time, we report a visible‐light‐driven photocatalyst of rGO/Cu−Co3O4 nanocomposite for photo‐Fenton‐like degradation activity. The structural, morphological, surface chemical and optical properties of the samples were deeply analysed. The Cu2+ replacement reduces the crystalline size of the Co3O4 nanoparticle and rGO addition enhances the active surface area and charge mobility towards the better catalytic activity. The effect of operating parameters such as pH, catalyst dose, dye concentration, and H2O2 was also investigated for methylene blue (MB) dye degradation: kinetic studies, active radicals finding, and percentage of total organic carbon removal were also discussed in detail.

Self-enhanced regulation of stable organic radicals with polypeptide nanoparticles for mild second near-infrared phototheranostics

Stable organic radicals have emerged as a promising option to enhance fluorescence quantum yield (QY), gaining traction in medical treatment due to their unique electronic transitions from the ground state (D0) to the doublet excited state (D1). We synthesized a stable dicyanomethyl radical with a NIR-II fluorescence QY of 0.86 %, surpassing many NIR-II organic dyes. Subsequently, amphiphilic polymer-encapsulated nanoparticles (NPs) containing the radical were created, achieving a NIR-II fluorescence QY of 0.32 %, facilitating high-contrast bio-imaging. These CNPPs exhibit self-enhanced photothermal properties, elevating photothermal conversion efficiency (PCE) from 43.5 % to 57.5 % under 915 nm laser irradiation. This advancement enables more efficient photothermal therapy (PTT) with lower dye concentrations and reduced laser power, enhancing both feasibility and safety. Through regular fractionated mild photothermal therapy, we observed the release of damage-associated molecular patterns (DAMPs) and an increase in cytokine expression, culminating in combined mild phototherapy (m-PTT)-mediated immunogenic cell death (ICD). Consequently, we developed an immunostimulatory tumor vaccine, showcasing a novel approach for refining photothermal agents (PTA) and optimizing the PTT process.

Preparation, characterization, and photocatalytic performance of atmospheric plasma-sprayed TiO2/Al2O3 coatings on glass substrates

Conventional methods for wastewater treatment are not always efficient in persistent organic pollutant degradation processes. Therefore, low-cost and effective methods of their removal from sewage are constantly sought. This study presents an attempt to fabricate thermally sprayed ceramic coatings on glass and their characterization. Granulation of TiO2, Al2O3, and their blends in different mass ratios was done. Assessment of actual density and specific surface area was performed, and TiO2, Al2O3, and TiO2/Al2O3 were then used as a coating material for the deposition on glass substrates in atmospheric plasma spraying. Surface analysis of coatings was done by evaluating their roughness and wettability. Both powder and coatings samples were characterized using the X-ray diffraction method and scanning electron microscopy. The photocatalytic activity was estimated in the Eosin Y degradation process under UV light. UV–Vis spectroscopy was applied to observe the changes in the dye concentration. Additional tests for color measurements before and after photodegradation were carried out using a sphere spectrophotometer in CIELab color space. Particle size distribution was examined for the powder samples after the granulation and d50 was stated at 48.42–63.28 µm. Characterization of coatings via roughness measurements showed the average roughness of a surface equal to 4.90–9.65 µm. Moreover, most of the coatings appeared to be hydrophobic with water contact angles between 100° and 130°. All of the coatings showed Eosin Y degradation ability and the highest efficiency was reached for 100T/C, A75T/C, and A50T/C samples and stated at 71%, 62%, and 51%, respectively.Graphical abstract

Effect of poling on photocatalytic activity with SrBi4Ti4O15 catalyst

AbstractThis research article is related to a bismuth oxide‐layered pseudo‐perovskite ferroelectric material and its capabilities in the area of photocatalysis. SrBi4Ti4O15 (SBT) catalyst was prepared via a solid‐state reaction followed by calcination at 950°C sustained over 4 h. X‐ray diffraction, X‐ray photoelectron spectroscopy, bandgap analysis, Raman spectroscopy, and scanning electron microscopy confirmed the successful synthesis of the SBT catalyst. The photocatalysis capability was checked on a methylene blue (MB) model dye. The poling of the SBT catalyst was performed under 2 kV/mm of electric field. The poling of the catalyst material played a crucial role in enhancing the photocatalytic activity. Moreover, the effect of volume (k(v)), initial concentration (k(ic)) of the MB dye, amount of catalyst (k(c)), and intensity (k(i)) of the light were examined and analyzed by the mathematical model. This study suggested that higher intensity and amount of catalyst enhance photocatalytic activity, whereas higher concentration and volume of dye suppress the photocatalytic activity. The amount of catalyst showed the highest effect on the photocatalytic activity. The rate constant is influenced by these factors and the order of influence is k(c) > k(i) > k(v) ≃ k(ic).

Kinetics Analysis of Crystal Violet Adsorption from Aqueous Solution onto Flamboyant Pod Biochar

The increasing presence of presistent synthetic dyes, like crystal violet (CV), in wastewater poses a significant threat to aquatic ecosystems and human health due to its genotoxicity and carcinogenicity. Biochar derived from agricultural waste offers a promising, cost-effective, and eco-friendly approach for dye removal. This study explores the potential of flamboyant pod biochar (FPB) as a novel and sustainable adsorbent for CV removal. FPB offers a unique advantage as it utilizes readily available flamboyant pod waste, promoting waste valorization and a cost-effective approach. FPB was synthesized through a simple process involving milling, sun-drying, and pyrolyzing flamboyant pod waste at 300 °C. Batch adsorption experiments were conducted to evaluate the influence of contact time and initial dye concentration on removal efficiency. Kinetic modeling using pseudo-first-order and pseudo-second-order models explored the underlying mechanisms governing the adsorption process. The pseudo-second-order kinetic model exhibited a superior fit (R² > 0.87) compared to the pseudo-first-order model, suggesting a chemisorption mechanism governing the adsorption process. These findings demonstrate the potential of FPB as a low-cost, sustainable adsorbent for CV removal from wastewater.

Optimization of electrolyte co-additives, TiO2 thickness, and dye concentration for the enhanced performance of dye-sensitized solar cells

Optimization of electrolyte co-additives, TiO2 thickness, and dye concentration for the enhanced performance of dye-sensitized solar cells

Reviewing the effect of aggregates in Rhodamine 6G aqueous solution on fluorescence quantum efficiency

Rhodamines constitute a class of dyes extensively investigated and applied in various contexts, primarily attributed to their high luminescence quantum yield. This study delves into the impact of aggregation on the thermal and optical properties of Rhodamine 6G (R-6G) solutions in distilled water. Examined properties encompass thermal diffusivity (D), temperature coefficient of the refractive index (dn/dT), fluorescence quantum efficiency (η), and energy transfer (ET). These parameters were assessed through thermal lens (TL) and conventional absorption and emission spectroscopic techniques. The dimerization of R-6G solutions was revisited, revealing that an increase in R-6G concentration alters the features of absorption and emission spectra due to dimer formation, resulting in unexpected behavior of η. Consequently, we introduce a novel model for the fraction of absorbed energy converted into heat (φ), which accounts for emissions from both monomers and dimers. Employing this model, we investigate and discuss the concentration-dependent behaviors of η for monomers (ηm) and dimers (ηd). Notably, our findings demonstrate that ηm values necessitate ηd = 0.2, a relatively substantial value that cannot be disregarded. Additionally, applying the Förster theory for dipole–dipole electric ET, we calculate microparameters for ET between monomers (CDD) and monomer–dimer (CDA). Critical ranges for ET in each case are quantified. Microparameter analysis indicates that ET between monomer–monomer and monomer–dimer species of R-6G dissolved in distilled water holds significance, particularly in determining ηm. These results bear significance, especially in scenarios involving high dye concentrations. While applicable to R-6G in water, similar assessments in other media featuring aggregates are encouraged.

Basic Red 46 adsorption studies onto pyrolyzed by-product biomass

In this study, the objective was to examine the utilization of the pyrolyzed by-products biomass as an adsorbent for extracting the dye Basic Red 46 (BR 46) from a solution. The pyrolyzed by-product containing Pleurotus mutilus biomass was characterized by thermogravimetric analysis (TGA), FTIR and µXRF. Different parameters effects such as, adsorbent dose, solution pH, contact time, temperature and initial dye concentration on the adsorption capacity of the pyrolyzed by-product biomass were examined. The solution was analyzed before and after the adsorption studies. With adsorbent dose of 1 g/L, contact time of 14 min, and solution pH of 7.5, the optimum yield of 88% was achieved. In order to fit the equilibrium data, the Langmuir, Freundlich, Temkin, and Khan isotherm models were used, and in order to fit the kinetics data, the pseudo-first-order, pseudo-second-order, Elovich, and Ritchie models were employed. Statistical analysis such as R2, RMSE,χ2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\chi }^{2}$$\\end{document} and ARE was used to assess which model has the best fit with the experimental data. The results demonstrated that the experimental equilibrium data are well described by the Langmuir model, and the kinetic studies indicated that the adsorption of BR46 followed the Ritchie model. The greatest BR 46 adsorption capacity determined from experimental equilibrium data was around 135 mg/g at pH = 7.5, adsorbent dosage of 1 g/L. Moreover, thermodynamic analysis has demonstrated that the adsorption process was physical, exothermic, and spontaneous in nature. These results indicated that pyrolyzed by-product biomass might be used as a cheap material to extract textile colors out of aqueous effluents.

Biodegradation of aniline blue dye by salt-tolerant Bacillus thuringiensis DHC4 isolated from soil-feeding termite guts

The existence of aniline blue in aquatic environments poses a large threat to aquatic organisms. Microbial degradation of aniline blue has been frequently used in remediation because of its effectiveness, low cost, and environmental friendliness. However, the mechanisms by which the dye can be biodegraded are not well understood. In this study, Bacillus thuringiensis DHC4 was isolated from the gut of a soil-feeding termite, and its ability to degrade aniline blue was investigated. The results showed that DHC4 was highly resistant to both aniline blue and salt, with the decolorization rate reaching 78% and 67% after 96 h of incubation at initial dye concentrations of 1 g/L and 7% salinity, respectively. Aniline blue degradation products were identified based on UV–vis, FTIR, and GC–MS analyses, and genome analysis confirmed that DHC4 contained many potential dye-degrading genes. Transcriptome analysis revealed significant up-regulation of methyltransferase, nitroreductase, arylamine N-acetyltransferase and oxidoreductase genes on exposure to aniline blue, indicating their active role in its biodegradation. A new degradation pathway of aniline blue by DHC4 is proposed, based on analysis of metabolites and differentially expressed genes. This mechanism involves cleavage of aniline blue by oxidoreductases into mono- and diphenyl ring molecules, followed by further methylation and alkylation through methyltransferases. The phytotoxicity results showed that aniline blue was degraded by DHC4 into less toxic metabolites. These results provide new insights into the mechanism of biodegradation of aniline blue by microorganisms.

Synthesis and application of dual-functional sorbent SBA-15-Fe3O4-PDA-ODA for removing both water soluble and insoluble pollutants

In this study, inorganic-organic hybrid sorbent SBA-15-Fe3O4-PDA-ODA with functional groups having affinity for both water-soluble and insoluble pollutants was synthesized for treatment of wastewater where Malachite Green (MG) dye and motor oil coexist. In order to enhance the specific interactions between the sorbent and dye via functional groups of polydopamine (PDA), Fe3O4 nanoparticles were encapsulated with SBA-15 and surface functionalization with PDA was accomplished and then the surface of Fe3O4-SBA-15-PDA was modified with octadecylamine (ODA) to remove the oil present in the same environment with dye. While the SBA-15-Fe3O4-PDA-ODA directed to the aqueous phase by magnet provided MG removal thanks to the hydrophilic groups of PDA, it provided motor oil removal thanks to hydrophobicity of ODA when directed to the oil phase. 99.20 % dye removal and 9.24 g/g oil adsorption capacity were achieved from the environment where oil and dye were present together. Besides, the adsorption of MG on Fe3O4-SBA-15-PDA was searched at various pH, dye concentration, adsorbent dosage, and temperature in order to propose optimum experimental conditions for removal of dye and maximum adsorption capacity was determined as 95.83 mg g−1 at optimum conditions (10 mg adsorbent, 10 mg L−1 MG concentration, pH 9). Interaction mechanism between dye and Fe3O4-SBA-15-PDA was explained by studying the adsorption behavior of sorbent derived from the isotherm and kinetic results. The sorbents were characterized by FT-IR, XRD, SEM, N2-adsorption/desorption, water-contact-angle, and VSM measurements. SBA-15-Fe3O4-PDA-ODA sorbent was tested for three successive adsorption cycles for both dye and oil and eventuated insignificant loss in activity when they were recycled. Easy and low-cost fabrication protocol, controllable removal ability of dye and oil will facilitate its versatility in environmental cleanup process for water soluble and insoluble pollutants.