High Dye Concentration Research Articles

Graphene Oxide/Fe3O4/Chitosan−Coated Nonwoven Polyester Fabric Extracted from Disposable Face Mask for Enhanced Efficiency of Organic Dye Adsorption

Owing to the COVID-19 pandemic, huge amounts of disposable face masks have been manufactured and used, and these discarded face masks have to be treated. In this study, we propose a simple approach for reusing the nonwoven polyester fabric (NWPF) from disposable face masks. In this approach, NWPF is utilized as a supporter for coating of a layer of graphene oxide/Fe3O4/chitosan (GFC) to form a GFC/NWPF adsorbent at room temperature via a simple spray coating method that does not require any solvent. The specific properties of GFC, NWPF, and the GFC/NWPF adsorbent were analysed via X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy, vibrating sample magnetometry, and field-emission scanning electron microscopy. Results showed that the presence of NWPF enhanced the adsorption capacity of GFC towards organic dyes. At high concentrations of the organic dyes, the adsorption efficiency of the GFC/NWPF adsorbent to the dyes reached 100% within 24 h. The adsorption capacity ([Formula: see text]) of the GFC/NWPF adsorbent to methylene blue, methyl orange, Congo red, and moderacid red was 54.795, 87.489, 88.573, and 29.010 mg g−1, respectively, which were considerably higher than that of bulk GFC (39.308, 82.304, 52.910, and 21.249 mg g−1, respectively).

Improved performance of immobilized laccase for catalytic degradation of synthetic dyes using redox mediators

Immobilized laccase had high and sustainable removal efficiencies for high concentrations of synthetic dyes in the presence of mediators.

A robust and renewable solar steam generator for high concentration dye wastewater purification

An optimized T-shaped Au/ceramic solar steam generator was fabricated, showing good robustness, pH and thermal stability. The blocked generator after long-term purification of high concentration dye wastewater can be regenerated by calcination.

Photocatalytic process augmented with micro/nano bubble aeration for enhanced degradation of synthetic dyes in wastewater

This research combines TiO2 nanopowder photocatalyst (TNP) with micro/nano bubble aeration (MNBA) to enhance the dye degradation of the photocatalytic process treating synthetic dye wastewater. The experimental synthetic dyes were indigo carmine (IC) and reactive black 5 (RB5). The dye degradation performance of the photocatalytic process without MNBA (TNP ​+ ​UVA) and with MNBA (TNP ​+ ​UVA ​+ ​MNBA) under various initial dye concentrations were evaluated. The results showed that, given the initial IC and RB5 dye concentrations of 2 ​μM, the degradation efficiency of TNP ​+ ​UVA and TNP ​+ ​UVA ​+ ​MNBA were 100%. With higher dye concentrations (4–10 ​μM), the degradation efficiency of TNP ​+ ​UVA and TNP ​+ ​UVA ​+ ​MNBA were between 84.05-98.20% and 90.64–100%. The kinetics of the photodegradation reaction of both dyes were described by the Langmuir-Hinshelwood kinetic model. The pseudo first order degradation rate constants of the photocatalytic process with MNBA were 1.44 and 1.66 times higher than those without MNBA for IC and RB5.

Barium alginate as a skeleton coating graphene oxide and bentonite-derived composites: Excellent adsorbent based on predictive design for the enhanced adsorption of methylene blue

The phenomenon that calcium alginate does not exhibit high adsorption capacity as a carrier material has not been reasonably explained or solved. In this paper, a new viewpoint that the orbital energy level of metal ions and the binding degree of the α-l-guluronate and β-d-mannuronate units affect the adsorption performance of the composite was innovatively proposed. Taking barium alginate (BA) as an example, the possibility of replacing calcium alginate is discussed. Barium alginate/graphene oxide (BA/GO) membranes and three-dimensional (3D) barium alginate-bentonite-graphene oxide derived (3D-BA) hydrogels were prepared by vacuum freeze-drying to remove methylene blue. The structure and morphology of the prepared adsorbents were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry and Fourier transform infrared spectroscopy. The effects of adsorbent dosage, doping ratio, temperature, contact time, pH value and initial dye concentration on the adsorption performance of BA composites were investigated. The adsorption capacities of the BA/GO and 3D-BA materials were 1011.3 and 710.3 mg/g, respectively. The BA/GO membrane exhibited stable filtration performance against high concentrations of dyes. Benefiting from the strong interaction between bentonite, sodium alginate and Ba2+, the 3D-BA hydrogel showed higher thermal stability and better adsorption efficiency than other materials. The Elovich kinetic model and Sips equation can appropriately describe the adsorption process. The results show that barium alginate is a better carrier material than calcium alginate.

Using Laminar Nanoclays for Phycocyanin and Phycoerythrin Stabilization as New Natural Hybrid Pigments from Microalgae Extraction

C-Phycocyanin (PC) and B-phycoerythrin (PE) are light-harvesting water-soluble phycobiliproteins from microalgae that belong mainly to the cyanobaceria and rhodhophytes families. Different methods have been developed for PC and PE extraction and purification from microalgae, and offer a high potential for their use as additives in sectors such as food and cosmetics. However, the main limitations of using these dyes are the sensitivity of their environmental factors, such as light fastness, temperature, and pH. We successfully employed safe lamellar nanoclays such as montmorillonite (M) and Laponite (L) for phycobiliproteins stabilization, as we did before with other natural dyes. We obtained a wide color gamut from blues to pink by combining four different factors under synthesis conditions: three dye concentrations; two laminar nanoclay sizes; a two nanoclay surface modifiers combination with cetylpyridinium bromide (CPB) and a coupling agent (3-Aminopropyl) triethoxysilane. The experimental conditions were defined according to a multilevel factorial design of experiment (DOE) to study the factors interacting in the final hybrid pigment characteristics. In both M and L, the d001 distance (nm) increased due to PC and PE adsorption. The best conditions to increase the basal space depend on the nanoclay structure, and it is better to use the surfactant for M, and silane modification for L. In addition, optical and thermal PE and PC properties significantly improved. We show the optimal synthesis conditions to increase PC and PE adsorption using the high dye concentration, with surfactant and silane depending on the nanoclay. The hybrid pigments from these phycobiliproteins offer the opportunity to perform several industrial applications, including in polymer additives, cosmetics, and packaging.

Third-order optical nonlinearity of DSR13/THF solutions under CW He–Ne laser irradiation using Z-scan method

The Z-scan technique was employed to explore the third-order nonlinear optical properties of disperse red 13 organic chromophore solutions in tetrahydrofuran. A continuous-wave He–Ne laser (632.8 nm) was used as a source of irradiation. The nonlinear absorption and nonlinear refractive index coefficients of this dye were investigated. The results showed that this dye has a good nonlinear response with its real and imaginary quantities of third-order susceptibility. The solutions showed negative nonlinear refraction. The best obtained value of the third-order susceptibility was 6.37 × 10–3 esu at a dye concentration of 3.15 × 10–4 mol/L. Moreover, the nonlinear optical properties were enhanced with higher dye concentrations, and an elevated trend in nonlinear absorption and nonlinear refractive index coefficients was observed. Also, it was found that the reverse saturable absorption was the main mechanism responsible for the two-photon absorption effect in DSR13/THF samples.

Efficient Design and Sustainability Assessment of Wastewater Treatment Networks using the P-graph Approach: A Tannery Waste Case Study

In the tannery industry approximately, 30 - 35 m3 of wastewater (WW) is generated per ton of rawhide processed. The WW comprises high concentrations of salts, ammonia, dye, solvents, and chromium. Of particular interest is chromium, which has been proven to cause dermatological, developmental, and reproductive issues on exposure. Thus, there is a need for appropriate treatment of the tannery WW before it is discharged for natural remediation. However, designing a treatment process is multifaceted due to the availability of multiple technologies that can perform similar tasks and the complex composition of waste streams. This necessitates the treatment to be performed in stages namely, primary, secondary, and tertiary. In some cases, pretreatment is required to enhance the recovery in the following stages. Due to the combinatorial nature of this problem, the P-graph approach, which uses principles from graph theory, can be used to synthesize a treatment pathway by selecting appropriate technologies at each stage, while meeting required purity specifications. Furthermore, the P-graph approach can provide alternate feasible treatment structures ranked based on Economics as well as Sustainability indicators, such as the Sustainable Process Index (SPI). In this work, a tannery WW case study is investigated with multiple stages and treatment technologies. A complex maximal structure is generated comprising all possible technologies, flows, connections, bypasses, mixers, and splitters. The models for each technology involve capital and operating costs, efficiency, and SPI at each stage of the treatment process. This problem is formulated in P-graph and solved using the Accelerated Branch-and-Bound algorithm.

Hollow fiber membrane applied for Sasirangan wastewater desalination integrated with photocatalysis and pervaporation set-up

Nowadays, the difficulty to access a clean water has been increased due to environmental pollution by human activities. Sasirangan is a traditional fabric from South Kalimantan. The process produced a wastewater which contains a high concentration of textile dye and total dissolved solids (TDS). It is carcinogenic to humans and potentially dangerous to biota. To overcome this problem, a hollow fiber membrane technology has employed to reject the contaminants from Sasirangan wastewater. The purpose of this study to determinate the performance of pervaporation hollow fiber membrane-photocatalytic for treating the Sasirangan wastewater. TiO2 has chosen as a catalyst in photocatalytic process with variations of 0; 0.5; 1; 1.5; 2; and 2.5%. These processes provide the highest water flux of 4.35 Kg.m−2.h−1 as well as good rejection in color of 98.02%, TDS of 2.345 mg/L, and conductivity (3.5µS) for 2.5% TiO2. Overall, the photocatalytic coupling with the pervaporation resulting in a remarkable effect on pollutants rejection for Sasirangan wastewater.

Optimization of Crystal Violet Dye Removal in Fixed Bed Column Using Eucalyptus camaldulensis as a Low-Cost Adsorbent

Adsorption through waste adsorbents is one of the developing technologies used for treating textile wastewater. The present study explores the possible outcome of Eucalyptus camaldulensis biomass as an adsorbent for removing crystal violet dye from aqueous solutions. Eucalyptus camaldulensis biomass was used as such and used in fixed bed column mode to testify its potential at different parameters. Effect of different constraints like bed height (cm), flow rate (mlmin-1), initial dye concentration (mgL-1), and pH were studied along with breakthrough curve and exhaust time. Maximum breakthrough curve and exhaust time and utilization of mass transfer zone were observed at bed height of 20 cm. However, the promising results are obtained at higher dye concentration (50 mgL-1), lower flow rate (1 mlmin-1), and at lower pH of 5. This study reveals promising results at acidic pH. This study reflects that adsorption capacity and breakthrough curve favor lower acidic pH. The adsorption data in batch mode follow the Langmuir isotherm and best fit to pseudo-second-order reaction kinetics. The breakthrough curve and mass transfer zone are individually testified, and the breakthrough curve obeys the assumptions of the Thomas model, and R2 (0.933-0.997) values confirm the data that its best fit with the Thomas model.

Comment on "Emissive H-Aggregates of an Ultrafast Molecular Rotor: A Promising Platform for Sensing Heparin".

For heparin sensing, Mudliar and Singh developed fluorescence and absorption spectroscopic approaches by utilizing emissive H-aggregates of thioflavin T (ThT) formed upon heparin binding. It has been proposed that the methods work not only in pure aqueous solution but also in complex biological media such as human serum. However, the optical features used to detect and quantify heparin are very sensitive to the ionic strength of the solution and completely vanish at 1.45 mM NaCl. Curiously, the authors were able to determine the heparin content of 1% serum samples containing the same level of electrolyte. In addition, the experimental conditions employed for heparin detection in serum samples were substantially modified, reducing the optical path length from 1 to 0.1 cm and increasing the dye concentration by an unknown measure. ThT shows a concentration-dependent tendency for aqueous aggregation, which markedly modifies its absorption and fluorescence properties. The authors have failed to verify that spectral characteristics of the ThT-heparin system observed in pure aqueous medium remain unchanged at higher dye concentrations and in the presence of serum components. Taking these issues into consideration, the heparin detection scheme offered for serum samples cannot be reproduced.

Determination of suitable wavelengths in dye concentration estimation by spectral analysis of K/S’s scalability

K/S and reflectance graphs are essential tools in characterizing the dyeing behavior. In textile coloration, estimating the dye concentration is poor using the Kubelka-Munk model due to its low scalability and deviation of the reflectance function from linearity after low dye concentrations, particularly in the wavelengths where the gradient of K/S against dye concentration is noticeable. This paper focused on extending the validity of the Kubelka-Munk function, which originates from the linearity of reflectance function against higher dye concentration. A data set of dyed polyester specimens with three disperse dyes in a dye concentration range was prepared. At the present work, K/S was analyzed by describing the scalability property, and the suitable wavelengths in the visible spectrum where K/S benefits from minor deviation from linearity were also discussed. It was observed that the K/S function is not always scalable and deviates in λ max after a specific dye concentration for K/S > 17. Accordingly, the wavelengths other than λ max were found that could be as important as λ max. For the K/S values > 25, no practical region was achieved.

Decolourization of azo dye using a batch bioreactor by an indigenous bacterium Enterobacter aerogenes ES014 from the waste water dye effluent and toxicity analysis

Effluents of textile industries caused serious environmental problem throughout the world. In this study, a total of 23 bacterial strains from five bacterial species were isolated from the dye effluent. Of these strains, a unique and novel Enterobacter aerogenes ES014 was utilized for dye decolourization and toxicity analysis. The selected strain could effectively decolourize three selected azo dyes. It showed the capability for decolourizing acid orange (82.3 ± 3.6%), methyl orange (78.2 ± 3.3%), and congo red (81.5 ± 3.2%). The selected bacterial strain significantly decolourized 100 mg/L acid orange at 35 °C, pH 7.5 with 6% sodium chloride concentration. Most of the tested nitrogen and carbon sources effectively enhanced decolourization process. It showed the ability to decolourize acid orange in the culture medium containing 1.5% glucose (100 ± 2.8%) and 0.8% beef extract (100 ± 3.1%). A laboratory-scale batch bioreactor was used to decolourize azo dye at optimized culture conditions. The decolourizing ability improved with 100 mL/h hydraulic retention time. The treated wastewater quality was improved due to sharp depletion of Total Dissolved Solids (TDS), pH, Chemical Oxygen Demand (COD), alkalinity and sulphate concentration. The selected bacteria has the potential to produce dye degrading laccase. Laccase was detected during fermentation process in batch bioreactor as a key enzyme for decolourization produced by E. aerogenes ES014. Phytotoxicity and acute toxicity analysis were performed using Arachis hypogaea (pea nut) seed and first instar larvae of Artemia parthenogenetica (brine shrimp). The seed germination rate of treated wastewater was improved (94.3 ± 1.8%) and enhanced survival rate (91.7 ± 2.9%) in the first instar Artemia larvae treated with wastewater after 24 h. Overall, E. aerogenes ES014, might be a promising bacterial strain for the treatment of textile effluents with high azo dye concentrations.

Effects of ferroferric oxide on azo dye degradation in a sulfate-containing anaerobic reactor: From electron transfer capacity and microbial community

Anaerobic decolorization of azo dye in sulfate-containing wastewater has been regarded as an economical and effective method, but it is generally limited by the high concentration of azo dye and accumulation of toxic intermediates. To address this problem, Fe3O4 was added to one of the anaerobic reactors to investigate the effects on system performances. Results showed that AO7 removal rate, COD removal rate, and sulfate reduction were enhanced with the addition of Fe3O4 under various influent AO7 concentrations (153 mgCOD/L – 1787 mgCOD/L). According to the proposed pathway for the degradation of AO7, more intermediates (2-hydroxy-1,4-naphthoquinone, phthalide, 4-methylphenol) were produced in the presence of Fe3O4. The electron transfer capacity of sludge was also increased since Fe3O4 could stimulate to secrete humic acid-like organics in EPS. Microbial analysis showed that iron-reducing bacteria like Clostridium and Geobacter were also enriched, which were capable of azo dye and aromatic compounds degradation.

Batik wastewater treatment by the hydrodynamic cavitation and Ozonation with coagulation-flocculation pretreatment

Wastewater discharged by Batik’s industry still contains a high concentration of dyes and pollutants, thus can contaminate the water’s ecosystem. Because of that, in this study, Batik wastewater was treated by the hydrodynamic cavitation, ozonation, and combination of those two. By using PAC, a coagulation-flocculation-based pretreatment technic was conducted first to increase the effectiveness of the main wastewater treatment process. Then, variations in flow rate (2 L/min, 4 L/min, and 6 L/min) and initial pH of wastewater (4, 7, and 10) were evaluated to analyze its effect on the pH changing and the degradation of TSS, COD, color (Pt-Co), and TOC. The best result obtained from this research was by the application of the combination technic, which can eliminate 95.19%; 78.85%; 96.42%; and 60.56% of TSS, COD, color (Pt-Co), and TOC, respectively after 60 minutes treatment.

Usability of spent Salvia officinalis as a low-cost adsorbent in the removal of toxic dyes: waste assessment and circular economy

ABSTRACT The removal of methylene blue (MB) and maxilon yellow (MY) dyes from aqueous solutions was investigated by an adsorption process using spent Salvia officinalis (SSO) for the first time. The operating conditions and mechanisms for the MB-SSO and MY-SSO adsorption systems were determined. FTIR-ATR and SEM-EDAX analyses were also performed to characterise the adsorbent. Optimum conditions in each system were similarly obtained, excluding pH (5.7 for MB and 6.5 for MY). The dye removal efficiency was 78% for MB and 56% for MY. It was observed that experimental data fits Freundlich isotherm (R2 ≈ 0.97) and pseudo-second-order kinetic (R2 ≈ 0.99) model in both systems. The maximum adsorption capacities of SSO for MB and MY dyes were determined as 16.53 and 11.79 mg g−1, respectively. The pseudo-second-order kinetic model revealed that adsorption efficiency was affected by a number of active sites on the adsorbent and the concentration of the dye. The thermodynamic parameters confirmed that adsorption was spontaneous, exothermic and physisorption in both adsorption systems. The results indicate that SSO can be used as a promising adsorbent material for removal of MB and MY dye from aqueous solutions. However, in order to remove high dye concentrations, SSO must be activated.

Reoxidation of graphene oxide: Impact on the structure, chemical composition, morphology and dye adsorption properties

The chemical composition, oxidation degree, and sheet size strongly affect the properties of graphene oxide (GO). Therefore, much effort has been directed to improve the synthesis of GO and control its structure. Herein, we report the reoxidation of GO using milder conditions of a modified Hummers’ method, including shorter reaction times and a reduced proportion of chemicals to obtain the reoxidized GO (Ox-GO). The reoxidation impact was evaluated by studying the materials’ adsorption performance towards methylene blue (MB) and rhodamine B (RB). Compared to GO, Ox-GO presents a similar C/O ratio, increased interlayer spacing, smaller sheets with holes, a higher exfoliation degree, and slight differences in each oxygenated functional group. Our measurements evidence that Ox-GO has an MB adsorption capacity more than 30% higher than GO under different conditions of dye concentration and pH. Moreover, Ox-GO also shows a notable improvement in the RB removal for a high dye concentration, where the removal capacity is almost 40% higher than that of GO. The enhancements in the dyes’ removal are attributed to the increased accessible surface area of Ox-GO, which provides more sites for dyes’ adsorption.

Random laser and stimulated Raman scattering in compressible porous polymeric foam

In this work, Random laser (RL) and stimulated Raman scattering (SRS) are investigated using Rhodamine 6G ethanol solution in poly (melamine formaldehyde) foam with micro/nano-sized porous structures. At low dye concentration, the RL containing multiple discrete narrow peaks is observed in both its natural and compressed state of foam. It is found that the cavity length in the compressed state is significantly shorter through the power Fourier transform of the spectra. At high dye concentration, in the natural state of the foam, the coexistence of the RL and SRS is observed, while only the SRS peaks appear in the compressed state. It may provide a novel approach to achieving mode-controllable RL emission.

Coupling electrocoagulation and solar photocatalysis for electro- and photo-catalytic removal of carmoisine by Ag/graphitic carbon nitride: Optimization by process modeling and kinetic studies

Graphitic carbon nitride, g-C3N4, have been receiving intense attention the last decades due to its unique physicochemical properties, and even more importantly, due to the visible light driven photoreactivity. Hence, the design and synthesis of novel photocatalysts based on g-C3N4 is a prosperous approach towards water and wastewater treatment, especially against pollutants of organic nature. Among the various water treatment techniques, electrocoagulation (EC) has the advantages of economical and operational benefits, while photocatalytic approaches, and particularly the solar light driven ones, are assumed as the future towards sustainable design of modern industrialization. Herein, we present a process intensification aspect for environmental remediation applications by coupling EC and photocatalysis processes for the removal of the azo dye carmoisine. The iron-iron electrodes showed a superior removal efficiency of 37% compared to aluminum-aluminum electrodes (23%) for a initial high dye concentration. Regarding the photocatalytic degradation of carmoisine, g-C3N4 doped with 2% Ag showed a higher dye removal efficiency (31%) related to 5% Ag doping (21%). Two quadratic models for dye removal were developed by carrying the experiments according to full factorial design and Box–Behnken design (BBD) for EC and photocatalysis processes, respectively. The models revealed that the electrical potential in EC and irradiation time in photocatalysis are the main variables which affect the process efficiency. The highest dye removal efficiency of 77% in EC was achieved when pH, electric potential, and time were set to 5, 15 V, and 60 min, respectively. Moreover, the optimal conditions for a 90% photocatalytic dye removal was 7.96, 0.59 g/L, 119.8 min, and 62.5 mg/L for pH, Ag(2%)/g-C3N4 dose, solar irradiation time, and initial carmoisine concentration, respectively. The removal efficiency did not change after 3 cycles indicating a physicochemical stability of the photocatalyst. The experimental data were well described well by first and pseudo-first order of kinetic models. Coupling EC and solar-driven photocatalysis showed to be a promising efficient dye removal approach, bearing in mind the need for economic and environmental-friendly method for environmental remediation applications.

Decolorisation of Azo Dye Congo Red (CR) by Termitomyces sp. Biomass

Aims: A study was conducted to evaluate decoloration of azo dye, Congo Red (CR) using fungal hyphal mat of beneficial bacidiomycete Termitomyces sp. TMS7 (MW694830) as bio sorbent material.
 Study design: Completely randomized block design (CRD).
 Place and duration of study: Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India, between September 2019 and January 2020.
 Methodology: Isolation of white rot fungus from basidiocarb was done and screened based on their ligninolytic enzyme activity and Isolate TMS 7 was selected as best isolate and identified through ITS 1 and ITS 4 primers. Efficiency of fungal biomass to decolorize Congo red was assessed and per cent decoloration and kinetics were calculated.
 Results: Twelve fungal isolates were obtained and Isolate TMS 7 was selected as best isolate based on enzymatic activity. TMS 7 was identified as Termitomyces sp. using ITS 1 and ITS 4 primer. Ligninolytic enzymes i.e. cellulase (9.97 µ mol of glucose released/min/mg protein), and xylanase (9.55 µ mol of xylose released/min/mg protein) were quantified from the crude fungal extract of TMS 7, which was higher than standard (Termitomyces albuminosus -MTCC 1366). Decolorisation efficiency of termitomyces fungal biomass (1 g/100 ml) against different concentration of congo red dye (50-250 mg/L) was assessed. About 100 % (99.9) degradation was recorded in the minimum dye concentration of 50 mg/L within 3 days and 8 % decoloration was achieved at the highest dye concentration (250 mg/L) within 5 days.
 Conclusion: Possible mechanism of degradation is the presence of lignolytic enzyme especially cellulase, xylanase in the culture filtrate and bio sorption of degraded product by the fungal cell wall components viz., chitin, glucan other complex polymers.