Direct Blue 15 Research Articles

Adsorption of Acid Yellow 36 and direct blue 86 dyes to Delonix regia biochar-sulphur

This study aims to investigate a new approach to removing hazardous dyes like Direct Blue 86 (DB86) and Acid Yellow 36 (AY36) from aqueous environments. Delonix regia biochar-sulphur (DRB-S), made from Delonix regia seed pods (DPSPs), is an inexpensive and environmentally friendly adsorbent. Different characterization investigations using BJH, BET, FTIR, SEM, DSC, TGA, and EDX were utilized in the descriptions of the DRB-S biosorbent. The optimal pH for AY36 dye and DB86 dye adsorption to the DRB-S adsorvbent was at pH 1.5. For the adsorption of AY36 and DB86 to DRB-S, equilibrium was attained at 30 and 90 min of reaction time interaction. The Langmuir model (LGM) and pseudo-second-order-model (PSOM) best describe the biosorption of both dye molecules to the biosorbent owing to the equal and homogeneous spread of the dye molecules over the biosorbent porous surface and a chemisorption process which involved the valency force through the exchange of electrons between the dye molecules and the prepared biosorbent. The determined biosorption capacities for both dyes (AY36 and DB86) were found to be 270.27 mg/g and 36.23 mg/g, respectively. In conclusion, this recently synthesised DRB-S adsorbent exhibited an impressive sorption capacity and successfully removed AY36 and DB86 dyes. This suggests that the biosorbent has potential applications in wastewater treatment and can be recycled without affecting its adsorption effectiveness.

Synthesis and Characterization of Sodium Carboxymethyl Cellulose/Chitosan/Polyvinyl Alcohol Hydrogels to Removal Ionic Dyes and Their Biodegaration

ABSTRACTHydrogels from polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (CMC), chitosan (CS) were syntheised via gamma irradiation at different radaition dose; 0, 2.5, 5, 10, and 20 kGy. The syntheized hydrogels were chataerized by gelation (%), swelling (%), XRD, and SEM to confirm the hydrogel formations. The hydrogels were used to remove dyes of direct blue 1 (DB1), methylene blue (MB) from their aqueous soltions. The effect of contact time, feeding intial concentration and temperature were investigated. The adsorption of kinetics models such pseudo first‐order, pseudo second‐order, and Bangham were studied. The results of kinetics invetsiation showed that DB1 obeys pseudo second‐order, while MB obeys pseudo first‐order. Moreover, the adsorption iostherms of Langmuir isotherm model, Freundlich, Redlich–Peterson isotherm, Sips isotherm, Hill isotherm were applied. The outcome results referred that both of DB1 and MB obey Langmuir model. Further, the Soil degradability test of pure hydrogels and hydrogels‐adsorbed DB1 and hydrogels‐adsorbed MB was carried out by burial under soil for 14 days. The results showed the pure hydrogels exposed rapid soil degradability than hydrogels‐adsorbed DB1 and hydrogels‐adsorbed MB. Furthermore, water‐holding capacity and water retention of sandy soils of hydrogels were studied. The results of water‐holding capacity and water retention showed that the hydrogels that prepared at 20 kGy is highest one than that prepared at 2.5 kGy is the lowest one.

A Combination of Adsorption and Photocatalysis Processes for the Removal of Direct Blue 71 (DB71) Dye on Fe-Doped Layered Double Hydroxides

Pollution in ecosystems has increased, especially in water, due to the pollutant agents that alter their chemical, physical and biological characteristics. This requires actions to resolve or at least reduce the harmful effects generated on the environment and people’s health. Many of the contaminants present in water come from the industrial sector, with the textile industry being one of the most impactful as it uses mostly synthetic dyes, which are characterized as being recalcitrant and toxic, so they cannot be degraded by conventional water treatment methods. Advanced oxidation processes have a great potential for application, especially those that use heterogeneous photocatalysis. The present research evaluates the efficiency in the adsorption and degradation of the triazoic Direct Blue 71 dye in aqueous mediums at concentrations of 600 ppm by the heterogeneous photocatalysis method. The photocatalysts used are layered double hydroxides (LDHs) with a Mg/Al = 3 ratio and are thermally activated and doped with Fe at 1, 3 and 5% w/w. The most efficient materials achieved removal percentages greater than 80% by means of a second-order kinetic model with a DB71 half-life decolorization of less than one hour; as shown by an HPLC study, the absence of intermediate products would confirm the mineralization of the dye.

Homogeneously assembled covalent organic framework membrane co-stitched by β-cyclodextrin and chitosan for dye separation

Covalent organic frameworks (COFs) based membranes have demonstrated great potential in molecular separation. However, COFs are usually synthesized as powders, and difficult to form large-area and highly crystalline membranes. There normally exists unfavorable crystal flaws and stacking defects in membranes, impairing their rejection performance. The severe reaction conditions of solvothermal synthesis also inhibit their fabrication. Here, a comprehensive strategy was developed to fabricate a homogeneously assembled COF membrane co-stitched by β-cyclodextrin (β-CD) and chitosan (CS). Specifically, the COF crystallites (named TATP) were homogeneously formed and assembled to be films at room temperature under the control of n-propylamine; The aminated CS chemically bonded the TATP crystallites on the substrate and helped assemble them to form dense films. β-CD molecules were subsequently embedded into the TATP layer and crosslinked to further stitch membrane defects. The prepared CD-TATP-NH2CS/nylon membrane demonstrated enhanced excellent rejection performance. It could reject 100 % of R250 (BB), Congo red, Direct blue15, and 99.4 % of Alcian blue. It also could selectively separate Methyl orange (MO) and BB mixed solutions with only MO passing through, owing to the co-stitching of the membrane defects by β-CD and CS. This study provides a significant concept and strategy for fabricating high-performance COF membranes.

New study of the adsorption mechanism of different dye molecules by high porous sludge activated carbon produced from a dairy-treatment effluent plant

In this study, a high-quality porous sludge-activated carbon from a dairy-treatment effluent plant in México (ACSDM) was produced, characterized, and investigated in the adsorption of 8 different dyes. The main focus was establishing how the dyes' molecular characteristics affect adsorption. So, the intrinsic characteristics of the different dye molecules were correlated with the experimental adsorption data. ACSDM proved high quality, considering their textural properties and physical-chemical characteristics. Adsorption was efficient using the natural pH of each dye solution and 1 g L−1 of ACSDM. The highest adsorption capacities were obtained in the following order: Methylene Blue (MB) (998.44 mg g−1), Crystal Violet (CV) (795.65 mg g−1), Fuchsine (F) (342.52 mg g−1), Direct Blue 86 (DB-86) (306.36 mg g−1), Alizarin Green (AG) (303.25 mg g−1), Reactive Black 5 (RB-5) (259.82 mg g−1), Methanil Yellow (MY) (252.81 mg g−1) and Amaranth Red (AR) (251.12 mg g−1). These results were obtained at 55 °C (endothermic process), except for MY, where the adsorption was exothermic (25 °C). Freundlich was the model that best fitted the DB-86, MB, and CV equilibrium data. While the Langmuir and Tóth models best fit the RB-5, AR, and MY isotherms. Tóth also best represented the F and AG data. Kinetic curves demonstrated that adsorption occurred faster for dyes MB, F, CV, MY, AR, and RB-5, respectively, reaching 90 %-99 % of their saturations in the first 30 minutes. Meanwhile, the adsorption of AG and DB-86 only about 85 % of the saturation occurred. The study indicated that molecular volume is the major variable in the dye adsorption process, as well as some individual chemical characteristics of the molecule.

Heteroatom doped biochar-aluminosilicate composite as a green alternative for the removal of hazardous dyes: Functional characterization and modeling studies

In this work, a novel nitrogen-doped biochar bentonite composite was synthesized by a single-pot co-pyrolysis method. Batch studies were conducted to evaluate the performance of the developed composite in eliminating synthetic dyes from the aqueous matrix. Energy dispersive X-ray spectroscopy analysis and field emission scanning electron microscopy imaging confirmed the N doping and bentonite impregnation into biochar. X-ray photoelectron spectroscopy analysis revealed that the N atoms were doped interstitially into the carbon matrix of biochar in the form of pyridinic and pyrrolic nitrogen. Simultaneous heteroatom doping and bentonite impregnation reduced the specific surface area to 41.721 m2 g−1 but improved the adsorption capacity of biochar for dye adsorption. Further experimental studies depicted that simultaneous bentonite impregnation and N doping into the biochar matrix is beneficial for direct blue-6 (DB-6) and methylene blue (MB) removal and maximum adsorption capacities of 53.17 mg. g−1 and 41.33 mg. g−1 were obtained for MB and DB-6, respectively, at varying conditions. Adsorption energetics of the dyes with the developed composite portrayed the spontaneity of the process through negative ΔG values. The Langmuir and Freundlich isotherm models fitted the best for MB and DB-6 adsorption. The monolayer adsorption capacity and favourability factor for MB and DB-6 adsorption were calculated to be 54.15 mg. g−1 and 0.217, respectively from the best-fitted isotherms. Based on density functional theory calculations and spectroscopic studies, major interactions governing the adsorption were predicted to be charge-based interactions, π-π interactions, H-bonding, and Lewis acid-base interactions.

A Study of Nanostructured FeO Thin Film-Based Allure Red and Direct Blue 15 Azo Dyes Sensing Scheme

This study reports on the amperometric sensing properties of FeO/Fe2O3 thin films for the detection of Allura Red (AR) and Direct Blue 15 (DB15) Azo dyes. The FeO/Fe2O3 thin films were produced using the Sequential Ionic Layer Adsorption and Reaction (SILAR) method and Na+-doping. The morphological and structural properties of the nanocomposites produced at pH of 10.5 showed good properties for the detection of azo dyes. The linear curve fit equations for AR and DB15 droplet applications onto Na+-doped FeO nanocomposite thin film samples were found to be y = -0.0002x + 0.0043 (R² = 0.9143) and y = -7E-05x + 0.0005 (R² = 0.9809), respectively. The findings reveal that adding Na+ doping to FeO/Fe2O3 thin films can effectively increase the detection response for the target azo dyes and enhance the sensitivity of the sensing system. The results suggest that the SILAR method can be used to produce low-cost and reusable FeO/Fe2O3 thin film devices, which can be promising candidates for the detection of toxic azo dyes in liquid samples.

In-silico and in-vitro targeting of organic dye pollutants from synthetic and real wastewater by the hierarchically self-assembled laccase@bismuth phosphate hybrid nanorods

The increasing presence of dyes in wastewater and even surface or groundwater has progressively become an emerging global concern. This study evaluated the potential use of facile, straightforward, and hierarchical laccase@BiPO4•hybrid nanostructures (HNSs) in the elimination of anthraquinone, monoazo, diazo, and triarylmethane dyes from municipal wastewater through in-silico and in-vitro analyses. The prepared HNSs possessed rod-like morphological features with more than 8 cycles of reusability and about 10 U mg–1 catalytic activity. The nitrogen sorption analysis revealed that the prepared HNRs presented a Brunauer-Emmett-Teller (BET) surface area of 15.3 ± 1.6 m2 g−1 and an average pore size of 9.7 ± 0.5 nm. The total pore volume of HNRs was also measured at 4.0 ± 0.1 (× 10−2 cm3 g−1). Molecular docking predicted the preferred orientation of dye molecules with the enzyme's active site, facilitating the formation of stable complexes. The constructed hybrid nanorods (HNRs) showed proper in-vitro oxidation activity on the pollutant dyes with a more than 95% bioremoval for Direct Blue-15, Direct Blue-71, Crystal Violet, and Acid Blue-92. The maximum adsorption capacity of the prepared HNRs was 401 ± 11 mg per g of the carrier after 240 min of contact time with initial dyes' concentrations. Freundlich isotherm well fitted on the removal data compared with the Langmuir model due to the formation of a uniform monolayer of the dyes onto the prepared HNRs. For Direct Blue-15, Direct Blue-71, Crystal Violet, Acid Blue-92, and Acid Red-18, R2 values of pseudo-second-order kinetic were closer to 1 than that of first-order. The thermodynamic evaluations indicated that the removal of the dyes by the immobilized enzyme proceeded spontaneously and favorably (0 > ΔG°), albeit with endothermic characteristics (0 < ΔH°). Bioremoval efficiencies of 32%, 51%, 64%, and 72% were recorded when actual wastewater samples underwent treatment with 0.3 U mL−1, 0.6 U mL−1, 0.9 U mL−1and 1.2 ≤ U mL−1 of HNPs, respectively. Furthermore, the enzymatic removal process led to less toxic metabolites as confirmed using the bacterial growth inhibition test. Therefore, laccase@BiPO4•HNRs can be a worthy approach in dye removal from wastewater due to their distinct physicochemical and catalytic properties.

Synthesis of highly efficient ternary phase graphene/Bi/SnO2 photocatalyst for degradation of organic dye pollutants

In this work, graphene nanosheets (GNs) are prepared from graphite rods obtained from waste dry-cell batteries using the electrochemical exfoliation (ECE) method. Then GNs used as a matrix to modify tin oxide (SnO2) and Bismuth (Bi) nanoparticles to prepare a binary phase SnO2@G and ternary-phase Bi@SnO2@G nanocomposite materials by wet-chemical method and used as a photocatalysts for degradation of organic dye pollutants. XRD diffraction pattern clearly confirmed the presence of tetragonal crystal system of SnO2 which was maintaining its structure in SnO2@G and G/Bi/SnO2. The stretching and bending vibrations of the functional groups were analyzed using FTIR analysis. FESEM images demonstrated the surface morphology and the texture of the as synthesized sample. Raman Spectroscopic investigation was carried out to confirm the in-plane blending of SnO2 and graphene inside the composite matrix. The as-prepared ternary-phase Bi@SnO2@G-based photocatalyst showed high degradation efficiency of 99.6% and 94.5% for direct blue (DB) and methyl blue (MB) dyes, respectively, under visible light irradiation by (i) minimizing the hole and electron recombination, (ii) providing a high surface area, and (iii) reducing the band gap energy. This study provides an effective, low-cost, and smart approach for producing GNs on a wide scale from battery waste along with nanohybrid composites with high photocatalytic efficiency.

A novel application of HKUST-1 for textile dyes removal in single and binary solutions: Experimental investigation combined with physical modelling

The paper analyzes the single and binary adsorption of textile water pollutants, namely Direct Blue 1 (DB-1) and Direct Yellow-4 (DY-4) dyes, on HKUST-1 at 30 – 50 °C and pH 6.8. Experimental adsorption data indicated that the DB-1 and DY-4 adsorption capacities using this MOF decreased from single to binary systems confirming the presence of a competition effect between these dye molecules on the HKUST-1 adsorbent site. This antagonistic adsorption effect was exothermic. A theoretical approach based on the application of two enhanced adsorption models was utilized to understand the mechanisms for the adsorption of both dye molecules. This approach allowed the calculation of the saturation adsorption capacities for these pollutants in single and binary systems, which followed the next sequence: Qm (DB-1/HKUST-1) > Qm (DY-4/HKUST-1) and Qmb (DB-1 (DB-1 + DY-4)/HKUST-1) > Qmb (DY-4 (DB-1 + DY-4)/HKUST-1). The binary adsorption of these dyes occurred via the presence of an antagonistic effect that reduced the MOF removal performance. HKUST-1 showed better adsorption performance to remove DB-1 dye. The adsorption orientations of DB-1 and DY-4 on HKUST-1 surface were discussed at different temperatures. The models determined the adsorption energies describing the interactions between both dyes and HKUST-1 surface, with range values from 17 to 21 kJ/mol, 12 to 16.5 kJ/mol in single and binary systems respectively. These calculations indicated that physical interactions may trigger the removal of these water pollutants. Overall, this work reports a cutting-edge application of HKUST-1 as adsorbent to remove toxic pollutants such as dye molecules from water.

Production of surfactant-modified banana peel biosorbents applied to treatment and decolorization of effluents

In this study, banana peels (BP) were pretreated under different conditions and modified with surfactants cetyltrimethylammonium bromide (CTAB), dodecyl trimethylammonium bromide (DTAB), or sodium dodecyl sulfate (SDS). The biosorbents were used for the removal of the anionic Direct Blue 86 (DB86) from synthetic solutions as well as for the treatment of a textile effluent. The biosorbents were characterized by Fourier Transform Infrared Spectroscopy (FTIR), contact angle measurements, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and point of zero charge (pHPZC). The results showed that the pretreatment using natural oxidation of BP showed better adsorbent performance than other pretreatments at pH 2. Treatment with SDS did not improve the sorption efficiency of the material. The biosorbents modified with DTAB (B-DTAB) and CTAB (B-CTAB) showed good performance with a maximum dye removal of 96.2% (at pH 2) and 91.7% (at pH 6), respectively, using 1.00 g L−1 of the biosorbents, constant stirring of 150 rpm for 60 min at 25 °C, and DB86 concentration of 10.0 mg L−1. The kinetics of B-DTAB and B-CTAB showed the best fit to the pseudo-first and pseudo-second-order models, respectively. The intraparticle diffusion model suggested that adsorption on B-CTAB may be guided by pore and film diffusion. Sips isotherm was found to be the best fit with theoretical maximum adsorption capacities from non-linear fit of 25.2 and 147 mg g−1, respectively, for B-DTAB and B-CTAB (1.00 g L−1 of the biosorbents, constant stirring of 150 rpm, 25 °C, and initial pH 6). Results suggest that mainly precipitation, hydrophobic interactions, and electrostatic attraction drives the sorption process. The treatment of the textile effluent using B-CTAB resulted in a reduction of 60.6% in color and 53.2% in effluent turbidity, demonstrating the potential of modified banana peels as promising biosorbents for environmental applications.

UiO-66 octahedrons for adsorptive removal of direct blue-6: process optimization, interaction mechanism, and phytotoxicity assessment.

The materials for water treatment have been evolving in multitude of dimensions, indicating the importance of water reuse and increasing level of water pollution around the globe. Among the various materials that are utilized in wastewater treatment, the material that has attracted the research community for the past decades is the metal organic framework (MOF). In this work one of the water stable and microporous MOF, UiO-66, and its aminated version has been employed to adsorb an anionic azo dye, direct blue-6 (DB-6), from the aqueous matrix. Performance of both the MOFs was compared to know the efficiency under varying solution conditions. The optimized parameters for DB-6 adsorption by UiO-66 was performed using response surface methodology. This numerical optimization was further extended with canonical and ridge analysis. Under optimal conditions, the materials were exhibiting a good adsorption capacity of 754.4mg/g. The materials were analyzed in terms of morphology, crystallinity, thermal stability, and surface area using instruments like X-ray diffraction, electron microscopy, thermogravimetric analysis, and BET surface area analysis. The mechanism of interaction between UiO-66 and DB-6 molecule was elucidated with the help of XPS analysis which helps to know the main interacting group of UiO-66. This study was concluded with a phytotoxicity analysis of DB-6 and the antioxidant system of Vigna radiata assessed using pre and post adsorbed water.

Efficient Photocatalytic degradation of direct blue 15 dye using samarium doped bismuth tungstate nanosheets: A sustainable approach towards wastewater treatment

The rare earth metal, samarium (Sm3+) doped bismuth tungstate (Bi2WO6) nanoparticles were prepared by a one-pot hydrothermal method. The powder X-ray diffraction (XRD) analysis confirmed the formation of Bi2WO6 with an orthorhombic crystal structure. The crystallite size of Bi2WO6 decreased from 20.73 to 9.25 nm as the Sm substitution in the W lattice increased. The vibrational modes of W–O, Bi–O, and Sm–O were identified in the range of 500–900 cm−1. The optical bandgap of Sm3+ doped Bi2WO6 nanoparticles increased from 2.86 to 2.95 eV with higher Sm doping levels. The surface morphology revealed the formation of flower-like sheets in the Sm3+ doped bismuth tungstate. The energy dispersive X-ray (EDX) spectrum of Sm3+ doped Bi2WO6 nanoparticles confirmed the presence of Sm, Bi, W, and O without any other impurities. The small peak detected at 1082.14 eV in the survey scan of Sm3+ doped Bi2WO6 nanoparticles belonged to Sm3d. In the photocatalytic degradation of direct blue 15 (DB15) under visible light irradiation, the efficiency of the nanoparticles increased with higher Sm3+ concentration. The obtained results demonstrated that the Sm–Bi2WO6 nanosheets could provide an effective and sustainable solution for treating the wastewater containing direct blue 15 dye.

UV/periodate and UV/chlorine for dye degradation and real wastewater treatment: a comparative study

Abstract The discharge of synthetic dyes into the environment poses a significant threat to both human health and the ecosystem, necessitating the treatment of contaminated water. To generate free radicals for the elimination of Direct Blue 71 (DB71) dye from aqueous solutions, periodate (PI) and chlorine (Cl2) have been employed. In this study, separate activation of PI and Cl2 was achieved using ultraviolet (UV) light. The impact of various operational parameters was investigated, resulting in the complete degradation of the dye within 12 min. The presence of ferrous and copper ions had a minor enhancing effect on the degradation rate in both systems. Scavenging experiments confirmed that HO• and IO3• were the primary agents responsible for DB71 degradation in the UV/PI system, while reactive chlorine radicals played a dominant role in the UV/Cl2 process. In terms of mineralization, application for real wastewater and energy efficiency, the UV/PI system exhibited slightly superior performance compared to the UV/Cl2 system.

Investigating the effects of polypropylene-TiO2 loading on the performance of polysulfone/polyetherimide ultrafiltration membranes for azo dye removal: Experimental and molecular dynamics simulation

This research paper delves into developing and analyzing advanced composite ultrafiltration (UF) membranes specifically tailored for water treatment and dye removal applications. The composite UF membranes were designed using a combination of polysulfone (PSF), polyetherimide (PEI), and polypropylene-80 wt% TiO2 (PPTiO2) to create the active layer, while a flat polyamide (PA) serves as the support material and is prepared via the spin/spray-coating method. Three different PPTiO2 contents were considered, including 5 wt% (M05), 10 wt% (M10), and 15 wt% (M15). The properties of these membranes were characterized using a range of techniques, including Fourier Transform Infrared (FT-IR), Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM), contact angle measurements, mechanical testing and zeta potential. Performance evaluation involved filtering Reactive Red 120 (RR120) and Direct Blue 6 (DB6) solutions through the prepared composite membranes at 5 bar and demonstrates that the optimized membrane M15 exhibited remarkable water permeability of 82.13 L.m−2.h−1 bar−1 and maximum dye rejections of 92.82 % and 97.07 % for DB6 and RR120 respectively. Furthermore, molecular dynamics (MD) simulations were conducted to analyze the thermal and structural properties of the membranes. The simulations reveal that increasing the content of PPTiO2 reduced membrane pore size, consequently limiting dye mobility and diffusion. This study is the first-of-its-kind to explore the effect of PPTiO2 content on the membrane (PSF/PEI) properties; the optimized composite UF membrane showcases exceptional water permeability and dye rejection performance, making it a promising candidate for water treatment and dye removal applications.

Schottky-junction plasmonic nanocomposite: A non-hazardous excellent visible light photocatalyst for industrial waste management

A bio-compatible nanocomposite “Ag/Ag doped TiO2” with UV–Visible-NIR light gathering quality was synthesized by solvothermal method, followed by green synthesis method. Insertion of Ag+ ions into Ti2+ lattice sites in Ag doped TiO2 alters the n-type TiO2 semiconductor to p-type. Nanostructured doped TiO2 suffers high charge recombination loss in presence of trapped states, resulting 35 % photocatalytic efficiency. Ag decoration on p-type Ag doped TiO2 forms a Schottky barrier at metal-semiconductor junction, which reduces charge recombination loss by separating the photogenerated electron-hole (e-h) in two materials of the nanocomposite. These photogenerated charges create oxide and hydroxide super radicals in the aqueous system of photocatalyst, ensuing 80% degradation of SO dye under 50 min white light illumination. The nanocomposite also demonstrated good performance in degradation of industrial dyes like 50% Mordant Orange (MO) and 15% Direct Blue (DB) under 50 min white light irradiation. DFT analysis of the heterosystems supports absorptivity tuning of experimentally obtained nanocomposite. Moreover, the nanocomposite proved its non-toxicity to human cells, as it reveals <20% cell death with maximum dose (250 µg/ml) of the nanocomposite in cytotoxicity test. Hence, proper designing and synthesizing the nanocomposite explored an eco-friendly solar photocatalyst for industrial waste management.

Efficient biocatalytic removal and algal detoxification of Direct Blue-15 by the hierarchically structured, high-performance, and recyclable laccase@yttrium phosphate hybrid nanostructures.

From the environmental point of view, azo dye industrial effluent is a major public health concern due to its toxic, carcinogenic, and teratogenic characteristics. On the other hand, using enzyme-based technologies offers a promising systematic and controllable method for removing synthetic dyes from wastewater. In the present study, yttrium (Y3+) phosphate was applied for the synthesis of hybrid nanoparticles (HNPs) consisting of laccase as the green catalyst. When the association of HNPs was fixed by glutaraldehyde (GA), three-dimensional cubic structures with the regular arrangement were provided. GA increased the reusability of the fabricated hybrid nanostructures (HNSs) up to 32 successive cycles. About 85% of Direct Blue-15 was removed after a 4 h-treatment using laccase@YPO4•HNPs and laccase@GA@YPO4•HNSs. The azo dye removal data were well-fitted with a pseudo-second-order model for both types of the prepared HNSs. For the model freshwater green alga Raphidocelis subcapitata, the half maximal effective concentration (EC50) of the dye decreased 10- and 100-fold after the removal with laccase@YPO4•HNPs and laccase@GA@YPO4•HNSs, respectively. GA-treated HNSs (250 U L-1) inhibited the biofilm formation by approximately 78%, 82%, and 79% for Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, respectively. Thus, the fabricated laccase@GA@YPO4•HNSs could be presented as a novel, efficient, and recyclable heterogeneous biocatalyst for wastewater treatment and clean-up.

Fabrication of a novel bio-polymer adsorbent with high adsorptive capacity towards organic dyes

A novel adsorbent, CMC-T-CH, was fabricated by crosslinking of carboxymethyl cellulose (CMC) and chitosan (CH) with triethylenetetramine. The adsorbent's efficacy in removing the hazardous dyes, Direct blue (DB) and Congo red (CR), was investigated. Different physical, chemical, and biological methods have been employed to eliminate CR and DB dyes from aqueous solution, and adsorption has shown potential in eradicating these dyes effectively. Various characterization methods were employed to investigate the physicochemical characteristics of CMC-T-CH. The removal process was performed at optimized conditions of pH 6 for CR and pH 5 for DB at the temperature of 35 °C, resulting in maximum removal efficiencies of 99 % and 98.33 % for CR and DB, respectively. Langmuir isotherm and pseudo-second-order kinetic mathematical models were utilised to analysed the interaction of adsorbate and adsorbent during the removal process. The maximum theoretical adsorptive capacities of 519.53 and 534.25 mg/g were achieved for CR and DB removal, respectively. The regeneration study revealed that the dye-loaded CMC-T-CH could be reused several times. The phytotoxicity assay showed that the germination of Vigna mungo seeds improved after the removal treatment, thus confirming the potential of CMC-T-CH in the elimination of CR and DB.

Compact tubular carbon-based membrane bioreactors for the anaerobic decolorization of azo dyes

This research investigates a highly efficient compact tubular ceramic-supported carbon-based membrane reactor integrated with anaerobic biodegradation to decolorize the azo dyes. Two carbon-based membranes, produced using Matrimid 5218 polyimide and graphene oxide solutions, are evaluated for the comparative color removal of three structurally different azo dyes, Acid Orange 7 (AO7), Reactive Black 5 (RB5), and Direct Blue 71 (DB71). Based on FESEM microscopic images, the average pore size of the tubular ceramic-supported carbonized membrane (TCSCM) was approximately 25 nm, while for the tubular ceramic-supported graphene oxide membrane (TCSGOM), it was 12 nm. Additionally, TCSCM had a thinner layer at only 1.10 µm, while TCSGOM was slightly thicker at 2.11 µm. These features influenced the permeate flux of the membrane, in which the TCSGOM exhibited lower permeate flux (18.2 L·m−2·h−1) than the TCSCM (45.6 L·m−2·h−1). However, the anaerobic decolorization results indicated that the TCSGOM bioreactor (B-TCSGOM) was more efficient and effective at removing color from all dye solutions than the TCSCM bioreactor (B-TCSCM) over a wide range of feed concentrations. In both reactors, the highest decolorization was achieved at low feed concentration (50 mg·L−1), and removal was 94 % for AO7, 90 % for RB5, and 88 % for DB71 in B-TCSGOM, whereas 88 %, 85 %, and 69 %, respectively, in B-TCSCM. These suggest that the robust conductive nanoporous surface of B-TCSGOM makes it more effective at removing different azo dye solutions from wastewater.

Investigation of the effect of supporting electrolyte type and pH parameters on electrooxidation color removal from Direct Blue 86

In this study, color removal and electrical consumption from Direct Blue 86 (DB86) dyestuff, commonly used in the textile industry, were investigated using the electrooxidation method. A jacketed glass reactor with a volume of 2000 mL was preferred for the electrooxidation process. Five anode and five cathode electrodes with dimensions of 70 x 100 mm were used. Ti/IrO2/RuO2 was chosen as the anode material, and stainless steel (plate type) electrodes were preferred as the cathode. The effects of the supporting electrolyte type and pH parameters on color removal were investigated. NaCl, KCl, NaNO3, and Na2SO4 were used as supporting electrolytes. Experiments were conducted at pH 3, 5, 7, 9, and 11 with an applied current density of 0.325 mA/cm2. The results showed that KCl as the supporting electrolyte provided the highest color removal efficiency with 99.76%. The optimum pH value was found to be pH 9. The minimum energy consumption was calculated as 3.39 kW-h/m3 for pH 11. Based on the obtained results, it was concluded that the electrooxidation method is effective in color removal and can be preferred due to its ease of use and process control advantages.