Dye-containing Effluents Research Articles

Green synthesis of NiFe2O4 nanoparticles using Hyphaene thebaica: A facile route towards magnetic and photocatalytic application

Wastewaters from textile industries contribute to significant volumes of colored and hazardous material pollution. Photocatalytic degradation offers a method to reduce organic pollutants, such as dye-containing effluents effectively. Nickel Ferrite (NiFe2O4) receives the most attention in spinel ferrites since it has diverse applications in catalysis, sensor technology, spintronics, magnetocaloric refrigeration, high-density data storage devices, etc. We performed the green synthesis of NiFe2O4 nanoparticles by fruit extract of a gingerbread tree (Hyphaene thebaica). We characterized it with Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), and Raman spectroscopy. The XRD indicates the inverse-spinel structure of the F3dm space group with crystallite size measured as 30 nm. SEM and TEM revealed the spheroidal structure of NiFe2O4 NPs. The green synthesized NiFe2O4 has tetrahedral and octahedral stretching vibrations of Ni–O and Fe–O, as suggested by FTIR. Doublet-like peak behavior in the Raman spectrum indicated the presence of a mixed spinel structure. We studied magnetic behavior in two different modes, and magnetization measurements showed a soft ferromagnetic behavior with a saturation magnetization of 1.527 emu g−1. For photocatalytic potential, the degradation efficiency was 97 % after 90 min at adding 1 g/L of NiFe2O4 nano-catalyst, which shows the high catalytic activity of NiFe2O4 NPs under visible light conditions.

Preparation of Au-MoS2 photocatalyst with a green synthesis method and its application in water contaminant degradation

In the current research, a successful and fast synthesis of gold nanoparticles (AuNPs) by utilizing the leaf extract of Eryngium planum is reported. In order to analyze the influential synthesis parameters, the Plackett-Burman (PB) design was utilized, while the response surface methodology (RSM) was employed for optimization purposes. Furthermore, the achieved AuNPs were applied in the production of the Au-MoS2 nanocomposite. The efficiency of the visible-light photocatalyst was examined in the photocatalytic decolorization of the refractory azo dye, Acid Blue 113 (AB113). A high dye removal efficiency (94%) was observed under the optimal conditions of pH 7.6 using 15.5 mg of Au-MoS2, and 14 min. These results proved that the fabricated Au-MoS2 photocatalyst using biogenic AuNPs was more efficient than pure MoS2 and could be used as a promising catalyst for the degradation of dye-containing effluents.

Oxalic Acid-Assisted Photo-Fenton Catalysis Using Magnetic Fe3O4 Nanoparticles for Complete Removal of Textile Dye

Textile industry effluents contain several hazardous substances, such as dye-containing effluents, which pose environmental and aesthetic challenges. Presently, the microbial-based remediation process is in use. This study investigated the application of ferrous–ferric oxide (Fe3O4) nanoparticles, a readily formulated nanoadsorbent, to remove scattered dye molecules from industrial effluents. The ferrous–ferric oxide nanoparticles were prepared using a chemical co-precipitation method. The nanoparticles had 26.93 emu g−1 magnetization, with sizes smaller than 20 nm, and possessed a highly purified cubic spinel crystallite structure. The catalytic activity of the iron oxide depended on the dose, photocatalytic enhancer, i.e., H2O2 level, pH of the reaction medium, and dye concentration. We optimized the Fenton-like reaction to work best using 1.0 g/L of ferrous–ferric oxide nanoparticles, 60 mM oxalic acid at pH 7.0, and 60 ppm of dye. Iron oxides act as photocatalysts, and oxalic acid generates electron–hole pairs. Consequently, higher amounts of super-radicals cause the rapid degradation of dye and pseudo-first-order reactions. Liquid chromatography–mass spectrometry (LC-MS) analysis revealed the ferrous–ferric oxide nanoparticles decolorized and destroyed Disperse Red 277 in 180 min under visible light. Hence, complete demineralization is observed using a photo-Fenton-like reaction within 3 h under visible light. These high-capacity, easy-to-separate next-generation adsorption systems are suggested to be suitable for industrial-scale use. Ferrous–ferric oxide nanoparticles with increased adsorption and magnetic properties could be utilized to clean environmental pollution.

Cloning and characterization of FMN-dependent azoreductases from textile industry effluent identified through metagenomic sequencing

ABSTRACT Azo dyes, when released untreated in the environment, cause detrimental effects on flora and fauna. Azoreductases are enzymes capable of cleaving commercially used azo dyes, sometimes in less toxic by-products which can be further degraded via synergistic microbial cometabolism. In this study, azoreductases encoded by FMN1 and FMN2 genes were screened from metagenome shotgun sequences generated from the samples of textile dye industries’ effluents, cloned, expressed, and evaluated for their azo dye decolorization efficacy. At pH 7 and 45°C temperature, both recombinant enzymes FMN1 and FMN2 were able to decolorize methyl red at 20 and 100 ppm concentrations, respectively. FMN2 was found to be more efficient in decolorization/degradation of methyl red than FMN1. This study offers valuable insights into the possible application of azoreductases to reduce the environmental damage caused by azo dyes, with the hope of contributing to sustainable and eco-friendly practices for the environment management. This enzymatic approach offers a promising solution for the bioremediation of textile industrial effluents. However, the study acknowledges the need for further process optimization to enhance the efficacy of these enzymes in large-scale applications. Implications: The study underscores the environmental hazards associated with untreated release of azo dyes into the environment and emphasizes the potential of azoreductases, specifically those encoded by FMN1 and FMN2 genes, to mitigate the detrimental effects. The study emphasizes the ongoing commitment to refining and advancing the enzymatic approach for the bioremediation of azo dye-containing effluents, marking a positive stride toward more sustainable industrial practices.

Evaluation of the design of anaerobic-aerobic systems for treating azo dye-containing effluents

Evaluation of the design of anaerobic-aerobic systems for treating azo dye-containing effluents

A Short Review on Dye-Wastewater Valorization Using Up-Flow Anaerobic Sludge Blanket Reactors

Dye-containing effluent generated in textile industries is polluting and complex wastewater. It should be managed adequately before its final destination. The up-flow anaerobic blanket (UASB) reactor application is an ecofriendly and cost-competitive treatment. The present study briefly reviews the UASB application for dye-containing wastewater valorization. Bioenergy and clean-water production potential during dye-containing wastewater treatment are emphasized to promote resource recovery in textile industries. Hydraulic retention time (HRT), organic loading rate (OLR), pH, temperature, and hydraulic mixing influence sludge granulation, microbial activity, and dye removal. HRT and OLR ranges of 6–24 h and 1–12 kg m−3 d−1 of chemical oxygen demand (COD) at a mesophilic temperature (30–40 °C) are recommended for efficient treatment. In these conditions, efficiencies of color and COD of 50–97% and 60–90% are reported in bench-scale UASB studies. Complex dye structures can hinder biomineralization. Pretreatment may be necessary to reduce dye concentration. Carbon-source and redox mediators are added to the UASB reactor to expedite kinetic reactions. A biogas yield of 1.48–2.70 L d−1 in UASB, which treats dye-containing effluents, is documented. Cotreatment of dye wastewater and locally available substrate could increase biogas productivity in UASB reactors. Organic waste generated in the textile industry, such as dye sludge, cotton, and starch, is recommended to make cotreatment cost competitive. Bioenergy production and water reuse allow environmental and economic benefits. Studies on combined systems integrating UASB and membrane processes, such as ultrafiltration and nanofiltration, for the production of reusable water and pretreatment of wastewater and sludge for improvements in biogas production might realize the complete potential for resource recovery of UASB technology. UASB bioenergy usage for integrated treatment trains can reduce operating costs and assist process sustainability in the textile industry.

The application of Rumex abyssinicus based activated carbon for Brilliant Blue Reactive dye adsorption from aqueous solution

The environmental pollution and human health impacts associated with the discharge of massive dye-containing effluents necessitate a search for cost-effective treatment technology. Therefore, this research work is conducted with the objective of investigating the potential of Rumex abyssinicus-derived activated carbon (RAAC) for the adsorption of Brilliant Blue Reactive (BBR) dye from aqueous solutions. Chemical activation with H3PO4 followed by pyrolysis was used to prepare the adsorbent. Characterization of the developed adsorbent was done using proximate analysis, pH point of zero charge (pHpzc), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), Brunauer, Emmett, and Teller (BET), and X-ray diffraction (XRD). The experimental design and the effect of independent variables including pH (2, 6, and 10), initial dye concentration (50, 100, and 150 mg/L), adsorbent dosage (0.05, 0.1, and 0.15 g/100 mL), and contact time (20, 50, and 80 min) were optimized using the response surface methodology (RSM) coupled with Box Behnken design (BBD). The analysis results revealed the exitance of high specific surface area of 524 m2/g, morphological cracks, and the presence of multiple functional groups like –OH, C=C, alkene, and amorphous structure. Maximum removal efficiency of 99.98% was attained at optimum working conditions of pH 2, contact time of 50 min, dye concentration of 100 mg/L, and adsorbent dosage of 0.15 mg/100 mL, reducing the pollutant concentration from 100 to 0.02 mg/L. Evaluation of the experimental data was done using Langmuir, Freundlich, Temkin, and Sips isotherm models, in which the Langmuir model was found to be the best fit with the experimental data at R2 0.986. This shows that the adsorbent surface is homogeneous and mono-layered. Furthermore, the kinetic study confirmed that the pseudo second-order model best describes the experimental data with R2 = 0.999. In general, the research work showed that the low cost, environmental friendliness and high adsorption capabilities of the activated carbon derived from Rumex abyssinicus could be taken as an effective nt for the removal of BBR dye from aqueous solutions.

Effects of malachite green on biochemistry and photosystem II photochemistry of Eichhornia crassipes.

Malachite green (MG) is a common synthetic dye that raises environmental concerns. This study reveals that MG has inhibitory effects on the biochemistry and physiology of Eichhornia crassipes . Effects of different concentrations of MG on ROS-scavenging enzymes, α-amylase, proline, chlorophyll pigments, and various photosynthetic parameters of E. crassipes were investigated. Chlorophyll fluorescence analysis coupled with the JIP test showed the inhibitory effects of MG on biochemistry and photosynthetic potential depended on concentration and time. Up to 2days of MG exposure, α-amylase and proline were upregulated with increasing MG concentration. When exposure time and concentration increased, all the parameters initially increased, then sharply declined. Chlorophyll content decreased with exposure time and concentration. Due to the slowing down of electron transport on the donor side brought on by MG exposure, P680+ builds up. According to an analysis of E. crassipes PSII activity, exposure to MG raises the proportion of inactive PSII reaction centres and active PSII centres. After increasing the exposure period (2, 4, and 6days) and MG concentration (50, 100, 150, and 200mgL-1 ), it decreased the absorption efficiency electron transport potential, maximal quantum yield of primary photochemistry, and the quantum yield of electron transport. These modifications led to a decline in the entire photosynthesis performance. The current research suggests that MG has detrimental effects on plants; therefore, the need for stringent regulations to prevent the release of dye-containing effluents into aquatic environments.

Tailoring the photocatalytic activity of novel magnetically separable ZnFe12O19-chitosan bionanocomposites: A green preparation, structural characterization and comparative study

Nowadays, the evaluation of nano-catalyts and photocatalytic technology for inactivating environmental pollution is identified as a priority. Although a series of semiconductor nanomaterials have been proven for this aim, suppression of charge carrier recombination and the absorption of solar light are still challenging. In this study, a novel visible-light-responsive bionanocomposite of ZnFe12O19-chitosan (ZF-C) is designed by a facile two-step approach. The utilization of two natural stabilizer and capping agents including turnip and carrot juices is developed to adopt nucleation and growth mechanism of as-fabricated crystals. In addition, benefiting from green templates, various quantities of these precursors show a strong impact on the construction of products in terms of structure and shape. The physic-chemical results confirmed creation of uniform ZF nanoparticles employing 20 mL of turnip juices. The band gap energy of ZF-C nanocomposites was found to be 1.55 eV, offering highly light absorption property in visible area. Moreover, the optimum photocatalyst had a specific surface area of 3.37 m2 g −1. This research encompasses the first insights of photocatalytic efficiencies of ZF and [ZF-Cx] (x: 5.0%, 10.0% and 15.0%) nanocomposites toward five toxic dyes such as methyl violet (MV), erythrosine (EY), methylene blue (MB), methyl orange (MO), and rhodamine B (RhB) under visible light. As a proof-of-concept, the nanocomposites with 10.0% of chitosan matrix could exhibit higher photocatalyst performance about 94.12% EY removal after 120 min, which is 1.15 times better than that of pristine ZF nanostructures. Based on active species trapping experiments, a possible photodegradation pathway of EY dye over the [ZF-C10] nanocomposites has been reported. These findings describes a revolutionary way for selecting [ZF-C10] nanostructure as eco-friendly and magnetically recyclable photocatalysts in dye-containing effluents.

Citric acid-functionalized Acacia pods as a robust biosorbent for decontamination of wastewater containing crystal violet dye: Experimental study combined with statistical optimization

This study reports the chemical modification of Acacia pods (AP) by citric acid and its application for crystal violet (CV) dye removal from water. The raw and modified AP (AP@CA) were characterized using scanning electron microscope, energy-dispersive X-ray spectrometer, Fourier-transform infrared spectrometer, X-ray diffractometer and N2 adsorption-desorption. The characterization findings confirm that the AP was successfully modified by citric acid with an increase in the surface area from 29.69 to 51.12 m2.g−1. The CV adsorption data reasonably agreed with pseudo-second-order kinetics and Langmuir isotherm models. The maximum uptake capacity of AP for CV dye increased from 267.67 to 300.92 mg.g−1 after citric acid modification. The CV adsorption mechanism mainly occurred through electrostatic forces, n-π interactions and H-bonds. The response surface methodology was employed to assess the effect of key parameters including pH (4.0–8.0), contact time (10–110 min) and absorbent dose (0.2–1.2 g.L−1) on the CV removal performance. The highest CV removal efficiency of 98.82% was obtained at pH 8, AP@CA dose 1 g.L−1 and contact time 90 min. The CV removal efficiency of AP@CA is still above 89.31% after five regeneration times. Overall, AP@CA material can be utilized as a promising reusable adsorbent for treating dye-containing effluents.

Azo Dyes Degradation Approaches and Challenges: An Overview

Dyes play a very important role in our daily lives. The dye industries started manufacturingdyes with natural sources and then turned towards synthetic ones. Among these dyes, about60% of the total dyes are azo dyes which are used in industries. They are mostly used as textiledyes because they are easy to synthesize, chemically stable and diverse in nature. Azo dyescome in about 3000 different variations and are employed in a variety of industries, includingthe textile, leather, paper, and pharmaceutical sectors. But sadly, the majority of azo dyes arepoisonous and mutagenic to all living things. The effluent coming from the textile sector musttherefore be removed and treated. The wastewater is often treated using a variety of physicaland chemical methods, however, these methods have been shown to be inefficient, expensive,produce insufficient amounts of sludge, and have limited effectiveness. So, in order to treatand decolorize dyes and dye-containing effluents without further harming the environment orendangering life forms, It has practically universal dye degradability is economical and hasalso eliminated a number of drawbacks of the physicochemical method. The properties andclassification of azo dyes, associated problems, biodegradation techniques, and possibilitiesare only a few of the subjects covered in this chapter’s examination of recent research,advancements, and the body of existing information on them. Biological processes havereceived special attention as a remedy for the current problems with azo dyes.

Homologous overexpression of azoreductase (azoA) in Enterococcus sp. L2 moderated growth and azo dye decolorization while gaining an oxidative and heavy metal stress resistance: A trade-off

Heavy metals as co-pollutants significantly restrict the efficiency of bioremediation of azo dye-containing effluents wherein bacterial survival is a prerequisite. An exposure to quinones and oxidative stress via H 2 O 2 could induce the azoreductase activity in Enterococcus sp. L2 which could link the AzoA to its stress management system. Therefore, we underpinned the physiological and stress tolerance features by homologous over-expression of the azoA gene in its native strain. AzoA overexpression increased 3.4 folds azoreductase specific activity and enhanced quinone reduction profile. AzoA overexpression in native strain led to a delay in the early log phase growth and reactive violet 5R decolorization while gaining an advantageous stress resistance towards oxidative and heavy metals such as copper and chromium. This was confirmed by the 32 folds higher survival upon exposure to 20 mM H 2 O 2 supported by H 2 DCFA staining. Additionally, the genetically modified strain significantly tolerated 3 mM Cu(II) and 0.3 mM Cr(VI) supporting the development of a robust azo dye bioremediation strain. • Azo dye, quinones and H 2 O 2 enhanced azoreductase activity of Enterococcus sp. L2. • Homologous cloning in strain L2 resulted in 3.4 folds over-expression of AzoA gene. • AzoA over-expression in strain L2 moderated growth and dye decolorization. • AzoA over-expression in strain L2 increased oxidative stress (H 2 O 2 ) resistance. • AzoA over-expression in strain L2 enhanced heavy metal (Cu 2+ and Cr 6+ ) tolerance.

Synthesis of magnetic nano-NiFe2O4 with the assistance of ultrasound and its application for photocatalytic degradation of Titan Yellow: Kinetic and isotherm studies

Textile industries wastewaters lead to the production of great volumes of color and hazardous material pollution. A photocatalytic degradation is an approach that provides the chance to reduce organic pollutants like dye-containing effluents. The main aim of the present study was to prepare mixed-metal-oxide of NiFe2O4 magnetic in the presence of octanoic acid using the co-precipitation technique as an efficient photocatalyst for photodegradation of Titan Yellow (TY) from an aqueous medium. Various methods, such as transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), and x-ray diffraction patterns were employed to characterize the prepared photocatalyst. The magnetic characterization of the synthesized photocatalyst was also evaluated utilizing a vibrating sample magnetometer (VSM). Photocatalytic properties of nanocatalyst for the photodegradation of TY from aqueous solution were assessed by studying influential parameters, such as concentration of the dye (10 mg/L), the temperature of the solution (40 °C), amount of catalyst (10 mg), time of irradiance of UV light (20 min), and solution pH = 5. The adsorption isotherms and kinetics models evaluations were demonstrated that the process of adsorption was well matched by Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacity was obtained at 19.193 mg/g by the Langmuir model. The results depicted that NiFe2O4 nanocatalyst has a satisfactory performance in photodegradation of dye pollutants under UV light.

Dynamic Sorption of Methylene Blue (MB) Dye in Continuous Column Using Bio-Sorbent (Ailanthus excelsa Roxb)

Industrial waste containing dye poses a threat to the ecosystem and human as well as aquatic life. Methylene blue (MB, a cationic dye) has been used in excess amounts in textile, pulp and paper, rubber, plastics, cosmetics, pharmaceutical, and food industries. MB dye released in water sources makes the water toxic in nature. So, to remove the dye from wastewater various methods (physical, chemical and biological) are adopted for treatment purposes. Among them, adsorption is found to be more economical and eco-friendlier in comparison to others. Various adsorbents reported have been the literature for the removal of MB dye such as wheat straw, rice husk, cashew nut shell, sawdust, wood, pine needles, green grass, eucalyptus bark, peanut shell, coconut shell, coir dust, etc. In this experimental study, Ailanthus excelsa Roxb. (AER) is utilised for the treatment of MB dye from the wastewater in continuous mode by varying the different parameters viz., bed height, flow rate, and the initial concentration of MB dye. Yoon-Nelson and Clark’s models have been applied to predict the break through curve and to find out the characteristic parameters of column suitable for process design. The study reported that Clark’s model was found to be fit for the breakthrough curve. The findings revealed that Ailanthus excelsa Roxb. has a high adsorption potential, and it could be used to treat dye-containing effluents.

Synthesis of Cu-doped MgO and its enhanced photocatalytic activity for the solar-driven degradation of disperse red F3BS with condition optimization

Abstract In the present study, Cu (2–12%) doped MgO was synthesized and characterized by SEM, XRD, EDX, and FTIR spectroscopy. The Cu concentration significantly affected the band gap and particle size, which ranged from 4.63 to 3.78 eV and from 27.2 to 79 nm, respectively. In addition, the photocatalytic activity (PCA) of Cu-doped MgO was monitored by the photocatalytic destruction of disperse red F3BS coralene dye, and four reaction variables such as dye concentration, catalyst dose, hydrogen peroxide concentration, and irradiation time, respectively, were optimized by response surface methodology (RSM). Dye degradation was significantly affected by these process variables, and a degradation rate of up to 93% was achieved under optimized conditions. The wastewater samples were also treated under optimized conditions and water quality variables, i.e., chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were significantly improved after treatment. Cu-doped MgO exhibited excellent PCA under the solar-light exposure for the degradation of disperse red F3BS dye, which can be employed for the treatment of dye-containing effluents.

Photocatalytic degradation of methyl blue in water using sawdust-derived cellulose nanocrystals-metal oxide nanocomposite

The increase in dye-containing effluents that are discharged into the environment and the need to remediate the water bodies from the adverse effect of these dye pollutants have motivated a lot of research work. In this study, ZnO and TiO2 heterojunction systems (MO) embedded in cellulose nanocrystals (CNC), derived from sawdust, are reported. The nanocomposites (CNC/MO) were subsequently used as photocatalyst for the degradation of methyl blue (MB). The nanocomposites were characterized using SEM/EDs, XRD, and the degradation of MB were determined by UV-vis spectrophotometer. The XRD analysis showed characteristic peaks of CNC and the metal oxide (MO) upon the nanocomposite formation. A reduction in the intensity of peak at 30°, attributed to the cellulose 1β phase of pristine CNC, was observed. The morphological evaluation revealed that the nanocomposite exhibited intertwined spherical and rod-like shape on the surface. The effects of some key operating parameters, such as initial pH, catalyst dosage, and initial dye concentration on the degradation of MB were investigated. Higher degradation percentage (98.52%) of MB was observed for the CNC/MO at optimum pH 6. The adopted kinetics models showed that MB degradation was well described by the pseudo-second order model. The application of this nanocomposites in real industrial sample will confirm its robustness.

Up-Flow Anaerobic Sludge Blanket Reactors in Dye Removal: Mechanisms, Influence Factors, and Performance

Society faces eco-environmental challenges when it comes to managing industrial wastewaters. In particular, textile effluents are one of the main threats to living being due to toxic dyes. Technologies used to remove dye compounds include physicochemical and membrane filtration processes. However, since current technologies have several limitations, including high investment and energy demand, researchers have investigated cheaper and eco-friendly alternatives. Among them, anaerobic processes have been an effective method to decolourise dye-containing effluents. In that direction, the up-flow anaerobic sludge blanket (UASB) technology stands out in terms of high cost-effectiveness. The authors reviewed the published literature on UASB reactors in dye compounds removal. Mechanisms, merits, demerits, and technical aspects of UASB reactors are introduced. Challenges and opportunities are discussed. The major points are 1) mechanisms of dye removal in UASB reactors comprise mainly dye adsorption onto sludge granules and azo bond cleavage (biodegradation), 2) dye structure and concentration, external organic carbon source, redox mediators, and bioreactor operating conditions play a key role in the treatment performance, 3) UASB technology exhibits high decolourisation rates. Removal efficiencies of chemical oxygen demand and colour lie within the range of 60–85% and 75–96%, respectively. However, anaerobic treatments may not be able to mineralise by-products of anaerobic metabolisms. Consequently, post-treatment of the anaerobically treated effluent is required, and 4) the energy production during the decolourisation process in UASB reactors is estimated at 22 kWh per m3 of treated wastewater. Bio-energy recovery can promote wastewater valorisation and decrease the economic burdens of dye-containing effluents treatment. Future studies should focus on optimising influence parameters of full-scale UASB reactors and biogas recovery from dye-containing wastewater treatment.

Evaluation of Dye decolourization Potential of Laccase Producing TrichodermaharzianumDBS-1 and TrichodermaviridaeDBS-2

Background: The presence of dye-containing effluents in water bodies and soil shows significant health risks to humans, plants, and animals. These adverse effects necessitate the search for safe, cost-effective, and environmentally friendly methods to remove dyes from these environments. This study aims to evaluate the dye decolourization potential of laccase-producing fungi, specifically Trichoderma harzianum DBS-1 and Trichoderma viridae DBS-2. Methods: Laccase-producing fungal isolates, T. harzianum DBS-1 and T. viridae DBS-2, were obtained from the laboratory at the Department of Microbiology, Ahmadu Bello University (ABU), Zaria, and stored on PDA slants. The isolates were screened for their ability to decolourize three dyes—Blue H3R, Yellow FG, and Red 3B—at concentrations of 50 ppm and 100 ppm. The fungi were inoculated into Malt Extract Broth containing each dye at the specified concentrations. Dye decolourization was assessed by measuring absorbance at 450 nm after 3, 6, and 9 days of incubation. Results: The results indicated that the fungal isolates could decolourize the dyes at varying rates. The highest decolourization was observed for Red 3B, with T. viridae DBS-2 achieving 71.32% decolourization at 50 ppm and 50.33% at 100 ppm after 9 days of incubation. Conversely, the lowest decolourization was recorded for Yellow FG by T. harzianum DBS-1, with 30.34% at 50 ppm and 20.87% at 100 ppm after 9 days. Blue H3R and Red 3B exhibited higher decolourization percentages compared to Yellow FG. Conclusion: The study demonstrates that laccase-producing isolates T. harzianum DBS-1 and T. viridae DBS-2 have significant potential for dye decolourization, particularly for Blue H3R and Red 3B dyes. These findings suggest that these fungal isolates could be employed as an effective, eco-friendly solution for the bioremediation of dye-contaminated environments.

Removal of dyes by immobilization of Trametes versicolor in a solid-state micro-fermentation system

A novel bioreactor system (low cost and easily scaled-up) is presented for dye decolorization applying filamentous fungi. In this two-phase bioreactor, dyes were decolorized at 28°C in a first phase by immobilized fungi in spherical cartridges prepared with a high-density plastic polyethylene mesh and filled with wheat bran as substrate for growth. In a second phase the capacity of the ligninolytic enzymes (laccase and Mn-peroxidase) present in the extracellular extracts from the solid residues was exploited for decolorization at 50°C. Each sphere behaved as a small-scale bioreactor for cell-culture. This system allowed the decoupling of growth (sterile condition) and decolorization (non-sterile condition) stages. The ability to decolorize the azo dye xylidine and the triphenylmethane Malachite Green by two Argentinean strains of Trametes versicolor was evaluated. The highest decolorization rates were displayed by T. versicolor BAFC 2234. When both dyes were applied together in the bioreactor, after a first phase (100min) 73.5% of Malachite Green and 40% of xylidine decolorization was attained, while at the end of the second phase (240min) a 97% and 52% decolorization was observed. Laccase activity was detected in the decolorized solution, but no Mn-peroxidase activity. The easy change of the cartridges allows the continuous use of the bioreactor in the non-sterile decolorization of dye-containing effluents.

Application of PVDF/HDTMA-modified clinoptilolite nanocomposite membranes in removal of reactive dye from aqueous solution

Nowadays, dye-containing effluents are one of the important environmental issues which attracted researcher attentions extensively. Among different methods, used for dye containing effluents treatment, membrane technology has been considered recently. In this study, neat polyvinylidene fluoride (PVDF) nanofiltration membrane and nanocomposite membranes containing clinoptilolite nanoparticles, modified with hexadecyltrimethylammonium bromide surfactants (PVDF/HDTMA-modified clinoptilolite), were fabricated by wet phase inversion method and their performance in reactive red 120 (RR120) separation from aqueous solution, was investigated. Morphology, surface roughness, functional groups, hydrophilicity and pore size of the fabricated membranes were characterized respectively by field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), contact angle measurement (CA), and gravimetric tests. The separation properties of the membranes were also determined by permeation and rejection experiments. Gravimetric test results showed that the average pore size decreased from 5.72 nm in neat PVDF membrane to 4.41 nm in the membrane containing 2.5 wt% HDTMA-modified clinoptilolite nanoparticles. Considering contact angle results of the neat PVDF membrane (CA = 77.5°) and nanocomposite membrane containing 2.5% nanoparticles (CA = 63.7°) it was found that hydrophilicity of the nanocomposite membranes increase as HDTMA-modified clinoptilolite nanoparticles content increases in the polymer matrix. Permeation test results showed that 98.5% of RR120 can be separated by using a nanocomposite membranes containing 2.5 wt% HDTMA-modified clinoptilolite nanoparticles while its flux can be recovered to 96%.