Biodecolorization of recalcitrant dye as the sole sourceof nutrition using Curvularia clavata NZ2 and decolorization ability of its crude enzymes

Ecofriendly Approach on the Removal of Reactive Orange 107 from Aqueous Solutions Using Cladophora Species as a Novel Biosorbent

The efficiency of Cladophora species for the removal of Reactive Orange 107 (RO107) from the aqueous solution was evaluated through batch adsorption studies by optimising various process parameters such as pH (3-8), dye concentration (100-500 mg/l), biosorbent concentration (100-500 mg/l), temperature (25-45 °C) and contact time (12-108 h). The results revealed that the optimum conditions for RO107 decolourisation (87%) was found on 72 h of incubation with 100 mg/l dye concentration amended with 200 mg/l biosorbent at pH 6 at 25 °C. The mechanism of dye adsorption was evaluated using isotherms, kinetics and thermodynamic models. The experimental data fitted well with Langmuir isotherm and pseudo-second-order kinetic models. Thermodynamic studies revealed that the adsorption process was endothermic, spontaneous and feasible in nature. Recovery of RO107 from the Cladophora sp. was maximum when 0.1 M HNO3 was used as an eluent. UV-Visible, FT-IR and SEM analyses reveal the interaction between the biosorbent-adsorbate and confirm the process of decolourisation by Cladophora sp. In order to evaluate the nature of the untreated and treated dye solutions, toxicological studies were conducted and the results revealed that the treated dye solution was non- toxic as compared with untreated dye solution. The results of the docking study proved that there was a substantial binding energy between RO107 and the protein (Cytochrome C6) of Cladophora sp. Hence, Cladophora sp. proves to be a promising biosorbent to decolourise RO107 and its potential can be explored in the textile sectors.

Eco-friendly oxidation of a reactive textile dye by CaO2: effects of specific independent parameters

Textile wastewater containing dyes poses significant risks to the environment. Advanced oxidation processes (AOPs) effectively eliminate dyes by converting them into harmless substances. However, AOPs have drawbacks such as sludge formation, metal toxicity, and high cost. As an alternative to AOPs, calcium peroxide (CaO2) offers an eco-friendly and potent oxidant for dye removal. Unlike certain AOPs that generate sludge, CaO2 can be directly employed without resulting in sludge formation. This study examines the use of CaO2 for oxidizing Reactive Black 5 (RB5) in textile wastewater without any activator. Various independent factors-pH, CaO2 dosage, temperature, and certain anions-were investigated for their influence on the oxidation process. The effects of these factors on dye oxidation were analyzed using the Multiple Linear Regression Method (MLR). CaO2 dosage was determined to be the most influential parameter for RB5 oxidation, while the optimal pH for oxidation with CaO2 was found to be 10. The study determined that 0.5 g of CaO2 achieved approximately 99% efficiency in oxidizing 100 mg/L of RB5. Additionally, the study revealed that the oxidation process is endothermic, with an activation energy (Ea) and standard enthalpy (ΔH°) for RB5 oxidation by CaO2 determined as 31.135 kJ mol-1 and 110.4 kJ mol-1, respectively. The presence of anions decreased RB5 oxidation, with decreasing effectiveness observed in the order of PO43-, SO42-, HCO3-, Cl-, CO32-, and NO3-. Overall, this research highlights CaO2 as an effective, easy-to-use, eco-friendly, and cost-efficient method for removing RB5 from textile wastewater.

Removal of the Basic and Diazo Dyes from Aqueous Solution by the Frustules of Halamphora cf. salinicola (Bacillariophyta)

Industrial wastes with hazardous dyes serve as a major source of water pollution, which is considered to have an enormous impact on public health. In this study, an eco-friendly adsorbent, the porous siliceous frustules extracted from the diatom species Halamphora cf. salinicola, grown under laboratory conditions, has been identified. The porous architecture and negative surface charge under a pH of 7, provided by the various functional groups via Si-O, N-H, and O-H on these surfaces, revealed by SEM, the N₂ adsorption/desorption isotherm, Zeta-potential measurement, and ATR-FTIR, respectively, made the frustules an efficient mean of removal of the diazo and basic dyes from the aqueous solutions, 74.9%, 94.02%, and 99.81% against Congo Red (CR), Crystal Violet (CV), and Malachite Green (MG), respectively. The maximum adsorption capacities were calculated from isotherms, as follows: 13.04 mg g^-1, 41.97 mg g^-1, and 33.19 mg g^-1 against CR, CV, and MG, respectively. Kinetic and isotherm models showed a higher correlation to Pore diffusion and Sips models for CR, and Pseudo-Second Order and Freundlich models for CV and MG. Therefore, the cleaned frustules of the thermal spring-originated diatom strain Halamphora cf. salinicola could be used as a novel adsorbent of a biological origin against anionic and basic dyes.

Secondary bond interface assembly of polyethyleneimine on zein microparticles for rapid adsorption of Reactive Black 5

Textile dye wastewater has the characteristics of high concentration, complex composition and changeable color degree and pH, which is difficult to be effectively and completely treated, and easy to cause environmental pollution. Here, a strategy of secondary bond interface assembly of polyethyleneimine on zein microparticles (PEI) (PEI@zein) was constructed to achieve rapid and efficient removal of Reactive Black 5 (RB5), which is one of the most widely used reactive dyes in the textile industry. Structural analysis indicated that the as-prepared PEI layer immobilized on zein microparticles was constructed based on the interface assembly dominated by hydrophobic interactions and electrostatic attraction between PEI molecules and zein chains. The novel interface showed excellent absorption performance for RB5 with an absorption capacity of 631.0 mg·g^-1, rapid adsorption in 2 min, wide pH range of 4-10. Mechanism analysis suggested the effective adsorption of RB5 by PEI@zein microparticles was mainly attributed to secondary bond interface such as electrostatic interaction and hydrogen bond between RB5 and PEI immobilized on the surface of zein microparticles. Moreover, due to the presence of secondary bond interface, RB5 adsorbed on microparticles can be easily desorbed by using 0.01 M NaOH. Therefore, the strategy of secondary bond interface assembly with polyethyleneimine on zein microparticles has high potential for practical application in the treatment of dye-containing wastewater.

Genotoxicity and cytotoxicity of textile production effluents, before and after Bacillus subitilis bioremediation, in Astyanax lacustris (Pisces, Characidae)

Textile effluents may be highly toxic and mutagenic. Monitoring studies are important for sustaining the aquatic ecosystems contaminated by these materials, which can cause damage to organisms and loss of biodiversity. We have evaluated the cyto- and genotoxicity of textile effluents on erythrocytes of Astyanax lacustris, before and after bioremediation by Bacillus subitilis treatment. We tested 60 fish (five treatment conditions, four fish per condition, in triplicate). Fish were exposed to contaminants for 7 days. The assays used were biomarker analysis, the micronucleus (MN) test, analysis of cellular morphological changes (CMC), and the comet assay. All concentrations of effluent tested, and the bioremediated effluent, showed damage significantly different from the controls. We conclude that water pollution assessment can be accomplished with these biomarkers. Biodegradation of the textile effluent was only partial, indicating the need for more thorough bioremediation to effect complete neutralization of toxicity.

Performance of Meyerozyma caribbica as a novel manganese peroxidase-producing yeast inhabiting wood-feeding termite gut symbionts for azo dye decolorization and detoxification

For hazardous toxic pollutants such as textile wastewater and azo dyes, microbial-based and peroxidase-assisted remediation represents a highly promising and environmentally friendly alternative. Under this scope, gut symbionts of the wood-feeding termites Coptotermes formosanus and Reticulitermes chinenesis were used for the screening of manganese peroxidase (MnP) producing yeasts intended for decolorization and detoxification of textile azo dyes, such as Acid Orange 7 (AO7). To this end, nine out of 38 yeast isolates exhibited high levels of extracellular MnP activity ranging from 23 to 27 U/mL. The isolate PPY-27, which had the highest MnP activity, was able to decolorize various azo dyes with an efficiency ranging from 87.2 to 98.8%. This isolate, which represents the molecularly identified species Meyerozyma caribbica, was successfully characterized in terms of morphological and physiological traits, as well as enzymatic activities. Almost complete decolorization was achieved by the MnP-producing M. caribbica strain SSA1654 after 6 h of incubation with 50 mg/L of the sulfonated azo dye AO7 at 28 °C with an agitation speed of 150 rpm. The maximum decolorization efficiency of AO7 reached 93.8% at 400 mg/L. The decolorization of AO7 was confirmed by Fourier transform infrared (FTIR) and UV-Vis spectral analysis. High performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) were used to identify AO7 decomposition intermediates. Based on UV-Vis spectra, FTIR, HPLC, and GC-MS analyses, a plausible AO7 biodegradation mechanism pathway was explored, showing azo bond (-N=N-) cleavage and toxic aromatic amines mineralization CO₂ and H₂O. Microtox® and phytotoxicity assays confirmed that the AO7 metabolites produced by the strain SSA1654 were almost non-toxic compared to the original sulfonated azo dye.

Biological remediation technologies for dyes and heavy metals in wastewater treatment: New insight

The pollution of the environment caused by dyes and heavy metals emitted by industries has become a worldwide problem. The development of efficient, environmentally acceptable, and cost-effective methods of wastewater treatment containing dyes and heavy metals is critical. Biologically based techniques for treating effluents are fascinating since they provide several benefits over standard treatment methods. This review assesses the most recent developments in the use of biological based techniques to remove dyes and heavy metals from wastewater. The remediation of dyes and heavy metals by diverse microorganisms such as algae, bacteria, fungi and enzymes are depicted in detail. Ongoing biological method's advances, scientific prospects, problems, and the future prognosis are all highlighted. This review is useful for gaining a better integrated view of biological based wastewater treatment and for speeding future research on the function of biological methods in water purification applications.

Removal of a reactive dye from simulated textile wastewater by environmentally friendly oxidant calcium peroxide

In the present study, calcium peroxide (CaO2) was used separately for potential application as an environmentally friendly and low-cost oxidant for the removal of a textile dye ‘Reactive Black 5’ (RB5) from simulated textile wastewater containing auxiliary chemicals of textile production. The specific morphology, elemental analysis, particle size distribution, specific surface area, identification of crystalline phases and surface functional groups of the synthesized CaO2 were investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), laser diffraction (LD), Brunaure–Emmett–Teller method (BET), X-ray diffraction (XRD) and Fourier transmission infrared (FTIR), respectively. X-ray Diffraction analysis confirmed the synthesized oxidant as CaO2 with the tetragonal crystalline structure. The signal corresponded to a bending vibration of O–Ca–O was detected in the fingerprint region of the FTIR spectroscopy. The effects of various independent parameters such as contact time, pH, initial RB5 concentration and CaO2 dosage on decolorization were investigated. The results of the study showed that pH, initial dye concentration and the CaO2 amounts have significant effects on removal of the RB5. The optimum pH was determined 7 for the removal of RB5 by CaO2. 2.0 g CaO2 was found to be sufficient for the removal of 300 mg/L RB5 with 96.93% removal efficiency. Also 82.8% chemical oxygen demand (COD) removal efficiency from simulated textile wastewater (STW) was obtained by 2.0 g CaO2. The results of the present study showed that the CaO2 can be used as an environmentally friendly and low-cost oxidant for effective removal of reactive textile dyes.

Magnetically stimulated azo dye biodegradation by a newly isolated osmo-tolerant Candida tropicalis A1 and transcriptomic responses

A recently isolated osmo-tolerant yeast Candida tropicalis A1, which could decolorize various azo dyes under high-salinity conditions, was systematically characterized in the present study. Stimulating dye-decolorization effectiveness and osmo-tolerance of the yeast by static magnetic field (SMF) was investigated and transcriptomic responses of the yeast to SMF was analyzed to propose possible mechanisms. The results demonstrated that the yeast A1 effectively decolorized (≥ 97.50% within 12 h) and detoxified (from high toxicity to low toxicity within 24 h) 70 mg/L Acid Red B (ARB) under the optimized conditions through a series of steps including naphthalene-amidine bond cleavage, reductive or oxidative deamination/desulfurization, open-loop of hydroxy-substituted naphthalene or benzene and TCA cycle. Moreover, dye decolorization performance and osmo-tolerance of the yeast A1 were further improved by 24.6 mT SMF. Genes encoding high-affinity hexose/glucose transporter proteins and NADH-ubiquinone oxidoreductase were up-regulated by 24.6 mT SMF, which might be responsible for the increase of dye decolorization. Significant up-regulation of glycerol-3-phosphate dehydrogenase and cell wall protein RHD3 suggested that osmo-tolerance was enhanced by 24.6 mT SMF through promoting production and intracellular accumulation of glycerol as compatible solute, as well as regulation of cell wall component. In conclusion, 24.6 mT SMF led to the up-regulation of related genes resulting in enhanced dye biodegradation efficiency and osmo-tolerance of the yeast A1.

Amino-Fe3O4-functionalized multi-layered graphene oxide as an ecofriendly and highly effective nanoscavenger of the reactive drimaren red

Amino-functionalized multilayer graphene oxide (Am-nGO) has been synthesized and applied to remove the reactive drimaren red (DR) from aqueous solutions. Infrared spectroscopy evidenced amine and amide presence by peaks at 1579 cm^-1 and a band between 3300 and 3500 cm^-1. Raman spectroscopy showed an increment in I_D/I_G ratio after amino-Fe₃O₄-functionalization of nGO from 1.05 to 1.20, referent to an increase in sp³ domain disorder. The isoelectric point of Am-nGO was pH 8.1. From kinetic study, the equilibrium was achieved within 90 min; moreover, pseudo-n-order model satisfactorily fitted to the experimental data. Kinetic constant (k_n) was 0.71 mg^1-n g^1-n min^-1 and modeled equilibrium sorption capacity (q_e) 219.17 mg g^-1. Equilibrium experiments showed monolayer adsorption capacity (q_m) of 219.75 mg g^-1, and BET model best fitted to the equilibrium data, indicating that the adsorption process happened with multiple layers formation. From sorption thermodynamics, the standard free energy of Gibbs and enthalpy were respectively - 31.91 kJ mol^-1 (at 298 K) and 66.43 kJ mol^-1. Such data evidence the spontaneous and chemical behavior of DR adsorption as a consequence of strong electron donor-receptor interactions between the dye and the nanosorbent. By phytotoxicity assessment, Am-nGO showed inexpressive inhibitory potential to American lettuce seeds in comparison with its precursor nGO and graphite nanoplatelets.

Decolorization of Acid Orange 7 by extreme-thermophilic mixed culture

Although a large amount of textile wastewater is discharged at high temperatures, azo dye reduction under extreme-thermophilic conditions by mixed cultures has gained little attention. In this study, Acid Orange 7 (AO7) was used as the model azo dye to demonstrate the decolorization ability of an extreme-thermophilic mixed culture. The results showed that a decolorization efficiency of over 90% was achieved for AO7. The neutral red (NR, 0.1 mM) could promote AO7 decolorization, in which the group of Cell + NR offered the highest decolorization rate of 1.568 1/h and t_1/2 was only 0.44 h, whereas after CuCl₂ addition, the decolorization rate (0.141 1/h) was lower and t_1/2 (4.92 h) was much longer. Thus, CuCl₂ notably inhibited this process. Caldanaerobacter (64.0%) and Pseudomonas (25.4%) were the main enriched bacteria, which were not reported to have the ability for dye decolorization. Therefore, this study extends the application of extreme-thermophilic biotechnology.

Toxicological Assessment and UV/TiO2-Based Induced Degradation Profile of Reactive Black 5 Dye

In this study, the toxicological and degradation profile of Reactive Black 5 (RB5) dye was evaluated using a UV/TiO2-based degradation system. Fourier transform infrared spectroscopy (FT-IR), thin layer chromatography (TLC), high-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography coupled with mass spectrometry (UPLC-MS) techniques were used to evaluate the degradation level of RB5. The UV-Vis spectral analysis revealed the disappearance of peak intensity at 599 nm (λmax). The FT-IR spectrum of UV/TiO2 treated dye sample manifest appearance of new peaks mainly because of the degraded product and/or disappearance of some characteristics peaks which were present in the untreated spectrum. The HPLC profile verified the RB5 degradation subject to the formation of metabolites at different retention times. A stable color removal higher than 96% with COD removal in the range of 74-82.3% was noted at all evaluated dye concentrations. The tentative degradation pathway of RB5 is proposed following a careful analysis of the intermediates identified by UPLC-MS. Toxicity profile of untreated and degraded dye samples was monitored using three types of human cell lines via MTT assay and acute toxicity testing with Artemia salina. In conclusion, the UV/TiO2-based degradation system could be effectively employed for the remediation of textile wastewater comprising a high concentration of reactive dyes.

Performance of a newly isolated salt-tolerant yeast strain Pichia occidentalis G1 for degrading and detoxifying azo dyes

A salt-tolerant yeast named G1 which could decolorize various azo dyes was recently isolated and identified as Pichia occidentalis. Systematic researches on characterization, degradation pathway, detoxification effects and enzymes analysis of this yeast were done. The results showed that the optimal metabolism and growth parameters for strain G1 were: 2.0gL^-1 glucose, 0.6gL^-1 ammonium sulfate, 0.08gL^-1 yeast extract, 30gL^-1 NaCl, 160rmin^-1, 30°C and pH 5.0. More than 98% of 50mgL^-1 Acid Red B (ARB) could be decolorized within 16h under the optimal conditions. Additionally, strain G1 degraded and obviously detoxified ARB through a possible pathway successively consisting of decolorization, deamination/desulfonation and TCA cycle processes. Moreover, NADH-DCIP reductase was estimated as the key reductase for decolorization and ligninases including lignin peroxidase, manganese peroxidase and laccase were important oxidoreductases for further degradation of decolorization intermediates.

Adsorptive amputation of hazardous azo dye Congo red from wastewater: a critical review

Increasing amount of dyes in an ecosystem has propelled the search of various methods for dye removal. Amongst all the methods, adsorption occupies a prominent place in dye removal. Keeping this in mind, many adsorbents used for the removal of hazardous anionic azo dye Congo red (CR) from aqueous medium were reviewed by the authors. The main objectives behind this review article are to assemble the information on scattered adsorbents and enlighten the wide range of potentially effective adsorbents for CR removal. Thus, CR sorption by various adsorbents such as activated carbon, non-conventional low-cost materials, nanomaterials, composites and nanocomposites are surveyed and critically reviewed as well as their sorption capacities are also compared. This review also explores the grey areas of the adsorption performance of various adsorbents with reference to the effects of pH, contact time, initial dye concentration and adsorbent dosage. The equilibrium adsorption isotherm, kinetic and thermodynamic data of different adsorbents used for CR removal were also analysed. It is evident from a literature survey of more than 290 published papers that nanoparticle and nanocomposite adsorbents have demonstrated outstanding adsorption capabilities for CR. Graphical abstract ᅟ.

Mutagenicity, cytotoxicity and phytotoxicity evaluation of biodegraded textile effluent by fungal ligninolytic enzymes

Colored effluents from the textile industry have led to severe environmental pollution, and this has emerged as a global issue. The feasibility of ligninolytic enzymes for the detoxification and degradation of textile wastewater was investigated. Ganoderma lucidum crude ligninolytic enzymes extract (MnP 717.7, LiP 576.3, and Laccase 323.2 IU/mL) was produced using solid-state culture using wheat bran as substrate. The biodegradation treatment efficiency was evaluated on the basis of degradation and detoxification of textile effluents. Standard bioassays were employed for mutagenicity, cytotoxicity and phytotoxicity evaluation before and after biodegradation. The degradation of Masood Textile, Kalash Textile, Khyber Textile and Sitara Textile effluents was achieved up to 87.29%, 80.17%, 77.31% and 69.04%, respectively. The biochemical oxygen demand, chemical oxygen demand, total suspended solids and total organic carbon were improved considerably as a result of biodegradation of textile effluents, which were beyond the permissible limits established by the National Environmental Quality Standards before treatment. The cytotoxicity (Allium cepa, hemolytic, Daphnia magna and brine shrimp), mutagenicity (Ames TA98 and TA100) and phytotoxicity (Triticum aestivum) tests revealed that biodegradation significantly (P < 0.05) detoxifies the toxic agents in wastewater. Results revealed that biodegradation could possibly be used for remediation of textile effluents. However, detoxification monitoring is crucial and should always be used to evaluate the bio-efficiency of a treatment technique.