New benzotriazoles generated during textile dyeing process: Synthesis, hazard, water occurrence and aquatic risk assessment

The natural anthraquinone dye emodin: Eco/genotoxicological characterization for aquatic organisms

Emodin is an anthraquinone secondary metabolite produced by several species of plants and fungi. Emodin is known for its pharmacological versatility, and, in the textile industry, for its good dyeing properties. However, its use in the textile industry can result in the formation and disposal of large volumes of wastewater. Emodin mutagenicity has been shown in bacteria and in human cells, but little is known about its possible toxic, genotoxic, or mutagenic effects in aquatic organisms. We have evaluated the eco/genotoxicity of emodin to aquatic organisms. Emodin was toxic to Daphnia similis (EC50 = 130 μg L-1) and zebrafish embryos (LC50 = 25 μg L-1). No toxicity was observed for Raphidocelis subcapitata, Ceriodaphnia dubia, or Parhyale hawaiensis. Additional biochemistry/molecular studies are needed to elucidate the toxic/mutagenic pathways of emodin in aquatic organisms. The PNEC value for emodin was 0.025 μg L-1. In addition to mutagenicity in the Salmonella/microsome assay, emodin was mutagenic in the micronucleus assay in the amphipod P. hawaiensis. Among the anthraquinone dyes tested to date, natural or synthetic, emodin was the most toxic to aquatic species.

Green synthesis of iron nanoparticles using mulberry leaf extract: characterization, identification of active biomolecules, and catalytic activity

The synthesis of iron-based nanoparticles (Fe NPs) using traditional preparation methods suffered from the disadvantages of high cost, environmental harm, and easy agglomeration. In this study, a novel eco-friendly method was proposed for the synthesis of iron nanomaterials (ML-Fe NPs): using antioxidant components extracted from mulberry leaf to reduce divalent iron (II). The preparation conditions of ML-Fe NPs were optimized by orthogonal tests. The prepared ML-Fe NPs exhibited an amorphous core-shell structure, displaying excellent dispersion and stability. During the synthesis process of ML-Fe NPs, the polyphenol molecules in mulberry leaf extract played a dominant role. A possible synthetic mechanism involving complexation, reduction, and encapsulation was proposed. Furthermore, the ML-Fe NPs were utilized to construct an ML-Fe NPs/peroxymonosulfate catalytic system for the degradation of Rhodamine B dye wastewater. The ML-Fe NPs demonstrated remarkable catalytic potential, achieving a 99% degradation efficiency for Rhodamine B within a span of 40 min.

Is natural better? An ecotoxicity study of anthraquinone dyes

The concept of sustainability has gained prominence in recent years, enhancing the need to develop products that are less harmful to the environment. Dyes are used by various industrial sectors and have a lot of market value; they are used on a large scale mainly by the textile industry that uses large volumes of water and is one of the main contributors to the contamination of water bodies. Some natural compounds, especially anthraquinones are re-emerging as possible alternatives to synthetic dyes, some of which are known for their toxic and/or mutagenic effects. The BioColour project (https://biocolour.fi/) which is interested in promoting the development of new alternative molecules to synthetic dyes, provided us highly purified anthraquinone dyes dermocybin and dermorubin (>98% purity) extracted from a specie of fungus Cortinarius sanguineus. Dyes were tested for their acute and chronic toxicity using different aquatic organisms. Dermorubin was not toxic to any of the organisms tested for the highest test concentration of 1 mg L-1 and it was the most promising dye. Dermocybin was toxic to Daphnia similis (EC50 = 0.51 mg L-1), Ceriodaphnia dubia (IC10 = 0.13 mg L-1) and Danio rerio embryos (extrapolated LC50 = 2.44 mg L-1). A safety limit, i.e, predicted no-effect concentration (PNEC) of 0.0026 mg L-1 was derived based on the toxicity of dermocybin. The PNEC value can be used to provide hazard information for future application in commercial dyeing processes. Then, we compared the toxicity of dermocybin and dermorubin with ecotoxicity data available in the literature on other anthraquinone dyes of natural and synthetic origin. Some natural dyes can be as toxic as synthetic ones, or more toxic when chronic effects are considered. Despite natural dyes being used since centuries past, there are few ecotoxicological studies available. This study is designed to help develop a more comprehensive understanding of their toxicological properties.

Sulfonate-modified calixarene-based porous organic polymers for electrostatic enhancement and efficient rapid removal of cationic dyes in water

Developing of fast and efficient adsorbents for removal of low concentration refractory organics in water is significant. Herein, a novel calix[4]arene-based porous organic polymer CaPy is constructed through Sonogashira-Hagihara cross-coupling polycondensation. The strong polar sulfonate is further anchored onto the polymer skeleton of CaPy and three sulfonate-modified anionic polymers CaPy-S1, CaPy-S2, and CaPy-S3 were obtained and fully characterized. The adsorption isotherms showed that the maximum adsorption capacities of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward methylene blue (MB) were 270, 1454, 558 and 1381 mg g^-1, whereas those for Rhodamine B (RhB) were 183, 2653, 1132, and 1796 mg g^-1, respectively. The maximum adsorption capacity toward RhB was the highest reported vale among the currently used synthetic adsorbents. In addition, the pseudo-second-order rate constants of CaPy, CaPy-S1, CaPy-S2, and CaPy-S3 toward MB were 0.00572, 0.488, 2.24, and 0.192 g mg^-1 min^-1, respectively, and those toward RhB were 0.000234, 0.138, 0.0819, and 0.203 g mg^-1 min^-1, respectively. The pseudo-second-order rate constant of CaPy-S2 toward MB was 2.24 g mg^-1 min^-1 indicating one of the highest adsorption speeds. The activation energy of CaPy-S1 for RhB and MB were 121 and 109 kJ mol^-1, respectively, demonstrating that the adsorption of both dyes on CaPy-S1 was chemisorption process. Further, the obtained values of Gibbs free energy were negative, revealing that the adsorption process was spontaneous. This work provides an effective approach for improving adsorption performance via post-modification.

Dye recovery with photoresponsive citric acid-modified BiOCOOH smart material: Simple synthesis, adsorption-desorption properties, and mechanisms

Dye recovery is of great significance for a circular economy and sustainable development. However, green recovery strategies without secondary pollution remain a significant challenge. To resolve this issue, a light-responsive smart material (citric acid-modified BiOCOOH (m-BOCH)) was synthesized and applied for dye recovery through adsorption in the dark, and desorption under visible light. With the modification of citric acid, the adsorption level of methylene blue (MB) on m-BOCH (43.4%) was more than six times that of pure BiOCOOH (7.1%). The desorption rate was ∼90% in 120 min under 420 nm light irradiation (there was no desorption for pure BOCH). Further, the adsorption rate was improved to 83.9% and the desorption rate remained stable at an optimal pH of 10.09. Characterization results indicated that carboxyl groups were modified onto the surface of BiOCOOH and served as adsorption sites for MB. Under visible light exposure, the connections between the carboxyl groups and BiOCOOH were damaged, which led to the desorption of MB from the surface of the m-BOCH. The recovered MB exhibited a good staining effect on hepatic stellate cells (HSC) as a fresh dye. The regeneration of m-BOCH was achieved through a moderate hydrothermal process, and the adsorption and desorption capacities were restored to 80.8% and 85.7%, respectively. This research provides a novel environmentally compatible strategy for dye recovery without secondary pollution. This is a very promising treatment technique for dye effluents, which highlights the application of smart materials resource recycling for environmental remediation.

Garlic peel based mesoporous carbon nanospheres for an effective removal of malachite green dye from aqueous solutions: Detailed isotherms and kinetics

Biowaste based nanoadsorbents have gained much attention in the recent times for wastewater decolourization owing to their low cost, high surface area and high adsorption capacities. In the present research, garlic peel based nanoparticles (GCNP) were synthesized at different temperatures by a one step pyrolytic green approach for the effective removal of cationic dye, malachite green from the aqueous medium. The surface properties of Garlic nanoparticles were elucidated by N₂ adsorption- desorption and all the GCNP samples were found to exhibit Type IV(a) isotherm indicating the presence of mesopores in carbon matrix. Using BET calculations, highest surface area (380 m²/g) was obtained for GCNP synthesized at 1000 ^◦C. Characterization of nanoparticles was done by XRD, EDAX, SEM and FTIR studies before and after the dye treatment. Adsorption studies conducted using different parameters like contact time, concentration and pH and dosage of adsorbent showed removal efficiency above 90% for the contact time of 70 min. Best adsorption experimental results were obtained for GCNP synthesized at 1000 °C ascribable to its high surface area, higher total pore volume (0.26 cm²/g) and higher carbon content. Four adsorption isotherm models were used to validate batch equillibrium studies and the results showed data in good agreement with Langmuir and Freundlich isotherms with maximum Langmuir adsorbtion capactiy to be 373.7 mg/g. Kinetic modelling of the data showed best fit with the Pseudo second order model with rate constant value of 48.726 g mg^-1 min^-1. Regenerative studies were conducted conducted upto 6 cycles. Also the GC nanoparticles were tested for their compatibility in membrane form wherein, removal efficiency results were obtained for GCNP anchored in polyvinyl difluoride (PVDF) and polysulfone (PSF) membrane matrix for dye adsorption.

Behavior of two classes of organic contaminants in the presence of graphene oxide: Ecotoxicity, physicochemical characterization and theoretical calculations

Graphene oxide (GO) production has increased considerably and therefore its presence in the environment is inevitable. When in aquatic environment GO can interact with co-existing compounds, modifying their toxicities for several organisms. However, the toxic effects of co-exposure of GO and organic compounds are rarely reported in the literature. Herein, we studied the behavior of four organic aquatic contaminants found in surface water such as 2-phenylbenzotriazoles (non-Cl PBTA-9 and PBTA-9) and phenoxyphenyl pesticides, pyriproxyfen (PYR) and lambdacyhalothrin (LCT), in the presence of GO. GO reduced 90% and 83% of the toxicity of non-Cl PBTA-9 and PBTA for Daphnia. When PBTAs were adsorbed onto GO surface their interactions caused GO agglomeration (up to 20 mm) and consequent precipitation, making PBTAs less bioavailable. PYR and LCT's toxicities increased up to 83% for PYR and 47% for LCT in the presence of GO, because their adsorption on GO lead to the stabilization of the suspensions (up to 0.5 μm). Those particles were then easily ingested and retained in the digestive tract of the daphnids, triggering the Trojan horse effect. Based on theoretical calculations we observed that PBTA compounds are planar, electron-poorer and more reactive than the studied pesticides, suggesting a better stability of the GO/PBTA complexes. PYR and LCT are nonplanar, electron-richer and less reactive towards GO than PBTAs, forming less stable GO complexes that could facilitate the desorption of pesticides, increasing toxic effects. Our results suggest that the properties of the organic toxicants can influence the stability of graphene oxide suspensions, playing a fundamental role in the modulation of their toxicity. Further research is needed for a deep understanding of the behavior of nanomaterials in the presence of contaminants and their effect in the toxicity of aquatic organisms.

Molecular characterization and ecotoxicological evaluation of the natural dye madder and its chlorinated products

There has been increased interest in the use of natural dyes for textile coloration as alternatives to synthetic dyes, due to the general belief that natural dyes are more environmentally friendly. However, natural dyes have poor affinity for textiles, which can lead to high dye levels in the resultant wastewater. While chlorine treatment has proven to be effective for dye wastewater disinfection and decolorization, this process can also lead to the formation of more toxic degradation products for certain synthetic dyes. On the other hand, little information is available regarding the ecotoxicity of natural dyes and their chlorination products. To advance knowledge in this area, madder was selected due to its historical importance and wide application in the textile industry. Specifically, we sought to characterize the chlorine-induced degradation products of an aqueous madder solution and to assess their ecotoxicity. The main component of the present madder sample was Alizarin (89.8%). Chlorination led to complete decolorization, and 2-hydroxynaphthalene-1,4-dione and phthalic anhydride were identified as key degradation products. Chlorination of madder decreased toxicity to Daphnia similis (microcrustacean) 10-fold and removed the toxicity to Raphidocellis subcapitata (algae), when compared to the parent dye.

Facile fabrication of composite cellulose fibrous materials for efficient and consecutive dyeing wastewater treatment

Fabricating dye adsorbents with efficient adsorption properties is of great significance in the treatment of printing and dyeing wastewater. Herein, composite materials of polydopamine decorated cellulose fibrous nonwovens (PDA@CF NWs) were fabricated by constructing a PDA functional layer on the surface of cellulose fibers via in situ polymerization. In addition, a three-dimensional adsorbent of 3D PDA@CF NWs with good hydrophilicity, structural stability, and compression resistance could be obtained using a facilely laminating and traditional loop bonding reinforcing technique. Attributed to the efficient and uniform loading of an active PDA functional layer, the resulting PDA@CF NWs exhibited a relatively large adsorption capacity of around 91 mg g⁻¹ towards the template dye of methylene blue within a fast equilibrium time of 2 h, which was superior to most of the fibrous adsorbents. In addition, the treatment column of 3D PDA@CF NWs exhibited a breakthrough capacity of 40.9 mg g⁻¹, reaching nearly 50% of the static saturated dye-binding capacity. More importantly, the 3D PDA@CF NWs column could effectively and continuously separate the mixture of different dyes under gravity, highlighting an excellent practical performance. Thus, the PDA@CF NWs are expected to provide a promising candidate for environment-friendly, large-scale and efficient treatment of industrial printing and dyeing wastewater.

Composite materials of polydopamine decorated cellulose fibrous nonwovens were fabricated for efficient and consecutive dyeing wastewater treatment.

Mutagenicity of a novel 2-phenylbenzotriazole (non-chlorinated 2-phenylbenzotriazole-9) in mice

Dinitrophenylazo dyes can form 2-phenylbenzotriazoles (PBTAs) in the textile dyeing process upon the addition of chemical reducing agents. Some dinitrophenylazo dyes, as well as their respective reduced (non-chlorinated) and chlorinated PBTAs, are now found in rivers owing to wastewater from textile plants. This study aimed to investigate the genotoxicity of a new PBTA derived from C.I. Disperse Violet 93 azo dye, namely non-Cl PBTA-9. Primary DNA damage in the blood, liver, and colon cells, micronucleated cells in the bone marrow, and gene expression (NAT2, CYP1A1, TRP53, and CDKN1A) in liver cells were observed in mice, at acute oral exposure (gavage) doses of 5, 50, and 500 μg/kg body weight (b.w.). The non-chlorinated PBTA-9 caused DNA damage in the blood and liver (at 500 μg/kg b.w.) and in colon cells (at 5, 50, and 500 μg/kg), and increased the frequency of micronucleated cells in the bone marrow (at 5 and 50 μg/kg). No histological alterations or gene expression changes were observed. In conclusion, in vivo exposure to non-chlorinated PBTA-9 induced genetic damage in various rodent tissues, corroborating results previously obtained from the Ames test. Because this compound has been detected in rivers, exposure to humans and biota is a major concern.

Ultrafast and high efficiency photodegradation of dyes under visible light by Au nanocluster-promoted Zn0.5Cd0.5S nanorods

Au nanoclusters decorated on the lateral surface of ultrathin ZCS nanorods could maximize the photocatalytic activity of ZCS by PRET mechanism. This makes it possible to use less photocatalysts to degrade more recalcitrant dyes in a short time.