Toxic Aromatic Amines Research Articles

Efficient activation of peroxymonosulfate by 3D blocky sponge-supported spinel ferrite nanocomposites for convenient removal of aniline

Aniline, a toxic aromatic amine prevalent in printing and dyeing effluents, has garnered significant attention due to its potential risks to human health and the environment. In this study, 3D blocky melamine sponge-supported spinel ferrite nanocomposites (MFe2O4@MS) were synthesized to activate peroxymonosulfate (PMS) for the removal of aniline from printing and dyeing wastewater. The CoFe2O4@MS-PMS achieved complete removal of aniline within 10 min across a pH range of 5 to 11, significantly outperforming the CuFe2O4@MS-PMS and ZnFe2O4@MS-PMS systems. Electron paramagnetic resonance (EPR) and probe-based kinetic model experiments certified the formation of sulfate radicals (•SO4−), hydroxyl radicals (•OH), and singlet oxygen (1O2) during the process, where •SO4− was identified as the principal reactive species responsible for aniline degradation. The Langmuir-Hinshelwood model demonstrated that the melamine sponge framework significantly improved the dispersion and adsorption capabilities of MFe2O4 nanoparticles. This enhancement led to localized enrichment of aniline and PMS on the surface. Furthermore, the removal of aniline by CoFe2O4@MS-PMS performed satisfactorily in five-cycle experiments and in actual printing and dyeing wastewater. This research offers new insights into the design and synthesis of environmentally friendly and highly active PMS catalysts for aniline degradation in industrial wastewater.

Investigation into the electrochemical advanced oxidation of p-arsanilic acid: Peculiar role of electrolytes and unexpected formation of coupling byproducts

Although banned in some countries, p-arsanilic acid (ASA) is still widely used as feed additive in poultry production. As a result, ASA is usually released into the aquatic environment without any treatments. Although ASA exhibits low toxicity, it can be transformed into highly toxic aromatic amines and inorganic arsenic species (As (V) as H2AsO4− and HAsO42−) under natural environmental conditions. Hence, it is necessary to develop efficient technologies for its removal or degradation. In this contribution, electrochemical advanced oxidation technology with boron-doped diamond (BDD) had been initially used to degrade ASA pollutants. A five-level central composite rotatable design (CCRD) was implemented to optimize the various influencing factors involved, among applied current density, NaCl concentration, Na2SO4 concentration and NaHCO3 concentration on the oxidation efficiency; the latter was assessed in terms of ASA degradation percentage. The results obtained highlighted the unique and important roles of electrolytes during the electrolytic oxidations. Meanwhile, the major degradation byproducts detected were also strongly dependent on the electrolyte adopted. In particular, several oligomer byproducts with novel structures were initially identified in BDD-treated ASA solutions. Two different electrochemical transformation pathways of ASA on BDD anode were thus proposed. This study demonstrated the effectiveness of BDD technology in the degradation of ASA, as well as the potential minor risk of its application in actual ASA wastewater treatment.

Robust synthesis of water stable ciprofloxacin functionalized hybrid metal-organic antimicrobial pigments for coating applications

Pigment production by calcination process at high temperatures (up to 1000 °C) or through diazotization process using toxic aromatic amines makes it an energy-intensive and hazardous process. To overcome these, a hybrid system of organic-inorganic coordination polymers has been synthesized by combining carboxymethylated diols and metal ions in aqueous conditions to produce metal-organic pigments (MOP's) at a low temperature of 70 °C. The poor water stability of these materials was overcome by introducing a pair of ether linkages in each ligand that can effectively repel the water molecules and preserve the structural integrity. The resultant MOP's retained their crystallinity even after incubating them for 24 h in aqueous and acidic conditions. UV-DRS studies showed the band gap of the MOP's at 2.78 and 2.38 eV leading to the formation of reddish-brown and yellow-colored pigments. The MOP's were able to cover the defects and uniformly impart color upon spray coating. Additionally, ciprofloxacin (CF) was functionalized onto the MOP's with a loading efficiency of 230 ± 15 mg/g reaching 92 ± 1.5% uptake and the XPS analysis revealed interaction between the free metal sites on MOP and carboxylic acid group present in CF through coordinate linkages. The CF functionalized MOP's were able to arrest the growth of tested microbes up to 96% resulting in fabrication of antimicrobial pigments that can be explored for the construction of antifouling surfaces.

Synthesis, characterization and application of a polyindole coated magnetic porous carbon nanoadsorbent for extraction and determination of toxic aromatic amines

In this research, a polyindole coated magnetic porous carbon (MPC@PIN) nanoadsorbent was synthesized and applied to the extraction of toxic aromatic amines from divers real water. The MPC was derived from MIL-53(Fe) as a metal–organic framework (MOF) source by calcination of the MOF under an inert atmosphere. After that, the functionalization process was performed by the polymerization of indole on the surface of the MPC. The synthesized nanoadsorbent (MPC@PIN) was characterized by various methods such as Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). Separation and determination of the target analytes was performed by HPLC-photodiode array (PDA) detection system. The extraction performance of MIL-53(Fe), MPC, and MPC@PIN was compared toward the target analytes, and the results exhibit the best extraction efficiency for the MPC@PIN. After optimization of the affecting parameters, LODs and linear ranges were 0.05–0.2 µg/L and 0.15–400 µg/L, respectively. Precision (n = 3) of the method as intra-day RSD, and inter-day RSD values were obtained in the range of 3.5–8.2%, and 5.8–12.3%, respectively. Finally, the method applicability was affirmed by analyzing various water samples, satisfactorily. To prepare spiked water samples, a small volume of the AAs standard solution was added to each sample, and then the spiked sample was subjected to the MSPE process.

A Review of Bacterial Degradation of Azo Dyes

Biodegradation of synthetic dyes using different bacteria is becoming an accepted approach for treating Azo dye wastewater to mitigate many environmental problems. Azo dye has a negative impact on the environment by increasing biochemical oxygen demand (B.O.D.) and chemical oxygen demand (C.O.D.). The Biodegradation of azo dyes by different bacteria was evaluated. Biodegradation of synthetic dyes not only results in the decolorization of the dyes but also in the disintegration of the dye molecules into smaller and simpler parts. Decolorization of the dye arises when the chromophoric center of the dye is slashed. Various microorganisms, including fungi, bacteria, yeasts, and algae, have been used to decolorize and Degradation of synthetic dyes. Bacterial decolorization is usually faster than fungal decolourization. It is well known that bacteria degrade azo dyes reductively under anaerobic circumstances to colorless aromatic amines, which are carcinogenic compounds. These colorless aromatic amines must also be degraded because they may be toxic, mutagenic, and carcinogenic to humans and animals Bacteria are capable of removing dyes by adsorption and absorption. Biosorption rates are directly matched with the composition of heteropolysaccharides and the cell wall lipids. Dead cells are more useful in Biosorption than living cells because they do not need nutrients and can be stockpiled for a long time. The azoreductases are considered to be the most potent group of enzymes active in the Biodegradation of synthetic azo dyes. They accomplish the reductive cleavage of synthetic azo dyes bonds. Laccases enzymes become more interesting and have more focus recently due to their ability in generating much lower toxic aromatic amines. Laccases do not need other cofactors. Many factors affecting the process are temperature, pH, salinity, dye concentration, and Bioremediation in aerobic and anaerobic environments. Keywords: Biodegradation, azo dyes, biochemical oxygen demand (B.O.D.), chemical oxygen demand (C.O.D.), bacterial enzymes and Bacterial Laccases enzymes.

Photoinitiation abilities of indeno- and indoloquinoxaline derivatives and mechanical properties of dental fillings based on multifunctional acrylic monomers and glass ionomer

Photopolymerization is a rapidly expanding technology with a wide variety of applications, from imaging to biomedical uses. Here, we present enhanced photosensitization of polymerization by photoredox pairs based on indene- and indoloquinoxaline dyes and thiophenoxyacetic acid for dental applications. The photoinitiating ability of the two-component systems was tested using several multifunctional monomers of various structures typical for dental fillings. The new photoinitiating systems show excellent efficiency in initiating free radical polymerization which occurs by photoinduced intermolecular electron transfer (PET) mechanism. Modification of the dye structure by extending the chain of conjugated π bonds, the arrangement of aromatic rings and the type of heteroatom, allowed to change the spectroscopic properties of the tested compounds and use them as absorbers of light emitted by dental lamps. The improved mechanical properties of the cured polymers, i.e., lowering the temperature during photopolymerization and an increase in polymer hardness were observed for the proposed photoinitiating systems compared to the camphorquinone – photoinitiator traditionally used in dentistry. This indicates that the dye – thiophenoxyacetic acid systems may be useful as photoinitiators in dental applications. The undoubted advantage of these photoinitiating systems is the elimination of the toxic aromatic amines traditionally used as co-initiators from the dental composition. It was possible thanks to the use of thiophenoxyacetic acid. Its application does not reduce the polymerization rate and does not extend the photocuring time.

N-acetylation of toxic aromatic amines by fungi: Strain screening, cytotoxicity and genotoxicity evaluation, and application in bioremediation of 3,4-dichloroaniline

Aromatic amines (AA) are one of the most commonly used classes of compounds in industry and the most common pollutants found in both soil and water. 3,4-Dichloaniline (3,4-DCA) is a persistent residue of the phenylurea herbicide in the environment. In this study, we used a colorimetric method as a new approach to screen 12 filamentous fungal strains of the genera Aspergillus, Chaetomium, Cladosporium, and Mucor to assess their capacity to perform AA N-acetylation since it is considered a potential tool in environmental bioremediation. Subsequently, the selected strains were biotransformed with different AA substrates to evaluate the product yield. The strains Aspergillus niveus 43, Aspergillus terreus 31, and Cladosporium cladosporioides showed higher efficiencies in the biotransformation of 3,4-DCA at 500 µM into its N-acetylated product. These fungal strains also showed great potential to reduce the phytotoxicity of 3,4-DCA in experiments using Lactuca sativa seeds. Furthermore, N-acetylation was shown to be effective in reducing the cytotoxic and genotoxic effects of 3,4-DCA and other AA in the immortalized human keratinocyte (HaCaT) cell line. The isolated products after biotransformation showed that fungi of the genera Aspergillus and Cladosporium appeared to have N-acetylation as the first and main AA detoxification mechanism. Finally, A. terreus 31 showed the highest 3,4-DCA bioremediation potential, and future research can be carried out on the application of this strain to form microbial consortia with great potential for the elimination of toxic AA from the environment.

Glycine ester ionic liquid as new co‐initiator used in initiating radical and cationic photopolymerization

AbstractIonic liquids using amino acid ester as cations is a new generation of green ionic liquids. It is found for the first time that they can be used as co‐initiators to initiate radical photopolymerization in the presence of commercial type II sensitizer, camphorquinone (CQ) under mild irradiation conditions. To intensively investigate this new function, we synthesized a series of glycine ester ionic liquids by a very simple method, and then evaluated their performance as co‐initiators in radical photopolymerization. The polymerization studies show that their co‐initiation abilities depend strongly on the structures of N‐terminal substituents and ester groups, as well as the type of anion moiety. And the pH values of the formula also have a heavy influence on their performances. More interestingly, when a small amount of hydroxyethyl acrylate (HEA) was added, under irradiation this multicomponent system composed of CQ, ionic liquids when anion moiety is PF6−, BF4− or SbF6−, and HEA, can release H+ to initiate cationic polymerization. These facts demonstrated that the investigated glycine ester ionic liquids can be considered as valid, environmentally friendly alternatives to toxic aromatic amines co‐initiators. Besides, the corresponding photoinitiation mechanism is suggested.

N-Acetylation of Toxic Aromatic Amines by Fungi: Strain Screening, Cytotoxicity and Genotoxicity Evaluation, and Application in the Bioremediation of 3,4-Dichloroaniline

N-Acetylation of Toxic Aromatic Amines by Fungi: Strain Screening, Cytotoxicity and Genotoxicity Evaluation, and Application in the Bioremediation of 3,4-Dichloroaniline

Purification of Textile Effluents Containing C.I. Acid Violet 1: Adsorptive Removal versus Hydrogen Peroxide and Peracetic Acid Based Advanced Oxidation

Textile effluent containing azo dyes such as C.I. Acid Violet 1 (AV1) can be degraded to toxic aromatic amines in the environment. Thus, there is a legitimate need to treat such effluents before they are discharged to surface waters. Two methods were proposed to remove AV1 from aqueous solutions: adsorption and advanced oxidation processes (AOPs). The sorption capacity of the strongly basic anion exchanger Purolite A520E of the polystyrene matrix determined from the Langmuir isotherm model was found to be 835 mg/g, while that of Lewatit S5428 of the polyacrylamide matrix Freundlich model seems to be more appropriate for describing the experimental data. The pseudo-second-order kinetic model and external diffusion are the rate limiting steps of adsorption. The removal efficiency of AV1 by the anion exchangers was higher than 99% after 40 min of phase contact time. AOPs involved the usage of hydrogen peroxide and peracetic acid (PAA) as oxidizing agents, while Fe2+ and simulated sunlight were used as oxidizing activators. AV1 oxidation followed the pseudo-first-order kinetics, and the systems with the highest values of the rate constants turned out to be those in which Fe2+ was present. The efficiency of oxidation measured by the degree of decolorization in the systems with Fe2+ was higher than 99% after 10–60 min. AV1 mineralization was slower, but after 120 min of oxidation it was higher than 98% in the H2O2/Fe2+, PAA/Fe2+ and PAA/Fe2+/sunlight systems.

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.

Decolourisation and Biodegradation of Textile Di-azo Dye Congo Red by Chryseobacterium geocarposphaerae DD3

In the present study, Chryseobacterium geocarposphaerae DD3 isolated from textile industry dye effluent in West Bengal, India, displayed significant tolerance to sulfonated di-azo dye Congo red (CR), up to 500 ppm. The optimum decolourisation revealed that C. geocarposphaerae DD3 was capable of 96.52% decolourisation of 0.2 g L−1 CR within 12 h of treatment in the presence of 5 g L−1 glucose as supplementary carbon source. Biodegradation analysis of decolourised CR containing water was investigated by FTIR, MS and 1H NMR, which confirmed the absence of azo bond as well as the toxic aromatic amines. Further, phytotoxicity analysis was performed to assess the toxicity of CR before and after bacterial treatment. Growth indexes of Vigna radiata L. seed confirmed that the biodegraded water was non-phytotoxic in comparison to the control CR solution. Multivariate analyses confirmed the same, showing significant differences between measured plant health indicators for CR solutions, whereas no significant differences were found between distilled and treated water. This study is novel as it is the first report of dye degradation by C. geocarposphaerae and may lead to a sustainable way of treating dye-contaminated water in the near future.

A novel inhibition mechanism of aniline on nitrification: Aniline degradation competes dissolved oxygen with nitrification

Aniline is a toxic aromatic amine and an inhibitor of nitrification. This study explored the inhibition effect and underlying mechanism. After sludge acclimation, 540 mg/L aniline was removed in 24 h and almost all ammonia released from aniline was oxidized to nitrate. However, nitrification never started until no aniline left. The cellular adenosine triphosphate (cATP) concentration of acclimated sludge reduced only by 2% after aniline exposure. Neither transmembrane transport of ammonia nor ammonia monooxygenase (AMO) activity was affected by aniline. Growing initial aniline concentration did not deteriorate the specific nitrification rate (NR). These all revealed that the toxicity of aniline only play a minor role in inhibition. Competition for dissolved oxygen (DO) was proposed to be another possible inhibition mechanism. The oxygen affinity constant (Ks) of aniline degraders and ammonia-oxidizing bacteria (AOB) was calculated to be 0.894 mg/L and 1.274 mg/L respectively, suggesting the former possessed much stronger oxygen affinity (P < 0.01). With aniline and ammonium as initial substrates, increasing aeration intensity advanced nitrification and increased the NR. Max NR of 0.63 mgN/(gMLSS·h) was achieved at the highest aeration intensity of 1000 mL/min. This study brings one step closer to better removal of aniline and derived nitrogen pollutants.

Biosorption of astrazon red dye by the bacterium Rhodopseudomonas sp. strain 51ATA

Astrazon red azodye that is still widely used in Turkey is released into the aquatic environment. Since these dyes are degradable into the toxic aromatic amines, they have become a public health and environmental concern. In this study, the biosorption of the Astrazon red dye from aqueous solutions on dehydrated cells of Rhodopseudomonas sp. 51ATA was studied as a function of each pH, temperature and initial dye concentration. Rhodopseudomons sp. 51ATA strain belongs to the Rhodopseudomonas species which is an eco-friendly photosynthetic and facultative anaerobic bacterium. The best uptake of Astrazon red was observed at pH 2.0 and the data obtained were applied to both Freundlich and Langmuir adsorption isotherms. The adsorption data provided an excellent fit to both isotherms and showed good agreement to Scatchard analysis at various temperatures. Freundlich isotherm showed good fit to the data at low temperatures while Langmuir model was suitable for describing the adsorption at higher temperatures. Therefore, from these data, we could report that Rhodopseudomonas sp. 51ATA strain is very efficient bacterium for the removal of dyes from wastewater.

The key role of oxygen in the bioremoval of 2,4-diaminoanisole (DAAN), the biotransformation product of the insensitive munitions compound 2,4-dinitroanisole (DNAN), over other electron acceptors

Insensitive munitions compounds, such as 2,4-dinitroanisole (DNAN), are replacing conventional explosives. DNAN is anaerobically reduced to 2,4-diaminoanisole (DAAN), a toxic aromatic amine. However, the removal of DAAN under different redox conditions is yet to be elucidated. Herein, we analyzed DAAN consumption in biotic and abiotic microcosms when exposed to different redox conditions (without added electron acceptor, without added electron acceptor but with pyruvate as a co-substrate, with sulfate, with nitrate, and with oxygen), using an anaerobic sludge as inoculum. We observed that DAAN autoxidation, an abiotic reaction, was significant in microaerobic environments. DAAN also reacted abiotically with heat-killed sludge up to a saturation limit of 67.4 μmol DAAN (g VSS heat-killed sludge)−1. Oxygen caused the fastest removal of DAAN in live sludge among the conditions tested. Treatments without added electron acceptors (with or without pyruvate) presented similar DAAN removal performances, although slower than the treatment with oxygen. Sulfate did not exhibit any effect on DAAN removal compared to the treatment without added electron acceptors. Nitrate, however, inhibited the process. An enrichment culture from the microcosms exposed to oxygen could be developed using DAAN as the sole substrate in microaerobic conditions. The enrichment profoundly changed the microbial community. Unclassified microorganisms accounted for 85% of the relative abundance in the enrichment culture, suggesting that DAAN microaerobic removal might have involved organisms that were not yet described. Our results suggest that DAAN microaerobic treatment can be coupled to DNAN anaerobic reduction in sludge, improving the treatment of DNAN-containing wastewaters.

Diphenylsilane‐Manganese Acetylacetonate Redox Initiating Systems: Toward Amine‐Free and Peroxide‐Free Systems

AbstractRoom temperature redox initiated free radical polymerization (RFRP), without light, brings a significant breakthrough in the field of materials science including energy conservation, high efficiency, robustness in thick materials/composites, and easy operation. Meanwhile, the current redox initiating systems used are based on toxic aromatic amines and hazardous peroxides (e.g., dibenzoylperoxide). In the present paper, for the first time in literature, new amine‐free, peroxide‐free redox two component (2K) initiating systems comprised of diphenylsilane (DPS, a reducing agent) and manganese acetylacetonate (Mn(acac)3, an oxidizing agent) are proposed. The significance of the system is its applicability under mild conditions (RT, under air). Optical pyrometry measurement results showed that the DPS in combination with Mn(acac)3 exhibited an excellent radical initiating property for benchmark (meth)acrylate monomers, competitive with a well‐established amine/dibenzoyl peroxide reference. Based on electron spin resonance experiments, the initiating chemical mechanisms of RFRP are proposed.

Fast-changing life-styles and ecotoxicity of hair dyes drive the emergence of hidden toxicants threatening environmental sustainability in Asia

The practice of hair dyeing is a rapidly expanding industry on a global scale; however, it has become a major concern for Asian countries because they have been undergoing rapid transformations of their environment and lifestyles. While the socio-economic benefits and impacts of this globalization trend are widely understood, the environmental effects are largely unknown. In particular, commonly available oxidative dyes potentially pose specific environmental risks due to their use of a toxic aromatic amine p-Phenylenediamine (PPD). In investigating the environmental impacts of PPD chemicals, we first provide context to the study by setting out the socio-psychological drivers to industrial expansion in Asian countries along with an overview of research into its effects, to show that its environmental impacts are under-researched. We then investigate the environmental toxicity of PPD by focusing on the role of microbes in metabolizing waste products. Results show that Acinetobacter baumannii EB1 isolated from dye effluent prevents autoxidation of PPD under oxygen-enriched (shaking) or oxygen-deficient (static) conditions representing different environmental settings. Microbes transformed PPD into more toxic metabolites, which then significantly reduced plant growth, thereby having a direct bearing on ecosystem services. Based on the findings, we argue that stricter regulatory controls on hair dye wastewater are necessary, particularly in newly industrialising Asian countries where the expansion of commercial practice is most prevalent.

Silane Based Redox Initiating Systems: Toward a Safer Amine-Free, Peroxide-Free, and Metal-Free Approach

Room temperature redox initiated free radical polymerization (RFRP) has always attracted high attention in the field of materials due to its advantages of energy saving, high efficiency, and easy operation. However, the current redox initiating systems are based on toxic aromatic amines and hazardous peroxides (e.g., dibenzoylperoxide). In the present paper, the redox two component (2K) initiating performances of silanes (as reducing agents) in combination with a highly stable iodonium salt (as oxidizing agent) were studied for the first time under mild conditions (RT, under air). Optical pyrometry measurements and DSC investigation results showed that the diphenylsilane (DPS) exhibited a unique initiating property for several (meth)acrylate monomers. Remarkably, thermal postcuring (B-stage) is also possible using this system. Based on electron spin resonance (ESR) experiments, the initiating chemical mechanisms of RFRP are established. Importantly, the new proposed initiating systems can be used for the preparation of tack-free glass fibers and carbon fibers composites at room temperature.

Sequential anaerobic-aerobic treatment using plant microbe integrated system for degradation of azo dyes and their aromatic amines by-products

The presence of unused dyes and dye degradation intermediates in the textile industry wastewaters is the major challenge in its treatment. A wide range of treatments including various physicochemical processes are used for this wastewater. Incomplete dye degradation results in hazardous colorless aromatic amine intermediates that are teratogenic in nature. A synergistic plant-microbe system operated in a sequential anaerobic-aerobic mode was evaluated for the complete degradation of a model azo dye methyl red under laboratory conditions. The degradation of methyl red and its break down products 2-aminobenzoic acid and N,N-dimethyl-p-phenylenediamine were analysed by HPLC, FTIR and GC–MS. The vetiver-microbe system had shown enhanced dye degradation. The dye decolourization percentage achieved for integrated plant-microbe treatment system (T) after anaerobic condition was 53.5 ± 6.2% and aerobic condition was 92 ± 3.4%. The removal efficiency of the intermediates 2-ABA and DMPD was found to be 89.79% in the integrated plant-microbe treatment system. The plant-microbe system was most effective in the removal of toxic aromatic amine as seen by lesser phytotoxicity for seed germination and teratogenicity in case of zebrafish development in the treated water.

Tannin-based thin-film composite membranes for solvent nanofiltration

The natural oligomer tannic acid was used as a reactant for an interfacial polymerization on top of a crosslinked polyacrylonitrile (PAN) membrane. The PAN membrane was soaked with the aqueous tannic acid solution and contacted with a dilute solution of teraphtaloyl chloride in hexane. Since both layers, the PAN support and the thin tannin-based layer, are highly crosslinked, the resulting thin film composite membrane is stable in harsh solvent environments such as N-Methyl-2-pyrrolidone (NMP). NMP permeances of up to 0.09L/m2hbar with a molecular weight cut-off of approximately 800g/mol were obtained. The exceptional stability in NMP and the incorporation of natural compounds like tannic acid for the manufacture of organic solvent nanofiltration membranes provides a cost-effective alternative for industrial separations due to the simplicity of the interfacial reaction and the replacement of the commonly applied toxic aromatic amines. The scale up of the manufacturing process is not difficult; the low price of the natural tannic acid is another advantage.