Molecular interactions of paraben family of pollutants with embryonic neuronal proteins of Danio rerio: A step ahead in computational toxicity towards adverse outcome pathway

The paraben family of endocrine disruptors exhibit persistent behaviours in aquatic matrices, having bio-accumulative effects and necessitating toxicity analysis and safe use, as well as prevention of food web penetration. In this study, the toxicity effects of 9 different parabens (Methyl, Ethyl, Propyl, Butyl, Heptyl, Isopropyl, Isobutyl, benzyl parabens and p-hydroxybenzoic acid) were studied against 17 neuronal proteins (Neurog1, Ascl1a, DLA, Syn2a, Ntn1a, Pitx2, and SoxB1, Her/Hes, Zic family) expressed during the early embryonic developmental stage of Danio rerio. The neuronal genes were selected as a biomarker to study the inhibitory effects on the cascade of genes expressed in the early developmental stage. The study uses trRossetta software to predict protein structures of neuronal genes, followed by structural refinement, energy minimisation, and active site prediction, evaluated using energy value, RC plot and ERRAT scores of PROCHECK and ERRAT programs. Compared to raw structures, highly confident predicted structures and quality scores were observed for refined protein with few exceptions. Based on the polarity and charge of the aminoacids, the probable pockets were identified using active site prediction, which were then used for molecular docking analysis. Further, the ADMET analysis, ligand likeliness and toxicological test revealed the paraben family of compounds as one of the most susceptible toxic and mutagenic compounds. The molecular docking results showed an interesting pattern of increasing binding affinity with increase in the carbon chains of paraben molecules. Benzyl Paraben showed higher binding affinities across all 17 neuronal proteins. Finally, gene co-occurrence/co-expression and protein-protein interaction studies using the STRING database depict that all proteins are functionally related and play essential roles in standard biological processes or pathways, conserved and expressed in diverse organisms. The interaction between paraben compounds and neuronal genes indicates high risks of inhibiting reactions in embryonic stages, emphasising the need for effective treatment measures and strict regulations.

Recent Advances in the Development of Sustainable Composite Materials used as Membranes in Microbial Fuel Cells

MFC can have dual functions; they can generate electricity from industrial and domestic effluents while purifying wastewater. Most MFC designs comprise a membrane which physically separates the cathode and anode compartments while keeping them electrically connected, playing a significant role in its efficiency. Popular commercial membranes such as Nafion, Hyflon and Zifron have excellent ionic conductivity, but have several drawbacks, mainly their prohibitive cost and non-biodegradability, preventing the large-scale application of MFC. Fabrication of composite materials that can function better at a much lower cost while also being environment-friendly has been the endeavor of few researchers over the past years. The current review aims to apprise readers of the latest trends of the past decade in fabricating composite membranes (CM) for MFC. For emphasis on environmental-friendly CM, the review begins with biopolymers, moving on to the carbon-polymer, polymer-polymer, and metal-polymer CM. Lastly, critical analysis towards technology-oriented propositions and realistic future directives in terms of strengths, weakness, opportunities, challenges (SWOC analysis) of the application of CM in MFC have been discussed for their possible large-scale use. The focus of this review is the development of hybrid materials as membranes for fuel cells, while underscoring the need for environment-friendly composites and processes.

Systematic computational toxicity analysis of the ozonolytic degraded compounds of azo dyes: Quantitative structure-activity relationship (QSAR) and adverse outcome pathway (AOP) based approach

The present study identifies and analyses the degraded products of three azo dyes (Reactive Orange 16, Reactive Red 120, and Direct Red 80) and proffers their in silico toxicity predictions. In our previously published work, the synthetic dye effluents were degraded using an ozonolysis-based Advanced Oxidation Process. In the present study, the degraded products of the three dyes were analysed using GC-MS at endpoint strategy and further subjected to in silico toxicity analysis using Toxicity Estimation Software Tool (TEST), Prediction Of TOXicity of chemicals (ProTox-II), and Estimation Programs Interface Suite (EPI Suite). Several physiological toxicity endpoints, such as hepatotoxicity, carcinogenicity, mutagenicity, cellular and molecular interactions, were considered to assess the Quantitative Structure-Activity Relationships (QSAR) and adverse outcome pathways. The environmental fate of the by-products in terms of their biodegradability and possible bioaccumulation was also assessed. Results of ProTox-II suggested that the azo dye degradation products are carcinogenic, immunotoxic, and cytotoxic and displayed toxicity towards Androgen Receptor and Mitochondrial Membrane Potential. TEST results predicted LC50 and IGC50 values for three organisms Tetrahymena pyriformis, Daphnia magna, and Pimephales promelas. EPISUITE software via the BCFBAF module surmises that the degradation products' bioaccumulation (BAF) and bioconcentration factors (BCF) are high. The cumulative inference of the results suggests that most degradation by-products are toxic and need further remediation strategies. The study aims to complement existing tests to predict toxicity and prioritise the elimination/reduction of harmful degradation products of primary treatment procedures. The novelty of this study is that it streamlines in silico approaches to predict the nature of toxicity of degradation by-products of toxic industrial affluents like azo dyes. These approaches can assist the first phase of toxicology assessments for any pollutant for regulatory decision-making bodies to chalk out appropriate action plans for their remediation.

Microplastics in terrestrial ecosystem: Sources and migration in soil environment

Plastics, especially microplastics in soils, are considered a severe environmental issue worldwide. However, globally, the main research focus is on microplastic pollution in the marine environment, the microplastic pollution on soils and sediments remains on the sideline so far. But the fact is that microplastics are omnipresent in terrestrial systems in the form of microbeads in industrial systems and in sewage sludge. Their presence in agricultural soils and sediments is enormously increased due to plastic mulching, plastic greenhouses and compost and extensive use of controlled release fertilizers. Therefore, this review outlines the global scenario regarding plastics and microplastics production, consumption, and possible pathways of penetration into the soil environment. Various mechanisms to restrict and manage the pathways of plastics and microplastics into the soil environment are also discussed. This review also focuses on the challenges and limitations on the use of plastic alternates such as bioplastics and oxo plastics. Also, the knowledge gaps on the source of microplastics in the environment and their deleterious effects on properties of soil, soil health and focused light on their soil trophic transfer in food chains via plants. This review provides a detailed insight on the management and possible control measures to alleviate the potential risk caused by microplastics pollution in the soil environment and the overall ecosystem's health. In spite of the occurrence and fate of microplastics on terrestrial environment, knowledge gaps and challenges for tackling this contamination are also explored which facilitates the policy makers to develop regulatory measures towards the containment of microplastics in living ecosystem.

The regime of constructed wetlands in greywater treatment

There is an excellent need for supply-side threats due to the enhanced degradation and reclamation of existing water bodies in the present scenario. This led to the global water crisis. One of the easiest ways to fulfil the growing need for freshwater is the recycling of wastewater. Greywater is a form of wastewater from households, industries, etc., with some less toxic materials. The recycling of this greywater has provoked the development of new and sustainable technologies to meet the growing water demand. Engineered constructed wetlands are considered one of the most economically practical processes to treat greywater due to its minimal footprint. In this case study, we summarize several categories of constructed wetlands, operating conditions, and the effects of biological, physical, and chemical aspects of greywater on their treatment performance. On the other hand, the effluent quality from diverse wetlands is also summarized. Furthermore, it would be better to consider that constructed wetlands' integrated performance with disinfection may improve the effluent quality to desirable standards.

Agricultural waste materials for adsorptive removal of phenols, chromium (VI) and cadmium (II) from wastewater: A review

Management of basic natural resources and the spent industrial and domestic streams to provide a sustainable safe environment for healthy living is a magnum challenge to scientists and environmentalists. The present remedial approach to the wastewater focuses on recovering pure water for reuse and converting the contaminants into a solid matrix for permanent land disposal. However, the ground water aquifers, over a long period slowly leach the contaminants consequently polluting the ground water. Synthetic adsorbents, mainly consisting of polymeric resins, chelating agents, etc. are efficient and have high specificity, but ultimate disposal is a challenge as most of these materials are non-biodegradable. In this context, it is felt appropriate to review the utility of adsorbents based on natural green materials such as agricultural waste and restricted to few model contaminants: phenols, and heavy metals chromium(VI), and cadmium(II) in view of the vast amount of literature available. The article discusses the features of the agricultural waste material-based adsorbents including the mechanism. It is inferred that agricultural waste materials are some of the common renewable sources available across the globe and can be used as sustainable adsorbents. A discussion on challenges for industrial scale implementation and integration with advanced technologies like magnetic-based approaches and nanotechnology to improve the removal efficiency is included for future prospects.

Microplastics in mangroves and coral reef ecosystems: a review

Microplastic pollution has recently been identified as a major issue for the health of ecosystems. Microplastics have typically sizes of less than 5 mm and occur in various forms, such as pellets, fibres, fragments, films, and granules. Mangroves and coral reefs are sensitive and restricted ecosystems that provide free ecological services such as coastal protection, maintaining natural cycles, hotspots of biodiversity and economically valuable goods. However, urbanization and industrial activities have started contaminating even these preserved ecosystems. Here we review sources, occurrence, and toxicity of microplastics in the trophic levels of mangrove and coral reef ecosystems. We present detection methods, such as microscopic identification and spectroscopy. We discuss mitigating measures that prevent the entry of microplastics into the marine environment.

Electrocatalytic removal of fluroquinolones from simulated pharmaceutical effluent: Chemometric analysis, chemical blueprint of electrodes and generated sludge

Electrocatalytic removal of fluroquinolones from simulated pharmaceutical effluent is studied in this work. The effects of parameters like NaCl concentration, pH and initial concentration of Ofloxacin were studied. The synergistic effect of H₂O₂ on the degradation of Ofloxacin paves the way to move towards radical based chemistry. The process was modelled and statistically evaluated through Central Composite Design approach towards the maximum concentration of Ofloxacin degraded (for 0.8 mM) as 0.46 mM at pH-3.0 and the concentration of H₂O₂ at 0.2 mM. The model was analyzed mathematically and observed as saddle response based on canonical and ridge analysis. The process follows pseudo first order kinetics with k = 0.047 min^-1 and reaction rate of 13.6 mg.L^-1.min^-1. The mineralization efficiency of the process was studied using Total Organic Carbon analysis and 76.5% removal efficiency was obtained on the simulated pharmaceutical effluent containing Ofloxacin, Ciprofloxacin and Norfloxacin. The crystal structure of the green and red colour sludge was determined by XRD to be lepidocrocite (a = 3.87 Å, b = 12.4 Å, c = 3.06 Å) and gupeiite (a = 5.6620 Å), respectively. The elemental composition of sludge and electrodes were found using SEM-EDX. Morphological change in electrode surface was determined using roughness plot.

Influence of number of azo bonds and mass transport limitations towards the elimination capacity of continuous electrochemical process for the removal of textile industrial dyes

This study focusses on the electrochemical decomposition of synthetic azo dyes (RO16, RR120 and DR80) using stainless steel electrodes, which is efficient, cost effective and industrially driven process. The experiments were carried out in a continuous electrochemical reactor and the effects of influencing parameters (initial concentration of dye, electrolyte concentration, pH) governing the process efficiency was studied. The interaction between the influencing parameters was investigated using Response Surface Methodology (RSM) and the regression value obtained for the generated model was above 0.9 for all the three dyes. The elimination capacity of electrochemical reactor was studied for the continuous removal of azo dyes with different ranges of concentration (100-400 mg L^-1) and flow rate (0.1-0.5 L h^-1). The maximum elimination capacity was obtained at a flow rate of 0.5 L h^-1 for 300 mg L^-1 of initial concentration of dye for RO16 and RR120 whereas it was 0.5 L h^-1 for 400 mg L^-1 of DR80. Further, a general dimensionless current density relation has been established for stirred tank reactor and allowed characterizing the relationship between kinetics and mass transport contributing to the overall reaction rate. The results quantitatively confirmed that the rate of electrochemical decolorization increased with the increasing initial dye concentration and flow rate due to the mass transport limitation. As newly established, the decolorization is also directly linked to the number of azo bonds.

Process development for the degradation of textile azo dyes (mono-, di-, poly-) by advanced oxidation process - Ozonation: Experimental & partial derivative modelling approach

The present study focuses on modelling the removal of reactive azo dyes (Reactive Orange 16, Reactive Red 120 and Direct Red 80) by ozonolytic degradation. The process was optimised using One Variable at a Time (OVAT) approach followed by Response Surface Methodology (RSM). The operational parameters influencing the process of degradation, i.e. initial dye concentration (mg/L), pH and ozone exposure time were modelled using Central Composite Design (CCD). Under the optimal condition (Initial dye concentration = 2000 mg/L, pH = 11.0, Ozone exposure time = 10 min), the highest desirable response (i.e. Concentration of the degraded dye) for the degradation of RO 16, RR 120 and DR 80 are 1289.35 mg/L, 1224.98 mg/L and 1039.87 mg/L, respectively. The high correlation coefficients, 0.9814 (RO 16), 0.9815 (RR 120) and 0.9685 (DR 80) indicates the closeness of the results predicted by RSM with the experimental results. The rate of degradation for all the three dyes at the optimal condition followed pseudo-first order kinetics with the rate of reaction as 141 mg/L.min, 197.2 mg/L.min and 216.6 mg/Lmin. The predicted model was also evaluated by partial derivative-based equation modelling and experimental approach. The reliability and applicability of the developed process were confirmed by degrading the synthetic mixed dye effluent.

Fractional factorial design modelling on degradation of Direct Red 81 dye by advanced oxidation process - ozonation: reaction kinetics

In the present work, the degradation of Direct Red 81 by ozonation was studied. The interactive effects of the influencing factors (dye concentration = 500-2,000 mg/L; time = 10-30 min; pH = 7.0-11.0) on degradation efficiency was critically examined through experimental design optimization by central composite design under the response surface methodology. The high correlation coefficients (R² = 0.976 & adjusted R² = 0.958) obtained by analysis of variance (ANOVA) demonstrated close fit between the experimental and the predicted values. Optimized conditions under specified cost-driven restraints were obtained for the highest desirability (i.e. degradation of 1,210.59 mg/L dye) at pH = 11.0, initial dye concentration = 2,000 mg/L and ozone exposure time of 27.16 min. The degradation of Direct Red 81 was confirmed through Fourier transform infrared spectroscopy (FTIR) analysis and UV-Vis spectrometry.