Fructose was utilized as an additional co-substrate to systematically investigate the molecular mechanism of its boosting effect for the degradation of refractory dye reactive black 5 (RB5) by a natural bacterial flora DDMZ1. A decolorizing rate of 98% was measured for sample YE + FRU(200) (with 3 g/L fructose additionally to yeast extract medium, 10% (v/v) inoculation size of flora DDMZ1, 200 mg/L RB5) after 48 h. This result was 21% and 77%, respectively, higher than those of samples with only yeast extract or only fructose. Fructose was found to significantly stimulated both intracellular and extracellular azoreductase secretion causing enhanced activity. Metagenomic sequencing technology was used to analyze the functional potential of genes. A label-free quantitative proteomic approach further confirmed the encoding of functional proteins by the candidate genes. Subsequently, the molecular mechanism of RB5 degradation by candidate genes and functional proteins of the dominant species were proposed. This study provides important perspectives to the molecular mechanism of co-metabolic degradation of refractory pollutants by a natural bacterial flora.

Kaolinite supported CoFe₂O₄ (KCF) was synthesized and employed to adsorb doxycycline (DOX), an antibiotic and Congo red (CR), a dye from aqueous solution. The prepared KCF nanocomposite was treated in a muffle furnace at 300, 500 and 700 °C, and thereafter characterized. X-ray diffractogram revealed structural damage of kaolinite and appearance of distinct peaks of CoFe₂O₄ with an increase in calcination temperature, while transmission electron microscopy (TEM) images showed that CoFe₂O₄ nanoparticles were supported on the lamellar surface of kaolinites. Comparative adsorption mechanism of the two targeted contaminants showed that adsorption of DOX was influenced by hydrogen bond and n-π interaction, while that of CR was due to hydrophobic interaction and hydrogen bond. However, the adsorption of the two contaminants was best fitted to the isotherm that was proposed by Langmuir, with a monolayer maximum adsorption capacity of 400 mg g⁻¹ at 333 K for DOX, and 547 mg g⁻¹ at 298 K for CR. The removal of DOX from aqueous solution was favored by an increase in temperature (endothermic), while that of CR was exothermic. Thermodynamics studies confirmed that the adsorption of the two contaminants is feasible and spontaneous. The presence of natural organic matter (NOM) did not affect the removal of the two contaminants. Regeneration and reusability study showed that KCF is economically viable. Therefore, introducing inorganic particles like cobalt ferrite into the matrix of kaolinites provides a composite with promising adsorption capacity.

In this study, a metal organic framework MIL-100(Fe) was synthesized for rhodamine B (RB) removal from aqueous solutions. An experimental design was conducted using a central composite design (CCD) method to obtain the RB adsorption data (n = 30) from batch experiments. In the CCD approach, solution pH, adsorbent dose, and initial RB concentration were included as input variables, whereas RB removal rate was employed as an output variable. Response surface methodology (RSM) and artificial neural network (ANN) modeling were performed using the adsorption data. In RSM modeling, the cubic regression model was developed, which was adequate to describe the RB adsorption according to analysis of variance. Meanwhile, the ANN model with the topology of 3:8:1 (three input variables, eight neurons in one hidden layer, and one output variable) was developed. In order to further compare the performance between the RSM and ANN models, additional adsorption data (n = 8) were produced under experimental conditions, which were randomly selected in the range of the input variables employed in the CCD matrix. The analysis showed that the ANN model (R² = 0.821) had better predictability than the RSM model (R² = 0.733) for the RB removal rate. Based on the ANN model, the optimum RB removal rate (>99.9%) was predicted at pH 5.3, adsorbent dose 2.0 g L−1, and initial RB concentration 73 mg L−1. In addition, pH was determined to be the most important input variable affecting the RB removal rate. This study demonstrated that the ANN model could be successfully employed to model and optimize RB adsorption to the MIL-100(Fe).

Breaking of biochar during compaction of amended soil in roadside biofilters or landfill cover can affect infiltration and pollutant removal capacity. It is unknown how the initial biochar size affects the biochar breaking, clogging potential, and contaminant removal capacity of the biochar-amended soil. We compacted a mixture of coarse sand and biochar with sizes smaller than, similar to, or larger than the sand in columns and applied stormwater contaminated with E. coli. Packing columns with biochar pre-coated with a dye and analyzing the dye concentration in the broken biochar particles eluted from the columns, we proved that biochar predominantly breaks under compaction by disintegration or splitting, not by abrasion. Increases in biochar size decrease the likelihood of biochar breaking. We attribute this result to the effective dissipation of compaction energy through a greater number of contact points between a large biochar particle and the adjacent particles. Most of the broken biochar particles are deposited in the pore spaces of the background geomedia, resulting in an exponential decrease in hydraulic conductivity of amended sand with an increase in suspended sediment loading. The clogging rate was higher in the columns with small biochar. The columns with small biochar also exhibited high E. coli removal capacity, partly because of an increase in bacterial straining at reduced pore size after compaction. These results are useful in selecting appropriate biochar size for its application in soils and roadside biofilters for stormwater treatment.

Microplastics ingested by two bivalve species Perna viridis and Meretrix meretrix collected from three estuaries viz. Ariyankuppam, Panithittu, and Chunnambar in Pondicherry, India was analysed for the first time in this research. Nile Red dye was used for microplastic detection. A survey of 50 local families was conducted to determine the frequency and quantity in which they consume mussels/clams. On an average, the number of microplastics per gram of soft tissue (wet weight) is 0.18 ± 0.04, 1.84 ± 0.61, and 1.76 ± 0.48; and the number of microplastics per bivalve is 0.50 ± 0.11, 1.75 ± 0.35, and 4.80 ± 1.39 respectively for Ariyankuppam, Panithittu, and Chunnambar. 61.02% and 77.42% of the particles belonged to the size group of <100 μm in M. meretrix and P. viridis respectively. A moderate positive correlation of r (18) = 0.6985, p < 0.05 was calculated between bivalve weight and microplastic particles. An average person belonging to the local community is likely to ingest 3917.79 ± 144.71 microplastic particles per year through mussel consumption.

The significant amount of plastic litter in the form of microplastics (size <5 mm) is garnering attention owing to its potential threat to marine life. Reliable, cost- and time-efficient analysis methods for monitoring microplastic abundance globally are still missing. Several studies proposed a fast detection method by binding the solvatochromic dye Nile Red on the surface of microplastics and using fluorescence microscopy for their detection. All the staining approaches reported so far differ in terms of Nile Red concentration, solvents, and staining procedure. Here, we compare the staining protocols published prior to 2019 and propose an optimized staining protocol. Furthermore, we explore the potential of Nile Red staining in combination with photoluminescence spectroscopy to identify the polymer type and to distinguish plastics from non-plastics.

Dyes from industrial wastewaters represent one of the most hazardous pollutants as they are not effectively biodegradable. The present work is focused to study the novel properties of keratin-polyamide blend nanofibrous filtration membranes for treating wastewaters containing dye. Keratin protein was extracted from goat hair, a tannery waste through sulphitolysis process. The extracted keratin was blended with polyamide to prepare a nanofibrous membrane through the electrospinning process. The fabricated pristine polyamide and keratin-altered polyamide membranes were characterized and compared for their properties. Effects of solution pH, dye concentration, membrane flux, and membrane capacity have been examined. Very fine nanofibers and enhanced porosity drive the membrane to enhanced flux and higher filtration efficiencies. At pH 2, the dye removal efficiency of the blend membranes was 100, 99, 98, 90, and 83% for 100, 200, 250, 300, and 400 ppm concentrations of dye, respectively. The keratin–polyamide blend membrane exhibited better properties in all aspects. The results of this present investigation indicate that the presence of keratin in filtration membranes is promising for dye removal from the effluents.

Magnetic NiₓMgyZn₍₁₋ₓ₋y₎Fe₂O₄ nanoparticles were fabricated via the ethanol-assisted combustion process. The characterizations of the nanoparticles were illuminated by SEM, EDS, XRD, and VSM. The specific surface area and pore diameter distribution were measured by the Brunauer–Emmett–Teller (BET) measurement. Magnetic Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ nanoparticles calcined at 400 °C for 2 h with anhydrous ethanol of 20 mL were chosen to remove methyl blue (MB), and their adsorption performances for removal of MB from water environment were evaluated. Adsorption kinetics and adsorption isotherm experiments had been carried out; the adsorption mechanisms were well demonstrated by the pseudo-second-order kinetics model and Temkin isotherm model, respectively, which indicated that the removal of MB by Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ adsorbent was multimolecular layer chemisorption mechanism. The pH effect of the dye solutions was explored to reveal that the adsorption capacity remained a solidly high level when pH was above 5. After three times of recycling, the relative removal activity of MB onto the nanoparticles remained above 97.6% of its original removal activity. The adsorption process of MB removed by Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ adsorbent was further illuminated by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). Graphical Abstract Magnetic Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ nanoparticles were fabricated by the ethanol-assisted combustion method, and they were chosen to remove methyl blue. Adsorption experiments were performed, and the pseudo-second-order kinetics model and the Temkin isotherm model fitted well with the experimental data. When pH was above 5, the adsorption capacity remained at a solidly high level. After three times of recycling, the relative removal activity of the nanoparticles remained above 97.6% of its original removal activity. The adsorption process was further illuminated by CV and EIS.

An iron(III)-polyvinyl chloride (PVC)-Schiff base adsorbent was prepared for removal of methyl orange (MO) as an anionic dye from the aqueous samples. PVC was reacted with ethylenediamine to prepare aminated PVC. Salicylaldehyde was then added to the aminated PVC to incorporate the Schiff base group into the polymer structure. This product was further reacted with iron (III) nitrate to form an iron complex as the modified PVC adsorbent (PVC-[Fe(EDA)(Sald)]). The prepared adsorbent was characterized by Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET) surface area analysis, and thermogravimetric analysis (TGA). The special parameters influencing the adsorption process such as the solution pH, contact time, initial dye concentration, and the solution temperature were investigated. Removal percentage (%R) and adsorption capacity (qₜ) greater than 50% and 140 mg g⁻¹, respectively, were obtained under the following conditions: pH, 7;contact time, 150 min; dye concentration, 100 mg.L⁻¹; and solution temperature, 25 °C. The adsorption isotherm and kinetic data were well fitted by the Freundlich isotherm model and the pseudo-second-order kinetic model, respectively. The thermodynamic data revealed that the adsorption process was endothermic and spontaneous. The changes in entropy (ΔS°) and enthalpy (ΔH°) were calculated to be 0.110 kJ mol⁻¹ K⁻¹ and 31.011 kJ mol⁻¹, respectively. In this work, we developed for the first time the synthesis of an iron(III)-polyvinyl chloride (PVC)-Schiff base adsorbent that can be successfully used for removal of methyl orange from the aqueous sample. Furthermore, these findings showed that modified PVC was more efficient than neat PVC on MO removal for adsorption process.

The concern with the environment and the depletion of natural resources has aroused the interest for the rational use and recycling of water. Therefore, this study evaluated the capacity of the Trametes sp. M3 isolate in the bioremediation of Reactive Blue (RB) 268 dye and its potential for use as an adsorbent in the treatment of textile effluents. In a solid medium containing RB 268, the discoloration rate was 1.00 and the growth rate was 1.4 cm/day. When evaluated in the in vivo biodiscoloration process, 100% of the dye lost its color after 120 h. The oxidative enzyme laccase was found in cultures containing the dye with high activity, indicating that it underwent induction. The chromatogram after cultivation of the fungus showed that there was a change in the structure of RB 268. The mycelium of the culture with the dye was analyzed by FTIR, pointing to an adsorption of RB 268 or its metabolites despite the absence of the color. In the biosorption, the best results were obtained when the mycelium was treated with HCl. The toxicity of the medium decreased after the cultivation of the fungus allowing the survival of the microcrustaceans in the acute toxicity bioassay.