Efficient removal of chemically toxic dyes using microorganism from activated sludge: Understanding sorption mechanism, kinetics, and associated thermodynamics

Theoretical analysis and application of immobilized methanotrophs as typical adsorbent materials for adsorption/degradation of trichloroethylene

Trichloroethylene (TCE) contamination presents a significant environmental challenge, necessitating efficient treatment solutions. This study aimed to develop an optimized immobilized bioreactor using methanotrophs for TCE degradation. Activated carbon fibres were identified as the optimal immobilization material, with an adsorption rate of 6-23 h - significantly faster than over 50 h for other materials - and the highest methane oxidation capacity of 0.970 mL·g-1·h-1. Adsorption kinetics indicated that activated carbon fibres followed a second-order kinetic model with a constant of 0.598 g·mg-1·h-1, suitable for low-concentration bacterial solutions. Thermodynamic analysis confirmed an exothermic process, favouring lower temperatures (288.15 K). The negative interaction energies, as per DLVO theory, suggested electrostatic attraction as a key mechanism. The bioreactor achieved 99% TCE removal within 1 h at an initial concentration of 10 mg·L-1, with visible microbial immobilization within 5 days. This research provides a novel and effective approach for using immobilized methane-oxidizing bacteria in TCE treatment, offering both theoretical and practical advancements for chlorinated hydrocarbon wastewater management.

Carbonate treated coffee powder (CTCP) for selective sorption of Pu4+ over Am3+, Np4+, NpO22+, and PuO22+ from aqueous acidic solution: Investigation on mechanism, kinetics, thermodynamics, stripping and radiolytic stability

An attempt was made for understanding the sorption behaviour of different actinide ions Pu⁴⁺, PuO₂²⁺, Am³⁺, Np⁴⁺, and NpO₂²⁺ on carbonate treated exhausted coffee powder (CTCP). Very efficient sorption of Pu⁴⁺ over other actinide ions from aqueous acidic medium was observed. Almost 4 h were required for achieving equilibrium. Experimental results for Pu⁺⁴ were fitted into different sorption isotherm model: Langmuir isotherm, Freundlich isotherm, D.R, isotherm and Temkin isotherm. Based on the linear regression, it was found that, Freundlich isotherm was predominantly operative. Pseudo 2nd order kinetics was found to be effective for the sorption of Pu⁺⁴. More than 80 % of loaded Pu⁴⁺ was found to desorb by 0.25 M oxalic acid solution. CTCP exhibited relatively good radiation stability. Sorption of Pu⁺⁴ on CTCP was exothermic, and spontaneous in nature. The sorption process was simple, cost effective and environmentally benign, as it did not involve any sophisticated, multi-step, sorbent synthesis.

Azo-Dye-Functionalized Polycarbonate Membranes for Textile Dye and Nitrate Ion Removal

Challenges exist in the wastewater treatment of dyes produced by the world’s growing textiles industry. Common problems facing traditional wastewater treatments include low retention values and breaking the chemical bonds of some dye molecules, which in some cases can release byproducts that can be more harmful than the original dye. This research illustrates that track-etched polycarbonate filtration membranes with 100-nanometer diameter holes can be functionalized with azo dye direct red 80 at 1000 µM, creating a filter that can then be used to remove the entire negatively charged azo dye molecule for a 50 µM solution of the same dye, with a rejection value of 96.4 ± 1.4%, at a stable flow rate of 114 ± 5 µL/min post-functionalization. Post-functionalization, Na⁺ and NO3⁻ ions had on average 17.9%, 26.0%, and 31.1% rejection for 750, 500, and 250 µM sodium nitrate solutions, respectively, at an average flow rate of 177 ± 5 µL/min. Post-functionalization, similar 50 µM azo dyes had increases in rejection from 26.3% to 53.2%. Rejection measurements were made using ultraviolet visible-light spectroscopy for dyes, and concentration meters using ion selective electrodes for Na⁺ and NO3⁻ ions.

Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.

Novel Poly(ionic liquid) Augmented Membranes for Unconventional Aqueous Phase Applications in Fractionation of Dyes and Sugar

Poly(ionic) liquid (PIL) augmented membranes were fabricated through self-polymerization of 2-vinyl pyridine and 4-vinyl pyridine followed by dopamine triggered polymerization and bridging with inert polyamide support. The resulting membranes acquired a positive surface charge with a high degree of hydrophilicity. Fourier transformed Infra-red (FTIR) and Energy dispersive X-ray (EDX) spectroscopic investigation revealed the successful augmentation of PIL surface layer, whereas surface morphology was investigated through scanning electron microscopy (SEM) imaging. This manuscript demonstrates pi electron-induced separation of dyes with the trend in permeability: Coomassie Brilliant Blue G (CBBHG) > Remazol Brilliant Blue R (RBBR) > Eichrome Black T (EBT) > Congo Red (CR). CBBG exhibited extended conjugation over large aromatic domain. RBBR and EBT were associated withtheelectron-donating -NH2 group and electron-withdrawing -NO2 group, respectively, hence pi electron density on aromatic ring varied. The steric repulsion between two pairs of ortho hydrogens (Hs) in biphenyl moieties of CR resulted in deviation of planarity and hence aromaticity leading to the lowest permeability. The sugar fractionation followed the trend: Galactose > Mannose > Fructose > Glucose > Xylose. More hydroxyl (-OH) groups in sugars and their conformational alignment in the same direction, exhibited more lone pair of electrons leading to more interaction with PIL and hence better permeability. Pentose showed poorer permeation than hexose, whereas aldose showed better permeation than ketose.

Guar gum based nanocomposites: Role in water purification through efficient removal of dyes and metal ions

Researchers nowadays are relentlessly on a race exploring sustainable materials and techniques for the sequestration of toxic dyes and metal ions from water bodies. Biopolymers such as guar gum, owing to its high abundance, low cost and non-toxicity, are potential candidates in this field. Plenty of hydroxyl groups in the polymer backbone enable guar gum to be functionalised or grafted in a versatile manner proving itself as an excellent starting substance for fabricating upgraded materials meant for diverse applications. This review offers a comprehensive coverage of the role of guar gum-based nanocomposites in removal of dyes and heavy metal ions from waste water through adsorption and photo-catalytic degradation. Isotherm and kinetics models, fabrication routes, characterisation techniques, swelling properties and reusability as well as adsorption and degradation mechanisms are outlined. A detailed analysis with convincing results suggests a good future perspective of implementation of these materials in real-time wastewater treatment technology.

Designing Electric Field Responsive Ultrafiltration Membranes by Controlled Grafting of Poly (Ionic Liquid) Brush

Electric responsive membranes have been prepared by controlled surface grafting of poly (ionic liquid) (PIL) on the commercially available regenerated cellulose ultrafiltration membrane. The incorporation of imidazolium ring on membrane surface was evidenced by FTIR (Fourier transformed infra-red) and EDX (energy-dispersive X-ray) spectroscopy. The PIL grafting resultedin a rougher surface, reduction in pore size, and enhancement in hydrophilicity. The interaction of the electric field between the charged PIL brush and the oscillating external electric field leads to micromixing, and hence it is proposed to break the concentration polarization. This micromixing improves the antifouling properties of the responsive membranes. The local perturbation was found to decrease the water flux, while it enhanced protein rejection. At a higher frequency (1kHz) of the applied electric field, the localized heating predominates compared to micromixing. In the case of a lower frequency of the applied electric field, more perturbation can lead to less permeability, whereas it will have a better effect in breaking the concentration polarization. However, during localized heating at a higher frequency, though perturbation is less, a heating induced reduction in permeability was observed. The electric field response of the membrane was found to be reversible in nature, and hence has no memory effect.

Synergistic Degradation of Dye Wastewaters Using Binary or Ternary Oxide Systems with Immobilized Laccase

In recent years, groundwater contamination caused by dyes has become an important problem. They enter into wastewater as a result of the textile, automotive, or cosmetics industries. For this reason, new methods are being sought, which would aid at the removal of dye impurities with high efficiency and also would be relatively cheap. In the presented study synthesized TiO2-ZrO2 (with TiO2:ZrO2 molar ratio of 8:2) and TiO2-ZrO2-SiO2 (with TiO2:ZrO2:SiO2 molar ratio of 8:1:1) oxide materials were used as supports for enzyme immobilization. Effective synthesis of the carriers was confirmed by results of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), low-temperature nitrogen sorption and Fourier transform infrared spectroscopy (FTIR). The materials achieve high immobilization efficiency of the laccases from Trametes versicolor (83% and 96% for TiO2-ZrO2-laccase and TiO2-ZrO2-SiO2-laccase, respectively). The effect of selected dye concentrations, pH, temperature, and reusability were also tested. The obtained results showed that after removal of textile dyes, such as Alizarin Red S (ARS), Remazol Brilliant Blue R (RBBR), and Reactive Black 5 (RB5), under optimal process conditions, which were pH 5 and 25 °C, from dye solution of 5 mg/L degradation efficiency reached 100%, 91%, and 77%, respectively, suggesting synergistic mechanism of degradation by simultaneous sorption and catalytic action. Finally, reduction of chemical oxygen demand (COD) of the solution after treatment indicated lower mixture toxicity and effective dye degradation.

Surface Oxidation of Ethylenechlorotrifluoroethylene (ECTFE) Membrane for the Treatment of Real Produced Water by Membrane Distillation

Modification of ethyleneechlorotrifluoroethylene (ECTFE) membranes by simple surface oxidation was reported in the present investigation in order to induce thin hydrophilic layer on hydrophobic membrane surface for the treatment of real produced water (PW). FTIR spectra indicates the appearance of hydrophilic functional groups (⁻OH and ⁻COOH) on the membrane surface due to modification, while water contact angle, zeta potential measurement, EDX, XPS analysis confirmed the presence of O functionalized hydrophilic groups on the surface. The effect of modification temperature and the time of surface oxidation on the performance of the resulting membranes were studied systematically, which revealed that induction of optimized hydrophilicity can successfully reduce the organic fouling. However, too much hydrophilic surface induces polar/electrostatic interaction resulting salt deposition on membrane surface. A simple on site cleaning procedure was demonstrated to be successful for the treatment PW for at least three consecutive cycles of membrane distillation (MD).