Determining binding of sulfonamide antibiotics to CTABr micelles using semi-equilibrium dialysis

MEUF for removal and recovery of valuable organic components present in effluents: A process intensified technology

In recent years, the domain of the research space in novel separation process has been led by membrane systems as a panacea providing multifarious benefits of high separation efficiency, elimination of extreme process conditions, sustainability, and environment friendliness coupled with high operational flexibility. In this niche area, often, ultrafiltration is touted as a robust separation technique due to its high separation efficiency, membrane stability, and lower operating costs. The only drawback of relatively large pore size can be overcome by combining surfactant addition, leading to development of integrated processes termed as Micellar Enhanced Ultrafiltration. MEUF processes isolate and selectively separate valuable organics present in effluent streams. The process characteristics fit the bill as a typified example for process intensification Technology interventions for recycling of surfactants can enhance the cost-competitiveness of the process. This has the potential to develop into a broad-spectrum effluent treatment option with a change of surfactants for target contaminants. Here, in this review, we attempt to critically examine the unique features of this technology, development of spin-offs with wide-ranging applications. Specifically applications in removal of hazardous, and persistent components like dissolved organics have been critically studied. The focus was to highlight the crux of the novel technologies highlighting the efficacy and the underlying concept of process intensification. PRACTITIONER POINTS: Role of MEUF as a sustainable process intensifying separation technique for removal and recovery of organics. Novel process development using MEUF. Comparative performance analysis to assess efficacy. Discussions on future integrative process development. Sustainability aspect of MEUF with possibility of byproduct recovery.

Determining binding of polycyclic aromatic hydrocarbons to micelles formed by SDS and SOL using semi-equilibrium dialysis

Micellar enhanced ultra-filtration (MEUF) is a modified ultrafiltration (UF) method that can remove small molecules that are not effectively removed by UF alone. In this work we used a similar semi-equilibrium dialysis (SED) method to characterize two anionic surfactants, sodium dodecyl sulfate (SDS) and sodium laurate (SOL), as MEUF candidates to remove several polycyclic aromatic hydrocarbon (PAH) compounds. These anionic surfactants have low toxicity and are more biodegradable compared to the fairly toxic and persistent cetyltrimethylammonium bromide (CTABr) and similar cationic surfactants, which is important as MEUF surfactants may be present in the treated effluent. The log binding constants (Log K_B) of the PAHs naphthalene, phenanthrene, pyrene and fluorene to SDS ranged from 3.07 to 4.48, which compared well with the previous results for CTABr and indicated that SDS is an excellent candidate for MEUF. The log binding constants for the same PAHs with SOL micelles ranged from 2.11 to 3.53, which suggested that SOL might be adequate for stronger-binding PAH like pyrene and fluorene but less suitable for naphthalene and phenanthrene. The results demonstrated a strong correlation between the Log K_B with one micelle type and the Log K_B with the other, suggesting a common set of properties and interactions are responsible for the binding. Similar to the previous results for CTABr, a significant correlation between Log K_B and Log K_OW values indicates that hydrophobic character is the main driving force for PAH binding with these anionic micelles. This may also be useful for predicting MEUF performance for various compound/surfactant combinations where Log K_B is not known.

Functionalized Poly(arylene ether nitrile) Porous Membrane with High Pb(II) Adsorption Performance

Porous materials with high specific surface area possess a broad application prospect in the treatment of wastewater. In this work, sulfonated poly(arylene ether nitrile) (SPEN) functionalized with a carboxylic acid group was successfully synthesized, which was subsequently transformed into SPEN porous membranes with cetyltrimethyl ammonium bromide (CTAB) as pore-forming agents to study the adsorption performance for lead ions in aqueous solution. Then, experiments were conducted to investigate the effect of pH, contact time and initial solution concentration on the adsorption performance of porous membranes, and the adsorption capacities of porous membranes with different content (0, 5 and 15 wt %) of CTAB were 183.60, 161.73 and 127.43 mg/g, respectively, which manifested that the adsorption capacity decreased with the increase of CTAB. The adsorption capacities of porous membranes increased with the increase of the initial concentration of lead ions, and the maximum reached was 246.96 mg/g. The simulation of adsorption kinetics revealed that the adsorption was accorded with the pseudo-second-order kinetic model and Langmuir equation, indicating that the adsorption process followed Langmuir monolayer adsorption. Thermogravimetric analysis demonstrated that the porous membranes had excellent thermodynamic properties both before and after adsorption. In addition, the change of adsorption peak in the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) spectrum indicated that the absorption performance of porous membranes for lead ions benefited from the chelation between lead ions and the carboxylic acid group on SPEN. Moreover, the porous membranes maintained excellent adsorption properties after circulating five times under the conditions of acidic or alkaline, and the cycle regeneration effect was outstanding.

Determining binding of polycyclic aromatic hydrocarbons to CTABr micelles using semi-equilibrium dialysis techniques

Micellar enhanced ultrafiltration (MEUF) has been shown to be an effective removal technique for a variety of trace contaminants in wastewater, especially for water soluble low molecular weight organic contaminants. In MEUF, contaminants first partition into surfactant micelles prior to removal by ultrafiltration, where the contaminants are below the molecular weight cut-off of the ultrafiltration membrane but the micelles are above the cut-off. Binding constants of selected Polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, phenanthrene, pyrene and fluorene have been determined in order to examine the removal efficiency of MEUF for PAHs with Cetyltrimethylammonium bromide (CTABr) using a semi equilibrium dialysis method. PAHs show strong binding with CTABr because of hydrophobic interactions. Our results enabled us to develop a relationship between binding constant (log K_B) and log K_OW for neutral compounds, which will be useful for predicting MEUF performance for PAHs removal from waste water. The range of our reported binding constant values are from 2.61 to 5.07.

Sorption-desorption behavior of sulfamethoxazole, carbamazepine, bisphenol A and 17α-ethinylestradiol in sewage sludge

The occurrence of trace organic contaminants (TOrCs) at detectable levels in wastewater and surface waters led to a growing concern over the persistence of toxicological effects in the environment. Sorption is significant process in municipal wastewater treatment plants to remove TOrCs due to low water solubility and high hydrophobic of most TOrCs. The work herein explored the sorption behavior of four typical TOrCs onto sludge solids. The sorption process was spontaneous and exothermic. Greater sorption amount was observed for EE2 that 60.9% of EE2 in liquid phase was removed, followed by BPA (49.4%) and SMX (35.8%), while only 19.5% of CBZ was adsorbed. Sorption of CBZ, BPA and EE2 was primarily a physical process dominated by partition function, while SMX was mainly sorbed through multiple interactions, and this strong affinity between SMX and activated sludge resulted in least desorption rate. Deep insight into the pathway of SMX in SBR revealed that total removal rate in a period was about 50.22%. Sorption process was observed in anaerobic stage, and biological degradation was mainly occurred in aerobic stage with biodegradation rate of 29.18%.

Thermophoresis for characterizing biomolecular interaction

The study of biomolecular interactions is crucial to get more insight into the biological system. The interactions of protein-protein, protein-nucleic acids, protein-sugars, nucleic acid-nucleic acids and protein-small molecules are supporting therapeutics and technological developments. Recently, the development in a large number of analytical techniques for characterizing biomolecular interactions reflect the promising research investments in this field. In this review, microscale thermophoresis technology (MST) is presented as an analytical technique for characterizing biomolecular interactions. Recent years have seen much progress and several applications established. MST is a powerful technique in quantitation of binding events based on the movement of molecules in microscopic temperature gradient. Simplicity, free solutions analysis, low sample volume, short analysis time, and immobilization free are the MST advantages over other competitive techniques. A wide range of studies in biomolecular interactions have been successfully carried out using MST, which tend to the versatility of the technique to use in screening binding events in order to save time, cost and obtained high data quality.

DOM-mediated membrane retention of fluoroquinolone as revealed by fluorescence quenching properties

In this study, membrane filtration tests showed that the membrane rejection degree of difloxacin hydrochloride (DFHC) increased significantly in the presence of Suwannee River DOM or Aldrich humic acid (2-10 mg-C/L). Titration experiments showed that the excitation and emission of Peak R belonging to DFHC exhibited blue shifts by 5 nm and 10 nm, respectively, in the presence of DOM. The presence of DFHC can, in turn, lead to more significant overlapping of the fluorescence peaks of the Suwannee River DOM and Aldrich humic acid. The parallel factor analysis (PARAFAC) of the excitation-emission matrix (EEM) spectra can well decompose the components belonging to DFHC from the DOM + DFHC mixtures. The maximum fluorescence intensity (FI max) of the antibiotic-like component (C1) sharply decreased upon the initial addition of DOM. More specifically, the Aldrich humic acid showed a larger quenching effect on DFHC than the Suwannee River DOM. The stability constants (K M ) obtained by the Ryan and Weber model also corroborated that the Aldrich humic acid had a much higher binding stability (K M = 4.07 L/mg) than the Suwannee River DOM (K M = 0.86 L/mg). These results have great implications for our understanding of the membrane filtration behavior of trace contaminants in natural waters.

Binding of Sulfonamide Antibiotics to CTABr Micelles Characterized Using (1)H NMR Spectroscopy

Interactions of nine sulfonamide antibiotics (sulfadoxine, sulfathiazole, sulfamethoxazole, sulfamerazine, sulfadiazine, sulfamethazine, sulfacetamide, sulfaguanidine, and sulfanilamide) with cetyltrimethylamonium bromide (CTABr) micelles were examined using (1)H NMR spectroscopy. Seven of the nine provided a significant change in the (1)H NMR chemical shift such that the magnitude and direction (upfield vs downfield) of the chemical shift could be used to propose a locus and orientation of the sulfonamide within the micelle structure. The magnitude of the chemical shift was used to estimate the binding constant for seven sulfonamides with CTABr micelles, providing values and an overall pattern consistent with previous studies of these sulfonamides.