Removal of calcium ions from aqueous solution by bovine serum albumin (BSA)-modified nanofiber membrane: Dynamic adsorption performance and breakthrough analysis

Non-destructive monitoring and prediction of fouling by organic matters and residual anionic coagulant during membrane process

Physical fouling characteristics on silicon carbide (SiC) membranes induced by various organic matter compounds vary depending on the presence of calcium ions (Ca2+). Both destructive techniques (morphological surface analysis) and non-destructive techniques (fouling properties monitoring) were used to determine the fouling mechanisms and behavior during the membrane filtration systems. Destructive analysis and a modified Hermia model were employed to assess the fouling mechanisms. Fouling behavior was also analyzed through non-destructive monitoring techniques including optical coherence tomography (OCT) and three-dimensional laser scanning confocal microscopy (3D-LSM). At concentrations of 10, 30, and 100 mg/L without Ca2+, the flux decreased by 57-95% for humic acid (HA) and anionic polyacrylamide (APAM). APAM exhibited a notable removal rate of up to 56% without Ca2+. At concentration of 10, 30, and 100 mg/L in the absence of Ca2+, the flux decreased by 6-8% for sodium alginate (SA). However, the addition of Ca2+ led to a reduction in the flux for SA by up to 91% and resulted in a removal rate of 40%. Furthermore, addition of Ca2+ led to an alteration of the fouling characteristics of HA and SA. In the case of HA, higher concentrations resulted in elevated thickness and roughness with correlation coefficients of 0.991 and 0.992, respectively. For SA, increased SA concentration led to a thicker (correlation coefficient of 0.999) but smoother surfaces (correlation coefficients of 0.502). Monitoring of these physical characteristics of the fouling layer through non-destructive analysis is crucial for effective fouling management, optimization of the system performance and extending the lifespan of the membrane. By continuously assessing the fouling layer thickness and surface roughness, we expect to be able to provide insights on the fouling behavior, identify trends, that can help scientists and engineers to make informed decisions regarding fouling control strategies in future.

Breakthrough Curve Modeling and Analysis for Lysozyme Adsorption by Tris(hydroxymethyl)aminomethane Affinity Nanofiber Membrane

In this study, a polyacrylonitrile nanofiber membrane was first hydrolyzed and then functionalized with tris(hydroxymethyl)aminomethane (P-Tris), then used as an affinity nanofiber membrane for lysozyme adsorption in membrane chromatography. The dynamic adsorption behavior of lysozyme was investigated in a flow system under various operating parameters, including adsorption pHs, initial feed lysozyme concentration, loading flow rate, and the number of stacked membrane layers. Four different kinetic models, pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion kinetic models, were applied to experimental data from breakthrough curves of lysozyme. The results showed that the dynamic adsorption results were fitted well with the pseudo-second-order kinetic model. The breakthrough curve experimental results show significant differences in the breakthrough time, the dynamic binding capacity, the length of the mass transfer zone, and the utilization rate of the membrane bed under different operating parameters. Four dynamic adsorption models (i.e., Bohart-Adams, Thomas, Yoon-Nelson, and BDST models) were used to analyze the breakthrough curve characteristics of the dynamic adsorption experiments. Among them, the Yoon-Nelson model was the best model to fit the breakthrough curve. However, some of the theoretical results based on the Thomas and Bohart-Adams model analyses of the breakthrough curve fit well with the experimental data, with an error percentage of <5%. The Bohart-Adams model has the largest difference from the experimental results; hence it is not suitable for breakthrough curve analysis. These results significantly impact dynamic kinetics studies and breakthrough curve characteristic analysis in membrane bed chromatography.

Reactive Green 19 dye-ligand immobilized on the aminated nanofiber membranes for efficient adsorption of lysozyme: Process development and optimization in batch and flow systems

The performance of lysozyme adsorption by the aminated nanofiber membrane immobilized with Reactive Green 19 (RG19) dyes was evaluated in batch and flow systems. The physicochemical properties of the dye-immobilized nanofiber membrane were characterized. The parameters of batch-mode adsorption of lysozyme (e.g., pH, initial dye concentration, and lysozyme concentration) were optimized using the Taguchi method. In a flow process, the factors influencing the dynamic binding performance for lysozyme adsorption in the chicken egg white (CEW) solution include immobilized dye concentration, adsorption pH value, feed flow rate, and feed CEW concentration. The impact of these operating conditions on the lysozyme purification process was investigated. Under optimal conditions, the recovery yield and purification factor of lysozyme achieved from the one-step adsorption process were 98.52% and 143 folds, respectively. The dye-affinity nanofiber membrane also did not exhibit any significant loss in its binding capacity and purification performance after five consecutive uses.

Dual-layer Janus charged nanofiltration membranes constructed by sequential electrospray polymerization for efficient water softening

The separation of hardness ions such as calcium and magnesium from hard water can improve water quality, which is important but technically challenging. Nanofiltration (NF) has attracted much attention because of its efficiency, environmental friendliness and low cost. However, common NF membranes with a singly (either positively or negatively) charged layer have insufficient water softening capacity. In this work, two types of dual-layer Janus charged polyamide NF membranes composed of oppositely charged inner and outer layers were developed for the first time by sequential electrospray polymerization strategy for efficient water softening. The effect of the microstructure of the dually charged barrier layer on the separation performance of divalent salt ions was explored. Detailed mechanistic studies revealed that the microstructure of the outer layer of the barrier layer played a crucial role in the ion separation of the Janus membrane due to its control of the reverse transport of ions. Janus charged polyamide NF membrane with a loose outer layer exhibited better water softening performance (93.6% of hardness removed) compared to the singly charged NF membranes due to the simultaneous dual electrostatic effect and no ion reverse transport confinement. This Janus charged NF membrane also possessed good antifouling performance, mainly due to its negatively charged outer layers. The mechanistic insights gained in this study reveal the huge potential of microstructural design toward high-performance Janus charged NF membranes, and provide important guidance on the future development of high-efficiency water softening NF membranes.

Recent development and application of membrane chromatography

Membrane chromatography is mainly used for the separation and purification of proteins and biological macromolecules in the downstream processing process, also applications in sewage disposal. Membrane chromatography is recognized as an effective alternative to column chromatography because it significantly improves chromatography from affinity, hydrophobicity, and ion exchange; the development status of membrane chromatography in membrane matrix and membrane equipment is thoroughly discussed, and the applications of protein capture and intermediate purification, virus, monoclonal antibody purification, water treatment, and others are summarized. This review will provide value for the exploration and potential application of membrane chromatography.

Emerging nanotechnology based advanced techniques for wastewater treatment

The increasing trend of industrialization leads to tremendous release of industrial effluents. Waste water treatment is one of the important sectors to focus in order to overcome the most threatening issue of waste disposal and to ensure sustainability. Sustainable and energy efficient treatment methods are the attractive technologies for their current implementation of waste management. Even though the existing technologies are effective, unsustainability makes them unfit for their extended applications. Conventional and advanced technologies have been extensively implemented for the treatment of wide spectrum of effluents. Hybrid technologies including chemical and biological methods also emerging as promising technologies but secondary sludge generation is still unaddressed. Even though effectiveness of biochar varies over type of contaminants, cost-effectiveness and eco-friendly nature extended their applications in waste management. Nanotechnology and membrane technology are the promising and emerging areas of interest due to their widespread applications in waste water treatment. Carbon nano structures, nano filters, graphene, nano magnets modified with activated carbon are the potential candidates for the treatment. The present review demonstrates the emerging treatment technologies with special focus to nano based waste water treatment methods.

Modeling of Hexavalent Chromium Removal with Hydrophobically Modified Cellulose Nanofibers

Cellulose nanofibers (CNF) are sustainable nanomaterials, obtained by the mechanical disintegration of cellulose, whose properties make them an interesting adsorbent material due to their high specific area and active groups. CNF are easily functionalized to optimize the performance for different uses. The hypothesis of this work is that hydrophobization can be used to improve their ability as adsorbents. Therefore, hydrophobic CNF was applied to adsorb hexavalent chromium from wastewater. CNF was synthetized by TEMPO-mediated oxidation, followed by mechanical disintegration. Hydrophobization was performed using methyl trimetoxysilane (MTMS) as a hydrophobic coating agent. The adsorption treatment of hexavalent chromium with hydrophobic CNF was optimized by studying the influence of contact time, MTMS dosage (0-3 mmol·g^-1 CNF), initial pH of the wastewater (3-9), initial chromium concentration (0.10-50 mg·L^-1), and adsorbent dosage (250-1000 mg CNF·L^-1). Furthermore, the corresponding adsorption mechanism was identified. Complete adsorption of hexavalent chromium was achieved with CNF hydrophobized with 1.5 mmol MTMS·g^-1 CNF with the faster adsorption kinetic, which proved the initial hypothesis that hydrophobic CNF improves the adsorption capacity of hydrophilic CNF. The optimal adsorption conditions were pH 3 and the adsorbent dosage was over 500 mg·L^-1. The maximum removal was found for the initial concentrations of hexavalent chromium below 1 mg·L^-1 and a maximum adsorption capacity of 70.38 mg·g^-1 was achieved. The kinetic study revealed that pseudo-second order kinetics was the best fitting model at a low concentration while the intraparticle diffusion model fit better for higher concentrations, describing a multi-step mechanism of hexavalent chromium onto the adsorbent surface. The Freundlich isotherm was the best adjustment model.

Studies of Protein Wastes Adsorption by Chitosan-Modified Nanofibers Decorated with Dye Wastes in Batch and Continuous Flow Processes: Potential Environmental Applications

In this study, reactive green 19 dye from wastewater was immobilized on the functionalized chitosan nanofiber membranes to treat soluble microbial proteins in biological wastewater. Polyacrylonitrile nanofiber membrane (PAN) was prepared by the electrospinning technique. After heat treatment, alkaline hydrolysis, and chemically grafted with chitosan to obtain modified chitosan nanofibers (P-COOH-CS), and finally immobilized with RG19 dye, dyed nanofibers were generated (P-COOH-CS-RG19). The synthesis of P-COOH-CS and P-COOH-CS-RG19 are novel materials for protein adsorption that are not deeply investigated currently, with each of the material functions based on their properties in significantly improving the adsorption efficiency. The nanofiber membrane shows good adsorption capacity and great recycling performance, while the application of chitosan and dye acts as the crosslinker in the nanofiber membrane and consists of various functional groups to enhance the adsorption of protein. The dyed nanofibers were applied for the batch adsorption of soluble protein (i.e., lysozyme), and the process parameters including chitosan’s molecular weight, coupling pH, chitosan concentration, dye pH, dye concentration, and lysozyme pH were studied. The results showed that the molecular weight of chitosan was 50 kDa, pH 5, concentration 0.5%, initial concentration of dye at 1 mg/mL dye and pH 12, lysozyme solution at 2 mg/mL at pH 8, and the maximum adsorption capacity was 1293.66 mg/g at a temperature of 318 K. Furthermore, thermodynamic, and kinetic studies suggested that the adsorption behavior of lysozyme followed the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model. The optimal adsorption and desorption conditions based on batch experiments were directly applied to remove lysozyme in a continuous operation. This study demonstrated the potential of dyed nanofibers as an efficient adsorbent to remove approximately 100% of lysozyme from the simulated biological wastewater.

Adsorption behavior of fluoroquinolone(ciprofloxacin) using zinc oxide impregnated activated carbon prepared from jack fruit peel: Kinetics and isotherm studies

Ciprofloxacin is a pharmaceutical component used for treating various tract infections. This is considered as an emerging contaminant due to the release of unreacted components getting disposed into the water bodies. This component is effectively treated using renewable biomass, which is converted into a useful renewable low-cost adsorbent material. Discarded Jack Fruit Peel (JFP) is used as an activated carbon incorporated with zinc oxide nanocomposite. The prepared activated carbon in this experiment was characterized by determining their functional groups, morphological characters, and nature of the adsorbent material by analyzing the Fourier Transform InfraRed (FTIR), Field Emission Scanning Electron Microscopy (FESEM), and X-ray Diffraction (XRD) characterization. Further, the prepared composite's correlation coefficients and equilibrium sorption of the adsorption process were calculated using Ultra Violet (UV)-Visible Spectroscopy and analyzed with isotherm models (Langmuir model, Freundlich model, and Temkin model) and kinetic models (Pseudo-first-order kinetics, Pseudo-second-order kinetics, Intraparticle diffusion model, and Elovich model). Among the different models, the Zinc oxide impregnated activated carbon show Freundlich Isotherm and Pseudo Second order equation having a maximum correlation with experimental studies indicating double-layer adsorption, which suggests that the process is chemisorption. The operational parameters, including the effect of pH, dosage of activated carbon, and contact time of adsorption was calculated to identify the optimal condition for maximum adsorption.

Design and characterization of small-diameter tissue-engineered blood vessels constructed by electrospun polyurethane-core and gelatin-shell coaxial fiber

Substitution or bypass is the most effective treatment for vascular occlusive diseases.The demand for artificial blood vessels has seen an unprecedented rise due to the limited supply of autologous blood vessels. Tissue engineering is the best approach to provide artificial blood vessels. In this study, a new type of small-diameter artificial blood vessel with good mechanical and biological properties was designed by using electrospinning coaxial fibers. Four groups of coaxial fibers vascular membranes having polyurethane/gelatin core-shell structure were cross-linked by the EDC-NHS system and characterized. The core-shell structure of the coaxial vascular fibers was observed by transmission electron microscope. After the crosslinking, the stress and elastic modulus increased and the elongation decreased, burst pressure of 0.11 group reached the maximum (2844.55 ± 272.65 mmHg) after cross-linking, which acted as the experimental group. Masson staining identified blue-stained ring or elliptical gelatin ingredients in the vascular wall. The cell number in the vascular wall of the coaxial group was found in muscle embedding experiment significantly higher than that of the non-coaxial group at all time points(p < 0.001). Our results showed that the coaxial vascular graft with the ratio of 0.2:0.11 had better mechanical properties (burst pressure reached 2844.55 ± 272.65 mmHg); Meanwhile its biological properties were also outstanding, which was beneficial to cell entry and offered good vascular remodeling performance.Polyurethane (PU); Gelatin (Gel); Polycaprolactone (PCL); polylactic acid (PLA);1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC); N-Hydroxy succinimide (NHS); 4-Morpholine-ethane-sulfonic (MES); phosphate buffered saline (PBS); fetal calf serum (FCS); Minimum Essential Medium (MEM); Dimethyl sulfoxide (DMSO); hematoxylin-eosin (HE).