TETA-anchored graphene oxide enhanced polyamide thin film nanofiltration membrane for water purification; performance and antifouling properties.

This work investigates the performance and structure of polyamide thin film nanocomposite (PA-TFN) membrane incorporated with triethylenetetramine-modified graphene oxide (GO-TETA). The embedment of GO-TETA nanosheets within the structure of PA-TFN membrane was evaluated at different concentrations (0.005, 0.01, 0.03 wt%; in aqueous piperazine (PIP)) through interfacial polymerization (IP). The physicochemical properties of the prepared membrane were investigated by SEM, AFM, water contact angle, and zeta potential as well as ATR-IR spectroscopy. The presence of longer chains of amino groups (in comparison with the directly linked amino ones) among the stacked GO nanosheets was assumed to increase interlayer spacing, resulting in remarkable changes in water permeance and separation behavior of modified polyamide (PA) membrane. It is seen that GO-TETA nanosheets were uniformly distributed in the matrix of PA layer. With increasing the concentration of GO-TETA, the flux of TFN membranes under 6 bar was increased from 49.8 l/m2 h (no additive) to 73.2 l/m2 h (TFN comprising 0.03 wt% GO-TETA. In addition, more loading GO-TETA resulted in a significant decrease in the average thickness of the polyamide layer from ~380 to ~150 nm. Furthermore, addition of GO-TETA improved the hydrophilicity of nanocomposite membranes, resulting in superb water flux recovery (antifouling indicator) as high as 95% after filtration of bovine serum albumin solution. Also, the retention capability of the TFN membranes towards some textile dyes increased as high as 99.6%.

Simultaneous Improvement of Antimicrobial, Antifouling, and Transport Properties of Forward Osmosis Membranes with Immobilized Highly-Compatible Polyrhodanine Nanoparticles.

This work shows that incorporating highly compatible polyrhodanine nanoparticles (PRh-NPs) into a polyamide (PA) active layer allows for fabricating forward osmosis (FO) thin-film composite (TFC)-PRh membranes that have simultaneously improved antimicrobial, antifouling, and transport properties. To the best of our knowledge, this is the first reported study of its kind to this date. The presence of the PRh-NPs on the surface of the TFC-PRh membranes active layers is evaluated using FT-IR spectroscopy, SEM, and XPS. The microscopic interactions and their impact on the compatibility of the PRh-NPs with the PA chains were studied using molecular dynamics simulations. When tested in forward osmosis, the TFC-PRh-0.01 membrane (with 0.01 wt % PRh) shows significantly improved permeability and selectivity because of the small size and the high compatibility of the PRh-NPs with PA chains. For example, the TFC-PRh-0.01 membrane exhibits a FO water flux of 41 l/(m2·h), higher than a water flux of 34 l/(m2·h) for the pristine TFC membrane, when 1.5 molar NaCl was used as draw solution in the active-layer feed-solution mode. Moreover, the reverse solute flux of the TFC-PRh-0.01 membrane decreases to about 115 mmol/(m2·h) representing a 52% improvement in the reverse solute flux of this membrane in comparison to the pristine TFC membrane. The surfaces of the TFC-PRh membranes were found to be smoother and more hydrophilic than those of the pristine TFC membrane, providing improved antifouling properties confirmed by a flux decline of about 38% for the TFC-PRh-0.01 membranes against a flux decline of about 50% for the pristine TFC membrane when evaluated with a sodium alginate solution. The antimicrobial traits of the TFC-PRh-0.01 membrane evaluated using colony-forming units and fluorescence imaging indicate that the PRh-NPs hinder cell deposition on the TFC-PRh-0.01 membrane surface effectively, limiting biofilm formation.

Mitigation of Thin-Film Composite Membrane Biofouling via Immobilizing Nano-Sized Biocidal Reservoirs in the Membrane Active Layer.

This work investigates the use of a silver-based metal-organic framework (MOF) for mitigating biofouling in forward-osmosis thin-film composite (TFC) membranes. This is the first study of the use of MOFs for biofouling control in membranes. MOF nanocrystals were immobilized in the active layer of the membranes via dispersion in the organic solution used for interfacial polymerization. Field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) characterization results showed the presence of the MOF nanocrystals in the active layer of the membranes. The immobilization improved the membrane active layer in terms of hydrophilicity and transport properties without adversely affecting the selectivity. It imparted antibacterial activity to the membranes; the number of live bacteria attached to the membrane surface was over 90% less than that of control membranes. Additionally, the MOF nanocrystals provided biocidal activity that lasted for 6 months. The immobilization improved biofouling resistance in the membranes, whose flux had a decline of 8% after 24 h of operation in biofouling experiments, while that of the control membranes had a greater decline of ∼21%. The better biofouling resistance is due to simultaneous improvement of antiadhesive and antimicrobial properties of the membranes. Fluorescence microscopy and FE-SEM indicated simultaneous improvement in antiadhesive and antimicrobial properties of the TFN membranes, resulting in limited biofilm formation.

Mixed matrix membrane application for olive oil wastewater treatment: process optimization based on Taguchi design method.

Olive oil mill wastewater (OMW) is a concentrated effluent with a high organic load. It has high levels of organic chemical oxygen demand (COD) and phenolic compounds. This study presents a unique process to treat OMW. The process uses ultrafiltration (UF) membranes modified by a functionalized multi wall carbon nano-tube (F-MWCNT). The modified tube has an inner diameter of 15-30 nm and is added to the OMW treatment process to improve performance of the membrane. Tests were done to evaluate the following operating parameters of the UF system; pressure, pH and temperature; also evaluated parameters of permeate flux, flux decline, COD removal and total phenol rejection. The Taguchi robust design method was applied for an optimization evaluation of the experiments. Variance (ANOVA) analysis was used to determine the most significant parameters affecting permeate flux, flux decline, COD removal and total phenols rejection. Results demonstrated coagulation and pH as the most important factors affecting permeate flux of the UF. Moreover, pH and F-MWCNT UF had significant positive effects on flux decline, COD removal and total phenols rejection. Based on the optimum conditions determined by the Taguchi method, evaluations for permeate flux tests; flux decline, COD removal and total phenols rejection were about 21.2 (kg/m(2) h), 12.6%, 72.6% and 89.5%, respectively. These results were in good agreement with those predicted by the Taguchi method (i.e.; 22.8 (kg/m(2) h), 11.9%, 75.8 and 94.7%, respectively). Mechanical performance of the membrane and its application for high organic wastewater treatment were determined as strong.

Comprehensive Characterization of Commercial Reverse Osmosis Membranes through High-Temperature Cross-Flow Filtration.

Developing thermally stable reverse osmosis membranes is a potential game-changer in high-temperature water treatment. In this work, the performance of three commercial reverse osmosis membranes was evaluated with a series of high-temperature filtrations. The membranes were tested with different filtration methodologies: long-term operation, cyclic tests, controlled stepwise temperature increment, and permeability tests. The morphological and physiochemical characterizations were performed to study the impact of high-temperature filtration on the membranes' chemical composition and morphological characteristics. An increase in the temperature deteriorated the membrane performance in terms of water flux and salt rejection. Flux decline at high temperatures was recognized as the primary concern for high-temperature filtrations, restricting the applications of commercial membranes for long-term operations. This research provides valuable insights for researchers aiming to thoroughly characterize reverse osmosis membranes at high temperatures.

A new concept in polymeric thin-film composite nanofiltration membranes with antibacterial properties.

A new, thin film, biofouling resistant, nanofiltration (NF) membrane was fabricated with two key characteristics, viz. a low rate of silver (Ag) release and long-lasting antibacterial properties. In the new approach, nanoparticles were embedded completely in a polymeric thin-film layer. A comparison was made between the new thin-film composite (TFC), NF membrane and thin-film nanocomposite (TFN), and antibacterial NF membranes. Both types of NF membrane were fabricated by interfacial polymerization on a polysulphone sublayer using m-phenylenediamine and trimesoyl chloride as an amine monomer and an acid chloride monomer, respectively. Energy dispersive X-ray (EDX) microanalysis demonstrated the presence of Ag nanoparticles. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to study the cross-sectional and surface morphological properties of the NF membranes. Permeability and salt rejection were tested using a dead-end filtration cell. Ag leaching from the membranes was measured using inductively coupled mass spectrometry (ICP-MS). Morphological studies showed that the TFC NF membranes had better thin-film formation (a more compact structure and a smoother surface) than TFN NF membranes. Performance experiments on TFC NF membranes revealed that permeability was good, without sacrificing salt rejection. The antibacterial properties of the fabricated membranes were tested using the disk diffusion method and viable plate counts. The antibiofouling properties of the membranes were examined by measuring the quantity of bacterial cells released from the biofilm formed (as a function of the amount of biofilm present). A more sensitive surface was observed compared to that of a typical antibacterial NF membrane. The Ag leaching rates were low, which will likely result in long-lasting antibacterial and biofouling resistant properties.

"Biomass to Membrane": Sulfonated Kraft Lignin/PCL Superhydrophilic Electrospun Membrane for Gravity-Driven Oil-in-Water Emulsion Separation.

Biobased membranes made with green solvents have numerous advantages in the water purification industry; however, their long-term use is impeded by severe membrane fouling and low structural stability. Herein, we proposed a facile and green approach to fabricate an eco-friendly and biodegradable electrospun membrane by simply blending polycaprolactone (PCL) with sulfonated kraft lignin (SKL) in a green solvent (i.e., acetic acid) without needing any additional post-treatment. We investigated the influence of SKL content on the surface morphology, chemical composition, and mechanical properties of the electrospun membrane. The SKL-modified membranes (L-5 and L-10) showed superhydrophilicity and underwater superoleophobicity with a water contact angle (WCA) of 0° (<3 s) and an underwater-oil contact angle (UWOCA) over 150° due to the combined effect of surface roughness and hydrophilic chemical functionality. Furthermore, the as-prepared membranes demonstrated excellent pure water flux of 800-900 LMH and an emulsion flux of 170-480 LMH during the gravity-driven filtration of three surfactant-stabilized oil-in-water emulsions, namely, mineral oil/water, gasoline/water, and n-hexadecane/water emulsions. In addition, these membranes exhibited superior antioil-fouling performance with excellent separation efficiency (97-99%) and a high flux recovery ratio (>98%). The 10 wt % SKL-incorporated membrane (L-10) also showed consistent separation performance after 10 cyclic tests, indicating its excellent reusability and recyclability. Furthermore, the stability of the membrane under harsh pH conditions was also evaluated and proved to be robust enough to maintain its wettability in a wide pH range (pH 1-10).

Ultrasonically synthesized MOFs for modification of polymeric membranes: A critical review.

Metal-organic framework (MOF) membranes hold the promise for energy-efficient separation processes. These nanocrystalline compounds can effectively separate materials with different sizes and shapes at a molecular level. Furthermore, MOFs are excellent candidates for improving membrane permeability and/or selectivity due to their unique properties, such as high specific area and special wettability. Generally, MOFs can be used as fillers in mixed matrix membranes (MMMs) or incorporated onto the membrane surface to modify the top layer. Characteristics of the MOFs, and correspondingly, the properties of the MOF-based membranes, are majorly affected by their production technique. This critical review discusses the sonication technique for MOF production and the opportunities and challenges of using MOF for making membranes. Effective parameters on the characteristics of the synthesized MOFs, such as sonication time and power, were discussed in detail. Although the ultrasonically synthesized MOFs have shown great potential in the fabrication/modification of membranes for gas and liquid separation/purification, so far, no comprehensive and critical review has been published to clarify such accomplishments and technological gaps for the future research direction. This paper aims to review the most recent research conducted on ultrasonically synthesized MOF for the modification of polymeric membranes. Recommendations are provided with the intent of identifying the potential future works to explore the influential sonication parameters.

Synthesize optimization, characterization, and application of ZIF-8 adsorbent for elimination of olive oil from aqueous solution.

In view of the importance of water quality and environmental aspect, zeolitic imidazolate framework-8 (ZIF-8) adsorbent was synthesized via a solvothermal approach for oil removal from water. Response surface methodology-central composite design approach (RSM-CCD) using a statistical software (Design expert, version 8.0.6) was employed to identify the influence of three independent variables of ZIF-8 synthesis procedure including ligand/salt molar ratio, solvent/salt molar ratio, and synthesis temperature on the oil adsorption capacity and yield of adsorbent as RSM responses. The optimum conditions for preparing ZIF-8 were found as follows: ligand/salt molar ratio of 10.4, solvent/salt ratio of 702.7, and temperature of 52.9 °C, which resulted in 1120 mg/g of olive oil uptake and 43% of ZIF-8 yield. Morphological and structural properties of the prepared adsorbent were characterized by N2 adsorption-desorption, XRD, FE-SEM, and FTIR analyses. Batch equilibrium adsorption experiments were conducted under varied system parameters expected to affect the ZIF-8 adsorption capacity including oil concentration, ZIF-8 dosage, contact time, and temperature. The isotherm and kinetic of olive oil adsorption onto ZIF-8 followed the Freundlich and pseudo-first-order models, respectively. The evaluation of thermodynamic parameters demonstrated that olive oil adsorption onto optimized ZIF-8 was spontaneous and exothermic in nature. In addition, the used ZIF-8 can be recovered effectively using a simple ethanol-washing method. Based on experimental results, the ZIF-8 prepared in this study can be successfully used in oil/water emulsion separation.

New strategy to enhance heavy metal ions removal from synthetic wastewater by mercapto-functionalized hydrous manganese oxide via adsorption and membrane separation.

The development of efficient materials and methods for the elimination of heavy metals contamination from water bodies is increasingly demanded as these toxic cations can acute diseases to humans or make serious threat to the environment. The aim of this research is to evaluate the effectiveness of the organosilane coupling agent for the modification of hydrous manganese oxide and the application of the functionalized nanoadsorbent for the removal of nickel and copper ions from synthetic wastewater samples. The synthesized thiol-functionalized hydrous manganese oxide was characterized in terms of their morphology, surface area, functional groups, surface elemental compositions, and the structural properties. In the adsorption process of Ni(II) and Cu(II), the effective parameters including the initial metal cation concentration (20-150 mg/L), operation temperature (298-318 K), and the contact time at the optimum pH were investigated. The uptake of Ni(II) and Cu(II) ions on the prepared adsorbents followed by the Freundlich isotherm model reveals the heterogeneous adsorption, with the adsorption capacities of 24.96 mg/g and 31.2 mg/g for the modified adsorbent and 23.92 mg/g and 29.6 mg/g for the virgin adsorbent, respectively. Based on the results, both the virgin and the functionalized adsorbents exhibited high affinity to copper ions than nickel in the single-component system. Kinetic experiments of both metal ions clarified that the experimental data was well predicted by pseudo-second-order model and the equilibrium was achieved after 10 min of contact time. Additionally, the incorporation of the as-prepared adsorbents in the electrospun nanofibers membrane matrix showed the promising potential for the removal of metal cations. The nickel and copper removal efficiency by the membranes containing 1.5 wt% of the modified adsorbent was 80% and 89%, respectively which implying that the modified adsorbent could be employed more efficiently in other treatment techniques for the removal of metallic pollutants. The modification of hydrous manganese oxide by the functional mercaptosilane increases the adsorption sites for trapping the metal ions and improves the adsorption capacity, making high capability for the removal of metal ions from the effluent.

A critical review on ultrasonic-assisted fouling control and cleaning of fouled membranes.

Fouling is one of the most challenging problems impacting the performance of membrane-based separation technology. In recent years, ultrasound have been widely applied as an unconventional method to control membrane fouling, as well as to enhance membrane cleaning. The aim of the present work is to review the current literature and the recent developments related to the use of ultrasound as an innovative and alternative approach to improve the fouling behavior of membrane separation processes. The theory underlying ultrasonic-assisted phenomena is reviewed, together with operational factors that influence the effectiveness of the ultrasound treatment, such as frequency, power intensity, pressure, temperature, pH, and operation mode. Ultrasound irradiation effectively aids the cleaning of contaminated surfaces and enhances the permeate flux, owing to cavitation phenomena and powerful convective currents, associated with secondary phenomena, such as microstreamers, shock waves, and heating. However, the lifetime of the membranes should be carefully evaluated when applying ultrasonication as a technique of cleaning or controlling membrane fouling. Indeed, the integrity of membranes after sonication and the control of erosion produced by high ultrasonic intensities are key issues hindering the scale-up of this approach in the membrane industry. This reviews highlights the topics requiring more investigations, specifically to evaluate the economic aspects of ultrasonic assisted fouling control and cleaning in membrane processes.

Pushing Rubbery Polymer Membranes To Be Economic for CO2 Separation: Embedment with Ti3C2Tx MXene Nanosheets.

Sustainable and energy-efficient molecular separation requires membranes with high gas permeability and selectivity. This work reports excellent CO2 separation performance of self-standing and thin-film mixed matrix membranes (MMMs) fabricated by embedding 2D Ti3C2Tx MXene nanosheets in Pebax-1657. The CO2/N2 and CO2/H2 separation performances of the free-standing membranes are above Robeson's upper bounds, and the performances of the thin-film composite (TFC) membranes are in the target area for cost-efficient CO2 capture. Characterization and molecular dynamics simulation results suggest that the superior performances of the Pebax-Ti3C2Tx membranes are due to the formation of hydrogen bonds between Ti3C2Tx and Pebax chains, leading to the creation of the well-formed galleries of Ti3C2Tx nanosheets in the hard segments of the Pebax. The interfacial interactions and selective Ti3C2Tx nanochannels enable fast and selective CO2 transport. Enhancement of the transport properties of Pebax-2533 and polyurethane when embedded with Ti3C2Tx further supports these findings. The ease of fabrication and high separation performance of the new TFC membranes point to their great potential for energy-efficient CO2 separation with the low cost of $29/ton separated CO2.

Toward Sustainable Tackling of Biofouling Implications and Improved Performance of TFC FO Membranes Modified by Ag-MOF Nanorods.

In this work, nanorods with high antibacterial properties were synthesized with silver acetate as the metal source and 2-aminoterephthalic acid as the organic linker and were then embedded into thin-film composite (TFC) membranes to amend their performance as well as to alleviate biofouling. Silver metal-organic framework (Ag-MOF) nanorods with a length smaller than 40 nm were incorporated within the polyamide thin selective layer of the membranes during interfacial polymerization. The interaction of the synthesized nanorods with the polyamide was favored because of the presence of amine-containing functional groups on the nanorod's surface. The results of X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy characterizations proved the presence of Ag-MOF nanorods in the selective layer of thin-film nanocomposite (TFN) membranes. TFN membranes demonstrated improved water permeance, salt selectivity, and superior antibacterial properties. Specifically, the increased hydrophilicity and antibacterial potential of the TFN membranes led to a synergetic effect toward biofouling mitigation. The number of live bacteria attached to the surface of the neat TFC membrane decreased by more than 92% when a low amount of Ag-MOF nanorods (0.2 wt %) was applied. Following contact of the TFN membrane surface with Escherichia coli and Staphylococcus aureus, full inactivation, and degradation of bacteria cells were observed with microscopy, colony-forming unit tests, and disc inhibition zone analyses. This result translated to a negligible amount of the biofilm formed on the active layer. Indeed, the incorporation of Ag-MOF nanorods decreased the metal-ion release rate and therefore provided prolonged antibacterial performance.

In Situ Ag-MOF Growth on Pre-Grafted Zwitterions Imparts Outstanding Antifouling Properties to Forward Osmosis Membranes.

In this study, a polyamide forward osmosis membrane was functionalized with zwitterions followed by the in situ growth of metal-organic frameworks with silver as a metal core (Ag-MOFs) to improve its antibacterial and antifouling activity. First, 3-bromopropionic acid was grafted onto the membrane surface after its activation with N,N-diethylethylenediamine. Then, the in situ growth of Ag-MOFs was achieved by a simple membrane immersion sequentially in a silver nitrate solution and in a ligand solution (2-methylimidazole), exploiting the underlying zwitterions as binding sites for the metal. The successful membrane functionalization and the enhanced surface wettability were verified through an array of characterization techniques. When evaluated in forward osmosis tests, the modified membranes exhibited high performance and improved permeability compared to pristine membranes. Static antibacterial experiments, evaluated by confocal microscopy and colony-forming unit plate count, resulted in a 77% increase in the bacterial inhibition rate due to the activity of the Ag-MOFs. Microscopy micrographs of the Escherichia coli bacteria suggested the deterioration of the biological cells. The antifouling properties of the functionalized membranes translated into a significantly lower flux decline in forward osmosis filtrations. These modified surfaces displayed negligible depletion of silver ions over 30 days, confirming the stable immobilization of Ag-MOFs on their surface.

Rhamnolipid as new bio-agent for cleaning of ultrafiltration membrane fouled by whey.

In this work, rhamnolipid biosurfactant as an eco-friendly and biodegradable cleaning agent was produced by Pseudomonas aeruginosa bacteria and was used to evaluate the chemical cleaning efficiency of whey fouled ultrafiltration membranes. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful synthesis of rhamnolipid. The produced rhamnolipid was compared to chemical cleaners including sodium hydroxide (NaOH), sodium dodecyl sulfate (SDS) and Tween 20. Ultrafiltration membranes used for fouling and cleaning analysis were prepared using phase inversion via immersion precipitation technique. For studying the fouling mechanisms, Hermia's model adapted to cross-flow was used. From the fouling mechanism experiments, it was found that the complete blocking and cake formation were the dominant fouling mechanisms. The highest values of cleaning efficiency were achieved using rhamnolipid and NaOH as cleaning agents with the flux recovery of 100%, but with considering the low concentration of the rhamnolipid used in the cleaning solution compared to NaOH (0.3 versus 4 g/L for NaOH), its application is preferred.

Exploiting Synergetic Effects of Graphene Oxide and a Silver-Based Metal-Organic Framework To Enhance Antifouling and Anti-Biofouling Properties of Thin-Film Nanocomposite Membranes.

Thin-film composite (TFC) membranes still suffer from fouling and biofouling. In this work, by incorporating a graphene oxide (GO)-silver-based metal-organic framework (Ag-MOF) into the TFC selective layer, we synthesized a thin-film nanocomposite (TFN) membrane that has notably improved anti-biofouling and antifouling properties. The TFN membrane has a more negative surface charge, higher hydrophilicity, and higher water permeability compared with the TFC membrane. Fluorescence imaging revealed that the GO-Ag-MOF TFN membrane kills Escherichia (E.) coli more than the Ag-MOF TFN, GO TFN, and pristine TFC membranes by 16, 30, and 92%, respectively. Forward osmosis experiments with E. coli and sodium alginate suspensions showed that the GO-Ag-MOF TFN membrane by far has the lowest water flux reduction among the four membranes, proving the exceptional anti-biofouling and antifouling properties of the GO-Ag-MOF TFN membrane.

Cross-linked κ-carrageenan polymer/zinc nanoporous composite matrix for expanded bed application: Fabrication and hydrodynamic characterization.

Expanded bed adsorption (EBA) is a reliable separation technique for the purification of bioproducts from complex feedstocks. The specifically designed adsorbent is necessary to form a stable expanded bed. In the present work, a novel custom-designed composite matrix has been prepared through the method of water-in-oil emulsification. In order to develop an adsorbent with desirable qualities and reduce the costs, κ-carrageenan and zinc powder were used as the polymeric skeleton and the densifier, respectively. The prepared composite matrix was named as KC-Zn. Optical microscope (OM) and scanning electron microscope (SEM) were applied to characterize the morphology and structure of prepared composite matrix. These analyses approved good spherical shape and porous structure with nano-scale pores in the range of about 60-180nm. The results from the particle size analyzer (PSA) revealed that all the KC-Zn beads followed logarithmic normal size distribution with the range of 50-350µm and average diameter of 160-230µm, respectively. Main physical properties of KC-Zn matrices were measured as a function of zinc powder ratio to κ-carrageenan slurry, which showed an appropriate wet density in the range of 1.39-2.27g/ml, water content of 72.67-36.41% and porosity of 98.07-80.24%, respectively. The effects of matrix density and liquid phase viscosity on hydrodynamic behavior of prepared matrix have been investigated by residence time distribution (RTD) experiments in an expanded bed. The results indicated that in a constant liquid velocity as the matrix density was increased, the expansion factor of bed decreased and the axial mixing coefficient increased. Moreover, an enhancement in the fluid viscosity led to an increase in the bed expansion and a decrease in the stability of expanded bed. Therefore using a matrix with higher density seems necessary to face viscous feedstocks. All the results demonstrated that proper physical properties and hydrodynamic characteristics of KC-Zn matrix confirm good potential for possible use in high flow rate expanded bed operations.

Cost-effective nanoporous Agar-Agar polymer/Nickel powder composite particle for effective bio-products adsorption by expanded bed chromatography.

In the present work a novel kind of dense nanoporous composite matrix for expanded bed application has been successfully first prepared with Nickel powder as a densifier and was covered with Agar-Agar layer as a skeleton, through the method of water-in-oil emulsification. Agar-Agar is a porous and inexpensive polymer. In order to fabricate cost-effective adsorbent with favorable qualities Agar-Agar polymer was used. Thereafter, the customized composite particle was modified by pseudo-affinity dye-ligand, Reactive Blue 4 (RB4), aimed at preparing a pseudo-affinity adsorbent (RB4-Agar-Ni) for bioprodut adsorption from aqueous solution. Bovine Serum Albumin (BSA) was selected as a model protein to investigate the adsorption behavior in batchwise and expanded bed chromatography, and the obtained results were evaluated with that of Streamline™ (Amersham-Pharmacia Biotech, Sweden). Spherical appearance and porous structure of composite particles were observed by the optical microscope (OM) and scanning electronic microscope (SEM). The results suggested that the matrices followed the logarithmic normal size distribution with the range of 65-300 µm and average diameter of 126.81-151.47 µm, proper wet density of 1.64-2.78 g/ml, water content of 62.74-34%, porosity of 98-90% and pore size of about 38-130 nm. For better comprehension of the impact of solid phase properties on the performance of the expanded bed, the expansion and hydrodynamic properties of a composite matrix with a series of densities was evaluated and estimated by the retention time distribution method (RTD) in an expanded bed and was compared with that of other matrices. According to obtained results the expansion factors under the same fluid velocity decreased by increasing the matrix density. Moreover, the axial dispersion coefficient (Dax) is the most appropriate parameter for evaluating the stability of expanded bed, on various operating conditions, such as different flow velocity, bed expansion degree, viscosity of the liquid phase and the density of adsorbent. It was observed that the application of matrix with high density was proper for high operation, fluid velocity, since the addition of densifier improves the rigidity of the matrix. Three momentous factors, pH, ionic strength and initial concentration of BSA were analyzed. The best results showed that the adsorption equilibrium isotherms seems to follow a typical Langmuir isotherm and also the maximum adsorption capacity (qm) of BSA on RB4-Agar-Ni (64.01 mg/ml adsorbent) was higher than that on RB4-Streamline commercial adsorbent (about 54 mg.ml adsorbent). Additionally kinetic adsorption processes were characterized by the pseudo-first-order and pseudo-second-order kinetics equations. The experimental data followed the pseudo-first-order kinetic equation. Also the breakthrough curves were investigated. It was found that dynamic binding capacity (DBC) decreased with increasing the flow rate and the values of DBC decreased from 21.08 to 11.15 mg/ml adsorbent when the density of composite beads increased from 1.64 to 2.78 g/ml. All results indicate that the prepared composite is promising for efficient bioproduct adsorption with good hydrodynamic characteristics, high stability and it is suitable for expanded bed usage as a cost-effective adsorbent.

Development of pilot scale nanofiltration system for yeast industry wastewater treatment.

The treatment of the yeast industry wastewater was investigated by nanofiltration (NF) membrane process on a pilot scale. Two wastewaters were used as feed: (i) dilute wastewater with COD 2000 mg/L and (ii) concentrate wastewater with COD 8000 mg/L. The permeate flux, COD retention, color and electrical conductivity (EC) removal were evaluated in relation to trans-membrane pressure and long-term filtration. A linear growth in permeate flux was found with increasing in trans-membrane pressure for wastewaters. In addition, the COD retention, color and EC removal increased with trans-membrane pressure enhancement. The results obtained from the long-term nanofiltration of dilute wastewater indicated that the permeate flux decreased from 2300 L/day to 1250 L/day and COD retention increased from 86% to 92%. The quality of the permeate in term of COD is lower than the discharge standard in river (200 mg/L). Thus, this process is useful for treatment of wastewaters produced by yeast industry.