Highly Saline Water Desalination Using Direct Contact Membrane Distillation (DCMD): Experimental and Simulation Study

The path for water molecules transported across a membrane in real porous membranes has been considered to be a constant factor in the membrane distillation (MD) process (i.e., constant tortuosity); as such, its effect on membrane performance at various operating conditions has been ignored by researchers. Therefore, a simultaneous heat and mass transfer model throughout the direct contact membrane distillation (DCMD) module was developed in this study by taking into account the hypothetical path across the membrane as a variable factor within the operating conditions because it exhibits the changes to the mass transfer resistance across the membrane under the DCMD run. The DCMD process was described by the developed model using a system of nonlinear equations and solved numerically by MATLAB software. The performance of the poly-tetra-fluoroethylene (PTFE) membrane was examined to treat 200 g/L NaCl saline at various operating conditions. The simulation results in the present work showed that the hypothetical proposed path across the membrane has a variable value and was affected by changing the feed temperature and feed concentration. The results estimated by the developed model showed an excellent conformity with the experimental results. The salt rejection remained high (greater than 99.9%) in all cases. The temperature polarization coefficient for the DCMD ranged between 0.88 and 0.967, and the gain output ratio (GOR) was 0.893. The maximum thermal efficiency of the system was 84.5%

Membrane Bioreactor and Promising Application for Textile Industry in Vietnam

Abstract A pilot-scale membrane bioreactor (MBR) was developed in order to run two membrane modules in parallel for the treatment of model textile wastewater (MTDW). Two independently operated commercially available ultrafiltration membrane modules called UP150 from Microdyn-Nadir where tested in the same activated sludge tank over a period of 70 days for their removal efficiency of the MTDW. In general the results of both membrane modules are in very good agreement. The water permeability ranged between 20 – 50 L/(m 2 .h.bar). Typically, the chemical oxygen demand (COD) removal efficiency indicated good biodegradation performance above 95%. The nitrification rate depended on the food to microorganism (F/M) ratio i.e. below 0.2 kg COD/(kg MLSS.d) the system showed complete nitrification. However, the color rejection for the model dyes was only around 20% to 60% what can be attributed to the low biodegradability of these chemicals. The next step is to run the MBR with novel nanostructured membranes in parallel with the commercially available membrane to compare their performances. This study contributes to sustainable development in the textile industry by improving water quality of treated textile wastewater what helps to reduce fresh water consumption and pollutant discharge

An alternative encapsulation approach for production of active chitosan-propolis beads

Encapsulation is a promising technology to carry natural active substances, preventing their loss and maintaining their stability until use. Beads of chitosan-containing propolis have been prepared using a mono-pore filter device, which permits the encapsulation of natural polyphenols avoiding heat treatments, high shear rates and the use of toxic solvents. Beads proved to be active against Bacillis cereus, Escherichia coli, Listeria innocua, Pseudomonas fluorescens, Yarrovia lipolytica and three moulds strains; the highest effect was found against Staphylococcus aureus (MIC 0.8 mg beads mL-1). Results in liquid cultures of S. aureus evidenced that beads were able to release the flavonoids from propolis: the diffusion of the active compounds is a key factor in the exploitation of the microbial activity. The obtained chitosan-propolis beads represent an example of natural antimicrobial delivery system that could be used to prevent the growth of pathogenic/spoilage bacteria in food applications

Toward the Next Generation of Sustainable Membranes from Green Chemistry Principles

Large-scale membrane technology has been widely implemented and rapidly growing for roughly 40 years. However, considering its entire life cycle, there are aspects being characterized by low sustainability, and this industry certainly cannot be defined as green. In the membrane manufacturing process, raw materials mainly rely on nonbiodegradable petroleum-based polymers and hazardous solvents. These materials are thus associated with the energy crisis and with disposal burdens at the end of their lifetime, and they pose risks to workers and the environment. Therefore, biobased polymers and green solvents should be employed within the membrane preparation process and replace traditional ones. Moreover, the wastewater generated from membrane fabrication processes contains an important amount of organic solvents and should be efficiently treated or recycled before discharge. The application of artificial intelligence in membrane manufacturing and use processes can also improve efficiency significantly. Finally, a large number of spent membrane elements should also be reused and recovered, rather than landfilled. This review critically evaluates the recent advances in methods to improve the sustainability of membrane technology, specifically emphasizing the progresses made, with regard to the above aspects. This review thus analyzes the needs for membrane industry transformations in the light of circular economy

Experimental evaluation of the thermal polarization in direct contact membrane distillation using electrospun nanofiber membranes doped with molecular probes

Membrane distillation (MD) has recently gained considerable attention as a valid process for the production of fresh-water due to its ability to exploit low grade waste heat for operation and to ensure a nearly feed concentration-independent production of high-purity distillate. Limitations have been related to polarization phenomena negatively affecting the thermal efficiency of the process and, as a consequence, its productivity. Several theoretical models have been developed to predict the impact of the operating conditions of the process on the thermal polarization, but there is a lack of experimental validation. In this study, electrospun nanofiber membranes (ENMs) made of Poly(vinylidene fluoride) (PVDF) and doped with (1, 10-phenanthroline) ruthenium (II) Ru(phen) 3 were tested at different operating conditions (i.e., temperature and velocity of the feed) in direct contact membrane distillation (DCMD). The temperature sensitive luminophore, Ru(phen) 3 , allowed the on-line and non-invasive mapping of the temperature at the membrane surface during the process and the experimental evaluation of the effect of the temperature and velocity of the feed on the thermal polarization

A non-invasive optical method for mapping temperature polarization in direct contact membrane distillation

Membrane Distillation (MD) is a thermal membrane process allowing for a theoretical 100% rejection of non-volatile compounds (i.e. ions, macromolecules, colloids, cells), whereas vapour molecules permeate through a micro-porous hydrophobic membrane due to a difference of vapour pressure established across the membrane-self. The effective driving force and, then, the vapour trans-membrane flux is affected by temperature polarization phenomena occurring in the boundary layers adjacent to the membrane. The temperature values at the membrane surface are usually difficult to measure and only recently some invasive techniques were adopted for this scope. The aim of this work was to introduce luminescent molecular probing as an innovative technology for non-invasive and in-situ monitoring of thermal polarization in MD. Tris(phenantroline)ruthenium(II) chloride (Ru(phen)3) was selected as temperature sensitive luminescent probe and immobilized in a flat poly(vinylidene fluoride) electrospun nanofibrous membrane (PVDF ENM). Experiments showed the key role of the Ru(phen)3 and Lithium Chloride (LiCl) in the preparation of homogeneous PVDF ENM due to their ionic nature that improved the electrical conductivity of the polymeric solution favouring the electrospinning. Furthermore, PVDF ENM showed a good performance in Direct Contact Membrane Distillation (DCMD) process. The immobilization of the molecular probe allowed to optically monitoring the membrane surface temperature during DCMD experiments. On the other hand, the employment of an IR-camera permitted the evaluation of the temperature of the bulk of liquid streams. Therefore, the combination of these two optical techniques enabled to evaluate, in a direct and non-invasive way, the thermal polarization along the membrane module during DCMD experiments

A Mini-Review of Enhancing Ultrafiltration Membranes (Uf) for Wastewater Treatment: Performance and Stability

The scarcity of freshwater resources in many regions of the world has contributed to the emergence of various technologies for treating and recovering wastewater for reuse in industry, agriculture, and households. Deep wastewater treatment from oils and petroleum products is one of the difficult tasks that must be solved. Among the known technologies, UF membranes have found wide industrial application with high efficiency in removing various pollutants from wastewater. It is shown that the search for and development of highly efficient, durable, and resistant to oil pollution UF membranes for the treatment of oily wastewater is an urgent research task. The key parameters to improve the performance of UF membranes are by enhancing wettability (hydrophilicity) and the antifouling behavior of membranes. In this review, we highlight the using of ultrafiltration (UF) membranes primarily to treat oily wastewater. Various methods of polymer alterations of the UF membrane were studied to improve hydrophilicity, the ability of antifouling the membrane, and oil rejection, including polymer blending, membrane surface modification, and the mixed membrane matrix. The influence of the type and composition of the hydrophilic additives of nanoparticles (e.g., Multiwall carbon nanotubes (MWCNT), graphene oxide (GO), zinc oxide (ZnO), and titanium dioxide (TiO2 ), etc.) was investigated. The review further provides an insight into the removal efficiency percent. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Application of Novel Low-Fouling Membranes for Fish Processing Wastewater Treatment and Comparison to PES Commercial Membranes in a Lab Scale Membrane Bioreactor

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Fabrication of gum arabic-graphene (GGA) modified polyphenylsulfone (PPSU) mixed matrix membranes: A systematic evaluation study for ultrafiltration (UF) applications

In the current work, a Gum, Arabic-modified Graphene (GGA), has been synthesized via a facile green method and employed for the first time as an additive for enhancement of the PPSU ultrafiltration membrane properties. A series of PPSU membranes containing very low (0–0.25) wt.% GGA were prepared, and their chemical structure and morphology were comprehensively investigated through atomic force microscopy (AFM), Fourier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). Besides, thermogravimetric analysis (TGA) was harnessed to measure thermal characteristics, while surface hydrophilicity was determined by the contact angle. The PPSU-GGA membrane performance was assessed through volumetric flux, solute flux, and retention of sodium alginate solution as an organic polysaccharide model. Results demonstrated that GGA structure had been successfully synthesized as confirmed XRD patterns. Besides, all membranes prepared using low GGA content could impart enhanced hydrophilic nature and permeation characteristics compared to pristine PPSU membranes. Moreover, greater thermal stability, surface roughness, and a noticeable decline in the mean pore size of the membrane were obtained