Recent Progress on Tailoring and Modification of Membranes for Membrane Distillation: A Review

Membrane distillation (MD) has gained the interest of many researchers since it is a promising method for the separation and purification process. Membrane distillation (MD) is a non-isothermal separation process in which differential vapor pressure between porous hydrophobic membrane surfaces acts as a driving factor. A hydrophobic membrane is used in the application of MD, which permits only the passage of vapor produced on the feed side through its pores to the permeate side. One of the most significant obstacles to the commercialisation of the MD method is a lack of appropriate membranes for the process. On the other hand, conventional hydrophobic membranes are subjected to rapid wetting and severe fouling, mainly when low surface tension compounds are present in saline water, resulting in decreased MD performance. In recent decades, MD membranes have received exceptional scientific interest, with substantial progress being made in the design and production of MD membranes appropriate for use in many applications. This review gives a comprehensive overview of recent research developments in the tailoring morphological structure of hydrophobic membranes, emphasising advancements in the fabrication and modification of membranes towards exhibiting high efficiency in the MD process. In addition, the critical morphology characteristics, mainly surface roughness, wettability, and water contact angle, are analysed. Finally, the challenges faced and future research direction is highlighted.

Mathematical Modeling of Extraction of Neodymium using Pseudo-emulsion based Hollow Fiber Strip Dispersion (PEHFSD)

Pseudo-emulsion based hollow fiber strip dispersion (PEHFSD) is a promising alternative technique due to its stability, simplicity and cost of operation. This is an efficient process due to its high surface area for extraction as well as stripping, and low energy consumption for creating the pseudo-emulsion and for the separation of phases. This technique takes the combine advantages of emulsion liquid membrane and overcomes the sufferings of membrane stability in the supported liquid membrane systems. Present work includes extraction of neodymium (III) (Nd) by using TODGA and HNO3 as the extractant cum strippant in PEHFSD technique. A model is developed to study the transport of Nd under different hydrodynamic and chemical conditions that includes organic ratio (A/O) in dispersion, effect of speed of impeller on drop size formation, effect of feed acidity, effect of carrier concentration, effect of feed flow rate. A code is written to solve the model equations numerically to predict the concentration of the feed reservoir with time. Experiments are conducted to obtain the best optimum extraction conditions. Results obtained from the numerical simulations are validated with the experimental data and found a good agreement between them.

Surface Modification of Stainless-Steel Membrane using a Closed-Batch iCVD Reactor for Oil/Water Separation

Oil-spill is one of the major global issues facing society in this century. The aim of this study was to develop a steel-based membrane for selective separation of oil from oil/water mixture. For this purpose, a single-step, rapid and environmentally friendly closed-batch initiated chemical vapor deposition (iCVD) method was employed to deposit hydrophobic thin film on a stainless-steel mesh. Perfluorodecyl acrylate (PFDA) and tert-butyl peroxide (TBPO) were used as monomer and initiator, respectively. Owing to the inherent vapor-based nature of iCVD method provided excellent conformal coverage on the mesh with high durability. iCVD coated mesh showed 96% oil/water separation efficiency. Highly reproducible results were obtained when the oil/water separation experiments were repeated.

Clay Ceramic Support Membrane Optimization Using Factorial Design Approach

In the present study, the effect of Sintering temperature, Particle size and Heating rate of the ceramic support membrane Elaboration based on dry clay were evaluated using full factorial design and investigated by porosity and mechanical strength measures. The flat supports have been prepared from 5 g of the material with a two fraction 2 and 30 µm, the extrusion was performed using the uniaxial pressing in applicant a pressure of 12 tones, the supports sintered between 900° C and 1200°C with a different heating rate (1°C/min and 10°C/min). By using full factorial design 23, it was found that the sintering temperature is the main controlling factors of the physical properties of dry ceramic support membrane, and its increase had a positive effect on Mechanical strength and negative effect on porosity. The interactions between the factors were relatively less important, and they had different (antagonistic/synergetic) influence on the properties. The optimal factors to elaborate the support membrane include a particle size of 2 µm, sintering temperature of 950°C, Heating rate of 1°C predicting the porosity of 40, 8% and Mechanical strength of 12 MPa.

Insights into Membrane Distillation Application for Textile Wastewater Treatment – A Review

Textile wastewater must be effectively treated with the best available technology prior to release to receiving water bodies to prevent its impact on the environment. Apparently, membrane distillation shows great potential in treating textile wastewater a part of the complexity of the textile wastewater composition. This membrane process enables the water vapour to pass through its porous hydrophobic membrane and retains the concentrated pollutants to be transported. This paper provides data and information from previous studies using membrane distillation to treat textile wastewater. An overview of the development of membrane distillation as well as the fundamental theory is presented. Recent progress in the application of membrane distillation in textile wastewater is then discussed. The final part of the paper looked at the future orientation of this technology to be acceptable in the industrial sector, especially for the textile industry.

Grand Challenges of Perovskite and Metal Oxide-based Membrane: A Form of Dual-layer Hollow Fibre

Perovskite and metal oxides-based dual-layer hollow fibre membrane (DHF) has a high appeal as separator and catalyst for methane conversion application which operated at intermediate and high temperature. The membrane mostly fabricated via the co-extrusion followed by co-sintering method, which is quite challenging, due to the complexity to handle the barrier between layers from delamination, membrane cracking and crystal structure distortion which affects the material performance in a DHF form. This recent review clarifies the challenges in the DHF fabrication process to regulate physical and chemical properties in terms of mechanical strength, tightness, elemental distribution, and crystal structure stability. The based material of the membrane focuses on NiO-YSZ in the inner layer directly interconnected with LSCF-YSZ in the outer layer. The understanding of the challenges in DHF fabrication, will further reduce crucial errors in the fabrication process and accelerate performance improvement for application such as syngas, methanol and long-chain hydrocarbons production, and solid oxide fuel cell.

The Future Challenges of Anaerobic Membrane Bioreactor (AnMBR) for High Strength Wastewater

This article is to present a review of anaerobic membrane bioreactor (AnMBR), process, operational condition, fouling mechanism and future challenge for high strength wastewater. Since1969s, membrane filtration technology has been used and continuously developed for wastewater treatment and recovery. AnMBR has proposed for the economic feasibility owing to the low footprint, high yield production under the relatively low energy consumption. Continuous stirred tank reactor (CSTR) configuration is the widely used couple with a flat sheet or hollow fibre modules. The various factors of operating condition are influence on the performance such as hydraulic retention time (HRT= 6 – 12 d), solid retention time (SRT > 100 d) and operating temperature (T = 10 - 56oC). In addition, the increase in temperature is related to high methanogenic activity and high COD removal efficiency (85% - 99%). However, the limitation of this process is fouling that occurs from the soluble microbial product (SMP), exopolymer substance (EPS) and biopolymer cluster (BPC). Almost of appropriate operating conditions for high performance, anti-fouling, the majority of effective microorganisms and energy balance are discussed in detail. For the challenge work, improvement of the prevention membrane fouling and high energy recovery in the hybrid/combination system with forward osmosis (FO), membrane distillation (MD) and powder activated carbon (PAC)-AnMBR.

Challenges in Membrane Process for Gas Separation from Natural Gas

Membrane technology is cost effective solution for CO2 removal from natural gas. However, there is challenges during its application depending on the polymer material characteristic. Understanding on the polymer fundamental and transport properties, will enable proper design of pre-treatment and operating conditions that suits its capability envelope. Diffusivity selective membrane favors high pressure and high temperature conditions and vice versa for solubility selective polymer. On top of that, the robustness and durability of the resultant membrane, need to be evaluated with multicomponent mixture to understand the effect of competitive sorption, plasticization and aging phenomena that will seriously impacting the membrane performance during its application.

Membrane Fouling – The Enemy of Forward Osmosis

Forward osmosis (FO) is an osmotically driven membrane separation process. It is potentially applied in various industries for nutrient recovery and water reclamation. Although FO showed a lesser fouling tendency than other pressure-driven membrane processes, the solutes in the feed solution would still deposit on the membrane surface, forming a fouling layer that resists water permeation. For that reason, fouling mitigation is a trending issue in the FO process. A better understanding of the fouling mechanism is required before opting for the appropriate strategy to mitigate it. This article describes the fouling mechanism based on different foulant presented in the feed, followed by a method in relieving fouling in the FO process.

Effects of Pore Additives on Deep Eutectic Solvent Immobilization for CO₂/N₂ Gas Separation Using Supported Deep Eutectic Solvent Membranes

This work analyses the effect of two different pore additives focusing on polyethylene glycol (PEG) and lithium chloride (LiCl) at different concentrations on the immobilization of a deep eutectic solvent (DES) in a polyvinylidene fluoride-co-polytetrafluoroethylene (PVDF-co-PTFE) membrane. Two compounds were chosen to synthesized the DES; choline chloride as halide salt and ethylene glycol as a hydrogen bond donor. The DES was impregnated onto the membrane pores by applying a vacuum-based technique. The membranes were prepared via phase inversion by means of immersion precipitation. For characterization purposes, scanning electron microscopy (SEM-EDX) was used to analyse the morphology of the supported- DES-membranes together with energy dispersive X-ray spectrometry. The gravimetric method was applied to calculate the porosity, while the membrane performance for carbon dioxide (CO2) permeation and separation was assessed to determine the capability of the DES-impregnated membrane. The outcomes demonstrating that the highest loading of DES in the membrane support was obtained when 3 wt% PEG was added into the polymer solution with a porosity of 70.5%. The CO2 permeability and the CO2/N2 selectivity achieved using the synthesized membrane are 2.81 x 106 barrer and 3.46, respectively, when working with a transmembrane pressure of 1.1 bar and a temperature of 25ᵒC at 200 cm3 /min of gas flow rate. The results showed that additional of PEG as a pore additives able to load the highest DES in the membrane pore and resulted the best CO2 permeability and the CO2/N2 selectivity.