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Membrane Technologies for Water Purification
Published in P.K. Tewari, Advanced Water Technologies, 2020
Microfiltration is a membrane separation technique in which very fine particles such as suspended solids and colloidal particles are removed from water. The pore size of the microfiltration membrane is typically in the range of 0.1–0.2 μm. Microfiltration (MF) is mainly used for the removal and separation of suspended solids. MF membranes are made from natural or synthetic polymeric materials. Commonly used polymeric materials for MF membranes are cellulose nitrate or acetate, poly-vinylidene difluoride (PVDF), polyamides, polysulfone, polycarbonate, polypropylene, polytetrafluoroethylene (PTFE), etc. Inorganic materials such as metal oxides (alumina), glass, zirconia-coated carbon, etc. are also used for manufacturing MF membranes. Properties such as mechanical strength, temperature resistance, chemical compatibility, hydrophobicity, hydrophilicity, permeability and perm-selectivity play an important role in the choice of membrane materials with respect to particular applications.
Theoretical Approach behind Membrane Processing Techniques
Published in M. Selvamuthukumaran, Applications of Membrane Technology for Food Processing Industries, 2020
The process is called a crossflow or tangential flow filtration because the filtration flow is perpendicular to the feed flow in the tube with the layer of membrane on the surface of the inside wall of the tube (Figure 3.3). In this, the feed flow is at high pressure inside the tube, which further aids in the filtration process. The high flow rate creates the generation of tumultuous stream, thereby preventing the blockage of the membrane, which prevents the rapid drop-off in flux rate and allows a higher volume to be filtered (Figure 3.2b) (Hasan et al. 2013; Herterich et al. 2017). Microfiltration membranes are generally made up of various polymers such as cellulose derivatives (Hu et al. 2019), polypropylene (Pi et al. 2016), polyvinylidene fluoride (Chen et al. 2017), polysulfones (Ohya et al. 2009), polyester (Chollom et al. 2017), and nylon (Huang et al. 2013). The selection of an appropriate membrane for microfiltration contributes to the efficiency of the process, which mainly depends on the type of the fluid, pH of the fluid system, the temperature of the dispersion, nature of the dissolved solids, molecular weight of the solutes, and loading of the suspended solutes. The selection of the suitable membrane also depends on the cost, percentage recovery, and pretreatment requirements involved for the filtration process.
Microfiltration, Ultrafiltration, and Other Membrane Separation Processes: A Critical Overview and a Vision for the Future
Published in Lionello Pogliani, Suresh C. Ameta, A. K. Haghi, Chemistry and Industrial Techniques for Chemical Engineers, 2020
Microfiltration is a type of separation process where a contaminated fluid is passed through a pore sized membrane to separate microorganisms and suspended particles from the liquid stream and wastewater. It is prominently used in conjunction with reverse osmosis and UF. The array of applications are water treatment, sterilization, petroleum refining, and dairy processing. The subtleties of science, engineering, and technological validation and the futuristic vision of membrane science will all lead a long and visionary way in the true realization of environmental remediation. For these reasons, MF stands as a pre-eminent technique. In the food and beverage industry, MF has vital applications. Process design and process engineering of membrane separation processes are today in the vistas of new scientific regeneration. This chapter will be a veritable eye opener to the vast scientific intricacies of fouling phenomenon of membrane science.
Membrane separation of antibiotics predicted with the back propagation neural network
Published in Journal of Environmental Science and Health, Part A, 2023
Mixuan Ye, Haidong Zhou, Xinxuan Xu, Lidan Pang, Yunjia Xu, Jingyuan Zhang, Danyan Li
Three types of membranes, i.e., microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes were used. MF and UF membranes made from polyether sulfone were with pore size 0.1 µm and MWCO 5000 Da, respectively. NF membrane was made from polyamide with MWCO 300 Da. The effective filtration area of the 3 membranes was 2.2 m2, and pH tolerance was in the range of 1.5-11.0. These membranes were hydrophilic and negatively charged in the water solution during tests. The reference standards SMZ (CAS No.: 723-46-6), TC (CAS No.: 60-54-8), AZM (CAS No.: 83905-01-5), CIP (CAS No.: 85721-33-1) and internal standard SMZ-D4 were bought from Dr. Ehrenstorfer (Augsburg, Germany) with above 95% purity. The detailed information above the compounds is shown in Appendix Table A1. Antibiotic stock solution (1 g/L) and internal standard stock solution (10 mg/L) were prepared and stored at −20 °C and protected from light before the start of the tests. Acetonitrile, dichloromethane, formic acid, methanol, and acetone were of HPLC grade. Potassium sodium tartrate, potassium persulfate, ascorbic acid, ammonium molybdate, hydrochloric acid, sodium hydroxide, and sulfuric acid were analytical grade or better. Poly-Sery HLB cartridges (6 cm3/200 mg) used for solid-phase extraction (SPE) were purchased from ANPEL (Shanghai, China). Ultrapure water was prepared with an EPED ultrapure water-purifying system (Tianjin Automatic Science Instrument Co. Ltd., China).
Arsenic exposure from groundwater: environmental contamination, human health effects, and sustainable solutions
Published in Journal of Toxicology and Environmental Health, Part B, 2021
Elida Cristina Monteiro De Oliveira, Evelyn Siqueira Caixeta, Vanessa Santana Vieira Santos, Boscolli Barbosa Pereira
Microfiltration and ultrafiltration are low-pressure-driven separation techniques typically applied for the removal of organic matter, suspended particles, macromolecules, and colloids of water and groundwater. Conversely, previous investigators reported that both procedures are not suitable for an efficient soluble As removal, since membranes are based upon pore flow model and enable multivalent ions to pass through the membrane pores, thereby showing limited capacity for metalloid treatment (Sarkar and Paul 2016). Thus, the efficiency of As removal from water might increase through a hybrid system of adsorption and microfiltration/ultrafiltration (Wan et al. 2020).
Investigating reverse osmosis membrane fouling and scaling by membrane autopsy of a bench scale device
Published in Environmental Technology, 2022
Pablo García-Triñanes, Makrina A. Chairopoulou, Luiza C. Campos
In order to break, loosen or dissolve the accumulated layers and free the membrane’s surface, physical and chemical pre-treatment is used [5]. A widely employed method is the use of heated aluminium oxide particles (HAOPs) to remove both NOM and colloids from water and thereby mitigate fouling of membranes [16]. Usually, a step employing ultrafiltration or microfiltration is found efficient to safeguard the membrane. Microfiltration is preferred since it achieves almost the same permeability with less pressure [17]. In some experiments, mechanical vibration was found sufficient to prevent fouling as it changes the hydrodynamics of the system and reduces the concentration polarisation [18,19]. This in turn lowers the permeate flux and prevents cake-enhanced concentration polarisation [18]. Sim et al. [20] suggested online monitoring to decrease fouling by flow diversion and antiscalant dosage regulation by means of installing sensors on the membrane module. In yet another study, the coupling of a granular activated carbon filtration was investigated as a pre-treatment step in a community scale desalination plant with promising results in reducing energy consumption and prevention of biofouling on the membrane [21]. Further strategies include mitigation of fouling by controlling the operating parameters to avoid crystal nucleation [22] or intermittent aeration by using air bubbles as a scrubbing media to minimise fouling on the membrane surface [23]. Despite this first line of defence, foulants and scalants continue finding their way to the RO membrane. In such cases, destructing the membrane cartridges and performing a membrane autopsy is advised to diagnose the type of fouling, identify the foulants and their mechanism and improve the membrane performance and durability by mitigating the obtruding body [24–26].