![]() ![]() ![]() Basic principles of FO phenomenon is also expressed in this part. The book chapter consists of three main titles firstly including introduction section, the second of which states a literature survey on early definitions of diaphragm, membrane and selectivity phenomenon by considering about last two centuries. In this first part of chapter, advantages of FO over conventional membrane processes and main drawbacks originated from the nature of FO membranes are thoroughly stated by considering both review and research articles in the available literature. Therefore, the number of studies related to improving both active and support layers of FO membranes is increasing in the applications. However, nature of FO membranes (asymmetrical structure) causes ICP which promotes the decrease in water flux. As the driving force is only the osmotic pressure difference between two solutions which means that there is no need to apply an external energy, this results in low fouling propensity of membrane and minimization of irreversible cake forming which are the main problems controverted by membrane applications -especially- in biological treatment systems (e.g. The osmotic pressure difference is the driving force of water transport, as opposed to pressure-driven membrane processes A concentrated DS with osmotic pressure draws water molecules from the FS through a semi-permeable membrane to the DS. The diluted DS is then reconcentrated to recycle the draw solutes as well as to produce purified water. Moreover, “necessity of concentrate management” and “meeting of discharge standards with high amounts of product water” oblige the developing new processes, membrane materials or modifications and finding new DS. In recent studies, developing new FO membranes by optimization of thickness, porosity, tortuosity of active/support layer of FO membrane to increase water flux and decrease ICP are mainly focused.įO is a technical term describing the natural phenomenon of osmosis: the transport of water molecules across a semi-permeable membrane. However, all drawbacks of FO process such as (i) membrane fouling originated from ICP, (ii) lower flux, and (iii) reverse salt diffusion (RSD) limit the performance of the FO applications in environmental studies. Among the concentration-driven processes, FO has recently attained many attractions due to its advantages such as less energy requirement, lower fouling tendency or easier fouling removal and higher water recovery. Membrane separation processes have been widely applied for many years in environmental, industrial applications, and domestic use such as water/wastewater treatment, desalination, specific industrial purposes and energy recovery. The manufacturing methods of support and active layers forming FO membranes are described with common and/or new modification procedures. In the first part, which appears here, the overview of membrane technologies and the definition of forward osmosis process are stated. The purpose of the chapter is to bring an overview on the FO membrane manufacturing, characterizing and application area at laboratory or full scales. As a major disadvantage, nature of FO membranes (asymmetrical structure) causes international concentration polarization (ICP) which promotes the decrease in water flux. The diluted DS is then reconcentrated to recycle the draw solutes as well as to produce purified water. A concentrated draw solution (DS) with osmotic pressure draws water molecules from the feed solution (FS) through a semi-permeable membrane to the DS. The osmotic pressure difference is the driving force of water transport, as opposed to pressure-driven membrane processes. Forward osmosis (FO) is a technical term describing the natural phenomenon of osmosis: the transport of water molecules across a semi-permeable membrane. ![]()
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