Pressure Retarded Osmosis Characteristics of Commercial RO Membranes

Abstract

As the necessity of stable energy using sustainable resources increases, people are higly interested in renewable energy using osmotic pressure of seawater. Osmotic power is to produce electric power by using the chemical potential of two flows with the difference of salinity, and Pressure Retarded Osmosis is a process that produces electric energy by working the turbine by the pressure which is generated from fresh water passing through the semipermeable membrane and moving to seawater. This study was conducted a research on the possibility of application to the PRO process by using the RO membranes that is commonly used. The variety of NaCl concentration solution used as draw solution and the experiment was conducted by adjusting concentration, velocity and pressure conditions. Distilled water was used as feed solution, and velocity and pressure were maintained to be fixed. As a result of the experiment, the flux and the value of power density of RO membrane changed followed by concentration of draw solution, velocity and pressure, and the maximum power density was 0.136 W/m2. In particular, ECP could be decreased by increasing velocity, and the salt rejection rate of the RO membrane for seawater was higher than that of RO membrane for brackish water and accordingly the possibility of application to the PRO process of the RO membrane for seawater was higher. As a result, it can be defined known that there is a limit in applying the RO membrane to the PRO process, and it also can be defined observed that each ICP and ECP by structure function very importantly. It can be judged that the design of the membrane structure considering concentration polarization and strength will be an important factor in developing the separator for PRO from now on.