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Removal of organic contaminants by RO and NF membranes (4/9/09) In order for water to be drinkable, organic compounds must be removed from it. The main way this is done is through filtration using a membrane. This study analyzed different membranes, six reverse osmosis membranes and two nanofiltration membranes, and their level of decontamination. It has been found that small, hydrophilic, uncharged molecules pass through the membranes at high rates. The rejection of molecules by the membrane depends on many factors such as the physico-chemical properties of the solvent, solute, and membrane, the solution pH and ionic strength, the solute size or shape and polarity, and the membrane pore size and charge. They tested each membrane with NaCl, (NH4)2CO3 and urea. The membranes were tested for their rejection of their molecules and the rate at which the solution moved across the membrane. It is very difficult to have both high rejection and a high rate. Then three membranes were used for continued testing. For the next test the pH was altered. It was found that as the pH was raised to 7.5 NaCl was increasing rejected while (NH4)2CO3 had a decrease in rejection, the rejection continued to decrease for this compound as the pH was increased. This could be due to VSEPR. It was found that while compounds with larger molecular weights usually have a higher rejection rate, it is not always so. The rejection is more dependent on the solute radius and the radius of the pores of the membrane. The molecular structure of the compound also affects the rejection. Rejection increases when the ratio of the solute radius to the pore radius increases. It was found that RO membranes have higher rejection rates mostly due to smaller pore radii. The rejection of NaCl was much higher than that of organic compounds which leads that the rejection of ionic compounds depends on electrostatic repulsion and is therefore higher. For organic compounds the transport of solutes is controlled by diffusion and convection. Diffusion has its effect when the ratio discussed above is high. Convection has its effect when the ration is lower. Yoon, Y., & Lueptow, R. M. (2005). Removal of organic contaminants by RO and NF membranes. //Journal of Membrane Science//, //261//(1-2), 76-86. doi: doi: DOI: 10.1016/j.memsci.2005.03.038.

This article examined a procedure to bind silver nanoparticles to ceramic membranes for better water filtration. Ceramic membranes filter well but cannot kill bacteria only remove it. Silver is known to have healing qualities. In this article Chinese scientists use an aminosilane agent to bind silver to the ceramic membranes in order to also kill the bacteria. FTIR and UV-Vis spectroscopic analysis were run to test the binding. The membranes were then soaked in Ecoli bacteria. After this it was found that the silver nanoparticles killed the Ecoli bacteria and was not easily removed. This was found to be a successful test. Silver coated ceramic membranes were found to kill Ecoli bacteria while still allowing the membrane to be durable, easily washable, and low cost. Lv, Y., Liu, H., Wang, Z., Liu, S., Hao, L., Sang, Y., et al. (2009). Silver nanoparticle-decorated porous ceramic composite for water treatment. //Journal of Membrane Science//, //331//(1-2), 50-56. doi: doi: DOI: 10.1016/j.memsci.2009.01.007.
 * Silver nanoparticle-decorated porous ceramic composite for water treatment (3/20/09) **

Surface modification of nanostructured ceramic membranes for direct contact membrane distillation (3/9/09) In water treatment for reuse, other than the process of reverse osmosis, membrane distillation is used. Traditionally polymeric membranes are used. In this study different chemically bound surface groups underwent many tests to see which would maximize the use of a ceramic membrane. Ceramic membrane may be better than polymeric membranes because of their high chemical and oxidation tolerance, the heat resistance, and their strength. This study used three different nonpolar polymers perfluorodecyltriethoxysilane (PFS) trichloromethylsilane (TCS), and trimethylchlorosilane (TMS) to optimize the surface of the ceramic membrane. Ceramic membranes are polar and nonpolar polymer surface layers are used to increasing their filtration by repelling the water. Each layer was tested for their polarity effect, their permeability, and their chlorine tolerance. Polymeric membranes are subject to biofouling over time and have a low resistance to chlorine which makes them difficult to clean. These layers were tested for their tolerance for chlorine and therefore, their ease of cleanliness. The PFS yields the best results along with TCS as possible candidate for the surface layer of ceramic membranes in membrane distillation. Future work will hopefully lead to ceramic membranes that can be used for membrane distillation. The next step is to improve the heat capacity of the membranes. Hendren, Z. D., J. Brant, et al. (2009). "Surface modification of nanostructured ceramic membranes for direct contact membrane distillation." __Journal of Membrane Science__ **331**(1-2): 1-10.