SEPARATION OF ORGANIC SOLUTES FROM WATER BY LOW-PRESSURE REVERSE-OSMOSIS

The separation of five organic solutes (1-propanol, 1-butanol, 2-butanol, 2-methy-1-propanol, 2-methy-2-propanol) from aqueous solution by reverse osmosis is investigated using a spiral-wound module equipped with a low pressure composite membrane (FT-30). The range of operating pressure is 80-180 psi. Permeate flowrate and rejection are the flow parameters used to characterize system behavior. Permeate flowrates ranging from 2. 272 ml/ft2 to 5.263 ml/ft2 are obtained. The following rejections are achieved: 1 -propanol, 43.77-44.90%; 1-butanol, 72.65-74.62%; 2-butanol, 75.38-81.54%, 2-methyl-1-propanol, 83.80-89.76%; 2 methyl-2-propanol, > 90.0%. Rejection of solutes increased as the number of carbon atoms or molecular weight increased. Organic solute configuration exhibits a significant role in the ability to permeate. Single and double branching alcohols of the same molecular weight are rejected to a greater extent than linear molecules. Rejection behavior could be adequately predicted by the modified concentration polarization model. The modified model provides an insight into the rejection controlling mechanisms in reverse osmosis, which in turn might provide the key to improve process design and operation.