Behaviour of RO90 membrane on the removal of 4-nitrophenol and 4-nitroaniline by low pressure reverse osmosis

Abstract Industrial and groundwater wastewater contains organic compounds that cause a serious environmental problem, specifically, 4-nitrophenol (4NP) and 4-nitroaniline (4NA) have been listed as major priority contaminants by the US environmental protection agency (EPA). This paper makes a comparative study on the removal of two organic compounds, 4NP and 4NA, from aqueous solutions by low pressure reverse osmosis using a RO90 polyamide membrane, analyzing the effect of different experimental conditions such as feed organic compound concentration, applied pressure and pH. The loss of efficiency of RO90 membrane after a long period of use and the effect of ultrasound cleaning treatment on that efficiency have also been studied. Different rejection behavior is observed for the two compounds at pH higher than 6, 4NA shows a rejection decrease and 4NP shows an important rejection increase as pH increases. Ultrasound treatment on the used membrane leads to a partial membrane regeneration, but it is far from regenerating the initial membrane separation properties.