Assessing potential of nanofiltration and reverse osmosis for removal of toxic pharmaceuticals from water

Concern about organic micropollutants, which are present in the environment at trace concentrations (ng L-1-mu g L-1) is related to the adverse effects to organisms exposed to these substances. Pharmaceutically Active Compounds (PhCAs) may be present in natural waters and usually cannot be removed or degraded by conventional water treatment processes. For this reason, treatment techniques, such as Nanofiltration (NF) and Reverse Osmosis (RO) are recommended to improve their removal. In this context, the present study aims to evaluate the removal of five Non-steroidal anti-inflammatory drugs (NSAIDs), analgesics and anti-pyretic: acetaminophen, ibuprofen, dipyrone, diclofenac, and caffeine by NF and RO process. NF90 and BW30 membranes were characterized by scanning electron microscopic (SEM), contact angle and zeta potential. Retention of PhACs was evaluated considering pH feed solution and operating pressure. Results indicated that NF90 membrane was efficient to reach over 88% rejection for some selected PhACs. Best results were obtained at 20 bar and pH 5 with more than 90% of rejection. For nonionic compounds acetaminophen and caffeine, exclusion by size is the main mechanism for rejection by NF90 membrane, whereas for anionic compounds ibuprofen, dipyrone, and diclofenac, electrical exclusion predominated at pH 5 and 7. Rejection results with NF90 membrane show that hydrophobicity has an important role due to the adsorption on the membrane surface. Conversely, lower rejections for hydrophilic compounds were observed due to the adsorption/diffusion mechanisms, both in NF90 and RO at pH 5.