Separation of aromatic alcohols using micellar-enhanced ultrafiltration and recovery of surfactant

The removals of single aromatic alcohols, including para nitro phenol (PNP), meta nitro phenol (MNP), phenol (P), catechol (CC), beta napthol (BN) and ortho chloro phenol (OCP) from aqueous solution have been studied using micellar-enhanced ultrafiltration (MEUF). Cetyl (hexadecyl) pyridinium chloride (CPC) has been taken as the cationic surfactant. An organic polyamide membrane of molecular weight cut-off 1000 is used in the MEUF experiments. Experiments are conducted using unstirred batch cell and a continuous cross flow cell. The effects of surfactant-to-solute concentration ratio in the feed, transmembrane pressure drop and cross flow rate on the permeate flux and observed retention of each solute have been studied in detail. The retention of solutes without using surfactant varies from 3 to 15% only at a typical feed solute concentration of 0.09 kg/m3. However, under the same operating pressure (345 kPa), retention increases to about 66–98% depending on the nature of solute at the end of 30 min of experiment in the batch cell using surfactant micelles (10 kg/m3). The maximum retention of solute is obtained at surfactant-to-solute concentration ratio of 110. Free surfactant molecules present in the permeate and retentate are then recovered by a two-step chemical treatment process. In the first step, the surfactant is precipitated by potassium iodide and in the second step, the surfactant is recovered from the precipitate by the addition of cupric chloride. Optimum consumptions of potassium iodide and cupric chloride are also obtained experimentally.