Performance, Mechanism And Application Research On Solibilization And Retention Of Aqueous Phenol By Using Micellar-enhanced Ultrafiltration

Performance, mechanism and application of solubilization and retention of phenol by using micellar-enhanced ultrafiltration (MEUF) are studied in this paper. A cationic surfactant, cetylpyridinium chloride (CPC), is used for forming micelles and two spiral polysulfone membranes are used for ultrafiltration. Effects of operation parameters on the performance of solubilization and retention of phenol by using MEUF are investigated systemically. The way of improving the performance of solubilization and retention of phenol by using MEUF is studied to decrease permeate concentrations and increase concentration ratios of phenol and CPC. By using HNMR (nuclear magnetic resonance), mechanism and process of solubilization of phenol in CPC micelle are analysed and discussed. The pilot study on seperation and reclamation of phenol and CPC by using chemical precipitation is conducted.Three types of surfactant, anionic SDS (sodium dodecyl sulfate), cationic CPC and non-ionic Tritonx-100 are used as surfactant in MEUF of phenol. Only CPC has good solubilization capability for phenol. So CPC is determined to be used for forming micelles in the following researches. The operation mode is the key to restrain the concentration polarization and has an important effect on the performance of ultrafiltration. The mode of circulating the retentate stream should be conducted. MEUF of phenol is studied using two spiral polysulfone membranes of P6 (MWCO=6000) and P10 (MWCO=10000) and CPC as surfactant. Effects of operation parameters (concentrations of phenol and CPC, MWCO of membrane, retentate flux, operating pressure, temperature and pH) on permeate flux, rejections and concentratings as well as adsorptions on membranes of phenol and CPC are investigated. In order to improve the performance of MEUF of phenol, SDS, Tritonx-100 and electrolytes (NaCl,Na₂SO₄ and Na₂CO₃) are mixed with CPC, respectively. It is found that the effect of electrolyte is good and the order of effect is Na₂CO₃>Na₂SO₄>NaCl. Effects of electrolytes on the self-assembly of CPC micelle are investigated from the point view of surface tension, size and zeta potential of micelle and the reason of improvement of performance of MEUF of phenol by adding electrolytes is revealed. By using HNMR, process and mechanism of CPC solubilizing phenol are analysed. The result shows that the solubilization of phenol in CPC micelle depends on the electrostatic attraction between phenol and N+ of headgroup of CPC micelle as well as the hydrophobic effect between phenyl and core of CPC micelle. Furthermore, the former has major effect, and the latter has minor effect only when the phenol concentration is relatively high. The existence of Na2CO3 can force the phenolic ions adsorbing on the CPC micelle surface to move to the core of CPC micelle along the hydrocarbon chain, but they do not enter the core and just are closer to the core. Chemical precipitation is used to separate and reclaim phenol and CPC in retentate streams of adding and not adding Na2CO3. The result shows that the effect of chemical precipitation is not very good, so it is necessary to find more convenient and effective technique.This study shows that MEUF using CPC and spiral polysulfone can solubilize and reject phenol in water effectively and quickly, and the existence of Na2CO3 can improve its performance significantly and increase the rejection and concentration ratios of phenol and CPC remarkably. In this study, Nano-Zs apparatus is used to reveal the reason of improvement of performance of MEUF of phenol by adding electrolytes from the point of view the characteristics of self-assembly of CPC micelle. HNMR is used to analyse and discuss the process and mechanism of solubilization of phenol in CPC micelle.In this paper, keys including parameters of control, process optimization, process and mechanism of solubilization of phenol in CPC micelle are studied and discussed.This study provides foundation for application and popularization of phenol-containing wastewater treatment by MEUF and has good theoretic significance and application prospect.