FOULING DURING ULTRAFILTRATION OF A LOW-MOLECULAR-WEIGHT HYDROPHOBIC SOLUTE

The influence of a small hydrophobic solute (octanoic acid) on the flu x reduction and the flux recovery of two ultrafiltration membranes was studied in this investigation. The two membranes were made of polyeth er sulfone and regenerated cellulose, both with a nominal molecular we ight cutoff of 20,000 Da. The concentration of the octanoic acid solut ion was found to have a significant influence on not only the extent o f flux reduction during treatment of the octanoic acid solution, but a lso on the flux recovery when the membrane was rinsed with deionized w ater. After treatment of the octanoic acid solution, a pure water flux increase of 1.5 times the pure water flux of the new, unused polyethe r sulfone membrane was observed. Different causes of the increased pur e water flux after treatment of the octanoic acid solution are present ed, and the serious consequences this apparent positive effect can cau se in industrial applications are discussed.