Properties of polyvinyl chloride (PVC) ultrafiltration membrane improved by lignin: Hydrophilicity and antifouling

Usually seen as a waste with low chemical value and limited commercial potential, lignin produced in large quantity from paper industry performs abundant valuable hydrophilic groups which make it a potential hydrophilic assistant. In this contribution, in order to improve hydrophilicity and antifouling properties of PVC ultrafiltration membrane, lignin was doped into PVC to prepare a uniform sol under strengthening heat and mass transfer process, and then PVC/lignin ultrafiltration membranes were prepared via phase inversion strategy. The resulted PVC/lignin ultrafiltration membranes were characterized by SEM, FT-IR, XPS, DSC and were also tested by oily wastewater. According to the results of SEM, XRD and DSC analyses, PVC is compatible with lignin and the homogeneous PVC/lignin sol can be formed. The hydrophilicity of membrane is significantly enhanced with water contact angle (WCA) decreasing from 106.73 degrees to 41.53 degrees. Particularly, the PVC/lignin ultrafiltration membranes exhibit attractive properties with oil rejection of 97.36% and oily wastewater permeation flux of 156.55 L m(-2) h(-1) (0.1 MPa), nearly 2.5 times that of pure one (65.06 L m(-2) h(-1)). Lignin suggests to be a superior additive to improve hydrophilic and anti-fouling properties of PVC membranes, and the lignin-modified membranes are promising candidates for cleaning oily wastewater and sewage.