Reductant-assisted polydopamine-modified membranes for efficient water purification

Surface engineering with polydopamine coatings has been considered a promising surface functionalisation tool.However,it is difficult to control the self-polymerisation for polydopamine formation,which usually causes severe interparticle aggregation.In this study,polydopamine self-polymerisation was controlled by adjusting its reducing environment using a reductant(NaBH4)to fabricate mixed cellulose ester(MCE)/polydopamine membranes.An oxidising environment using NaIO4 was additionally tested as the control.The results showed that a thin polydopamine coating with small polydopamine particles was formed on the skeleton frameworks of the MCE membrane with NaBH4,and the self-polymerisation rate was suppressed.The polydopamine coating formed in the reducing environment facilitated excellent water transport performance with a water permeance of approximately 400 L·m^(−2)·h^(−1)·bar^(−1) as well as efficient organic foulant removal with a bovine serum albumin rejection of approximately 90%.In addition,the polydopamine coating with NaBH4 exhibited both excellent chemical stability and anti-microbial activity,demonstrating the contribution of the reducing environment to the performance of the MCE/polydopamine membranes.It shows significant potential for use in water purification.