Abstract
Polydopamine has been widely used as an additive to enhance membrane fouling resistance. This study reports the effects of two-step dopamine-to-polydopamine modification on the permeation, antifouling, and potential anti-UV properties of polyethersulfone (PES)-based ultrafiltration membranes. The modification was performed through a two-step mechanism: adding the dopamine additive followed by immersion into Tris-HCl solution to allow polymerization of dopamine into polydopamine (PDA). The results reveal that the step of treatment, the concentration of dopamine in the first step, and the duration of dipping in the Tris solution in the second step affect the properties of the resulting membranes. Higher dopamine loadings improve the pure water flux (PWF) by more than threefold (15 vs. 50 L/m2·h). The extended dipping period in the Tris alkaline buffer leads to an overgrowth of the PDA layer that partly covers the surface pores which lowers the PWF. The presence of dopamine or polydopamine enhances the hydrophilicity due to the enrichment of hydrophilic catechol moieties which leads to better anti-fouling. Moreover, the polydopamine film also improves the membrane resistance to UV irradiation by minimizing photodegradation’s occurrence.
Highlights
Polydopamine (PDA) has been known as an important biocomponent in the medical field, material coating, and an effective additive for membrane fabrication [1,2,3]
The analysis shown here is only for pristine PES (P), the membrane with low dopamine concentration and short polymerization time (P-D5-a), high dopamine concentration and short polymerization time (P-D5-c), and high concentration and long polymerization time (P-D36-c)
It is distinguished by the catechol-amine moiety, specific to dopamine, appearing at the spectrum range of 3300–3600 cm−1
Summary
Polydopamine (PDA) has been known as an important biocomponent in the medical field, material coating, and an effective additive for membrane fabrication [1,2,3]. If the PDA blended with the polymer, the photocatalytic efficacy diminishes because the photocatalysis occurs only on the surface [27] Another employed a simple dip-coating in an aqueous solution of dopamine and utilized dopamine self-polymerization to form thin surface-adherent polydopamine films onto various materials in which secondary reactions can be used to create a variety of ad-layer [29]. This study focuses on the role of PDA additive as an anti-fouling agent and anti UV degradation agent and high filtration performance. Such properties are important for membrane materials used in photocatalytic membrane reactors because the presence of the PDA layer can be functionalized with semiconductor photocatalytic particles
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