Application of dopamine-modified halloysite nanotubes/PVDF blend membranes for direct dyes removal from wastewater

Membrane technology has been successfully applied for the removal of dyes from wastewater in the textile industry. In this work, halloysite nanotubes (HNTs) were functionalized with dopamine (DA) firstly, and then a series of novel polyvinylidene fluoride (PVDF) membranes were prepared via blending with different dosages of DA grafted HNTs (D-A-HNTs). The characterizations of nanoparticles (NPs) confirmed the reaction between DA and HNTs. The morphologies of membranes were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM), which indicated that D-A-HNTs had a good dispersity in membrane matrix and also improved the microstructure of membranes. The experimental results demonstrated that the D-A-HNTs modified membranes were presented to be more hydrophilic, with a pure water flux (PWF) as high as 42.2   L   m −2   h −1 , which increased by 80.3% compared with pure PVDF membrane. The dye rejection ratios were also improved after adding D-A-HNTs, which reached 86.5% for Direct Red 28, 85% for Direct Yellow 4 and 93.7% for Direct Blue 14, respectively. More importantly, the anti-fouling test revealed that the blend membranes showed excellent anti-fouling property after several cycles. As a result, this study could have a great potential to widen the applications of membrane to treat textile wastewater.