Fabrication of sponge-like pH-responsive absorbent with gas foaming technique for oil water separation

Abstract

Oily wastewater must be discharge after ensuring post-treatment due to its high risk of water pollution. There are various methods such as membrane technology, pyrolysis and land farming to purify waste water containing oil emulsion. Among them, membrane processes are dominant which requires high pressure. For high pressure, a lot of energy is consumed, which leads to an increased cost burden. In order to overcome this problem, the facility which can be used as semi-permanent process and consume less energy is necessary. And the absorbent treatment will be suitable due to its reusability and simplicity. In this study, poly(ethersulfone-co-2-(dimethylamino)ethylmethacrylate (PES-co-PDMAEMA) is used for oil water separation. It is synthesized to prevent the collapse of the nanofiber structure when pristine PDMAEMA is used for water treatment. It is made through the atom transfer radical polymerization (ATRP), which is a method of radicalizing PES and propagate with DMAEMA monomer. And this copolymer is fabricated as nanofiber mat via electrospinning technique. The gas foaming method is based on the principle of expanding the volume of the mat by pushing the fiber via generation of hydrogen gas from sodium borohydride (NaBH4). The gas foamed absorbent showed 10 times higher capacity than the nanofiber mat without gas foaming treatment. According to the result of purification test of oil/water emulsion, 98% of oil is removed by PES-co-PDMAEMA absorbent. PESco-PDMAEMA showed maximum water affinity at pH3, and showed a rapid decline of hydrophilicity between pH5 and pH7 due to pH-responsive property of PDMAEMA. Finally, it showed consistent performance during 5 cycles of reusability test. This is new approach of oil-water separation method that using gas foamed electrospun nanofiber membrane for oil absorption and desorption through adjusting pH condition. Since the time required for absorption is short and the regeneration process is relatively simple, it is highly useful for purification of oil emulsion, so it potentially solve the problem of contamination by wastewater containing oil emulsion.