Incorporation of zwitterionic carbon quantum dots in cellulose acetate tubular membrane for oil/water separation

Abstract

The substantial generation of oily industrial wastewater poses a considerable environmental threat. A promising strategy for addressing this challenge involves employing ultrafiltration membranes integrated with a hydrophilic nanomaterial. This study aims to investigate the properties of zwitterionic carbon quantum dots (ZQDs) and enhance the performance of cellulose acetate (CA) tubular membranes by incorporating ZQDs. The CA tubular membrane was crafted using the dry-wet spinning method. The introduction of ZQDs into the CA casting solution disrupted its thermodynamic stability and expedited the non-solvent inflow rate during membrane formation, thereby augmenting both membrane porosity and pore size. The inclusion of ZQDs heightened the membrane's hydrophilicity owing to the presence of hydrophilic functional groups in the nanomaterial. The modified tubular membrane demonstrated high pure water and diesel oil-water emulsion permeate flux of 581.3 ± 33.9 L m−1 h−1 bar−1 and 350.5 ± 11.2 L m−1 h−1 bar−1, respectively, with an impressive oil rejection rate of 98 %. The flux recovery and reversible fouling ratio increased to 88.42 % and 28.12 %, respectively, while the irreversible fouling ratio decreased to 11.57 %. The modified tubular membrane effectively rejected various oil-water emulsions (diesel oil, dodecane, canola oil, and engine oil) with a separation efficiency ranging from 94 % to 99 %. In conclusion, the zwitterionic-modified tubular membrane proved to be effective in the separation of oil and water.