Sm-MOF decorated cotton for efficient on-demand oil-water separation and organic pollutants removal

Abstract

Complex wastewater containing oil–water and contaminant mixtures is a constant threat to ecosystems and public health. However, efficient water–oil separation and water treatment are required, with a preference for simple but universal matrices for possible large-scale applications. Herein, effective oil–water separation and organic pollutant removal are simultaneously realized on cotton balls decorated with polydimethylsiloxane combined with a samarium metal–organic framework. Cotton balls containing polydimethylsiloxane (10 %) and Sm-MOF (Synthesis temperature was 110 ℃, 15 mg/L) were successfully prepared by a simple precipitation method, with a high water contact angle of 150.75 ± 1.1°. After pre-wetting with a low surface energy solution, the modified cotton was endowed with repeatable super-wetting transitions between superhydrophobic/superoleophilic and superhydrophilic/underwater superoleophobic properties. In addition to on-demand separations of immiscible oil–water mixtures at a rate of 95 %, water-in-oil emulsions could be separated by the addition of different surfactants. The mechanism of demulsification of the treated cotton ball was studied based on the type of emulsifier and the results of emulsified oil separation. Cotton balls modified with 10 % PDMS and Sm-MOF (Synthesis temperature was 140 °C; 15 mg/L) showed higher adsorption capacity compared to pure cotton balls, adsorbing about 98.7 % of Eriochrome Black T within 2 h. Cotton balls modified by PDMS and Sm-MOF are an effective, safe and green material with promising applications in the simultaneous separation of oil–water mixtures and removal of organic pollutants from water systems.