Fabrication of NH2-MIL-125 (Ti)/Polyvinylidene fluoride hollow fiber mixed matrix membranes for removal of environmentally hazardous CO2 gas

Abstract

Improper pairing of filler and polymer together with inappropriate filler loadings into polymer matrix may lead to structural defects such as large aggregations and interface void formations. Subsequently, the structural defects may sacrifice the selectivity of CO2 over CH4, which was unfavorable. In the current work, NH2-MIL-125 (Ti) (MIL = Material Institute Lavoisier), which possesses NH2-groups and theoretically capable of forming strong hydrogen bonding with F-groups of polyvinylidene fluoride (PVDF), was selected to spin hollow fiber mixed matrix membranes (HFMMMs). Besides, NH2-MIL-125 (Ti) can interact better with CO2 over CH4 via quadrupole moment, and NH2-groups also aid in CO2 selectivity due to its high CO2 adsorption capability. The HFMMMs were spun using a dry-wet spinning technique of filler loadings percentage ranging from 1 to 3 wt percent (wt%). The effect of filler and loadings percentage over HFMMMs properties, including contact angle, mechanical strength, thermal stability and cross-sectional morphology was investigated. The compatibility at interface of filler and polymer was observed to be good, and dispersion was observed to be acceptable up to 2 wt% filler loadings. However, apparent aggregation was observed beyond this point. The wt% of Ti, O, and N elements were found to increase from 0.72 to 2.05, 3.27 to 4.53, and 0.52 to 1.55, respectively, with increasing filler loading into HFMMMs. Subsequently, PVDF-2 membrane displayed the highest CO2/CH4 ideal selectivity with contact angle of 83.44 ± 1.45, ultimate tensile strength (UTS) of 1.33, 29.12 Young's Modulus, and 72.2% elongation at break. Therefore, optimizing loading percentage and selecting appropriate filler are considered practical methods to ensure good morphology and better hazardous CO2 removal.