Accessibility of adsorption sites for superfine powdered activated carbons incorporated into electrospun polystyrene fibers

Abstract

Superfine powdered activated carbon (SPAC) is sub-micron sized activated carbon with superior adsorption kinetics compared to regular powdered activated carbon (PAC) due to the short intraparticle diffusion times. SPAC has recently been demonstrated as an excellent adsorbent; however, subsequent removal of spent SPAC in suspended reactors may be challenging due to its fine size. Thus, SPAC may benefit from immobilization into a macroscopic scaffolding if its adsorptive properties can be preserved. Composition of non-woven electrospun polystyrene (PS) fibers consisting of SPAC is a novel approach to immobilize SPAC; however, the potential losses of adsorption capacity due to polymer-SPAC interactions is still mostly unknown. In this study, SPAC-laden electrospun PS with intentionally tuned SPAC sizes were fabricated for the first time. The centrifugal separation of SPAC generated two different particle sizes with median diameters of 0.30 ± 0.15 µm (SPAC-Fine) and 0.62 ± 0.25 µm (SPAC-Coarse). Both SPAC-Fine and SPAC-Coarse were added to the spinning solution and compared against the PS-only control fibers. Phenanthrene was used as a probe molecule to investigate the accessibility of adsorption sites on PS/SPAC composite fibers. This study showed that most SPAC adsorption sites are still accessible when incorporated into electrospun polymer fibers, regardless of whether the carbon particle size is larger or smaller than the fiber diameter. It can be speculated that the disposition of fine particles on the external surface of PS fibers as well as partial incorporation of large SPAC particles in the fiber allow diffusion of probe molecules onto the ultimate sorption sites of SPAC particles.