Activated carbon nanofibers nonwoven flat sheet for methylene blue dye adsorption: batch and flow-through systems

In this study, a flat sheet of electrospun activated carbon nonwoven nanofiber (ACN) based on polyacrylonitrile polymer was fabricated and characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET). The SEM analysis showed that the prepared ACN mat consisted of long and bead-free nonwoven nanofibers with an average diameter of 600 nm. The BET analysis of ACN showed that the pores were mesoporous pores with a size of 3.7 nm and a specific surface area of 450 m2/g. The obtained ACN was used to evaluate the removal of methylene blue (MB) dye from aqueous medium water using batch and flow-through modes. In batch mode, ACN reveals a removal efficiency of up to 90% at the optimum parameter conditions (i.e., pH 7, 100 mg adsorbents, 10 mg/L initial concentration, and room temperature). The adsorption process was well described by the Freundlich isotherm and pseudo-second-order kinetic model with the highest 24.7 mg/g MB dye adsorption capacity. To investigate the effectivity of the ACN nonwoven sheet in a continuous adsorption system, a novel flow-through cell was designed for using nonwoven nanofiber sheets as an adsorbent. The innovative design allows the feed solution to flow within the nanofiber assembly and thus provides a more reachable surface area and longer residence time. Adsorption experiments showed characteristic breakthrough actions in the flow-through process. The breakpoint period was 40 min to treat 25 mL/h of MB dye solution (10 mg/L) in the flow-through system using one layer of 6 cm of ACN mat. In addition, it was found that breakpoint time increased as feed flow decreased, the bed height increased, and the number of ACN mat layers increased due to increasing adsorption sites.