Synthesis and Characterization of Electrospun Carbon Quantum Dots – Polyacrylonitrile/Polycaprolactone Composite Nanofiber Membranes for Copper (II) Adsorption

Abstract

Heavy metal adsorption (HMA) is one of the remediation techniques used to remove heavy metals from water/wastewater. Composite membranes with functionalized additives for selective adsorption are being investigated. In this study, Carbon Quantum Dots – Polyacrylonitrile/Polycaprolactone nanocomposite membranes are synthesized by electrospinning which is intended for HMA of Cu2+. The nanofiber mats were characterized using SEM, FTIR, and Contact Angle. Batch adsorption process were performed and to utilize the AAS for kinetic adsorption behavior analysis. SEM micrographs revealed the addition of CQD in PAN and PAN/PCL membrane matrix shifted the fiber size distribution from 50 – 100 nm to 150 – 250 nm indicates the decrease in effective surface area. FTIR analysis exhibited vibrational peaks and binding of distinct functional groups such as amine, nitrile, carboxylic, hydroxyl, and carbonyl for CQD, PAN and PCL, respectively. CQD in aqueous form further increases the hydrophilicity of PAN/PCL membrane matrix which is essential for HMA of Cu2+ ions. The increase of nanofiber mat’s adsorption capacity with respect to contact time obtained a maximum at 63.45 mg/g with a maximum efficiency of adsorption at 90.74%. Kinetic adsorption studies show that the pseudo – first order kinetic model best fits the data for CQD – PAN/PCL nanofiber mat in Cu2+ ions obtaining a correlation value of R2 = 0.9418 and a rate constant k = 0.0172 min1 indicating the adsorption behavior follows the physical adsorption process involving Van der Waals forces and hydrogen bonding between the adsorbent and adsorbate.

Carbon quantum dots (CQDs)-modified polymers: a review of non-optical applications

“…One of the purification methods for removing heavy metals from wastewater is heavy metal adsorption (HMA). 72 Composite membranes containing functionalized additives for the adsorption of particular ions are useful in this regard. The electrospinning technique was used to fabricate carbon quantum-dot-polyacrylonitrile/polycaprolactone (CQD-PAN/ PCL) nanofibrous membranes, suitable for Cu 2+ HMA.…”

“…The electrospinning technique was used to fabricate carbon quantum-dot-polyacrylonitrile/polycaprolactone (CQD-PAN/ PCL) nanofibrous membranes, suitable for Cu 2+ HMA. 72 Firstly, CQDs were synthesized using a hydrothermal method and were then loaded into PAN/PCL at a 4 wt% concentration. The diameter of the CQD composite nanofibers was slightly increased, forming a uniformly distributed fibrous network.…”

“…4 CQD-modified polymers for membrane applications: (a) schematic representation of the membrane structure before and after solvent evaporation, where the CQDs offer strong affinity with the -SO 3 H groups in the Nafion side chain; 65 (b) loading of CQDs into the polyamide binder applied as an overlayer on the surface of the PSF membrane; 66 (c) film formation without CQD/PVA leads to a defect-rich morphology, and the strong interactions of the CQD/PVA allow a defect-free compact and uniform coating of the polyamide overlayer; 70 (d) and (e) adsorption capacity and efficiency of Cu 2+ ions using the CQD-PAN/PCL membrane. 72 and efficiency levels of 63.45 mg g −1 and 90.74%, respectively [Fig. 4(d and e)].…”

Polycaprolactone Composites/Blends and Their Applications Especially in Water Treatment

“…CQD in PAN and PAN/PCL membrane magnified the fiber size distribution from 50-100 nm to 150-250 nm, increasing the hydrophilicity of the PAN/PCL membrane. The physical adsorption method, which involves VDW forces and hydrogen bonds between adsorbent and adsorbate, governs the adsorption behavior [132].…”