Abstract
In this study, the potential of graphene oxide-alginate beads (GO-AB) as an adsorbent for bisphenol A (BPA) removal from aqueous solution was investigated. GO was first prepared via modified Hummers’ techniques and an aerogel alginate bead with embedded GO was prepared using an extrusion dripping method, where calcium chloride was utilized as a curing agent. The physicochemical characteristics of GO-AB were investigated using XRD, FTIR, BET, TGA. The results revealed that crystal structure and the surface groups of GO and alginate were retained upon the formation of GO-AB. A batch adsorption testing was carried out as a function of pH (3, 7, and 9), contact time (up to 420 min) and initial concentration of BPA (50—200 mg·L−1). The adsorption rate was typically faster at the beginning of the adsorption process and started to level off after 180 min. AB and GO-AB had better adsorption performances at neutral condition (pH 7) than alkaline and acidic environments due to repulsive electrostatic interaction between BPA and the adsorbent surface’s charge. The sorption kinetic data was observed fitted to the pseudo-second-order kinetics model (R2 > 0.98) and obeyed the Freundlich isotherm model adsorption behaviour compared to Langmuir. However, the RL value of Langmuir model is between 0 and 1, which implies a favourable adsorption process. The maximum BPA adsorption capacity for AB and GO-AB was found to be 250.00 and 384.62 mg·g−1, respectively, indicating that GO-AB is a promising adsorbent for BPA removal from aqueous solution. In addition, the adsorption efficiency of GO-AB exhibited more than 80% in the six-consecutive adsorption–desorption cycles of experiments, further confirming the excellent reusability of GO-AB.
Highlights
Bisphenol A (BPA) is among the most utilized monomer in production of various polymers such as epoxy resins, polycarbonates, polysulfone (PS) resins and other types of plastics (Yang et al 2011; Seachrist et al 2016; Almeida et al 2018)
The extruded graphene oxide-alginate beads (GO-alginate bead (AB)) beads were generally bigger than AB due to the high viscosity of Graphene oxide (GO)-AB solution owing to the addition of GO
AB and GO-AB were not stable and started to lose mass rapidly at the beginning of the heating up process up to 80% and 60%, respectively
Summary
Bisphenol A (BPA) is among the most utilized monomer in production of various polymers such as epoxy resins, polycarbonates, polysulfone (PS) resins and other types of plastics (Yang et al 2011; Seachrist et al 2016; Almeida et al 2018). Adsorption is an adhesion process of atoms, ions, or molecules from liquid, gas or dissolved solid, which creates an adsorbate film on the surface of adsorbent(Sophia A. and Lima 2018). It is one of the water remediation technique that has been widely utilised due to versatility of the process, higher removal rate of chemical pollutants, simple setup, relatively low cost, simple operation, and produces minimal harmful secondary products (Ersan et al 2017). The adsorbents should possess high adsorption capability, rapid adsorption rate, and specific surface reactivity
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