Fly ash/2-hydroxy-3-methoxybenzaldehyde/graphene composite as an adsorbent for bisphenol-A removal from aquatic environment: Synthesis, adsorption characteristics and mechanism

Fly ash (FA) as inexpensive waste material was modified with 2-Hydroxy-3-methoxybenzaldehyde (HMBA) and Graphene (GP) (FA/HMBA/GP) for powerful removal of Bisphenol-A (BisP-A) from aqueous media. The synthesized FA/HMBA/GP composite material was characterized for chemical characterization and surface morphology by Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) before and after adsorption. Factorial design using response surface methodology (RSM) in the central composite design (CCD) method was used to examine the significance of contact time, pH, BisP-A concentration, and adsorbent dosage throughout the adsorption of BisP-A. Analysis of variance (ANOVA) investigated significant interactions among these variables. Adsorption isotherm fitted well with Langmuir model for BisP-A removal on FA/HMBA/GP with obtained maximum removal capacity of 302.7 mg g⁻¹. Langmuir isotherm and Pseudo-second-order could express the adsorption process which is controlled by both chemisorption and monolayer adsorption. Electrostatic attractions, hydrogen bonding, and n-π interactions were attributed to the removal mechanism for BisP-A by FA/HMBA/GP. The composite was used for four times-adsorption/desorption cycles without significant adsorptive performance loss. Results of the present work suggested that the eco-friendly prepared FA/HMBA/GP composite can be evaluated for the separation of BisP-A from contaminated water.