Reclamation of mature Bambusa bambos (L.) Voss culms into activated carbon for adsorptive removal of Bisphenol A

Abstract

This study deals with the sustainable conversion of mature Bambusa bambos culms into activated carbon (AC) for removal of Bisphenol A (BPA) from aqueous solutions, supporting the principles of the circular bioeconomy. AC was synthesized by chemical activation with orthophosphoric acid, with a BET surface area of 903.7 m²/g and average pore diameter 2.62 nm. SEM analysis of synthesized AC revealed an irregular rough porous surface, which became smoother with partial pore filling after BPA adsorption. The EDAX spectrum of BPA treated AC showed a slight decrease in carbon content (83.13 – 87.43 %), while the oxygen content increased (10.01 – 15.65 %), compared to untreated AC. FT-IR analysis indicated shifts in peaks corresponding to -O-H, -CC and -CO stretching vibrations, alcoholic or ether groups and C-H out of plane bending vibrations after BPA adsorption, indicating hydrogen bonding, dipole-dipole interactions and π-π stacking as dominant adsorption forces. Batch adsorption studies showed maximum adsorption efficiency (80.68 %) at 20 mg/L BPA, 0.4 g/L AC dosage, pH 4.0, at 35 ºC, 125 RPM in 2 h. Adsorption followed pseudo second order kinetics (R² = 0.999) and Temkin isotherm (R² = 0.969), confirming strong adsorbent adsorbate interactions and a gradual decrease in adsorption heat. Thermodynamic analysis confirmed that adsorption is spontaneous and exothermic (ΔG°= −5.20 - −7.26 kJ/mol), driven by strong physisorption (ΔH° = –36.5 kJ/mol), with decreased randomness on the solid-solution interface (ΔS°= –98.6 J/mol). These results demonstrate that mature Bambusa bambos culms are a suitable precursor for conversion into AC for BPA remediation.