Adsorption of bisphenol A by phosphoric acid activated puffing carbon and the enhancing effect of pre-wetting treatment

Phosphoric acid activation has been recognized as an effective method for synthesizing high-performance activated carbon, while expansion pretreatment of native biomass materials such as rice can induce instantaneous volumetric expansion to generate abundant micropores, offering novel perspectives for carbon material design. However, the synergistic mechanisms between expansion treatment and phosphoric acid modification remain unclear. Moreover, the conventional microporous suffer from limited accessibility of adsorption sites due to strong capillary resistance that impedes complete water molecule infiltration into partial internal surfaces. In this study, activated carbons were prepared through a coupled expansion-phosphoric acid activation approach to investigate the combined effects of these treatments on the physicochemical properties of carbon materials. Bisphenol A (BPA) was selected as a model pollutant to evaluate adsorption enhancement induced by modification. Ultrasonic and vacuum-assisted prewetting treatments were employed to elucidate the regulatory role of microporous site accessibility in adsorption performance. The results demonstrated that expanded activated carbon (P) and phosphoric acid-expanded activated carbon (HP) exhibited substantial improvements in specific surface area (up to 1023.8 m2·g−1 for HP) and total pore volume (0.53 cm3·g−1 for HP), primarily attributed to newly formed micropores. In contrast, conventional activated carbon (C) showed structural collapse after acid treatment (HC), resulting in reduced specific surface area and pore volume. HP displayed superior BPA adsorption capacity, approximately 4-fold higher than HC and nearly 10-fold greater than P and C. Ultrasonic and vacuum treatments further enhanced BPA adsorption on HP by about30%. 1H NMR analysis revealed increased wetted specific surface area in HP after prewetting, confirming improved accessibility of adsorption sites.