Rapid removal of Rhodamine B by phosphoric acid-modified activated carbon derived from rape straw

A series of activated carbon was obtained from rape straw by chemical modification with phosphoric acid (H₃PO₄). The activated carbon was characterized and the adsorption capacity for Rhodamine B (RhB) from water was analysed. The SEM images showed that PRC-40 is a porous material and the BET analysis revealed a high surface area of 1720 m²/g with the coexistence of micropores and mesopores. The FTIR spectra determined the presence of oxygenated functional groups at its surface. The XPS spectra revealed that the content of carboxyl and metaphosphate groups in the modified activated carbon significantly increased, and this is conducive to the adsorption reaction. The XRD pattern showed the amorphous nature of carbon. The effect of significant parameters, such as the concentration of H₃PO₄ for modification and pH value, has been discussed. The kinetic data showed that the pseudo-second-order model is predominant. Besides, the Langmuir model was compatible well with the equilibrium data, and the maximum adsorption capacity of the activated carbon modified by H₃PO₄ was 2882.84 mg/g. Therefore, agricultural waste and rape straw can be used to prepare effective adsorbents for the application with the removal of dye from wastewater.