The performance of phosphoric acid in the preparation of activated carbon-containing phosphorus species from rice husk residue

The performance of phosphoric acid (H₃PO₄) in the preparation of activated carbon-containing phosphorus species (P-species) using rice husk residues as feedstock was studied. In the activation process, the consequent pretreatments by NaOH and HCl, respectively, remove the silica and ash thoroughly, which led to cracks and pore opening. While H₃PO₄ acting as activation regent interacted with the phenolic and carbonyl groups of activated carbon, forming P-containing carbonaceous species (such as C–O–P), which further promoted the development of micropore of the activated carbon and then increased the surface area, H₃PO₄ also acted as catalyst to adjust and control the texture properties and structures of activated carbon. The activated carbon (PC-2.5) prepared at 500 °C for 2 h using H₃PO₄-treated carbon residue with acid/carbon mass ratio of 2.5 (g/g) achieved the maximum surface area of 1365 m²/g. Interestingly, the P-species formed in the activated carbon exhibited high-efficiency catalytic effects for the treatment of municipal waste landfill leachate to a disposable quality, where the removal rate of pollutant from landfill leachate over 90% and a high removal of TN (84%), COD (82%) and NH₄⁺–N (100%) were obtained.