Phosphate adsorption characteristics of La(OH)3-modified, canna-derived biochar

La(OH)3-modified canna biochar (CBC-La) was prepared by a coprecipitation method (dipping method), and its phosphate adsorption characteristics were investigated. The results show that the pseudo-second-order kinetics and the Langmuir model can be used to describe the adsorption process with a high level of accuracy. Adsorption equilibrium could be reached at 8 h, at which point the maximum adsorption capacity was shown to be 37.37 mg/g. CBC-La has excellent phosphate adsorption capacity in the middle to low concentrations (<= 50 mg/L), and its removal rate can exceed 99 %. CBC-La also has wide pH adaptability (3-9) and a strongly selective adsorption performance. Notably, it can still maintain a removal rate of over 99.8 % in the presence of certain anions (NO3 , HCO3 , and CO32 ), and the presence of NH4+ has a synergistic effect on the adsorption process. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) measurements demonstrate that the main mechanisms of CBC-La phosphate adsorption are electrostatic adsorption, ion exchange, ligand exchange and inner sphere complexation.

Automated summary

The La(OH)3-modified canna biochar (CBC-La) exhibits excellent phosphate adsorption capacity, wide pH adaptability, and high selectivity. The main mechanisms of phosphate adsorption by CBC-La include electrostatic adsorption, ion exchange, and inner sphere complexation.