posted on 2024-04-26, 19:04authored byYan Li, Lili Dong, Xingyu Ren, Hao Liu, Chenjia Zhang, Shunli Wan
A new biochar (N-BC)
was fabricated by incorporating high-density
positively charged quaternary ammonium groups into the pristine biochar
without any adsorption for phosphate. N-BC can highly efficiently
remove phosphate with an optimal pH of 5.0, a maximum experimental
adsorption capacity of 30 mg of P/g, and an adsorption equilibrium
time of 180 min. The predicted pore diffusion coefficient D (the diffused surface area of the adsorbate for unit time)
for phosphate adsorption by N-BC was 5.3 × 10–9 cm2/s. N-BC can still capture phosphate in the copresence
of anion Cl– with a molar concentration 50 times
that of phosphate. The exhausted N-BC was completely regenerated using
a 10 wt % NaOH solution and further reused without any observable
loss in adsorption capacity. Moreover, N-BC yielded ∼324 bed
volumes (BV) of wastewater containing 1 mg P/L phosphate and 50 mg/L
Cl– before breakthrough occurring (<0.1 mg P/L
in effluent) in a fixed-bed column operation system. The introduced
quaternary ammonium groups covalently bound to biochar played a dominant
role in phosphate sequestration by N-BC through forming the out-sphere
complexation with phosphate. All results imply that it is of promising
prospect for N-BC practical application for phosphate purification
from waters. The present study provided a new strategy to expand the
application of biochar, usually serving as an adsorbent for cationic
pollutants, to the purification of anionic pollutants such as phosphate
from waters.