Removal of phosphate by green zeolite - peanut shell biochar: Performance, mechanism

The development of efficient adsorbent materials is a key challenge in environmental pollution control, but the existing materials have limitations in terms of performance and green preparation. In this study, zeolite - biochar (Ze-BC) composite adsorbent was innovatively prepared by green mechanical ball milling, and the synthesis method was optimized in terms of rotational speed, time, mass ratio, and ball material ratio. Comprehensive characterization (scanning electron microscopy, specific surface area analysis, and adsorption test) showed that the adsorption performance was optimal under acidic conditions. The adsorption capacity reached a maximum value of 10.095 mg/g at the optimum dosage (20 g/L). The adsorption kinetics conformed to the pseudo-second-order model, indicating that the adsorption process was dominated by chemisorption and supplemented by physisorption. Density functional theory (DFT) calculations confirmed that Ze-BC has a high adsorption energy for phosphate ions (H
2
PO
4
-
/HPO
4
2-
) and so on. It features a specific surface area of 404.3481 m
2
·g
-1
, maintains >60% removal efficiency after 5 adsorption-desorption cycles, resists interference from Cl
-
/NO
3
-
/CO
3
2-
/SO
4
2-
, and fits the pseudo-second-order kinetic model with R
2
=0.9844. The adsorption was spontaneous, selective, and stable. This study provides efficient and green adsorption materials for environmental pollution control and new ideas for the design of high-performance composite adsorbents.