Adsorption and mechanistic study for humic acid removal by magnetic biochar derived from forestry wastes functionalized with Mg/Al-LDH

Abstract

A novel adsorbent of Mg/Al-LDH functionalized magnetic biochar from waste poplar sawdust (CoFe2O4@PBC-LDH) and bamboo powder (CoFe2O4@BBC-LDH) was developed, and the removal performance of HA from aqueous solution was investigated. The Mg/Al-LDH was effectively functionalized on the CoFe2O4@BC surface via co-precipitation method. The CoFe2O4@BC-LDH exhibited a brush structure with larger surface area and higher adsorption capability. The adsorption mechanism was mainly the ions exchange and electrostatic interactions between CoFe2O4@BC-LDH and HA. The adsorption of HA was well fitted to the Freundlich model with endothermic nature and spontaneous process. CoFe2O4@BC-LDH showed remarkable adsorption capacity for HA, and the maximum adsorption capacity for CoFe2O4@PBC-LDH and CoFe2O4@BBC-LDH were 240.58 and 337.83 mg·g−1 at 25 °C, respectively. The adsorption process was conformed to the pseudo-second-order model and dominated by the chemisorption. Meanwhile, the coexisting ions could conducive to the adsorption capacity of CoFe2O4@BC-LDH for HA. Most importantly, CoFe2O4@BC-LDH exhibited an excellent adsorption capacity in real water samples with long-term stability, and which can be easily recycled from water under an external magnet. Therefore, this work provides new insights into the fabrication of low-cost biochar from forestry wastes and that can be used to develop a high-performance adsorbent for removal of contaminants.