Valorization of N-doped biochar into Fe-Cu loaded carbon catalyst from electroplating wastewater: Structure regulation, adsorption performance, and catalytic properties

A nitrogen-doped and CaO-activated pinewood biochar ( N -aPBC) was synthesized. • Closed-loop recycling strategy enables electroplating wastewater treatment. • N -aPBC achieves high Fe 3 ⁺/Cu2⁺ adsorption capacities of 287.40/61.88 mg g⁻1. • N/O functionalities and defects promote Fe 3 ⁺/Cu2⁺ uptake via surface interactions. • Spent adsorbent-derived Fe-Cu-NaB removes 93.64% CIP from swine effluent. The efficient removal and resource recovery of high-concentration heavy metals like Fe 3 ⁺ and Cu 2 ⁺ from electroplating wastewater remains a critical challenge. Herein, a sustainable closed-loop “adsorption-transformation-upcycling” strategy was proposed. Initially, a nitrogen-doped and CaO-activated pinewood biochar ( N -aPBC) was synthesized via synergistic modification. Systematic characterization revealed that N -aPBC features a high specific surface area (188.79 m 2 g⁻ 1 ), a hierarchical porous architecture, and abundant nitrogen-containing functionalities. Adsorption experiments demonstrated superior performance for Fe 3 ⁺ and Cu 2 ⁺, yielding maximum capacities of 287.40 and 61.88 mg g⁻ 1 , respectively. Mechanistic investigations indicated that the adsorption followed the pseudo-second-order kinetic model and Langmuir isotherm, suggesting monolayer chemisorption. The primary removal mechanisms involved surface complexation via N/O-functional groups, coupled with electrostatic attraction and ion exchange. N species and defects tuned surface polarity and electronic structure. Subsequently, the spent adsorbent was calcined to produce a functional material (Fe-Cu-NaB). Electrochemical analyses confirmed that Fe-Cu-NaB exhibited lower charge transfer resistance and enhanced electrocatalytic activity. Notably, Fe-Cu-NaB enhanced the oxidative degradation capacity, achieving high removal rates of 93.64% for ciprofloxacin (CIP) and 65.88% for total organic carbon (TOC) in swine wastewater. This work provides a high-performance adsorbent for heavy metal remediation and establishes a viable pathway for the high-value reutilization of spent adsorbents as efficient catalytic materials. Download: Download high-res image (142KB) Download: Download full-size image