Hydroxyapatite nanowires enhanced biochar hybrid aerogel for superior Ni(II) adsorption

Industrial nickel pollution discharged into water bodies poses a serious threat to the environment and human health. Conventional biochar-based adsorbents suffer from poor mechanical strength, restricting large-scale application. Inspired by reinforced concrete, this study synthesized a high-strength hydroxyapatite nanowire (HANW) enhanced biochar hybrid aerogel (HBA). HANWs served as the reinforcing framework, while the MgCl 2 -modified biochar matrix provided abundant adsorption sites, synergistically boosting mechanical strength and adsorption capacity. The optimized HBA exhibited 47% higher compressive strength than conventional biochar aerogels and a notable Ni(II) adsorption capacity of 300.65 mg/g, which is 4 times more effective than conventional biochar. Comprehensive characterization confirmed Ni(II) adsorption on HBA follows a synergistic physicochemical process involving ion exchange, surface complexation, surface sedimentation, electrostatic interaction, and pore diffusion. The HANW-reinforced porous architecture not only sustains this multi-mechanistic pathway but also preserves high mass-transfer efficiency and structural stability during successive adsorption cycles. HBA further exhibited strong selectivity toward Ni(II) under competitive conditions, achieving 99.7% simultaneous removal of Ni in actual electroplating wastewater. The reinforced-concrete-like architecture offers new insights for the design of durable, recyclable, and scalable materials for heavy-metal-contaminated wastewater remediation. Download: Download high-res image (414KB) Download: Download full-size image