Enhanced and efficient removal of U(VI) from aqueous solution by a hydroxyapatite-bamboo biochar composite: performance and mechanism

A hydroxyapatite-bamboo biochar (HAP-BBC) composite was synthesized via pyrolysis and co-precipitation for efficient U(VI) removal from aqueous solution. Batch experiments demonstrated that over 98% removal efficiency for 50 mg L −1 U(VI) was achieved at pH 4.0–5.0 with an adsorbent dosage of 0.3 g L −1 . The adsorption process fitted well with the Langmuir isotherm and pseudo-second-order kinetic model, with a theoretical maximum adsorption capacity of 649.35 mg g −1 . U(VI) immobilization follows synergistic mechanisms of dissolution–precipitation, surface complexation and ion exchange, endowing the composite with promising prospects for uranium-containing wastewater treatment.