Selective adsorption and recovery of scandium from red mud leachate by using phosphoric acid pre-treated pitaya peel biochar

•A low-cost and environment-friendly biosorbent for scandium was prepared.•Scandium was successfully recovered from red mud leachates.•The used biochar could recover Sc3+ ion with high selectivity from Al3+, Fe3+, Dy3+, Y3+ ions coexistence solution.•The used biochar showed ideal reusability after five adsorption/ desorption cycles.•The adsorption mechanism of 750 °C calcined H3PO4 activated biochar was identified through characterization analysis.