One-pot hydrothermal synthesis of magnetic N-doped sludge biochar for efficient removal of tetracycline from various environmental waters

•Magnetic N-doped sludge biochar was synthesized by one-pot hydrothermal method.•MNSBC performed excellent adsorption capacity for TC in various real water samples.•MNSBC showed a good environmental safety due to the low leaching levels of Fe and TN.•MNSBC exhibited a stable sustainable adsorption capacity by NaOH regeneration.