Preparation of biochar grafted with amino-riched dendrimer by carbonization, magnetization and functional modification for enhanced copper removal

•MBC@APTES-PAMAM exhibited higher adsorption capacity for the removal of Cu(II).•The maximum Cu(II) adsorption capacity of MBC@APTES-PAMAM was 251.81 mg/g.•External impact factors such as pH, competing ions, surfactant and humic acid greatly influenced Cu(II) adsorption process.•The adsorption mechanism of MBC@APTES-PAMAM for Cu(II) was elucidated.