Remediation performance and mechanisms of Cu and Cd contaminated water and soil using Mn/Al-layered double oxide-loaded biochar

•LDO/BC was successfully prepared via coprecipitation and co-pyrolysis.•LDO/BC had an outstanding performance for Cu2+ and Cd2+ adsorption.•Ca was beneficial to the formation of more regular layered and flake structure.•LDO/BC exhibited an excellent remediation for heavy metals in contaminated soil.