Phosphate-functionalized magnetic calcium alginate for the engineering remediation of uranium-contaminated water and soil

•A magnetic phosphate-functionalized calcium alginate (MPCA) was synthesized.•The mechanical strength improved after in situ magnetization and phosphorylation.•The adsorption process involves multiple adsorption mechanisms.•The excellent magnetic separation of U(VI) from eluent and soil.•An effectiveness in the engineering linked remediation of uranium contaminated soil.