The　feasibility　of　the　bioremediation　of　cadmium　(Cd)　using　microalgal-biochar　immobilized　complex　(MBIC)　was　investigated.　Major　operating　parameters　(e.g.,　pH,　biosorbent　dosage,　initial　Cd(II)　concentration　and　microalgal-biochar　ratio)　were　varied　to　compare　the　treatability　of　viable　algae　(Chlorella　sp.),　biochar　and　MBIC.　The　biosorption　isotherms　obtained　by　using　algae　or　biochar　were　found　to　have　satisfactory　Langmuir　predictions,　while　the　best　fitting　adsorption　isotherm　model　for　MBIC　was　the　Sips　model.　The　maximum　Cd(II)　adsorption　capacity　of　MBIC　with　a　Chlorella　sp.:　biochar　ratio　of　2:3　(217.41　mg　g−1)　was　higher　than　that　of　Chlorella　sp.　(169.92　mg　g−1)　or　biochar　(95.82　mg　g−1)　alone.　The　pseudo-second-order　model　fitted　the　biosorption　process　of　MBIC　well　(R2　＞　0.999).　Moreover,　zeta　potential,　SEM　and　FTIR　studies　revealed　that　electrostatic　attraction,　ion　exchange　and　surface　complexation　were　the　main　mechanisms　responsible　for　Cd　removal　when　using　MBIC.　©　2017　Elsevier　Ltd