Buoyant ALG/HA/HGMs composite adsorbents for highly efficient removal of copper from aqueous solution and contaminated kaolin soil

•Two novel buoyant ALG/HA/HGMs composite adsorbents were prepared and characterized.•The buoyant adsorbents could efficiently remove copper from aqueous solution and kaolin.•The buoyant adsorbent of AHG(acid) could reduce pH value of kaolin soil.•The buoyant adsorbent of AHG(base) could increase pH value of kaolin soil.•AHG(acid) showed excellent reusability in removal of copper from contaminated kaolin.