Preparation of cellulose nanofiber/Fe₃O₄/CaCO₃ magnetic biocomposite by air capture and its application on purifying lead-contaminated water: Removal, immobilization and separation

Utilizing nature resource is one of the most effective ways to achieve sustainability development. In this work, super low-concentration CO2 in the atmosphere and rich and cheap biomaterial cellulose were used to prepare magnetic bio-composite, cellulose nanofiber/Fe3O4/CaCO3 (CFeCa). By capturing CO2 in air, Ca2+ was trans-formed into calcite CaCO3, which subsequently coated on cellulose nanofiber (CNF). Fe3O4 with about 50 nm in size were also observed to attach to the CNF. Thus, CNF bridged these two inorganic materials, which together fabricated stable composite with strong mutual coupling. The prepared CFeCa was applied to purify the lead-polluted water as water treatment agent. Its up-taken capacity for Pb2+ reached as high as 1010 mg(-1). Almost 100% removal efficiency was attained, even treating Pb2+ wastewater in a wide concentration range from 5 to 250 ppm. Meanwhile, CFeCa is stable property during application. After running for 30 cycles, the treated water still met drinkable water standard. More importantly, the recovered lead was also bound on the surface of CNF, which make it easy to be separated from water and avoiding the risk of second pollution. Cheap raw materials and multiple merits of resulted composite offer CFeCa a perspective application as water treatment agent.