Novel environmental-friendly nano-composite magnetic attapulgite functionalized by chitosan and EDTA for cadmium (II) removal

Abstract Adsorbent preparation of non-toxicity, low cost, large adsorption capacity and outstanding reusability is imperative in purifying Cd-contaminated water. In this work, novel environmental friendly shell-coated magnetic attapulgite, named as attapulgite/CoFe2O4@SiO2-chitosan/EDTA (ATPCFS-CSEs), was successfully prepared by solvothermal and sol-gel process. Chitosan and EDTA were selected to functionalize the magnetic attapulgite to provide abundant amino groups and carboxyl groups. Sodium tripolyphosphate was chosen as non-toxic cross-linker in surface deposition-crosslinking, and subsequently amidation reaction was taken for functionalization by chitosan and EDTA. The adsorbents were characterized by SEM, TEM, XRD, FTIR, VSM, BET and XPS, and the adsorption properties including adsorption isotherm, contact time, adsorbents dosage, pH value of initial solution, competitive ions, desorption experiment and recycling method for repeated use were evaluated. The nano-composite adsorbent exhibited well-defined architecture and paramagnetic behavior. The adsorption behavior agreed well with Langmuir model, and adsorption capacity was up to 127.79 mg/g. High concentration ionic competition experiments showed that the ATPCFS-CSEs has high selectivity. Removal efficiency was still above 88% after 5 cycles. The adsorption mechanism was also discussed. Functional groups complexed with cadmium ions with the formation of stable complexes. ATPCFS-CSEs is an excellent adsorbent for removal and separation of Cd2+ from contaminated water.