Synthesis of CuFe2O4/attapulgite composite for removal of methylene blue from aqueous solutions

Attapulgite is a magnesium-aluminosilicate clay mineral with a 2:1 layered chain structure that has excellent adsorption properties. In this work, the CuFe2O4 were loaded on the surface of attapulgite by sol-gel method to prepare magnetic CuFe2O4/attapulgite composite, which was used for the removal of methylene blue. The magnetic attapulgite was characterized by XRD, FT-IR, SEM-EDS/Map, XPS, BET, and VSM, which confirmed that the CuFe2O4 was successfully loaded on the surface of attapulgite, with good magnetic performance. Under the optimal operating conditions, the magnetic attapulgite efficiently removed methylene blue from dye solution, in which the removal rate of methylene blue was 97.76 %. The kinetic analysis showed that chemisorption significantly impacted the adsorption rate of methylene blue by magnetic attapulgite, and the process was limited by both liquid film diffusion and intra-particle diffusion. The adsorption followed the Langmuir isotherm model, suggesting that methylene blue adsorbed to the surface of magnetic attapulgite in a near-monolayer fashion. Thermodynamic analysis revealed a negative Gibbs free energy and a standard entropy of 0.0683 kJ/ (mol & sdot;K), indicating that the adsorption was spontaneous, endothermic, and driven by entropy. Meanwhile, the solution still maintained more than 90 % removal rate of methylene blue, after three cycles under the optimal conditions.