Methylene blue adsorption from an aqueous solution by a magnetic graphene oxide/humic acid composite

Abstract

A novel adsorbent called magnetic humic acid/graphene oxide composite (MHAGO) adsorbent was prepared for treating methylene blue (MB) from wastewater. The structure and morphology of MHAGO were characterized by FTIR, XRD, SEM and XPS. The response surface method was used to optimize the quality feeding ratio for the raw materials, and the best graphene oxide: humic acid: ferroferric oxide feeding ratio was determined to be 0.25:0.50:1.66. Batch adsorption experiments were performed with variation in the initial MB dye concentration, pH of the solution, adsorbent dosage and contact time. The results showed that the adsorption reaction occurred at 45 °C with 30 mg adsorbent to adsorb 5.0 mg/L MB in 100 mL solution, with a maximum MB adsorption capacity of approximately 59.00 mg/g for MHAGO. The adsorption kinetics and adsorption isotherms were found to be in accordance with the Elovich equation and Langmuir model, respectively. Moreover, the thermodynamic parameters showed that the adsorption is spontaneously endothermic. The mechanisms for MB adsorption onto the MHAGO surface was mainly electrostatic attraction, π-π interaction and hydrogen bonding. In addition, the MHAGO shows good feasibility for the removal of pollutants from real factory dyeing wastewater.