Application of a magnetic graphene nanocomposite modified with 5-aminoisophthalic acid amine group for chromium (VI) adsorption from aqueous solutions: kinetic and thermodynamic studies

Polymer nanocomposites are composite materials that incorporate nanomaterials, such as magnetic graphene oxide (mGO), into a polymer matrix. To enhance its adsorption capacity, the surface of mGO nanoparticles was polymerised by a 5-aminoisophthalic acid amine group (mGO-AIPA) through a simplified co-precipitation method. The structural and morphological characteristics of the synthesised nanoparticles were evaluated through techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Thermogravimetric analysis (TGA), and Vibrating sample magnetometer (VSM). Response surface method (RSM) was used to evaluate the effectiveness of mGO-AIPA nanocomposite in removing chromium (VI) ions by examining variables such as solution of pH, contact time, adsorbent dose and initial concentration. Also, the study of kinetic models, adsorption isotherms and thermodynamic modelling of the process were evaluated. The results found that the mGO-AIPA nanocomposite has the maximum removal of chromium (VI) ions from the aqueous solution by 83.11% in optimal conditions including pH 3.5, contact time of 35 min, an adsorbent dosage of 25 mg g-1 and an initial concentration of 55 mg L-1. The pseudo-second-order kinetic and Langmuir isotherm models had a better fit with the experimental data of adsorption and the maximum adsorption capacity of chromium (VI) the base of the Langmuir model was 90.91 mg g-1. Moreover, the thermodynamic analysis indicated that the process was exothermic and nonspontaneous process, implying that it was energetically unfavourable. These findings suggest that the mGO-AIPA nanocomposite has a high performance as an effectual adsorbent to eliminate chromium heavy metal from an aqueous medium.