A comparative study of 8-hydroxyquinoline-5-sulphonic acid and its 7-nitro derivative loaded on F-400 granular activated carbon for removal of copper ions from aqueous solutions

The purpose of this study was to compare 8-hydroxyquinoline -5-sulphonic acid (QSA) and its 7-nitro derivative (NQSA) loaded on F-400 GAC as a suitable adsorbent material for adsorption of Cu ions in aqueous solutions. Batch experiments were performed to evaluate effect of various parameters like pH, contact time, temperature, agitation speed, etc. Kinetic studies were done which showed 90.14% removal of copper for QSA and 94.19% removal for NQSA. The adsorption isotherm data were validated to Langmuir, Freundlich and DR isotherms. Kinetic data showed that it follows pseudo second order kinetics for both QSA and NQSA. The thermodynamic parameters of the adsorption process like Gibb's free energy, entropy and enthalpy were also determined for both the ligands. The Langmuir constants have been calculated at different temperatures and the adsorption is found to be exothermic (Δ H = -36.08 kJ/mole for QSA and Δ H = -48.11 kJ/mole for NQSA). Maximum removal is observed at pH 5.5 for both the ligands. It has been observed in the qe values that even though NQSA is adsorbed to a marginally lower extent than QSA, it is able to remove more copper than QSA because of proper orientation to form a 1:2 complex with copper ions on the surface of ligand loaded GAC. The results demonstrates that NQSA loaded GAC has an edge over QSA as an effective adsorbent for removal of copper ions. The 7-nitro derivative owing to its bulky nature shows better adsorption capacity.