Neem flower (Azadirachta indica) activated with sintered-CaP for enhanced adsorption of malachite green dye—adsorption, kinetic, and thermodynamic studies

The adsorption of malachite green (cationic dye) is generally poor due to its bulk structure. For the first time, the bioadsorbent of neem flower ( Azadirachta indica ) was activated with sintered calcium phosphate (S-CaP) towards the removal of malachite green (MG) dye. The activated neem flower (NF) was characterized using XRD, SEM, FTIR, and BET analytical techniques. The NF activated with S-CaP (NFS2) exhibited the highest surface area of 10.9 m 2 /g among the prepared bioadsorbents. The physical interaction of alumina, boric acid, and S-CaP with NF was affirmed by the presence of new a hump at 730 cm −−1 in the FTIR spectra. The adsorption studies with different initial concentrations of MG dye were carried out to investigate the adsorption potential of the prepared NF-based bioadsorbents. The adsorption data were analyzed using Langmuir and Freundlich isotherms, which revealed strong adsorption of the MG dye over activated NF. The thermodynamic parameters (ΔG * = −84.51kJ; ΔH * = −82.1kJ; ΔS * = 26.5J) were calculated by carrying out adsorption at different temperatures.