Kinetic and Adsorption Behaviour of Aqueous Fe, Cu and Zn Using a 30 nm Hydroxyapatite Based Powder Synthesized via a Combined Ultrasound and Microwave Based Technique

The present study reports the kinetic and absorption performance of novel nanometre scale hydroxyapatite (HAP) absorber synthesised from a combined ultrasound and microwave based technique for the removal of metal ions (Fe, Cu and Zn) from aqueous solutions. After powder characterisation was carried out using XRD, SEM, EDS and FT-IR, batch adsorption studies were carried out. Kinetic studies established that Feand Cu ion adsorption tended to follow a pseudo-second order model, while Zn ion adsorption tended to follow an intra-particle diffusion pattern. All three metal ion adsorption studies indicated an ion-exchange mechanism (metal ion → Ca) was a primary participant in the sorption process and was influenced by intra-particle diffusion. The Isotherm studies indicated the Langmuir isotherm modelled Fe and Cu ion adsorption, while the Freundlich isotherm was the better model for Zn ion adsorption data. Maximum adsorption capacity of HAP determined via Langmuir isotherm was found to be 61.35 mg/g for Cu ions, 55.25 mg/g for Fe ions and 48.54 mg/g for Zn ions. The study established HAP as an effective absorbent material for the removal of Fe, Cu and Zn loaded aqueous solutions.