Tween 80 Modified Hydroxyapatite as an Adsorbent for Removal of Copper from Aqueous Solution

Hydroxyapatite was in this study modified with Tween 80 through ultrasound assisted chemical precipitation method. The Tween-modified hydroxyapatite (T-HA) was characterized by some analytical methods. T-HA particles were rod-shaped with an average length of 59 nm. The effect of contact time, pH, temperature, adsorbent dosage and initial concentration of Cu2+ on adsorption capacity were studied to determine the capacity of T-HA to adsorb copper ions. The removal efficiency for Cu2+ reached maximum (82.68%), at an initial concentration of Cu2+ of 200 mg/L and adsorbent dosage of 0.1 g at 35 degrees C for two hours reaction. The adsorption mechanism was determined by pseudo-first-order (PFO) and pseudo-second-order (PSO) kinetic models, while the equilibrium isotherms was fitted by Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models. Our data can best be described by a PSO kinetic model (R-2 = 0.99971) and D-R model (R-2 = 0.9377), suggesting a chemisorption mechanism. Application of Langmuir isotherm model (R-2 = 0.99337) indicated that Cu2+ was adsorbed on T-HA as a monolayer. These results demonstrated that the Tween-modified hydroxyapatite is a promising material for environmental remediation of copper ions in waste water.