Removal of methylene blue from aqueous solution by adsorption onto hydroxyapatite nanoparticles

Abstract

Water pollution due to industrial discharges is a major problem in many countries as it can have adverse effects on the environment and human health. Among wastewater treatment processes, adsorption technique is widely used to reduce the harmful effects of many pollutants, including dyes. The main objective of this research is to characterize and evaluate the removal capacity of methylene blue (a cationic dye) from an aqueous solution using hydroxyapatite as a bio-adsorbent. Hydroxyapatite was prepared by two different methods and the resulting biomaterials were designated HAp A, HAp B, HAp C, and HAp D. A comparative study of methylene blue adsorption by these biomaterials was performed. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to characterize these adsorbents. The effects of various experimental parameters such as contact time (5–120 min), concentration (5–90 mg/L), pH (6–12) and temperature (25–6°C) were studied. Adsorption studies revealed a removal efficiency of 88.88% at an initial MB concentration of 45 mg/L, an equilibrium time of 20 min, Basic pH and a temperature of 25 °C. The pseudo-second order kinetic model was used to describe the adsorption kinetics, while the Freundlich adsorption isotherm was used to describe the equilibrium adsorption process. This research suggests that the method of synthesis has a significant impact on the ability of the adsorbent to remove organic pollutants from dyes in an aqueous solution.