Synthesis and Characterization of Hydroxyapatite- (HAP-) Clay Composites and Adsorption Studies on Methylene Blue for Water Treatment
Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Hindawi
Abstract
Dyes used by the textile, tannery, and food industries tend to pollute water bodies and must be removed to get clean water.
Hydroxyapatite (HAP) was synthesized from eggshells using the wet precipitation process. 'e as-synthesized HAP was
characterized using Fourier Transform Infrared (FTIR) and X-ray powder diffraction (XRD). 'e synthesized HAP was mixed
with three different clays: halloysite (HNT), kaolinite (KAO), and bentonite (BENT). 'e removal efficiency values of methylene
blue (MB) from the data showed that HAP-BENT adsorbents had higher values, followed by HAP-HNT and then HAP-KAO
adsorbents. 'e combined masses of 24 mg, 34.5 mg, and 33 mg (representing 20%, 15%, and 10% of HAP-BENT mass) had
average adsorption capacity values of 20.7 mg/g, 17.2 mg/g, and 17.9 mg/g, respectively. For each mass percentage, the adsorption
capacity values were found to decrease with adsorbent dosage. 'e HAP-BENT composites had removal efficiency values of 98.4,
91.9%, and 91.9%, respectively. Adsorption data for the HAP-BENT adsorbents were found to be well described by the Langmuir
isotherm model and pseudo-second-order kinetic model. 'e effect of temperature on adsorption capacity was evaluated and
thermodynamical modeling was undertaken. 'e thermodynamical modeling predicts that based on the value of the change in
enthalpy and Gibbs free energy the process was exothermic and spontaneous. 'is work confirms the potential of HAP-clay
composites in removing MB from water.
Description
Research Article