One-step synthesized calcium phosphate-based material for the removal of alizarin S dye from aqueous solutions: isothermal, kinetics, and thermodynamics studies

Abideen Idowu Adeogun,Ramesh Balakrishnan Babu

doi:10.1007/s13204-015-0484-9

Abstract

Calcium phosphate hydroxyapatite (Ca-Hap) synthesized from CaCO3 and H3PO5, it was characterized by scanning electron microscopy, Fourier transform infrared, and X-ray diffraction. The Ca-Hap was used for the removal of Alizarin Red S dye from its aqueous solution. The kinetics, equilibrium, and thermodynamic of the adsorption of the dye onto the Ca-Hap were investigated. The effects of contact time, initial dye concentration, pH as well as temperature on adsorption capacity of Ca-Hap were studied. Experimental data were analyzed using six model equations: Langmuir, Freudlinch, Redlich–Peterson, Temkin, Dubinin–Radushkevich, and Sips isotherms and it was found that the data fitted well with Sips and Dubinin–Radushkevich isotherm models. Pseudo-first-order, pseudo-second-order, Elovic, and Avrami kinetic models were used to test the experimental data in order to elucidate the kinetic adsorption process and it was found that pseudo-second-order model best fit the data. The calculated thermodynamics parameters (∆G°, ∆H° and ∆S°) indicated that the process is spontaneous and endothermic in nature.

Highlights

Environmental contaminations by toxic wastes pose a serious problem worldwide due to their incremental accumulation in the food chain and continued persistence in the ecosystem
Calcium phosphate hydroxyapatite (Ca-Hap) synthesized from CaCO3 and H3PO5, it was characterized by scanning electron microscopy, Fourier transform infrared, and X-ray diffraction
The Ca-Hap was used for the removal of Alizarin Red S dye from its aqueous solution

Summary

Introduction

Environmental contaminations by toxic wastes pose a serious problem worldwide due to their incremental accumulation in the food chain and continued persistence in the ecosystem. The residual dyes from different sources such as: textile, paper and pulp, dye and dye intermediates, pharmaceutical, tannery, and kraft bleaching industries are considered as organic colored pollutants (Rajgopalan 1995; Routh 1998; Kolpin et al 1999; Ali and Sreekrishnan 2001). These industries utilize large quantities of a number of dyes which residues lead to large amount of colored wastewaters, toxic and even carcinogenic, posing serious hazard to aquatic living organisms. Most treatments for such dye-laden effluents are largely inadequate; removal of this dye from industrial wastewaters is a crucial process, from both economic and environmental points of view (Panizza et al 2001)

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Conclusion