Removal of a reactive textile azo dye by dolomitic solids: kinetic, equilibrium, thermodynamic, and FTIR studies

Abstract

Algerian dolomite was treated at different temperatures in the 600–1000°C range and characterized by XRD and SEM. The obtained samples, named dolomitic solids, were used in the removal of Reactive Black 5 (RB5) from aqueous solutions. A literature survey shows that the data about the dye adsorption by dolomites are almost non-existent. Kinetic data, equilibrium isotherms, thermodynamic parameters, pH influence, and FTIR study were considered. The kinetic mechanism is enough complex, involving different models such as those of pseudo-second-order, intraparticle diffusion, and Elovich. For all dolomitic solids, the capacity in RB5, at equilibrium, strongly increases with increasing adsorption temperature. The affinity sequence is D900 (dolomite treated at 900°C) > D800 > D1000 > D600 > raw dolomite. Knowing that D900 adsorbs 125.9 mg g⁻¹, it appears very effective for removing reactive dyes from wastewaters. The isotherms are found to be overall well represented by the Redlich–Peterson equation. The fact that maximum adsorption occurs at isoelectric point emphasizes the prevalence of the nonelectrostatic interaction. A close agreement exists between the evolution of kinetic, equilibrium, and thermodynamic parameters, suggesting chemisorption. The process reflects for D800, D900, and D1000 a weak chemical interaction via a mechanism of inner-sphere complexation. The comprehension of the organic compound–dolomitic solid interactions constitutes a fundamental aspect for developing the application of these materials in the field of wastewater treatment.

Keywords:

• Dolomite
• Reactive Black 5
• Removal
• Kinetics
• Isotherms
• Mechanism