High Performance Removal of Azo and Cationic Dyes Pollutants with Mn-Aluminophosphate Particles: Kinetics, Thermodynamics, and Adsorption Equilibrium Studies

Abstract

Manganese aluminophosphate (Mn–APO) microcrystals have been synthesized by hydrothermal method and characterized with X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). As a potential application in water treatment, Mn–APO particles were evaluated in removal of safranin (CAF) and chrysoidine G (CHG) dyes from aqueous solution. The effects of initial concentrations and pH, contact time, dosage of adsorbent, and temperature were investigated on the dye adsorption capacity of the Mn–APO. The experimental data revealed that an amount of 0.1 g of sorbent demonstrated maximum removal efficiency of CAF and CHG dyes (30 ppm) at pH 7. Two common kinetic models, pseudo-first-order and pseudo-second-order were applied to explain the adsorption kinetics. The adsorption kinetics of CHG and SAF was found to follow a pseudo-second-order kinetic model. Thermodynamic results indicated that the adsorption of CHG and SAF onto Mn–APO particles is endothermic and negative value of ΔG° confirms the spontaneous process. The particles of Mn–APO can be easily regenerated by chemical and physical methods after adsorption. Three common isotherm models, the Langmuir, Temkin and Freundlich were employed to study the interaction of CHG and SAF onto Mn–APO particles. The equilibrium adsorption of Mn–APO was best explained by the Temkin isotherm model. The recycled sorbent can be use after 3 cycles without noticeable change in its activity. The obtained maximum adsorption capacities correspond to an excellent ability to remove dye at ambient temperature. The present study not only introduces new materials for highly efficient and recyclable sorbent, but also facilitates their practical application in environmental remediation.