Efficient and environmentally friendly removal of azo textile dye using a low-cost adsorbent: Kinetic and reuse studies with application to textile effluent

Abstract

Recently, there has been an increasing interest in environmentally friendly methods for the removal of toxic dyes to enable sustainable textile dyeing processes. In this study, a highly efficient, non-toxic, low-cost MgO particles were prepared by sol-gel technique and utilized for the removal of Reactive Red 21 azo dye by adsorption process. The prepared MgO particles were characterized by Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, X-Ray Diffraction, and Particle Size Analysis. The batch adsorption studies were performed for optimizing the parameters affecting adsorption. The adsorption behavior of Reactive Red 21 was accurately characterized by the Langmuir model. The adsorption process was found to be thermodynamically spontaneous at room temperatures as indicated by the negative Gibbs free energy change (∆G) value of −30.65 kj/mol. The kinetic studies indicate that the pseudo-second-order model provides a good fit to the adsorption of Reactive Red 21. The adsorption capacity of the prepared MgO particles for Reactive Red 21 was determined to be 355 mg/g at room temperature over a wide pH range of 5–9, with a contact time of 20 min. The regeneration of dye-adsorbed MgO particles was conducted at 500 °C for 2 h. The regenerated MgO particles were then utilized for adsorbing Reactive Red 21 five times with a sufficiently high dye removal efficiency. The prepared MgO particles provided a 98 % dye removal in real textile wastewater containing Reactive Red 21 dye.