Design and optimization of an adsorption method for the removal of textile azo dyes from aqueous solutions using Plantago lanceolata

Abstract

Water is an essential commodity for human survival; however, this resource is predicted to be scarce within the 21st Century due to pollution and industrialization. Textile industries are among the many polluters of water, and hence methods to remediate textile waste-water need attention. In this study, a common garden weed Plantago Lanceolata was used for the preparation of novel activated carbon materials as an adsorbent for the degradation of textile azo dyes Reactive Blue 222 (RB), Reactive Red 195 (RR), and Reactive Yellow 145 (RY). The activated carbon was modified with four different chemical activators to produce phosphoric acid-based activated carbon (H3PQ4-AC), sulfuric acid-based activated carbon (H2SO4-AC), potassium hydroxide-based activated carbon (KOH-AC), and sodium hydroxide-based activated carbon (NaOH-AC). These materials were characterized by Fourier- transfer infrared spectroscopy (FTIR), scanning electron microscope with energy dispersive Xray (SEM/EDX), high resolution transmitting electron microscope (HRTEM), and a thermogravimetric analyzer with differential scanning calorimeter (TGA/DSC). The initial concentration of the adsorbate, adsorbent dosage concentration, contact time, temperature, and pH were optimized. The four materials adsorption capacity was studied, and H3PQ4-AC produced the best results of adsorption capacity 98,98% - 100%, with optimum agitation time of 70 minutes, the optimum dosage of 0.8 g/60 ml of adsorbent, and pH of 6. The experimental data were fitted using Langmuir (type 1- 4), Freundlich, Temkin, and Dubinin-Radushkevich isotherms. The data from this study best fitted the Langmuir isotherm type 1: RB (qm -15.58 mg g 1 ), RR (qm - 11.24 mg g 1 ) and RY (qm - 11.24 mg g 1 ). Furthermore, the reaction rate followed the pseudosecond-order kinetic model while the intraparticle diffusion model had no impact. Its thermodynamic parameters indicated the reaction as spontaneous and exothermic. Furthermore, a nanocomposite was prepared from H3PQ4-AC and iron oxide to produce an iron oxide/activated carbon nanocomposite. FTIR, SEM/EDX, HRTEM, and TGA/DSC fully characterized this novel material. The iron oxide/H3PQ4-AC nanocomposite produced slightly better results compared to H3PO4-AC: RB (99.60% - 100%), RR (99.59 - 100%) and RY (99.48% - 100%). The experimental data fitted Langmuir isotherm type 1, and the reaction followed the pseudo-second-order kinetic reaction model.