Preparation of leonardite powder-embedded calcium alginate beads and adsorption of Safranin-O dye

Abstract

In this study, calcium alginate (Ca-Alg) beads were mixed with leonardite powder to prepare leonardite-embedded calcium alginate (Leo-Ca-Alg) beads. The prepared Leo-Ca-Alg beads were utilized for the adsorption of the Safranin-O dye. Leo-Ca-Alg beads were characterized by X-ray diffraction, Fourier transform infrared, and scanning electron microscopy before and after the adsorption process. The effects of pH, adsorbent dose, initial dye concentration, and contact time on the adsorption of Safranin-O dye onto Leo-Ca-Alg beads were investigated. The optimal condition was achieved at a pH value of 8.0, an adsorbent amount of 20 g/L, an initial concentration of 10 mg/L, and a contact time of 120 min. Under optimum conditions, 98.91% dye removal efficiency was obtained. Besides, the isotherm, kinetic, and thermodynamic were studied for the adsorption process. Accordingly, the removal of Safranin-O dye by the Leo-Ca-Alg adsorbent can be defined by the Freundlich model and described by the Elovich model and the second-order kinetic model at concentrations of 10 and 20–30 mg/L, respectively. The Safranin-O removal by Leo-Ca-Alg was feasible and naturally spontaneous. In reuse cycle studies, it was tried up to 10 reuses and decreased from 98.91 to 83.01% in the 10th use. HIGHLIGHTS A novel leonardite-embedded calcium alginate beads adsorbent was prepared.; Safranin-O was removed using the prepared adsorbent with an efficiency of 98.91%.; The Safranin-O removal by leonardite-embedded calcium alginate was feasible and naturally spontaneous.; The adsorbent was successfully utilized for 10 cycles.;

Keywords

• adsorption
• calcium alginate beads
• leonardite powder
• safranin-o dye