Removal of hexavalent chromium by ecofriendly raw marine green alga Ulva fasciata: Kinetic, thermodynamic and isotherm studies

Abstract

The present study investigates the efficiency of marine green macroalga Ulva fasciata to remove Cr(VI) from aqueous solutions. The alga was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-rays (EDAX) and BET analyses. The effects of various operating parameters such as pH (1–9), biosorbent dose (0.05–0.25 g), initial concentration (10–200 mg/l) and temperature (30–50 °C) were also examined. At concentrations of 10 and 20 mg/l, it was observed that Cr(VI) was completely removed from the solutions after only 5 min contact time. The adsorption experiment data fully showed the applicability of the Harkins-Jura isotherm model. Amongst the applied kinetic models, pseudo-second-order kinetic model was the best fitted one. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) revealed the feasibility of spontaneous random exothermic adsorption. The results indicated the high removal efficiency of Cr(VI) from its aqueous solutions by the raw alga Ulva fasciata because of its low-cost, ecofriendly and promising biosorbent quality.