Efficient adsorptive removal of Zinc by green marine macro alga Caulerpa scalpelliformis –Characterization, Optimization, Modeling, Isotherm, Kinetic, Thermodynamic, Desorption and Regeneration Studies

Abstract

In this work, the sorption efficiency of marine green macro algae, Caulerpa scalpelliformis was explored for heavy metal zinc from aqueous and industrial wastewater. The characteristics of sorbent prepared were studied using Fourier Transform Infrared Spectroscopy (FTIR), Scanning electron microscope (SEM), and Brunauer–Emmett–Teller (BET). The optimum conditions of operating variables were found using Box-Behnken design (BBD) as pH - 5.7, sorbent dosage - 1.5 g/L and agitation speed - 150 rpm. At these conditions, experiments were performed for the effect of zinc concentrations and temperature. The equilibrium studies were performed using Langmuir, Freundlich and Temkin isotherm. Results show that the Langmuir isotherm model fits the data well based on high R2 = 0.9970. The maximum uptake of zinc by the Langmuir model was 83.3 mg/g. The kinetic studies show that the mechanism of sorption of zinc on green biomass Caulerpa scalpelliformis follows pseudo-second order (R2 = 0.9960). From the thermodynamic study, it was observed that the sorption of zinc on green biomass was feasible, spontaneous and endothermic. Desorption and regeneration studies were also performed for five cycles.