Physico-chemical, structural, and adsorption properties of amino-modified starch derivatives for the removal of (in)organic pollutants from aqueous solutions

Abstract

In this study, an environmentally sustainable process of crystal violet, congo red, methylene blue, brilliant green, Pb2+, Cd2+, and Zn2+ ions adsorption from aqueous solutions onto aminomodified starch derivatives was investigated. The degree of substitution, elemental analysis, swelling capacity, solubility, and FTIR, XRD, and SEM techniques were used to characterize the adsorbents. The influence of pH, contact time, temperature, and initial concentration has been studied to optimize the adsorption conditions. The amino-modified starch was the most effective in removing crystal violet (CV) (65.31-80.46%) and Pb2+ (67.44-80.33%) within the optimal adsorption conditions (pH 5, 10 mg dm-3, 25 oC, 180 min). The adsorption of CV could be described by both Langmuir and Freundlich adsorption isotherms, while the adsorption of Pb2+ ions was better described by the Langmuir isotherm. The pseudo-second order model can be used to describe the adsorption kinetics of CV and Pb2+ on all tested samples. The thermodynamic study indicated that the adsorption of CV was exothermic, while the Pb2+ adsorption was endothermic. The simultaneous removal of CV and Pb2+ from the binary mixture has shown their competitive behavior. Thus, the amino-modified starch is a promising eco-friendly adsorbent for the removal of dyes and heavy metals from polluted water.