Adsorption Characteristics of Glyphosate on Cross-Linked Amino-Starch

Abstract

Cross-linked amino-starch (CAS) was prepared via a dry process and used to adsorb glyphosate from aqueous solution. Effects of adsorption time, glyphosate concentration, temperature, pH, and ionic strength on the adsorption of glyphosate by CAS were thoroughly studied. It shows that CAS can effectively remove glyphosate from the solution. The adsorption equilibrium is attained in about 60 min, and the adsorption process follows the pseudo second-order kinetic model. Sips isotherm model is more suitable than Langmuir and Freundlich isotherm models for the adsorption process, and the maximum adsorption capacity is 3.61 mmol·g –1 from Sips isotherm fitting. The result of thermodynamics study indicates that the adsorption is a spontaneous and exothermic process. The results of isotherm and thermodynamics study show that the adsorption of glyphosate by CAS is attributed to a combination of chemical and physical processes. The adsorption process is severely affected by pH and ionic strength of the solution and the optimal adsorption performance is achieved at pH = 6.0.