A Multipurpose Lignin-based Adsorbent for Metallic Ions, Nanoparticles and Various Organophosphate Pesticides in Hexane

A lignin-based adsorbent for metallic ions, nanoparticles and various agricultural organophosphate pesticides in hexane is immobilized on silica gel without further fractional purification. For most organophosphate analytes examined in this study under the same conditions, the percentage of adsorption achieved was well above 90% in 15 min, was found to be highly related to the dipole-dipole attractions that occurred among the oxygen-containing functional groups attached to analyte and lignin molecules and was greatly enhanced in hexane. The adsorption is believed to be reversible and surface oriented; furthermore, the interaction leading to the adsorption is not as significantly subject to the steric hindrance effect caused by the bulky group or elements surrounding the phosphorus element. Other types of interactions enhanced in hexane, such as the pi-pi interaction, and hydrogen bonding in some cases, were also observed and contributed less to the percentage of adsorption. However, the adsorption of ions and nanoparticles under aqueous conditions is thought to be mainly a result of the complexation of the oxygen-bearing hydrophobic cleft of the lignin molecule. In all cases, the nature of the analyte, the amount of adsorbent and the acidic or basic origin of the additive in matrix also affect the percentage of adsorption.