Adsorption of AuCl (4) (-) from Acidic Chloride Solution by Chemically Modified Lignin Based on Rice Straw

The chemically modified lignin was synthesized based on rice straw and the adsorption properties of AuCl (4) (-) were investigated in this paper. The adsorbent was characterized by Fourier transform infrared spectrometer, scanning electronic microscope and thermogravimetric analysis and differential scanning calorimetry. The chemically modified rice straw lignin was of excellent thermal stability and had plenty of primary amines and hydroxyls. Many influence factors such as initial concentration of AuCl (4) (-) , adsorption time and concentration of hydrochloric acid on AuCl (4) (-) were optimized. The maximum adsorption capacity was 783.94 mg center dot g(-1). The equilibrium adsorption time was 600 min. The equilibrium isotherm fitted well with the Langmuir model and the pseudo-second-order kinetic model was suitable for describing the adsorption of AuCl (4) (-) . Low hydrochloric acid concentration could promote the selectivity of adsorption on AuCl (4) (-) . Combination of ion exchange and reduction was the mechanism. AuCl (4) (-) was adsorbed by ion exchange first and then reduced from hydrochloric acid medium in the form of Au(0) by phenolic hydroxyl.