In order to extract palladium economically

efficiently and environment friendly

lignin is firstly extracted from rice straw by sulfuric acid method

and then the quaternary ammonium rice straw lignin is synthesized through chemical modification with the 3-chloro-2-hydroxy-propyl-trimethyl ammonium chloride (CHMAC). After that

[PdCl4]2- was adsorbed by the quaternary ammonium rice straw lignin. The lignin and its derivants were characterized by the scanning electron microscope (SEM)

Fourier transform infrared spectroscopy (FTIR)

thermogravimetric analysis and differential scanning calorimetry (TG-DSC)

respectively. Meanwhile

the effects of pH value

the initial concentration of [PdCl4]2-

the adsorption time on the adsorption properties of quaternary ammonium rice straw lignin were investigated. Furthermore

its selectivity for [PdCl4]2- was also discussed. The results show that the quaternary ammonium rice straw lignin is porous

rough and irregular with excellent thermal stability below 200 ℃ and infrared absorption peak at 1469 cm-1 is attributed to the bending vibration of quaternary ammonium ion. Moreover

the optimum value of pH for [PdCl4]2- adsorption is 2 and the time of adsorption equilibrium is 8 h. The adsorption reaches saturation when the concentration of [PdCl4]2- is 4 mmol·L-1 with 1.120 mmol·g-1 of the saturated adsorption capacity. At the same time

the adsorption process could be described by pseudo-second order kinetic equation and adsorption isotherm could be simulated by Freundlich equilibrium adsorption equation

which indicates that the adsorption is chemical adsorption of monomolecular and nonhomogeneous. In addition

the quaternary ammonium rice straw lignin presents excellent selectivity for [PdCl4]2- when the concentration of hydrochloric acid is less than 1 mol·L-1. The lower concentration of hydrochloric acid

higher initial concentration of [PdCl4]2- and longer adsorption indicate the better of adsorption capacity and selectivity.