Effect of Solvent Extraction on Removal of Heavy Metal Ions Using Lignocellulosic Fiber

Abstract

Kenaf bast, which is lignocellulosic fiber and environment friendly natural material, was tested for its ability to remove copper, nickel and zinc ions from aqueous solutions. The fiber was analyzed for xylose, lignin content, weight loss and dry volume, and extracted with diethyl ether, ethyl alcohol, hot water, or 1% sodium hydroxide to change physical and chemical characteristics of keanf bast. Diethyl ether and ethyl alcohol are organic solvents, which extract only extractives in the cell wall. The weight losses are less than 4.1%, the dry volumes increase up to 0.68 cm3/g, and the changes of lignin content are less than 0.6%. The differences of the heavy metal ions removal capacities are less than 0.05 mg/g, compared to those of control. Hot water and 1% sodium hydroxide remove cell wall components as well as extractives in the cell wall. In addition, during the extraction process the cell wall is swollen by the delamination of cell wall layers, xylose and lignin are exposed. The weight losses increases up to 24.0%, the dry volumes increase up to 1.20 cm3/g, and the changes of lignin content are less than 0.6%. The difference of the heavy metal ions removal capacities of kenaf bast increase up to 0.14 mg/g, and are much higher than those of diethyl ether and ethyl alcohol. The above results show that to increase the heavy metal ions removal capacities, the extraction chemicals may swell the cell wall more than water does and remove the cell wall components as well as extractives to change cell wall chemistry and architecture.