Heavy metal ion sorption of unmodified and modified lignocellulosic fibers

Many of our water resources are contaminated with heavy metals, for example mercury, lead, copper, cadmium, nickel, cobalt, iron, zinc and manganese from automobiles, industrial effluents and mine waste water. Contaminated water cannot be used for municipal water supply, industry or irrigation. Therefore, heavy metals must be removed from water resources.; This study concentrates on the use of lignocellulosic fiber to remove selected heavy metals from water. Kenaf bast, kenaf core, sugar cane bagasse, cotton, coconut coir and spruce were chosen to investigate Cu(II), Ni(II) and Zn(II) ion sorption capacity.; In unmodified lignocellulosics, it has been reported that lignin content is important in heavy metal removal from water. This study shows that lignin availability and content is a critical factor in heavy metal removal from water.; Diethyl ether and ethyl alcohol are organic solvents, which extract only chemicals in the cell wall or redistribute the dissolved extractives, and deaspirate some of aspirated pits. The differences of the heavy metal ions sorption capacities are less than 0.08 mg/g, compared to those of the unmodified lignocellulosics.; Hot water and 1% sodium hydroxide deaspirate some of aspirated pits. During the extraction process the cell wall of lignocellulosic fiber swells by delamination of cell wall layers. Some of amorphous matrix and extractives are removed and shrunk. Delamination and shrinkage change the amount of exposed lignin in lignocellulsoics. The difference of the heavy metal ions sorption capacities of lignocellulosics increase up to 0.29 mg/g, compared to those of the unmodified.; The heavy metal ions sorption capacities increase, when the extraction chemicals swell lignocellulosics more than does water, expose more lignin, and dry volume and water sorption increase. In the 2N nitric acid reaction the heavy metal ions sorption capacities correlate with the lignin content of lignocellulosics. When the phenolic hydroxyl groups of lignin are substituted with the epichlorohydrin reaction products, the heavy metal ion sorption capacities decrease. The results show that the amount of exposed lignin is the most important factor in the heavy metal ions sorption capacities.