Adsorption of copper ions from solution by heavy metal stressed Larrea tridentata (creosote bush) biomass

Larrea tridentata (creosote bush) was found naturally growing in heavy metal contaminated soils. Samples of Larrea tridentata were collected from seven different locations to study their ability to bind copper ions from solution. Samples from the same locations were either oven dried at 90 C or lyophilized in order to determine differences in drying conditions. Batch laboratory experiments were conducted with the leaves, stems, and roots of Larrea tridentata in order to determine pH profiles, time dependencies, and total copper binding capacities. It was determined by the pH profile experiments that the optimum copper binding pH was between 5 and 6. A maximum adsorption of copper ions was observed within five minutes of reaction time for most of the biomass collected from the various sites. The copper binding capacity experiments showed that one gram of biomass can bind as high as 23.7 mg and as low as 7.6 mg of copper. The capacity to bind copper ions by the biomasses varied according to the location of the sample site. The leaves generally bound copper than the roots and stems. The stems bound the least amount. These differences in capacities correlate with the distances from the collection site to the possiblemore » contamination source. The closer the sample to the possible source, the greater the copper binding capacity. The desorption studies showed that once bound to the creosote biomass, it was possible to remove as much as 99.9% of the bound copper.« less