ENHANCED METAL-BINDING CAPACITY OF NaOH TREATED LARREA TRIDENTATA LEAF TISSUE

Larrea tridentata, or creosote bush, is a common desert plant that inhabits the Chihuahuan Desert. Due to its great abundance and high growth tolerance of heavy metal-contaminated soils, it was chosen as the primary candidate for this study. Previous experiments conducted on inactivated and untreated sodium hydroxide (NaOH) Larrea tridentata leaf tissues showed that it effectively bound metal ions from aqueous solutions. These pure metal ion solutions consisted of copper(II), cadmium(II), nickel(II), lead(II), zinc(II), and chromium(III). In order to understand the effects of NaOH modification on the creosote bush’s metal ionbinding ability, batch modification studies were conducted. Results from these modification studies showed an increase in metal binding for every metal tested. We believe that the enhanced metal-binding ability of the NaOH modified biomass of Larrea tridentata is due to the conversion of methyl esters to carboxylic groups. Carboxylic groups have a higher affinity to bind metal ions at pH 5 since they are deprotonated and thus promote the approach of positively charged cations. Data from these experiments suggest that NaOH modification may be a process to further improve heavy metal binding by creosote bush tissues.