Removal of trivalent and hexavalent chromium from aqueous solution using fiber of Agave americana plant and its modified forms

Chromium contamination due to industrial effluents has been recognized as one of the major problems since chromium compounds affect human health leading to adverse health effects of humans. Among many adsorbents that have been experimented with, cellulose fibers have been identified to be very effective for chromium removal. Agave americana, a plant native to Central America, is rich in cellulose fibers, which consist of esters, ethers of alcohol derivatives of cellulose showing coordinating ability toward heavy metal ions. This study is aimed at optimization of solution parameters, such as shaking time, settling time, solution pH and adsorbent dosage, while varying one parameter at a time throughout a broad range keeping others constant, for most efficient adsorption of Cr(III) species, followed by investigation of equilibrium and kinetics aspects under optimized conditions. Adsorption of Cr(III) from solutions of different concentrations on untreated AAF fulfills the requirements of the Langmuir adsorption isotherm at equilibrium which is probably due to the fine fibrous nature of the biosorbent. Moreover, the extent of Cr(III) on Agave americana fiber (AAF), investigated during the early stages of adsorption, leads to the validity of the pseudo first-order kinetics with a relatively high regression coefficient. Although untreated AAF shows a strong affinity toward Cr(III), its adsorption ability toward Cr(VI) is undetectable, suggesting that surface modification of AAF be performed. In this context, EDTA-treated AAF demonstrates a significant improvement on Cr(VI) removal, indicating the possibility of extending the present investigation for removal of chromium species under industrial setting.