The binding capacity of iota-carrageenan to Pb, Cd, and Zn for potential remediation of contaminated soil

• Main Author: Pili, Adora Soriano
• Format: text
• Language: English
• Published: Animo Repository 1999
• Subjects: Heavy metals; Chondrus crispus; Soils > Heavy metal content; Solution (Chemistry); Chemistry
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/2044
• Institution: De La Salle University

The ability of carrageenan to strongly bind to cations suggests its potential use for remediation of contaminated soil. In this study, the capacity of iota-carrageenan to bind to Pb, Cd, and Zn is investigated by flame atomic absorption spectroemtric (AAS). Dialysis is adopted to facilitate the separation between carrageenan-bound and free heavy metals. Artificially contaminated soil samples were used for testing.For single metal systems, binding capacity of iota-carrageenan to the heavy metal ions considered was found to be independent of the metal-carrageenan mixing time. The amounts of metal ions individually bound to iota-carrageenan averaged to about 81 percent, 56 percent, and 31 percent of Pb, Cd, and Zn, respectively. Binding capacity was observed to be pH-sensitive, with the maximum amount of heavy metal ions bound to iota-carrageenan calculated at pH 8, 9 and 6, respectively for Pb, Cd and Zn, with significant effect on Pb. Competition among the heavy metals gauged in terms of their simultaneous binding with iota-carrageenan showed a general trend of Pb (̃31 percent)Zn(̃28 percent)Cd(23 percent). A similar trend and extent of binding are observed during metal binding competition at optimum pH values previously identified. For artificially contaminated soil samples subjected to double carrageenan treatment, extraction of individual metal ions showed that about 72 percent, 46 percent and 37 percent of Pb, Cd and Zn, respectively, were bound to iota-carrageenan. Binding competition among the three metal ions revealed a trend similar to that observed in pure iota-carrageenan solution, i.e. PbZnCd. Results of the experiments showed that the extent of metal extraction is related to carrageenan's binding capacity, binding competition among the metals involved and the soil matrix effect. Efficiency of the extraction scheme indicated a high of ̃72 percent for Pb in single metal system, and low of ̃28 percent for Cd in mixed metal system.