Use of Vegetable Fibers for PRB to Remove Heavy Metals from Contaminated Aquifers—Comparisons among Cabuya Fibers, Broom Fibers and ZVI

The Zero Valent Iron (ZVI) is the material most commonly used for permeable reactivebarriers (PRB). For technical and economic reasons, hoter reactive substances usable in alternativeto ZVI are investigated. The present study takes into account a vegetable fibers, the cabuya,investigating its capacity to retain heavy metals. The capacity of the cabuya fibers to adsorb heavymetals was verified in laboratory, by batch and column tests. The batch tests were carried out withcabuya and ZVI, using copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb). The results obtained bythe cabuya fibers showed a very high adsorption capacity of heavy metals and resulted very similarto those obtained for the broom fibers in a previous study. The high value of the absorption capacityof the cabuya fibers was also confirmed by the analogous comparison made with the results of thebatch tests carried out with ZVI. Column tests, using copper, zinc and cadmium, allowed todetermine for the cabuya fibers the maximum removal percentage of the heavy metals considered,the corresponding times and the time ranges of the release phase. For each metal considered, for agiven length and three different times, the constant of degradation of cabuya fibers was determined,obtaining values very close to those reported for broom fibers. The scalar behavior of heavy metalremoval percentage was verified. An electron microscope analysis allowed to compare, by SEMimages, the characteristics of the cabuya and broom fibers. Finally, to investigate the chemicalstructure of cabuya and broom fibers, the FTIR technique was used, obtaining their respectiveinfrared spectra.