Removal of Heavy Metal Ions Using Modified Celluloses Prepared from Pineapple Leaf Fiber

Since large amounts of pineapple leaves are abandoned after harvest in agricultural areas, the possibility of developing value-added products from them is of interest. In this work, cellulose fiber was extracted from pineapple leaves and modified with ethylenediaminetetraacetic acid (EDTA) and carboxymethyl (CM) groups to produce Cell-EDTA and Cell-CM, respectively, which were then used as heavy metal ion adsorbents. A solution of either lead ion (Pb²⁺) or cadmium ion (Cd²⁺) was used as wastewater for the purpose of studying adsorption efficiencies. The adsorption efficiencies of Cell-EDTA and Cell-CM were significantly higher than those of the unmodified cellulose in the pH range 1–7. Maximum adsorptions toward Pb²⁺ and Cd²⁺ were, for Cell-EDTA, 41.2 and 33.2 mg g^–1, respectively, and, for Cell-CM, 63.4 and 23.0 mg g^–1, respectively. The adsorption behaviors of Cell-CM for Pb²⁺ and Cd²⁺ fitted well with a pseudo-first-order model, but those of Cell-EDTA for Pb²⁺ and Cd²⁺ fitted well with a pseudo-second-order model. All of the adsorption behaviors could be described using the Langmuir adsorption isotherm. Desorption studies of Pb²⁺ and Cd²⁺ on both adsorbents using 1 M HCl suggested that regenerability of Cell-EDTA was, for both adsorbates, better than that of Cell-CM. Moreover, adsorption measurements in a mixture of Pb²⁺ and Cd²⁺ at various ratios showed that for both adsorbents the adsorption of Pb²⁺ was higher than that of Cd²⁺, while the adsorption selectivity for Pb²⁺ of Cell-CM was greater than that of Cell-EDTA. This study showed that the modified cellulosic adsorbents made from pineapple leaves were able to efficiently adsorb metal ions.