Synthesis of Citric Acid-Modified Jackfruit Leaves as an Adsorbent for Enhanced Adsorption of Pb2+ and Cd2+: Optimization, Characterization, and Adsorption Performance

Abstract

In this study, we synthesized the citric acid-modified jackfruit leaf powder (CIJLP) to comprehend the adsorption behavior and mechanism of Pb²⁺ and Cd²⁺ adsorption in simulated aqueous solution. This investigation suggested that CIJLP shows 125 mg/g of maximal adsorption capacity for Pb²⁺, which is nearly 1.6 times more than Cd²⁺ (∼77 mg/g). The optimum pH values for adsorption of Pb²⁺ and Cd²⁺ were determined to be 6.0 and 5.0, respectively. The CIJLP was characterized using FT-IR, FESEM–EDX, and XPS analyses. The FT-IR and EDX analyses revealed the crucial role of oxygen-containing functional groups onto CIJLP, which substantially contributed to the heavy metal removal with extremely high adsorption capacities. Based on regression coefficient and RMSE values, adsorption behavior of Cd²⁺ and Pb²⁺ onto CIJLP were best fitted by Freundlich and Langmuir isotherm models. Moreover, kinetic data was better represented by the pseudo-second-order model. Consequently, the heavy metal adsorption onto CIJLP was chemisorption on homogenous monolayer. It was primarily controlled by cation exchange and surface precipitation mechanism. Due to its significantly efficient adsorption for Pb²⁺ and Cd²⁺, as compared to the other biowaste-based adsorbents, CIJLP can be utilized industrially and is socially acceptable as an adsorbent for efficient removal of these toxic ions from an aqueous solution.