A B S T R A C TThis study aimed to analyze the efficiency of in natura and chemically modified with sodium hydroxide macadamia mesocarp as alternative adsorbents for removal of Pb 2+ and Cr 3+ from aqueous medium. The effect of chemical modification on the in natura macadamia mesocarp with respect to chemical structure and morphological feature were verified by Fourier transform infrared spectroscopy, scanning electronic microscopy, and zero point charge. The best adsorption occurred when pH ranged from 4.0 to 5.0. The adsorbent-adsorbate equilibrium time was found to be at 200 min and followed the pseudo-second-order kinetic model. The maximum adsorption capacity of the modified mesocarp for Pb 2+ and Cr 3+ was found to be 91.40 and 81.63 mg g −1 , respectively. The thermodynamic parameters indicated an increase of the system spontaneity after the modification, corroborated by the negative values of Gibbs' energy. Besides greater adsorption, the modified material also had greater ion desorption, approximately 94% for Pb 2+ and 70% for Cr 3+ , and may be reutilized as a retention filter for metals in the future.
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