Nickel (II) removal using modified Citrus limettioides peel

Abstract

The Ni(II) adsorption capacity of carbon derived from Citrus limettioides peel (CLP), which is a novel waste material (CLPC), was evaluated regarding contact time, pH and adsorbent dose during batch adsorption processes with raw CLP. The optimal contact time for the adsorption of Ni(II) ions onto the peel and peel carbon was 3 h, and the optimal pH ranged from 5.0 to 8.0 for CLP and 4.0–8.0 for CLPC, respectively. The removal percentage decreased from 85.0 to 70.0 % for CLP and remained nearly constant (99 %) for CLPC when the initial Ni(II) concentration was increased from 10 to 50 mg L−1. The equilibrium data fit the Langmuir isotherm with a high R 2 value, indicating that the Ni(II) ions formed a homogenous monolayer on the adsorbent surface. Adsorption capacity of Ni(II) ions on peel (CLP) and peel carbon (CLPC) was found to be 25.64 and 38.46 mg g−1, respectively. The surface morphology and functionality of the CLP and CLPC before and after adsorption were characterized using SEM, EDX and FT-IR. Various thermodynamic parameters, including the standard Gibbs free energy (∆G°), standard enthalpy (∆H°) and standard entropy (∆S°), were evaluated. The CLP and CLPC were tested with Ni(II) plating wastewater through a batch-mode process over five cycles; CLPC showed better results than CLP.