Isotherm Models for Metal Removal Using Modified Graphene

In the present study, a holey graphene oxide (HGO) was synthesized by a fast-designed method via carbonization of apricot shell waste. Raman spectroscopic analysis confirmed the structure of HGO. A simple adsorption method was designed for the removal of La³⁺ and Ni²⁺ by the utilization of HGO. The adsorption rate of La³⁺ progressively reached its maximum after 5 min, while the maximum adsorption of Ni²⁺ ions was achieved after 90 min. The adsorption isotherm data exhibited the best fitting with Langmuir isotherm for the adsorption of La³⁺ and Ni²⁺ with a correlation coefficient (0.9985, 0.9986), and the adsorption is considered to be favourable with a separation factor 0 < R_L< 1, which confirms that the adsorption process takes place on heterogeneous surface adsorbent, which is consistent with HGO nature. This model assumes that adsorption sites increase exponentially with adsorption, resulting in multilayer adsorption. This study suggested that the HGO has proved to be an efficient adsorbent for Ni²⁺and La³⁺ ions removal from aqueous solutions.