Dynamic and static models for biosorption of Cd2+ ions onto peel of Artocarpus nobilis fruit

• In this study, various static and dynamic models were applied to the biosorption system, consisting of Cd 2+ adsorbate and peel of Artocarpus nobilis fruit as the biosorbent. • An excellent Cd 2+ removal of 88% in batch experiments was determined under optimized conditions of 150 min shaking time, 15 min settling time, 5.5 – 7.0 pH range at 150 rpm rotation speed. • The extent of removal of Cd 2+ is independent of both the heating time and heating temperature. • Linearized Langmuir adsorption isotherm models lead to regression coefficients of 0.976 with a high biosorption capacity of 13.7 mg g -1 . • According to the Webber Morris intra-particle diffusion model, the boundary layer thickness of the biosorbent developed by the Cd 2+ solution retards the movement of Cd 2+ ion through diffusion. • Dynamic models, such as the Thomas model, Adam’s-Bohart model and Yoon Nelson model can be used to explain the adsorption behaviour of Cd 2+ on the biosorbent under flowing conditions. Biosorption has become attractive in the recent past as a cost-effective and environmentally friendly methodology. As biosorbents are usually heterogeneous consisting of many organic functionalities, change in solution pH would cause differences of their reactivities thereby affecting the extent and the modes of mass transfer of adsorbates from the solution phase to the solid biosorbent phase. Consequently, it is important to have model studies to extrapolate toward large scale treatment suitable for commercialization. Although model studies have been established for small-scale batch experiments, biosorption models for dynamic studies have not been much elaborated. In order to fill this void, various static and dynamic models were applied for the biosorption system consisting of Cd 2+ adsorbate and peel of Artocarpus nobilis fruit as the biosorbent. Systematic investigation conducted on the biosorbent leads to an excellent Cd 2+ removal of 88% in batch experiments under optimized conditions of 150 min shaking time, 15 min settling time, 5.5 – 7.0 pH range at 150 rpm rotation speed. The extent of removal of Cd 2+ is independent of both the heating time and heating temperature. Fitting of equilibrium biosorption data on linearized Langmuir adsorption isotherm models leads to the regression coefficients of 0.976 with biosorption capacity of 13.7 mg g −1 . Moreover, dynamic adsorption models, namely, the Thomas, Adam’s-Bohart and Yoon Nelson, are also successfully fitted to the Cd 2+ removal data taken under dynamic conditions. Moreover, the effect of boundary layer thickness explained by the intra-particle diffusion model could be considered in extending the removal of Cd 2+ at large-scale.