Fig. 5. Adsorption kinetic plots and curving fitting by pseudo-first-order (solid line) and pseudo-second-order (dot line) kinetic models of Cr(iii) on GH (A) and GA-GH (B). The pseudo first order and pseudo second order kinetic models were according to the equations of ln(q_e − q_t) = ln(q_e) − k₁t and t/q_t = 1/k₂q_e² + t/q_e, respectively, where q_e and q_t are the capacities (mg g⁻¹) of metal ions adsorbed at equilibrium and time t (min), k₁ is the rate constant of pseudo first order model (min⁻¹), and k₂ is the rate constant of the pseudo second order model of adsorption (g mg⁻¹ min⁻¹).