Multivariate optimization of Cd(II) biosorption onto Ulmus tree leaves from aqueous waste

Ulmus tree leaves were successfully used as a novel and efficient biosorbent for removing cadmium, (Cd(II)), from aqueous solutions in a batch system. A multivariate strategy for optimization of removal efficiency conditions of Cd(II) was carried out. A 2³ full factorial design with three center points (9 runs) was performed for screening the main variables and reducing the large number of experimental runs. Initial concentration of metal ion (C _m), amount of sorbent (m), and pH were considered as the three main variables at two different levels. The maximum removal efficiency of Cd(II) was achieved within 1 h contact time. It was found that all the main factors and their interactions were significant at p < 0.05. Doehlert response surface methodology was utilized (13 runs) for finding a suitable mathematical model. The analysis of variance and some statistical tests such as lack-of-fit, coefficient of determination (R ²), and residual distribution plot confirmed the validity of the model. The optimum conditions for maximum removal of Cd(II) by Ulmus tree leaves were found as pH = 3.4, m (amount of sorbent) = 0.128 g, C _m (initial concentration of metal ion) = 12.1 mg L^?1.