Removal of Ni (II) from aqueous solution using modified MCM-41 nano-adsorbents

In this study, a synthetic and modified PPAP-MPTMS-MCM-41 nano-adsorbent was used to remove nickel (II) during a batch process. Studying the parameters that were effective on adsorption revealed that the PPAP-MPTMS-MCM-41 adsorbent was the most effective in the adsorption of nickel (II) from a standard solution (Conc. = 5 mg/L, volume = 100 mL) under the following conditions: pH=8, contact time = 20 min, 6 wt.% of poly para-aminophenol (PPAP) ligand, adsorbent mass = 0.3 g, 1 molar hydrochloric acid (to remove nickel from the adsorbent), and NaCl salt with a concentration of less than 100 g/L. The results showed that the Langmuir isotherm had a higher linear and non-linear fitting with the experimental data. Investigating the kinetic models and mass transfer of this adsorption process showed that the experimental data were in good agreement with the pseudo-second-order kinetic model and the intra-particle mass transfer model. According to thermodynamic studies, this adsorption process is endothermic; its Gibbs free energy value is positive such that with an increase in temperature, it goes to lower values, and thus the process progresses spontaneously.