Adsorption performance and mechanism of Schiff base functionalized polyamidoamine dendrimer/silica for aqueous Mn(II) and Co(II)

• Published in: Chinese chemical letters 2020-10, Vol.31 (10), p.2742-2746
• Main Authors: Qiao, Wenzhu, Zhang, Peixu, Sun, Lixiang, Ma, Songmei, Xu, Wenlong, Xu, Shengguang, Niu, Yuzhong
• Format: Article
• Language: English
• Subjects: Adsorption; DFT calculation; PAMAM dendrimer; Schiff base
• ISSN: 1001-8417; 1878-5964
• DOI: 10.1016/j.cclet.2020.04.036

Schiff base functionalized PAMAM dendrimer/silica were synthesized and employed for the removal of aqueous Mn(II) and Co(II). The adsorption performance and mechanism were revealed based on experiment and DFT calculation. [Display omitted] Schiff base functionalized polyamidoamine (PAMAM) dendrimer/silica were prepared for the adsorption of aqueous Mn(II) and Co(II). The effects that influence the adsorption were investigated systematically and the adsorption mechanism was illustrated by theoretical calculation. The optimum adsorption pH are 4 and 6 for Mn(II) and Co(II). Adsorption kinetics follow pseudo-second-order model and the rate-controlling step is film diffusion process. Adsorption isotherm shows that high initial metal ion concentration facilitates the uptake of metal ions. The adsorption capacity increases first and then decreases in the temperature range of 15–35 °C. Density functional theory (DFT) calculation demonstrates that Schiff base functionalized PAMAM dendrimer tends to coordinate Mn(II) and Co(II) with the oxygen atoms of hydroxyl and carbonyl groups, nitrogen of tertiary amine and imino groups. The imino and tertiary amine groups mainly dominate the adsorption. The reproducibility of the adsorbents indicates they can be regenerated by 5% thiourea and 0.5 mol/L HNO3 solution efficiently.