Preparation of ethylenediamine-modified pectin/alginate/Fe₃O₄ microsphere and its efficient Pb²⁺ adsorption...

As a common macromolecular carbohydrate, pectin has a strong affinity for Pb²⁺. An ethylenediamine modified pectin (EP₄₈) with 48 % of amidation was prepared and exhibited great removal efficiency towards Pb²⁺ in our previous study. However, the EP₄₈ has drawbacks in adsorption including low mechanical strength and difficulty in separation. In this study, EP₄₈ was compounded with sodium alginate (Alg) and Fe₃O₄ to synthesize EP₄₈/Alg/Fe₃O₄ microsphere. The physicochemical properties and Pb²⁺ adsorption characteristics of microsphere were analyzed. It was found that the microsphere exhibited good thermal stability, mechanical strength, porous structure, as well as acid tolerance. The pseudo-second-order model well described the kinetics of adsorption process, indicating the chemical adsorption is dominant. The Langmuir model fitted the experimental data well, and the maximum adsorption capacity reached 175.19 mg/g. Adsorption-desorption experiments showed that the removal rate of the microsphere maintained over 98.9 % after 10 cycles. The X-ray photoelectron spectroscopy (XPS) analyses revealed that the potential adsorption mechanism included ion-exchange and chelation. The above results suggested its potential use for the removal of Pb²⁺ from wastewater.