Encapsulation of a powdery spinel-type Li⁺ion sieve derived from biogenic manganese oxide in alginate beads

Abstract

© 2016 Elsevier B.V. A powdery lithium ion sieve (HMO) derived from biogenic birnessite was homogeneously integrated in sodium alginate (AL) beads. The composite beads were then characterized and their Li+adsorption properties were investigated. Scanning electron microscopy–energy dispersive spectroscopy analysis showed that the HMO particles were homogeneously dispersed in the AL beads even after drying. The adsorption isotherm of Li+adsorption to HMO encapsulated in AL beads (HMO–AL) was well fitted by the linear Langmuir model, and the beads showed a maximum adsorption capacity of 3.61 mmol/g based on HMO, which is comparable with the value of the original powdery HMO. Kinetic studies revealed that adsorption of Li+follows a pseudo-second-order model with rate constant k2 = 2.8–11.9 × 10− 3 g/(mmol min) for the initial Li+concentration range 2.56–4.23 mM. Diffusion of Li+from aqueous solution to the HMO particle through the Ca–AL network is the rate-limiting step for Li+adsorption to HMO–AL beads. The HMO-AL beads enhanced the handling efficiency for Li+adsorption and reused without significant reduction of Li+adsorption efficacy.