Design, synthesis, and application of negative ion-ion sieve synergistic adsorbent based on cross-linked carrier

Abstract

The growing demand for lithium in the new sustainable society is advancing technology for lithium recycling from real Salt Lake brine, which has low concentrations in a near-neutral condition. Traditional adsorbents for this process typically exhibit excellent adsorption ability in alkaline solutions, limiting their industrial application for recycling lithium from the real salt lake. In this work, we designed and synthesized a manganese-based ion sieve loaded onto a cross-linked polystyrene carrier and modified it, HMO@PS-IDA, by incorporating iminodiacetate onto a polystyrene-based ion sieve. These conditions typically reduce the charge density on the surface of adsorbents, hindering the ion exchange process. Our innovative approach introduces cross-linked polystyrene for adsorbent granulation, providing modification sites, and selects Iminodiacetic acid (IDA) as the preferred anionic donor. The dual-structure design of anionic groups and ion sieves in HMO@PS-IDA results in a remarkable 2.6-fold increase in adsorption capacity at pH = 7, surpassing the individual capacities of its components. The adsorbent exhibits a regular spherical shape with a rough surface and uniformly distributed ion sieves, achieving an adsorption capacity of 6.85 mg·g⁻¹ within 40 min in a real neutral system. The synergistic adsorption mechanism is attributed to the CHELPG atomic charge decrease from −0.16 to −1.44, maintaining the ion exchange driving force under neutral conditions. This innovation compensates for the loss of surface charge on the adsorbent, enabling a wide pH application range and overcoming the low adsorption capacity issue in near-neutral conditions. HMO@PS-IDA also demonstrates exceptional lithium adsorption capacity, with a 10-cycle adsorption capacity of 6.3 mg·g⁻¹, maintaining 92.1 % of the initial performance. These properties make HMO@PS-IDA a direct candidate for extracting Li⁺ from neutral salt lake brines, and our findings provide a theoretical foundation for the modification of adsorption materials.