Adsorption of heavy metal ions by iron tailings: Behavior, mechanism, evaluation and new perspectives

Here we report the adsorption of heavy metal ions from wastewater by the pellet material (IT@SA) of iron tailings (IT) compounded with sodium alginate (SA) as a regenerable adsorbent. The adsorption capacities of IT@SA on Zn2+, Cu2+, Pb2+ and Ni2+ were 1.748 mg/g, 2.404 mg/g, 10.000 mg/g and 1.279 mg/g, respectively. The adsorption behavior would be in accordance with the Langmiur isothermal adsorption model, the pseudo second-order kinetic model and the intra-particle diffusion model, indicating that the adsorption process was mainly controlled by monolayer chemisorption on heterogeneous surfaces, and that the adsorption proceeded spontaneously due to intermolecular interactions. The selective adsorption of IT@SA can be represented as exhibited Pb2+ > Cu2+ > Zn2+ > Ni2+ under competitive adsorption conditions. The adsorption mechanisms mainly include surface physical adsorption, ion exchange, functional group complexation, precipitation, electrostatic attraction, etc. This work opens up a new direction for designing stimuli-responsive materials for energy-efficient and sustainable heavy metal ions adsorption and water purification, while the recycling of iron tailings contributes to the sustainable development of China's iron ore processing industry. It fully conforms to the concept of clean production and efficient utilization of industrial solid waste materials.