Metallic ions recovery from membrane separation processes concentrate: A special look onto ion exchange resins

Abstract

A future scenario of water scarcity, combined with minerals resources exhaustion, led to the development of treatments capable to achieve water reuse and by-products recovery. Whereas most membrane separation processes (MSPs) guarantee a wastewater treatment at reuse level, their concentrate represents in most cases a liability due to its greater complexity and environmental impact. However, rather than its treatment, the concentrate from mining wastewater treatment is presented as an opportunity for by-products recovery by ion exchange (IX) resins. It was summarized the efficiency and limitations of MSPs (pressure-, thermal-, osmotic-, and electrical-driven processes) for reuse water reclamation from acid mining wastewater, followed by a critical discussion of IX process for metallic compounds recovery from their concentrate. The advantages of IX over conventional treatment and disposal practices were highlighted, with special attention given to factors that affect the IX equilibrium, kinetics, and thermodynamics, in batch and continuous operation, in addition to the models used to describe them. Models for error estimations were presented as well along a criticism for the use of linearized models for data interpretation. An overview of the lab-scale studies pointed out that IX would be an interesting alternative for concentrated solutions valorization. As an attempt to scale up IX for pilot- and full-scale applications, it was presented a step-by-step mass balance that allows for a batch system design and resins mass estimation for a given concentrate flow rate. Finally, future perspectives are presented pointing out to integrated IX system, impregnated resins, and columns systems, that represents knowledge gaps to be covered in the next few years.