(308c) Process Simulation, Optimization, and Intensification of Electrodialysis-Based Mineral Recovery from Industrial Wastewater

Materials like Lithium, Nickel and Cobalt, Nitrates and Phosphates are of critical importance in the energy, manufacturing, and chemicals industries [1,2]. The availabilities of these materials and their derived products are central to the national security and economic independence of the United States [3]. One way to reduce dependence on external sellers is via mineral recovery from industrial wastewater. While less than 10% of industrial wastewater is reused, and even less is used for resource recovery [4], estimates show that cobalt recovered from water produced by US oil and gas extraction is sufficient to meet demands for over a century [5,6]. Since these valuable minerals exist as dissolved ionic species, our ability to exploit this overlooked resource is bottlenecked by the effectiveness of ion separation technologies. However, the development and intensification of efficient mineral recovery systems is challenging. The heterogenous nature of wastewater chemical properties, such as pH and salinity, make a one-size-fits-all approach to equipment configuration and process design ineffective. While there is a wide range of membranes with varying filtration capabilities, it is difficult to overcome the combinatorial complexity of picking separation methods and units that yield optimal results, be it in terms of energy efficiency, mineral recovery etc.

Process simulation tools to model and optimize wastewater treatment processes are deficient and do not allow for the multi-parametric optimization of design and process decision variables required to identify optimal process designs. Similar tools that exist for chemical engineering processes can perform sensitivity analysis on a series of interconnected and user-determined unit operations but perform the optimization of each modular single-task unit in isolation rather than as a whole process. This is particularly important for optimizing resource recovery from wastewater due to the low separation efficiency of current processes, which necessitates the exploration of novel process designs. The Design Building Blocks fill this gap by constructing a superstructure that simultaneously represents all plausible process pathways. This representation proposed by Hasan and co-workers [7] uses “building blocks” that represent a volume bounded by four interfaces with other blocks, through which the transfer of mass, energy and momentum can occur. When arranged in a 2-dimensional grid, these blocks represent various process phenomena, tasks and unit operations. This representation allows for the simultaneous multi-scale optimization of material, process and flowsheet parameters for process systems given a target performance metric. This makes it particularly suitable for discovering process intensification opportunities without requiring prior knowledge of the unit operations involved. The representation was used in SPICE (Systematic Process Intensification of Chemical Enterprises) [8] for the systematic discovery of chemical process configurations and flowsheets without an exhaustive search [9-12].

In this work, we extend the SPICE framework for modeling, simulation and optimization of membrane-based separation technology that can address many aqueous separation problems. Specifically, we will develop phenomenological representations of multiple membrane processes using a transition state theory-based kinetic barrier network approach [13, 14], which allows the modeling of multi-component membrane transport via a network of experimentally measurable activation energy barriers. This allows the building blocks approach to connect molecular-scale material features, represented by the energy barriers, with unit-scale and flowsheet-scale design elements and decisions, and thus elucidates interactions, synergies and trade-offs in physicochemical phenomena involved in trans-membrane ion transport at multiple scales. Inverse design of ion exchange membranes can also be performed to identify opportunities for improved membrane chemistry by allowing transport energy barriers to be a decision variable. Building block representation of electrodialysis is used alongside pressure-based membrane separation, reactors, flash separation and other phenomena represented in SPICE to optimize pathways for wastewater treatment for mineral recovery.

Keywords: Process Design & Development, Ion Exchange, Membrane Separation, Inverse Design, Sustainability, Water treatment

References:

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