(58d) Thermodynamic Modeling of the Aqueous Copper(II) - Nitrate - Chloride - Sulfate System with the Electrolyte-NRTL Model

Thermodynamic Modeling of the Aqueous Copper(II) - Nitrate - Chloride - Sulfate System with the Electrolyte-NRTL Model

Benjamin Caudle, Yuan Li, Chau-Chyun Chen

Texas Tech University

Abstract

Electronic waste (e-waste) is waste associated with computers and cell phones, as well as increasingly digitized appliances such as refrigerators and ovens. As demand grows in emerging markets, the need for proper handling of this waste increases as well [1]. A unique characteristic of e-waste is the presence of both valuable materials, such as copper and members of the platinum group, and hazardous materials. Proper recycling of e-waste is necessary to prevent the release of toxic substances into the environment and has the added benefit of yielding materials that can be reused or sold. The most promising method of recycling is through leaching with mixed acids, in which metals can be selectively dissolved depending on the composition of the leaching solution. Copper is typically the most prevalent metal in e-waste and, even if it is not recovered for its own sake, its behavior in solution has a large impact on the system as a whole. For this purpose, a thermodynamic model of copper in common acid solutions is a useful tool for the design of recycling systems.

The electrolyte non-random two-liquid (eNRTL) model has proven to work for a wide range of electrolytes in both single and mixed solvents [2-4]. The nitric, chloric, and sulfuric acid systems already have validated eNRTL models available [5-7], and the prime advantage of the NRTL model is straightforward and accurate extension to other multicomponent systems.

This work extends the eNRTL model to cover the behavior of copper(II) in nitric, chloric, and sulfuric acids and mixtures thereof. Beginning with the binary systems, parameters are regressed from the available literature data. This includes phase equilibrium and calorimetric properties as well as solubility data for the respective copper salts. The binary models are then integrated with the existing acid system models and validated against literature data for the ternary and quaternary systems. The resulting model is an integral part of the overall model for e-waste recycling processes.

[1] Widmer, Rolf et al., Global perspectives on e-waste, Environmental Impact Assessment Review, Volume 25, Issue 5, July 2005, 436-458

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[3] Chen, C.-C. et al., A Local Composition Model for the Excess Gibbs Energy of Aqueous Electrolyte Systems. AIChE Journal 32 (1986) 444-454.

[4] Song, Y. and Chen, C.-C., Symmetric Electrolyte Nonrandom Two-Liquid Activity Coefficient Model. Ind. Eng. Chem. Res. 48 (2009) 7788-7797.

[5] Wang, M. et al., Thermodynamic Representation of Aqueous Sodium nitrate and Nitric Acid Solution with Electrolyte NRTL Model. Fluid Phase Equilibria. 407 (2016) 105-116

[6] Hassanjani, S. et al., Comprehensive Thermodynamic Modeling of Complex Mixed-Solvent Electrolyte Systems: An Investigation on Water-Hydrogen Chloride-Methanol Ternary System. In preparation.

[7] Que, H. et al., Thermodynamic Modeling of the Sulfuric Acid - Water - Sulfur Trioxide System with the Symmetric Electrolyte NRTL Model. J. Chem. Eng. Data. 56 (2011) 963-977.