(58b) Thermodynamic Modeling of Aqueous Nickel Nitrate-Nickel Chloride-Nickel Sulfate System with Electrolytes NRTL Model

Thermodynamic Modeling of Aqueous Nickel Nitrate-Nickel Chloride-Nickel Sulfate System with Electrolytes NRTL Model

Yuan Li, Benjamin Caudle, Chau-Chyun Chen

Texas Tech University

Abstract

Millions of tons of electronic waste such as computers and mobile phones, known as e-waste, are produced each year. Traditionally most e-waste has been disposed of in landfills [1], but in recent years recycling of e-waste is being taken seriously due to environmental concerns and potential financial gains from recovery of materials. In one mode of recycling, metals in e-waste are dissolved in strong acids and then the valuable metals are recovered through electrochemical methods. Nickel is one of the significant metals in e-waste and its dissolution and saturation can significantly affect the efficiency of the recovery system. Therefore, a comprehensive and validated thermodynamic model for nickel salts in strong acids is a necessity for process simulation of e-waste recycling processes.

With a wide applicability from dilute to saturated electrolyte solutions, the electrolytes NRTL (eNRTL) model is one of the most accurate thermodynamic models for aqueous and mixed solvent electrolytes [2-4]. Moreover, the eNRTL model has been successfully validated for various strong acids and mixed acid systems [5-7]. In this work, we extend the eNRTL model and develop a comprehensive thermodynamic model for nickel salts in strong acids including nitric acid, hydrochloric acid, and sulfuric acid.

We first identify the eNRTL binary interaction parameters for aqueous nickel nitrate, nickel chloride, and nickel sulfate electrolyte systems from available literature data using phase equilibrium properties such as vapor pressure, osmotic coefficient, mean ionic activity coefficient, and calorimetric properties such as molar heat capacity and excess enthalpy. Salt solubility data are then used to identify thermodynamic properties for corresponding salt crystals. The binary system models are then integrated with the strong acid models developed with eNRTL [5-7] and further validated against available data for ternary nickel salt - acid − water systems. These ternary system models will form a sound thermodynamic foundation for use in process simulation of e-waste recycle processes.

[1] Robinson, B.H., E-waste: An assessment of global production and environmental impacts. Science of the Total Environment 408 (2009) 183-191.

[2] Chen, C.-C. et al., Local Composition Model for Excess Gibbs Energy of Electrolyte System. Part I: Single Solvent, Single Completely Dissociated Electrolyte Systems. AIChE Journal 28 (1982) 588-596.

[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.