Non-dispersive selective extraction of germanium from fly ash leachates using membrane-based processes

ABSTRACT

Non-dispersive selective extraction of Ge(IV) tartrates was carried out from simulated fly ash solutions containing heavy metals through supported liquid membranes (SLM). The optimum transport was obtained using a PTFE membrane containing Alamine 336 5%v/v in the condition of tartaric acid 2.76 mmol/L and HCl 1 mol/L in feed and strip phases, respectively. Under this condition, a hollow fiber (HF) SLM experiment was conducted. The results showed that this system could transport germanium from the feed to the strip phase so much faster than the flat sheet (FS) SLM system. The rate of transport through HFSLMs is comparable to dispersive extractions.

Abbreviation: A: Effective area of the membrane (cm²); BDL: Below detection limit; C_f,: Feed concentration (mg/L); C_t,: Initial concentration (mg/L); D: Distribution coefficient; ELM: Emulasion liquid membranes; FSSLM: Flat sheet supported liquid membrane; HF: Hollow fiber; LLX: Liquid-liquid extraction; P: Permeation coefficient (m/h); PTFE: Poly tetra fluoro ethylene; PVDF: Polyvinylidene difluoride; T: Tartrate species (C₄H₄O₆); T: Temperature (K); %T:Germanium transport effeciency; V: Volume of feed solution (cm³); t: time (h); η: Viscosity (P.s (c.P)); κ: Boltzmann constant; r: Ionic radius of species; τ: Tortuosity of the membrane; ρ: Porosity; α: Separation factor.

KEYWORDS:

• Supported liquid membrane
• non-dispersive extraction
• germanium
• fly ash
• heavy metals

Acknowledgments

This research was done in the laboratory of the Department of Chemical Engineering, Universitat Politècnica de Catalunya (Barcelona-Tec), Vilanova i la Geltrú Campus, Spain. The authors thank Dr. Maria Teresa Coll for her assistance and scientific consultation.