Enhancing Resource Circularity in Aluminum Production through Nanofiltration of Waste Cryolite

Overview

Aluminum refining produces cryolite-based electrolytes that gradually accumulate sodium, lithium, and potassium impurities, rendering them unusable and creating a persistent waste problem. Disposal of this spent cryolite contributes to fluoride and aluminum contamination in soil and water systems.

This research introduced a nanofiltration-based upcycling method that selectively removes monovalent impurities while retaining aluminum, enabling reuse of the purified electrolyte and significantly reducing environmental waste. A polyelectrolyte-coated NF membrane was developed to enhance charge-based selectivity, exploiting Donnan exclusion to favor sodium permeation and aluminum retention.

Work

My role centered on data analysis, figure creation, and manuscript development, transforming experimental results into quantitative insights and publication-ready visuals that communicated the project's scientific and sustainability impact.

• • Analyzed ion rejection experiments for coated vs. uncoated NF membranes under varying pH and flux conditions
• • Created high-impact figures and schematics—including the cryolite filtration process, membrane cross-sections, and performance plots—for journal publication
• • Synthesized visual summaries of process efficiency, membrane stability, and module-scale energy consumption for publication graphics

Results & Impact

The study demonstrated that Donnan-enhanced nanofiltration can recover aluminum with high purity (99.1% rejection) while allowing monovalent ions (Na⁺, K⁺, Li⁺) to pass freely, reducing waste toxicity and improving recyclability.

Key findings include: Na/Al separation factor increased up to 102.0 at low pH, indicating strong charge-based selectivity; aluminum concentration in the treated permeate dropped to 0.00194%, approaching safe effluent thresholds; retentate Na/Al ratio ≈ 2.6, meeting operational requirements for reintroduction into Hall–Héroult electrolytic cells.

This work supports a closed-loop aluminum production model, where waste electrolytes are recycled into active materials—bridging membrane science and sustainable process engineering. Module-scale modeling confirmed viability of NF treatment at industrial scale with manageable energy use.

Published Research

View the complete published research paper detailing the novel nanofiltration method and experimental results.