研究目的
To achieve selective recovery of indium from sulfuric acid solutions containing multiple metal ions using continuous counter-current foam separation with anionic organophosphate surfactants.
研究成果
The optimized surfactant combination of anionic A219B and nonionic POOE20 enabled complete and selective recovery of indium from multi-metal solutions using CCFS, with high enrichment ratios and separation factors. The method showed feasibility even with interfering Fe(III) when reduced with ascorbic acid. This approach expands the range of target metals for foam separation and offers a green alternative to solvent extraction, though further development is needed for surfactant properties and operational conditions.
研究不足
The study encountered issues such as foam instability with sole anionic surfactant use, necessitating nonionic co-surfactants. Unfavorable phenomena included voids in foam bed, intermittence, scum formation, and opaque foamate interfering with ICP-AES measurements. The mechanism of surfactant-metal interaction at air-liquid interface may differ from liquid-liquid extraction, requiring further investigation. Operational parameters like flow rates and column dimensions need optimization for broader applicability.
1：Experimental Design and Method Selection:
The study employed continuous counter-current foam separation (CCFS) and conventional batch foam separation (CON mode) to evaluate surfactant combinations for selective indium recovery. The rationale was to enhance recovery and selectivity by injecting metal and surfactant solutions into a rising foam bed, leveraging chromatographic behavior. Theoretical models involved surfactant-metal interactions similar to solvent extraction processes.
2：Sample Selection and Data Sources:
Metal solutions were prepared using standard solutions for atomic absorption spectrometry, containing In(III), Cu(II), Zn(II), and in some cases Fe(III). Surfactants were commercial products from various suppliers, selected based on their structural similarity to phosphoric acid extractants like D2EHPA.
3：List of Experimental Equipment and Materials:
Equipment included glass bubble columns with sintered glass filters, peristaltic pumps, magnetic stirrers, a pH electrode (ToupH 9618-10D, HORIBA), and an inductively coupled plasma atomic emission spectrometer (ICP-AES, SPS3500, SII Nano Technology Inc.). Materials included anionic surfactants (e.g., A219B, A215C), nonionic co-surfactants (e.g., POOE20), metal standard solutions, sulfuric acid, sodium hydroxide, and ascorbic acid.
4：Experimental Procedures and Operational Workflow:
In CON mode, batch experiments were conducted with a bulk solution in a glass column, introducing air through a distributor. Foam was collected and analyzed. In CCFS mode, metal and surfactant solutions were injected into the foam bed at specific points, with continuous operation. Samples were taken at equilibrium, and metal concentrations were measured using ICP-AES after dilution. pH was monitored, and any scum or precipitates were handled with acid washing.
5：Data Analysis Methods:
Percent recovery (Rmi), separation factor (Spmi), and enrichment ratio (En) were calculated using defined equations. Statistical analysis involved error estimation within 10% for recovery data.
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