As environmental regulations are becoming stricter, new techniques must be developed for the removal of trace concentrations of heavy metals from mineral processing effluents. Foam separation techniques are an interesting alternative to more conventional processes such as ion exchange because of their efficiency to treat dilute aqueous streams. In this paper, the simultaneous removal of Cd²⁺, Mn²⁺, and Zn²⁺ from dilute aqueous solutions was investigated by using sodium dodecyl sulfate as collector and triethylenetetramine as auxiliary ligand via a series of batch-mode flotation experiments. Experimental results showed that Cd²⁺, Mn²⁺, and Zn²⁺ can be completely removed in one step under the following conditions: pH 9.50, flotation time = 120 min, auxiliary concentration 0.1 mmol L⁻¹, collector-to-metals molar ratio 2:1, ethanol concentration 0.5% (v/v), and a nitrogen gas flowrate set at 25 mL min⁻¹. An excess in auxiliary ligand concentration yielded to low removal efficiency. The modeled speciation of the examined system suggested that the metals are separated from the bulk solution to the foam phase via a combination of ion flotation and precipitate flotation.

Graphical Abstract

中文翻译：

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泡沫分离去除稀水溶液中的镉，锌和锰

随着环境法规越来越严格，必须开发新技术以去除矿物加工废水中的痕量重金属。泡沫分离技术是更常规方法（例如离子交换）的有趣替代方法，因为它们能有效地处理稀水流。本文通过一系列分批浮选实验，以十二烷基硫酸钠为捕收剂，三亚乙基四胺为辅助配体，研究了从稀水溶液中同时去除Cd 2 ⁺，Mn ²⁺和Zn ^2+的方法。实验结果表明，Cd 2 ⁺，Mn ²⁺和Zn ²⁺可在以下条件下一步一步完全除去：pH 9.50，浮选时间= 120分钟，辅助浓度0.1 mmol L ^-1，捕集剂与金属的摩尔比2：1，乙醇浓度0.5％（v / v），氮气流量设置为25 mL min ^-1。辅助配体浓度过高导致去除效率低。所检查系统的模型形态表明，通过离子浮选和沉淀物浮选的组合将金属从本体溶液分离到泡沫相。

图形概要