An efficient method for extracting bismuth (Bi 3+ ) from a hydrochloric acid (HCl) system by cementation with copper (Cu 0 ) powder was proposed in this work. The thermodynamic properties of cementation were investigated via cyclic voltammetry measurement and thermodynamic calculation. Then, the effects of reaction temperature, Cu 0 /Bi 3+ molar ratio, stirring rate, HCl concentration, and competing ions on the cementation efficiency of bismuth were systematically investigated. Results showed that the cementation reaction between bismuth and copper powder was thermodynamically spontaneous. A Bi recovery of 99% could be achieved with copper powder under an optimized cementation condition (6 mol L −1 HCl, 60 °C, Cu 0 /Bi 3+ molar ratio of 4, stirring rate of 500 rpm, and reaction time of 30 min). Kinetics study revealed that Cu 0 -Bi 3+ cementation followed a first-order reaction law in the range of 20 °C–60 °C. The activation energy of bismuth cementation was 8.58 kJ mol −1 . The generated cuprous ions can be recovered as copper sulfides by sulfuration after Bi 3+ was extracted. This finding indicated that Cu 0 powder cementation showed potential for Bi 3+ extraction.
Wenjuan Zhang,Liu Xia,Kashif Mairaj Deen,Edouard Asselin,Baozhong Ma,Chengyan Wang
Cadmium recovery from wastewater is important to prevent water pollution and add value to the circular economy. Cementation is a widely applied method for Cd removal but this process is found less efficient. Herein, a novel electro-assisted cementation process is proposed, which enables effective Cd removal and recovery from Zn processing wastewater. Under optimal conditions, 98.5 % of dissolved Cd was removed and recovered having 94.1 % purity. More importantly, a peculiar Cd reduction on the Zn anode was observed and the mechanism is explained based on the electrochemical test and experimental results. By applying a cell potential of 0.5 V, the negative surface potential of Zn and its localized dissolution facilitated Cd deposition on the Zn anode by suppressing H 2 generation. Moreover, in contrast to the conventional cementation process, the formation of Cd dendritic structures on the Zn anode avoided full surface coverage, thus resulting in high cementation efficiency. In summary, this process presents great potential for the efficient removal of Cd from wastewaters and the findings offer new insights into the enhancement mechanism of electro-assisted cementation.
Cunjun Wang,Yongqiang Chen,Yubo Liu,Baozhong Ma,Chengyan Wang
Recycling cadmium from wastewater not only mitigates environmental risks but also offers economic benefits. However, conventional zinc powder cementation is hindered by excessive zinc consumption and the generation of low-purity cadmium sludge. In this study, we proposed a galvanic cell system composed of a zinc plate coupled with a stainless steel plate, replacing zinc powder as the reductant. Under optimized conditions, the system achieved 99.8 % cadmium removal, with a recovered cadmium purity exceeding 90 %. Mechanistic insights derived from kinetic modeling and electrochemical analysis revealed that cadmium deposition was governed by a mixed control mechanism involving both mass transfer and interfacial reaction. The stainless steel plate provided additional cathodic reduction sites and established a natural potential difference together with the zinc anode. This galvanic interaction promoted active zinc dissolution and facilitated preferential cadmium deposition. Meanwhile, microstructural analysis confirmed the formation of a loose, dendritic cadmium layer, which prevented surface encapsulation and promoted favorable mass transfer conditions for sustained cementation. Compared to traditional zinc powder cementation, this approach eliminates the need for external energy input, reduces zinc consumption, and avoids the generation of hazardous sludge. These findings demonstrate a clean, efficient, and scalable strategy for the removal and recovery of cadmium from wastewater.
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