In electroplating sludge, iron (Fe) and aluminum (Al) are common impurities that need to be separated before recycling valuable heavy metals. However, the traditional Fe/Al separation process often leads to significant losses of heavy metals. To address this issue, a new approach was developed to sequentially separate Fe/Al and recycle chromium (Cr) and nickel (Ni) from real electroplating sludge. The sludge contained 4.5% Cr, 1.2% Al, 1.1% Ni, and 14.6% Fe. Initially, the sludge was completely dissolved in a mixture of hydrochloric and nitric acids. The resulting acid solution was then heated to 160 °C for 10 h with the addition of saccharose. This hydrothermal treatment led to the hydrolysis and crystallization of 98.3% of Fe, 31.8% of Cr, 1.1% of Al, and 4.9% of Ni, forming akaganeite-bearing particles. It was observed that the excessive amount of saccharose also improved the removal of Cr, Al, and Ni, but decreased the removal of Fe. After the hydrothermal treatment, the remaining supernatant was adjusted to different pH levels (1.9, 2.9, and 4.5, respectively), and then Al, Cr, and Ni were stepwise extracted using di-(2-ethylhexyl) phosphate acid (P204). The recycling efficiencies achieved were 97.4% for Al, 61.2% for Cr, and 89.3% for Ni. This approach provides a promising method for the stepwise separation of Fe/Al and the recycling of heavy metals from electroplating sludge.

中文翻译：

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通过铁/铬共结晶和逐步萃取路线将真实混合电镀污泥近乎完全回收为有价金属

在电镀污泥中，铁 (Fe) 和铝 (Al) 是常见的杂质，在回收有价值的重金属之前需要进行分离。然而，传统的铁铝分离工艺往往会导致重金属的大量损失。为了解决这个问题，开发了一种新方法，从真实的电镀污泥中顺序分离 Fe/Al 并回收铬 (Cr) 和镍 (Ni)。污泥含有4.5％Cr、1.2％Al、1.1％Ni和14.6％Fe。最初，污泥完全溶解在盐酸和硝酸的混合物中。然后将所得酸溶液加热至160℃并保持10小时，同时添加蔗糖。该水热处理导致98.3%的Fe、31.8%的Cr、1.1%的Al和4.9%的Ni水解和结晶，形成含有赤铜矿的颗粒。结果发现，过量的蔗糖还提高了 Cr、Al 和 Ni 的去除率，但降低了 Fe 的去除率。水热处理后，将剩余的上清液调节至不同的pH水平（分别为1.9、2.9和4.5），然后使用磷酸二（2-乙基己基）酸（P2O4）逐步萃取Al、Cr和Ni。 Al、Cr 和 Ni 的回收效率分别为 97.4%、61.2% 和 89.3%。该方法为逐步分离Fe/Al和从电镀污泥中回收重金属提供了一种有前景的方法。