Electroplating sludge is a hazardous waste produced in large quantities in the electroplating industry during production. It is rich in heavy metal resources and can be recovered as value-added heavy metal products. To recover Zn in electroplating sludge, Fe/Al/Ca impurities were effectively removed as hematite, boehmite, and calcium sulfate, respectively, via a facile hydrothermal method with reduction of nitric acid by addition of glucose. After the sludge was dissolved in nitric acid, the generated solution contained 6.1 g/L of Zn, 2.2 g/L of Fe, 2.5 g/L of Al, and 2.9 g/L of Ca. First, approximately 100% Fe was extracted as hematite nanoparticles containing 94.6 wt% Fe₂O₃ after the solution was treated at 190 °C for 6 h. Second, when the temperature was elevated to 270 °C, nearly 99% Al was isolated as boehmite particles containing 95.2 wt% Al₂O₃. Third, more than 98% Ca was removed as anhydrite, which contained 95.9 wt% CaSO₄, by adding sulfuric acid. During the steps, the total loss of Zn was less than 3%, and 5.75 g/L of residual Zn was recovered as zincite containing 92.2 wt% ZnO by adjusting the pH to 8. The dissolved Fe, Al, and Ca impurities were successfully removed as purified hematite, boehmite, and anhydrite, respectively, through the stepwise separation method by adjusting reaction temperatures and pH. The high content of Zn in the electroplating sludge was finally purified as zincite.

电镀污泥是电镀行业生产过程中大量产生的危险废物。重金属资源丰富，可回收为高附加值的重金属产品。为了回收电镀污泥中的锌，通过添加葡萄糖还原硝酸的简便水热法，分别以赤铁矿、勃姆石和硫酸钙形式有效去除 Fe/Al/Ca 杂质。将污泥溶于硝酸后，生成的溶液中含有 6.1 g/L 的 Zn、2.2 g/L 的 Fe、2.5 g/L 的 Al 和 2.9 g/L 的 Ca。首先，大约 100% 的 Fe 被提取为含有 94.6 wt% Fe ₂ O _{3 的}赤铁矿纳米颗粒溶液在 190°C 下处理 6 小时后。其次，当温度升高到 270 °C 时，将近 99% 的铝被分离为含有 95.2 wt% Al ₂ O _{3 的}勃姆石颗粒。第三，通过加入硫酸，超过 98% 的 Ca 作为硬石膏被去除，其中含有 95.9 wt% 的 CaSO ₄。在这些步骤中，锌的总损失小于 3%，通过调节 pH 至 8，回收了 5.75 g/L 的残留锌，为含有 92.2 wt% ZnO 的锌矿。成功溶解了溶解的 Fe、Al 和 Ca 杂质通过调节反应温度和pH值，通过逐步分离的方法分别去除纯化的赤铁矿、勃姆石和硬石膏。电镀污泥中高含量的锌最终被提纯为红锌矿。