Hydrometallurgical removal of heavy metals (like chromium, iron, and zinc) from an industrial effluent, and their valorization into less-toxic species has been studied. At first, the solvent extraction of Cr(VI) was investigated with tri-butyl phosphate (TBP) to separate this carcinogenic metal from an electroplating effluent containing 3.43 g·L⁻¹ Cr, 1.3 g·L⁻¹ Zn, 0.41 g·L⁻¹ Fe, and 1.23 mol·L⁻¹ free acid of chloride medium. The study based on parametric variation revealed the spontaneity in adduct formation (HCrO₃Cl·2TBP) into organic phase through the exothermic extraction process (ΔH°, −18.8 kJ·mol⁻¹). The extracted species of Cr(VI) was efficiently stripped (∼99%) as less-toxin Cr(III) by 30 min of contact with 2.0 mol·L⁻¹ ascorbic acid solution. Thereafter, the hydrolytic precipitation of Cr(III) from stripped solution at pH ∼9.0, and Fe(III) from raffinate at pH 3.5 under continuous air-flow could yield the precipitates of Cr(OH)₃ and FeOOH·2H₂O, respectively. From the Fe-removed solution, a 5% stoichiometric excess of oxalic acid could effectively precipitate >99.8% zinc in 30 min at 50 °C.

人们已经研究了从工业废水中湿法冶金去除重金属（如铬、铁和锌），并将其转化为毒性较小的物质。首先，研究了用磷酸三丁酯（TBP）溶剂萃取Cr（VI），从含有3.43 g·L ^-1 Cr、1.3 g·L ^-1 Zn、0.41 g·的电镀废水中分离出这种致癌金属。 L ^-1 Fe，氯化物介质的游离酸1.23 mol·L ^-1 。基于参数变化的研究揭示了通过放热萃取过程在有机相中自发形成加合物(HCrO _{3 Cl·2TBP) (Δ} H °, -18.8 kJ·mol ^-1 )。通过与2.0 mol·L ^-1抗坏血酸溶液接触30分钟，提取的Cr(VI)物质被有效地剥离(∼99%)为毒性较小的Cr(III) 。此后，在连续气流下，汽提液中的 Cr(III) 和 pH 3.5 的萃余液中的 Fe(III) 在 pH ～ 9.0 下水解沉淀，可产生 Cr(OH) ₃和 FeOOH·2H ₂ O 沉淀，分别。从除铁溶液中，化学计量过量 5% 的草酸可以在 50 °C 下 30 分钟内有效沉淀 >99.8% 的锌。