Sequential recovery of Cu(II), Cr(III), and Zn(II) from electroplating sludge leaching solution by an on-line biosorption method with dosage controlling

Hydrometallurgy leaching is a common method used to recycle heavy metals from electroplating sludge, but the subsequent separation of heavy metals from the complex leaching solution is difficult. In this study, Cu(II), Zn(II), and Cr(III) were sequentially recycled from electroplating sludge by an on-line biosorption method with dosage controlling. The results showed that the three metals mainly existed in their labile forms and could be leached by HNO3. A series of amine-modified bagasse biosorbents were prepared, and diethylenetriamine-modified sorbent was chosen and fixed in a column to remove heavy metals from the leaching solution. Sorbent dosage experiments showed Cu(II) was recycled exclusively at a dosage of 1.5 g/L, while Zn(II) and Cr(III) were recycled simultaneously at a dosage of 3.8 g/L when treating 800 mL of a leaching agent containing 13.4, 9.9, and 7.1 mg/L of Cu, Zn, and Cr. A linear relationship between the dosage and amount of adsorbed metal ions was obtained. The XPS results illustrated that the column had an adsorption affinity order of Cu(II)>Zn(II), Cr(III)≫Ca(II), Mg(II). Cu(II) was enriched in the foot layer, and Zn(II) and Cr(III) were enriched in the middle layer of the column, while co-ions could not be absorbed. According to these results, Cu(II), Zn(II), and Cr(III) could be sequentially recycled by using these columns in-series.