Column removal of Ni(II) from synthetic electroplating waste water using a strong-acid resin

Ion exchange is widely used for the recovery and removal of metals from waste streams in chemical process industries. The removal of Ni(II) from synthetic electroplating waste water using a strong-acid resin in fixed beds was investigated. Besides NiSO4, the water contained NH4Cl and anionic ligands NaH2PO4 and citrate. Batch studies showed that the exchange isotherms were well fitted by the Langmuir equation. Column experiments were performed under different pH values (0.5–5.0), metal concentrations (5.1–11.9 mol/m3), volumetric flow rates (5–12 cm3/min), and bed volumes (3.7–9.8 cm3). The Thomas model that consists of two parameters was applied to describe the breakthrough curves. It was shown that the calculated breakthrough curves agreed well with the measured ones (standard deviation 6%), except the curves before break point obtained at pH > 3.0. The non-zero Ni(II) concentration in the effluent at the early stage of the whole process was ascribable to the presence of anionic ligands. A chemical model that considers possible aqueous complexation reactions was proposed to explain such breakthrough characteristics.