Feasibility test for waste-reclaimed material to remove Cu2+ and Zn2+: Kinetics and applications to treat a real plating wastewater

Applicability of waste-reclaimed material (WR) to remove heavy metals (Cu2+ and Zn2+) in a plating wastewater was investigated. The mass (mg) of both Cu2+ and Zn2+ removed from solution was linearly increased when the initial concentrations increased from 10 to 100 mg/L. Experimental data was well predicted by both Langmuir and Freundlich models. In the Langmuir model, the values of RL (a dimensionless constant separation factor) indicated that adsorption of both Cu2+ and Zn2+ on WR were favorable (i.e. RL for Cu2+ were 0.337–0.048 and RL for Zn2+ were 0.775–0.256). Kinetically, adsorption of both Cu2+ and Zn2+ was predicted by pseudo-second order model. The highest qe of Cu2+ and Zn2+ were 1.6 × 10−1 and 8.1 × 10−2 mg/g, respectively. Moreover, the initial adsorption rate, h (k2qe2), was increased when initial concentrations of metal ions increased. The effect of pH on the removal of Cu2+ and Zn2+ revealed that some degrees of Cu2+ and Zn2+ were removed at the acidic condition. Moreover, all Cu2+ was removed at pH 7, while Zn2+ was completely removed at pH 9. Therefore, those results indicated that the surface characteristics, specifically both the surface charge and chemical compositions, could make WR a potential adsorbent. The use of WR showed that removal of metal ions satisfy the regulatory requirements (i.e. under 3.0 mg/L of Cu2+ and 5.0 mg/L of Zn2+) in Korea when experiments using large-scale reactors were conducted 20 times in plating wastewater.