Comparison between sinusoidal AC coagulation and conventional DC coagulation in removing Cu2+ from printed circuit board wastewater.

A new Electrocoagulation (EC) technique, sinusoidal AC coagulation (SACC), is creatively put forward for Cu2+ removal in the wastewater from the printed circuit board (PCB) production in this paper. The removal efficiency of Cu2+ from PCB wastewater and energy consumption are compared by SACC and conventional direct current coagulation (DCC). The optimal process parameters were established through analysis of response surface methodology (RSM). The coagulations containing Cu2+ was characterized by SEM, EDS, TEM，BET, XRD and FTIR. The nano-ferrum collosol, mainly composed of goethite (α-FeOOH) and magnetite (γ-Fe2O3), absorbs the Cu2+ and coagulates to remove Cu2+. The results show that the removal rates of Cu2+ by SACC and DCC are 99.86％ and 98.21％, respectively, and the energy consumption is 2.76 × 10-2 kWh⋅m-3 for SACC and 4.42 × 10-2 kWh⋅m-3 for DCC under the optimal process conditions of c0 (Cu2+) = 41.99 mg⋅dm-3, pH = 7.14, j = 0.293 A⋅m-2, t = 16.7 min. The pilot tests indicate that the SACC technique is feasible in industrial application. Cu2+ removal were completed through electrodeposition of Cu2+ on iron electrode, the deposition of Cu(OH)2 and the adsorption of Cu2+ by ferrum collosol. The adsorption follows the pseudo-second order kinetics model well. The maximum saturated adsorption capacity (qmax) of Cu2+ on ferrum collosol produced by SACC is larger than that by DCC. The adsorption of Cu2+ on the ferrum collosol prepared by SACC and DCC are in accordance with Langmuir's adsorption isotherms. The novel SACC technique is a promising technique for the highly-efficient treatment of Cu2+ from PCB wastewater.