Techno-economic estimation of electroplating wastewater treatment using zero-valent iron nanoparticles: batch...

Electroplating manufacturing processes release industrial effluents that comprise severe levels of heavy metals into the environment. This study investigated the utilization of nanoparticles of zero-valent iron (nZVI) for the treatment of electroplating wastewater industry containing multiple heavy metal ions. In batch experiments using Cu²⁺ as a single solute, the optimum operating condition was pH 7.3, nZVI dosage 1.6 g/L, time 36 min, temperature 30 °C, and agitation speed 180 rpm, achieving almost 100% Cu²⁺ removal efficiency. The adsorption mechanisms were illustrated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) spectrometer. Moreover, continuous-feed experiments were performed to treat real electroplating wastewater industry via adsorption and sedimentation processes. The system attained removal efficiencies of 91.3% total suspended solids (TSS), 68.3% chemical oxygen demand (COD), 94.2% nitrogen (N), 98.5% phosphorus (P), 66.7% Cr⁶⁺, 91.5% Pb²⁺, 83.3% Ag⁺, 80.8% Cu²⁺, 17.4% Ni²⁺, 47.1% Mn²⁺, 54.6% Zn²⁺, 94.7% Fe³⁺, 100.0% Al³⁺, and 42.1% Co²⁺. The removal mechanisms included reduction of Meⁿ⁺ to Me^(n-x)+/Me⁰ by the Fe⁰ core, adsorption to the oxide shell as Me(OH)_x and Me-Fe-OOH, oxidation of Meⁿ⁺ to Me^(n+z)+, specific surface bonding, and sequential steps of electron transfer and precipitation. The total cost, including amortized and operating expenses for scaling up the adsorption system, was 4.45$ per m³ of electroplating wastewater. Graphical abstract.