Superhigh adsorption of nickel from electroplating wastewater by raw and calcined electroplating sludge waste

Both the raw electroplating sludge (RES) waste and the calcined electroplating sludge (CES) were utilized to adsorb nickel from the real electroplating wastewater. The CES was obtained via calcination treatment at 500 °C, and the CES and RES were characterized by X-ray fluorescence (XRF), Fourier transform infrared spectrometer (FT-IR), X-ray powder diffraction (XRD). Adsorption isotherm results showed that the maximum adsorption capacities of Ni2+ on the CES and RES were 163.6 and 210.9 mg/g according to the Langmuir fitting, respectively. In the real nickel-containing wastewater treatment, the RES exhibited much higher adsorption capacity for Ni2+ than commonly used adsorbents including coal-based activated carbon (CAC), strong acid cation-exchange resin (D001), weak acid cation-exchange resin (D113) and amino carboxylic acid chelating resin (D463). The adsorption mechanisms of Ni2+ on the RES and CES mainly included ion exchange and surface complexation. The large amount of Ca2+ in the adsorbents played an important role in the adsorption of Ni2+ via cation exchange, and the hydroxyl and carboxyl groups on the adsorbent were also responsible for Ni2+ adsorption. Therefore, the electroplating sludge waste is an efficient adsorbent for Ni2+ removal from high concentrations of nickel-containing electroplating wastewater. This study provides a new method for the utilization of electroplating sludge as efficient adsorbents before being treated as hazardous waste, showing the feasible concept of disposal waste with waste.