Biodiesel Waste-Based Additive as an Environmental-Sustainable Approach for Cyanide-Free Zinc Electroplating Process

Biofuel production has increased significantly as a result of the rush to decarbonize fuels, which has led to a notable increase in the amount of glycerol waste generated. The innovation of this study results from incorporating glycerol waste to optimize the zinc electrodeposition process on brass substrates, reducing the need for effluent disposal and promoting the circular economy through the use of this industrial waste, as well as promoting a sustainable and functional alternative in the field of electroplating. The presence of residual glycerol in low concentrations in its composition allowed to carry out the optimization of zinc electrodeposition on brass substrates. To do that, a central composite experimental design was carried out to investigate the effects of the concentration of industrial glycerol waste, time and current on the process, using the cathodic efficiency of the deposit as the variable response. The experiments were conducted using the Hull cell, a scaled-down unit of an industrial electrodeposition system. The results clearly indicate that the estimated model is predictive (R 2 = 0.99045), with the effects of the linear and quadratic terms of current and time, quadratic of the concentration of glycerol waste, and the interactions between current and time being significant. The most effective test showed a cathodic efficiency of about 139.7%, and it evidences that the presence of biodiesel waste favored a more homogeneous electrochemical deposition, as revealed by scanning electron microscopy (SEM) analysis. In addition, corrosion inhibition increased with an increase on the biodiesel waste concentration, achieving 37% when 0.10% v/v biodiesel waste was used. Thus, the use of wastewater from the biodiesel production process was proposed for the first time as an additive in cyanide-free electrolytic baths.