Electro-Fenton process for implementation of acid black liquor waste treatment

In this work, an eco-friendly solution for the remediation of wastewater generated in the lignin recovery process from eco-industrial paper mill has been proposed in their way towards a more circular economy strategy. Thus, the application of the electro-Fenton process for the degradation of the non-recovered lignin and other organic compounds form a scarcely studied acid black liquor waste (ABLW) was successfully performed. This treatment was able to operate in a range of COD loads (0.5–19.5 mg O2·L–1) showing high degradation values of the ABLW determined by the abatement of color, total phenolic content and COD. Then, the optimization of the working conditions for the design of a sustainable treatment system with optimum efficiency was carried out using a response surface methodology. The experiment carried out in the calculated optimal conditions for the electro-Fenton degradation process (current intensity 132.5 mA, catalyst dosage of 0.10 mM, and temperature 40 °C) showed a COD removal of 74.82% and current efficiency 77.79%, close to the theoretical value predicted by the model 73.12% and 77.06%, respectively. In addition, the identification of the final products permitted to confirm the mineralization efficiency.