A Fenton-based approach at neutral and un-conditioned pH for recalcitrant COD removal in tannery wastewater: Experimental test and sludge characterization

Erika Pasciucco; Francesco Pasciucco; Renato Iannelli; Isabella Pecorini

doi:10.1016/j.scitotenv.2024.172070

A Fenton-based approach at neutral and un-conditioned pH for recalcitrant COD removal in tannery wastewater: Experimental test and sludge characterization

Sci Total Environ. 2024 May 20:926:172070. doi: 10.1016/j.scitotenv.2024.172070. Epub 2024 Mar 29.

Authors

Erika Pasciucco¹, Francesco Pasciucco², Renato Iannelli³, Isabella Pecorini⁴

Affiliations

¹ Department of Energy, Systems, Territory and Construction Engineering, University of Pisa, Via C.F. Gabba 22, Pisa, Tuscany 56122, Italy. Electronic address: erika.pasciucco@phd.unipi.it.
² Department of Energy, Systems, Territory and Construction Engineering, University of Pisa, Via C.F. Gabba 22, Pisa, Tuscany 56122, Italy. Electronic address: francesco.pasciucco@phd.unipi.it.
³ Department of Energy, Systems, Territory and Construction Engineering, University of Pisa, Via C.F. Gabba 22, Pisa, Tuscany 56122, Italy. Electronic address: renato.iannelli@unipi.it.
⁴ Department of Energy, Systems, Territory and Construction Engineering, University of Pisa, Via C.F. Gabba 22, Pisa, Tuscany 56122, Italy. Electronic address: isabella.pecorini@unipi.it.

PMID: 38554952
DOI: 10.1016/j.scitotenv.2024.172070

Abstract

The combination of raw animal skin manufacturing processes involves the use of large amounts of chemicals, resulting in the generation of complex and highly polluted tannery wastewater. In this context, the high concentration of chloride in tannery wastewater represents a crucial bottleneck. Indeed, sodium chloride, commonly used in tannery industry to prevent skin rot, increases the concentration of chlorides up to 50 %. At the same time, most of the advanced oxidation processes usually employed in tannery wastewater treatment to remove recalcitrant COD involve the use of conditioning agents, thus increasing the overall concentration of chlorides in the treated effluent. The aim of this study was to evaluate the electrochemical peroxidation process (ECP) efficiency in the treatment of tannery wastewater without changing pH, to improve Fenton technology by avoiding the use of chemicals. The influence of different electric currents on COD and color removal was investigated. The characterization of the produced sludge was conducted through FTIR, SEM and XRD analysis, exploring the morphology and composition of precipitate, depending on the applied current. Although an electrical current of 750 mA yields the highest COD and color removal efficiency (69.7 % and 97.8 %, respectively), 500 mA can be considered the best compromise because of energy consumptions. Iron oxides and hydroxides were generated during the ECP process, playing the role of coagulants through the absorption of organic and inorganic contaminants. The consumption of energy increased as a function of time and applied current; however, cost analysis showed that the electrodes contributed the most to the total cost of the process. In authors' knowledge, the application of ECP process as a tertiary treatment for the removal of recalcitrant COD in tannery wastewater represents a novelty in the literature and the results obtained can be considered as the basis for scaling up the process in future research.

Keywords: Advanced oxidation process; Electrochemical process; Recalcitrant COD; Tannery wastewater treatment; iron sludge reuse.