Waste tire upcycling for the efficient electrogeneration of H₂O₂ in advanced degradation of the antibiotic tinidazole by electro-Fenton process

Abstract

The electrochemical production of H2O2 using small- and medium-size modular devices has emerged as aninteresting approach for water treatment. In this work, waste tire-derived carbon (WTC) has been innovativelyemployed as a cheap and recycled electroactive material to manufacture a gas-diffusion cathode. It was foundthat acidification with HNO3 significantly enhanced the H2O2 production, attaining a concentration of up to1161 mg/L with a current efficiency around 40 %–60 %. These results were superior to those obtained bytreating the WTC with H2SO4 or KOH, being also better than the values reached with reported carbons. Liner andcyclic voltammetries informed about the oxygen reduction reaction profiles; transmission electron microscopyrevealed the morphological features of the synthesized carbons, whereas other properties were obtained byBrunauer-Emmett-Teller analysis, Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy.The cathode was further employed to degrade tinidazole (TNZ), a typical nitroimidazole antibiotic, inwater by electro-Fenton at pH 3.0, producing more than 10 mM H2O2. The effect of solution pH, Fe2+ dosage andinitial TNZ concentration was investigated. Under optimal conditions (0.5 mM Fe2+ and 20 mA/cm2), thetreatment of solutions containing 20 mg/L TNZ at pH 3.0 yielded a pseudo-first-order constant (k1) of 0.449min-1. Besides, the degradation pathways were proposed according to the 7 identified transformation products.This study demonstrates that waste tires can become a source of inexpensive carbon able to catalyze the in-situH2O2 synthesis for water decontamination, in excellent agreement with new policies on circular economy.