Efficacy and cytotoxicity of engineered ferromanganese-bearing sludge-derived biochar for percarbonate-induced phthalate ester degradation

Phthalate esters (PAEs) are a group of ubiquitous organic environmental contaminants. Engineered ferromanganese-bearing sludge-derived biochar (SDB), synthesized using one-step pyrolysis in the temperature range between 300 and 900 degrees C, was used to enable Fenton-like processes that decontaminated PAE-laden sediments. SDB was thoroughly characterized using scanning electron microscopy-energy-dispersive spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller surface area, thermogravimetric analysis, Raman spectroscopy, Fourier-transform infrared spectroscopy, electron paramagnetic resonance, X-ray photoelectron spectroscopy, and fluorescence excitation-emission matrix spectroscopy coupled with parallel factor analysis. The maximum PAE degradation was remarkable at 90% in 12 h at pH 6.0 in the presence of 1.7 g L-1 of SDB 900. The highly-effective PAE degradation was mainly attributed to the synergism between FeOx and MnOx, which strengthened the activation of percarbonate (PC) via electron transfer, hydroxy addition, and hydrogen abstraction through radical (HO center dot) and nonradical (1O2) oxidation mechanisms, thereby facilitating PAE catalytic degradation over SDB in real sediments, which clearly proved the efficacy of ferromanganese-bearing SDB and PC for the remediation of contaminated sediments. The cytotoxicity exhibited by human skin keratinocyte cells exposure to high SDB concentration (100-400 mu g mL-1) for 24-48 h was low indicating insignificant cellular toxicity and oxidative damages. This study provides a new strategy for freshwater sludge treatment and reutilization, which enables a water-cycle-based circular economy and waste-to-resource recycling.

Automated summary

This study utilized engineered ferromanganese-bearing sludge-derived biochar to decontaminate PAE-laden sediments, showing remarkable degradation efficiency and low cytotoxicity, providing a new strategy for freshwater sludge treatment and reutilization.