Green valorization of end-of-life toner powder to iron oxide-nanographene nanohybrid as a recyclable persulfate activator for degrading emerging micropollutants.

The sustainable management of toner waste (T–raw) was performed via carbonization at 500 °C (T-500) and 600 °C (T–600) to produce iron oxide-nanographene nanohybrid (FeO-NG) for activating persulfate (PS) to efficiently degrade dyes (methylene blue, MB), antibiotics (sulfamethazine, SMZ), and pesticides (diazinon, DZN). Morphology, crystallinity, chemical structure, chemical composition, surface area, and pore size distribution of the synthesized materials were investigated using various analyses. High degradation ratios of MB were attained over a wide pH range (2–7), and the optimum operating conditions were determined. The FeO-NG/PS system was tested in different water matrices. MB degradation efficiency dropped from 80.13% to 78.56% after five succeeding experiments, proving the high stability of T–500. Trapping experiments proved the major role of sulfate radicals and the minor contribution of singlet oxygen. The toxicity evaluation of the treated and untreated MB solutions was conducted via measuring the cell viability, showing an increase in cell viability ratio after the degradation of MB. The degradation efficiencies of DZN and SMZ were 97.54% and 83.7%, respectively and the mineralization ratios were 74.08% and 60.37% at initial concentrations of sulfamethazine and diazinon of 50 and 100 mg/L, respectively. The high degradation efficiency of emerging micropollutants as well as the inexpensiveness, and facile synthesis of the catalyst boost the prospect of applying the proposed system on an industrial scale. [Display omitted] • 500 °C carbonization of toner waste yielded a porous and high surface FeO-NG. • FeO-NG can effectively activate persulfate to generate reactive oxygen species. • High degradation and mineralization of target pollutants were achieved. • Sulfate radicals were the dominant reactive species. • The toxicity of methylene blue decreased after the treatment by FeO-NG/PS system. [ABSTRACT FROM AUTHOR]