Structural dependent persulfate activation by coke powder for aniline degradation

Coke powder (CP), the by-product of coal carbonization, its activity of persulfate (PS) activation was systematically investigated. Structural dependent organic pollutant degradation performances and the related mechanisms were discussed in detail. The structural characteristics of CP were studied using X-ray diffraction, Raman, Fourier transform infrared spectra, X-ray photoelectron spectra, and electron paramagnetic resonance (EPR) etc. Characterization results indicate that CP contains ~ 78% carbon and presents highly disordered amorphous structures with abundant oxygenated functional groups (OFGs) and persistent free radicals (PRFs). The catalytic application reveals that CP held excellent activity for PS activation across a wide pH range from 3 -& nbsp;11. In the presence of 0.5 g/L CP, 0.25 mM PS and 0.021 mM aniline (pH 7 & PLUSMN; 0.2), > 99% aniline was degraded within 40 min. Under the interference of inorganic anions (Cl-, HCO3-& nbsp;and SO42-), 98% aniline degradation efficiency still could be achieved. Meanwhile, quenching tests and EPR demonstrated that the superoxide anion radical (O-2(& BULL;-)) was responsible for aniline degradation in CP/PS system, and its generation was independent of dissolved oxygen. The outstanding performance of aniline degradation and ROS generation were attributed to the existence of PRFs, sp2-hybridized carbon, OFGs and defects on CP inducing O-O bonding homolytic cleavage of PS into sulfate radicals. Besides, the OFGs including C-OH and -COOH as electron donors facilitated PS decomposition to generate O-2(& BULL;-). The findings imply that CP is an excellent PS activator, and clarify the development of remediation materials by using by-products of coking process for wastewater treatment.

Automated summary

This study systematically investigated the activation performance of coke powder (CP) towards persulfate (PS) and discussed its mechanism for organic pollutant degradation. The results show that CP has highly disordered amorphous structures with abundant oxygenated functional groups (OFGs) and persistent free radicals (PRFs), which contribute to the excellent activity of CP for PS activation. The study also reveals that superoxide anion radical (O-2•) is responsible for the degradation of organic pollutants in the CP/PS system, and its generation is independent of dissolved oxygen. These findings provide important insights for the development of remediation materials using by-products of the coking process for wastewater treatment.