Ball-milled MoS₂/biochar as peroxymonosulfate activator efficiently removes tetracycline: Multiple active sites-triggered radical/non-radical pathways

In spite of biochar (BC) was feasible on using to activate peroxymonosulfate (PMS) to degrade organic pollutant, its catalytic performance must be advanced further. In this work, MoS2/BC composite fabricated through onestep solvent-free ball milling procedure was utilized as PMS activator for efficient tetracycline (TC) degradation and the activated mechanism of PMS was proposed. The optimized MoS2/BC-0.5-4 with mass ratio of MoS2 to BC of 0.5 and ball milling time of 4 h exhibited the highest degradation efficiency of TC at the present of PMS which significantly surpassed pristine BC and MoS2. The results of XRD, FT-IR and Raman tests implied the composite was synthesized successfully. The results of hydrochemical experiments demonstrated the composite possessed the excellent removal efficiency in wide pH range under the low dosages of catalysts (50 mg/L) and oxidants (0.1 mM). EPR characterization analysis indicated (OH)-O-center dot, SO4 center dot-, O-2(center dot-), O-1(2) and electron transfer presented in MoS2/BC-PMS system, demonstrating that TC degradation was accomplished through both radical and non radical paths. Among those, (OH)-O-center dot played the dominant role in MoS2/BC-PMS system, but the part played by O-1(2) was larger in BC-PMS system. In addition, the introduction of Mo(IV) and exposed carboxyl group (-COOH) by ball milling provides more important active sites, enhancing electron transfer effect and generating more reactive oxygen species (ROSs) resulted in increased PMS activation. Findings from this study indicated the ball milled MoS2/BC has great prospects in the removal of antibiotics due to its remarkable efficiency, affordable, environmental-friendly, and straightforward synthesis.