Enhanced Degradation of Smx in Water by Biochar Loading and Multiple Free and Non-Free Radicals Cooperating in the Fe7s8@Bc/Ps System

Abstract

The excessive consumption of sulfamethoxazole (SMX), an antibiotic pharmaceutical, presents a substantial environmental hazard. Biochar (BC) showed good results for the adsorption of SMX. However, BC alone had limited adsorption capacity, and the adsorbed pollutant was not completely destroyed allowing it to contaminate the environment. Therefore, the present study involved the loading of Fe7S8 materials onto BC to promote efficiency of electron transfer, enhance the activation of persulfate, and improve adsorption and degradation of SMX. The synthesis of Fe7S8@BC was conducted using a one-pot approach, wherein the mass ratio of Fe7S8 to BC was systematically adjusted to determine the best Fe7S8@BC catalytic efficiency. The persulfate (PS) activated by Fe7S8@BC, loaded with a mass ratio of 1:1, exhibited the highest efficacy in the removal of SMX, achieving a removal efficiency of 92.5%. Four free and non-free radicals (·OH, SO4·-, 1O2, and Fe(IV)) were identified during the PS activation process. These reactive species played a major role in the removal of SMX, and their removal contribution varied with time. The C-O-Fe in Fe7S8@BC, which may build the structure of the primary battery, contributed significantly to the enhanced destruction of SMX. The toxicity prediction results indicated that the toxicity of transformation byproducts was greatly reduced. Hence, our investigation explored the mechanism by which Fe7S8@BC activates PS in order to generate innovative concepts for the development of a cutting-edge and effective method for removing and remediating SMX.

Keywords: Sulfamethoxazole, Fe7S8@BC, Persulfate, free radicals, Fe(IV), Toxicity prediction