Graphene-like carbon sheet-supported nZVI for efficient atrazine oxidation degradation by persulfate activation

Developing excellent carrier materials for supporting metal-based catalysts is challenging. Herein, a graphene-like carbon sheet (CS) was fabricated from a mixture of corn straw and potassium oxalate (K2C2O4) via a simple one-pot approach. The as-obtained sample possesses a 2D lamellar structure similar to graphene, which improves the specific surface area of the biochar. CS-supported nanoscale zero-valent iron (nZVI) composites (nZVI@CS) were designed to enhance atrazine removal by persulfate (PS) activation. The removal efficiencies of nZVI@CS-800 were higher than that of nZVI-PS, implying that the synergy between CS and nZVI was achieved and promoted the removal efficiency of atrazine. CS facilitates the dispersion of nZVI due to its vast SSA, which could prevent nZVI particles from self-aggregation. Simultaneously, the degradation may be by preferentially degrading the atrazine adsorbed on catalyst to promote adsorption. SO4 center dot- plays a more important role in the oxidative degradation of atrazine. CS can directly activate PS to generate SO4 center dot-, and as an electron shuttle, it can promote the conversion of Fe3+ to Fe2+ and improve the activity of the catalyst. The apparent mineralization rate of atrazine after reaction for 60 min is 38.65%, and degradation pathways include dealkylation, alkyl oxidation and dichlorination. Oxidative degradation of atrazine is favored at high temperature or low pH, while it is inhibited when the amount of PS or catalyst becomes excessive. And it may be impacted by organic compounds or anions in the environment. This study is of great significance for the practical application of nZVI@CS for in situ organic pollution remediation.