Treatment of polymer-flooding wastewater by a modified coal fly ash-catalysed Fenton-like process with microwave pre-enhancement: System parameters, kinetics, and proposed mechanism

Raw coal fly ash (RCFA) was modified by H2SO4 impregnation, and the modified RCFA (ACFA) was then used as a Fenton-like catalyst to treat polymer-flooding wastewater (PW) with microwave (MW) pre-enhancement. The characterisation results revealed that H2SO4 impregnation can damage the surface structure of RCFA, increase its specific surface area, and release active sites, thereby improving its catalytic potential. Under optimal experimental conditions (ACFA loading = 20 g/L, H2O2 dosage = 18 mmol/L, pH = 3, MW pre-enhancement duration = 7 min, and formal treatment duration = 50 min), the removal rate of polyacrylamide (PAM) in PW reached 70.3%. The degradation of PAM followed pseudo-first-order kinetics: lnC(0)/C=0.0290.t, and the relationship between the reaction rate constant, H2O2, and ACFA was k(ap,1) = 4355 (A) over cap .e(-4724.8/T)(A) over cap.[ACFA](0.411)(A) over cap.[H2O2](0.947). MW pre-enhancement could remarkably enhance the center dot OH generation, while the generation path of center dot OH could be changed by the leaching behaviour of ACFA.

Automated summary

The modification of raw coal fly ash by H2SO4 impregnation enhances its catalytic potential, while microwave pre-enhancement can significantly increase the generation of center dot OH. Under optimal experimental conditions, ACFA shows good removal efficiency for PAM in PW.