Photocatalytic oxidation of 2,4-D by g-C3N4-CuFe2O4 catalyst: statistical modeling and optimization via Box–Behnken design

Abstract

Response surface methodology (RSM) is an outstanding tool for optimizing pollutant photodegradation processes that involve many complex operational factors. This study aims to model and optimize the photodegradation parameters of 2,4-Dichlorophenoxyacetic acid (2,4-D) using a Z-scheme g-C₃N₄-CuFe₂O₄ catalyst, with a Box–Behnken design (BBD) as the RSM statistical model. The effects of independent variables such as the g-C₃N₄-CuFe₂O₄ catalyst with different loadings of g-C₃N₄ (X₁), reaction time (X₂), initial 2,4-D concentration (X₃), catalyst dosage (X₄), and solution pH (X₅) on 2,4-D photodegradation were studied. All independent variables tested during 2,4-D photodegradation were found to be statistically significant based on the ANOVA results. The results show that the amount of g-C₃N₄ introduced into the CuFe₂O₄ structure had the most significant influence among the variables on 2,4-D photodegradation. The photodegradation efficiency predicted by the BBD model was 98.21 % under optimal operating conditions, including a solution pH of 5.0 using 1000 mg/L of g-C₃N₄(2 %)-CuFe₂O₄ at an initial 2,4-D concentration of 20 mg/L. The actual 2,4-D photodegradation efficiency was close to the predicted value (97.78 ± 0.80 %), suggesting that BBD can be effectively used to optimize 2,4-D photodegradation using a Z-scheme g-C₃N₄(2 %)-CuFe₂O₄ catalyst under visible light. The enhanced photodegradation efficiency of 2,4-D is mainly due to the effective separation of photoinduced electron–hole pairs and the formation of highly active species (O₂^•− and OH^•) in the Z-scheme g-C₃N₄-CuFe₂O₄ heterojunction system. Furthermore, g-C₃N₄(2 %)-CuFe₂O₄ is durable and easily recycled and reused many times in succession, showing great application potential in the removal of toxic pollutants through the efficient use of solar energy.