Removal of Red Ponceau 4R by a Combined Process Coupling Adsorption and Photocatalysis

This investigation explores the elimination of Red Ponceau 4R (RP4R) dye through a synergistic method combining biosorption and photocatalysis. The study utilized fig as a botanical biosorbent within aqueous mediums to evaluate the influence of various factors such as contact duration, pH of the solution, dosage of biosorbent, temperature, and initial concentration of dye on the biosorption capacity. The study identified that the most effective biosorbent concentration was 1 g/L, with an optimal pH of 1.5. The biosorption capacity was found to increase when the concentration of RP4R varied between 15 and 100 mg/L. Equilibrium was reached in 50 minutes, and the adsorption dynamics were well-described by the Langmuir isotherm model, as indicated by a correlation coefficient (R²) of 0.997. The biosorption kinetics adhered to a pseudo-second-order model, achieving an R² of 0.999. Thermodynamic assessments indicated that the process was both spontaneous and absorbed heat. Following this, the residual concentration of RP4R was subjected to photocatalytic degradation using a CuFe2O4/ZnO hetero-system under solar light. The CuFe2O4 spinel was fabricated via a co-precipitation technique. Mott-Schottky analysis (C²-V) revealed p-type conductivity with the conduction band situated at (+1.60 VSCE), which is beneath the potential of the O2/O2•- couple, suggesting that electrons could transform RP4R into radical O2•- with ZnO acting as the facilitator. The photocatalytic degradation reached its maximum with a 30% concentration of CuFe2O4. This degradation process followed first-order kinetics, with a half-life of 56 minutes, and achieved a conversion efficiency of 64% at an initial concentration of 10-4 M.