Enhancement of dye waste treatment using Fenton's reagent and adsorbents (natural bentonite, surfactant modified bentonite and activated carbon)

The effectiveness of removing colour and chemical oxygen demand (COD) by using Fenton's process and adsorbents (natural bentonite (NB), anionic surfactant modified bentonite (ASMB), cationic surfactant modified bentonite (CSMB) and granular activated carbon (GAC)) in dye wastewater were investigated. The effect of various factors such as dosage, pH, contact time and concentration were taken under consideration in order to get the optimum performances. Based on the results obtained, the optimum dosage obtained were 0.6 g (NB), 0.3 g (ASMB), 0.4 g (CSMB) and 3.0 g (GAC). While the optimum pH was achieved at pH 3, 4, 6 and 8 for ASMB, NB, CSMB and GAC, respectively. Besides, the optimum contact time was 20 min for NB and ASMB, 15 min for CSMB and 40 min for GAC. Meanwhile, the optimum removal was obtained at dye concentration of 150 ppm (GAC), 250 ppm (NB) and 200 ppm (ASMB and CSMB). The best removal efficiencies were the combination treatments of NB/ASMB/CSMB, Fenton's and GAC (Type II) compared to NB/ASMB/CSMB and GAC (Type I) with the removal of 93.4% - 99.4% for colour and 84.1% - 98.0% for COD. Moreover, the Langmuir isotherm model was fitted well with the experimental data with the R² values for colour 0.2295–0.9938 and COD 0.122–0.5024 compared to the Freundlich isotherm model with the R² values 7x10⁻⁵–0.7043 for colour and 0.0691–0.5718 for COD.