Iron-loaded leonardite powder for Fenton oxidation of Reactive Red 180 dye removal

Fenton oxidation is an effective and valuable method for wastewater treatment. To inhibit environmental impacts and increase overall reaction efficiencies, it is important to develop advanced catalysts. This paper illustrates an experimental study on the elimination of RR180 dye from synthetic aqueous solutions with raw leonardite and different iron-loaded leonardite powders, Fe(0)-loaded leonardite, and Fe(II)-loaded leonardite. The effect of solution pH (2.0-6.0), catalyst amount (0.10-1.5 g/L), H₂O₂ concentration (10-50 µL/L), and dye concentration (10-30 ppm) was tested to achieve maximum color removal efficiency using the three catalysts. At pH = 2, color removal efficiencies were higher and more suitable. Initial experiments showed the advantage of using Fe(II)-loaded leonardite on using Fe(0)-loaded leonardite. Fe(II)-loaded leonardite catalyst was the most efficient in RR180 color removal compared to the other tested reagents. Color removal in function of solution pH did not decrease much when Fe(II)-loaded leonardite was used (100 to 96%) when pH was increased from 2.0 to 6.0. In the other hand, dye removal has been significantly affected in the case of using raw leonardite, Fe(0)-loaded leonardite (93 to 0%), and (100 to 13%) in the same pH range, respectively. At optimum experimental conditions, catalyst amount: 0.75 g/L for Fe(II) and Fe(0)-loaded leonardite and 1.5 g/L for raw leonardite; dye concentration: 10 ppm; solution pH: 2.0; H₂O₂ concentration: 50 µL/L; volume: 100 mL and reaction time: 60 min, RR180 dye removal efficiencies were 91%, 100%, and 100% by raw leonardite, Fe(0)-loaded leonardite and Fe(II)-loaded leonardite, respectively. The stability and reusability of the tested catalyst was investigated up to ten cycles. The experimental results revealed that both Fe(0)-loaded leonardite and Fe(II)-loaded leonardite can be used in Fenton reaction up to four cycles without decreasing their efficiency in RR180 color removal. The characterization of the catalysts was established using scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). The synthesized catalyst can be used at large scale in any textile industry to effectively remove dyes resulting in high elimination rates at the optimal determined and studied conditions.