Synergistic effect of Fenton oxidation and adsorption process in treatment of azo printing dye: DSD optimization and reaction mechanism interpretation

ABSTRACT

The main challenges to overcome within the Fenton process are the acidic pH as an optimal reaction condition, sludge formation in neutral pH medium and high toxicity of treated printing wastewater due to the generation of contaminating by-products. This research discusses the catalytic activity of homogeneous (FeSO₄/H₂O₂) and heterogeneous (Fe₂(MoO₄)₃/H₂O₂) Fenton processes in treatment of Yellow azo printing dye in synthetic aqueous solution and real printing effluent, with an integration of adsorption on functionalized biochar synthesized from wild plum kernels. The definitive screening design (DSD), was used to design the experiment. Independent variables were initial dye concentration (20–180 mg L⁻¹), iron concentration (0.75–60 mg L⁻¹), pH (2–10) and hydrogen peroxide concentration (1–11 mM). Higher decolourization efficiency of 79% was obtained within homogeneous Fenton treatment of printing wastewater, in comparison to heterogeneous Fenton treatment (54%), after a reaction time of 60 min. Same trend of mineralization degree was established: COD removal was 59% and 33% for homogeneous and heterogeneous Fenton process, respectively. The application of adsorption treatment has achieved significant advantages in terms of toxicity reduction (95%) and decolourization efficiency (90% of TOC removal and 22% of dye removal) of treated samples, even at neutral pH medium. Degradation mechanisms within Fenton and adsorption processes were proposed based on the qualitative gas chromatography/mass spectrometry analysis, physico-chemical properties of dye degradation products and functionalized biochar. Overall, the homogeneous Fenton/adsorption combined process can be potentially used as a treatment to remove azo dyes from contaminated water.

GRAPHICAL ABSTRACT

KEYWORDS:

• Yellow printing dye
• Fenton treatment
• adsorption process
• biochar
• microwave functionalization

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data are available within this article.

Additional information

Funding

This study was supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia (grant numbers 451-03-68/2022-14/200156, 451-03-68/2022-14/200125).