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Magnesium oxide/expanded graphite (MgO/EG) catalyst was synthesized and applied for enhancing the degradation of Cu-ethylenediaminetetraacetic acid (Cu-EDTA) in an aqueous solution. The MgO/EG catalyst was characterized by XRD, SEM, EDS, and FTIR. For assessing the catalytic activity of MgO/EG, essential influencing factors were investigated including catalyst dosage, O3 dosage, initial pH, initial Cu-EDTA concentration, and coexisting ions. The results show that the catalytic material showed high catalytic oxidation capacity for the Cu-EDTA removal in the MgO/EG/O3 system. 100% of Cu(II) and 73.2% of TOC removal efficiency could be achieved in the MgO/EG/O3 system at the reaction times of 90 min. This efficiency was higher than that seen for other systems, including O3 alone (Cu(II) 81.4%/TOC 60.6%), EG/O3 (84.2%/64.1), MgO/EG (< 4%/< 4%), and EG (< 4%/< 4%). A small decrease in the Cu(II) and TOC removal rate was observed after three runs in the stability and reusability experiments of the catalyst. Assays with radical scavenging experiments confirmed that MgO/EG-mediated oxidation was dependent on a hydroxyl radical pathway. The UV–vis spectra confirmed that the absorption peak of Cu-EDTA was gradually decreased and finally disappeared. [ABSTRACT FROM AUTHOR]

A novel calcium carbonate (CaCO3)/expanded graphite (EG) catalyst was fabricated, characterized, and used in a catalytic ozonation process to increase degradation and mineralization of ethylenediaminetetraacetic acid (EDTA) aqueous solutions. Various techniques were used to analyze the crystalline structure, morphology, and elemental composition of the novel CaCO3/EG catalyst, including X-ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. Mercury intrusion porosimetry was used to measure specific surface area, pore diameter, and pore volume of the CaCO3/EG catalyst. Essential influencing factors such as CaCO3/EG composite dosage and initial pH were also surveyed for different systems. Catalytic ozonation by CaCO3/EG was notably increased by the removal of total organic carbon (TOC) of EDTA. After 60 min, 80% TOC removal efficiency from simulated wastewater having an initial TOC concentration of 600 mg/L and initial pH of 4.9 was achieved using 1.0 g/L CaCO3/EG. This efficiency was higher than that seen for other systems, including O3 alone (40%), EG/O3 (39%), CaCO3/O3 (28%), and EG (4%). A small decrease in the CaCO3/EG-catalyzed TOC removal rate was observed after three runs, but nonetheless the efficiency was >80% after 120 min. Assays with tert-butanol confirmed that CaCO3/EG-mediated catalytic ozonation was dependent on a free radical pathway. The results support that CaCO3/EG material could serve as an important reusable resource for catalytic oxidation reactions during treatment of wastewater containing EDTA. [ABSTRACT FROM AUTHOR]