Sunflower stalk–derived biochar enhanced thermal activation of persulfate for high efficient oxidation of p-nitrophenol
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Sunflower stalk–derived biochars (BC) were prepared at various temperatures (i.e., 500, 650, and 1000 °C) and demonstrated as a highly efficient catalyst in persulfate (PS) activation for the oxidation of p-nitrophenol (PNP) at 60 °C. The apparent PNP oxidation rate constant in the BC500 (0.1543 L mol−1 S−1), BC650 (0.6062 L mol−1 S−1), or BC1000 (2.1379 L mol−1 S−1) containing PS system was about 2, 8 and 28 times higher than that in PS/PNP (0.0751 L mol−1 S−1) system, respectively. The effect of reaction temperature on PNP oxidation was also investigated. Furthermore, the radical quenching tests and electron paramagnetic resonance spectroscopy (EPR) were employed to investigate the sulfate and hydroxyl radicals for PNP oxidation. The Raman results suggested that the defective sites on biochars possess vital role for oxidation of PNP in PS system. The possible activation pathway of PS/BC was proposed that the defective sites on BC were involved for weakening the O–O bond in PS and subsequently cleaving O–O bond by heat to generate sulfate radical. The oxidation of PNP at low concentration (below 100 μg L−1) was completely removed in urban wastewater by PS/BC system within 30 min. This work would provide new insights into PS activation by BC catalyst and afford a promising method for organic pollutant removal in high-temperature wastewater.
KeywordsSunflower stalk–derived biochar Persulfate p-Nitrophenol Oxidation Defective sites
The authors thank the Analytical and Testing Center of HUST for the use of Raman, EA, FTIR, XPS, and XRD equipments.
This work is financially supported by the International Science & Technology Cooperation Program of China (Nos. 2013DFG50150 and 2016YFE0126300) and the Innovative and Interdisciplinary Team at HUST (2015ZDTD027).
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