Exploring the activity of chemical-activated carbons synthesized from peach stones as metal-free catalysts for wet peroxide oxidation

• Published in: Catalysis today Vol. 313; pp. 20 - 25
• Main Authors: Martin-Martinez, Maria, Álvarez-Torrellas, Silvia, García, Juan, Silva, Adrián M.T., Faria, Joaquim L., Gomes, Helder T.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2018
• Subjects: Activated carbon; Chemical activation; Metal-free CWPO; Peach stone; Chemical activation; Peach stone; Activated carbon; Metal-free CWPO
• ISSN: 0920-5861; 1873-4308
• DOI: 10.1016/j.cattod.2018.01.003

[Display omitted] •Activated carbon from peach stones was prepared by chemical activation with H3PO4.•The presence of surface acidic groups in PS, hinders the decomposition of H2O2.•The impregnation with platinum strongly favors H2O2 decomposition.•The hydrophilicity increment promotes the formation of non-reactive species.•The calcination of the activated carbon promotes the generation of HO radicals. Peach stones were used as raw material for the synthesis of activated carbons with different properties. Firstly, peach stones were chemically activated using a 12 M H3PO4 solution and carbonized under flowing air (400 °C). The obtained activated carbon, named as PS, is characterized by a high surface development (SBET = 1262 m2 g−1) and acidic character (pHPZC = 4.2). A fraction of PS was further carbonized under N2 atmosphere at 800 °C to remove surface functionalities and to increase its basicity (PS-800). In addition, a Pt catalyst supported on PS (3% w/w Pt/PS) was synthesized by incipient wetness impregnation, resulting in a considerable hydrophilicity increasing. The synthesized materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated solutions of 4-nitrophenol (4-NP, 5 g L−1) during 24 h experiments, conducted at relatively mild operating conditions (T = 50–110 °C, pH = 3, catalyst load = 2.5 g L−1 and [H2O2]0 = 17.8 g L−1, corresponding to the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP). It was observed that the increase of electron-donating functionalities in PS-800 promotes the generation of reactive HO radicals, being the activity towards CWPO twice higher than that obtained with the pristine PS. Besides, increasing operating temperature substantially enhances CWPO, finding a 80% of 4-NP removal at 110 °C. On the other hand, despite the sharp increment in H2O2 decomposition due to the presence of Pt particles in Pt/PS catalyst, this decomposition is inefficient in all cases, with a consequent poor pollutant removal. This can be attributed to the recombination of HO radicals into non-reactive species −scavenging effects, promoted by the hydrophilicity of the catalyst.