Cobalt-aluminum spinel supported on modified γ-alumina for peroxymonosulfate activation: Si–Al ratio of support to optimize performance and reusability.

The development of cobalt-based supported catalysts with high PMS catalytic activity and stability by adjusting the composition of the support is highly desirable yet remains scarce. In the work, a series of catalysts (Co 2 AlO 4 /Al 2 O 3 -xSiO 2) were prepared by impregnation and high-temperature calcination using Al 2 O 3 -xSiO 2 with a low Si–Al ratio as the support. Measurement techniques such as XRD, XPS, UV-DRS, FTIR, BET, SEM and HRTEM were used to characterize textural and chemical properties (ratio of Co3+/Co2+, specific surface area, pore size, pore volume, etc.). The ratio of Co3+/Co2+ and pore volume of Co 2 AlO 4 /Al 2 O 3 -xSiO 2 can be turned by controlling the ratio of Si to Al, which are closely related to the catalytic performance and reusability of the catalysts. The optimized catalyst (Co 2 AlO 4 /Al 2 O 3 -0.25SiO 2) can completely degrade 10 mg/L p-nitrophenol (PNP) in 40 min in the pH range of 3–9 with excellent reusability. The effects of several reaction parameters (i.e., PMS dosage, Co 2 AlO 4 /Al 2 O 3 -0.25SiO 2 dosage, reaction temperature, initial pH value, and inorganic ions) on PNP removal were comprehensively investigated. Sulfate radical (SO 4 •−) and singlet oxygen (1O 2) are making a major contribution to the degradation of PNP. Moreover, a millimeter-scale catalyst (CoSiAl-0.25/Al 2 O 3 pellet) was prepared by sol adsorption and high-temperature calcination method, which maintained high oxidation activity after treatment of 18 L wastewater (PNP of 10 mg/L) in a continuous flow process. The method is simple and easy to operate on a large scale, providing a new perspective on the design and preparation of cobalt-aluminum spinel catalysts for activated PMS. [Display omitted] • Co 2 AlO 4 /Al 2 O 3 -xSiO 2 were prepared by impregnation and calcination. • The ratio of Si–Al plays a key role in catalytic performance and reusability. • Sulfate radical (SO 4 •−) and singlet oxygen (1O 2) is the crucial reactive species. • The Co3+/Co2+ were the intrinsic active centers for PMS activation. • CoSiAl-0.25/Al 2 O 3 pellet exhibited better long-term PNP removal ability. [ABSTRACT FROM AUTHOR]