Catalytic wet peroxide oxidation of aniline in wastewater using copper modified SBA-15 as catalyst

Abstract

SBA-15 mesoporous molecular sieves modified with copper (Cu-SBA-15) were prepared by pH-adjusting hydrothermal method and characterized by X-ray diffraction, BET, transmission electron microscopy, UV-Vis and (29)Si MAS NMR. The pH of the synthesis gel has a significant effect on the amount and the dispersion of copper on SBA-15. The Cu-SBA-15(4.5) (where 4.5 denotes the pH value of the synthesis gel) modified with highly dispersed copper was used as catalyst for the oxidation of aniline by H2O2. The Cu-SBA-15(4.5) shows a higher catalytic activity compared to CuO on the surface of SBA-15. The influences of reaction conditions, such as initial pH of the aqueous solutions, temperature, as well as the dosages of H2O2 and catalyst were investigated. Under weakly alkaline aqueous solution conditions, the aniline conversion, the H2O2 decomposition and the total organic carbon (TOC) removal could be increased significantly compared to the acid conditions. The percentage of leaching Cu(2+) could be decreased from 45.0% to 3.66% when the initial pH of solution was increased from 5 to 10. The TOC removal could be enhanced with the increases of temperature, H2O2 and catalyst dosage, but the aniline conversion and H2O2 decomposition change slightly with further increasing dosage of catalyst and H2O2. At 343 K and pH 8.0, 100% aniline conversion and 66.9% TOC removal can be achieved under the conditions of 1.0 g/L catalyst and 0.05 mol/L H2O2 after 180 min. Although copper might be slightly leached from catalyst, the homogeneous Cu(2+) contribution to the whole catalytic activity is unimportant, and the highly dispersed copper on SBA-15 plays a dominant role.

Recent progress in magnetic nanoparticles and mesoporous materials for enzyme immobilization: an update

“…Over the last 20 years, SBA-15 has been widely used for immobilizing lipase. In recent years, organically modified and ionic liquid-modified SBA-15 have shown satisfactory performance in enzyme immobilization (Abolghasemi et al, 2016;Kong et al, 2016;Yuan et al, 2016). The immobilization of Candida antarctica lipase B (CALB) by using mesoporous SBA-15 resulted in improved enzymatic activity and stability.…”

1. Noncatalytic and catalytic oxidation of organic pollutants in wastewater by air

“…The reaction mechanism of CWAO of phenol is illustrated in Figure 1.9 and involves the following reaction steps [135]: Further exploration on mixed oxides leads to mesoporous materials such as MCM-41 [63], SBA-15 [67], zeolites [58], and pillared clay [5,139]. They could be a promising catalyst support for CWAO due to their uniform pore structure and large surface area.…”

“…They could be a promising catalyst support for CWAO due to their uniform pore structure and large surface area. Copper catalysts supported on mesoporous SBA-15 were evaluated in the oxidation of aniline with H 2 O 2 as oxidizing agent [67]. The effects of reaction conditions such as initial pH of the reaction mixture and reaction temperature on the aniline and TOC conversion were investigated.…”

“…One of the major limitations of heterogeneous catalysts is the relatively rapid deactivation under CWAO operating condition, which could be due to one or several reasons of the following: (i) leaching and sintering of the active metal species, (ii) loss of surface area of the supporting material, (iii) possible poisoning of the active sites by intermediates, and (iv) deposition of organic or inorganic compounds (coking) on the catalyst surface [21]. Metal oxide catalysts, in particular Cu, as we know it, are more vulnerable to metal leaching under acidic condition [60,66,67]. However, it can be controlled to a large extent by an appropriate choice of catalytic metal or metal oxide phase as well as pH of the solution.…”

“…In particular, copper-based catalysts are susceptible to leaching in spite of their good catalytic activity [61,64,66,67]. Santos et al found that the rate of copper leaching increased noticeably when the pH of the solution was less than 4 [64].…”