Manganese oxides at different oxidation states for heterogeneous activation of peroxymonosulfate for phenol degradation in aqueous solutions

Abstract

A series of manganese oxides (MnO, MnO 2 , Mn 2 O 3 and Mn 3 O 4 ) were synthesized and tested in heterogeneous activation of peroxymonosulfate (PMS) for phenol degradation in aqueous solutions. Their properties were characterized by several techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and N 2 adsorption/desorption isotherms. Catalytic activities of Mn oxides were found to be closely related to the chemical states of Mn. Mn 2 O 3 is highly effective in heterogeneous activation of PMS to produce sulfate radicals for phenol degradation compared with other catalysts (MnO, MnO 2 , and Mn 3 O 4 ). The activity shows an order of Mn 2 O 3 > MnO > Mn 3 O 4 > MnO 2 . Mn 2 O 3 could completely remove phenol in 60 min at the conditions of 25 ppm phenol, 0.4 g/L catalyst, 2 g/L PMS, and 25 o C. After heat regeneration, the activity could be fully recovered. A pseudo first order model would fit to phenol degradation kinetics and activation energy was obtained as 11.4 kJ/mol.

Synthetic conditions-regulated catalytic Oxone efficacy of MnO x /SBA-15 towards butyl paraben (BPB) removal under heterogeneous conditions

“…Indeed, differentiated MnO x species of MS with changed oxidation states can be observed in current study where Mn 2 O 3 and Mn 3 O 4 are suspected as the main species of MS 8 (823,3) (refer to XPS analysis in Section 3.1.4). Moreover, previous work indicated that the catalytic decomposition of Oxone was closely associated with the oxidation states of bare MnO x particles with a conclusion that Mn 2 O 3 and Mn 3 O 4 are more effective for Oxone activation than MnO 2 [23]. Hence, it is understandable that the changes of MnO x species in oxidation states could control the types and the amounts of free radicals formed in MS-Oxone systems, thus regulating their catalytic Oxone removal ability of BPB.…”

“…In addition, Co and Co/Mg decorated SBA-15 hybrids were found to provide higher catalytic Oxone efficacy during the treatment of wastewater containing organic chemicals and the hybrid catalysts exhibited excellent stability over their recycle processes [20][21][22]. Although the catalytic Oxone efficacy of MnO x or other metalbased composites toward the removal of commonly found organic contaminants such as phenols and dyes has been demonstrated in previous work [4,[23][24][25][26][27][28][29][30]], yet, thus far, such information on the catalytic Oxone performance of MnO x decorated SBA-15 composite for the removal of pharmaceutical and personal care products (PPCPs) is still unavailable.…”

“…It is also evidenced that bare MnO x with different valence states, morphologies and crystal phases often shows different catalytic performance against the decomposition of organic substrates [4,23,24,31,32]. On the other side, MnO x formed within porous silica was reported to possess different oxide states [11][12][13], which resulted in varied catalytic performance.…”

Sulfate Radical Technologies as Tertiary Treatment for the Removal of Emerging Contaminants from Wastewater

“…Saputra et al [67] Liu et al [68] reported a comparison study of propachlor degradation by persulfate activation using two metal ions such as Cu(II) and Fe(II), respectively. Both metals ions were able to activate persulfate and degradate the target molecules.…”

“…The particle size plays an important role on activated carbon activity, because its performance as a PMS activator depends of the density of the surface. Saputra et al (2013), [67] demonstrated that powdered activated carbon (PAC) was much more effective than granular activated carbon (GAC) and proposed the following reaction mechanisms:…”