Adsorption Species Distribution and Multicomponent Adsorption Mechanism of SO₂, NO, and CO₂ on Commercial Adsorbents

Adsorption is a commonly used method for gas pollutant removal. The adsorption performances of four commercial adsorbents have been compared in this work through a fixed-bed reactor. The single gas adsorption results show that zeolite is more effective for SO₂, NO, and CO₂ removal among the four adsorbents. SO₂, NO, and CO₂ are mainly monolayer adsorbed on adsorbents. Physically adsorbed SO₂ is the main adsorption species on 13X zeolite, 5A zeolite, and mesoporous alumina according to TPD-MS, while SO₂ is more easily oxidized on activated carbon than the other adsorbents. NO can be oxidized more easily on zeolite than activated carbon. Only physically adsorbed CO₂ is detected on these adsorbents. Multicomponent adsorption is investigated on 13X zeolite and activated carbon. For gas adsorption on 13X zeolite, the inhibitive effect of NO on SO₂ is 26.3% higher than that of CO₂ on SO₂, indicating that NO plays a dominant role in SO₂ adsorption. Physically adsorbed NO is the only NO adsorption species on 13X when SO₂ exists, showing NO oxidation on 13X is greatly inhibited by SO₂. For gas adsorption on activated carbon, chemically adsorbed SO₂ increases largely after NO is put in, showing that the promotive effect of NO on SO₂ is mainly for the chemically adsorbed SO₂. In the presence of SO₂, chemically adsorbed NO almost disappeared, which indicates that SO₂ mainly dominates chemically adsorbed NO on activated carbon. The effects of adsorbent performance on multicomponent gas adsorption are reflected by the gas adsorption mechanism. These findings provide considerable specific information for industrial flue gas purification

The Roles of Sulfur-Containing Species in the Selective Catalytic Reduction of NO with NH₃ over Activated Carbon

In the selective catalytic reduction (SCR) of NO with NH₃ over activated carbon (AC), deactivation occurs over time in the presence of SO₂. This work distinguishes the multiple roles of SO₂ in the gas phase versus the solid deposition product and clarifies the effects of the physicochemical properties of AC on NO conversion. The deposition products were detected using temperature-programmed desorption (TPD) coupled with mass spectrum (MS) analysis and Fourier transform infrared (FTIR) spectrometry. The results showed that the activated carbon loses less de-NO_<i>x</i> activity when it has more CO- and CO₂-containing groups with decomposition temperatures over 900 K. The Raman spectra revealed that the disorder of the microcrystalline structure of the graphite has a positive linear correlation with NO conversion regardless of the presence of functional groups. The deposition products were analyzed by Gaussian-Lorentz deconvolution of the TPD spectra, and it was discovered that the sulfur-containing species included sulfate and strongly adsorbed SO₂/SO₃; the NH₃-containing species included NH₄HSO₄ and freely adsorbed NH₃; and the ratios of SO₂/SO₃, NH₄HSO₄ and NH₃ were approximately 31 mol %, 42 mol %, and 26 mol %, respectively. NH₄HSO₄ does not notably inhibit NO conversion, even with a high loading amount. The inhibitory effect of gaseous SO₂ on NO conversion is reversible, and this inhibitory effect is greater than that caused by the loss of functional groups. Increasing the disorder of the microcrystalline structure of the graphite and reducing the gaseous SO₂ were identified as ways to improve activated carbon activity for NO conversion

Optimization and evaluation of astragalus polysaccharide injectable thermoresponsive <i>in-situ</i> gels

<div><p>The objective of this study was to develop an injectable in situ forming gel system based on Poloxamer for sustained release of Astragalus polysaccharide (APS), thus achieved once or twice administration instead of frequent dosing during long-term treatment. The optimal formulation is 10 g APS, 18 g poloxamer 407, 2 g poloxamer 188, 0.15 g CMC-Na, 0.85 g sodium chloride in 100 ml gel in situ which had a preferable sol-gel transition temperature(<i>T</i> sol-gel) (34.1 ± 0.4°C), and good stability. In vitro release studies, all formulations containing polymer additives had prolonged release time and decreased initial burst to some extent. The optimal formulation containing 0.15% CMC-Na showed a best sustained release profile for about 132 h with the lowest initial burst in vitro about 16.30% in 12 h). In vivo, Male BALB/c mice (18–20 g) were administrated with APS in-situ gel just once, the values of immune organ indices, spleen lymphocyte proliferation, and serum IgM, IgG, IL-2 and IL-6 had significant increase, which was consistent with the mice given daily APS injections (7 times), while the above indices were increased more significantly in which administrated with APS in-situ gel twice. Based on these results, it can be concluded that the Poloxamer depot is a promising carrier for the sustained release of APS with an ideal release behavior.</p></div