Enhanced CO₂ Adsorption Using MgO-Impregnated Activated Carbon: Impact of Preparation Techniques

The development of a facile and sustainable approach to produce magnesium oxide (MgO) activated carbons impregnated through a single-step activation of biochar is reported. In a single-step activation process, biochar is impregnated with 3 and 10 wt % of magnesium salt solutions followed by steam activation. In a two-step method, activated carbon, the product of steam activation of biochar, is impregnated with magnesium salt using the incipient wetness and excess solution impregnation process and calcined. The impacts of activation method, impregnation method, and metal content are evaluated, and the product qualities are compared in terms of porosity and surface chemistry. The sorbents are then used for CO2 capture in low partial pressure of CO2 at 25 and 100 °C from a feed containing 15% CO2 in N2 in a fixed-bed reactor. The incipient wetness of activated carbons results in the highest CO2 uptake (49 mg/g) at 25 °C, while single-step impregnation of biochar with rinsing step yields the largest surface area (760 m2/g) and the second highest CO2 uptake (47 mg/g). The increase in Mg content from 3 to 10 wt % results in the smaller surface area and higher CO2 uptake suggesting that the metal content has a greater impact than porosity and surface area. Rinsing the Mg impregnated activated carbon with water results in the larger surface area and higher CO2 uptake in all samples. Moreover, the CO2 adsorption runs at 100 °C shows a 65% increase using MgO impregnated activated carbon as compared to steam activated carbon indicating that MgO impregnation of activated carbon can overcome the limitation of using nontreated activated carbon at moderate operating temperature of 100 °C and low partial pressure of CO2 of 15 mol %

Selective CO₂ Capture by Activated Carbons: Evaluation of the Effects of Precursors and Pyrolysis Process

Activated carbons are produced from different Canadian waste biomasses including agricultural waste (wheat straw and flax straw), forest residue (sawdust and willow ring), and animal manure (poultry litter). The precursors are carbonized through the fast and slow pyrolysis processes and then activated with potassium hydroxide. A fixed-bed reactor is used for temperature swing adsorption of CO₂ in a gas mixture of N₂, O₂, and CO₂ to study the cyclic CO₂ adsorption capacity and selectivity of the produced activated carbons. The breakthrough adsorption capacity of the produced activated carbon is measured under a flue gas condition of 15 mol % of CO₂, 5 mol % of O₂, and 80% of N₂ at 25 °C and atmospheric pressure. Slow pyrolysis based activated carbon has a lower surface area and total pore volume but higher adsorption capacity in the presence of N₂. Sawdust based activated carbon synthesized using the slow pyrolysis process creates the highest ultra-micropore volume of 0.36 cm³/g, and the highest adsorption capacity in N₂ (78.1 mg/g) but low selectivity (2.8) over O₂ because of the oxygen functional groups on the surface. Ultra-micropores and surface chemistry of adsorbents are far more important than particle size, total pore volume, and internal surface area of the adsorbents. All the samples fully recovered their initial adsorption capacity in each cycle (for up to 10 cycles). This work also demonstrates that adsorption capacity and selectivity of activated carbon can be controlled and optimized through the choice of starting material and carbonization conditions

Effect of Class Switch Recombination Defect on the Phenotype of Ataxia-Telangiectasia Patients

Objectives: Ataxia-telangiectasia (A-T) is an autosomal recessive neurodegenerative disorder with multisystem involvement caused by homozygous or compound heterozygous mutations in the ataxia telangiectasia mutated (ATM) gene which encodes a serine/threonine protein kinase. The aims of this study were to investigate class switch recombination (CSR) and to review the clinical and immunologic phenotypes of 3 groups of A-T patients, including A-T patients with CSR defects (CSR-D), A-T patients with selective immunoglobulin A deficiency (IgA-D) and A-T patients with normal Ig level. Methods: In this study, 41 patients with confirmed diagnosis of A-T (16 A-T patients with HIgM, 15 A-T patients with IgA-D, and 10 A-T patients with normal Ig levels) from Iranian immunodeficiency registry center were enrolled. B-cell proliferation, in vitro CSR toward IgE and IgA were compared between three groups as well as G2 radiosensitivity assay. Results: Earliest presentation of telangiectasia was a significant hallmark in A-T patients with CSR-D (p = .036). In this investigation, we found that the frequency of respiratory infection (p = .002), pneumonia (p = .02), otitis media (p = .008), chronic fever (p p = .02) and hepatosplenomegaly (p = .03) in A-T patients with HIgM phenotype were significantly higher than the other groups. As expected IgE production stimulation and IgA CSR were perturbed in HIgM patients that were aligned with the higher readiosenstivity scores in this group. Conclusion: A-T patients with HIgM compared to other A-T patients presenting more infections and noninfectious complications, therefore, early detection and careful management of these patients is necessary.</p