Adsorption Performance Of Activated Carbon Research Articles

Calcium oxide adsorption of gas phase PCDD/Fs and its impact on the adsorption properties of activated carbon

Calcium oxide (CaO), utilized in semi-dry/dry desulfurization systems at municipal solid waste incineration (MSWI) plants, demonstrates some capability to remove polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study assessed the gas-phase PCDD/F removal performance of CaO, activated carbon (AC) and CaO-AC mixtures. Alone, CaO achieved removal efficiencies of only 31.9% for mass and 50.8% for I-TEQ concentration. However, CaO-AC mixtures exhibited significantly higher efficiencies, reaching 96.0% and 92.5% for mass and I-TEQ concentrations, respectively, surpassing those of AC alone, which were 74.7% and 58.5%. BET analysis indicated that CaO's limited surface area and pore structure are major constraints on its adsorption performance. Density functional theory (DFT) calculations revealed that the π-π electron donor-acceptor (EDA) interaction enhances the adsorption between AC and PCDD/F, with adsorption energies ranging from −1.02 to −1.24 eV. Additionally, the induced dipole interactions between CaO and PCDD/F contribute to adsorption energies ranging from −1.13 to −1.43 eV. Moreover, with increasing chlorination levels, PCDD/F molecules are more predisposed to accept electron transfers from the surfaces of AC or CaO, thereby facilitating adsorption. The calculation for mixed AC and CaO showed that CaO modifies AC's properties, enhancing its ability to adsorb gas phase PCDD/Fs, with the higher adsorption energy and more electrons transfer, aligning with gas phase PCDD/Fs adsorption experiments. This study provides a comprehensive understanding of how CaO influences the PCDD/F adsorption performance of AC.

Effect of dispersant on the synthesis of cotton textile waste-based activated carbon by FeCl2 activation: characterization and adsorption properties.

Considering the accumulation and high consumption of activating agents, anhydrous ethanol (AE) could be used to dissolve them to improve the dispersion effect, which was an effective way of improving the practical utilization rate. In this study, FeCl2 was dissolved in AE and further impregnated cotton textile waste (CTW) to prepare activated carbons (ACs) by pyrolysis. Afterward, ACs prepared in optimal conditions determined by the orthogonal experiment evaluated the physicochemical properties and adsorption capacities for Cr(VI). The results illustrated that AE greatly increased the dispersion of FeCl2 on CTW, reduced the conventional impregnation dosage, and remarkably improved the activation efficiency. Textural analyses revealed that ACs exhibited excellent porosity properties and graphite carbon structure. FeCl2 catalyzed the decomposition of volatile substances to produce gaseous products and promoted the transformation of amorphous carbon to graphite carbon that was conducive to pore development, followed by the formation of developed micropores and crystal structures. The adsorption performance of ACs was estimated using Cr(VI), and the adsorption was fitted with the pseudo-second-order kinetic and the Langmuir isotherm. Furthermore, the ACs possessed superior magnetization and reusability. Graphical abstract.

Role of inherent pyrite in coal on physicochemical structure of activated carbon and adsorption capacity

Pyrite is the most common inorganic iron-bearing mineral in coal. In order to reveal the influence of inherent pyrite on physicochemical structure and adsorption performance of AC, in this study, different content of pyrite (0.5%, 1%, 2%, 3%) were physically mixed with Yangcheng coal and briquetted, carbonized and steam activated for activated carbon (AC) preparation. As-obtained ACs’ morphology, pore texture, carbon crystallite structure and surface chemistry were characterized by SEM, BET, XRD and FTIR, respectively. The results show that pyrite (FeS2) transformed into hematite (Fe2O3) during AC preparation. Pyrite promotes the interaction between water vapor and carbon and enhances the rate of gasification reactivity by inhibiting the growth of heavy aromatic structures, catalyzing the graphitization process and enhancing the surface chemical properties. The total specific area and specific surface area of micropore of 2%FeS2/AC are up to 836 m2/g and 644 m2/g, which are 58.6% and 46.9% higher than AC, respectively. The 2 h sulfur capacity of 2%FeS2/AC is up to 65.2 mg/g, which is 18.8% greater than that of AC (54.9 mg/g), the mechanism of which was proposed: absorbed gaseous SO2 finally transformed into H2SO4 in macropores and forming an acid macro-environment where most Fe2O3 attacked by the generated H2SO4 on the AC’s pore surface to form Fe2(SO4)3. Fe3+ can promote the oxidation of SO3 to form H2SO4, and a redox cycle of Fe2+ and Fe3+ was established. Moreover, 1%FeS2/AC shows the highest Rhodamine B (RhB) adsorption, and the capacity of RhB is 168 mg/g, which is 41.2% higher than that of AC.

Photocatalytic degradation of vehicle exhaust using Fe-doped TiO2 loaded on activated carbon

To enhance the photocatalytic degradation efficiency of TiO2 on vehicle exhaust (VE), nanoscale Fe-doped TiO2 (Fe-TiO2) was synthesized and loaded on the activated carbon (AC) to prepare a composite photocatalyst AC/Fe-TiO2. The loaded amount of Fe-TiO2, the chemical compositions, adsorption-desorption properties, and photocatalytic degradation efficiency of the AC/Fe-TiO2 on VE were discussed. Results indicated that the synthesized Fe-TiO2 only contained anatase phase, and the optical absorption edges of Fe-TiO2 showed an obvious red shift. Fe-TiO2 particles were successfully loaded on the AC. Fe-TiO2 particles were mainly distributed in the macropores and mesopores of the AC. The loaded Fe-TiO2 had a slight effect on the AC adsorption property. Furthermore, the Ti concentration on the AC was increased, but the specific surface area, total pore volume, and average pore size of the AC were decreased with the increase in loading rounds of Fe-TiO2. The AC with the narrow pores demonstrated the best adsorption, belonging to narrow pore adsorption. Additionally, each component of VE was enriched on Fe-TiO2 surface. This enhanced effectively the degradation efficiency on VE due to the photocatalytic activity of Fe-TiO2 and the oxidation-reduction of active functional groups on the AC surface. The photocatalytic degradation efficiency of AC/Fe-TiO2 was increased due to the synergistic effect between AC adsorption and Fe-TiO2 photocatalysis. This facilitated the photocatalytic degradation reaction of Fe-TiO2 with VE. Finally, excessively loaded Fe-TiO2 lowered the specific surface area, total pore volume, and average pore size of the AC, leading to a decrease in adsorption performance of AC and photocatalytic degradation efficiency of Fe-TiO2. Three loading rounds were proposed to prepare AC/Fe-TiO2 for purifying VE in road tunnels.

Adsorption of quinolone, tetracycline, and penicillin antibiotics from aqueous solution using activated carbons: Review.

Antibiotics, an important type of pharmaceutical pollutant, have attracted many researchers to the study of their removal from aqueous solutions. Activated carbon (AC) has been widely used as highly effective adsorbent for antibiotics because of its large specific surface area, high porosity, and favorable pore size distribution. In this article, the adsorption performance of AC towards three major types of antibiotics such as tetracyclines, quinolones, and penicillins were reviewed. According to collected data, maximum adsorption capacities of 1340.8, 638.6, and 570.4mg/g were reported for tetracyclines, quinolones, and penicillins, respectively. The values of 1/n for Freundlich isotherm were less than unity, suggesting that the adsorption was nonlinear and favorable. Adsorption kinetics followed closely the pseudo-second-order model and analysis using the Weber-Morris model revealed that the intra-particle diffusion was not the only rate controlling step. AC adsorption demonstrated superior performance for all selected drugs, thus being efficient technology for treatment of these pollutants.