Design of a viscose based solid amine fiber: Effect of its chemical structure on adsorption properties for carbon dioxide

Adsorption of CO2 by surface modified coal-based activated carbons: kinetic and thermodynamic analysis

The effects of different surface modifiers on the CO2 adsorption capacity of coal-based activated carbons were studied, and the diffusion behavior, adsorption kinetics and thermodynamic parameters of CO2 in activated carbons were analyzed. The results show that compared with ethylene glycol, 1,2-propylenediamine and zinc chloride, potassium hydroxide and sodium hydroxide can greatly improve CO2 adsorption capacity. The adsorption rate is faster, and the adsorption capacity is larger, with the maximum CO2 adsorption capacity being 33.54 mL/g. Fick’s law can well describe the diffusion behavior of CO2 in activated carbon. The addition of a surface modifier can increase the diffusion coefficient. The diffusion of CO2 in activated carbon falls into the category of crystal diffusion. The adsorption kinetics of CO2 before and after surface modification follow the Bangham equation. During the adsorption process, δ H < 0, δ G < 0, δ S < 0. Surface modification can reduce adsorption heat and promote adsorption, and the adsorption process is dominated by physisorption.

Synthesis and characterization of a thermosensitive solid amine biomass adsorbent for carbon dioxide adsorption

A thermosensitive solid amine fiber SF-AM-co-NIPAM-HBP-NH₂ was synthesized by grafting temperature-sensitive monomer N-isopropyl acrylamide (NIPAM) as well as acrylamide (AM) onto the surface of substrate sisal fiber, and further aminating with hyperbranched amine. FTIR, ¹³C NMR, SEM, EA and TGA were used to confirm the structure and chemical properties of the grafted fibers. Swelling ratio and CO₂ adsorption-desorption experiment were investigated to verify the thermo-sensitivity of the grafted fibers and their CO₂ adsorption-desorption behavior. Compared with conventional solid amine adsorbents regenerated around 140 °C, SF-AM-co-NIPAM-HBP-NH₂ (1:1) with NIPAM could be regenerated at a much lower temperature of 60 °C, while still maintain a high CO₂ adsorption capacity (2.61 mmol/g), comparable to that of SF-AM-HBP-NH₂ (2.73 mmol/g) before NIPAM introduction. Its excellent regeneration property and the effect of energy consumption reduction make it possible to be used for CO₂ adsorption in industrial process.

Development and characterization of chitosan functionalized dialdehyde viscose fiber for adsorption of Au(III) and Pd(II)

A highly efficient fiber-based adsorbent (DAVFs-CS) was developed via decoration of chitosan (CS) on the dialdehyde viscose fibers (DAVFs) substrate, and employed to selective separation of precious metals from simulated contaminated water. The surface functionalization of the solid material was probed using the Fourier transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA) and nuclear magnetic resonance (NMR) technique. The batch characteristic results showed that the maximum uptake capacities of DAVFs-CS were higher up to 322 mg/g and 207 mg/g for Au(III) and Pd(II) at optimal pH 2.0 and 3.0, which exhibited competitiveness with the majority of the reported adsorbents. Meanwhile, the adsorption data were in accordance with Langmuir and PSO equations, which indicated that the monolayer chemisorption dominated the adsorption process. The competitive adsorption study showed that the removal efficiency of Au(III) was not susceptible to the co-existing impurities. Adsorption mechanism study revealed that the negative Au(III) or Pd(II) species were firstly adsorbed on DAVFs-CS via the protonated amino groups, subsequently the partially reduction of them to zero-valent gold and palladium with the help of reductive functional groups. Thus, DAVFs-CS could be as a promising adsorbent to recovery of precious metals owning to its unique adsorption mechanism and excellent adsorption performance.

Adsorption behavior and mechanism of Au(III) on caffeic acid functionalized viscose staple fibers

A novel fibrous adsorbent (DAVSF-CA) was synthesized via grafting caffeic acid (CA) onto dialdehyde viscose staple fiber (DAVSF), and used to selectively adsorb Au(III) from simulated wastewater. Fourier Transform Infrared (FTIR), X-ray Photoelectron (XPS) and Nuclear Magnetic Resonance (NMR) spectra confirmed that caffeic acid was successfully grafted on DAVSF through condensation reaction. Adsorption experiments revealed that the adsorption of Au(III) on DAVSF-CA was extremely dependent on pH values and temperatures, and the maximum adsorption capacity of 3.71 mmol/g for Au(III) was obtained at pH 3.0 and 333 K according to the Langmuir fitting. High temperature was favorable for Au(III) adsorption because the adsorption of Au(III) on the DAVSF-CA was endothermic. The competitive adsorption demonstrated that DAVSF-CA had a good preference to Au(III) adsorption in the presence of some coexisting pollutants. The adsorption isotherm data of Au(III) were well-described by the Langmuir model, while the kinetic data were fitted well by the Pseudo-second-order equation. The major reaction involving the reduction of Au(III) to Au(0) was identified by XPS and XRD analysis. Namely, Au(III) was first captured on protonated functional groups via electrostatic adsorption, and then reduced to its elemental form and formed the nano-particles on the adsorbent surfaces.

Structure Design of Low-Temperature Regenerative Hyperbranched Polyamine Adsorbent for CO2 Capture

A novel low-temperature regenerative hydroxy-functionalized hyperbranched polyamine adsorbent (0.16OH-HBPA) for CO₂ capture was readily prepared using glutaraldehyde to cross-link amino-terminated hyperbranched polymers (HBP) and functionalized with glycidol, followed by the reduction of the imino groups of 0.16OH-HBPA to alkyl aminos using NaBH₄. Here, the HBP has been prepared through the one-pot reaction between pentaethylenehexamine and methyl acrylate. The as-prepared 0.16OH-HBPA adsorbent showed a high adsorption capacity (4.05 mmol/g) for CO₂ (concentration, 10%) in the presence of water at 25 °C, and the alkyl amino utilization efficiency reached 73%. More importantly, the CO₂-adsorbed 0.16OH-HBPA showed excellent regenerative performance at low temperatures (85 °C, under pure CO₂ gas) due to the introduced hydroxyl that can cooperatively adsorb CO₂ via the amino groups to form stable carbamic acid. This process suppressed the formation of open-chain urea and cyclic urea and could overcome the disadvantages of high regeneration temperatures (≥90 °C, under pure inert gas) of CO₂-adsorbed traditional solid amine adsorbents.

Preparation and Properties of A Hyperbranch-Structured Polyamine adsorbent for Carbon Dioxide Capture

A fibrous adsorbent with amino-terminated hyperbranch structure (PP-AM-HBP-NH₂) was prepared by grafting hyperbranched polyamine (HBP-NH₂) onto the acrylamide-modified polypropylene (PP) fibers. The grafting of AM on PP fibers provided the active sites for introducing HBP-NH₂ onto the PP fibers. This kind of “grafting to” procedure to synthesize hyperbranch-structured fiber could overcome the disadvantages of stepwise growth procedure, avoiding the complicated synthesis process and the requirement of strict experimental conditions. The grafted HBP-NH₂ was three-dimensional dentritic architecture and had a large number of pores existing within the grafted polymers, which is favorable for CO₂ molecules to diffuse into the HBP-NH₂. Therefore, the as-prepared PP-AM-HBP-NH₂ fibers showed a high adsorption capacity (5.64 mmol/g) for CO₂ in the presence of water at 25 °C, and the utilization efficiency of alkyl amino groups could reach 88.2%, demonstrating that the hyperbranched structure of adsorbents can greatly promote adsorption capacity and efficiency. This could be attributed to better swelling properties and lower mass transfer resistance to CO₂ of the hyperbranched adsorbent. PP-AM-HBP-NH₂ also showed excellent regeneration performance, and it could maintain the same adsorption capacity for CO₂ after 15 recycle numbers as the fresh adsorbent.

Preparation and characterization of amine-functionalized sugarcane bagasse for CO2 capture

A low-cost solid amine adsorbent for CO2 capture was prepared by using sugarcane bagasse (SB), a dominant agro-industrial residue in the sugar and alcohol industry as raw materials. In this preparation process, acrylamide was grafted on SB, and the grafted fiber was then aminated with different type of amine reagents to introduce primary and secondary amine groups onto the surface of SB fibers. The graft and amination conditions were optimized. The prepared solid amine adsorbent showed remarkable CO2 adsorption capacity and the adsorption capacity of the solid amine adsorbent could reach 5.01 mmol CO2/g at room temperature. The comparison of adsorption capacities of amine fibers aminated with various amination agents demonstrated that fibers aminated with triethylenetetramine would obtain higher adsorption capacities and higher amine efficiency. These adsorbents also showed good regeneration performance, the regenerated adsorbent could maintain almost the same adsorption capacity for CO2 after 10 recycles.

Sisal fiber-based solid amine adsorbent and its kinetic adsorption behaviors for CO2

A sisal-based solid amine adsorbent was prepared by grafting acrylamide and then aminating with amine agents. Remarkable CO₂ adsorption capacity (4.20 mmol g⁻¹) was achieved due to unique texture of vegetable and plentiful amine groups.