Genggeng Qi

High efficiency nanocomposite sorbents for CO2 capture based on amine-functionalized mesoporous capsules

A novel high efficiency nanocomposite sorbent for CO2 capture has been developed based on oligomeric amine (polyethylenimine, PEI, and tetraethylenepentamine, TEPA) functionalized mesoporous silica capsules. The newly synthesized sorbents exhibit extraordinary capture capacity up to 7.9 mmol g−1 under simulated flue gas conditions (pre-humidified 10% CO2). The CO2 capture kinetics were found to be fast and reached 90% of the total capacities within the first few minutes. The effects of the mesoporous capsule features such as particle size and shell thickness on CO2 capture capacity were investigated. Larger particle size, higher interior void volume and thinner mesoporous shell thickness all improved the CO2 capacity of the sorbents. PEI impregnated sorbents showed good reversibility and stability during cyclic adsorption–regeneration tests (50 cycles).

In situ formation of silver nanoparticles on thin-film composite reverse osmosis membranes for biofouling mitigation

The potential to incorporate silver nanoparticles (Ag-NPs) as biocides in membranes for water purification has gained much interest in recent years. However, a viable strategy for loading the Ag-NPs on the membrane remains challenging. This paper presents a novel, facile procedure for loading Ag-NPs on thin-film composite (TFC) reverse osmosis membranes. Reaction of silver salt with a reducing agent on the membrane surface resulted in uniform coverage of Ag-NPs, irreversibly bound to the membrane, as confirmed by XPS, TEM, and SEM analyses. Salt selectivity of the membrane as well its surface roughness, hydrophilicity, and zeta potential were not impacted by Ag-NP functionalization, while a slight reduction (up to 17%) in water permeability was observed. The formed Ag-NPs imparted strong antibacterial activity to the membrane, leading to reduction of more than 75% in the number of live bacteria attached to the membrane for three model bacteria strains. In addition, confocal microscopy analyses revealed that Ag-NPs significantly suppressed biofilm formation, with 41% reduction in total biovolume and significant reduction in EPS, dead, and live bacteria on the functionalized membrane. The simplicity of the method, the short reaction time, the ability to load the Ag-NPs on site, and the strong imparted antibacterial activity highlight the potential of this method in real-world RO membrane applications.

Efficient CO2 sorbents based on silica foam with ultra-large mesopores

A series of high-capacity, amine impregnated sorbents based on a cost-effective silica foam with ultra-large mesopores is reported. The sorbents exhibit fast CO2 capture kinetics, high adsorption capacity (of up to 5.8 mmol g−1 under 1 atm of dry CO2), as well as good stability over multiple adsorption–desorption cycles. A simple theoretical analysis is provided relating the support structure to sorbent performance.

Sponges with covalently tethered amines for high-efficiency carbon capture

Adsorption using solid amine sorbents is an attractive emerging technology for energy-efficient carbon capture. Current syntheses for solid amine sorbents mainly based on physical impregnation or grafting-to methods (for example, aminosilane-grafting) lead to limited sorbent performance in terms of stability and working capacity, respectively. Here we report a family of solid amine sorbents using a grafting-from synthesis approach and synthesized by cationic polymerization of oxazolines on mesoporous silica. The sorbent with high amount of covalently tethered amines shows fast adsorption rate, high amine efficiency and sorbent capacity well exceeding the highest value reported to date for low-temperature carbon dioxide sorbents under simulated flue gas conditions. The demonstrated efficiency of the new amine-immobilization chemistry may open up new avenues in the development of advanced carbon dioxide sorbents, as well as other nitrogen-functionalized systems.

CO2 Sorption Kinetics of Scaled-Up Polyethylenimine-Functionalized Mesoporous Silica Sorbent

Two CO2 solid sorbents based on polyethylenimine, PEI (M(n) ∼ 423 and 10K), impregnated into mesoporous silica (MPS) foam prepared in kilogram quantities via a scale-up process were synthesized and systematically characterized by a range of analytical and surface techniques. The mesoporous silica sorbent impregnated with lower molecular weight PEI, PEI-423/MPS, showed higher capacity toward CO2 sorption than the sorbent functionalized with the higher molecular weight PEI (PEI-10K/MPS). On the other hand, PEI-10K/MPS exhibited higher thermal stability than PEI-423/MPS. The kinetics of CO2 adsorption on both PEI/MPS fitted well with a double-exponential model. According to this model CO2 adsorption can be divided into two steps: the first is fast and is attributed to CO2 adsorption on the sorbent surface; the second is slower and can be related to the diffusion of CO2 within and between the mesoporous particles. In contrast, the desorption process obeyed first-order kinetics with activation energies of 64.3 and 140.7 kJ mol(-1) for PEI-423/MPS and PEI-10K/MPS, respectively. These studies suggest that the selection of amine is critical as it affects not only sorbent capacity and stability but also the energy penalty associated with sorbent regeneration.

Synthesis and Carbon Dioxide Sorption of Layered Double Hydroxide/Silica Foam Nanocomposites with Hierarchical Mesostructure

Layered double hydroxides (LDHs) with a hierarchical mesostructure are successfully synthesized on mesoporous silica foams by simple impregnation and hydrothermal treatment. The as-synthesized LDH/silica foam nanocomposites show well-defined mesostructures with high surface areas, large pore volumes, and mesopores of 6-7 nm. The nanocomposites act as carbon dioxide (CO2 ) sorbents under simulated flue gas conditions. They also exhibit significantly enhanced CO2 capacities under high-pressure conditions and high CO2 /N2 and CO2 /CH4 selectivities.

Yellow emitting carbon dots with superior colloidal, thermal, and photochemical stabilities

Herein we report the hydrothermal synthesis of yellow emitting carbon dots, CDs, in high salinity water and compare them with those prepared in distilled water. The saline environment significantly affects the surface chemistry and charge of the CDs. We also present data on their long-term colloidal and photochemical stability in distilled and saline water at ambient and high temperatures. The facile preparation and shelf life stability coupled with their improved photochemical and thermal properties make them potential applicants as tracers for biomedical, subsurface and other technologies that require stability under harsh conditions.

Superhydrophilic Wrinkle-free Cotton Fabrics via Plasma and Nanofluid Treatment

We demonstrate in this study a wrinkle-free, superhydrophilic cotton fabric (contact angle ∼0°) by uniformly attaching specially engineered nanoparticles to plasma-pretreated cotton fabric. Because of their highly charged nature, the nanoparticles are firmly anchored on the fabric via electrostatic interactions, as confirmed by microscopy and chemical analyses. The durability of wetting behavior and wrinkle-free property of the nanoparticle-coated fabrics were evaluated via aging, laundering, and abrasion tests. The strongly attached coatings are stable enough to maintain their superhydrophilic nature even after 60 days of aging at room temperature, 50 laundering cycles, and 25 000 abrasion cycles. Moreover, the nanoparticle-coated superhydrophilic fabrics exhibit great wrinkle-recovery property, tensile strength, and abrasion resistance performance up to 25 000 abrasion cycles.

A Highly Efficient and Selective Polysilsesquioxane Sorbent for Heavy Metal Removal

Considerable efforts are under way worldwide to remove heavy metal ions from contaminated water because of their detrimental effect on the environment and human health. Among various approaches, adsorption has drawn particular attention due to its ease of handling, low energy consumption, and high process flexibility. 2] Two of the most widely studied sorbents for heavy metal removal are based on polymers and mesoporous organosilicas. Polymer-based sorbents include both synthetic and semi-natural polymers with carboxylic acid, sulfonic acid, and imidazole functional groups. Generally, polymer-based sorbents are non-selective toward heavy metals and an increase in their selectivity comes at the expense of sorbent capacity. In contrast to polymer-based sorbents, mesoporous organosilicas show several advantages for metal ion adsorption due to a number of features including high surface area, tunable pore structure, and ease of functionalization. Two major synthetic approaches have been used to synthesize mesoporous organosilica sorbents: a) post-grafting or co-condensation of functional groups on the surface of mesoporous silica and b) one-pot synthesis involving direct incorporation of functional groups inside the silica framework (polysilsesquioxane sorbents) using appropriate precursors. In the former approach, an increase in the density of functional groups in the sorbent comes usually at the expense of surface area available for metal ions, ultimately compromising the performance of the sorbent. 9, 11] In the latter approach, a precursor, with a formula of (R’O)3-Si-R-Si-(OR’)3, where R contains a potentially active group, such as an amine, is used to allow integration of active groups inside the framework, and not just as side chains. The resulting sorbents offer a potentially high concentration of active groups accessible to metal ions and a uniform distribution of these groups throughout the material. Several studies have already been reported using such intraframework organosilicas in the hope of attaining high capacity of heavy metal removal. In 2002, Mercier et al. first reported the use of an organosilica-based sorbent for metal ion adsorption, which was synthesized by adding 2–5 mol % of N,N’-bis[3-(trimethoxysilyl)propyl]-ethylenediamine (TMSEN) into tetraethyl orthosilicate. However, the Cu adsorption capacity reported for that system was relatively low (2 mg g ) due to a small concentration of amine groups present. A series of reports focusing on similar functional groups followed, but high capacities remained elusive. 21–24] A better performance (39 mg g 1 for Cu) was obtained by co-condensation of N-(2aminoethyl)-3-aminopropyltrimethoxysilane (up to 30 mol %) and bis(triethoxysilyl)ethane. However, in this case, the amine groups were grafted onto the silica surface and, thus, did not reflect real intra-framework metal ion adsorption. Based on the results above it is thus expected that organosilica including polysilsesquioxane-based sorbents can compete effectively in terms of sorption capacity only if a high concentration of active groups is integrated into the framework, while the porous network, usually indicated by the accessible surface area, is maintained. 25] To that end, Burleigh et al. and Tang et al. prepared poly(TMSEN)s in emulsions using either cationic or anionic surfactant templates. Unfortunately, they obtained materials with relatively low surface areas [Brunauer–Emmett– Teller (BET) surface area ~30–40 m g ] , which was attributed to the pore collapse during surfactant extraction. 26] Herein, we report a high capacity polysilsesquioxane sorbent based on TMSEN. In contrast to previous work, the new sorbent was synthesized using TMSEN as the sole precursor in a one-pot synthesis to obtain both a high amine loading and a high surface area, which is the first attempt of such a system for heavy metal ion removal. The sorbent exhibits a high adsorption capacity towards Cu and Pb ions. After metal adsorption the system can be readily regenerated to its full capacity. The sorbent shows high selectivity for Cu over Ni and Co. As such this new sorbent may be potentially useful in wastewater treatment, drinking water purification, and even soil remediation. The bis-amine bridged polysilsesquioxane was synthesized as shown in Figure 1. The amount of surfactant P123 and the water content controls both the cross-link-