Amine-Functionalized Meso-Macroporous Polymers for Efficient CO2 Capture from Ambient Air.

Over the past decade, direct air capture (DAC) of carbon dioxide (CO2) using solid nanoadsorbents has garnered attention as a negative emission technology with high energy efficiency. Although operational, the large-scale deployment of DAC technologies has been significantly delayed due to the low performance and high cost of solid DAC nanoadsorbents. Herein, we present a novel family of meso-macroporous melamine formaldehyde (MF) materials with a facile preparation methodology, low capital cost, and unique physicochemical characteristics for DAC. The fabricated MF materials exhibit an extra-large pore volume of 5.19 cm3/g with a 24.6 nm average pore diameter. We show that the synthesized MF materials can be used as substrates and impregnated with different amounts of tetraethylenepentamine (TEPA) to act as chemical nanoadsorbents for DAC. Owing to the ultrahigh pore volume of MF, a substantial amount of 71 wt % TEPA (i.e., MF-TEPA71%) can be loaded, resulting in 2.65 mmol/g of CO2 uptake under DAC conditions. In addition, the superior physicochemical properties of MF lead to a high CO2 loading of 2.07 mmol/g with low TEPA loading in MF-TEPA33%. The prepared MF-TEPA nanoadsorbents can be successfully employed in different shapes (i.e., droplets, pellets, and coatings) and maintain their superiority across different temperatures and CO2 concentrations. This study provides a promising approach for developing meso-macroporous substrates through a straightforward and scalable synthesis method, representing a new avenue for the next generation of DAC nanoadsorbents with superior performance for practical applications.

Enhanced pollutant photodegradation over nanoporous titanium-vanadium oxides with improved interfacial interactions.

This study addressed the separation problem of colloidal catalytic powder from its solution and pore blockage of traditional metallic oxides by fabricating nanoporous composites of titanium (Ti)-vanadium (V) oxide via magnetron sputtering, electrochemical anodization, and annealing processes. The effect of V-deposited loading on the composite semiconductors was investigated by varying V sputtering power (20-250 W) to correlate their physicochemical properties to the photodegradation performance of methylene blue. The obtained semiconductors revealed circular and elliptical pores (14-23 nm) and formed different metallic and metallic oxide crystalline phases. Within the nanoporous composite layer, V ions substituted Ti4+, leading to Ti3+ formation accompanied by decreased band gap values and higher visible-light absorption. Thus, the band gap of TiO2 was 3.15 eV, while that of Ti-V oxide with the maximum V content (at 250 W) was 2.47 eV. The interfacial separators between clusters in the mentioned composite created traps disrupting the charge carrier movements between crystallites, thereby decreasing the photoactivity. In contrast, the composite prepared with the minimum V content showed approximately 90% degradation efficiency under solar-simulated irradiation resulting from the homogeneous V dispersion and the lower recombination possibility, owing to its p-n heterojunction constituent. The nanoporous photocatalyst layers with their novel synthesis approach and outstanding performance can be applied in other environmental remediation applications.

Upgrading the biogas production from raw landfill leachate using O3/H2O2 pretreatment process: Modeling, optimization and anaerobic digestion performance.

Here, a combined pretreatment oxidation process (O3/H2O2) was investigated to enhance the biodegradability of raw landfill leachate (RLL) and biomethane potential (BMP) in anaerobic reactors. The central composite design (CCD) and response surface methodology (RSM) were employed to optimize the operational parameters influencing on RLL bioavailability in O3/H2O2 process: pH, Oxygen Flow rate, Reaction Time, and H2O2 concentration. The findings revealed that the O3/H2O2 increased biodegradability index (BOD5/COD) of RLL from 0.41 to 0.68 under optimized condition (pH=8, Oxygen flow= 0.25 L.min-1, Reaction Time= 25 min, H2O2 concentration= 2.5 g.L-1). Furthermore, the effects of O3/H2O2 process on BMP of RLL were surveyed under mesophilic anaerobic reactors (Temperature: 37 ± 1 °C) in viewpoints of operational performance and methane yield in a batch mode for incubation period of 24 days. The results showed that O3/H2O2 process simultaneously improve the BMP by 2.99 times higher in a shorter lag-phase period (5 days) compared with control. The pretreatment O3/H2O2 and mesophilic anaerobic digestion process revealed a feasible and efficient method for enhance BMP of RLL.