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Since CO2 is an important component of gas emissions, its removal from gas streams is of the utmost importance to fulfill various environmental requirements. The technologies used to accomplish this removal are based mainly on absorption, as well as adsorption and membrane processing. Among the materials used in the above separation processes, materials in nano forms offer a potential alternative to other commonly used macromaterials. The present work reviews the most recent publications (2023) about CO2 capture using different nanomaterials, and whilst most of these publications were dedicated to investigating the above, several presented data on the separation of CO2 from other gases, namely nitrogen and methane. Furthermore, a number of publications investigated the recyclability of nanomaterials under continuous use, and just three of the references were about computational modeling; all others were experimental papers, and only one reference used a real industrial gas. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Biorefinery processes utilize carbohydrates from biomass in order to produce biochemical and biomaterials. Lignin as the byproduct after biorefinery needs to be studied for applications. This study evaluated how hot water pretreatment, a typical biorefinery process, will impact on the heavy metal adsorption capacity of lignin. RESULTS: Paulownia elongata acid insoluble lignin was tested for its heavy metal adsorption capacities for Pb(II), Cu(II) and Cd(II). Hot water pretreatment was conducted on the lignin with both water and dilute acetic acid solution. Samples with both increased and decreased adsorption capacity were observed after the pretreatment, while samples with long duration of pretreatment encountered a substantial loss in the adsorption ability. Depolymerization and condensation lignin reaction schemes under acidic environment were summarized and applied to explain the capacity changes. NMR analysis was performed to quantify the functional groups in the lignin samples. Changes in the amount of functional groups were found in the samples after pretreatment. CONCLUSION: Hot water pretreatment can either increase or decrease the adsorption capacity of lignin depending on the treatment duration. Lignin byproducts after treatment under acidic and high temperature environments with long duration is no longer suggested for use as a heavy metal adsorbent. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]