In view of global warming caused by the uncontrolled emissions of CO2 to the environment, there is a great need to develop methods able to eliminate this pollutant. Apart from establishing new techniques, the exploration of new materials with high separation performance and low cost are of importance. This work aims to treat carbon‐metals‐rich chars originated from the fast pyrolysis of sewage sludge and wood sawdust to be used as CO2 adsorbents. The samples were washed with ethanol and dichloromethane before their physical and chemical activation to remove impregnated bio‐oil. For the chemical activation, potassium hydroxide and hydrochloric acid were used as agents. The samples were analyzed via BET, TGA, XRD, and XRF. The results were used to investigate the role played by ethanol or dichloromethane and the effect of the activation on the properties of the materials such as specific surface area, total specific pore volume, and average pore size. CO2 isotherms were obtained experimentally at 25 °C using a magnetic suspension balance and the data was used to estimate Langmuir and Freundlich isotherm parameters. After chemical treatment, the sewage sludge char specific surface area increased 11 times and had an adsorptive capacity of 1.32 × 10−3 mol/g. The wood sawdust char specific surface area increased 90 times and had an adsorptive capacity of 3.73 × 10−3 mol/g. Desorption was carried out from 5 × 105 to 1 × 105 Pa at 37 °C and the efficiencies were 89.0 and 84.4 % for the sewage sludge and wood sawdust, respectively.
The acid properties of palygorskite clay (R1) were studied using n-butylamine as probe molecule. A comparison was made of these properties in palygorskite clay (R1), in an acidified palygorskite (R2) and in acid palygorskite loaded with 2% of lanthanum (R3). The total acid properties were determined by FTIR (Fourier Transform Infrared) and TG-DTA (thermogravimetry). The acidity increased as follows: R3>R2>R1. The acid strength sites were classified as physisorbed, weak, medium and strong. The acid treatment did not change the site distribution, apparently only removing channel impurities. The introduction of lanthanum created many more acid sites and increased the specific area. Both weak and strong sites, which increased significantly, were considered new active acid sites produced by the lanthanum
Lignocellulosic biomass is the most abundant biological resource on the planet and has been extensively researched to produce cellulosic ethanol. However, there is a consensus that the presence of lignin hinders the biomass conversion. Lignin is often considered a villain in cellulosic ethanol production studies due to its adverse effects on cellulases and yeasts. Despite this, recent studies indicate that lignins can be transformed into useful inputs to produce cellulosic ethanol. These approaches aim to establish closed-loop biorefineries to improve economic metrics and reduce the environmental impact due to the substitution of products based on fossil sources. The present review addresses the successful cases in transforming lignin into chemicals and materials to increase cellulosic ethanol titers. A contextualization was first carried out, considering aspects of biomass characteristics and lignin valorization. The impact of lignin-based chemicals and materials in the pretreatment, detoxification, and enzymatic hydrolysis steps was discussed in detail. Economic aspects and future perspectives were also included in this review. These reports open a new point of view on lignin valorization and its integration with the cellulosic ethanol production chain.
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