Activated Carbon for CO₂ Adsorption from Avocado Seeds Activated with NaOH: The Significance of the Production Method

The rise in atmospheric greenhouse gases like CO₂ is a primary driver of global warming. Human actions are the primary factor behind the surge in CO₂ levels, contributing to two-thirds of the greenhouse effect over the past decade. This study focuses on the chemical activation of avocado seeds with sodium hydroxide (NaOH). The influence of various preparation methods was studied under the same parameters: carbon precursor to NaOH mass ratio, carbonization temperature, and nitrogen flow. For two samples, preliminary thermal treatment was applied (500 °C). NaOH was used in the form of a saturated solution as well as dry NaOH. The same temperature of 850 °C of carbonization combined with chemical activation was applied for all samples. The applied modifications resulted in the following textural parameters: specific surface area from 696 to 1217 m²/g, total pore volume from 0.440 to 0.761 cm³/g, micropore volume from 0.159 to 0.418 cm³/g. The textural parameters were estimated based on nitrogen sorption at -196 °C. The XRD measurements and SEM pictures were also performed. CO₂ adsorption was performed at temperatures of 0, 10, 20, and 30 °C and pressure up to 1 bar. In order to calculate the CO₂ selectivity over N₂ nitrogen adsorption at 20 °C was investigated. The highest CO₂ adsorption (4.90 mmol/g) at 1 bar and 0 °C was achieved.