Acidic surface chemical modification of biomass combustion ash-derived activated carbon for CO2 adsorption
Mikhail Gorbounov, Ludivine Hecquet-Perrot, Svetlana Ignatova, Peter Hewitson, Salman Masoudi Soltani
Abstract
To maximise the output and optimise a given adsorbent-adsorbate system, tailoring the material to the specific task at hand is a prominent approach. In the context of CO 2 adsorption, terminal amine groups are most common due to their exceptional affinity towards carbon dioxide. However, other methods involving introduction of alternative functionalities are often overlooked despite providing major benefits: e.g. cost-effectiveness of sorbent production and regeneration, thermal stability and etc. On these grounds, a physically activated carbon has been chemically modified with a mixture of nitric and sulphuric acid to introduce novel acidic functional groups to facilitate CO 2 adsorption. The experimental campaign was conducted by employing a randomised Box-Behnken design, evaluating the modification time and temperature as well as the ratio at which the acids (of different concentrations) have been mixed. CO 2 uptake was maximised (0.96 mmol/g at 50 °C) when treating the sorbent for 3 hours at 90 °C with 1 molar acids at a volumetric HNO 3 /H 2 SO 4 ratio of 1:2. Successful grafting of the nitro group was confirmed via spectroscopic studies, increased nitrogen content as well as other indicators. The sample was shown to possess a high working capacity, losing less than 5 % of its original uptake even after 40 adsorption-desorption cycles. As such, nitration of the surface may be viewed as a novel yet cost-effective surface modification method in the context of CO 2 adsorption. • Tailoring adsorbents for a target molecule maximises performance. • Activated carbon’s surface was chemically modified to facilitate CO 2 adsorption. • Novel acidic treatment purified the material and added NO 2 groups simultaneously.