Synthesis of N-doped materials from oily sludge solid particles for CO2 adsorption application.

In response to rising human-induced CO₂ emissions, various carbon capture technologies have emerged in recent years. Therefore, the synthesis of new carbonaceous adsorbent materials from waste, with the additional aim of reducing their environmental impact, appears to be a promising alternative. Refinery oily sludge coming from API separator was used as feedstock to synthetize porous carbon materials, due to its high content on solid particles composed mainly by carbon and oxygen (25 and 20 wt.%). The influence of some parameters have been studied, such as KOH:waste mass ratio, temperature activation rate, as well as nitrogen doping using urea. The results demonstrate that ultramicroporosity plays a key role in CO 2 adsorption capacity, reaching a maximum CO 2 capture of 3.85 mmol/g at 0°C for the material activated using 1:1 KOH:waste ratio and 2 °C/min of temperature rate (ACT1-R2). Furthermore, the doping of nitrogen increases the selectivity of CO 2 capture, reaching out 4.12 mmol/g at 0°C for the material ACT1-R2-U1, and also showing excellent reusability after several cyclic tests. However, it is important to note that excessive amount of nitrogen may cause pores to collapse, reducing their ultramicroporosity. The synthesis of these oily sludge derived materials with CO 2 adsorption capacity provides new strategies for the recovery of this type of waste. In this way, by following this strategy, it is possible to fully recover this refinery residue, achieving the goal of zero waste. • Mild activations conditions are better for the formation of narrow micropores. • Ultramicroporosity is a key parameter for CO 2 adsorption, favouring the materials capacity. • The N-doping of carbon materials increases the selectivity of CO 2 capture. • Fractional recovery of oily sludge allows the solid fraction to be converted into adsorbent carbons.