الهام مهرابي

Due to the increasing concentration of carbon dioxide in the atmosphere an‎d its role in global warming, the development of an adsorbent with high adsorption capacity, low regeneration energy, an‎d good cyclic stability is of great importance. In this study, alumina aerogel was first synthesized, followed by the synthesis of metatitanic acid. Subsequently, an alumina–metatitanic acid composite was prepared to create a stable structure with suitable surface properties. The surface of the composite was then modified with piperazine. Among the prepared samples, AA-MT/PZ10 containing 10 wt% piperazine was selec‎ted as the optimum adsorbent, showing an improvement of approximately 14.6% in adsorption performance.The structural an‎d morphological characteristics of the adsorbents were eva‎luated using XRD, FTIR, BET, FESEM, an‎d TGA analyses. To optimize the adsorption conditions, the Design of Experiments (DOE) approach an‎d Response Surface Methodology (RSM) based on Central Composite Design (CCD) were employed. The results indicated that increasing pressure enhanced the adsorption capacity, whereas increasing temperature reduced it, confirming the exothermic nature of the adsorption process. Statistical analysis also verified the good fit of the developed model.Equilibrium an‎d kinetic studies demonstrated that the Langmuir isotherm model provided the best fit to the experimental adsorption data, while the Avrami kinetic model showed the best agreement with the kinetic results, indicating monolayer adsorption an‎d the multi-step nature of the adsorption process. Thermodynamic analysis confirmed that the adsorption process was both exothermic an‎d spontaneous.In the cyclic regeneration analysis, the modified sample retained 92.28% of its initial adsorption capacity after five adsorption–desorption cycles, demonstrating good stability of the adsorbent. Regarding the adsorption mechanism, adsorption in the pristine sample was mainly physical, resulting from van der Waals forces an‎d pore filling. In contrast, in the modified sample, in addition to physical adsorption, acid–base interactions occurred between CO₂ molecules an‎d amine groups. Therefore, the adsorption mechanism in AA-MT/PZ10 can be described as a physico-chemical process, which is responsible for the enhanced adsorption capacity.Overall, surface modification with piperazine strengthened the physico-chemical interactions an‎d improved the CO₂ adsorption performance, making this composite a promising adsorbent for carbon dioxide capture.

اروژل آلومينا-متاتيتانيك‌اسيد , پيپرازين , اصلاح سطح , جذب دي‌اكسيدكربن

alumina aerogel–metatitanic acid , piperazine , surface modification , Carbon dioxide adsorption

Elham Mehrabi

Dr. Shahrukh Shah Hosseini