Optimization of CO2 adsorption capacity and cyclical adsorption/desorption on tetraethylenepentamine-supported surface-modified hydrotalcite

The objective of this research was to investigate CO₂ adsorption capacity of tetraethylenepentamine-functionalized basic-modified calcined hydrotalcite (TEPA/b-cHT) sorbents at atmospheric pressure formed under varying TEPA loading levels, temperatures, sorbent weight to total gaseous flow rate (W/F) ratios and CO₂ concentrations in the influent gas. The TEPA/b-cHT sorbents were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT–IR), thermal gravimetric analysis (TGA), Brunauer–Emmet–Teller (BET) analysis of nitrogen (N₂) adsorption/desorption and carbon–hydrogen–nitrogen (CHN) elemental analysis. Moreover, a full 2⁴ factorial design with three central points at a 95% confidence interval was used to screen important factor(s) on the CO₂ adsorption capacity. It revealed that 85.0% variation in the capacity came from the influence of four main factors and the 15.0% one was from their interactions. A face-centered central composite design response surface method (FCCCD–RSM) was then employed to optimize the condition, the maximal capacity of 5.5–6.1 mmol/g was achieved when operating with a TEPA loading level of 39%–49% (w/w), temperature of 76–90°C, W/F ratio of 1.7–2.60 g·sec/cm³ and CO₂ concentration of 27%–41% (v/v). The model fitted sufficiently the experimental data with an error range of ± 1.5%. From cyclical adsorption/desorption and selectivity at the optimal condition, the 40%TEPA/b-cHT still expressed its effective performance after eight cycles.