Stabilization of Carbon Dioxide Foam by a Low Concentration of Cetyltrimethylammonium Bromide-Grafted Nano-Faujasite Zeolite. Part 1: Experimental Study

In this work, we are introducing an innovative technique to enhance the CO2 foam stability by using a nanofoam stabilizer that reduces the surfactant concentrations below the critical micelle concentration (CMC). The core structure of our foam stabilizer consists of faujasite zeolite nanoparticles (FAU) that are grafted with cationic surfactant, cetyltrimethylammonium bromide (CTAB). The prepared nanomaterials were fully characterized by an array of characterization techniques to gain insight into their surface properties and stability. Then, the foamability and foam stabilization properties of the CTAB, compared with the physically mixed CTAB and neat FAU nanoparticles, and CTAB-grafted FAU nanoparticle systems were evaluated at various surfactant concentrations based on initial foam volume, half-life, liquid holdup, surface shear viscosity, and bubble sizes. Furthermore, the CO2 foam stabilization mechanisms of all foaming agents were investigated by the dilational surface tension. Our results indicated that the CTAB-grafted FAU nanoparticles were able to stabilize the liquid films of CO2 foam at low surfactant concentrations via surfactant coverage on the surface of nanoparticles, which optimized the viscoelastic and surface tension properties of CO2 foam. In fact, below the CMC of CTAB (∼335 ppm), the initial foam volume and half-life remained constant after the addition of the FAU nanoparticles, whereas the foam properties were highly enhanced above the CMC (350–3000 ppm). Our foam stabilization results showed that the optimum stable CO2 foam was generated by CTAB-grafted FAU nanoparticles at a concentration of 1000 ppm (∼500 ppm grafted CTAB), which had a half-life of 773 s, in contrast to the other systems that had a half-life of less than 350 s at 500 ppm CTAB concentration. The surface tension results showed that grafting 50 and 100 ppm CTAB on FAU nanoparticles resulted in 60.20 and 51.52 mN/m initial dynamic surface tension measurements, whereas the virgin CTAB solutions at the same surfactant concentrations had initial dynamic surface tensions of 69.78 and 60.44 mN/m, respectively. On the other hand, at a surfactant concentration of 50 ppm (100 ppm CTAB-FAU nanoparticles), the viscoelastic modulus was almost identical to the viscoelastic modulus measurement at the CMC of CTAB. Interestingly, the CTAB-grafted FAU nanoparticles, compared with the other systems, had almost 1.5–4 times higher liquid holdup and formed smaller and homogeneous bubble sizes during the first 360 s. Hence, the CTAB-grafted FAU nanoparticles could retard the foam destabilization mechanisms, including foam bubble coalescence and ripening effects, due to their ability to maximize the viscoelastic modulus and reduce the surface tension at these low surfactant concentrations. Our findings can provide an economical solution for implementing conventional CO2 foams in enhanced oil recovery (EOR) applications while hindering the agglomeration of nanoparticles.