Polyelectrolyte complex gels used for CO₂ absorption

Polymer gels have shown application potential in minimizing gas channeling during CO2 enhanced oil recovery and storage processes, but the pumping pressure of preformed gels was too high, and the in-situ cross-linking in reservoirs was uncontrollable. Here we developed polyelectrolyte complex gels through the columbic attraction between sodium carboxymethyl cellulose (NaCMC) and protonated polyethyleneimine (PEI+) by CO2 in the presence of water. Without CO2, the viscosity of polymer complex solution is relatively low; after streaming CO2, the viscosity of the NaCMC-PEI+ mixture aqueous solution increases significantly, forming a gel. It was also found that the complex solution shows an evolution of "sol-gel-separated phase" as the polymer concentration increases, which could be attributed to the enhanced electrostatic attraction between CMC- and PEI+. The viscosity of the gel decreases upon increasing salinity owing to the reduced charge repulsion by the introduced inorganic salt. The CMC--PEI+ complex can retain its gel behavior until 60 degrees C, after which the complex collapses. The uptake tests show that 11.34 mg CO2 can be absorbed by each gram of gel composed of 0.9 wt% NaCMC and 0.15 wt% PEI at room temperature and ambient pressure. This work provides an inexpensive route to control gas leakoff and improve CO2 absorption.