Water Contact Angle Dependence with Hydroxyl Functional Groups on Silica Surfaces under CO2 Sequestration Conditions.
Functional groups on silica surfaces under CO2 sequestration conditions are complex due to reactions among supercritical CO2, brine and silica. Molecular dynamics simulations have been performed to investigate the effects of hydroxyl functional groups on wettability. It has been found that wettability shows a strong dependence on functional groups on silica surfaces: silanol number density, space distribution, and deprotonation/protonation degree. For neutral silica surfaces with crystalline structure (Q(3), Q(3)/Q(4), Q(4)), as silanol number density decreases, contact angle increases from 33.5° to 146.7° at 10.5 MPa and 318 K. When Q(3) surface changes to an amorphous structure, water contact angle increases 20°. Water contact angle decreases about 12° when 9% of silanol groups on Q(3) surface are deprotonated. When the deprotonation degree increases to 50%, water contact angle decreases to 0. The dependence of wettability on silica surface functional groups was used to analyze contact angle measurement ambiguity in literature. The composition of silica surfaces is complicated under CO2 sequestration conditions, the results found in this study may help to better understand wettability of CO2/brine/silica system.
Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology , Dalian 116024, P. R. China.
Cong
C
Chen
School of Petroleum and Chemical Engineering, Dalian University of Technology , Panjin 124221, P. R. China.
Ning
N
Zhang
Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology , Dalian 116024, P. R. China.
Weizhong
W
Li
Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, Dalian University of Technology , Dalian 116024, P. R. China.
Yongchen
Y
Song
D002245:Carbon Dioxide / Q000737:chemistry*; D057965:Carbon Sequestration; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical; D056004:Molecular Dynamics Simulation; D012492:Salts / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D017155:Wettability
D012492:Salts; C017082:brine; D014867:Water; D002245:Carbon Dioxide; D017665:Hydroxyl Radical; D012822:Silicon Dioxide