The methane–water kLa was determined by using gassing-out
method, as described in previous studies [13,19,20]. The concentration of methane in aqueous solution (CL) was determined based
on average value of triplicate measurements by gas chromatography (ACME 6100, Young Lin Instruments Co., Korea). The overall
volumetric mass transfer rate (R = M/h) for a liquid during the gas
transfer process in a solution can be described as: