Jurusan Teknik Kimia, Fakultas Teknik, Universitas Muhammadiyah Surakarta
Jl A Yani Tromol Pos 1 Pabelan, Kartasura 57102 Telp 717417 psw 248
The application of closed system pulp and paper mill generates problem on accumulation of metal in the cycle. In some mill, CO2 effluent is used to remove the accumulated metal by acidification. Dissolved CO2 forms carbonic acid that provides proton to exchange with the metal ions attached to pulp fibres. Despite of the application of CO2 acidification for metal removal in pulp mills, the study of the kinetics of CO2 acidification, particularly at the condition similar to the condition in the pulp mill, has not been done yet. This study investigated the kinetics of carbonic acid formation by dissolved CO2 in water in a bubble reactor a well as its equilibrium. From the experiment it was found that the rate of formation of carbonic acid was affected by agitation speed and CO2 flow rate. CO2 acidification was very fast, where the equilibrium of the acidification was achieved within several minutes. However, the CO2 acidification was only applicable for pH>4 at atmospheric pressure due to its limitation on CO2 solubility and dissociation of carbonic acid. The rapid acidification requested an adequate mixing with Re>104 that gives Np of 4. The volumetric mass transfer coefficient of the CO2 acidification at the particular conditions was in the range of 0.0005-0.0083 s^-1.