Gas bubble generation

In the cathodic scan in cyclic voltammetry, gas bubble generation was seen around 0.9 and 0.2 V, and the cathodic current increased simultaneously. This gas generation was considered to be Hj generation by electrochemical reduction of moisture in the bath. 

The sequence of potentiostatic electrolysis at 0.7 V for a few tens of minutes and cyclic voltammetry was repeated. The cathodic current at 0.7 V in the cyclic voltammogram lowered almost linearly with the total quantity of electricity by the potentiostatic electrolysis, and the generated gas bubbles decreased consequently. This result indicates that the residual moisture was eliminated electrochemically. 

The H2 generation was not prevented by Li deposition at lower potential, namely Li deposition occurred competitively with the H2 generation. However, the ratio e v defined by Equation 2.4.1 was seriously deteriorated by LiOH addition. The shape of the deposited Li changed to small spheres by LiOH addition. The change in the shape might affect the ratio to some extent. 

By Li20 addition, conspicuous gas generation was not seen in the cathodic scan in the cyclic voltammetry, which is consistent with the results and discussion above for LiOH addition. Meanwhile, it is noted again that the cathodic current density decreased considerably with Li20 addition. 

The cathodic phenomena in Li electrolysis in a LiCl-KCl eutectic melt were studied. Two types of metal fog formation were observed, but their influence on the efficiency of Li deposition was limited. It was confirmed that some cathodic reactions of residual moisture in the bath occurred in the bath and gas bubbles of H2 were generated. The reduction of residual moisture was competitive against the Li deposition, so that the efficiency of Li deposition was directly influenced by it. 

---

Fig. 28. Positions of two coaxial gas bubbles generated subsequently at the same orifice together with the distribution of the relative (i.e., with respect to the velocity of the leading gas bubble) liquid phase velocity.

Heim A., Rzyski E., Stelmach ]., Diameters of gas bubbles generated by self-aspirating mixers, Chem. and biochem. Quart. 11 (1997) 3, p. 143-146... 

The fixed bed reactor, behaving as a plug flow reactor, is most often used for immobilized enzyme reactions. Typically, the reactor is used with an upward direction of the flow to avoid compression of the bed and to release gas bubbles generated during the reaction. Reactor design may be done readily without knowing the detailed enzyme kinetics. Kinetic measurements are performed with a recirculation reactor and the data are plotted in the form 1/v = f(%) (see above). From this plot, the residence time necessary to reach a desired conversion x can be calculated as described. The different enzyme concentrations in the recirculation reactor and in the plug flow reactor have to be considered. 

Another approach for on-line degassing of solutions is to use a standard sandwich type gas-diffusion separator. One of the ports of the acceptor channel is blocked and the other connected to a vacuum source or to a pump which evacuates the gas from the channel. Such an arrangement was used by Hinkamp and Schwedt [13] in the determination of total phosphorus in waters with amperometric detection to remove gas bubbles generated in the reaction stream after an on-line continuous digestion in a microwave oven. 

Makuta, T., F. Takemura Simulation of micro gas bubble generation of uniform diameter in an ultrasonic field by a boundary element method, Phys. Fluids 18, 108102 (2006). 

Electrolyte based acid mist abatement technology is focused on surfactants. Surfactants are added to electrolytes to produce a foam layer at the electrolyte surface and suppress acid mist. Foam is generated at the electrolyte surface as oxygen gas bubbles generated at the anode are released from the electrolyte to the environment Foams stabilize and prolong the life of bubbles at the electrolyte-air interface and thereby allow electrolyte to drain away from the bubble surface and hence reduce acid mist. 

As a final step, the surfaces of the membranes can be coated with hydrophilic inorganic porous layers, so as to enhance the release of the gas bubbles generated in the electrolysis cells. 

Wastewater can be treated by several physical processes. In some cases, simple density separation and sedimentation can be used to remove water-immiscible liquids and solids. Filtration is frequently required, and flotation by gas bubbles generated on particle surfaces may be useful. Wastewater solutes can be concentrated by evaporation, distillation, and membrane processes, including reverse osmosis, hyperfiltration, and ultrafiltration. Organic constituents can be removed by solvent extraction, air stripping, or steam stripping. 

Porosity through thin dielectric films on metallic substrates may be measured by corrosion (liquid gas), selective chemical dissolution (electrographic printing - solution analysis), electrochemical decoration, anodic current measurement, gas bubble generation (electrolytic), liquid crystal (electric field) effects, and absorption (dyes - liquid or gaseous radioactive material). 

---