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ePaper created 2016-03-17, 15:06:18 | version 1.45.01
102 ELECTROLYTIC GENERATION OF HYDROGEN PEROXIDE Christiane Chaumette, Carsten Pietzka, Behnam Parwizi, Thomas Scherer Decentralized production of H2O2 Hydrogen peroxide, which is a platform chemical with a wide range of applications, is produced commercially in centralized chemical plants today. Areas of application are, for example, pulp and paper processing and water treatment, as well as applications with smaller consumption volumes such as plant and surface disinfection in food processing facilities and hospitals. When hydrogen peroxide is transported it is classi- fied as a ha ardous good, so transportation is cost-intensive, which will burden its use in future. That is why, together with industrial partners, Fraunhofer IGB has developed a concept for producing hydrogen peroxide on-site and by using electric power and an electrochemical cell. The decentralized production of hydrogen peroxide in con- centrations and volumes below the explosion threshold is at- tractive for two reasons. On the one hand, this option reduces the risk and cost of transportation, storage and handling; on the other, electrolytic generation from electricity allows for a fle ible operation of the production process This will be es- pecially cost-effective in future when surplus electricity could be used to balance out peaks of power supply to the grid as a consequence of intermittent, regenerative power generation. The electrolytic generation of hydrogen peroxide for water treatment was demonstrated with landfill leachate in the research pro ect O floc Integrated water treatment in a one-stage oxidative-adsorptive process to degrade and remove harmful substances”, which is funded by the European Union. In this project a treatment process was developed that accomplishes oxidative and adsorptive removal of pollutants from landfill leachate in one treatment step by combining two electrolytic processes. For demonstration, power from solar cells was used in the demonstration plant for the treatment of the leachate. Electrolytic cell for various applications The electrolytic cell developed at I B has a controlled flow across the area of the electrodes (Fig. 2). Oxidation reactions occur at the anode and the pH value decreases while, cath- odically, at a gas diffusion electrode converting oxygen and protonated water molecules, a hydrogen peroxide solution is produced and oxygen as well as protons are consumed. In initial trial runs with the addition of oxygen, concentrations of > 400 mg/L hydrogen peroxide (Fig. 1) were achieved in sodium sulfate solution (50 mM). With air supplied, H2O2 concentrations of 50 mg/L were attained with an energy requirement of 10 kWh/kg H2O2. The cell is operating with a continuous flow there is no recirculation of the solution Modular designed systems incorporating these cells can be fle ibly ad usted to the customer s individual need for hydro- gen peroxide. The pH value and the concentration of the solution can be ad- justed by selecting the process conditions (divided/undivided electrolytic cell, volume flow and composition of the solution, current density and temperature) and of the electrode materi- al. This allows for an energy-optimized treatment of the water flow and enables it to be reutili ed within the framework of the integrated water management of industrial processes. 1 CHEMISTRY H2O2concentrationinmg/L atthroughput10L/h current density in A/m2 0 100 200 300 400 500 600 700 450 0 50 100 150 200 250 300 350 400 0100200300400500600700