Mercury Removal from Concentrated Sulfuric Acid by Electrochemical Alloy Formation on Platinum

Mercury is a highly toxic heavy metal, and improved removal processes are required in a range of industrial applications to limit the environmental impacts. At present, no viable removal methods exist commercially for mercury removal of aqueous solutions at high acidic conditions, such as concentrated sulfuric acid. Herein, we show that electrochemical mercury removal based on electrochemical alloy formation on platinum, forming PtHg4, can be used to remove mercury from concentrated sulfuric acid. Thin platinum film electrodes and porous electrodes with supported platinum are used to remove more than 90% of mercury from concentrated acid from a zinc smelter with an initial mercury concentration of 0.3-0.9 mg/kg, achieving high-quality acid (<0.08 mg/kg) within 80 h. The removal process is carried out in 50 mL laboratory-scale experiments and scaled up to a 20 L pilot reactor with retained removal efficiency, highlighting excellent scalability of the method. In addition, the removal efficiency and stability of different electrode substrate materials are studied to ensure high-quality acid and a long lifetime of the electrodes in harsh chemical conditions, offering a potential method for future large-scale mercury decontamination of sulfuric acid

Positioner with I/P-transducer as an option

Denna rapport beskriver ett projekt som startats på uppdrag av Lennart Proper, Aspervall Instruments AB. Projektet behandlar utvecklingen av Aspervalls pneumatiska ställdon, ASPEdonet och är en del av kursen Examensarbete för högskoleingenjörsexamen i Maskinteknik, MSGC17. Kursen omfattar 22,5 högskolepoäng och utfördes under vårterminen 2016 vid fakulteten för hälsa, natur- och teknikvetenskap, Karlstad universitet. Aspervall är ett företag beläget i Säffle som specialiserat sig på finmekanik, legotillverkning samt framtagning av egna produkter exempelvis ASPEdonet. ASPEdonet är ett pneumatiskt ställdon som är uppbyggt av en dubbelverkande pneumatisk cylinder med en lägesställare. En pneumatisk cylinder används för att omvandla gastryck till mekaniskt arbete genom förflyttning av en kolv med kolvstång i ett cylinderrör. Lägesställaren används för att reglera trycket till de olika sidorna av kolven med hjälp av en styrsignal. Syftet med examensarbetet var att vidareutveckla den pneumatiska lägesställaren så att den blev elektropneumatisk, det vill säga att den tidigare pneumatiska styrsignalen ersattes av en elektronisk analog styrsignal. Detta gjordes genom att installera proportionalteknik i lägesställaren i form av en I/P-omvandlare. I/P-omvandlare, som också kallas E/P-omvandlare eller proportionalventil, är en tryckregulator som används för att reglera lufttrycket proportionellt mot en elektronisk signal. Problemformuleringen för projektet var hur lägesställaren kunde kompletteras med en I/P-omvandlare utan att grundfunktionen eller designen av lägerställaren förändras. Projektet har följt produktutvecklingsprocessens olika faser, förstudie, produktspecifikation, idegenerering, konceptval och konfiguration med detaljkonstruktion. Resultatet av arbetet blev en dokumentation som kan användas som grund vid produktframställning och fortsatt produktutveckling. Lösningen som togs fram har samma grundkonstruktion och design som tidigare modell. Som I/P-omvandlare valdes Norgrens VP12 då den var tillräckligt kompakt för att monteras under huven på lägesställaren. Standard komponenter från Norgren och Nelco valdes som luftkopplingar och kabelgenomföring. Som en del i konstruktionsarbetet utformades en ny mer kompakt ventil för lägesställaren, ventilen tillverkas av en enhet.This report covers a project instigated by Lennart Proper, Aspervall Instrument AB. The report deals with the development of Aspervalls pneumatic actuator, ASPEdonet and it is a part of the course degree project of Bachelor of Science in Mechanical Engineering, MSGC17. The course covers 22.5 ECTS credits and it was accomplished during the spring term of 2016 at the faculty of health, natureand engineering, Karlstad University. Aspervall is a company located in Säffle that specialize in precision engineering, contract manufacturing and development of own products like ASPEdonet. ASPEdonet is a pneumatic actuator constructed of a pneumatic double-acting cylinder and a positioner. The pneumatic cylinder is used to convert air pressure into mechanical work through the moment of a piston with piston rod in a cylinder tube. The positioner is used to regulate the pressure to different sides of the piston with the use of a control signal. The thesis objective was to further develop the pneumatic positioner by converting it to electropneumatic, which means that the previous pneumatic control signal was replaced with a electronic analog control signal. This was accomplished through installing proportional technology into the positioner in the form of an I/P-transducer. I/P-transducer is also preferred to as E/P-transudcer or proportionalvalve, is a pressure regulator that is used to regulate air pressure proportional to an electronic signal. The problem definition of the project was how the positioner could be complemented with a I/P-transducer without compromising the basic function or the design of the positioner. The project followed the different stages of the product development process, pre-study, product specification, idea generation, concept selection and structure with detail design. The project resulted in a documentation that can serve as basis for product manufacturing and further development. The solution that was generated has the same basic construction and design as the previous model. Norgren VP12 was selected as I/P-transducer since it is compact enough to be integrated in the positioner. Standard components from Norgren and Nelco served as fittings and cable gland. A new more compact valve was designed as a part of the construction, the valve is manufactured from a single unit

Mercury Removal from Concentrated Sulfuric Acid by Electrochemical Alloy Formation on Platinum

Mercury is a highly toxic heavy metal, and improved removal processes are required in a range of industrial applications to limit the environmental impacts. At present, no viable removal methods exist commercially for mercury removal of aqueous solutions at high acidic conditions, such as concentrated sulfuric acid. Herein, we show that electrochemical mercury removal based on electrochemical alloy formation on platinum, forming PtHg4, can be used to remove mercury from concentrated sulfuric acid. Thin platinum film electrodes and porous electrodes with supported platinum are used to remove more than 90% of mercury from concentrated acid from a zinc smelter with an initial mercury concentration of 0.3–0.9 mg/kg, achieving high-quality acid (<0.08 mg/kg) within 80 h. The removal process is carried out in 50 mL laboratory-scale experiments and scaled up to a 20 L pilot reactor with retained removal efficiency, highlighting excellent scalability of the method. In addition, the removal efficiency and stability of different electrode substrate materials are studied to ensure high-quality acid and a long lifetime of the electrodes in harsh chemical conditions, offering a potential method for future large-scale mercury decontamination of sulfuric acid