Electrochemical Reduction Of Vat Dyes

Electrochemical reduction of vat dyes（including indigo） and sulfur dyes is a new attempt for new dyes method.Based on the research and development of synthesis of the electrochemical reduction as a research direction,and to Sulfur Black 2BR 200% for raw materials,the reduction behavior on silver and silver-plated graphite electrode was mainly studied.ChapterⅠdiscussed the character,sort and property,the new dyes methods and technology nowadays,the electrode materials applications were also discussed. Provide background for the research.ChapterⅡfocuses on the experiment contents and methods.In chapterⅢ,electrochemical reduction behavior of Sulfur Black on silver electrode was discussed.The cathodal reduction behavior,the reaction kinetics and course of Sulfur Black were carried out a detailed study by cyclic voltammetry and linear sweep voltammetry.The influences of scan rate,concentration,pH and temperature on the electrochemical behavior of Sulfur Black were discussed.The results showed that:（1） Silver electrode had electro-catalytic activity to Sulfur Black in different electrodes（stain steel,copper,graphite,silver,platinum）,and i_p in silver electrode was higher activity than i_p in other electrodes;（2） The influence of silver activated was less to electrochemical reduction for Sulfur Black,the reduction peak current increased gradually and peak potential shifted more positive with increasing scan rate,the reduction peak current increased gradually with increasing Sulfur Black concentration,the reduction peak current increased gradually with increased temperature,decreasing NaOH concentration was not furthersome to electrochemical reduction for Sulfur Black.（3） In NaOH solution,It was found that it was more electrochemical reducible on silver electrode than Na₂CO₃ and Na₂SO₄ under the same condition,but the influence was slight,and the low cost of NaOH,so it use NaOH solution as ground electrolyte in industrialized production.In chapterⅣ,the morphology of graphite electrode and silver-plated graphite electrode the electrochemical behaviors and kinetic characteristics of aromatic compounds on the two kind electrodes are studied by the methods of SEM,EDS and electrochemical test techniques etc.Current-controlled electrolysis experiments were carried out on graphite and silver-plated graphite electrode was mainly studied.The effects of Sulfur Black concentration,current and the reaction temperature were investigated with an orthogonal experiment.The results show that:（1） Accord to EDS,the smaller the particle size of silver can plate graphite electrode well,better catalytic effect.（2） The influence of silver activated was less to electrochemical reduction for Sulfur Black,the reduction peak current increased gradually and peak potential shifted more positive with increasing scan rate.In NaOH solution,it was found that it was more electrochemical reducible on silver electrode than Na₂CO₃ and Na₂SO₄ under the same condition,but the influence was sligh;high NaOH concentration was furthersome to electrochemical reduction for Sulfur Black.（3） Very excellent current efficiency（92.2%） can be gained in the following reaction condition:silver-plated graphite used as cathode; temperature is about 27℃,current density is 6.25 mA·cm^-2;pH of electrolyte is 14. （4） When the Sulfur Black concentrations were 40～80 g/L,the temperature of reduced were 30～60℃,the current was 0.55～0.75 A,and the ground electrolytes were 0.5 mol·L^-1 NaOH、0.25 mol·L^-1 Na₂CO₃、0.25 mol·L^-1 Na₂SO₄,the optimized result was obtained,with more than 90%current efficiency.