Study On Electrochemical Dyeing System Of Indigo

Indigo is an important dye for denim fabric dyeing.Because it is insoluble in water,traditional dyeing often uses sodium dithionite?SD?as a reducing agent to reduce the dye to Indigo leuco that is easily soluble in water.The dyeing process is complicated,and a large amount of sulphates(SO₄^2-),sulphites(SO₃^2-)and thiosulphates(S₂O₃^2-)wastewater with deep color,large alkalinity and recalcitrance is generated,which increases the burden of sewage treatment.In order to overcome these problems,indirect electrochemical method with green environmental protection and easy automatic control is becoming one of the hotspots of current research.Previous studies have focused on complex systems of specific ferric salts and ligands,while little research has been done on using ferrous salts directly as a medium,and the available reduction potentials and irons under different valence iron ion complex systems.The structure-activity relationship and mechanism of action between ion self-conversion rate and indigo dye reduction rate and dyeing performance have not been studied.Based on above,this paper proposes an indirect electrochemical reduction dyeing of indigo dye with Fe?II?-sodium gluconate?DGS?-Abal B synergistic complexation system,and Fe?II?is directly used as a reduction medium.Indirect electrochemical dyeing of indigo dye can achieve rapid reduction of dyes and greatly improve electrochemical reduction rate and efficiency.The specific research contents and results are as follows:Abal B and sodium gluconate with strong alkali resistance and electrical conductivity are used as ligands to form a complex system with ferric ions and divalent iron ions,and different concentrations can be determined by orthogonal test combined with mean and range analysis.The effect of body on the stability of ligand complex?iron sulfate and ferrous sulfate complex value,CV value and turbidity?,and further optimization of each component in different valence iron ion complex systems by grey cluster analysis concentration.The results showed that the concentration of sodium hydroxide had the greatest influence on the complexing ability of ligand solution on divalent iron ions and the turbidity of complex solution;the effect of sodium gluconate concentration on the hard water stability of divalent iron ion complex solution maximum.The concentration of sodium gluconate had the greatest influence on the complexing ability of the ligand solution on the ferric ion and the turbidity of the complex solution;the sodium hydroxide concentration had the greatest influence on the stability of the hard water stability of the ferric ion complex solution.The electrochemical behavior of indigo in Fe-DGS-Abal B medium was studied by cyclic voltammetry.The results show that Fe?II?-DGS-Abal B system exhibits higher oxidation peak current and reduction peak current,and oxidation.The peak potential is shifted negatively and the reduction peak is shifted positively.The reduction peak current and the oxidation peak current of each system are increased after the addition of the dye,as the scanning rate increases,the redox peak current in the Fe?II?-DGS-Abal B system also increases.Indirect electrochemical reduction of indigo dyes was carried out by using iron salts with different valence states as media to form a synergistic complex system with different ligands.The effects of different concentrations of ferrous sulfate/ferric sulfate on the indirect electrochemical reduction performance of indigo are discussed.The results show that ferrous sulfate is used as medium and sodium gluconate.The ligand complex solution formed by Abal B as a ligand is more stable and the system has better reduction performance.Electrochemical reduction of indigo dyes was successfully achieved by using ferrous sulfate-sodium gluconate-Abal B synergistic complexation system as a medium.The effects of various factors on the oxidation peak current,dye reduction rate and K/S value during electrochemical reduction and dyeing were discussed by single factor experiments.The optimal electrochemical reduction conditions were as follows:indigo2.5 g/L,ferrous sulfate 10 g/L,sodium gluconate 8 g/L,Abal B 7 g/L,sodium hydroxide30 g/L,under this condition,the dye reduction rate of up to 90%.The optimal electrochemical dyeing conditions were:indigo 3.0 g/L,ferrous sulfate 14 g/L,sodium gluconate 10.5 g/L,Abal B 8.75 g/L,sodium hydroxide 35 g/L,electrolysis voltage 12 V,reduction time 40 min,the cathode electrode area 15 cm².Under these conditions,results comparable to conventional dyeing can be obtained.The indirect electrochemical reduction process of indigo blue in the Fe-DGS-Abal B synergistic complexing system was optimized by response surface methodology.The optimized indigo reduction rate was 91.4%.The optimized process was compared with the traditional process.The results showed that the K/S value of dyed cotton fabric reached 12.53 under the optimized electrochemical reduction dyeing process,which was9.43%higher than the traditional dyeing process,and the color fastness is basically consistent with the traditional dyeing process.The availability of the dyeing cycle of electrochemical reduction dyeing is obviously better than that of traditional dyeing process.When the reducing dyeing solution is used less than 5 times.The indirect electrochemical reduction dyeing K/S value does not change much,and can still be maintained above 10,and has excellent sustainable dyeing performance.Compared with traditional cotton dyed fabrics,electrochemical dyed cotton fabrics have less impurity on the surface of the fibers,which indicates that the Fe?II?-DGS-Abal B synergistic complex system is stable,so that more iron ions are in solution during the dyeing process.The indigo is reduced without being adsorbed onto the fibers along with the indigo for dyeing.Indirect electrochemical dyeing is more effective than traditional SD dyeing,and dyeing liquid is more susceptible to biological and chemical degradation.Among them,BOD decreased by 33.26%,COD decreased by 35.88%,and B/C reached 0.486,which has obvious environmental benefits.