Electrochemical Preparation of Polyaniline Nanowires with the Used Electrolyte Solution Treated with the Extraction Process and Their Electrochemical Performance

Abstract

Electrochemical polymerization of aniline is one of the most promising methods to prepare polyaniline (PANI) materials. However, during this process, the electrolyte solution must be replaced after electropolymerization of a certain time because of the generation and the accumulation of the by-products, which have significant effects on the morphology, purity and properties of PANI products. Treatment and recycling of the used electrolyte solution are worthwhile to study to reduce the high treatment cost of the used electrolyte solution containing aniline and its polymerization by-products. Here, the composition of the used electrolyte solution was separated and determined by high performance liquid chromatography coupled with diode array detection (HPLC-DAD) in the range of ultraviolet and visible (UV-Vis) light. The analysis results revealed that the used electrolyte solution consisted of aniline, p-hydroquinone (HQ), p-benzoquinone (BQ), co-oligomers of aniline and p-benzoquinone (CAB) and acid. Then, n-octanol and 2-octanone were selected as extracts to remove HQ, BQ and CAB from the used electrolyte solution. Following that, the recycled electrolyte solution was prepared by adjusting the concentration of aniline and acid of the aqueous phase, and the electrochemical polymerization process was conducted. Finally, the obtained PANI was characterized by scanning electron microscope (SEM) and electrochemical methods. The experimental results clearly demonstrate that the morphology and specific capacitance of PANI produced from the recycled electrolyte solution can be recovered completely. This research paves the way for reusing the used electrolyte solution for aniline electrochemical polymerization.

Photocatalytic and Oxidative Synthetic Pathways for Highly Efficient PANI-TiO2 Nanocomposites as Organic and Inorganic Pollutant Sorbents

“…More interestingly, the electrochemical preparation of PANI has been extensively explored. This latter method represents the best approach to produce PANI films characterized by a fine control of thickness and morphology [18]. However, electrochemical syntheses show lower production yield than chemical oxidation, do not permit the production of complex polymer-inorganic composites, and present difficulties in scale-up [18,19].…”

“…This latter method represents the best approach to produce PANI films characterized by a fine control of thickness and morphology [18]. However, electrochemical syntheses show lower production yield than chemical oxidation, do not permit the production of complex polymer-inorganic composites, and present difficulties in scale-up [18,19]. In order to achieve high production yields, long-term electropolymerization is needed: this procedure leads to the accumulation of by-products including p-benzoquinone, p-hydroquinone and co-oligomers of aniline and p-benzoquinone and acid [18].…”

“…However, electrochemical syntheses show lower production yield than chemical oxidation, do not permit the production of complex polymer-inorganic composites, and present difficulties in scale-up [18,19]. In order to achieve high production yields, long-term electropolymerization is needed: this procedure leads to the accumulation of by-products including p-benzoquinone, p-hydroquinone and co-oligomers of aniline and p-benzoquinone and acid [18]. Besides their significant side effects on the properties of the final product, the discarded electrolyte solution is highly pollutant.…”

Some Important Issues of the Commercial Production of 1-D Nano-PANI

“…Through the polymerization process, hydrolysis reaction always takes place and BQ generate by hydrolysis of imines parts of PANI. The formed BQ will react with the amine group of aniline, aniline oligomers, and PANI through Michael addition reaction [30,31,32]. The by-products—including co-oligomers of aniline and p -benzoquinone (CAB), BQ, and hydroquinone (HQ)—generated during this reaction will accumulate through side reactions (Scheme 2) [32].…”

“…This process, resulting in composition of the discharged waste liquid, is very complex. The composition of the waste liquid which was generated by electrochemical polymerization of 1-D nano-PANI was characterized by high performance liquid chromatography coupled to photodiode diode array detection (HPLC–DAD) and ultraviolet and visible (UV–vis) spectrophotometer, and the chromatograms were shown in the Figure 1 [32]. In the HPLC chromatograms, the peaks 1 to 7 belong to HQ, BQ, aniline, N -phenyl-1,4-benzoquinonediimine (PBQD) [33,34], and N -phenyl-1,4-benzoquinonemonoimine (PBQM) [35], p -aminodiphenylamine (PPD) [36], 2,5-dianilino- p -benzoquinone (DABQ) [37], and Peaks 8 and 9 belong to the CAB with larger molecular weight which has similar structure with DABQ.…”