Chemometric study on the electrochemical incineration of nitrilotriacetic acid using platinum and boron-doped diamond anode

Zhang, Chunyong; He, Zhenzhu; Wu, Jingyu; Fu, Degang

doi:10.1016/j.chemosphere.2015.02.018

Cited by 7 publications

(1 citation statement)

References 32 publications

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“…The concentration of boron in the film was 8000 ppm, and the average diameter of the diamond grains was about 20-50 μm. 15 Analytical apparatus and calculations.-Quantitative analysis of BPB dye was performed by UV visible in a Shimadzu UV-1800 spectrophotometer set at 592 nm (maximal absorption wavelength). All experiments were carried out at least in duplicate.…”

Section: Methodsmentioning

confidence: 99%

The Peculiar Roles of Sulfate Electrolytes in BDD Anode Cells

Zhang

et al. 2015

J. Electrochem. Soc.

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Taking bromophenol blue as pollutant model, the role of sulfate electrolytes during the anodic oxidations was investigated in a wide range of concentrations (0.1-500 mM). Trials were performed with an electrochemical cell containing boron-doped diamond anode and stainless steel cathode. The impact of sulfate concentration on the degradation performance was assessed by comparing the color removal efficiencies at various time intervals. The results revealed a significant and peculiar influence of this parameter on the degradation efficiency. Thus, we emphasize the importance of selection of operating levels in electrolytic oxidations, especially when certain activators (from the cathode) may be formed in the treated solutions.Using boron-doped diamond (BDD) anodes to mineralize biorefractory organic pollutants has been one of the most active areas of research interest in environmental electrochemistry within the last decade. 1 Specifically, the rate and efficiency of BDD technology are strongly dependent on the employed supporting electrolytes. 2-4 So far, various electrolytes like NaCl, Na 2 SO 4 , Na 2 CO 3 , Na 3 PO 4 and NaNO 3 have been evaluated for the electrochemical destruction of organic pollutants, and Na 2 SO 4 has often been reported to be the most effective one regarding degradation improvements. 5,6 As is known, sulfate electrolyte exhibits many advantages, such as low price, high electrical conductivity, and low reactivity on both anode and cathode. Hence, it is generally recognized as an inert electrolyte which solely serves as a conducting media. However, in BDD anode cells, the presence of sulfate electrolyte (>20 mM) may lead to the formation of persulfate ions (S 2 O 8 2− ), which will spread to the bulk solution and participate in the oxidation reactions. 7 In this scenario, the effects of sulfate electrolyte on the electrochemical oxidation of organics had previously been investigated by many researchers. [8][9][10][11][12] As a result, in these studies, the sulfate concentration demonstrated either positive or inapparent effects. However, quite different observations were recently obtained by our research group in studying the degradation of bromophenol blue (BPB) and Acid Orange-II with BDD anodes. 13,14 In these two studies, increasing sulfate concentration will result in a significant decrease of the degradation efficiency. This phenomenon is explained by the hypothesis that sulfate ions of higher concentrations may block the active sites of BDD surface and thus reduce the efficiency of •OH formation (the blocking effect).Since differing effects of sulfate electrolyte have been reported by various researchers, there is an urgent need for their better clarifications. In this scenario, we report here the first comprehensive investigation on the impacts of sulfate concentration during the BDD anodic oxidations. BPB, a biorefractory dye pollutant, extensively used in textile industries and college laboratories, was employed as a pollutant model (see Fig. 1). As expected, the results obtained ...

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Section: Methodsmentioning

confidence: 99%

The Peculiar Roles of Sulfate Electrolytes in BDD Anode Cells

Zhang

et al. 2015

J. Electrochem. Soc.

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Statistical investigation on the role of supporting electrolytes during NTA degradation on BDD anodes

et al. 2015

Environ Sci Pollut Res

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This work reported a comparative study on the electrochemical incineration of nitrilotriacetic acid (NTA) in the presence of different supporting electrolytes (Na2SO4 and NaCl). Galvanostatic electrolyses were conducted in an undivided electrochemical cell containing boron-doped diamond (BDD) anode and platinum cathode. Initial solution pH, flow rate, applied current density, and supporting electrolyte concentration were selected as variables, besides the mineralization efficiency of NTA that was selected as response. Central composite rotatable design and response surface methodology were employed here to examine the statistical significance of the selected variables, as well as to determine the optimal conditions of the degradation process. Under the same operating conditions, two regression models were thus constructed to illustrate the differing impact of supporting electrolytes in BDD anode cells. The kinetics for NTA degradation followed different reaction orders for the two scenarios (in the absence and presence of NaCl), indicating the complex interaction between hydroxyl radicals and active chlorine. Despite this, the experimental results demonstrated that effective mineralization of NTA might also be achieved in the presence of chlorides (of lower concentrations). Besides, in the case of chlorides, the average mass transfer coefficient of the system was found to be strongly dependent on the initial solution pH. Lastly, a plausible reaction sequence concerning the electrolytic oxidation of NTA in chloride media was also proposed.

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