Determination of chemical oxygen demand in mixed organic solution by Ti/TiO2 nanotube array electrode method

Abstract

Chemical oxygen demand (COD) is a significant parameter for analyzing water quality. However, the detection methods still suffer from the problems of secondary pollution, use of harmful substances, complicated operations, etc. To trace these problems, a Ti/TiO2 nanotube array (NTA) electrode was successfully prepared by the secondary anodic oxidation method in this work. The prepared electrode was used to determine COD of single- and multi-component solutions (including aniline, rhodamine B, and potassium hydrogen phthalate). The Ti/TiO2 NTA electrode exhibited higher electrochemical oxidation efficiency than the neat Ti one. The electrocatalytic reactions of the target organics on the electrode surface were confirmed to conform to the first-order kinetic process. Within COD range of 5–150 mg/L, COD value was not only proportional to the anodizing current but also related to organic matter itself. The activation energies of electro-oxidation reaction of different substances were different from each other (An: 14.25 kJ/mol, RhB: 18.56 kJ/mol, and KHP: 35.32 kJ/mol), indicating the differences in their dynamic behaviors on the electrode surface. The related bias obtained for all successive measurements was below ± 5.8%. Therefore, we report a fast, effective, accurate, and well-reproducible COD detection method, which is feasible for both single-component and multiple-component organic solutions.

Rapid and Reliable Electrochemical Measurement of Chemical Oxygen Demand Using SnO2–Sb-Based Anodes

“…The practical application feasibility of the TF/Pt/SnO 2 –Sb anode for measuring COD was further confirmed using simulated organic wastewater (SOW) samples containing 15 typical organic compounds, which could be categorized as follows: , (1) chemicals commonly used in the standard test method for measuring COD, including sucrose, glucose, trisodium citrate, KHP, glutamic acid, mannitol, d -fructose, isopropanol, and glycine; (2) common pollutants in chemical and pharmaceutical wastewaters, including sodium acetate, salicylic acid, l -arginine, and benzoic acid; and (3) common intermediates in the oxidation of aromatic hydrocarbon organics, including oxalic acid and p -benzoquinone. As shown in Figure e, a gradually enhanced current response was achieved for a wide COD Th range from 100 to 10,000 mg L –1 .…”

“…The superior linear relationship over the range from 200 to 6000 mg L –1 ( R 2 = 0.998; Figure f) showed excellent electrochemical COD measurement of the TF/Pt/SnO 2 –Sb anode. In addition, the current responses of the SOW were more sensitive than those of the standard glucose sample, likely because of the different electrocatalytic oxidation kinetics toward different organics on the TF/Pt/SnO 2 –Sb anode . Overall, these results support our hypothesis that when loaded on a porous and exceptionally robust TF/Pt substrate, the SnO 2 –Sb electrocatalyst could be applied for measuring the COD.…”

Biological treatment methods of ship sewage: Case study

“…COD is used to measure levels of water contamination by organic matter, which is oxidized via an oxidizing agent (potassium dichromate) (Alrumman et al, 2016). COD is one of the most widely used indicators in water quality analysis (Abba & Elkiran, 2017;Li et al, 2021;Punmia et al, 2016). COD is an imperative parameter in analyzing water parameter quality, since it provides an index to assess the impact of discharge on the receiving water body (Abba & Elkiran, 2017;Punmia et al, 2016).…”