Toc5050a analyzer

Decolorization was calculated from the initial dye concentration and dye concentration at time t (C₀ and C_t, respectively) by measuring the absorbance at the visible maximum absorption wavelength (583 nm for RB5 and 617 nm for Rb7). Decolorization (D) was reported in %:

Absorbance measurements were carried out with a UV–vis spectrophotometer (Shimadzu UV-2401 PC, Kyoto, Japan). In the working range, the dye absorbance (Abs) has a linear behavior versus the dye concentration (conc), according to the Equations (2) and (3):


The total organic carbon (TOC) was determined with a Shimadzu TOC5050A analyzer (Kyoto, Japan). The % degradation was calculated according to Equation (4).

where TOC₀ corresponds to the initial value and TOC_t is the value at time t.
In accordance with our previous studies [28 (link)], the dye degradation follows a first-order reaction with an electrochemical treatment. The discoloration rate constants (k_D) were calculated from the slope of the semilogarithmic plot of absorbance versus treatment time (t) following the kinetic Equation (5).

The mineralization rate constants (k_M) were calculated from the slope of the semilogarithmic plot of TOC versus treatment time (t), in accordance with Equation (6).

In the field, water temperature, pH, electrolytic conductivity, dissolved oxygen (DO), and saturated dissolved oxygen (SDO) were measured using Hach Lange probes. The concentrations of total organic carbon (TOC), dissolved organic carbon (DOC), and inorganic carbon (IC), as well as total nitrogen (TN) and dissolved nitrogen (DN) were determined in the laboratory using a high-temperature catalytic combustion method in a Shimadzu TOC-5050A analyzer (Kyoto, Japan).