Visible Light Spectroscopic Analysis of Methylene Blue in Water

Abstract

We herein report a universal calibration curve for the UV-Visible spectrophotometric determination of the concentration of polymerizable dyes (C dye ) in solution. The equation for the calibration curve is ∑ ( ) , in which m is the number of dye species in solution, both monomeric and aggregates, I F is the instrumental factor that takes values around 1, L is the path length, are the absorbance values at λ i , which are the characteristic wavelengths of maximum absorption for all dye species, and β i are coefficients of proportionality that can be evaluated either with the molar attenuation coefficients of the different dye species (if known) or via error minimization. The method has been successfully applied to construct a calibration curve of methylene blue in water which is applicable in a wide range of methylene blue and chloride concentrations, regardless of both the aggregate concentration distribution and the temperature. In addition, it was found that the molar fractions of each MB species in solution could be fairly approximated by means of simple algebraic expressions in the A 650 /A 607 absorbance ratio.

Graphene oxide membranes for effective removal of humic acid

“…The concentration of MB in feed and permeate was then calculated according to the maximum absorption measured by the UV-vis spectrophotometer. The maximum absorption peak of MB was scanned in the wavelength range from 300 to 800 nm and was detected within the visible light region (λ = 668 nm), which is in agreement with literatures [50]. The employed standard curve of MB at a range of concentrations, 10 mg/L, 5 mg/L, 2.5 mg/L, 1.25 mg/L, 0.625 mg/L, 0.312 mg/L and 0.156 mg/L, is illustrated in Fig.…”

“…UV-vis spectrophotometer (PerkinElmer Lambda 365) was used to determine the concentration of methylene blue (λ = 668 nm) [50]. Before each sample measurement, de-ionized (DI) water was recorded as the background spectrum to avoid any absorption of water and cuvette.…”

Simultaneous Fractionation, Desalination, and Dye Removal of Dye/Salt Mixtures by Carbon Cloth-Modified Flow-electrode Capacitive Deionization

“…Further increasing C NaCl,0 from 10 to 20 g L −1 enhanced the MB removal in both units, which might be due to the increase in the aggregation level of MB molecules with the increase in the NaCl concentration; thereby, some of the MB molecules might be removed in their aggregated forms (such as a dimer, trimer, and tetramer). 43 For the interaction of the MB and NaCl recovery processes, as shown in Figure 4e, the RC NaCl values of both units remained almost unchanged with the increase in C MB,0 . The higher NaCl recovery in CC-FCDI relative to U-FCDI was probably attributed to the slight adsorption of NaCl by the carbon cloth layer.…”

Photoactive Red Fluorescent SiO2 Nanoparticles Based on Controlled Methylene Blue Aggregation in Reverse Microemulsions

“…This is an important feature given the natural tendency of MB molecules for aggregation when in high to moderate concentrations. 40,47,50,51 Also, purified core-MB@SiO 2 NPs (with the same χ = 3 ratio but with no further TEOS addition) showed a similar absorption spectrum to the washed MB@SiO 2 NPs: in both cases, the more intense absorption bands belong to the dye in its monomeric form (λ max ∼660 nm), in opposition to what happens during the synthesis and before the purification steps (Figure S2). This result reveals that the extra TEOS addition for depositing a SiO 2 shell does not influence the MB monomer/aggregate ratio, being only dependent on the HDTMOS amount at the beginning of the synthesis.…”

“…38 In a nutshell, the spectroscopic behavior of MB in aqueous solutions can be interpreted as an equilibrium between a monomer and a dimer, 39 although higher aggregates even at a relatively low concentration of 3.4 × 10 −5 M have been recently proposed. 40 Basically, the monomer presents an absorption peak in H 2 O in the 650−660 nm interval, while the dimer and higher aggregates absorb at ∼610 nm in liquid solvents. 41 In particular, these higher molecular species deactivate the photoexcitation pathways and do not present photoactivity for producing singlet oxygen.…”