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Analysis And Results. The ligand of Amido Black 10B azo dye is shown in Figure 1, and it was complexed with Pb (II) ions using a metal: ligand ratio of u = 1:1 mol.
It is easy to see that only the atoms of the -OH functional group participate in the coordination reaction. The structure of the lead complex in the immobilized fiber is presented in Fig. 2.



Figure 1. The structure of the ligand

H₂O
H₂O

Pb

O₂N

NH₂

N N

O₃S
NH₂ O
N N
NH₂

C
CH NH
CH₂
CH_{2 2}
NH₂
NH CH₂
NH₂

C
CH NH
CH₂

Figure 2. The structure of the complex

UV-Vis spectroscopy

The UV-Vis spectrum of the acidic azo dye (Figure 3) showed two lines from 263 nm to 368 nm. The first line may be due to the transition of π-π* in the aromatic ring, and the second line may be due to the n-π* transition of the N = N group [18]. Complex formation of azo reagent with Pb (II) ion was also confirmed by UV-Vis spectrum.

Figure 3. Absorption spectrum of organic amido black reagent immobilized on PPD-1 fiber (l=620 nm): before immobilization (1), after immobilization (2)

Figure 4. Reflectance spectra of fiber (1), immobilized reagent (2) complex with lead (II) ion (3) in universal buffer mixed media

It can be seen that λ max for the ligand is 620 nm. The complexation reaction is the main reason for the significant hypochromic shift in the region of π-π* and n-π* transitions, which reached a maximum of 490 nm in Fig. 4 [19].