Interactions in the Ti(IV)–2,2',3,4-Tetrahydroxy-3'-Nitro-5'-Sulfoazobenzene–Cationic Surfactant System

We studied the complexation of titanium(IV) with 2,2',3,4-tetrahydroxy-3'-nitro-5'-sulfoazobenzene (R) in the presence of cationic surfactants (CSs) cetylpyridinium chloride (CPCl), cetylpyridinium bromide (CPBr), and cetyltrimethylammonium bromide (CTMABr). In the presence of cationic surfactants, mixed-ligand complexes are formed with the ratio of components $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ : H4R– : CS = 1 : 2 : 2. The optimal pH values of the complex formation were found: 4.5 for ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2 and 3.5 for mixed-ligand complexes ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2(CPCl)2, ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2(CPBr)2, and ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2(CTMABr)2. We also investigated the effect of time, temperature, and concentrations of the reacting components on the formation of mixed-ligand complexes. The Beer law is observed in the concentration range of ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2, ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2(CPCl)2, ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2(CPBr)2, and ( $${\text{Ti}}({\text{OH}})_{{\text{2}}}^{{{\text{2}} + }}$$ (H3R2–)2(CTMABr)2 of 0.10–1.8, 0.10–1.92, 0.10–1.92, and 0.08–1.92, respectively. The effect of foreign ions and masking substances on the determination of titanium(IV) as mixed-ligand complexes was studied. We developed a procedure for the spectrophotometric determination of trace amounts of titanium in sea sand taken from the Caspian Sea coast near the Turkan village.