Analytical evaluation and efficient removal of Congo red from water using polycaprolactone and poly(ε-caprolactone-co-glycidyl methacrylate) synthesized via a titanium catalyst

The reaction of 3-[3-(hydroxymethyl)-5-tert-butylsalicyl]-5-tert-butyl-2-hydroxybenzyl alcohol with one and two equivalents of titanium (IV) oxyacetylacetonate ([TiO(acac)₂]) in refluxing methanol, in the presence of excess tetraethylammonium chloride, afforded two new complexes (1 and 2) after work-up. The synthesized complexes were fully characterized. Titanium complexes and ammonium molybdate [(NH₄)₆Mo₇O₂₄·4H₂O] have been assessed as catalysts for polymerization of ɛ-caprolactone (CL) and glycidyl methacrylate (GMA), with and without benzyl alcohol, with and without solvent present, at fixed temperatures; yield percentages were more than (90 %) with good control. In this study, polycaprolactone (PCL) and a copolymer with glycidyl methacrylate (GMA) were successfully synthesized, and their chemical structures were analyzed using proton nuclear magnetic resonance (¹H-NMR) and gel permeation chromatography. The characterization results showed that the polymer (PCL-GMA) was successfully fabricated. The Langmuir isotherm model fits the adsorption equilibrium data of the adsorbents quite well. It showed that Congo red dye (CR) could be adsorbed at a maximum rate of 18.450 mgg-1. The method exhibited excellent linearity over the range of 1–40 mg L⁻¹ (R² = 0.9983), with low detection and quantification limits of 0.075 mg L⁻¹ and 0.228 mg L⁻¹, respectively. The precision was satisfactory (RSD < 3%), and recoveries ranged from 96% to 102%.