Applied Chemical Engineering

Comparative Cloud Point Extraction of Gold Using Novel Benzimidazole vs. Benzothiazole Azo-Ligands: Analytical Performance and Antibacterial Activity

Dalal Abbas Ali

Department of Chemistry, College of Education for Women, University of Kufa, Iraq

Ibtehaj Raheem Ali

Department of Chemistry, College of Education for Women, University of Kufa, Iraq

DOI: https://doi.org/10.59429/ace.v9i2.5932

Keywords: gold, benzothiazole, benzimidazole, azo-ligands, antibacterial activity, cloud point extraction, Surfactant-based extraction

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Abstract

Herein, two new azo reagents, 2-[(1-banzimidazol)azo]-2-hydroxy-5-banzal (BIApB) and 6-[(1-banzethiazol) azo thymol] (BTAT), were synthesized and identified using FTIR, UV-Vis, mass spectrometry, and ¹H-NMR. Also, this research presents a comparative analysis of novel azo-chelating reagents for the cloud point extraction (CPE) of gold complexes. The study evaluates how the structural differences between the benzimidazole and benzothiazole moieties influence both extraction efficiency (E%) and the biological potency of the resulting complexes. The optimal conditions for both reagents (BIApB and BTAT) were determined. These included pH, TritonX-100 concentration, temperature, and heating time. The thermodynamic characteristics of the CPE were calculated for both chelators with gold. The CPL layer easily removed by syringe.

This approach indicates an endothermic reaction. The analytical figures for BIApB and BTAT, respectively, were good, with limits of detection (LOD) of 0.30 and 0.35 µg L^-1, limits of quantities (LOQ) of 1.0 and 1.16 µg L^-1, pre-concentration factors (PF) of 200 and 125, enrichment factors (EF) of 125 and 147.4, and RSD% values of 8.7% and 1.1%. The calibration curves for two complexes were linear from 1.0 to 7.0 µg L^-1.

Additionally, analytical results confirm effective gold recovery with both reagents; however, antibacterial screening against E. coli and S. aureus revealed that the BTAT-Au(III) complex possesses significantly higher bioactivity, with inhibition zones reaching 28 mm. This is attributed to the increased lipophilicity provided by the sulphur-containing benzothiazole ring, which facilitates membrane penetration. Statistical t-tests (p < 0.05) confirmed that the antibacterial effects are dose-dependent, establishing BTAT as a high-performance, multifunctional reagent for both trace metal analysis and antimicrobial applications.

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