Synthesis and Characterization of Immobilized Thiolactic Ligand System for the Detoxification of Tannery Wastewater

Abstract

A porous solid polysiloxane immobilized thiosalicylic acid ligand system has been prepared by hydrolytic polycondensation of tetraethylorthosilicate with a mixture of 3-chloropropyltrimethoxysilane, methanol and sodium hydroxide as a catalyst, gelation formed after 40 min. The product formed was functionalized with excess ethylchloroacetate, triethylamine and immobilized with thiosalicylic acid. The immobilized ligand was characterized using FTIR, the spectrum showed characteristic absorption regions (cm-1) at: 3384 (OH), 1587 to 1722 (C=C, C=O); 900 to 1038 (Si - O) respectively. SEM-EDX showed irregular particle sizes of the polysiloxane matrices with elemental composition (wt %): 3-CPPS; Si (50.45), O (25.02) and Cl (24.57). F - 3CPPS showed, O (58.68), Si (41.32); thiolactic (0.00 of S). The competitive sorption characteristic of the metal ions (Cr3+, Fe3+, Pb2+, Cu2+ and Zn2+) were studied using Microwave Plasma Atomic Emission Spectrophotometer (Agilent MPAES-4200). The immobilized thiolactic ligand exhibits high potential for the extraction of heavy metals in tannery wastewater at pH 6.0, this development would improve the treatment of tannery wastewater at a low cost; batch or column systems of extraction of metal could be employed. Thermodynamic range for the parameters with respect to Cr3+, Fe3+, Pb2+, Cu2+ and Zn2+ yielded negative values for ΔGo, (Cu2+ -(8.650 to 11.962) to Fe2+ -(14.368 to 14.842) KJmol-1; positive values for ΔHo: Zn2+ (0.000) to Cu2+ (21.047) KJmol-1 and ΔSo: Zn2+ (47.421) to Fe3+ (245.869) Jmol1K1 respectively, indicating spontaneous, endothermic reactions and high degree of disorderliness with respect to metal ion binding capacity to the ligand system.