Synthesis and characterization of an immobilized thiosalicylic–mercaptoethanol biligand system and its application in the detoxification of chromium(iii) and iron(iii) ions from tannery wastewater

Background: Effective wastewater treatments are paramount to contemporary scientists. The existing methods are ineffective in detoxifying tannery wastewater. Aim: This study aims to synthesize and characterized polysiloxane-Immobilized thiosalicylic-mercaptoethanol ligand system (PITSMCBLS) and used in detoxification of Cr3+ and Fe3+ from tannery wastewater. Method: Porous solid PITSMCBLS was prepared by hydrolytic polycondensation of tetraethylorthosilicate with mixture of 3-chloropropyltrimethoxysilane, methanol and sodium hydroxide as catalyst. The gelation formed (3-CPP) after 40 min, was functionalized (F-3CPP) with excess ethylchloroacetate, triethylamine and grafted with thiosalicylic-mercaptoethanol bi-ligand. The PITSMCBLS was characterized using FTIR and SEM-EDX. The competitive sorption characteristics of metal ions (Cr3+ and Fe3+) were studied using Microwave Plasma Atomic-Emission Spectrophotometer. Result: The FTIR spectrum of PITSMCBLS showed vibrational frequencies (cm-1) at: 3339, (O-H); 2928, (C-H); 2685, (SH); 2497, (Si-H); 1587–1707, (C=O) and 1028, (Si-O). The SEM-EDX showed irregular particle sizes (4.4294 ± 1.7187 nm) and elemental composition (wt %): 3-CPP, Si (50.45); O (25.02) and Cl (24.57). The F-3CPP showed, O (58.68) and Si (41.32), while PITSMCBLS showed 11.94 of S. Gibbs free energy yielded negative range values for ΔGo (Cr3+ -14.187 to -14.832 and Fe3+ - 14.369 to -14.843 kJmol-1), positive values for: ΔHo (Cr3+ 5.345 and Fe3+ 0.000 kJmol-1) and ΔSo (Cr3+ 64.459 and Fe3+ 47.421 Jmol1K1) respectively. Conclusion: PITSMCBLS exhibits high potential for the extraction of Cr3+ and Fe3+ in tannery wastewater. The Thermodynamic values indicate spontaneous, endothermic reactions and high degree of disorderliness with respect to metal ion binding capacity to the ligand system. This development would improve tannery wastewater treatment.