Influence of solution chemistry on heavy metals removal by bioadsorbent tea waste modified by poly (vinyl alcohol)

In this study, the macroporous spherical composite biomaterials, Poly(vinyl alcohol)/teawaste (PVA/TW), were prepared and investigated for their potential to remove Pb2+, Hg2+, and Cu2+ from aqueous solution. Investigations showed that adsorption capacity of Hg2+ by PVA/TW bead was much higher than that of Pb2+ and Cu2+, while adsorption rate of Pb2+ was fastest. The experimental data obtained for Pb2+-PVA/TW, Hg2+-PVA/TW, and Cu2+-PVA/TW at different solution temperatures indicate a monolayer type biosorption, which explains why the Langmuir isotherm accurately represents the experimental data obtained in this study. The Langmuir maximum biosorption capacities of Pb2+, Hg2+, and Cu2+ onto PVA/TW were 81.56, 175.68, and 49.08mg/g at 298K, respectively, which is comparatively superior to most other low-cost biomaterials. Fourier transform infrared spectroscopic analysis of the metal-loaded biosorbents confirmed the participation of -COOH, -NH2, and O-CH3 groups in the complexation of Pb2+, Hg2+, and Cu2+. Thermodynamic parameters demonstrated that the biosorption of Pb2+ onto PVA/TW was endothermic, spontaneous, and feasible at 288-318K. The results evidently indicated that PVA/TW would be suitable biosorbents for Pb2+, Hg2+, and Cu2+ in wastewater under certain conditions.