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

Abstract

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 49.08 mg/g at 298 K, 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, –NH_2, 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 288–318 K. The results evidently indicated that PVA/TW would be suitable biosorbents for Pb²⁺, Hg²⁺, and Cu²⁺ in wastewater under certain conditions.

Keywords:

• Tea waste
• Polymer PVA
• Adsorption mechanism
• Heavy metals

Acknowledgments

The authors gratefully acknowledge financial supports from the National Natural Science Foundation of China (No. 21304040), the Fundamental Research Funds for the Central Universities (lzujbky-2012-80) and Chinese Postdoctoral Funds (2013M532090).