AUTHOR=Zhang Mingyue , Zhou Yaru , Wang Fangling , Chen Zeshao , Zhao Xu , Duan Weidong , Yin Guangting , Yang Xinling , Li Junfeng , Yin Quanyu , Zhao Mingqin TITLE=Preparation of biomass-based hydrogels and their efficient heavy metal removal from aqueous solution JOURNAL=Frontiers in Chemistry VOLUME=10 YEAR=2022 URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2022.1054286 DOI=10.3389/fchem.2022.1054286 ISSN=2296-2646 ABSTRACT=

In this work, a porous tobacco straw-based polyacrylic acid hydrogel STS-PAA with high adsorption performance was prepared by polymerizing pretreated waste tobacco straw (TS) with acrylic acid/potassium acrylate by UV radiation initiation. The adsorption performance of metal ions was investigated. The effects of different temperatures (25°C, 35°C, and 45°C), adsorption times (1–420 min), pH values (2.0–6.0) and initial concentrations (0.25–4.0 mmol L⁻¹) of metal ions on the adsorption amount of heavy metal ions were investigated. The results showed that the hydrogel had a high removal rate of Pb²⁺, Cd²⁺ and Hg²⁺ in aqueous solution. The adsorption of Pb²⁺ was particularly effective. When C₀ = 4.0 mmol L⁻¹, pH = 6, the equilibrium adsorption amount of Pb²⁺, Cd²⁺ and Hg²⁺ reached 1.49 mmol g⁻¹, 1.02 mmol L⁻¹ and 0.94 mmol g⁻¹, respectively. The chemical structure and morphology of the hydrogels were characterized by FT-IR, EDS, SEM and XPS. The Langmuir model fits well with the adsorption system. The kinetic data suggest the adsorption of Pb²⁺, Cd²⁺ and Hg²⁺ follow the pseudo-first-order model. This indicates that STS-PAA adsorption of three heavy metal ions is monolayer physical adsorption. Thermodynamic analysis shows that the adsorption of Pb²⁺, Cd²⁺ and Hg²⁺ by STS-PAA is an endothermic (ΔH>0) entropy increase (ΔS>0) non-spontaneous reaction.