Effects and Mechanisms of Calcium Ion Addition on Lead Removal from Water by <i>Eichhornia crassipes</i>

• Main Authors: Jin-mei Zhou, Zhong-cheng Jiang, Xiao-qun Qin, Lian-kai Zhang, Qi-bo Huang, Guang-li Xu
• Format: Article
• Language: English
• Published: MDPI AG 2020-02-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: <i>eichhornia crassipes</i>; lead; calcium ion (ii); alleviation; cation exchange; functional groups
• Online Access: https://www.mdpi.com/1660-4601/17/3/928

Karst water is rich in calcium ions (Ca²⁺) and exhibits poor metal availability and low biodegradation efficiency. This study sought to analyze the effects and mechanisms of Ca²⁺ on lead (Pb) removal and absorption by <i>Eichhornia crassipes</i> (a floating plant common in karst areas). Moreover, the morphology and functional groups of <i>E. crassipes</i> in water were characterized via SEM, and FTIR. The results demonstrated that the removal rate of Pb in karst water (85.31%) was higher than that in non-karst water (77.04%); however, the Pb bioconcentration amount (BCA) in <i>E. crassipes</i> roots in karst water (1763 mg/kg) was lower than that in non-karst water (2143 mg/kg). With increased Ca²⁺ concentrations (60, 80, and 100 mg/L) in karst water, the Pb removal rate increased (85.31%, 88.87%, and 92.44%), the Pb BCA decreased (1763, 1317, and 1095 mg/kg), and the Ca BCA increased (6801, 6955, and 9368 mg/kg), which was attributed to PbCO₃ and PbSO₄ precipitation and competitive Ca and Pb absorption. High Ca²⁺ concentrations increased the strength of cation exchange, alleviated the fracture degree of fibrous roots, reduced the atrophy of vascular bundles, protected the cell wall, promoted C&#8722;O combined with Pb, enhanced the strength of O‒H, SO₄^2&#8722;, C=O, and reduced the oxidization of alkynyl acetylene bonds.