Adsorption and Desorption Characteristics of Vanadium (V) on Coexisting Humic Acid and Silica
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Adsorption and Desorption Characteristics of Vanadium (V) on Coexisting Humic Acid and Silica Qiao-yu Song & Meng Liu & Juan Lu & Yu-liang Liao & Li Chen & Jin-yan Yang
Received: 29 March 2020 / Accepted: 20 August 2020 # Springer Nature Switzerland AG 2020
Abstract Vanadium (V) has been progressively studied due to its potential toxicity in the environment as a trace metal. A coexistence system of humic acid (HA) and silica was employed to simulate the main organic and inorganic components of soil. The adsorption and desorption characteristics of V by the system and the effects of several environmental conditions were investigated. The adsorption data were well described by the Langmuir and Freundlich models, illustrating that the adsorption of V on HA + silica was a monolayer adsorption. The kinetic study indicated that the main adsorption controlling step was a chemical reaction. The thermodynamic study showed that the adsorption was exothermic and spontaneous. The adsorption-desorption process was strongly dependent on the solution pH and HA concentration, while Q. 0.05) could be observed from the adsorption capacity of low concentration V by HA + silica at different temperatures (Fig. 5a). However, with temperature increasing, the adsorption amount of high concentration V by HA + silica dropped from 359.97 to 271.50 mg kg−1. These results contradicted with the existing study which reported a promoting role of the rise of temperature in the adsorption of Cu(II) and Zn(II) on HA (Li et al. 2010). The calculated ΔH° of − 2.949 kJ mol−1 showed that the adsorption of V on HA + silica was an exothermic process, suggesting that the
4 Conclusion This study investigated the adsorption-desorption characteristics of V by HA + silica coexistence system and the effects of various environmental conditions, with soil organic and inorganic composition simulated by HA and silica, respectively. The results implied that soils rich in organic matter might have stronger ability to adsorb V under the same condition, and the mechanism was largely involved with the reduction and fixation ability of organic matter such as HA. According to
Water Air Soil Pollut
(2020) 231:460
the pH-dependence of the adsorption-desorption process, it is reasonable to infer that acidic condition is more favorable for soil components to adsorb more and release less V. While the adsorption of V on HA + silica is thermodynamically exothermic and spontaneous, the fixation of V is able to occur easily under natural circumstances. This study also offers some explanation for the relatively low mobility and bioavailability of V in the soil, which is vital to the assessment of risk of V in soil to the ecological stability. Funding Information This work was supported by the Industry Support and Guidance Program of Gansu Higher Education (2019C-16); the Fundamental Research Funds for the Central Universities (2019FZJD007); the Chengdu Science and Technology Project (2018-YF05-00760-SN); and Sichuan University Foreign Culture and Education Expert Program (G2
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