Abstract
Two types of pretreatment categories, namely microwave-assisted alkalization and microwave-assisted acid oxidation, were used to synthesize novel wheat straw adsorbents for the effective removal of Cd(II) in simulated waterlogged paddy soil. A systematic adsorption behavior study, including adsorption kinetics and adsorption isotherms was conducted. Results showed that wheat straw pretreated by microwave-assisted soaking of NaOH and ethanol solution obtained the highest Cd(II) removal efficiency of 96.4% at a reaction temperature of 25 ℃, pH of 7.0, initial Cd(II) concentration of 50 mg/L, and adsorbent/adsorbate ratio of 10 g/L. Sequential extraction experiment was carried out to analyze the changes of different of Cd(II) in soil, the aim of which was to study the mobility of Cd(II) and then evaluate the toxicity that Cd(II) might bring to plants. A 60-day incubation was performed to investigate the dynamic variations of soil pH and dissolved organic carbon content over incubation time. Characterization analyses revealed the morphological changes of wheat straw adsorbents, which suggested that those pretreatment methods were of significance. This study provided an environmentally friendly way to reuse agricultural wastes and remedy Cd(II) contaminated soil.
Highlights
Cadmium as one of the common hazardous heavy metals can cause potential threat to human life.It can be introduced to the environment by various anthropogenic activities, especially by industrial processes, such as mining, fossil fuel combustion, metal smelting, processing and fabricating, use of cadmium in chemical fertilizers, application of cadmium in pigments and stabilizers for plastics, and so forth [1,2]
The overall trend for the four adsorbents was that they showed higher Cd(II) adsorption capacity than that of the Raw wheat straw (RWS) when it came to the fractionations of HAc-Cd and CaCl2 -Cd, and the adsorbent ENMWS had the highest Cd(II) removal efficiency among the four adsorbents
When HAc-Cd was chosen as an indicator to evaluate the removal rate, following result was found: by the end of the incubation, ENMWS, EKMWS, EHMWS, and ECMWS could remove
Summary
Cadmium as one of the common hazardous heavy metals can cause potential threat to human life. It can be introduced to the environment by various anthropogenic activities, especially by industrial processes, such as mining, fossil fuel combustion, metal smelting, processing and fabricating, use of cadmium in chemical fertilizers, application of cadmium in pigments and stabilizers for plastics, and so forth [1,2]. Smoking may significantly increase human’s exposure to cadmium [3]. It is easy for cadmium to release to the environment, especially to the aquatic environment, and, as a consequence, it will cause damage to soil and air and become a long-term risk to ecosystems and humans [4]. Public Health 2019, 16, 205; doi:10.3390/ijerph16020205 www.mdpi.com/journal/ijerph
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