Removal of Fluoride from Groundwater Using New Biochar Adsorbents
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Abstract:
In this study, new biochar adsorbents were first prepared from the peanut shell, chestnut shell, walnut shell, and orange peel under different pyrolysis temperatures, and then the fluoride removal effects of these new biochar adsorbents were compared. The results showed that the biochar derived from the peanut shell with pyrolysis at 650 ℃ provided the best defluoridation effect. The surface structure of the peanut shell-derived biochar was then characterized and the effects of factors such as the adsorption equilibrium time, dosage of biochar, pH value, and initial concentration of fluoride ions on the defluoridation of the peanut shell-derived biochar were investigated. The results indicated that the optimum dosage of the biochar was 1 g/100 mL, the optimum pH was approximately 5.5~6, the adsorption equilibrium was attained after approximately 60 min when the removal rate was 82.25%, and that the adsorption capacity was 0.82 mg/g. With an increasing initial concentration of fluoride, the fluoride removal rate showed a declining trend. However, the adsorption capacity showed an increasing trend with increasing fluoride concentration. The simulated results of the adsorption isotherm of fluoride on the peanut shell-derived biochar indicated that the experimental data fitted well with both the Langmuir and Freundlich models. The maximum absorption capacity of this peanut shell-derived biochar on fluoride in groundwater was 1.11 mg/g. This study therefore provides new prospects in the recycling use of waste agricultural biomass and defluoridation of groundwater.
