Magnesium modified activated carbons derived from coconut shells for the removal of fluoride from water

Fluoride presence in water has been recognized as one of the major water related global problems, rendering the development of effective technologies for its removal as a very significant issue, for improving human health and well-being in the affected areas. Among the commonly applied technologies for fluoride removal, adsorption has gained great attention because it offers efficiency, low-cost treatment and simple operation. The present study aimed at developing novel adsorbents, namely activated carbon modified by magnesium or/and lanthanum and silica for fluoride removal. The structure and the morphology of resulted modified activated carbons (AC-Mg and AC-Si-Mg-La) were studied in detail by the application of BET, XRD, FTIR and SEM techniques. The proposed adsorbent materials were tested for the treatment of fluoride containing waters. The effects of the adsorbent's dosage, initial concentration of pollutant, pH value of the water and regeneration efficiency were examined. According to the obtained results, the maximum adsorption was observed at pH 8, after 4 h of reaction and 0.2 g/L of adsorbent dose. Langmuir-Freundlich isotherm model and pseudo-second order kinetic model fitted the experimental data sufficiently. At pH 8 a maximum adsorption capacity of 36.56 mg/g for AC-Mg and 54.48 mg/g for AC-Si-Mg-La, was found. Repeated adsorption and regeneration studies showed only a 10% decrease of adsorption capacity after 4 regeneration cycles of operation.