Groundwater fluoride removal using modified mesoporous dung carbon and the impact of hydrogen-carbonate in borehole samples

Abstract

There have been many research reports pertained to the interference of co – ions including hydrogen carbonate against the removal of fluoride from water. In this context, the present research explores the fluoride removal efficiency of ammonium carbonate modified dung derived carbon (DDC500) in the absence and presence of hydrogen carbonate using synthetically made fluoride solutions and groundwater samples. The adsorbent DDC500 was found to achieve the highest removal of 80% of fluoride at pH 6.95 than the washed carbon (DDC500W) and dung ash (DA) of 48% and 23% respectively. In DDC500, the carbon base in concert with inorganic residues actively functioned in the fluoride removal process and chosen for synthetic fluoride solutions (2–5 mg L−1) and 16 groundwater samples (2.1–3.6 mg L−1) from 10 locations of Usilampatti Taluk in Madurai District, South India. After the removal of hydrogen carbonate in groundwater, the percentage of samples was increased in accordance with the safe limits of World Health Organization (WHO) and Bureau of Indian Standard (BIS). Langmuir isotherm model (R2 = 0.9379) was in concordance with the adsorption of fluoride from groundwater free from hydrogen carbonate. The dynamics of other groundwater quality parameters at conditions and the independency between Fˉ/HCO3ˉ ratio and DE were illustrated by scatter plots. Characterization studies for the dried dung (CD110), derived carbons (DDC500 and DDC500W) and ashes (CD110A, DDC500A and DDC500WA) using FE–SEM, XRD, FTIR, Raman and TGA – EGA were done to understand the nature and behavior of materials.