Defluoridation efficiency of a green composite reactive material derived from lateritic soil and gastropod shell

• Published in: Sustainable chemistry and pharmacy 2019-06, Vol.12, p.100131, Article 100131
• Main Authors: Oladoja, N.A., Bello, G.A., Helmreich, B., Obisesan, S.V., Ogunniyi, J.A., Anthony, E.T., Saliu, T.D.
• Format: Article
• Language: English
• Subjects: Composite material; Defluoridation; Fluoride; Gastropod shell; Groundwater; Laterite
• ISSN: 2352-5541; 2352-5541
• DOI: 10.1016/j.scp.2019.100131

In the bid to exploit the synergy in mixed metal matrix that enhances substrate binding affinity, a composite reactive material (GLT) was prepared using lateritic soil and Gastropod shell as precursors. The defluoridation efficiency of the GLT was studied in laboratory grade fluoride contaminated water and groundwater matrix. Using experimental evidences, insight into the underlying defluoridation mechanisms of GLT was provided. The monolayer adsorption capacity (qm, mg/g) of the GLT (43.7 mg/g) was higher than that of any of the precursors (i.e. lateritic soil (qm = 2.8 mg/g) and Gastropod shell (qm = 19.8 mg/g)), which confirmed the synergistic effect of the constituents of the composite. Premised on the results of kinetic analysis, the Gibbs (∆G) free energy value of formation of insoluble metal fluoride and the results of the evaluation of the effects of water chemistry on the fluoride removal efficiency of the GLT, mechanism of the defluoridation process was found to be a combination of adsorption (via ion exchange or outer sphere complexation) and precipitation reaction. Relative to the performance of the GLT in laboratory grade water, the GLT was also effective in groundwater but the value of the Langmuir monolayer adsorption capacity (qm mg/g) was lower in the groundwater system (29.76 mg/g) than in the laboratory grade water system (43.7 mg/g). The leached constituents of the GLT enhanced the values of the pH, electrical conductivity and the total dissolved solids of the treated water. [Display omitted] •monolayer adsorption capacity of the GLT was higher than that of the precursors.•the mechanism of defluoridation was a combination of adsorption and precipitation.•the GLT was effective in GW but the monolayer adsorption capacity was lower.•leached constituents of the GLT impacted on the quality of the treated water.