Influence of operating conditions on the retention of fluoride from water by nanofiltration

Titanium(IV) hydrate based on chitosan template for defluoridation from aqueous solution

“…Sorption experiments showed the following results: Ti-CHI could remove fluoride from aqueous solutions with low fluoride concentrations (4.52 mg/L), making water meeting the permitted drinking water standard (0.55 mg/L, below 1 mg/L); the Ti-CHI had an effective defluoridation capacity in a wide pH range (4)(5)(6)(7)(8)(9) and is a potential adsorbent for natural fluoride-contaminated water with a basic pH; and finally, the presence of anions had a deleterious effect on the adsorption of fluoride, particularly for CO 3 2− , HCO 3 − and PO 4 3− . After combining the defluoridation effect, the pH effect and the analysis of the FTIR and Zeta potential data, we found that the adsorption process was governed by both electrostatic adsorption and chemical bonding: the NH groups and Ti OH groups were the adsorption sites for F − on Ti-CHI.…”

“…The surface charges were measured using Zeta-Sizer; these values were based on the electrophoretic mobility of the adsorbents in aqueous media at different pHs. Each measurement was performed in an aqueous solution with a constant ionic strength (0.1 M NaNO 3 ); the pH was adjusted using NaOH or HNO 3 . Each Zeta potential was measured 4 times; the average values were used in the Zeta potential-pH plot.…”

“…To study the effects of different anions on the defluoridation capacity, the Cl − , SO 4 2− , CO 3 2− , HCO 3 − , NO 3 − and PO 4 3− ions that are common in natural water bodies were added to the fluoride aqueous solution as coexisting anions [20,21]. The initial concentrations of the coexisting anions were either 20 mg/L, 60 mg/L and 100 mg/L.…”

“…Consuming too much fluoride-contaminated drinking water can cause endemic fluorosis. Individuals suffering from fluorosis may develop symptoms that include periosteal proliferation, osteoporosis and dental illnesses [2,3]. A comprehensive literature review reveals that defluoridation through adsorption onto various materials is promising because it is cost effective in the context of the medium and running costs and it is characterized by easy operation, high adsorption capacity, recyclability, numerous useful cycles, and possible regeneration [4].…”

Factors affecting fluoride and natural organic matter (NOM) removal from natural waters in Tanzania by nanofiltration/reverse osmosis

“…Fluoride retention by NF/RO is generally governed by steric effects (size exclusion) and electrical effects (charge repulsion, Donnan exclusion and dielectric exclusion) (Shen and Schäfer, 2014). A variety of parameters, including feed compositions, membrane characteristics and operational conditions, lead conditions to be more conducive to the dominant effect of one mechanism over the other (Bejaoui et al, 2011;Mnif et al, 2010;Richards et al, 2010;Shen and Schäfer, 2014).…”