Hydrated cement: A promising adsorbent for the removal of fluoride from aqueous solution

Experimental Evaluation of Activated Termite Mound for Fluoride Adsorption

“…Consequently, the effect of the basic metallic oxides to increase the pH of the solution was negligible and overshadowed by the effect of the oxides of Al and Fe. The result is similar to previous defluoridation studies [13,45,46]. This decrease in the amount adsorbed could be due to the decrease in the fluoride/active binding sites ratio [20].…”

“…Most fluoride ions adsorbed to the binding sites at low initial concentration, resulting in a high percentage of fluoride adsorbed, while only part of the fluoride combined with the limited binding sites at high initial concentration, resulting in a relatively low removal percentage [42]. Similar observations have been made earlier [46,47]. ) is the Polanyi potential, R (kJ/(mol.K)) is the gas constant, and T(K) isthe temperature of the equilibrium experiment.…”

A Comparative Study on Removal of Hazardous Anions from Water by Adsorption: A Review

“…An increase in adsorption capacity was observed with a higher concentration of magnesium and calcium due to an increase in surface positive charges and attraction of negatively charged ions onto various metal oxide surfaces on fluoride removal by nano magnesia (NM), as shown in the study conducted by Maliyekkal et al [62]. Similar effects were observed by [157] at 400 mg/L of Ca 2+ by using hydrated cement and on alumina cement granules [23]. Also, the formation of insoluble CaF 2 and MgF 2 was the reason for the increase of adsorption by granular ceramic at 200 mg/L and Ca 2+ and Mg 2+ concentration [40]; however, Mn 2+ and Fe 3+ at 200 mg/L were reported to decrease fluoride removal capacity up to 10% on nano magnesia [62].…”

“…The decrease in fluoride adsorption observed by the presence of HCO 3 − , CO 3 2− , and SO 4 2− was due to the competition for active sorption sites or due to the change in pH or combination of them [4,29,147,160,161,[163][164][165][166][167]181], where the decrease of fluoride was related to anions competitions or effects of pH; however, in the same study, it was reported that sulfate did not have significant effect on fluoride removal [157]. A similar study was reported on MgO nanoplates [144].…”

Defluoridation of water using nano-magnesium oxide

“…It was noticed that the percentage of fluoride removal decreased as initial fluoride concentration was increased. This might be due to the fact that at higher fluoride concentration, the binding capacity of the adsorbent approaches saturation, resulting in a decrease in overall percent removal [33]. Figure 9 shows the removal capacity of fluoride by nano-MgO in the presence of various other ions, namely OH À , Cl À , SO 2À 4 and HCO À 3 .…”