Material For Fluoride Removal Research Articles

Efficient removal of fluoride on aluminum modified activated carbon: an adsorption behavioral study and application to remediation of ground water

In recent times, ground water contamination by toxic elements is of great concern and it is to be addressed for consumption of human, animal, and plant growth. In this context, we have synthesized an adsorbent by modifying commercially available activated carbon with aluminum and tested for de-fluoridation studies. The activity results suggested that the optimized adsorbent is highly efficient in removing the fluoride from ground water. Adsorption maxima are obtained over a wide pH range from 4 to 9, with a contact time of 15 minutes at a dosage of 4 g/L. The results also revealed that the synthesized adsorbent is suitable for application in ground water without any pH adjustment and has exhibited 85%–95% tolerance for common anions in the range of 100–500 mg/L. Equilibrium adsorption isotherm models as well as kinetics of adsorption were applied for the system. An adsorption capacity of 20.4 mg/g and fast kinetics observed are most favorable for defluoridation. Reuse of adsorbent over repeated cycles was investigated. Residual amount of aluminum in treated water is found to be negligible. The removal of toxic elements like Pb, Cd, Cr, Cu, Ni, Zn, As, and Se under the optimized experimental conditions has also been investigated. Al-AC found to be a highly promising material for removal of fluoride and toxic metals from drinking water.

Removal of fluoride ions from aqueous solution by metaettringite.

Fluoride contamination is a major problem in wastewater treatment. Metaettringite (which has previously shown enhanced anion adsorption) was investigated as a possible adsorbent to remove fluoride from low-concentration solution (25 mg-F/L). The fluoride removal properties of ettringite and metaettringite were first compared at pH 10, and metaettringite was found to be more effective. The dominant reaction mechanism for fluoride adsorption in metaettringite was found to be recrystallization of metaettringite by rehydration; this was accompanied by precipitation of calcium fluoride. The adsorption kinetics followed the pseudo-second order model. Metaettringite was also able to remove fluoride effectively in low pH environment (i.e., at pH 3.5). The influence of coexistence of sulfate ions in solution on the fluoride removal performance was investigated, and a small decrease in performance was noted. The residual fluoride concentrations obtained with higher doses of metaettringite were lower than those specified by the Japanese effluent standard (non-coastal areas: 8 mg-F/L; coastal areas: 15 mg-F/L). The fluoride removal capacity of metaettringite was compared with those of other solid materials. The observed maximum capacity was 174.7 mg-F/g-metaettringite. In the case of high fluoride concentration solution, the main removal mechanism will be changed to calcium fluoride precipitation. In general, metaettringite is regarded as promising material for fluoride removal in wastewater treatment.

Experimental evaluation of sorptive removal of fluoride from drinking water using natural and brewery waste diatomite

This paper focuses on introducing low-cost water treatment options by using waste products from the beer industry, thereby contributing to cleaner production. To this purpose, sorptive removal of fluoride from drinking water using locally available natural grade diatomite (NGD) and brewery waste diatomite (BWD) was studied in a batch adsorption system. The equilibrium was achieved within an adsorption time of 60 min for NGD and 30 min for BWD at the optimum pH of 5 and adsorbent dose of 60 g/L. The equilibrium data were best fitted to the Freundlich isotherm (R2 = 0.979 and 0.995) for NGD and BWD, respectively. The adsorption capacity (qmax) calculated from the Langmuir isotherm value obtained for NGD and BWD was 0.917 mg/g and 0.617 mg/g, respectively. The adsorption kinetics data for both adsorbents followed the pseudo-second-order model (R2 = 0.734 and 0.947 for NGD and BWD, respectively). The influence of other anions on fluoride removal process has a slight influence, following the order PO43− > HCO3− > CO32− > SO42− > NO3− > Cl- for both adsorbents. The materials can be used on a system level for real water sample of low fluoride concentration (≤ 5 mg/L) and could be regenerated. Though BWD is considered as a waste for the brewery, it is used as a useful material for removal of fluoride. This application can be a stepping stone for providing a solution for safe management of industrial waste while providing a resource for water treatment on a system level.

Activated red mud as a permeable reactive barrier material for fluoride removal from groundwater: parameter optimisation and physico-chemical characterisation

ABSTRACT The main aim of this work is to test the performance of red mud as a permeable reactive barrier (PRB) material for fluoride removal from water. Batch experiments were carried out to optimise the fluoride removal efficiency (RE) of activated red mud (ARM) based on four selected parameters, namely, the initial fluoride concentration (3–40 mg/L), adsorbent dose (0.5–5 g/L), pH (3.0–11.0) and ionic strength (0.001–0.5 M). Statistical analysis of the results revealed the optimum conditions as initial fluoride concentration −21.46 mg/L, adsorbent dose −2.77 g/L, pH 7.01 and ionic strength −0.24 M, respectively. Under the optimum conditions, fluoride RE of 87.3% was achieved. The individual effects due to initial fluoride concentration, adsorbent dose and ionic strength on fluoride removal were highly significant (F = 59.69; P < 0.005); whereas adsorbent dose, pH and ionic strength showed the greatest squared effects (F = 26.05; P < 0.001). The interaction effect due to initial fluoride concentration and adsorbent dose was also found to be significant (F = 12.52; P = 0.002) for fluoride removal. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses were performed to identify the change in functional group and surface topography following red mud activation.

Effect of Doped Iron on Fluoride Sorption by Calcined MgAlFe-CO&lt;sub&gt;3&lt;/sub&gt; Layered Double Hydroxides

A series of MgAlFe-CO3 layered double hydroxides (LDHs) were successfully prepared by co-precipitation method. With synthetic wastewater, the effect of doped iron on fluoride sorption by calcined MgAlFe-CO3 layered double hydroxides (CLDH) under different pH and contact time conditions was investigated. The sorption isotherm data were fitted well to Langmuir isotherm at 25 °C. The maximum sorption capacity of fluoride on CLDH increases first and then decreases with the increase of Fe/Al molar ratio and attains maximum of 71.94 mg/g when Fe/Al molar ratio is 1:2, although doped iron is unfavorable to the regeneration of original layered structure for CLDH after fluoride adsorption. No aluminium in the solution after fluoride adsorption was detected when Fe/Al molar ratio is equal to or larger than 1:2. The results indicate that CLDH with proper Fe/Al molar ratio is a promising candidate as an adsorbent material for fluoride removal from aqueous solutions.

Fluoride removal from drinking water in Senegal: laboratory and pilot experimentation on bone char-based treatment

In Senegal there are four regions where fluoride concentration in drinking water exceeds the World Health Organization guide value of 1.5 mg/L. This generates permanent damages to the teeth (dental fluorosis) and to the skeleton (skeletal fluorosis). A safe, efficient, simple and low-cost effective defluoridation technique is not available yet and needs to be developed in order to prevent the occurrence of fluorosis. This experimental research was carried out in order to define an appropriate technology for fluoride removal from groundwater in Senegal. Batch tests and filtration tests at laboratory and pilot scale were carried out using animal bone char as adsorbent material for fluoride removal. Possible influencing parameters, such as specific ions in Senegalese drinking water, were investigated and the best process conditions were defined for the application in Senegal. The results attest to the efficacy of bone char in removing fluoride from Senegalese water: at pilot scale the mean specific adsorption was 2.7 mg F−/g of bone char, corresponding to a total treated volume of 4,000 L and a filter life of nearly three months.

Development of Functional Material for Removal of Fluoride by DCPD and Waste Materials

Development of Functional Material for Removal of Fluoride by DCPD and Waste Materials