Fluoride removal from water by adsorption—A review

http://edge.rit.edu/content/P13418/public/Reference%20Documents/Fluoride%20Removal/Review%20of%20fluoride%20removal%20from%20drinking%20water.pdf

Review of fluoride removal from drinking water.

Fluoride in drinking water and defluoridation of water.

Recent advances in applications of activated carbon from biowaste for wastewater treatment: a short review.

Defluoridation of drinking water using adsorption processes

Removal of excess fluoride from water using waste residue from alum manufacturing process

The efficiency of untreated hydrated alumina (UHA) and thermally treated hydrated alumina (THA) obtained from hydrolysis of locally manufactured aluminum sulfate to remove fluoride from aqueous solution has been investigated in batch and continuous operation. The parameters considered were contact time and adsorbent dose, thermal pre-treatment of adsorbent, initial fluoride concentration and pH. The adsorption was rapid during the initial 20 min, but significant amount (> 90 %) was removed within one hour at an optimum adsorbent dose of 1.6 g/L for initial F - concentration of 20 mg/L. The removal efficiency of F - was increased with adsorbent dosage. Fluoride adsorption efficiencies increase with increase in the thermal treatment temperature up to 200 °C, but further increase in temperature resulted in decreased removal efficiency. For application in continuous packed bed column, treatment at 300 °C was taken as an optimum value. Fluoride adsorption capacity increases linearly with increase in F - concentration. High defluoridation efficiency was achieved using both UHA and THA within a pH range of 4.0 to 9.0. The adsorption data at ambient pH were well fitted to the Freundlich isotherm model with a minimum capacity of 23.7 mg F - /g and 7.0 mg F - /g for THA and UHA, respectively. The kinetic studies showed that the adsorption reaction of fluoride removal by hydrated alumina can be well described by a pseudo-second-order rate equation. Continuous packed bed column experiment using THA indicated that 4.5 g of THA could treat 6 L of water containing 20 mg/L fluoride before breakthrough. Hence, both UHA and THA can be applied for the treatment of water with high fluoride content.

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Removal of excess fluoride from water by aluminum hydroxide

In this study, the adsorption potential of aluminium-iron-amended activated bamboo charcoal (AIAABC), prepared from waste bamboo, for defluoridation of drinking water was investigated. The adsorbent (AIAABC) in which ABC was impregnated in AlCl3/FeCl3 solution and treated at 400 °C showed higher fluoride uptake capacity. The samples obtained were characterized and tested in batch mode. Inorganic particles were dispersed on the surface of carbon as indicated by SEM images and EDS. The main elements found in AIAABC were carbon, oxygen, aluminium, iron, sodium, and sulfur. Fluoride was associated with the aluminium hydro(oxide) (AO) particles in the pore spaces of ABC after adsorption. Specific surface area (SSA) was reduced from 80.5 to 3.7 m2/g, when ABC was impregnated with AO, indicating that the AO particles might cover the surface or pore spaces found in ABC. Maximum adsorption occurred at pH range from 5 to 9. The adsorption data were well fitted to Langmuir isotherm model with a maximum adsorption capacity of 21.1 mg/g. The adsorption process obeyed a pseudo–second–order rate equation. The adsorbent was effectively regenerated (85.7%) by 0.1% NaOH. Due to its high adsorption capacity compared to commercially available aluminium hydroxide–based adsorbents, AIAABC is a highly promising material for defluoridation of drinking water.

Aluminium-iron-amended activated bamboo charcoal (AIAABC) for fluoride removal from aqueous solutions

In this study, aluminium oxide–manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7 m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F− concentration, and raw water pH) showed that fluoride removal efficiency of AOMO vari...

Water defluoridation by aluminium oxide–manganese oxide composite material

Selenium is an essential element since it is necessary for metabolism and is also toxic to the living things if it is consumed above the desirable limit. For instance, up to 40 µg per d of dietary selenium is essential for human health; however, consumption of a little over 400 µg per d could result in adverse physiological problems. In the environment, selenium occurs in different species; of which selenate and selenite are its most toxic forms accounting for 95% of selenium toxicity. Though, selenium fortification is important for normal human physiology in selenium deficient environments, it needs to be minimized or removed from selenium rich environmental media. Thus, its quantification is significantly important to control per limit. Currently there is advancement in the detection and quantification of selenium in environmental including the use of a Hydride Generating Atomic Absorption Spectroscopy. Due to the excess occurrences of selenium in different locations the removal techniques from geogenic or anthropogenic sources include microbial metabolism, phytoremediation, sorption, membrane separation, coagulation, ion exchange and catalytic reduction. Most of all, the microbial removal is applied in drinking water supply and in selenium recovery from wastewater sludge. Though current selenium removal from sorption studies reported better efficiency, phytoremediation appears attractive due to its field scale application advantage. However, the fate of selenium following phytoremediation remains unaddressed.

/pdf/a-review-on-environmental-selenium-issues-2mj6km9xgt.pdf

Feleke Zewge

Papers

Removal of excess fluoride from water using waste residue from alum manufacturing process

Removal of excess fluoride from water by aluminum hydroxide

Aluminium-iron-amended activated bamboo charcoal (AIAABC) for fluoride removal from aqueous solutions

Water defluoridation by aluminium oxide–manganese oxide composite material

A review on environmental selenium issues