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

Fluoride contamination, health problems and remediation methods in Asian groundwater: A comprehensive review.

A review of emerging adsorbents and current demand for defluoridation of water: Bright future in water sustainability.

From pollutant to solution of wastewater pollution: Synthesis of activated carbon from textile sludge for dye adsorption

A review of fluoride in african groundwater and local remediation methods

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

In this study the fluoride removal potential of nanoscale aluminium oxide hydroxide (nano-AlOOH) has been investigated. The material was produced using aluminium nitrate (Al(NO 3 ) 3 . 9H 2 O, 95%), and ammonium bicarbonate (NH 4 HCO 3 , 98%) and its density and mineralogy were investigated. A series of batch adsorption experiments were carried out to assess parameters that influence the adsorption process. The parameters considered were contact time and adsorbent dose, initial fluoride concentration, and pH. Results showed that most of the adsorption took place during the first 30 min; and equilibrium was reached at one hour contact time with an optimum adsorbent dose of 1.6 g L -1 for initial fluorideconcentration of 20 mg L -1 . The removal efficiency of fluorideincreased with increase in adsorbent dosage. The fluoride removal efficiency was increased as the pH of the solution increases from pH 3 to 8, but any further increase in pH led to a decrease in fluoride removal efficiency. Maximum adsorption occurred at around pH 7 with initial fluoride concentration of 20 mg L -1 . The adsorption data were well fitted to the Langmuir isotherm model with a maximum adsorption capacity of 62.5 mg F - g -1 . The kinetic studies showed that the adsorption of fluoride by nano-AlOOH obeys a pseudo-second order rate equation. The intraparticle diffusion was not a rate-controlling step for the adsorption process. Thus, the overall study indicates that nano-AlOOH is an efficient defluoridating material. KEY WORDS : Nanoscale AlOOH, Defluoridation, Fluoride removal efficiency, Adsorption capacity, Adsorption kinetics, Adsorption mechanism Bull. Chem. Soc. Ethiop. 2014 , 28(2), 215-227. DOI: http://dx.doi.org/10.4314/bcse.v28i2.6

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Adsorptive removal of fluoride from water using nanoscale aluminium oxide hydroxide (AlOOH)

In this study, the properties and fluoride-uptake capacity of aluminum hydroxide-based (AO) adsorbent has been investigated. AO was synthesized, characterized, and tested in batch and column experiments. The surface area of the AO was found to be 37.7 m2 g−1. The composition was determined to be 90% Al(OH)2.8(SO4)0.1 (or 78.3% Al(OH)3 plus 10.7% Al2(SO4)3) with 10% Na2SO4 (as an impurity). The material is X-ray amorphous and scanning electron microscopic (SEM) studies show AO to be a network of fibers with a size range of 200–300 nm. Fluoride uptake was found to be unaffected by sodium salts of chloride and sulfate in concentrations up to 500 mg/L. A reduction of fluoride uptake with increasing concentrations of hydroxide and bicarbonate was ascribed to the pH dependence of fluoride sorption, while phosphate appeared to compete with fluoride for sorption sites. The surface site concentration determined by acid–base titrations is 0.5 meq/g (equivalent to a surface site concentration of 8 sites/nm2)...

A high-capacity aluminum hydroxide-based adsorbent for water defluoridation

In this study, the performance of different aluminium hydroxide.based adsorbents was compared in terms of fluoride adsorption capacity, potential for repetitive regeneration, surface acidity and surface site concentrations. The adsorbents were aluminium hydro(oxide) (AO), activated alumina (AA), and pseudoboehmite (PB). The AO adsorbent was synthesised at different OH:Al ratios to optimise the fluoride adsorption capacity. The AO was pilot tested in a rural community in the Ethiopian Rift Valley where groundwaters are heavily enriched with fluoride. The maximum fluoride uptake was achieved for the AO adsorbent synthesised at OH:Al ratios between 2.5 and 2.7. The fluoride adsorption capacity of the adsorbents determined from mini-column studies was found to be 10.6, 1.9, and 2.4 mg/g for AO, AA, and PB, respectively. This significant difference in fluoride adsorption capacity is strongly related to the surface acidity and surface site concentration. The surface acidity (1.57 meq/g) and surface site concentration (0.74 meq/g) for AO is higher than that for AA and PB. The elemental composition analysis showed that AO has a lower % Al2O3 content than AA and PB, but higher sulphate (19.4%) and iron (2.2%) content. High resolution 27Al Magic Angle Spinning Nuclear Magnetic Resonance (27Al MAS NMR) spectra of AO, AA, and PB were recorded, to analyse the coordination geometry of solid Al species and the results showed that aluminium is coordinated octahedrally and tetrahedrally in all cases. Regeneration experiments showed that AA and PB can be regenerated for more than 3 cycles, whereas the potential for regeneration of AO for more than 3 cycles is limited. The results from a community defluoridation plant showed that fluoride in the feed water (8.10 mg/.) is removed below 0.1 mg/.. The average adsorption capacity was determined to be 2.11 mg/g based on continuous field monitoring results obtained until the fluoride content in the treated water exceeded the breakthrough value of 1.5 mg/.. No major operational problems and complaints from the beneficiaries were experienced during operation. Keywords : fluoride, adsorption, surface acidity, regeneration,  defluoridation, Ethiopia

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Eyobel Mulugeta

Papers

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

Water defluoridation by aluminium oxide–manganese oxide composite material

Adsorptive removal of fluoride from water using nanoscale aluminium oxide hydroxide (AlOOH)

A high-capacity aluminum hydroxide-based adsorbent for water defluoridation

Aluminium hydro(oxide)-based (AO) adsorbent for defluoridation of drinking water: Optimisation, performance comparison, and field testing