Defluoridation performance comparison of aluminum hydroxides with different crystalline phases

Aluminum hydroxide is an eye catching and extensively researched adsorbent for fluoride removal and its defluoridation performance is closely related to the preparation method and crystalline phase. In this research, the defluoridation performances of aluminum hydroxides with different crystalline phases are compared and evaluated in terms of fluoride removal capacity, sensitivity to pH values and residual Al contents after defluoridation. It is found that the defluoridation performance of different aluminum hydroxides follows the order of boehmite > bayerite > gibbsite. The fluoride adsorption on aluminum hydroxides follows pseudo-second-order kinetic model and Langmuir isotherm model, and the maximum defluoridation capacities of boehmite, bayerite and gibbsite are 42.08, 2.97 and 2.74 mg m−2, respectively. The pH values and FTIR analyses reveal that the ligand exchange between fluoride and surface hydroxyl groups is the fluoride removal mechanism. Different aluminum hydroxides have different surface hydroxyl group densities, which results in the different defluoridation capacities. This work provides a new idea to prepare aluminum hydroxide with outstanding defluoridation performance.

Functional activated carbon: from synthesis to groundwater fluoride removal

Conversion and surface modification of date stems to obtain a relevant adsorbent to remove fluoride contamination.

Review of Fluoride Removal Appropriate Technology for Securing Safe Drinking Water in Africa

Making and securing safe drinking water is considered as the most important element and human right for sustainable human life. However, many countries in Africa still have low access to safe water, and in particular, fluorosis symptoms are severe from the people of Africa where there is a lot of groundwater and surface water contaminated with fluoride due to the geological natures. Fluoride is a colorless, tasteless, and odorless element with very strong reactivity and is emitted from the cleaning process of semiconductors and the fertilizer manufacturing industries. Various technologies such as chemical coagulation/precipitation, electrochemical method, ion exchange, separation membrane technology, nanotechnology, and adsorption may be proposed as a technology for removing fluoride for securing safe drinking water. The strengths and weaknesses of each element technology and recent research cases were investigated and analyzed, and an appropriate technology application plan for the sustainable development of emerging and developing countries in Africa was presented. Efficiency of fluoride removal may be important to secure drinking water for developing countries in Africa, but it is necessary to consider the local economic situation and cultural background first for sustainability of the applied technology. Therefore, animal bone-based adsorption process is advantageous in terms of sustainability and can be proposed as a fluoride removal technology suitable for the developing countries in Africa.

Defluoridation of water by Ce-Ti hybrid oxide nanoparticles

In the present work, Ce-Ti and Ce-Ti/Fe3O4 hybrid oxides were prepared by co-precipitation method and then characterized by X-ray diffraction (XRD), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and scanning electron microscope (SEM) techniques. The nano-adsorbents were applied to remove fluoride (with the concentration range of 10–30 mg L−1) from aqueous solution, reaching the adsorption equilibrium within 30–60 minutes. Practically, the fluoride removal onto both nanomaterials was efficient at the neutral pH (pH 5–7) and obeyed the Langmuir adsorption isotherm with the maximum adsorption capacities of 22.78 mg g–1 (Ce-Ti) and 20.28 mg g–1 (Ce-Ti/Fe3O4) at room temperature.

Adsorption of fluoride from industrial wastewater using polymer adsorbents: a review

Fluoride pollution in ground and surface water originates from naturally occurring reactions and industrial activities such as the disposal of industrial wastewater. Amongst different fluoride removal technologies including chemical precipitation, membrane filtration, ion exchange processes, and electrodialysis, adsorption is an attractive method for fluoride removal from wastewater due to its low operational cost, simplicity, and good sustainability. Various adsorbents are used for fluoride removal including, metal oxides and hydroxide, carbonaceous adsorbents, zeolite, polysaccharides, and polyresin adsorbents. This review studies the application of modified polysaccharides and polyresin adsorbents for the removal of fluoride from wastewater. The relationship between the adsorption conditions and the resulting adsorption capacity is thoroughly discussed. Based on the reported studies, modified polysaccharides and polyresins adsorbents can effectively remove fluoride from wastewater achieving high adsorption capacity, the highest being 92.39 mg/g for aluminum impregnated amberlite at pH 3. Furthermore, aluminum impregnated adsorbents reported a higher fluoride adsorption capacity than other modification methods where the three adsorbents with the highest fluoride adsorption capacity are: aluminum impregnated amberlite 92.39 mg/g at pH 3> zirconium immobilized crossed linked chitosan 48.26 mg/g at pH 6 > chitosan/aluminum hydroxide beads 17.68 mg/g at pH 4. In addition, polymeric adsorbents are also highly sustainable as they can be regenerated multiple times to be reused. Therefore, the high adsorption capacity and good regeneration potential allow polymeric adsorbents to serve as promising and sustainable adsorbents to remove fluoride from industrial wastewater.