article · Processes
Phosphate mining generates wastewater with excess fluoride, creating environmental and health risks in water-scarce areas. This research assesses four conventional defluoridation methods on real mine waters sourced from Youssoufia and Khouribga in Morocco. The techniques examined were coagulation-flocculation, chemical precipitation, adsorption with metal oxides, and treatment using calcined bovine bone apatite. While aluminium sulphate removed up to 82.5 percent of fluoride in washing water and aluminium oxide displayed the highest equilibrium adsorption capacity, calcined bone apatite proved to be the most efficient solution overall. It removed around 83 percent of fluoride within 20 minutes in batch trials and continued to perform well in continuous-flow testing, reducing fluoride levels below World Health Organization guideline thresholds despite interference from competing ions present in the real mine water matrices.
High fluoride levels in water from phosphate mining threaten surrounding ecosystems and public health, especially in dry climates where communities rely on limited water supplies. Demonstrating that a waste-derived substance such as calcined bone apatite can successfully treat actual mining effluent to reach international drinking water safety standards offers a practical path towards cleaner mining wastewater and possible water reuse.
This work is relevant to phosphate mining operators and wastewater treatment engineers seeking effective defluoridation methods for industrial effluents. The technology sits at an applied and tested stage, having demonstrated success with real mining effluent in continuous fixed-bed systems. The abstract also notes that combining chemical pretreatment with adsorption could enable industrial effluent reuse, though such integrated systems still require experimental validation.
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Excess fluoride originating from phosphate mining activities poses a significant environmental and public health challenge, particularly in arid and semi-arid regions where water resources are limited. This study presents a comparative evaluation of four conventional defluoridation technologies for the treatment of real phosphate mine waters collected from two major Moroccan phosphate mining sites (Youssoufia and Khouribga). The investigated processes included coagulation–flocculation using aluminum sulfate and ferric chloride, chemical precipitation with calcium hydroxide and calcium chloride, adsorption on aluminum oxide (Al2O3) and zirconium oxide (ZrO2), and fluoride removal using calcined bovine bone apatite under both batch and continuous-flow conditions. Adsorption equilibrium was interpreted using Langmuir and Freundlich isotherm models, while the effects of adsorbent dosage, contact time, and water matrix composition were systematically investigated. Among the coagulation processes, aluminum sulfate achieved fluoride removal of up to approximately 82.5% in phosphate washing water and approximately 76.3% in mine drainage water, whereas ferric chloride removed about 52% of the dissolved fluoride under the reported conditions. Lime and calcium chloride exhibited moderate removal efficiencies of 66% and 61%, respectively. Aluminum oxide showed the highest equilibrium adsorption capacity (qm = 7.14 mg g−1), while zirconium oxide displayed faster fluoride uptake because of its higher surface affinity for fluoride ions. The presence of competing ions in real mine waters was associated with lower adsorption performance compared with synthetic fluoride solutions. Calcined bone apatite proved to be the most effective material, achieving approximately 83% fluoride removal within 20 min under batch conditions and maintaining good performance during continuous fixed-bed operation, producing treated water with fluoride concentrations below the World Health Organization guideline value. Overall, the results demonstrate that calcined bone apatite provides the highest fluoride-removal performance among the investigated materials under the tested conditions. Its waste-derived origin, rapid adsorption kinetics, and effective fluoride removal make it a promising material for the treatment of fluoride-rich phosphate mine waters. The comparative evaluation further indicates that integrating chemical pretreatment with adsorption may represent a promising strategy for the treatment and potential reuse of mining effluents, although the performance of such a combined treatment train should be validated experimentally.
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DOI: 10.3390/pr14172699
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