Analysis of Fluoride Precipitation Mechanisms and Optimization Techniques for Mine Water Remediation
DOI:
https://doi.org/10.66021/Keywords:
Fluoride Removal, Mine Drainage, Chemical Precipitation, PHREEQC, Optimization, RSM, Calcium Chloride, Lanthanum Chloride, Water TreatmentAbstract
Background:
Fluoride pollution in the mine drainage is of the most serious concern to water chemistry, human health, and aquatic ecosystem. Being present in much higher concentrations than World Health Organization (WHO) guidelines, require efficient and easy-to-implement remediation techniques, particularly in areas affected by phosphate, coal and uranium mines.
Aim: In this study, chemical and statistical methods are used to examine the mechanism of fluoride precipitation and present an optimally designed treatment process for mine drainage treatment.
Method: Some of the precipitation agents such as calcium, aluminum, and lanthanum were studied at lab scale on batch mode at different pH, dosages, and contact time. the pre- and post-treatment fluoride levels were determined by ion-selective electrodes. From them it was possible to interpret the saturation and precipitation of fluoride minerals as reportedoftheseauthors. thermodynanic computations and kinetic analysis using PHREEQC were runed. Treatment parameter optimization was performed using Response Surface Methodology (RSM), and field verification was carried out for mine water samples from three locations.
Results: The optimal conditions of calcium and lanthanum salts removal of fluoride were obtained, and the fluoride removal rate of lanthanum chloride could be up to more than 99%. The best results of precipitation were found at pH 6.5–7.5 and prolonged contact time yielded little increases after 60 min. The experimental results were also in agreement with the thermodynamic, statistical models and then validated in the field (~93% fluoride rejection efficiency to various mine drainage samples).
Conclusion: The application of fluoride precipitation for mine water treatment is considered to be a suitable, cost-effective, and flexible process, particularly if it is optimized by statistical and geochemical modeling tools as were used in the present study.
