Electrodialysis for fluoride and nitrate removal from synthesized photovoltaic industry wastewater

Fluoride and nitrate ions are the main pollutants in the photovoltaic cells manufacturing effluent. Their presence in the effluent is due to the extensive use of HF and HNO3 acids during the silicon wafers production process. This work deals with the electrodialysis application to remove these ions. Synthetic solutions were used for the investigation of the main operational factors affecting the treatment performance; such as current intensity, initial pollutants concentration and pH. Significant fluoride removal was obtained in an acidic or neutral medium after a relatively short treatment time of 6 min. Nitrate ions were also removed showing an efficiency of 98% after 18 min of treatment using a current intensity of 0.1 A and for an initial concentration of 1000 ppm. The study of competition between these two ions during their eliminations showed that the fluoride ions presence does not affect the nitrate removal, while; the nitrate ions presence in the solution delays the fluoride removal from 7 to 20 min, and makes the removal less effective. The results obtained can be used to optimize the pollutant removal recovery at large scale.