A hybrid electrocoagulation-adsorption process for fluoride removal from semiconductor wastewater

Abstract

Semiconductor processing facilities regularly emit wastewater with fluoride concentrations exceeding 100 mg/L which can cause major health issues in the local population. This research aims to address this issue by optimising an electrocoagulation-adsorption (EC-AD) process using two aluminium electrodes and activated carbon. The applied voltage (5, 15, and 20V) and adsorbent dosage (0.20, 0.50, and 1.00g) parameters were varied to treat a synthetic wastewater solution containing 100 mg/L of fluorine. It was found that fluoride removal efficiencies are significantly affected by the adsorbent dosages and applied voltages used. Increasing the applied voltage from 5V to 20V increased the removal efficiency from 37.55% to 64.25% for 0.2g adsorbent dosage and from 33.85% to 67.25% for 0.5g dosage. After all the parameter combinations were tested, an applied voltage of 20V and an adsorbent dosage of 0.50g produced the maximum fluoride removal efficiency. These parameter values thus define the optimal conditions for the EC-AD process to reduce fluoride from highly concentrated wastewater. The AD, EC, and hybrid EC-AD process achieved fluoride removal efficiencies of 2.86%, 41.13%, and 67.25% respectively from synthetic wastewater. Therefore, it was showed that the combination EC-AD process performs better than adsorption (AD) or electrocoagulation (EC) processes used in isolation.

Electrocoagulation as a Promising Defluoridation Technology from Water: A Review of State of the Art of Removal Mechanisms and Performance Trends

“…For this reason, several researchers are moving toward combined EC processes to increase pollutants removal efficiency, such as fluoride found in drinking water. EC process can be used as a pre-or post-polishing process depending on the type of contaminants present in water [101][102][103][104][105].…”

“…They reported that using NaCl as a supporting electrolyte (200 NaCl mg L −1 ), the fluoride removal efficiencies were 83%, 93.46%, and 95% for EC alone, EC-adsorption with tri tricalcium phosphate processes, and EC-adsorption with activated alumina, respectively. The second contribution to the application of EC-adsorption processes was performed by Jalil et al [102]. They used aluminium plates as anode and cathode and activated carbon as an adsorbent.…”

Removal of fluoride ions from aqueous solution by metaettringite

“…High fluoride content is commonly found in wastewaters from industries including the mining [ 4 ], semiconductor [ 5 , 6 ], fertilizer [ 7 , 8 ] and photovoltaic [ 9 ] sectors. This means that a broad range of options to remove fluoride and prevent fluoride contamination are needed.…”

Comparison of Electrocoagulation Coupled With Synthetic Zeolite, Ultrasound and Two Steps Electrocoagulation

“…However, due to the increased complexity of the composition of produced wastewater, the application of EC as a stand-alone is not enough to obtain effluent suitable for further discharge into sewage. Recently, efforts are being made to develop hybrid or combined processes, which combine EC with other physical, chemical, or biological processes, carried out simultaneously or sequentially (one after the other), in order to overcome the limitations of individual processes [9,10]. An example of such a process is electrocoagulation in combination with zeolite [11,12].…”