Treatment of thin film transistor-liquid crystal display (TFT-LCD) wastewater by the electro-Fenton process

• Electro-Fenton process was used to treat TFT-LCD wastewater.
• Significant variables affecting DMSO removal: Fe2+ loading > pH > H2O2 loading.
• Decrease in solution pH due to presence of acidic degradation intermediates.
• Real TFT-LCD wastewater was treated using the electro-Fenton process.

In this study, the electro-Fenton process was used to treat synthetic and actual TFT-LCD wastewaters. TFT-LCD wastewater contains high amounts of organic solvents mainly dimethyl sulfoxide (DMSO). For the simulated TFT-LCD wastewater, response surface methodology (RSM) was used to fit experimental data to empirical models with the responses, %DMSO removal and H2O2 efficiency (Δ[H2O2]/Δ[DMSO]). Among the studied independent variables that affect DMSO degradation efficiency, Fe2+ loading was found to be the most dominant, then pH and, H2O2 loading being the least significant. DMSO removal and H2O2 efficiency improved with high Fe2+ loading, low H2O2 loading and low solution pH. The observed decrease in pH was attributed to the production of acidic degradation intermediates of DMSO. At 5 mM DMSO loading, treatment efficiency reached 100% DMSO removal. The electro-Fenton technology was also applied to real TFT-LCD wastewater resulting in TOC and COD removals of 68% and 79%, respectively.