Study Of Phenolic Wastewater Treatment By Pulse Electrolysis

Nguyen Ngoc Long, Dalian Maritime University Abstract of Master’s Thesis, Submitted June 12th 2015 Study of Phenolic Wastewater Treatment by Pulse ElectrolysisThe purpose of this study is to investigate the possibility of using pulse electrolysis to remove phenol from wastewater. The removal rate of phenol was explored in terms of various parameters in batch mode namely:electrode material, operating time, pH, and concentration of sodium chloride, addition of sodium sulphate, initial current, pulse frequency, voltage, and flow rate. In order to throw some light on the economics of the process, chemical oxygen demand values, concentration of phenol before after treatment and energy consumption values were assemblage and made comparison for discovering optimum electrolysis operation.In this work, there are 5 different kinds of electrode which were made of different materials. Based on the result after experiment, Ti/Ir was chosen as the best anode and copper as the best cathode. These electrodes bring us better treatment result than the other kind in the same condition. The energy consumption is also very less.To find out the reaction time which can satisfy those requirements:low energy consumption, higher removal rate? So many experiments were conducted, and take samples at different points of time. Based on results and analysis,30 minutes is as a suitable time for experiment.After finding the appropriate electrode, and a reasonable reaction time, the effect of solutions properties study had been concerned, too. They include:pH, conductivity, concentration of sodium chloride. With the changing sodium chloride concentration from 0.5 to 7 g/L, the best result occurred when concentration of Sodium chloride is 5.5g/L. With the higher of Sodium chloride (more than 5.5g/L), the high removal rate was appeared too:about 98%. But, it leads to the higher concentration of ion chloride in solution, so the chemical oxygen demand is also increased. Furthermore, put more will be wasting sodium chloride.During the researching these results:pH value before and after reaction, energy consumption, removal rate. A conclusion was showed for pH value:optimum pH for the electrolysis is about 6.5 to 7.2. When the environment of solution is a strong alkaline one or strong neutral one, removal rates are not good, and that kind of solution will reduce the reliability of the electrodes.For knowing about conductivity, sodium sulphate was applied to control the ion density in solution. After analysis experiments result, some inference was concluded, higher conductivity will make energy consumption reduce, but the removal rate also falls too.Properties are the most important factor for researching. With these requirements:low energy consumption and high removal rate. But higher current will bring higher energy consumption. After concerned every data and result, current 1A, frequency 3000Hz was chosen as standard value.The final condition which was examined is flow rate. Experiments result shows that:too fast or too slow flow rate will have bad effect on reaction. The optimum flow rate for operation is 120ml/minute.Finally, the optimum conditions were found:constant 1=1 (A), Frequency= 3000 (Hz), Ti/Ir anode, Copper cathode, reaction time is 30 minutes,5.5 g/L Sodium chloride, lg/L Sodium Sulphate, initial pH= 7, flow rate is 120 ml/minute.The study revealed that the optimum conditions for the removal of phenol was achieved at used Ti/Ir as anode, Cu as cathode, operating time is 30 minutes, pH is about 7, sodium chloride concentration is 5.5 g/L, addition of sodium sulphate is 1 g/L, initial current is 1 A with the changing voltage, pulse frequency= 3000 Hz and flow rate is about 120 mL/minute. Noteworthy removal of 99% of phenol had been achieved for 100 mg/L phenol concentration with the low energy consumption (15.37 Wh for each gram phenol). The new design of pulse electrolysis seems to be a promising method, and it can be widely applied in reality.