3.1.4. Effect of the nature of the electrolyte
As aforementioned, the synthetic solution had not the required
conductivity to perform the electrochemical experiments; hence
two electrolytes were tested, NaCl and Na2SO4 at a concentration
of 1.5 g/L, in order to increase the effluent’s conductivity and
decrease the energy consumption. This way, the initial conductivity
of the effluent became 3.0 and 2.5 mS/cm after the introduction of
chlorine and sulphate salts, respectively. From the results
(Fig. 5a and b) it was found out that at the end of 30 min, NaCl led
to better degradation values (TPh removal = 84.0% and COD
removal = 51.1%) than the ones achieved with Na2SO4 (TPh
removal = 62.1% and COD removal = 15.4%). In the presence
of both salts it occurs the generation of oxidizing species
ðCl2; HClO;ClO and S2O2
8 Þ which are able to react with organic
compounds during electrolysis [33]. The difference between the
two electrolytes may be explained by the fact that the NaCl solution
provides higher conductivity to the effluent and the chemical species
that are formed are good oxidant reagents to decompose
organic compounds, thereby improving the process efficiency.
Moreover, moderate levels of chloride ions in solution decrease
the passivation layer on the surface of the sacrificial anodes, increasing
the removal efficiency of contaminants in the ECG process [34].
In addition, through the analysis of the evolution of the pH in the
medium (Fig. 5c) and according to the Pourbaix diagram, one can
foresee that in the experiment with Na2SO4, the short time in neutral
pH may have reduced the dose of coagulants and, on the other hand,
the alkaline medium may have led to the formation of an oxide layer
on the surface of the zinc electrode which prevents the dissolution of
the metal, limiting also, this way, the coagulant generation. Thus the
efficiency of the electrocoagulation process is inhibited [35].
3.1.4. Effect of the nature of the electrolyteAs aforementioned, the synthetic solution had not the requiredconductivity to perform the electrochemical experiments; hencetwo electrolytes were tested, NaCl and Na2SO4 at a concentrationof 1.5 g/L, in order to increase the effluent’s conductivity anddecrease the energy consumption. This way, the initial conductivityof the effluent became 3.0 and 2.5 mS/cm after the introduction ofchlorine and sulphate salts, respectively. From the results(Fig. 5a and b) it was found out that at the end of 30 min, NaCl ledto better degradation values (TPh removal = 84.0% and CODremoval = 51.1%) than the ones achieved with Na2SO4 (TPhremoval = 62.1% and COD removal = 15.4%). In the presenceof both salts it occurs the generation of oxidizing speciesðCl2; HClO;ClO and S2O28 Þ which are able to react with organiccompounds during electrolysis [33]. The difference between thetwo electrolytes may be explained by the fact that the NaCl solutionprovides higher conductivity to the effluent and the chemical speciesthat are formed are good oxidant reagents to decomposeorganic compounds, thereby improving the process efficiency.Moreover, moderate levels of chloride ions in solution decreasethe passivation layer on the surface of the sacrificial anodes, increasingthe removal efficiency of contaminants in the ECG process [34].In addition, through the analysis of the evolution of the pH in theขนาดกลางกินซี 5) และตามแผนภาพ Pourbaix หนึ่งสามารถเล็งเห็นที่ในการทดลองกับ Na2SO4 ในเวลากลางค่า pH อาจลดปริมาณ coagulants และ ในทาง กลับกันสื่อด่างอาจได้นำไปสู่การก่อตัวของชั้นออกไซด์ที่บนผิวหน้าของอิเล็กโทรดสังกะสี ซึ่งทำให้การยุบโลหะ ยัง จำกัดด้วยวิธีนี้ รุ่น coagulant ที่ ดังนั้นการประสิทธิภาพของกระบวนการ electrocoagulation เป็นห้าม [35]
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