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. 2022 Oct 10;10(10):598. doi: 10.3390/toxics10100598

Table 4.

Electrochemical degradation of selected NSAIDs using a carbon-based electrode.

Compound Anode Material Removal% Main Byproducts Observations References
Diclofenac BDD 100% (TOC)
100% (DIC)
  • -

    Carboxylic acids: malic acid; tartaric acid; succinic acid; oxalic acid; oxamic acid

  • -

    Aromatic compounds

  • -

    2,6-dicloroaniline (C6H5NCl2)

  • -

    2,6-dichlorohydroquinone (C6H4O2Cl2)

  • -

    2-hydroxyphenyl acetic acid (C8H8O3)

  • -

    2,5-dihydroxyphenyl acetic acid (C8H8O4)
  • -

    The removal of TOC was achieved after 360 min under these conditions: 175 mg/L DIC, 0.05 M Na2SO4, pH 5.8 and current of 450 mA

  • -

    The removal of diclofenac was achieved after 190 min under same above conditions

  • -

    Thin-film BDD was 3 cm2

  • -

    Diclofenac concentration was monitored using HPLC

  • -

    Carboxylic acid were analyzed using exclusion chromatography

  • -

    Aromatic compounds were analyzed using GC-MS

 [98]
Graphite felt 88% NS
  • -

    Graphite was as a cathode

  • -

    This removal was the best compared to other cathode materials such as stainless steel and aluminum after 2 h

  • -

    Electrochemical cell size was 500 cm3

  • -

    Surface area was 50 cm2

  • -

    Distance between electrodes was 1 cm

  • -

    Electrochemical degradation was as three-dimensional electrochemical (3DE) reactor

 [102]
BDD disk 100% (DIC)
100% (TOC)		 NS
  • -

    BDD electrode dimensions were: length 16 cm, height 4 cm and surface area 64 cm2

  • -

    Diclofenac was monitored using UV-visible spectrophotometer

  • -

    Electrochemical cell size was 10 mL

  • -

    Complete removal was observed for diclofenac and TOC after 50 and 250 min, respectively, under these conditions: 0.5 M NaClO4, 150 mg/L DIC, 330 mg L−1 COD

 [117]
Graphite-PVC 100% (DIC) Several byproducts were generated in both positive and negative ionization modes, so we presented the main byproducts only:
C6H5OCl2; C11H8O4NCl3;
C14H11O3NCl2; C13H8ONCl5
  • -

    Electrochemical cell size was 100 mL

  • -

    Graphite-PVC pellet was 10 mm in diameter

  • -

    Diclofenac was monitored using LC-TOF/MS

  • -

    Complete removal was observed after 40 min under these conditions: 6 volts, 4 g L−1 NaCl, 5 mg L−1 DIC

 [103]
BDD thin-film 100% (DIC) Several byproducts were generated, so we presented the main byproducts only:
C14H11O3NCl2; C13H9O3NCl2;
C13H9O2NCl2
  • -

    Complete removal was achieved after 60 min at 292 mA cm−2

  • -

    Degradation efficiency was very influenced by current density

  • -

    Thickness of BBD layer was 5–7 µm while its surface area was 24 × 50 mm2

  • -

    Diclofenac was monitored using HPLC

 [110]
Activated carbon fiber 100% Several byproducts were generated, so we presented the main byproducts only:
C14H11O3NCl2; C13H11O2NCl2
C13H11ONCl2, C13H9ONCl2
  • -

    The removal% observed was after a combination of permanganate oxidation and electrolysis using activated carbon fiber as a cathode

  • -

    Complete removal was achieved after 10 min under these conditions: 20 µm DIC, current density 57 A m−2, and permanganate dosage 100 µM

  • -

    Experimental electrolysis reactor dimensions were 9 cm inner diameter and 12.5 cm height

  • -

    Surface area of ACF was 17.5 cm2

  • -

    The distance between the two electrodes was 1 cm

 [111]
ND-BDD 72% (DIC) Several byproducts were generated, so we presented the main byproducts only:
C14H9O3NCl2; C15H13O2NCl2
C14H10O2NCl3
  • -

    Dimensions of electrode NB/BDD were 6 µm in thickness, 40 cm2, and (10 cm × 5 cm × 2 mm) cylindrical shape

  • -

    Different electrolytes were used (Na2SO4, NaH2PO4, NaNO3)

  • -

    Removal% was observed under these conditions: 50 µM DIC, current density 50 mA cm−2, 30 mM Na2SO4, and 30 min electrolysis time

 [118]
BDD 72% (TOC) Several chlorinated and non-chlorinated byproducts were formed, such as:
2,6 -dichlorobenzeneamine;
1-(2,6-Dichlorocyclohexa-2,4-dienyl)indolin-2-one;
2,5-Dihydroxyl-benzeneacetic acid;
2.5-Dihydroxybenzyl alcohol;
Oxalic acid; benzoic acid
  • -

    The reactor size is 100 mL

  • -

    Surface area of the BDD anode is 12 cm2

  • -

    The concentration of diclofenac was 30 mg L−1

  • -

    GC-MS and LC-TOF/MS instruments were used to analyze the byproducts

  • -

    TOC removal was achieved after 4 h of the electrochemical degradation process

 [112]
Ketoprofen BDD 100% (KTP)
36% (COD)		 NS
  • -

    Electrode surface was 12.5 cm2

  • -

    Gap separation between two electrodes was 0.1 cm

  • -

    Ketoprofen removal was monitored using high-performance liquid chromatography (HPLC)

  • -

    Optimum conditions were pH 3.99, oxygen flow rate = 1.42 mL min−1, current density = 235 mA cm−2 and Na2SO4 = 0.5 mol L−1

 [105]
Thin-film BDD 45–100% (KTP)
>90% (TOC)		 Aromatic compounds:
3-acetylbenzophenone (C15H12O2)
3-hydroxyethyl benzophenone (C15H14O2)
Benzophenone (C13H10O)
3-ethyl benzophenone (C15H14O)
Carboxylic acid:
Ten compounds, most of them are formic acid, acetic acid, malic acid, oxalic acid, and so on.
  • -

    Experimental conditions were 0.198 mM DIC, 50 mM Na2SO4 and 250 mL solution

  • -

    Removal% was based on the wide range of current density from 100 mA to 2000 mA

  • -

    High removal% in terms of TOC was achieved after 10 h

  • -

    Ketoprofen was monitored using HPLC

  • -

    Surface area was 24 cm2

 [104]
Thin-film BDD 100% (TOC) NS
  • -

    Surface area was 11.25 cm2

  • -

    Electrochemical cell size was 250 mL

  • -

    The distance between electrodes was 10 mm

  • -

    Ketoprofen was monitored using a UV-visible spectrophotometer

  • -

    Complete mineralization was observed after 12 h under these conditions: 0.1 M Na2SO4, 8.8 mA cm−2 current density, and 5 µM ketoprofen

  • -

    Na2SO4 exhibited better removal compared to NaCl and NaNO3

 [100]
Ibuprofen Black carbon 60% NS
  • -

    It was achieved after 60 min under these conditions: 5 mg L−1 IBU, 0.05 M Na2SO4, 0.03 A, and pH not changed

  • -

    Removal was influenced by initial concentration, current, and Na2SO4 concentration

  • -

    Ibuprofen was monitored by HPLC

 [119]
BDD 70–90% (TOC) -different organic compounds were produced (data not shown).
-carboxylic compounds:
Maleic acid; oxamic acid; acetic acid; formic acid
  • -

    Surface area was 5 cm2

  • -

    100 cm3 is the size of the electrochemical cell

  • -

    Distance between two electrodes was 1 cm

  • -

    30 pharmaceuticals were spiked in wastewater samples and then treated

  • -

    The observed removal% was provided after 300 min, and it was very influenced by the type of electrolyte and its concentration and current density

 [120]
BDD 60–95% (COD)
48–92% (TOC)		 One compound has been reported:
[2-(4-carboxycarbonyl)phenyl] propanoic acid (C11H10O5)
  • -

    Removal% was achieved after 6 h

  • -

    Concentration of ibuprofen was 1.75 mM

  • -

    Concentration of electrolyte (Na2SO4) was 0.035 M

  • -

    200 mL of ibuprofen solution was used

 [112]
BDD
CNT
GC		 BDD = 50%
CNT = 75
GC = 45		 NS
  • -

    Three different carbon-based electrodes were provided

  • -

    CNT exhibited better degradation in the presence of chloride and sulfate as support electrolytes

  • -

    Removal% in terms of COD and TOC were 69 and 27.5%, respectively, using the CNT anode

  • -

    Electrochemical cell was 100 cm3

 [113]
Thin-film BDD >95%
91–96% (TOC)		 Aromatic compounds:
P-benzoquinone
4-isobutyhlphenol,
4-isobuthylacetophenone

Carboxylic acid:
Oxalic acid, glyoxylic acid, formic acid, acetic acid, and pyruvic acid
  • -

    High removal was observed after 90 min

  • -

    Influence of pH, current, and initial concentration of IBU was investigated

  • -

    Electrochemical cell with a 6 cm diameter and 0.2 L capacity was used

  • -

    Presence of NaCl exhibited better removal% compared to Na2SO4

  • -

    High removal% of TOC was achieved after 8 h

 [106]
Naproxen MWCNTs-GCE >80% (NPX)
>60% (TOC)		 Several byproducts were generated, so we presented the main byproducts only:
C13H12O2; C13H14O2;
C12H10O2; C12H10O3
  • -

    Electrode was prepared after deposition of multiwall carbon nanotubes (MWCNTs) on glassy carbon electrode (GCE)

  • -

    Naproxen was monitored using HPLC

  • -

    Removal% was observed after 25 min and 19 mg/L NPX

 [121]

NS: not studied.