C-Flow PLT Case Study 1
Destruction of Formic Acid
Clare Fairfield, Senior Scientist
clare.fairfield@ctechinnovation.com
Electrochemistry has potential to contribute to a cleaner environment. One area where its application can be of great benefit is wastewater treatment. Most environmental pollutants canbe successfully eliminated or converted to non-toxic materials
by one or more electrochemical processes, including electrolysis, electrocoagulation and electrocoagulation/flotation andelectro dialysis. This case study will focus on electro-oxidation.
Chemical processes for the treatment of waste water are
known. Polluted waters can be treated with ozone, or other powerful oxidants but the total organic carbon removal islow (approximately 30 % of starting material) . With chemical processes, although the organic pollutants can be nearcompletely eliminated, the level of total organic carbon still
remains a problem. The process also requires the addition ofother chemical reagents which may leave behind unwantedcontaminants. For these reasons, electro-oxidation holds many
advantages over chemical processes. It is applicable to a wide
range of pollutants and does not require high temperature orpressure to complete. The reaction can be driven until full oxidation to carbon dioxide is achieved, reducing the total organic
content to very low levels. This occurs at a significant rate in
the potential region of oxygen evolution and it is commonly
assumed that electro- generated hydroxyl radicals are activein the degradation of organic molecules. The hydroxyl radicals
are produced directly from water according to equation (1);H2O → OH- + H+ + e-		(1)Apparatus
A 5x5 cm C-Flow LAB cell was first used to validate the electrochemical oxidation at a small (1 litre) scale.

Figure 2 – Laboratory scale test equipment
After validation in the laboratory, the reaction was completedwith the C-Flow PLT cell and test platform, operating in 10-50
L volume scale.

C-Tech Innovation are market-leading in the creation and validation of electrochemical systems, some of which have been
toward wastewater treatment including extensive collaboration and supply to the nuclear industry.
In this case study the direct electro-oxidation of formic acidis demonstrated, first at a laboratory scale using a C-Flow Lab
5x5 electrochemical cell and compared with results achieved
at pilot scale with the C-Flow PLT unit. Formic acid was chosen due to its simplicity. Having only one carbon, the reaction
proceeds quickly and requires only two electrons for oxidation
to carbon dioxide. The reaction pathway is shown in Figure 1.

Figure 1; formic acid oxidation mechanism
Figure 3: C-Flow PLT

C-Flow is a registered trademark of C-Tech Innovation Ltd

C-Tech Innovation Ltd Capenhurst
Technology Park CH1 6EH
United Kingdom+44 (0) 151 347 2900
info@ctechinnovation.com
www.ctechinnovation.comThe C-Flow PLT cell has an active area of 20 x 30 cm (600cm2).
The components of used in both cells were;

Results
The charts in Figure 4 and Figure 5 show the decrease in total organic content in the anolyte solution over time for thelaboratory and pilot scale test respectively. Both show a linear
decline over the concentration range tested.

Table 1: Organic destruction cell components
MaterialAnodeDSA

AnolyteNitric acid (3M, Puriss reagent grade, Sigma Aldrich
LOT SZBD0390V) with 3%
w/w addition of formic acid(Sigma Aldrich, >95%, MKBV5742V).

Membrane

Nafion 324

CathodeTitanium

Catholyte

Nitric acid (3M, Puriss reagent grade, Sigma Aldrich
LOT SZBD0390V)

Figure 4: Decline in total organic carbon
in laboratory scale experiment

Bulk electrolysis experiments were carried out with a power
supply of suitable specification to deliver current required tooperate at 4000 A/m2 (10 A) for the lab cell and 2000 A/m2(125 A) for the pilot cell.
To effectively compare the two cell types, the electrolyte flow
rates were adjusted so that a similar flow velocity (0.2 m/s)
could be achieved through both cell sizes.This equated to 3L/min
through the C-Flow Lab cell and 18L/min through the C-Flow PLT.
The destruction of organic in the anolyte solution was measured
by frequently sampling the anolyte tanks in both experiments
and measuring the total organic carbon (TOC) in solution.This
was completed by a colorimetric technique using Hach Lange
cuvettes (tests LCK 381) and spectrometer (DR500).

Figure 5: Decline in total organic carbon in pilot scale
In order to compare the performance in both experimental
scales, the organic oxidation (in moles) per Amp of current
applied was calculated and plotted over time. This shows thatthe oxidation rate is remarkably similar.

Figure 3 – TOC Measurements

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Figure 6: Performance comparison – LAB versus PLT

C-Tech Innovation Ltd Capenhurst
Technology Park CH1 6EH
United Kingdom+44 (0) 151 347 2900
info@ctechinnovation.com
www.ctechinnovation.com

Table 2 shows the cumulative current efficiency calculated inboth the laboratory and pilot scale electro-oxidation of formicacid. At both scales a comparable and high current efficiency
has been achieved.
Table 2: Current Efficiency Comparison

Current efficiency (%)

LAB

PLT

80.3

79.5

Conclusions
Electro-oxidation is a useful and effective tool in the removalof unwanted organics in waste waters. In this case study, thedestruction of formic acid has been demonstrated, with themethod initially developed and checked at a laboratory scale
before proceeding to effectively scale up the reaction to pilot
scale. The results achieved with the C-Flow Lab 5x5 cell werereadily replicated with the C-Flow PLT.

C-Flow is a registered trademark of C-Tech Innovation LtdC-Tech Innovation Ltd Capenhurst
Technology Park CH1 6EH
United Kingdom+44 (0) 151 347 2900
info@ctechinnovation.com
www.ctechinnovation.com