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Ciencias Químicas

PHOTOELECTROCHEMICAL DEGRADATION OF IMATINIB MESYLATE

USING A BDD/TIO

PHOTOANODE: A SHORT COMMUNICATION

DEGRADACIÓN FOTOELECTROQUÍMICA DE MESILATO DE IMATINIB

UTILIZANDO UN FOTOÁNODO BDD/TIO

: UNA COMUNICACIÓN CORTA

DEGRADACAO FOTOELETROQUIMICA DO MESILATO DE IMATINIB

UTILIZANDO UM FOTOÂNODO BDD/TIO

: UMA COMUNICACAO CURTA

Autores:

# Steven Mateo Vélez Zambrano

1,2

svelez6538@utm.edu.ec

# G. Xavier Castillo-Cabrera

GXCASTILLO@puce.edu.ec

# Gustavo Altamirano-Briones

2,3

gustavo.altamirano@alu.uhu.es

# Patricio Javier Espinoza-Montero

1,∗

pespinoza646@puce.edu.ec

Pontiﬁcia Universidad Católica de Ecuador, Quito,

Ecuador

Universidad Técnica de Manabí, Portoviejo, Ecuador

Programa de Doctorado en Ciencia y Tecnología Industrial

y Ambiental, Universidad Huelva, Huelva, España

* Autor para correspondencia.

Editor Académico

Jesús Ágreda

Citación sugerida: Velez Zambrano, S.M., Castillo Cabrera,

G.X., Altamirano-Briones, G., Espinoza-Montero, P.J. (2025).

Photoelectrochemical degradation of imatinib mesylate

using a BDD/TiO

photoanode: A short communication.

Revista Bases de la Ciencia, 10(3), 30-43. DOI: 10.33936/rev-

basdelaciencia.v10i3.7677

Recibido: 28/06/2025

Aceptado: 17/11/2025

Publicado: 17/12/2025

Abstract

Imatinib (IMB) is an enzymatic inhibitor that prevents the proliferation of cancer cells. It is

used to treat certain types of cancer, such as leukemia, and is also effective in the treatment

of speciﬁc gastrointestinal stromal tumors and dermatoﬁbrosarcoma protuberans. After

administration, it is excreted through urine and feces. The concentration of IMB in the

environment is increasing rapidly, leading to serious environmental and human health

concerns. This study employs a boron-doped diamond photoanode modiﬁed with titanium

dioxide (BDD/TiO

) for the degradation of IMB via photoelectrocatalysis. The research

was divided into three stages: i) modiﬁcation of the BDD electrode through electrophoretic

deposition of synthetic TiO

nanoparticles; ii) electrochemical characterization of the

BDD/TiO

photoanode; iii) degradation of imatinib (24 mg L

−1

) through electrochemical

oxidation using BDD and photoelectrocatalysis with BDD/TiO

at various current densities

over 90 minutes. Degradation and mineralization were monitored using UV spectroscopy

and chemical oxygen demand (COD) analysis. The highest photoelectrocatalytic degradation

rate of IMB reached 84.09 % when applying a current density of 8.26 mA cm

−2

Keywords: Imatinib mesylate (IMB), Photoelectrocatalysis (PEC), Photoanode, Electrophore-

tic deposition, Boron Doped Diamond (BDD), Titanium Dioxide (TiO

Resumen

El imatinib (IMB) es un inhibidor enzimático que previene la propagación de las células

cancerosas. Se utiliza para tratar ciertos tipos de cáncer, como la leucemia. También es

útil para el tratamiento de ciertos tipos de tumores del estroma gastrointestinal y del

dermatoﬁbrosarcoma protuberante. Tras su consumo, se elimina mediante la orina y

materia fecal. La cantidad de IMB en el ambiente está creciendo rápidamente, causando

serios problemas ambientales y en la salud humana. Este estudio utiliza un fotoánodo

de Diamante Dopado con Boro modiﬁcado con Dióxido de Titanio (BDD/TiO

) para la

degradación de IMB mediante fotoelectrocatálisis. El estudio se dividió en tres etapas: i)

modiﬁcación del BDD mediante deposición electroforética de nanopartículas sintéticas

de TiO

; ii) caracterización electroquímica del fotoánodo BDD/TiO

; iii) degradación de

imatinib (24 mg L

−1

) mediante oxidación electroquímica con BDD y fotoelectrocatálisis

sobre BDD/TiO

a diferentes densidades de corriente durante 90 min. La degradación

y mineralización se monitorearon mediante espectroscopia UV y demanda química

de oxígeno. La tasa máxima de degradación fotoelectrocatalítica del IMB fue del 84.09 %,

aplicando una densidad de corriente de 8.26 mA cm

−2

Palabras clave: Mesilato de imatinib (IMB), Fotoelectrocatálisis (FEC), Fotoánodo, Depósito

electroforético, Diamante Dopado con Boro (BDD), Dióxido de Titanio (TiO

Resumo

O imatinibe (IMB) é um inibidor enzimático que impede a proliferação de células cancerígenas.

É utilizado no tratamento de certos tipos de câncer, como a leucemia. Também é eﬁcaz

no tratamento de determinados tipos de tumores do estroma gastrointestinal (GIST) e do

dermatoﬁbrossarcoma protuberante. Após sua administração, é eliminado por meio da urina

e das fezes. A concentração de IMB no ambiente está aumentando rapidamente, causando

sérios problemas ambientais e riscos à saúde humana. Este estudo utiliza um fotoânodo

de diamante dopado com boro, modiﬁcado com dióxido de titânio (BDD/TiO

), para a

degradação do IMB por meio da fotoeletrocatálise. A pesquisa foi dividida em três etapas: i)

modiﬁcação do eletrodo BDD por deposição eletroforética de nanopartículas sintéticas de

TiO

; ii) caracterização eletroquímica do fotoânodo BDD/TiO

; iii) degradação do imatinibe

(24 mg L

−1

) por oxidação eletroquímica com BDD e fotoeletrocatálise com BDD/TiO

sob

diferentes densidades de corrente durante 90 minutos. A degradação e a mineralização foram

monitoradas por espectroscopia UV e pela análise de demanda química de oxigênio (DQO).

A taxa máxima de degradação fotoeletrocatalítica do IMB foi de 84.09%, aplicando uma

densidade de corrente de 8.26 mA cm

−2

Palavras chave: Mesilato de imatinibe (IMB), Fotoeletrocatálise (FEC), Fotoânodo, Deposição

eletroforética, Diamante dopado com boro (BDD), dióxido de tiânio (TiO

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1. Introduction

The large-scale production and consumption of pharmaceutical compounds have become a major environmental

concern, as most of these substances ultimately reach and contaminate natural water sources (Vasilachi et al., 2021).

Although their residual concentrations are typically low, many pharmaceuticals can bioaccumulate and enter the

trophic chain, leading to long-term adverse effects on plants, animals, and human health (Gondi et al., 2022).

Cytostatic drugs (CDs) are classiﬁed as contaminants of emerging concern (CECs) because they are not currently

regulated, despite their well-documented toxicological and ecological impacts (Domingo-Echaburu et al., 2022).

Among these compounds, imatinib mesylate (

O · CH

; IMB) stands out as the ﬁrst clinically approved

protein kinase inhibitor used in cancer therapy. Unlike most CDs, IMB does not interact directly with DNA, offering

a more selective and promising therapeutic approach. As a result, its global consumption has increased exponentially

(Novak et al., 2017). IMB exhibits high bioavailability (approximately 98 %) and is primarily excreted through feces

(68 %) and, to a lesser extent, urine (13 %) (Serna Siatova & Cárdenas Losada, 2018).

Environmental studies have revealed growing concern regarding the persistence of IMB in aquatic ecosystems.

Novak et al. (2017) reported IMB concentrations in European water bodies ranging between 3.3 and 5.0 ng

−1

, levels

initially considered below ecotoxic thresholds. However, subsequent monitoring by the same group in 2021 revealed

an increase to 13 ng

−1

, more than doubling the previous concentrations and highlighting the escalating issue of

pharmaceutical residues in the environment (Novak et al., 2021). In toxicological studies, IMB exposure was shown

to induce mutagenic effects in mice, including hyperplasia of the interstitial cells of Cajal and retention of intestinal

contents in the caecum (Klein-Rodewald et al., 2022).

The continuous rise of IMB contamination underscores the urgent need for effective and sustainable treatment

strategies. In this context, advanced oxidation processes (AOPs) have emerged as promising technologies for

degrading persistent and complex pollutants such as CECs (Mishra et al., 2023). Among AOPs, photoelectrocatalysis

(PEC) has attracted particular attention due to its high efﬁciency, environmental compatibility, and ability to

mineralize recalcitrant organic contaminants.

PEC operates through a three-step mechanism: (i) a photocatalyst deposited on a conductive substrate

(photoelectrode) absorbs incident photons, promoting electrons from the valence band (VB) to the conduction

band (CB) and generating electron–hole pairs; (ii) an external bias potential is applied to extract photogenerated

carriers, thereby enhancing charge separation and minimizing recombination; and (iii) the resulting holes (h+) in

the VB drive oxidation reactions, ideally producing hydroxyl radicals

· OH

from water, which can non-selectively

oxidize organic pollutants (Espinoza-Montero et al., 2022). The application of an external potential in PEC systems

provides a signiﬁcant advantage over conventional photocatalysis, as it increases the lifetime and reactivity of charge

carriers, thus improving overall oxidation efﬁciency.

The degradation efﬁciency of organic pollutants is strongly inﬂuenced by the type of photocatalyst used as

photoanode (Alulema-Pullupaxi et al., 2021). According to Espinoza-Montero et al., (2022), the selection of photoanode

materials determines the properties of the photoelectrode and the overall degradation performance. In the case of

boron-doped diamond substrates (BDD), the introduction of boron atoms creates electron deﬁciencies (positive holes)

in the crystal lattice. In the band structure, the Fermi level is closer to the valence band (VB), and when electrons are

stimulated by light (or the application of potential), they move from the VB to the conducting band (CB).

In this case, there are more holes in the VB than electrons in the CB, so the BDD exhibits p-type semiconductor

behavior (Rycewicz et al., 2022; Sultana et al., 2025). In contrast, the presence of oxygen vacancies in

TiO

introduces

a pair of electrons into the lattice. When light is applied, these electrons are excited from VB to CB (Asadollahi

et al., 2020; Kayani et al., 2023; Zhu et al., 2022). Under these conditions,

TiO

has a greater number of free electrons

than holes and exhibits n-type semiconductor behaviour. The p–n heterojunction formed between BDD and

TiO

facilitates efﬁcient charges separation and transport, improving the photoelectrocatalytic performance.

On the other hand, BDD/

TiO

photoanodes combine efﬁciency and environmental safety. BDD is chemically inert,

electrochemically stable, and does not evict harmful species, while

TiO

is biocompatible and widely recognized

as a non-toxic photocatalyst (Terashima et al., 2016). In addition, BDD/

TiO

is a p-n heterojunction which offers

clear functional advantages: (i) efﬁcient charge carriers separation, (ii) higher electrical conductivity that reduces the

loss of recombination, (iii) synergy between electrooxidation in BDD and photocatalysis in

TiO

, and (iv) long-term

mechanical and chemical stability.

Several strategies have been explored to mitigate the environmental impact of cancer drugs, particularly through

their degradation using light driven technologies such as photocatalysis and PEC. Mazierski et al., (2023) used a

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Revista de la Facultad de Ciencias Básicas

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Photoelectrochemical degradation of imatinib mesylate using a BDD/TiO

photoanode: A short communication.

CdS/

TiO

photoanode to degrade ifosfamide, 5-ﬂuorouracil, and imatinib mesylate in three-hour reactions, achieving

a TOC elimination of 48

2.4 %, 40

2.2 %, and 24

1.8 %, respectively. Although effective, CdS poses a critical

drawback: cadmium is a highly toxic heavy metal, and despite controls to detect leaching, its potential release and

the photocorrosion of CdS signiﬁcantly limit long-term applicability (Wei et al., 2021). Similarly, Naraginti et al.,

(2019) reported 90 % degradation of azithromycin using a

ZrO

/Ag@

TiO

photoanode under visible light. However,

the incorporation of silver also raises concerns about cost and ecotoxicity due to potential metal release.

BDD/

TiO

composites are among the most robust and widely studied photoelectrodes for this purpose and have

shown excellent performance in reducing complex and persistent organic compounds in water environments,

including glyphosate (Alulema-Pullupaxi et al., 2021), diclofenac (Sigcha-Pallo et al., 2022), and microplastics

(Quilumbaquin, Castillo-Cabrera, Borrero-González, Mora et al., 2024). This photoanode exhibits high long-term

stability, efﬁcient photoelectrochemical activity, and environmental safety, since

TiO

is non-toxic and biocompatible

(Jerczynski et al., 2022).

In this study, we utilized the BDD/

TiO

photoanode to evaluate its efﬁciency in the degradation of IMB by PEC.

Additionally, we explored the optimal operating conditions for this system, providing a foundation for further

research aimed at improving both the photoanode material and operational parameters.

2. Materials and Methods

Reagents

All reagents were used without further puriﬁcation. Sodium sulfate (Sigma Aldrich, CAS 7757-82-6, reagent grade),

sulfuric acid (Sigma Aldrich, CAS 7664-93-9, 98 %), potassium ferricyanide (Sigma Aldrich, CAS 13746-66-2, 98 %),

imatinib mesylate (Anhui Haikang Pharmaceutical, CAS 220127-57-1), potassium ferrocyanide (Sigma Aldrich,

CAS 14459-95-1, 98 %), BDD/Nb (Metakem™, Germany; geometric area = 8.5 cm

), Degussa P25 titanium dioxide

nanopowder (Sigma Aldrich, CAS 13463-67-7), perchloric acid (Sigma Aldrich, 98 %), and COD LR reagent vials

(Hanna Instruments) were used in this study.

Equipment

For electrochemical and photoelectrochemical measurements, a CH Instruments 1230 electrochemical workstation

was used. PEC experiments were conducted using a UV LED lamp (Cole-Parmer, T8 20 W, 110 V, 245 nm) as the light

source and an AC/DC power supply (BK Precision, 1760A) for degradation. IMB degradation was monitored using

the HACH COD test (HACH 8000, Usepa HAC-H-2000) and a UV–Vis spectrometer (Agilent Technologies, Cary 60).

Methods

Prior to modiﬁcation, the boron-doped diamond (BDD) electrode was electrochemically activated and subsequently

coated with

TiO

via electrophoretic deposition, following the procedure previously described by our group

(Quilumbaquin, Castillo-Cabrera, Borrero-González & Espinoza-Montero, 2024). Brieﬂy, a 2.5 % (w/v)

TiO

suspension was prepared in a 2.5 % (v/v) isopropyl alcohol–water solvent mixture, with a total volume of 25

mL.

An electrochemical cell was then assembled, consisting of the BDD electrode as the working electrode and an

aluminum plate as the counter electrode. Both electrodes were immersed in the

TiO

suspension for 15 s under an

applied potential of 4.8 V. Following deposition, the modiﬁed electrode was dried on a hot plate at 100

◦

C for 5 min

and subsequently subjected to thermal treatment in an oven at 200

◦

C for 20 min to ensure proper adhesion and

crystallization of the TiO

layer.

a) Characterization

For electrochemical and photoelectrochemical characterizations, a three-electrode system was employed, consisting of

either bare BDD or BDD/

TiO

as the working electrode, a platinum mesh as the counter electrode, and an Ag/AgCl

reference electrode, all enclosed within a Faraday cage to minimize electronic noise. To evaluate the enhancement in

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active surface area and photoactivity upon

TiO

modiﬁcation, CV experiments were performed using a 2 mmol L

−1

ferricyanide redox couple in 1 mol L

−1

KCl under both UV-illuminated and dark conditions.

In order to determine the working potential window of the electrodes and select the appropriate potentials for

transient photocurrent experiments, CV was performed in 0.1 mol L

−1

sodium sulfate solution. Light-chopped

photocurrent experiments (transient photocurrent) were then conducted at the previously determined potentials

according to the CV proﬁles, using only the electrolyte solution to assess the photocurrent generated by the

photocatalyst layer. The experiments were carried out in a transient mode, consisting of 5 minutes of dark

pre-conditioning for stabilization, followed by 2 minutes of light activation, 10 seconds of photocurrent recording,

and 4 minutes for the system to return to the ground state, with a total of 10 cycles of measurement.

b) Degradation of IMB

The degradation of imatinib mesylate (IMB) was monitored using UV–Vis spectroscopy at 257 nm (Bende et al.,

2008) with an integration time of 12.5 ms. A calibration curve was constructed using IMB standard solutions at

concentrations of 1, 5, 10, 20, 30, 40, and 50

mol L

−1

prepared in 0.1 mol L

−1

sodium sulfate, which served as the

supporting electrolyte.

Both electrocatalytic (EC) and photoelectrocatalytic (PEC) degradation processes were evaluated. Experiments were

conducted using 35 mL of a 24 mg L

−1

IMB solution in 0.1 mol L

−1

under continuous magnetic stirring, for

reaction times of 10, 20, 30, 60, and 90 min. UV irradiation (4 mW cm

−2

) was supplied by two LED emitters, and the

applied current density was varied between 4.13, 8.26, and 11.35 mA cm

−2

. To prevent temperature ﬂuctuations from

affecting hydroxyl radical (

•

) generation, two cooling gels were positioned on either side of the electrochemical

cell.

A platinum mesh was used as the counter electrode, while an Ag/AgCl electrode served as the reference to maintain

control of the anodic potential during degradation. Electrooxidation (EO) experiments were carried out under

identical conditions but without UV illumination, employing either a bare BDD anode or a

TiO

-modiﬁed BDD

(BDD/TiO

) anode for comparative evaluation.

The degradation process was monitored by UV–Vis spectroscopy at a ﬁxed wavelength of 257 nm. After each

degradation experiment, performed at the speciﬁed time intervals, aliquots of the treated solution were collected and

preserved with concentrated sulfuric acid for subsequent chemical oxygen demand (COD) analysis using the HACH

8000 test system. All experiments were conducted in triplicate to ensure statistical reliability.

The speciﬁc energy consumption (EC) of the PEC process was calculated according to the following equation

(Castillo-Cabrera et al., 2023):

E.C (kWh m

−3

) =

cell

· I · t

(1)

Where

cell

is the applied cell potential (V),

is the current passing through the cell (A),

is the reaction time (h), and

is the solution volume (m

The operating cost of the process was calculated (Castillo-Cabrera et al., 2023):

Cost of process = E.C (kWh m

−3

) · Unit electricity price (USD kWh

−1

) (2)

3. Results and Discussion

Figure 1a presents the cyclic voltammetry (CV) proﬁles obtained for the ferri/ferrocyanide redox couple. The

BDD/TiO

electrode exhibits higher anodic and cathodic peak current densities than the bare BDD electrode,

indicating an enhancement of the electroactive surface area due to the deposition of the TiO

photocatalyst layer.

Figure 1b shows the voltammetric response recorded in 0.1 mol L

−1

, revealing distinct differences in oxidation

and reduction overpotentials between the two electrodes. These variations suggest improved electrocatalytic

performance of the BDD/TiO

photoelectrode. The observed increase in capacitive current within the potential range

−

0.5 to

−

1.25 V is characteristic of the charging and discharging processes associated with electrodes modiﬁed by

semiconductor materials.

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Photoelectrochemical degradation of imatinib mesylate using a BDD/TiO

photoanode: A short communication.

Upon UV illumination, the BDD/TiO

electrode displays a clear decrease in oxidation overpotential (Figure 1c),

conﬁrming the photoactivation of the TiO

layer and its contribution to the overall photocatalytic behavior of the

composite electrode.

Figure 1d illustrates the transient photocurrent responses recorded at applied potentials of 1.50, 1.55, and 1.60 V vs.

Ag/AgCl. At 1.50 V, the photocurrent increases from a baseline of 0.003 to 0.006

A cm

−2

; at 1.55 V, from 0.007 to

0.012

A cm

−2

; and at 1.60 V, from 0.016 to 0.027

A cm

−2

. The highest photocurrent response was observed at 1.60

V, corresponding to a net increase of 0.011

A cm

−2

. These results indicate that higher applied potentials promote

more efﬁcient charge separation and enhanced photoelectrocatalytic activity of the BDD/TiO

electrode.

Figure 1. Electrochemical and photoelectrochemical characterization of BDD and BDD/TiO

electrodes. a) CV proﬁles of BDD

and BDD/TiO

in 2.0 mmol L

−1

[Fe(CN)

]

3−/4−

redox couple in 1.0 mol L

−1

KCl. b) CV proﬁles of BDD and BDD/TiO

0.1 mol L

−1

. c) CV proﬁles of BDD/TiO

in 0.1 mol L

−1

under dark and UV illumination conditions. d) Transient

photocurrent response of BDD/TiO

in 0.1 mol L

−1

under chopped UV light.

Photoelectrocatalytic Degradation of IMB

Three distinct current densities, 4.13, 8.26, and 11.35 mA cm

−2

, were evaluated for the electrochemical and

photoelectrochemical oxidation of IMB. These values were selected based on

•

OH-radical scavenging experiments

conducted by (Quilumbaquin, Castillo-Cabrera, Borrero-González, Mora et al., 2024), which identiﬁed the optimal

range for generating oxidant species under the speciﬁc photoanode material and cell conditions.

Figure 2a presents the degradation percentages of IMB over 90 min PEC reactions at different current densities. The

results indicate that the degradation efﬁciencies at 8.26 and 11.35 mA cm

−2

are statistically equivalent, achieving

84.09 % and 82.95 % respectively. In contrast, a lower efﬁciency of 62.14 % was observed at 4.13 mA cm

−2

. These

ﬁndings highlight that a current density of 8.26 mA cm

−2

provides the highest degradation efﬁciency while

minimizing energy consumption compared to the higher current density.

Similar trends were observed in the electrochemical oxidation of IMB using the bare BDD and the BDD/TiO

(Figure

1), conﬁrming that the PEC process with the BDD/TiO

photoanode offers superior performance for IMB degradation

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under the conditions evaluated in this study.

Figure 1b presents the pseudo-ﬁrst-order kinetic analysis for the PEC degradation of IMB at the tested current

densities. The highest apparent rate constant was observed at 11.35 mA cm

−2

, with a value of 0.0295 min

−1

. However,

the corresponding coefﬁcient of determination (R

) was relatively low, indicating poor linearity and limited statistical

conﬁdence in the ﬁt—suggesting that side reactions or mass transport limitations may be inﬂuencing the degradation

behavior at this higher current density. At 8.26 mA cm

−2

, the apparent kinetic constant slightly decreased to 0.024

min

−1

, yet the R

value improved signiﬁcantly, indicating a better ﬁt to the pseudo-ﬁrst-order model and greater

statistical reliability. This suggests a more controlled and efﬁcient degradation process under these conditions. In

contrast, the lowest current density (4.13 mA cm

−2

) yielded the lowest rate constant, reﬂecting a slower degradation

rate caused by limited generation of oxidant species or inefﬁcient separation of charge carriers. A similar kinetic

trend was observed in electrochemical oxidation experiments using both BDD and BDD/TiO

electrodes without

photoactivation (Figure 1), reinforcing the observation that intermediate current density not only offers improved

energy efﬁciency but also more predictable and reliable kinetic behavior in IMB degradation.

When comparing the degradation processes (PEC and EO) at a current density of 8.26 mA cm

−2

, we ﬁnd that

the PEC process has a higher apparent kinetic constant, mainly due to the synergistic effect of the BDD/TiO

heterojunction and UV irradiation. As shown in Figure 3, the CB and VB positions of TiO

differ signiﬁcantly from

those of BD, favoring charge separation. By using a bias potential, holes from the BDD are injected into the VB of

the TiO

, while electrons from the TiO

are injected into the CB of the BDD, allowing for easy separation of charge

carriers between the two materials. The band alignment at the BDD/TiO

interface facilitates charge transfer and

suppresses recombination. The photogenerated h

in the VB, together with pre-existing oxygen vacancies in TiO

contribute to the generation of

•

OH, which play a key role in the enhanced degradation and mineralization of IMB.

(Alulema-Pullupaxi et al., 2021; Castillo-Cabrera et al., 2023; Terashima et al., 2016; Xie et al., 2022).

a) b)

Figure 2. a) IMB degradation efﬁciency during 90 min of PEC reactions at different current densities (4.13, 8.26, and 11.35 mA

−2

) in 0.1 mol L

−1

. b) Pseudo-ﬁrst-order kinetic analysis of the degradation process, showing the inﬂuence of current

density on the apparent rate constant and the linear ﬁt to the kinetic model. Data are presented as mean

standard deviation, as

detailed in Table 1.

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Photoelectrochemical degradation of imatinib mesylate using a BDD/TiO

photoanode: A short communication.

Figure 3. Electronic band positions of TiO

and BDD with respect to vacuum level and standard hydrogen electrode. Adapted

from Terashima et al., (2016).

The chemical oxygen demand (COD) was measured to evaluate the mineralization efﬁciency of each process. Figure

4 presents the percentage of COD removal over time for the PEC system. After 90 min of reaction, the BDD/TiO

photoanode achieved a COD concentration of 12.16 mg L

−1

, representing the lowest residual value among the

tested systems. This result indicates a higher degree of IMB degradation compared to both EO using the same

BDD/TiO

photoanode and the bare BDD electrode. The enhanced mineralization observed in the PEC system can be

attributed to the synergistic effects of photogenerated electron-hole pairs due to the surface activity of the BDD/TiO

photoanode.

Figure 4. COD analysis for the degradation of IMB using PEC and EO with the bare BDD and BDD/TiO

anodes. (see Table 1).

For comparison, Table 1 presents the concentration of COD removal and the corresponding mineralization achieved

by the oxidation processes evaluated. The PEC process exhibited a mineralization rate 14.57 % higher than obtained

through EO using the BDD/TiO

photoanode. Similarly, the PEC system outperformed the EO process using the bare

BDD anode, achieving a 15.66% greater mineralization efﬁciency. These results demonstrate that the PEC process

is the most effective technology for the degradation of IMB, highlighting its superior capability to promote almost

complete oxidation of the pollutant compared to traditional electrochemical oxidation.

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Table 1. COD values and mineralization rates for IMB degradation after 90-min of reaction using PEC and EO processes.

Process Electrode COD (mg L

−1

) Mineralization ( %)

PEC BDD/TiO

12.16 68.70

EO BDD/TiO

13.6 54.13

EO BDD 17 53.04

It is essential to develop cost-effective and energy-efﬁcient strategies for the degradation of anticancer drugs to ensure

their long-term environmental applicability. In Ecuador, the electricity cost is reported to be USD 0.095 per kWh as

of December 2024 (Global Petrol Prices, 2024). Based on this rate, the operational cost of the proposed process is

estimated at USD 0.91 per m

of treated solution. These ﬁndings demonstrate that the PEC process can achieve high

degradation efﬁciency for complex oncological compounds while maintaining relatively low energy requirements.

In a related study, Sigcha-Pallo et al., (2022) reported the degradation of diclofenac sodium via PEC using a BDD/TiO

photoanode fabricated by electrophoretic deposition, achieving 98.5 % mineralization within two hours. The authors

concluded that PEC systems exhibit lower energy consumption than electrooxidation (EO) processes, primarily due

to the enhanced charge separation enabled by the p–n heterojunction. A similar trend was observed in the present

work: during IMB degradation, the BDD/TiO

photoanode demonstrated reduced energy consumption under PEC

conditions compared with EO operation.

Alulema-Pullupaxi et al., (2021) also employed PEC technology to degrade glyphosate using a TiO

/BDD photoanode

prepared via a sol–gel/spin-coating method with titanium oxysulfate as the precursor. Their process achieved 91.1 %

glyphosate degradation with an energy consumption of 0.62 kWh gTOC

−1

over ﬁve hours, treating 400 mL of

a 50 mg L

−1

solution. In contrast, the present study achieved substantial degradation of the more complex IMB

molecule in only 90 minutes, suggesting a lower energy demand per unit time. Nonetheless, the difference in solution

volume–11.5 times smaller in this work–may partly explain the faster degradation kinetics observed.

For comparison, (Yang et al., 2019) reported complete mineralization of IMB via the electro-Fenton process using

a graphene-modiﬁed carbon felt cathode (EEGr–CF), with an energy consumption (EC) of 14.4 kWh g

−1

. In

contrast, a conventional carbon felt cathode required 16.6 kWh g

−1

under similar conditions. Although effective,

the electro-Fenton process demanded higher current densities (16.66 mA cm

−2

), longer reaction times (8 h), and

larger solution volumes (150 mL). By comparison, the PEC process developed in this study achieved comparable

mineralization efﬁciency at a lower current density (8.26 mA cm

−2

) and signiﬁcantly shorter reaction time (90 min),

underscoring its superior energy efﬁciency.

Overall, when compared to other advanced oxidation processes, the proposed PEC system exhibits competitive

advantages in terms of degradation efﬁciency, energy economy, and operational simplicity, positioning it as a

promising technology for the sustainable treatment of pharmaceutical contaminants.

4. Conclusion

The BDD/TiO

photoanode demonstrated the highest efﬁciency among the tested oxidation systems, achieving

84.10 % degradation and 68.70 % mineralization of imatinib within 90 min under UV-assisted PEC conditions at an

optimal current density of 8.26 mA cm

−2

The TiO

coating effectively enhanced the surface properties of the BDD electrode, exhibiting sustained catalytic

activity and mechanical integrity over prolonged operation (up to 7 h) without evidence of delamination or material

degradation, conﬁrming its durability for extended PEC applications.

Consistent with prior studies, the BDD/TiO

PEC system exhibited lower speciﬁc energy consumption compared to

conventional electrooxidation, attributed to improved charge separation within the p–n heterojunction. However,

optimization of light utilization and reactor conﬁguration remains essential to further reduce energy costs and enable

practical implementation in large-scale wastewater treatment.

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Photoelectrochemical degradation of imatinib mesylate using a BDD/TiO

photoanode: A short communication.

5. Acknowledgments

The authors thank Pontiﬁcia Universidad Católica del Ecuador for funding through project Preparation of

boron-doped diamond (BDD) photoelectrodes modiﬁed with bismuth semiconductors and their application in

photoelectrocatalysis, code: QINV0402-IINV529020100, and Universidad Técnica de Manabí for ﬁnancial support.

6. Conﬂict of Interest

The authors report no conﬂicts of interest related to this research.

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8. Contributions from authors

Author Contribution

Steven Mateo Vélez Zambrano

Data curation, Formal analysis, Investigation, Methodology, Writing- original

draft, Writing - review & editing.

G. Xavier Castillo-Cabrera

Data curation, Formal analysis, Investigation, Methodology, Writing - review

& editing.

Gustavo Altamirano-Briones

Conceptualization, Funding acquisition, Investigation, Methodology, Resour-

ces, Supervision, Validation, Visualization, Writing - original draft, Writing -

review & editing.

Patricio Javier Espinoza-Montero

Conceptualization, Data curation, Funding acquisition, Investigation,

Methodology, Project administration, Resources, Supervision, Validation,

Visualization, Writing - original draft, Writing - review & editing.

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9. Supplementary material

Electrochemical Degradation

a) b)

c) d)

Figure S1. a) Degradation efﬁciency of IMB during 90-min EO process using a

BDD/TiO

photoanode at different current densities

in 0.1

mol L

−1

. Data are presented as

mean ± standard deviation

, as detailed in Table S1. b) Pseudo-ﬁrst-order reaction

kinetic analysis of IMB degradation in EO using

BDD/TiO

. c) Degradation efﬁciency of IMB during 90-min EO process using

bare BDD photoanode at different current densities in 0.1

mol L

−1

. Data are presented as

mean ± standard deviation

, as

detailed in Table S1. d) Pseudo-ﬁrst-order reaction kinetic analysis of IMB degradation in EO using bare BDD.

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Photoelectrochemical degradation of imatinib mesylate using a BDD/TiO

photoanode: A short communication.

Table S1. Mean standard deviation of the percentage of IMB degraded by the photoelectrocatalytic process (PEC) and its kinetic

analysis during 90-minute reactions at different current densities applied in 0.1 mol L

−1

, corresponding to Figure 3.

Degradation Kinetic analysis

Time (min)

4.13 mA

−2

8.26 mA

−2

11.35 mA

−2

4.13 mA

−2

8.26 mA

−2

11.35 mA

−2

10 0.91 4.18 1.41 0.00 0.00 0.00

20 4.46 8.41 6.03 0.05 0.07 0.09

30 2.94 7.46 7.70 0.04 0.07 0.12

60 1.95 6.36 8.14 0.04 0.08 0.16

90 11.94 7.13 8.19 0.23 0.21 0.32

Mean standard deviation

4.44 6.71 6.29 0.07 0.09 0.14

Table S2. Mean standard deviation of the percentage of IMB degraded by the photoanode electrooxidation process (EO-BDD/TiO

)

and its kinetic analysis during 90-minute reactions at different current densities applied in 0.1

mol L

−1

, corresponding to

Figure S1.

Degradation Kinetic analysis

Time (min)

4.13 mA

−2

8.26 mA

−2

11.35 mA

−2

4.13 mA

−2

8.26 mA

−2

11.35 mA

−2

10 0.79 10.62 1.64 0.00 0.00 0.00

20 1.44 12.53 3.15 0.02 0.03 0.02

30 2.41 8.29 3.01 0.02 0.01 0.03

60 3.67 6.95 3.27 0.05 0.01 0.04

90 5.31 4.37 2.89 0.12 0.10 0.10

Mean standard deviation

2.72 8.55 2.79 0.04 0.03 0.04

Table S3. Mean standard deviation of the percentage of IMB degraded by the electrooxidation process (EO-BDD) and its kinetic

analysis during 90-minute reactions at different current densities applied in 0.1 mol L

−1

, corresponding to Figure S1.

Degradation Kinetic analysis

Time (min)

4.13 mA

−2

8.26 mA

−2

11.35 mA

−2

4.13 mA

−2

8.26 mA

−2

11.35 mA

−2

10 0.00 0.00 0.00 1.99 5.98 3.75

20 0.05 0.02 0.06 3.76 3.87 2.28

30 0.03 0.02 0.11 1.52 4.45 4.66

60 0.01 0.04 0.21 0.79 5.42 8.28

90 0.04 0.14 0.29 2.74 4.81 4.66

Mean standard deviation

0.03 0.04 0.13 2.16 4.91 4.73

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Table S4. Mean standard deviation of the values obtained by chemical oxygen demand for the three degradation processes during

90 minutes, at a current density of 8.26 mA cm

−2

, corresponding to Figure 4.

PEC EO-BDD-TiO

EO-BDD

Time (min) 8.26 mA cm

−2

8.26 mA cm

−2

8.26 mA cm

−2

10 0.65613 0.56569 4.17193

20 1.98756 1.59099 2.72236

30 2.52937 1.69706 4.34871

60 0.44252 1.06066 5.16188

90 0.71 1.27279 3.81838

Mean standard deviation

1.27 1.24 4.04

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