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The influence of pH and current density on an UV254 photo-assisted electrochemical process generating active chlorine and radicals for efficient and rapid ciprofloxacin mineralization compared to individual techniques

August 2020
Journal of Environmental Chemical Engineering 8(5):104357

August 2020
8(5):104357

DOI:10.1016/j.jece.2020.104357

Authors:

Rosa Maria Luna Sanchez

Metropolitan Autonomous University

Ricardo Palma

Universidad del Valle (Colombia)

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A photo-assisted electrochemical process is herein evaluated with the aim of improving and accelerating the degradation and mineralization of Ciprofloxacin (CIP) in aqueous media, in comparison with single electrochemical or photochemical methods. Active chlorine species are initially electro-generated on a synthesized (Pechini method) Ti/TiO2-RuO2 DSA, and subsequently fragmented homolitically using UVC irradiation under very low fluency rate (3300 µW cm⁻², λ = 254 nm) to produce radicals with higher oxidation potentials compared to the original active chlorine. A faster CIP degradation (5 min) and higher mineralization is obtained in the coupled system against the individual techniques. Variations of pH and current density in the UV-assisted electrochemical process reveal that a similar degradation rate is obtained during 60 min for pH 6 and 9 due to the co-existence of HOCl and OCl- species in this range of pH, leading to the possible production of highly reactive radicals (e.g.HOaq•, Claq•, Oaq-•) after chlorine species fragmentation. The highest total organic Carbon (TOC) removal was obtained at pH = 6 (70% in 60 min), where the highest HOCl concentration is observed, thus, enhancing the HOaq• production. The contaminant degradation and mineralization strongly depend on the radicals formed from the irradiation of chlorine species, which on its turn rely on the redox couples formed as a function of pH: 3 (HOCl + Cl2), 6 and 9 (HOCl + OCl-). Mechanisms are proposed for these homolysis reactions, while the degradation pathway of CIP is rationalized using HPLC analyses during 60 min of electrolysis.

Effect of initial pH on the 60 µmol L −1 CIP +0.05 mol L -1 NaCl UV-assisted electrochemical treatment at three different pH values (3, 6 and 9), applying a current density of a) 5 and b) 10 mAcm -2 .

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Byproduct (CIP-I-1, CIP-I-2 and CIP-I-3) concentrations as a function of pH, current density and time during UV-assisted electrochemical treatment for CIP.

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Degradation pathway proposed for CIP by UV-assisted electrochemical treatment.

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Specific energy consumptions and percentage of TOC removed as a function of pH and current density in chloride media.

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1. Introduction

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I@E< GIF;L:K@FE ?8J EFK 9<<E <M8CL8K<; 9P LJ@E> 8 :FEKIFCC<; JPEK?<J@J

F= 8 .@.@),L)8EF;< J@E:< :FDD<I:@8C 8EF;<J ?8M< 8CN8PJ 9<<E

<DGCFP<; .?< GI<J<E:< F= 8 :FEKIFCC<; :FDGFJ@K@FE I<:<EKCP ;<GFJ@K<;

:FLC; J@>E@=@:8EKCP @DG8:K K?< <=`:@<E:P 8E; <EP :FEJLDGK@FE F= K?<

G?FKF:?<D@:8C GIF:<JJ LJ@E> C8DGJ N@K? 8 :FEJ@;<I89CP CFN<I aL<E:P

I8K< @E FI;<I KF @DGIFM< K?< @EK<I8:K@FE 9<KN<<E K?< <C<:KIF:8K8CPK@:

8E; I8;@8K@FE GIF:<JJ =FI J:8C<LG 8GGC@:8K@FEJ

/E;<I K?@J @;<8 K?< =F:LJ F= K?@J JKL;P @J KF <M8CL8K< K?< @EaL

<E:< F= G" 8E; :LII<EK ;<EJ@KP @E 8 G?FKF8JJ@JK<; <C<:KIF:?<D@:8C

GIF:<JJ LJ@E> 8 JPEK?<J@Q<; .@.@),L)-  :D N?FJ< :8K8CP

J@J KFN8I;J K?< GIF;L:K@FE F= 8:K@M< :?CFI@E< ?8J 9<<E GI<M@FLJCP FG

K@D@Q<; LJ@E> K?< *<:?@E@ JPEK?<J@J D<K?F; 56 .?< - @J :?8I8:

K<I@Q<; LJ@E> 2I8P @==I8:K@FE 2, -:8EE@E> C<:KIFE@: '@:IFJ:FGP

-' 8E; EP;@JG<IJ@M< 2I8P JG<:KIFJ:FGP -  I<8:K@FE K8EB

 D& :FEK8@E@E> 8 "> /0 C8DG  ^1 :D−λ  ED @J

LK@C@Q<; KF ;<>I8;<  GGD #* @E  DFC & (8C ;LI@E>  ? .?<I<

=FI< @K N@CC 8CCFN 8::FLEK@E> =FI K?< <==<:K F= <C<:KIF:8K8CPK@: 8:K@M@KP

FE K?< >CF98C GIF:<JJ F= ;<JKIL:K@FE 8E; D@E<I8C@Q8K@FE F= G?8ID8:<L

K@:8C :FDGFLE;J @E I<C8K@M<CP J?FIK K@D<J /0G?FKF:?<D@:8C <C<:KIF

:?<D@:8C 8E; /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ<J 8I< :FE;L:K<; =FI

:FDG8I8K@M< GLIGFJ<J .?< @EaL<E:< F= KNF :LII<EK ;<EJ@K@<J  8E;

 D :D− 8E; K?I<< @E@K@8C G" M8CL<J   8E;  8I< <M8CL8K<; KF

N8I;J K?< #* ;<>I8;8K@FE N?@:? @J DFE@KFI<; 9P LJ@E> "@>? *<I=FI

D8E:< &@HL@; ?IFD8KF>I8G?P "*& N?@C< K?< D@E<I8C@Q8K@FE

GIF:<JJ @J <M8CL8K<; 9P .FK8C )I>8E@: 8I9FE .)

2. Materials and methods

 !,(.,4:9

.?< =FCCFN@E> 8E8CPK@:8C I<8><EKJ N<I< GLI:?8J<; =IFD '<I:B 8E;

LJ<; 8J I<:<@M<; JF;@LD :?CFI@;< (8C 8:<KFE@KI@C< "( JF;@LD

JLC=8K< (8-) GFK8JJ@LD @F;@;< %# JF;@LD ?P;IFO@;< (8)"

DDFE@LD ?<GK8DFCP9;8K< ("'F)_") 8E; @GIFaFO8:@E

#*

 "?4:/,909 5- (45+, 3(:,80(29

-J `CDJ N<I< @DGI<>E8K<; FE K@K8E@LD GC8K<J LJ@E> K?< *<:?@E@

D<K?F; 8::FI;@E> KF *8CD8!FP<J <K 8C 5–6 E8CPK@: >I8;<

I<8><EK F= ,LCN8J LK@C@Q<; 8J D<K8CC@: GI<:LIJFI @E 8 GFCPD<I@: D@O

KLI< GI<G8I<; N@K? 8 D<K8C DFC8I :FE:<EKI8K@FE F=  DFC &−N@K?

 DFC &−:@KI@: 8:@; 8J :?<C8K@E> 8><EK 8E;  DFC &−<K?PC<E< >CP

:FC 8J I<8:K@FE JFCM<EK .?< GFCPD<I@: D@OKLI< N8J B<GK JK@II<; 8K  Z

=FI  D@E 8E; JL9J<HL<EKCP ;<GFJ@K<; FE .@ GC8K<J  f  :D N?@:?

N<I< GI<M@FLJCP KI<8K<; @E FO8C@: 8:@; 8K  Z =FI  D@E .?<J< GC8K<J

N<I< ;I@<; 8K  Z =FI `M< D@ELK<J 8E; :8C:@E<; 8K  Z =FI  ?

FK? K<DG<I8KLI<J N<I< J<C<:K<; =IFD K?<IDF>I8M@D<KI@: 8E8CPJ@J .!

;8K8 F= K?< I8N GFCPD<I@: D@OKLI< -LGGFIK@E> @E=FID8K@FE  .?< :F8K

@E> GIF:<;LI< N8J I<G<8K<; <@>?K K@D<J KF K?@:B<E K?< :F8K@E>

 0*859:8;*:;8(2 */(8(*:,80@(:054 5- (45+,9

-' @D8><J N<I< :FCC<:K<; KF ;<K<ID@E< K?< DFIG?FCF>P F= ;<

GFJ@K<; FO@;< `CDJ LJ@E> 8 ?@>?`<C; <D@JJ@FE D@:IFJ:FG< 4<@JJ -/*,

0* N@K? 8::<C<I8K@E> MFCK8>< F=  B0 ?<D@:8C :FDGFJ@K@FE N8J

J@DLCK8E<FLJCP <M8CL8K<; LJ@E> <EP ;@JG<IJ@M< 2I8P JG<:KIFJ:FGP

- :8G89@C@K@<J =FI <C<D<EK8C 8E8CPJ@J 2, ;8K8 N<I< :FCC<:K<; N@K?

8 ILB<I  ;M8E:< N@K? L%αI8;@8K@FE ;@==I8:KFD<K<I @E 8

I8>>I<EK8EF θθ :FE`>LI8K@FE FG<I8K<; N@K? 8 L %α%α I8;@8

K@FE λ S 8K  B0 8E;  D =IFD  KF Z θ .?< :IPJ

K8CC@E< G?8J<J N<I< @;<EK@`<; LJ@E> K?< $*-# :8I;J

 #$6/5:5*/,30*(2 ,2,*:85*/,30*(2 (4+ #$(9909:,+ ,2,*:85*/,30*(2

*/(8(*:,80@(:0549

<>I8;8K@FE K<JKJ N<I< G<I=FID<; LJ@E> 8 /08JJ@JK<; <C<:KIF:?<D@

:8C I<8:KFI -LGGFIK@E> @E=FID8K@FE  /0G?FKF:?<D@:8C <C<:KIF:?<D

@:8C 8E; /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ<J N<I< :8II@<; FLK @E 8

 D& J@E>C< :FDG8IKD<EK 8@IK@>?K >C8JJ :<CC N@K? 8  :D;@8D<K<I

HL8IKQ KL9< GC8:<; @E K?< :<EK .?<

K<DG<I8KLI< F= K?< I<8:KFI N8J :FEKIFCC<; K?IFL>? 8 :FFC@E> A8:B<K 8K

 Z 8E; ;@JGC8P<; 9P 8 K?<IDF:FLGC< @DD<IJ<; @EKF K?< JFCLK@FE #E

8CC :8J<J K?< JK@II@E> JG<<; N8J B<GK :FEJK8EK  IGD LJ@E> 8 D8>

E<K@: JK@II /0

G<E,8P C8DG DF;<C -  D   ^1 :D−   :D

&@>?K<; &<E>K?@8D<K<I λ  ED N8J GC8:<; @E K?< I<8:KFI :<E

K<I -@E>C< /0G?FKF:?<D@:8C GIF:<JJ<J N<I< :8II@<; LJ@E> K?@J JPJK<D

@E K?< 89J<E:< F= <C<:KI@: :LII<EK @E K?< I<8:KFI /0G?FKF:?<D@:8C

-@E>C< <C<:KIF:?<D@:8C <OG<I@D<EKJ <C<:KIF:?<D@:8C 8E; /08JJ@JK<;

<C<:KIF:?<D@:8C N<I< G<I=FID<; =FI :FDG8I8K@M< GLIGFJ<J LJ@E> K?<

JPEK?<J@Q<; .@.@)–,L) :D ><FD<KI@: 8I<8 G?8J< 8J 8EF;<

N?@C< 8 JK8@EC<JJJK<<C GC8K<  :D ><FD<KI@: 8I<8 8E; >>C N<I<

LJ<; 8J :8K?F;< 8E; I<=<I<E:< <C<:KIF;<J I<JG<:K@M<CP #E FI;<I KF ;<

K<ID@E< K?< JPE<K@: <==<:KJ F= K?< :FLGC@E> M8I@8K@FEJ F= @E@K@8C G"

8E; :LII<EK ;<EJ@KP N<I< :FE;L:K<; =FI K?< /08JJ@JK<; <C<:KIF:?<D

@:8C GIF:<JJ J?FNE @E .89C<  FEKIFC KI@8CJ N<I< G<I=FID<; N@K?



UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

Table 1

OG<I@D<EK8C ;<J@>E LJ<; @E K?< #* ;<>I8;8K@FE FE .@.@)–,L)<C<:KIF;<J

OG<I@D<EK

#*μDFC

&−$

D:D −G"

(8C

DFC & −*FN<I

;<EJ@KP^1 :D −

     

     

     

     

     

     

8E; N@K?FLK #* @< FECP JLGGFIK@E> <C<:KIFCPK< .?< 8HL<FLJ <C<:

KIFCPK< N8J :FDGI@J<; F=  μDFC &−#*  D> &− 8E;  DFC &−

(8C .?@J #* :FE:<EKI8K@FE N8J :?FJ<E 98J<; FE 8E8CPK@:8C 8E; ;<

K<:K@FE C@D@KJ N?@C< K?< (8C :FE:<EKI8K@FE :8EEFK <O:<<; I<GI<J<EK8

K@M< C<M<CJ F= N8JK<N8K<J 9LK N@K?FLK :FDGIFD@J@E> 8E 8;

<HL8K< @FE@: :FE;L:K@M@KP @E K?< I<8:KFI 56 P:C@: MFCK8DD<KIP N8J

@E@K@8CCP LJ<; KF <M8CL8K< K?< <C<:KIF><E<I8K@FE F= FO@;@Q@E> 8><EKJ 8E;

KF @EM<JK@>8K< K?< <C<:KIF;< GFK<EK@8C F= <C<:KIF:?<D@:8C GIF:<JJ<J F:

:LII@E> FE K?< 8EF;< JLI=8:< .?<J< <OG<I@D<EKJ N<I< :8II@<; FLK @E

K?< I8E>< =IFD  KF  0 MJ >>C LJ@E> 8 J:8E I8K< F=  D0J−

@E 8 0'* @F&F>@: -:@<E:< #EJKILD<EK GFK<EK@FJK8K>8CM8EFJK8K :FE

KIFCC<; 9P &89 JF=KN8I<

.?< 8DFLEK F= FO@;8EKJ ><E<I8K<; ;LI@E> K?< KI<8KD<EK N8J ;<K<I

D@E<; 9P @F;FD<KIP 8J I<GFIK<; 9P *8CD8!FP<J <K 8C 56 LJ

@E> /0–M@J JG<:KIFJ:FGP 8J ;<K<:K@FE D<K?F; #E K?@J 8E8CPJ@J 8C@HLFKJ

F=  μ& F= J8DGC< N<I< GC8:<; @E 8 HL8IKQ :<CC :FEK8@E@E>  μ&

F=  DFC &−%# 8E;  μ& F=  DFC &−("'F)_")

N@K? JL9J<HL<EK JK@II@E> .?< 89JFI98E:< 8K  ED N8J D<8JLI<; 8=

K<I  D@E F= I<8:K@FE .?< @E@K@8C =FID8K@FE I8K< F= FO@;8EKJ μDFC

&−D@E− N8J <M8CL8K<; 9P C@E<8I@Q@E> K?< >I8G? F= FO@;8EK <MFCLK@FE

μDFC &− MJ <C<:KIFCPJ@J K@D< D@E .?@J I8K< @J 8E @E;@:8K@FE F= K?<

8DFLEK F= FO@;@Q@E> 8><EKJ =FID<; G<I LE@K F= K@D< FE K?< 8EF;< JLI

=8:< .?< JG<:@`: <EP :FEJLDGK@FE : B1 ? D N8J :8C:LC8K<; 8:

:FI;@E> KF *8CD8 <K 8C  56 8E; I<JLCKJ 8I< ;<J:I@9<; @E .89C< 

.?< <MFCLK@FE F= #* ;<>I8;8K@FE @< @EK<ID<;@8K< =FID8K@FE ;LI

@E> /0G?FKF:?<D@:8C <C<:KIF:?<D@:8C 8E; /08JJ@JK<; <C<:KIF:?<D@:8C

GIF:<JJ<J N8J DFE@KFI<; LJ@E> 8E "*& *<IB@ECD<I C<O8I <HL@GG<;

N@K? 8  3'  DD f  DD :FCLDE 8E; 8 /0 ;<K<:KFI

 ED .?< DF9@C< G?8J< N8J  MM D@OKLI< F= 8:<KFE@KI@C< 

=FID@: 8:@; G"  8K 8 aFN I8K< F=  D& D@E− .?< @EA<:K@FE MFCLD<

N8J  μ& .?< J8D< <HL@GD<EK LJ@E> 8E *I<M8@C  DD f  DD

:FCLDE 8K  Z 8J JK8K@FE8IP G?8J< 8E; 9Ld<I JFCLK@FE  DDFC &−

%"*)N?@:? N8J 8;ALJK<; KF G"  LJ@E> "*) 8J DF9@C< G?8J<

8E; 8 /0 ;<K<:KFI  ED N8J <DGCFP<; KF 8E8CPQ< J?FIK :?8@E

FI>8E@: 8:@;J GI<J<EK @E K?< <C<:KIFCPQ<; JFCLK@FE .?< 8GG8I<EK I8K<

:FEJK8EKJ F= ;<>I8;8K@FE F= #* D@E− N<I< >@M<E 9P K?< JCFG<

F= K?< :FII<JGFE;@E> JKI8@>?K C@E<J F= GCFK .?< KFK8C

FI>8E@: :8I9FE .) 8E8CPJ@J N8J :8II@<; FLK @E 8 .)

& J<I@<J -?@D8;QL <HL@GD<EK 9P ;@I<:K @EA<:K@FE F= K?< J8DGC< .?< J8D

GC<J N<I< `CK<I<; LJ@E> '@CC@GFI< D<D9I8E<J F=  μD

3. Results and discussion

 ":8;*:;8(2 (4+ :,>:;8(2 6856,8:0,9 5- "

-LGGFIK@E> @E=FID8K@FE  J?FNJ K?< 2I8P ;@==I8:K@FE JG<:KILD F= K?<

.@.@)–,L):8K8CPJK :FCC<:K<; LJ@E> 8 I8>>I<EK8EF ><FD<KIP )ECP

8 J@E>C< J<K F= 9IF8; 8E; JPDD<KI@: G<8BJ N8J =FLE; =IFD K?@J 8E8CPJ@J

8K θ   8E;  N?@:? N<I< 8KKI@9LK<; KF       8E;

   I<a<:K@FE GC8E<J I<JG<:K@M<CP .?<J< GC8E<J 8I< :?8I8:K<I@JK@: F=

K<KI8>FE8C :IPJK8CC@E< JKIL:KLI< 333 8J:I@9<; KF K?< GI<J<E:< F=

,L) .?<J< D<K8CC@: FO@;<J >I<N LG FE 8 C8P<I F= .@)ILK@C<

 GI<M@FLJCP =FID<; FE .@ JL9JKI8K<  ;L< KF K?< G8J

J@M8K@FE :FE;@K@FEJ F= K?@J M8CM< D<K8C -LGGFIK@E> @E=FID8K@FE  .?@J

F9J<IM8K@FE JL>><JKJ K?8K .@)C8PFE8C :IPJ

K8CC@E< JKIL:KLI< ,L)>IFNK? D8@ECP =8MFI<; =FI K?<@I J@D@C8I C8KK@:<

G8I8D<K<IJ #E 8;;@K@FE K?< @FE@: I8;@@ F= ,L .@ 8I<  f −

8E;  f  D I<JG<:K@M<CP 56 '8O@DLD ;@==<I<E:< <8:? FK?<I

@J   JD8CC<I K?8E K?< "LD<–,FK?<IP C@D@K =FI JL::<JJ=LC JL9JK@KL

K@FE @<   56 .?@J <OGC8@EJ N?P K?< 9@E8IP FO@;< D@OKLI< F=

.@)–,L):FLC; <O@JK 8J JFC@; JFCLK@FE

)E K?< FK?I8G?J N<I< <M8CL8K<; KF ;<K<ID@E<

K?< <C<:KIF;< K<OKLI< -LGGFIK@E> @E=FID8K@FE  GI<J<EKJ 8 KPG@:8C @D8><

F= K?< .@.@)–,L):8K8CPJK I<M<8C@E> 8 ?<K<IF><E<FLJ JKIL:KLI< :FD

GI@J<; F= C8I>< 8>>CFD<I8K<J F= K?@J FO@;< J@KK@E> FE KFG F= 8 DL;:I8:B

C8P<I D8;< F= K?< J8D< G?8J< FEJ<HL<EKCP K?@J JL9C8P<I @E:I<8J<J K?<

JLI=8:< 8I<8 F= K?< :8K8CPK@: D8K<I@8C 8E; @DGIFM<J K?< :?8I>< KI8EJ=<I F=

K?< <C<:KIF:?<D@:8C I<8:K@FE - D8GG@E> 8E8CPJ<J F= K?< 9@E8IP FO@;<

N<I< :8II@<; FLK @E 8  f  ^D 8I<8 -LGGFIK@E> @E=FID8K@FE 9<

:FE`ID@E> D8AFI@KP 8E; N<CC;@JG<IJ<; GI<J<E:<J F= ,L 8E; ) <C<D<EKJ

 8E;  8K  I<JG<:K@M<CP N?@C< .@  8K  @J 98I<CP F9

J<IM<; J@E:< @K 8:KJ 8J JL9JKI8K< F= K?< ,L):F8K@E> J F9J<IM<; @E K?<

JLGGFIK@E> @D8>< K?< .@)JL9JKI8K< ?8J 9<<E :FDGC<K<CP :FM<I<; 9P

K?< EFEJ<D@:FE;L:K@M< G?8J< ,L) N?<E:< @KJ G?FKF<O:@K8K@FE @J LE

C@B<CP KF 8I@J< ;LI@E> /0 @CCLD@E8K@FE N?@:? ELCC@`<J @KJ G?FKF8:K@M@KP

KFN8I;J K?< #* <C@D@E8K@FE

 2,*:85*/,30*(2 */(8(*:,80@(:054 5- "

P:C@: MFCK8DD<KIP N8J @EM<JK@>8K<; FE K?< .@.@)–,L)8EF;< @E

9FK?  DFC &−(8-)JFCLK@FE 8E;  DFC &−(8C @E GI<J<E:<

8E; 89J<E:< F= #* LJ@E> 8 J:8E I8K< F=  D0 J− @>  .?@J 8E8CPJ@J

N8J :FE;L:K<; KF ;<K<ID@E< K?< <C<:KIF:?<D@:8C GIF:<JJ<J F::LII@E> FE

K?< 8EF;<<C<:KIFCPK< @EK<I=8:< 8E; K?<@I I<>@FEJ F= MFCK8>< CC MFCK8D

D<KIP <OG<I@D<EKJ N<I< JK8IK<; KFN8I;J K?< 8EF;@: ;@I<:K@FE J F9

J<IM<; @E K?< :LIM< :FE;L:K<; @E K?< #*  (8-)<C<:KIFCPK<  @>

8 FECP FE< 8EF;@: GIF:<JJ @J F9J<IM<; 8IFLE;  0 MJ >>C N?@:?

@J DFJK C@B<CP 8JJF:@8K<; N@K? K?< FOP><E <MFCLK@FE I<8:K@FE ), I<

8:K@FEJ – 8E; – J@E:< EF FK?<I <C<:KIF8:K@M< JG<:@<J :8E 9< FO@

;@Q<; @E K?@J I<>@FE F= MFCK8>< &@B<N@J< EF I<;L:K@FE GIF:<JJ<J N<I<

I<>@JK<I<; N?<E K?< J:8E N8J @EM<IK<; @E K?< FGGFJ@K< ;@I<:K@FE 0FCK8D

D<KIP ;8K8 :FCC<:K<; @E K?< 89J<E:< F= #* EFK J?FNE JL>><JKJ K?8K

Table 2

-G<:@`: <EP :FEJLDGK@FEJ 8E; G<I:<EK8>< F= .) I<DFM<; 8J 8 =LE:K@FE F= G" 8E; :LII<EK ;<EJ@KP @E :?CFI@;< D<;@8

OG<I@D<EK #*μDFC& −$D:D −G" .),<DFM<; /:<CC0 &8DGGFN<I^1 :B1?D −

       

       

       

       

       

       



UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

Fig. 1. P:C@: MFCK8DD<KIP :FE;L:K<; FE .@.@),L)8EF;< @E ;@==<I<EK JLGGFIK@E>

<C<:KIFCPK<J 8  DFC &−(8-)8E;  ^DFC &−#* 9  DFC & (8C 8E;

 ^DFC &−#* 8E; :  DFC & (8C -:8E I8K<  D0J−8E; G" 

K?@J :FDGFLE; ;F<J EFK ;@I<:KCP FO@;@Q< FE K?< 8EF;< JLI=8:< J@E:< K?<

FEJ<K GFK<EK@8C F= K?< 8EF;@: J:8E @J EFK DF;@`<; @= :FDG8I<; 8>8@EJK

K?< <OG<I@D<EK @E @> 8 K?LJ @E;@:8K@E> K?8K #* @J <EFL>? I<:8C

:@KI8EK KF 9< ;@I<:KCP KI8EJ=FID<; FE K?< - 8E; FECP ), F::LIJ

@E K?< (8-)JFCLK@FE I<>8I;C<JJ F= K?< GI<J<E:< F= K?< :FEK8D@E8EK

1?<E (8C @J @E:FIGFI8K<; @EKF K?< JFCLK@FE  @> 9 : K?< J?8G<

F= K?< MFCK8DDF>I8D CFFBJ J@D@C8I @E K?< 8EF;@: I<>@FE ?FN<M<I 8

:CFJ< @EJG<:K@FE @E K?< FEJ<K F= K?< FO@;8K@FE GIF:<JJ<J I<M<8CJ K?8K @K

N8J J?@=K<; 8GGIFO@D8K<CP  D0 DFI< E<>8K@M< @E;@:8K@E> K?< F::LI

I<E:< F= 8 ;@==<I<EK GIF:<JJ K?8E ), @E (8-) @> 8 <M@;<E:@E>

8E <==<:K F= K?< :?CFI@;< GI<J<E:< 8E; 8:K@M< :?CFI@E< JG<:@<J =FID<;

;L< KF K?< ;@JGC8:<D<EK F= K?< FEJ<K GFK<EK@8CJ 8E; GFJJ@9C< @E?@9@

K@FE F= ), 56 #E K?< 98:BN8I; J:8E  @> 9 8 I<;L:K@FE G<8B

@J ;<K<:K<; 8IFLE;  0 MJ >>C I<C8K<; KF K?< GI<M@FLJ FO@;8K@FE

@==<I<EK JKL;@<J ?8M< JL>><JK<; K?< :?CFI@;< FO@;8K@FE KF =FID 8:K@M<

:?CFI@E< JG<:@<J I<8:K@FEJ –: FE .@.@)–,L);L< KF K?< :?CFI@;<

@FE :FEK<EK @E K?< <C<:KIFCPK< 8E; K?< JL9J<HL<EK I<;L:K@FE F= K?<J<

:FDGFLE;J @E K?< I<M<IJ<; JN<<G 56 K?LJ :FE`ID@E> K?< :8K

8CPK@: 8:K@M@KP F= K?@J G?8J< KFN8I;J :?CFI@;< FO@;8K@FE ), :FE:LI

I<EKCP 8I@J<J 8J G8I8J@K@: I<8:K@FE 8K DFI< GFJ@K@M< GFK<EK@8CJ FE K?< <C<:

KIF;< JLI=8:< 1?<E #* @J 8;;<; KF K?< <C<:KIFCPK<  @> 9 EF ;@=

=<I<E:<J 8I< I<>@JK<I<; @E K?< MFCK8DDF>I8D @E K?< FO@;8K@FE 9I8E:?

8>8@E JL>><JK@E> K?8K K?@J GFCCLK8EK :8EEFK 9< ;@I<:KCP FO@;@Q<; FE K?<

JPEK?<J@Q<; - ;L< KF @KJ I<:8C:@KI8EK :?8I8:K<I "FN<M<I K?< :?8I><

@E K?< I<;L:K@FE G<8B @J CFN<I =FI K?< <OG<I@D<EK :FE;L:K<; @E K?<

#* GI<J<E:<  @> 9 K?8E @E @KJ 89J<E:<  @> : ;L< KF K?< :FE

JLDGK@FE F= 8:K@M< :?CFI@E< JG<:@<J 9P K?@J :FEK8D@E8EK N?@:? 8I<

EFK <==<:K@M<CP I<;L:<; FE K?< - JLI=8:< 0FCK8DD<KIP J:8EJ :FE

;L:K<; FE K?< .@.@)–,L):8K8CPJK @E (8C D<;@8 I<M<8C<; K?8K K?<

J?8G< F= K?< MFCK8DDF>I8DJ I<D8@E LE8CK<I<; 8=K<I  :P:C<J EFK

J?FNE ;<DFEJKI8K@E> K?< JK89@C@KP F= K?< JPEK?<J@Q<; 8EF;<

#E C@E< N@K? K?< 89FM< I<JLCKJ 8 I<:<EK JKL;P ?8J GIFGFJ<; K?< =FC

CFN@E> I<8:K@FE D<:?8E@JD FE ,L98J<; <C<:KIF;< D8K<I@8CJ =FI :?CFI@;<

FO@;8K@FE 8E; :FE:FD@K8EKCP F::LII<E:< F= ), @E K?< I8E>< F= G" =IFD

 KF  LJ@E> ;@==<I<EK@8C <C<:KIF:?<D@:8C D8JJ JG<:KIFJ:FGP '-

56





8

9

:







N?<I< ;<J:I@9<J 8E 8:K@M< J@K< FE 8E FOP><E 8KFD F= K?< :8K8CPJK

JLI=8:< 8E; 8E 8;JFI9<; @EK<ID<;@8K< JG<:@<J FE K?< JLI=8:< 

 (FK< @E K?< 89FM< D<:?8E@JD K?8K K?< ")C @J K?< GI<;FD@E8EK

:?CFI@E< JG<:@<J @E K?@J I8E>< F= G" N?@C< )C−GI<;FD@E8K<J 8K G" M8C

L<J ?@>? KF K?< =I8:K@FE F= 8HL<FLJ 8:K@M< :?CFI@E<

JG<:@<J 8J 8 =LE:K@FE F= G" -LGGFIK@E> @E=FID8K@FE  .?LJ K?<J< KNF

:?CFI@E< JG<:@<J :FLC; 8:K 8J @E@K@8C FO@;8EKJ @E K?< ?FDFCPJ@J F::LII@E>

=FI K?< /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ KF ;<JKIFP K?< #* :FEK8D@

E8EK

  +,.8(+(:054 ;904. #$6/5:5*/,30*(2 ,2,*:85*/,30*(2 (4+ #$

(9909:,+ ,2,*:85*/,30*(2 685*,99,9

 :FDG8I@JFE F= K?< #* ;<>I8;8K@FE N8J :8II@<; FLK KF ;<K<ID@E8K<

K?< @E;@M@;L8C G<I=FID8E:< F= <8:? K<:?E@HL< 8E; K?< GFJJ@9C< JPE<I

>@JD <O@JK@E> 9<KN<<E K?< G?FKF:?<D@:8C 8E; <C<:KIF:?<D@:8C GIF:<JJ<J

@> 8 J?FNJ K?< ;<:8P F=  ^DFC &−#* @E  DFC &−(8C

G"   8J 8 =LE:K@FE F= K@D< ;LI@E>  D@E F= ;<>I8;8K@FE 8;FGK

@E> K?< =FCCFN@E> <OG<I@D<EK8C :FE;@K@FEJ ;@I<:K /0  ED @E K?<

89J<E:< F= 8E <C<:KIF;< G?FKF:?<D@:8C /0 ED  D :D 8G

GC@<; FE K?< .@.@)–,L)8EF;< <C<:KIF:?<D@:8C  8E; ;@I<:K /0

 ED 8GGCP@E>  D :D FE K?< <C<:KIF;< /08JJ@JK<; <C<:KIF:?<D

@:8C   /0 ED J F9J<IM<; K?< /0 ED GIF:<JJ GI<J<EKJ

8 JCFNI8;8K@FE @= :FDG8I<; 8>8@EJK K?<  D<K?F; I<DFM@E> 

 F= #* 8=K<I K?< KI<8KD<EK  ]  D@E − .?< =8:K K?8K

K?<I< @J 8 I<D8@E@E> :FE:<EKI8K@FE F= #* 8=K @II8;@8K@FE G<

I@F; 8E; <C<:KIFCPJ@J  D@E ?@>?C@>?KJ K?< I<:8C:@KI8EK :?8I8:K<I F=

K?@J GFCCLK8EK )E K?< FK?<I ?8E; K?<  GIF:<JJ 8:?@<M<J 8 =8JK :FE

K8D@E8EK I<DFM8C  ]  D@E − <M<E 8=K<I K?<  D@E F=

KI<8KD<EK   FE 8::FLEK F= K?< 8:K@M< :?CFI@E< GIF;L:K@FE N?@:?

8:KJ 8J D8@E FO@;8EK "FN<M<I 8 =LCC #* <C@D@E8K@FE @J EFK 8KK8@E<; 8=

KC< D<K?F; N?@C< @KJ D8AFI ;I8N98:B @J @KJ CFN

D@E<I8C@Q8K@FE ;<>I<< 8J GI<M@FLJCP I<GFIK<; =FI FK?<I :FEK8D@E8EKJ

5–6 &@B<N@J< 8 :FEJ@;<I89C< #* ;<>I8;8K@FE F::LIJ @E K?< /08J

J@JK<; <C<:KIF:?<D@:8C GIF:<JJ   /0 ED 9LK @KJ :FE:<EKI8K@FE

8:KL8CCP ;<:8PJ KF  @E 8GGIFO@D8K<CP  D@E  ]  D@E−

@E;@:8K@E> 8 :C<8I JPEP 9<KN<<E K?< <C<:KIF:?<D@:8C 8E; G?FKF:?<D

@:8C K<:?E@HL<J 8E; 8 JLG<I@FI G<I=FID8E:< 8>8@EJK K?< J@E>C< LJ< F=

K?<J< JPJK<DJ -G<:@=@:8CCP K?@J 9<?8M@FI :FLC; 9< ;L< KF K?< ?FDFC

PJ@J F= K?< 8:K@M< :?CFI@E< JG<:@<J <C<:KIF><E<I



UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

Fig. 2. <>I8;8K@FE F= 8  ^DFC &−#* 9P ;@I<:K /0  ED @II8;@8K@FE /0  ED

G?FKFCPJ@J ;@I<:K <C<:KIF:?<D@:8C ;<>I8;8K@FE  8E; /08JJ@JK<; <C<:KIF:?<D@:8C

GIF:<JJ   /0  ED 8E; 9 FO@;8EKJ JG<:@<J <MFCLK@FE ;LI@E> K?< ;@==<I<EK KI<8K

D<EK JPJK<DJ FE;@K@FEJ  DFC & (8C 8E; G"  

8K<; FE K?< .@.@)–,L)<C<:KIF:8K8CPJK 8E; =I8>D<EK<; 9P K?< /0

 ED I8;@8K@FE C<8;@E> KF K?< GIF;L:K@FE F= ?@>?CP I<8:K@M< I8;@:8CJ 

   @E JFCLK@FE J ;<J:I@9<; 89FM< :?CFI@E< JG<:@<J

;F EFK GI<J<EK 8 ?@>? FO@;8K@FE GFK<EK@8C =FI GFCCLK8EK ;<>I8;8K@FE 8J

I8;@:8CJ :FE`ID@E> K?<@I IFC<J @E K?< I<JLCKJ J?FNE @E @> 8 KFN8I;J

K?< #* <C@D@E8K@FE   /0 ED .?@J `E;@E> N@CC 9< 8CJF :FE

`ID<; @E K?< .) 8E8CPJ@J J?FNE 9<CFN ::FI;@E> KF K?< <C<:KIF:8K

8CPK@: D<:?8E@JD GI<J<EK<; 89FM< @E I<8:K@FEJ – =FI 8:K@M< :?CFI@E<

GIF;L:K@FE K?< =FCCFN@E> D<:?8E@JD @J GIFGFJ<; KF 8::FLEK =FI K?< GFJ

J@9C< I8;@:8C =FID8K@FE @E K?< /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ

:





.?< @II8;@8K@FE F= 8K λ  ED GIF;L:<J 8E;

M@8 ?FDFCPK@: :C<8M8>< H  56 ;;@K@FE8CCP  

:8E 9< =FID<; <HJ – -LGGFIK@E> @E=FID8K@FE  ;L< KF K?<

@EK<I8:K@FE F= 8E; N@K? :?CFI@;< 8E; N8K<I 56 #E

8;;@K@FE :8E I<8:K N@K? N8K<I KF GIF;L:< <H  -LG

GFIK@E> @E=FID8K@FE  N?@:? :8E ;<:FDGFJ< KF =FID 8;;@K@FE8C

<H  -LGGFIK@E> @E=FID8K@FE  (FK< K?8K 8E; FK?<I I8;@:8C

FO@;8EKJ 8I< ?<I<@E LJ<; KF 8JJ@JK KF <C@D@E8K< K?< :@GIFaFO8:@E

8E; @KJ @EK<ID<;@8K<J 8;;@K@FE8CCP K?<J< I8;@:8CJ :8E I<8:K <8:? FK?<I

JLGGFIK@E> @E=FID8K@FE  N?<I<9P @K @J ;@=`:LCK KF ;<K<:K K?<D 8K

K?< <E; F= KI<8KD<EK .?< :F<O@JK<E:< F= )C−?8J 9<<E :FE`ID<;

8CFE> N@K? ")C 8IFLE; E<LKI8C G" M8CL<J 98J<; FE

'- D<8JLI<D<EKJ =FI ,L98J<; 8EF;<J 56 8E; JLGGFIK<; 9P K?<I

DF;PE8D@: :8C:LC8K@FEJ -LGGFIK@E> @E=FID8K@FE  N?<I<9P K?@J FO@

;8EK :FLC; G?FKF;<:FDGFJ< @EKF K?< ;@==<I<EK JG<:@<J GIFGFJ<; @E I<8:

K@FE  8CJF @E;@:8K@E> K?8K K?< /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ I<C@<J

FE G" 8J 8 I<JLCK F= K?< ")C )C−I8K@F @E JFCLK@FE =FI G"   8J

;<J:I@9<; @E 9I<M@KP

.?< 89FM< D<:?8E@JD :FEJ@;<IJ 8CC K?< GFJJ@9@C@K@<J K?8K :8E 9< GIF

;L:<; 9P K?< ?FDFCPJ@J F= D8@E 8:K@M< :?CFI@E< JG<:@<J ")C 8E; )C−

N?<E JL9A<:K<; KF /0 @II8;@8K@FE #K J?FLC; 9< 9FIE< @E D@E; K?8K DFJK

F= K?<J< :FDGFLE;J :8EEFK 9< <OG<I@D<EK8CCP ;<K<ID@E<; <> JFD< F=

K?<D 8I< EFK MFC8K@C< KF 9< ;<K<:K<; @E '- K?<I< 8I< EFK I8;@:8C J:8M

<E><IJ :LJKFDK8@CFI<; N?<I<9P K?<P J?FLC; 9< GI@D8I@CP 8JJLD<; 8J 8

GFJJ@9@C@KP 9<PFE; K?< I<8:K@FE J:?<D< GIFGFJ<; =FI K?< 98J@: =I8>D<E

K8K@FE ;<J:I@9<; 9P I<8:K@FEJ  8E;  (<M<IK?<C<JJ @K @J GFJJ@9C< KF

;<K<ID@E< K?< FO@;8K@FE :8G8:@KP F= K?< @E;@M@;L8C JPJK<DJ /0G?FKF

:?<D@:8C <C<:KIF:?<D@:8C 8E; /08JJ@JK<; <C<:KIF:?<D@:8C KF @E=<I K?<

:I<8K@FE F= JFD< F= K?<J< I8;@:8CJ @> 9 ;<J:I@9<J K?< FM<I8CC GIF

;L:K@FE F= FO@;8EKJ 8=K<I  D@E 8J ;<K<ID@E<; 9P @F;FD<KIP -<:K@FE

  :FEJ@;<I89C< ;@D@ELK@FE @E K?< ><E<I8K@FE F= FO@;8EKJ @J F9

J<IM<; N?<E K?< <C<:KIF><E<I8K<; 8:K@M< :?CFI@E< @J <OGFJ<; KF /0

C@>?K   /0 ED @E :FDG8I@JFE N@K? K?< J@E>C< <C<:KIF:?<D@

:8C GIF:<JJ  K?LJ JLGGFIK@E> K?< =FID8K@FE F= JFD< I8;@:8C JG<:@<J

89FM< GIFGFJ<;

 E,*: 5- *;88,4: +,490:? (4+ 6 54 :/,  +,.8(+(:054 ;904. #$

(9909:,+ ,2,*:85*/,30*(2 685*,99

)E:< K?8K K?< JLG<I@FI :8G8:@KP F= #* ;<>I8;8K@FE ?8J 9<<E ;<DFE

JKI8K<; LJ@E> /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ :FDG8I<; KF K?<@I @E

;@M@;L8C G<I=FID8E:<J G?FKF:?<D@:8C 8E; <C<:KIF:?<D@:8C ;@==<I<EK

<OG<I@D<EKJ N<I< :8II@<; FLK N@K? K?< 8JJ@JK<; K<:?E@HL< KF <M8CL8K<

K?< @EaL<E:< F= :LII<EK ;<EJ@KP  8E;  D :D− 8E; @E@K@8C G" M8C

L<J   8E;  LGFE K?< GFCCLK8EK ;<>I8;8K@FE (FK< K?8K ?@>?<I :LI

I<EK M8CL<J N<I< EFK :FEJ@;<I<; J@E:< K?<P :FLC; =8MFI K?< <E?8E:<

D<EK F= K?< ), D<:?8E@JD FM<I K?< :?CFI@;< FO@;8K@FE K?LJ :FD

GIFD@J@E> K?< :LII<EK <=`:@<E:P F= K?< GIF:<JJ 8E; K?< FO@;8EK GIF;L:

K@FE LII<EK ;<EJ@KP 8E; G" 8I< @DGFIK8EK J@E:< K?<P 8I< I<C8K<; KF

K?< :?8I>< KI8EJ=<I :LII<EK <=`:@<E:P 8E; <EP :FEJLDGK@FE 8E; K?<

:?<D@:8C JKIL:KLI< 8E; GI<;FD@E8E:< F= <C<:KIF><E<I8K<; JG<:@<J I<

JG<:K@M<CP .?< G" @J 8CJF @DGFIK8EK @E K?< FO@;8K@FE GIF:<JJ J@E:< @K @J

;@I<:KCP 8JJF:@8K<; N@K? K?< ;<>I8;8K@FE I8K< ;L< KF ;@==<I<EK G%8 =FI

#* G%8  G%8  G%8 – G%8 –

56 #E 8;;@K@FE K?< I8K< F= =I<< 8:K@M< :?CFI@E< JG<:@<J G?FKFCPJ@J @J G"

;<G<E;<EK 56 CC K?< <OG<I@D<EKJ N<I< :FE;L:K<; @E <C<:KIFCPK<J :FE

K8@E@E>  ^DFC & #* 8E;  DFC & (8C LJ@E> .@.@)–,L)8J

8EF;< 8E; ;@I<:K /0  ED @II8;@8K@FE @> 8 J?FNJ K?< <==<:K F= K?<

@E@K@8C G" M8CL<   8E;  @E K?< #* :FE:<EKI8K@FE ;<:8P 8K `O<; :LI

I<EK ;<EJ@KP F=  D :D− J F9J<IM<; K?< <C@D@E8K@FE F= K?@J :FEK8D@

E8EK @J :FEJ@;<I89C< =8JK J@E:< @KJ :FE:<EKI8K@FE ?8J M@IKL8CCP ;<:8P<; KF

 @E C<JJ K?8E  D@E N?@C< K?<I< @J 8E @EaL<E:< F= K?< @E@K@8C G" M8CL<

.?< #* 898K<D<EK CFFBJ J@D@C8I =FI G"  8E;  N?@:? @J EFK JLIGI@J

@E>CP ;L< KF K?< :F<O@JK<E:< F= ")C 8E; )C JG<:@<J @E K?@J I8E>< F=

G" N?@:? :8E >@M< I@J< KF K?< ELD<IFLJ I8;@:8CJ 89FM< GIFGFJ<; <>

 KF ;<JKIFP K?< #* 8IFLE;  D@E -C@>?K ;@==<I<E:<J

8I< ;<K<:K<; @E ?@>?<I B8GG M8CL<J =FI G"   ]  D@E @= :FD

G8I<; 8>8@EJK G"   ]  D@E @EJ<K F= @> 8 DFJK C@B<CP

;L< KF 8 D8AFI 89LE;8E:< F= ")C 8K CFN @E=FI

D8K@FE  N?@:? =8MFI K?< =FID8K@FE ;;@K@FE8C ;@==<I<E:<J @E

KI<8KD<EK 9<KN<<E K?<J< KNF G" M8CL<J :FLC; 9< ;<K<:K<; @E K?< 8DFLEK

F= #* @EK<ID<;@8K<J <C@D@E8K<; =IFD K?< JFCLK@FE 8J 8E8CPQ<; 9<CFN

-LGGFIK@E> @E=FID8K@FE  E <EP :FEJLDGK@FE F=  B1 ? D @J

:8C:LC8K<; =FI 8EP F= K?<J< GIF:<JJ<J LJ@E>  D :D−8J :LII<EK ;<EJ@KP

.89C< 



UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

Fig. 3. ==<:K F= @E@K@8C G" FE K?<  ^DFC &−#*  DFC & (8C /08JJ@JK<; <C<:

KIF:?<D@:8C KI<8KD<EK 8K K?I<< ;@==<I<EK G" M8CL<J   8E;  8GGCP@E> 8 :LII<EK ;<EJ@KP

F= 8  8E; 9  D:D

1?<E K?< G" @J CFN<I<; ;FNE KF  ")C I<D8@EJ 8J K?< GI<;FD@

E8EK JG<:@<J 9LK )C−J?@=KJ KF C8J K?< :F<O@JK<EK :FDGFLE; N?<I<9P

K?< FM<I8CC FO@;8K@FE :8G8:@KP F= K?< JPJK<D @J 8CK<I<; .?@J :FE;@K@FE

@J I<a<:K<; 9<:8LJ< @J EFK 8::FDG8E@<; 9P  9LK I<

JLCK@E> =IFD C?FDFCPQ<J 9P /0  @II8;@8K@FE 56 8::FI;@E> KF

<HJ – @E K?< -LGGFIK@E> @E=FID8K@FE  .?< GIF;L:K@FE 8CFE>

N@K? K?< ?P;IFOPC I8;@:8C @E;L:<J 8 JC@>?KCP JCFNI8;8K@FE

@E :FDG8I@JFE N@K? K?8K FE< F9K8@E<; 8K G" M8CL<J F=  8E;   @>

8 98J<; FE K?< I<HL@I<D<EK F= 8GGIFO@D8K<CP  D@E KF ;<JKIFP K?<

N?FC< :FEK8D@E8EK .?@J @J 8CJF JLGGFIK<; @E 8 CFN B 8GG M8CL< <HL8CJ

 ]  D@E #K @J NFIK?N?@C< D<EK@FE@E> K?8K 8K K?@J G" K?< =FI

D8K@FE F= Z I<;FO   0 MJ -" <H  -LGGFIK@E> @E=FI

D8K@FE  :FLC; 9< =8MFI<; 56

@> 9 <O?@9@KJ K?< #* :FE:<EKI8K@FE ;<:8P ;LI@E> 8 J@D@C8I 8J

J@JK<; KI<8KD<EK 8J 8GGC@<; @E @> 8 9LK 8K 8 :LII<EK ;<EJ@KP F=

 D :D− #K @J <M@;<EK K?8K K?< @E:I<8J< F= K?< :LII<EK aFN @E K?<

I<8:KFI J@>E@=@:8EKCP I<;L:<J K?< ;<>I8;8K@FE K@D< KF I<DFM< K?< <E

K@I< :FEK8D@E8EK @E  D@E @E :FDG8I@JFE N@K?  D :D− D@E

(FK JLIGI@J@E>CP 8 ?@>?<I 8DFLEK

F= :?CFI@E< JG<:@<J N?@:? N@CC 9< FE K?<@I KLIE =I8>D<EK<; @EKF I8;@

:8CJ 9P /0  ED @II8;@8K@FE KF G<I=FID K?< #* 898K<D<EK .?@J :LI

I<EK ;<EJ@KP N@CC 8CJF @EMFCM< 8 >I<8KP :FEJLDGK@FE F=  B1

? D− FE:<IE@E> K?< G" M8I@8K@FE K?< KI<E;J 8I< J@D@C8I KF K?8K F9

J<IM<; 8K K?< CFN<I :LII<EK ;<EJ@KP K?< <C@D@E8K@FE K<JKJ 8I< M@IKL8CCP

J@D@C8I 8K G"  8E;  I<DFM@E> K?< #* @E R D@E FECP ;@==<I@E> =FI

G"  N?@:? I<HL@I<J 8 ;FL9C< K@D< KF I<DFM< K?@J :FEK8D@E8EK .?@J

F9J<IM8K@FE 8CJF I<C@<J @E K?< =8:K K?8K K?< :F<O@JK<EK :?CFI@E< JG<:@<J @J

DF;@`<; KF GIF;L:< 

.?< 89FM< `E;@E>J I<M<8C<; K?8K K?< @E:I<8J< F= :LII<EK ;<EJ@KP @J

<==<:K@M< KF <E?8E:< K?< #* ;<>I8;8K@FE N?@C< K?< G" 8CJF ;@JGC8P<;

JFD< @EaL<E:< 8CK?FL>? J@D@C8I I<JLCKJ N<I< F9K8@E<; 8K G"  8E;  .F

=LIK?<I 8E8CPQ< K?<J< F9J<IM8K@FEJ .) D<8JLI<D<EKJ N<I< G<I=FID<;

=FI 8CC K?< <OG<I@D<EKJ J?FNE @E @> 8 8E; 9 J F9J<IM<; @E @>

 .) I<DFM8C @J <E?8E:<; 8K C8I><I :LII<EK ;<EJ@K@<J  D :D−

I<D8IB@E> DFI< J@>E@=@:8EKCP K?< ;@==<I<E:<J @EMFCM<; N@K? K?<J< M8I@

89C<J .?< ?@>?<JK I<DFM8C G<I:<EK8><J 8I< F9K8@E<; 8K G"   I<>8I;

C<JJ F= K?< 8GGC@<; :LII<EK :C<8ICP JLGGFIK@E> K?< =8:K K?8K K?< ?@>?

<JK :FE:<EKI8K@FE F= ")C @J GIF;L:<; 8K K?@J :FE;@K@FE @E FI;<I KF <E

?8E:< K?< GIF;L:K@FE N@K? K?< C8I><JK FO@;8K@FE :8G8:@KP M@8 /0

 ED @II8;@8K@FE .?< J<:FE; ?@>?<JK .) <C@D@E8K@FE @J ;<K<ID@E<;

8K G"  FM K?8K K?< ?FDFCPK@: GIF;L:KJ

I<JLCK@E> =IFD ")C  CGI<J<EKJ 8 ?@>?<I FO@;8K@FE :8G8:@KP K?8E

K?< ")C  )C−:FLGC< .?@J :FLC; JK<D FE K?< K?<IDF;PE8D@: FO@

;8K@FE GFK<EK@8CJ F= K?< 98J@: :?CFI@E< JG<:@<J   0 MJ

-"   0 MJ -" 8E;   0 MJ

-" N?<I< K?< MFCK8>< @E:I<8J<J @E K?< =FCCFN@E> FI;<I ")C  C

)C− .?LJ K?< I<JLCKJ @E @>  I<M<8C K?8K 8CK?FL>? K?< #* ;<>I8;8

K@FE :FLC; B@E<K@:8CCP GIF:<<; JCFN8@EJK G" 

8 ?@>?I<< @J 8:?@<M<; 8K K?< 8:@;@: G" M8CL< N?<I<

K?< #* @EK<ID<;@8K<J 8I< ;<>I8;<; =8JK<I K?8E @E K?< 8CB8C@E< G"

#E C@E< N@K? K?<J< I<JLCKJ @>  8E; -LGGFIK@E> @E=FID8K@FE  8E;

 ;<J:I@9< K?< GIF`C<J F= K?< #* 9PGIF;L:KJ ><E<I8K<; ;LI@E> <8:?

K<JK :8II@<; FLK @E .89C<   @>J  8E;  #EK<I<JK@E>CP K?< 8G

G<8I8E:< 8E; ;@J8GG<8I8E:< F= <8:? @EK<ID<;@8K< 8K G"  #*# 8E;

#*# 8E;  #*# ;@==<IJ I<>8I;@E> K?< GIF`C<J <JK@D8K<; 8K G"

 #*# 8E; #*# I<>8I;C<JJ F= K?< 8GGC@<; :LII<EK ;<EJ@KP .?<

@EK<ID<;@8K<J #*# #*# 8E; #*# 8I< <C@D@E8K<; =8JK

 D:D− N?<I< K?< #* ;<>I8;8K@FE @J @DGFIK8EK ;L< KF K?< >I<8K

<JK ")C GIF;L:K@FE ><E<I8K@E> FE @KJ KLIE K?< ?P;IFOPC I8;@:8C 8E;

FK? KF <HJ –8E; -LGGFIK@E> @E=FID8K@FE  #E

8;;@K@FE K?< 8JJ@JK<; GIF:<JJ D@E<I8C@Q<J DFI< <=`:@<EKCP 8K G"  8E;

 8E; 8C@G?8K@: 8:@;J ) 8E;  8I< =FID<; -LGGFIK@E> @E=FID8

Fig. 4. .FK8C FI>8E@: :8I9FE .) I<DFM8C =FI K?<  ^DFC &−#*  DFC & (8C

/08JJ@JK<; <C<:KIF:?<D@:8C KI<8KD<EK 8K K?I<< ;@==<I<EK G" M8CL<J   8E;  8E; ;@==<I

<EK 8GGC@<; :LII<EK ;<EJ@K@<J  8E;  D:D



UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

Fig. 5. PGIF;L:K #*# #*# 8E; #*# :FE:<EKI8K@FEJ 8J 8 =LE:K@FE F= G" :LII<EK ;<EJ@KP 8E; K@D< ;LI@E> /08JJ@JK<; <C<:KIF:?<D@:8C KI<8KD<EK =FI #*

K@FE  IFD K?< =I8:K@FE F= 8HL<FLJ :?CFI@E< JG<:@<J 8J 8 =LE:K@FE

F= G" -LGGFIK@E> @E=FID8K@FE  89JFIGK@FE JG<:KI8 F= 8E;

 -LGGFIK@E> @E=FID8K@FE  K?< DFC8I 89JFIGK@FE :F<=`:@<EK F=

8K /0  ED @J ;@==<I<EK =IFD K?8K F=  JJLD@E> K?8K

K?< G?FKFCPJ@J F= 8E; 8I< KNF @E;<G<E;<EK GIF:<JJ<J 8E;

K?8K K?< @EK<I8:K@FEJ 9<KN<<E K?<J< KNF GIF:<JJ<J 8I< E<>C@>@9C< ;L< KF

K?< =I8:K@FE 8HL<FLJ FECP 8 LE@HL< :FDGFE<EK FI  @J

GI<J<EK @E =I<< :?CFI@E< J8DGC<J 8K G"  FI  K?<I<=FI< FO@;8EK I<8:

K@M< JG<:@<J <HJ 8E;  8I< =FID<; 9LK K?@J 9<?8M@FI 8K G"   ;F<J

EFK F::LI 9<:8LJ< 8I< EFK GI<J<EK

 ,.8(+(:054 6(:/=(? 5- 

"*& 8E8CPJ<J ;LI@E> K?< `IJK  D@E F= <C<:KIFCPJ@J  ^DFC &−

@E@K@8C G"   1  D:D  DFC &−(8C  ^1:D /0

C@>?K @EK<EJ@KP J?FN<; 8 GIF>I<JJ@M< ;@J8GG<8I8E:< F= #* 8E; @EK<I

D<;@8K< =FID8K@FEJ -LGGFIK@E> @E=FID8K@FE  8E; ) .?< @EK<ID<;@

8K< :FE:<EKI8K@FEJ I<8:?<; 8 D8O@DLD M8CL< 8E; K?<E ;<:I<8J<; LE

K@C M8E@J?@E> ;LI@E> K?< `IJK  D@E  @>  #EK<ID<;@8K<J F= #*#

#*# 8E; #*# N<I< @;<EK@`<; 9P "*& 9P :FDG8I@E> K?<@I I<K<E

K@FE K@D<J 8E; /0 JG<:KI8 56 /EC@B< K?@J JKL;P N?<I< #* D@E<I8C

@Q8K@FE N8J EFK 8:?@<M<;  .) I<DFM8C @E  ? 9P FECP LJ@E> <C<:

KIF><E<I8K<; 8:K@M< :?CFI@E< FI <M<E @E ?<K<IF><E<FLJ G?FKF:8K8CPK@:

GIF:<JJ<J 56 N< ?<I<@E @EM<JK@>8K<; K?< D@E<I8C@Q8K@FE :8G8:@KP

F= K?< /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ I<M<8C@E> K?8K K?@J JPEP

@J 89C< KF J@>E@=@:8EKCP @E:I<8J< K?< #* D@E<I8C@Q8K@FE @E 8HL<FLJ JFCL

K@FE @E 8 HL8IKC< <C<:KIF:?<D@:8C GIF:<JJ

 @>  -@E:< K?<I< N<I< EF JK8E;8I;J =FI K?<J< GIF;L:KJ K?<P :8E

FECP 9< :C8JJ@`<; 8J K<EK8K@M< :8E;@;8K<J C@G?8K@: @EK<ID<;@8K<J FO

8C@: 8:@; 8E; =FID@: 8:@; ) 8E;  I<JG<:K@M<CP N<I< @;<EK@`<; 9P

:FDG8I@E> K?<@I I<K<EK@FE K@D<J N@K? K?8K F= JK8E;8I; I<8><EKJ 8I@J@E>

8=K<E

<I8K<; @EK<ID<;@8K<J @EKF DFI< FO@;@Q<; :FDGFLE;J 8J<; FE K?< @;<E

K@`:8K@FE F= I<8:K@FE @EK<ID<;@8K<J D@E<I8C <E;GIF;L:KJ 8E; .) I<

DFM8C M8CL<J 8 GC8LJ@9C< D@E<I8C@Q8K@FE G8K?N8P @J JL>><JK<; @E @>

=FI #* LJ@E> K?< ")•8J D8@E FO@;8EK .F K?@J :FE:<IE #*#

N8J K?< GI@E:@G8C 9PGIF;L:K 8J 8 :FEJ<HL<E:< F= K?< G@G<I8QPC I@E> 8K

K8:B M@8 8E @E@K@8C ")•KI8EJ= KF K?< ILGKLI<

F= K?< ( 9FE; 8E; JL9J<HL<EKCP CFJJ F= "F= #* 8E; JL9J<HL<E:<

=FID8K@FE F= 9PGIF;L:K #*# #E 8;;@K@FE 8J :FEJ<HL<E:< F= K?< JL:

:<JJ@M< ;<>I8;8K@FE F= @EK<ID<;@8K< #*# FE ( K?< CFJJ F= K?< KFK8C

G@G<I8QPC I@E> =FID<; K?< 9PGIF;L:K #*# <M@;<E:@E> K?8K K?< :LI

I<EK ;<EJ@KP C@D@KJ K?< B@E<K@: 8E; K?< D<:?8E@JD F= #* ;<>I8;8K@FE

.?<J< @EK<ID<;@8K<J #*# #*# 8E; #*# ?8M< 9<<E 8CJF I<

GFIK<; =FI FK?I8;8K@FE GIF:<JJ<J FI @EJK8E:< #*# 8E; #*#

N<I< =FLE; 9P E <K 8C ;LI@E> K?< #* ;<>I8;8K@FE :FE;L:K<; N@K?

J<M<I8C =I<< I8;@:8CJ ")••(8E; -)•56 8E; F;; <K 8C ;LI

@E> N8K<I :?CFI@E8K@FE GIF:<JJ<J F= aLIFHL@EFCFE<J 56 #*# N8J

=FLE; 9P *8CD8 <K 8C ;LI@E> K?< <C<:KIF:?<D@:8C :FEM<IJ@FE F= #* LJ@E>

- 8EF;<J 56 @E8CCP @E;<G<E;<EK F= K?< #* ;<>I8;8K@FE G8K?N8P

=FID@: 8E; FO8C@: 8:@;J N<I< =FID<; 8J `E8C 9PGIF;L:KJ @E  ? JLG

GFIK@E> @E=FID8K@FE  <JG@K< KFO@:@KP K<JKJ F= KI<8K<; JFCLK@FE N<I<

EFK G<I=FID<; K?< E8KLI< F= K?< =FID<; @EK<ID<;@8K<J N8J J@D@C8I KF

K?8K F9K8@E<; @E 8 GI<M@FLJ JKL;P 56 N?<I< K?< 8EK@9@FK@: 8:K@M@KP

N8J I<DFM<; 8=K<I  D@E #E 8;;@K@FE K?< =FID8K@FEJ F= =FID@: 8E;

FO8C@: 8:@; <M@;<E:< K?< JL::<JJ@M< 9I<8B@E> F= K?<   9FE; @E K?<

#* K?LJ KI8EJ=FID@E> @K @EKF :FEJ@;<I89CP C<JJ ?8IDC<JJ :FDGFLE;J

.?<J< `E8C 9PGIF;L:KJ :8E 9< :8II@<; LG KF )@< KFK8C D@E<I8C@Q8

K@FE LJ@E> CFE>  LIK?<IDFI<

@K GFJJ@9C< K?8K K?< C−8:K@M< =FID8K@FE @E GI<J<E:< F= (FI>8E@:J K?8K

I<C<8J< 8DDFE@8 D8P P@<C; :?CFI8D@E<J "FN<M<I LE;<I :FE;@K@FEJ F=

CFN :FE:<EKI8K@FEJ F= :?CFI@;< 8E; K?< :FDG<K@K@M< I<8:K@FEJ F= FK?<I

@FE@: JG<:@<J @E JFCLK@FE :?CFI8D@E<J 8I< EFK =FID<; ;LI@E> K?< <C<:KIF

:?<D@:8C FO@;8K@FE 56

4. Conclusions

#E FI;C< 8;M8E:<; FO@;8K@FE

GIF:<JJ<J @E K<IDJ F= D@E<I8C@Q8K@FE KFN8I;J I<:8C:@KI8EK FI>8E@: :FD

GFLE;J 8E; K@D< K?< GI<J<EK JKL;P 8::FLEKJ =FI K?< ?FDFCPJ@J F= 8:K@M<

:?CFI@E< JG<:@<J JL9A<:K<; KF /0 @II8;@8K@FE LE;<I M<IP CFN aL<E:P

I8K<  ^1 :D−λ  ED N?@:? =8MFI89CP C<8;J KF K?< ><E<I

8K@FE F= I8;@:8CJ N@K? ?@>?<I FO@;8K@FE GFK<EK@8CJ :FDG8I<; KF :?CFI@E<

.?<J< FO@;8EKJ N<I< <C<:KIF><E<I8K<; FE 8 JPEK?<J@Q<; .@.@),L)

- <DGCFP@E> 8 *<:?@E@ D<K?F; 8E; JL9J<HL<EKCP :?8I8:K<I@Q<; LJ@E>

2I8P ;@==I8:K@FE 8E; -'

 :FDG8I@JFE F= #* ;<>I8;8K@FE  ^DFC &−@E  DFC &−(8C

G"   ;LI@E>  D@E :FE;L:K<; N@K? /0G?FKF:?<D@:8C /0



UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

Fig. 6. <>I8;8K@FE G8K?N8P GIFGFJ<; =FI #* 9P /08JJ@JK<; <C<:KIF:?<D@:8C KI<8KD<EK

 ED <C<:KIF:?<D@:8C  D :D FE - 8E; /08JJ@JK<; <C<:KIF

:?<D@:8C GIF:<JJ<J /0 ED  D :D FE - <E89C<; KF ;<

K<ID@E< K?8K @KJ :FE:<EKI8K@FE ;<:8P<; KF  @E 8GGIFO@D8K<CP  D@E @E

;@:8K@E> 8 :C<8I JPEP 9<KN<<E K?< <C<:KIF:?<D@:8C 8E; G?FKF:?<D@:8C

K<:?E@HL<J 8E; 8 JLG<I@FI G<I=FID8E:< 8>8@EJK K?< J@E>C< LJ< F= K?<J<

JPJK<DJ N?@:? I<HL@I<; CFE><I K@D<J .?@J 9<?8M@FI N8J :FEE<:K<; N@K?

K?< ?FDFCPJ@J F= 8:K@M< :?CFI@E< JG<:@<J <> ")C )C− <C<:KIF><E

<I8K<; FE K?< <C<:KIF:8K8CPJK 8E; =I8>D<EK<; 9P K?< /0  ED I8;@

8K@FE C<8;@E> KF K?< GIF;L:K@FE F= ?@>?CP I<8:K@M< I8;@:8CJ 

   8J 8::FLEK<; =FI @F;FD<KIP OG<I@D<EKJ <O:CLJ@M<CP :8I

I@<; FLK N@K? K?< /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ KF <M8CL8K< K?<

@EaL<E:< F= :LII<EK ;<EJ@KP  8E;  D :D 8E; @E@K@8C G" M8C

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

UNCORRECTED PROOF

&(C,@!059,:(2 5;84(25-4<08543,4:(2/,30*(24.04,,804. >>> >>>> >>>>>>

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GFJ<; =FI K?< ?FDFCPJ@J F= 8:K@M< :?CFI@E< JG<:@<J ;<G<E;@E> FE K?<

G" N?@C< K?< ;<>I8;8K@FE G8K?N8P F= #* N8J I8K@FE8C@Q<; LJ@E> "*&

8E8CPJ<J ;LI@E>  D@E F= <C<:KIFCPJ@J JL>><JK@E> K?8K =FID@: 8E; FO8C@:

8:@;J N<I< =FID<; 8J `E8C 9PGIF;L:KJ I<>8I;C<JJ F= K?< @E@K@8C G" .?<

GIF>I<JJ@M< I<;L:K@FE F= .) D<8JLI<D<EKJ JL>><JK<; K?8K K?< :FD

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K@FE K@D<

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F= 8:K@M< :?CFI@E< :FLC; :FEKIFC K?< /08JJ@JK<; <C<:KIF:?<D@:8C GIF:<JJ

FN@E> KF K?< =8:K K?8K K?< KLE@E> F= @KJ :8K8CPK@: 8:K@M@KP @< :FEKIFCC<;

JPEK?<J@J F= 8 .@.@),L)8EF;< 8J ?<I<@E GIFGFJ<; :8E G<I=FID K?<

=8JK ;<>I8;8K@FE F= 8 I<:8C:@KI8EK :FDGFLE; <M<E LJ@E> 8 C8DG N@K? 8

:FEJ@;<I89CP CFN<FD<KI@: 8I<8 F= <C<:

KIF;<  I<8:KFI MFCLD< 8E; J?FIK8@EJK FK?<I JKL;

@<J @E K?< C@K<I8KLI< FEJ<HL<EKCP =LKLI< JKL;@<J N@CC 9< ;<MFK<; KF <O

GCFI< FK? K?< :8K8CPK@: GIF;L:K@FE F= 8:K@M<

:?CFI@E< N@K? M8I@<; aL<E:P I8K<J 8E; N8M<C<E>K?J

CRediT authorship contribution statement

Angel E. Yañez-Rios: #EM<JK@>8K@FE 8K8 :LI8K@FE Edgar Car-

rera-Crespo: #EM<JK@>8K@FE 8K8 :LI8K@FE Rosa M. Luna-Sanchez:

'<K?F;FCF>P -LG<IM@J@FE LE;@E> 8:HL@J@K@FE Ricardo E.

Palma-Goyes: FE:<GKL8C@Q8K@FE 1I@K@E>  FI@>@E8C ;I8=K Jorge

Vazquez-Arenas: LE;@E> 8:HL@J@K@FE 1I@K@E>  FI@>@E8C ;I8=K 1I@K@E>

 I<M@<N  <;@K@E> *IFA<:K 8;D@E@JKI8K@FE

CRediT authorship contribution statement

Angel E. Yañez-Rios: #EM<JK@>8K@FE 8K8 :LI8K@FE $L8E Edgar Car-

rera-Crespo: #EM<JK@>8K@FE 8K8 :LI8K@FE Rosa M. Luna-Sanchez:

'<K?F;FCF>P -LG<IM@J@FE LE;@E> 8:HL@J@K@FE Ricardo E.

Palma-Goyes: FE:<GKL8C@Q8K@FE 1I@K@E>  FI@>@E8C ;I8=K Jorge

Vazquez-Arenas: LE;@E> 8:HL@J@K@FE 1I@K@E>  FI@>@E8C ;I8=K 1I@K@E>

 I<M@<N  <;@K@E> *IFA<:K 8;D@E@JKI8K@FE

Declaration of Competing Interest

.?< 8LK?FIJ I<GFIK EF ;<:C8I8K@FEJ F= @EK<I<JK

Acknowledgments

E><C  38W<Q,@FJ 8E; $L8E  8II<I8I<JGF K?8EB )(3.

=FI K?< <:FEFD@: JLGGFIK KF GLIJL< D8JK<I 8E; GFJK;F:KFI8C JKL;@<J I<

JG<:K@M<CP @E8E:@8C JLGGFIK N8J GIFM@;<; 9P -.#'2'2#)

>I8EK : -.# -#*#*( >I8EK EF  8E; @<E

:@8 8eJ@:8 )(3.  >I8EK EF - .?< 8LK?FIJ 8:BEFNC

<;>< K?< 8JJ@JK8E:< F= I $FI>< & CFI<J 'FI<EF /' KF :FE;L:K

K?< 2, D<8JLI<D<EKJ

Appendix A. Supplementary data

-LGGC<D<EK8IP D8K<I@8C I<C8K<; KF K?@J 8IK@:C< :8E 9< =FLE; @E K?<

FEC@E< M<IJ@FE 8K ;F@?KKGJ;F@FI>AA<:<

References

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K?< NFIC;’J C8I><JK LEKI<8K<; N8JK<N8K8K@FE JPJK<D '<QHL@K8C 08CC<P

'<O@:F ?<DFJG?<I<   – ;F@

A:?<DFJG?<I<

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

Photo-assisted electrochemical degradation of ciprofloxacin using DSA® anode with NaCl electrolyte and simultaneous chlorine photolysis

Article

Jun 2022

This study aimed to investigate and improve the performance of the photo-assisted electrochemical process (PAEC) for the degradation of ciprofloxacin (CIP) and the production of active chlorine species (ACS), using a DSA® (Dimensionally stable anodes) electrode, NaCl as the supporting electrolyte and UV radiation provided by a high-pressure mercury lamp (UVC). The performance of the system was assessed by monitoring the CIP concentration, ACS, chemical oxygen demand (COD), total organic carbon (TOC), and phytotoxicity tests. The effect of operational parameters, such as current density, NaCl concentration, volumetric flow, and initial pH of the solution were evaluated. Under operating conditions of j = 60.7 mA/cm², [NaCl] = 0.3 mol/L, qv = 10 mL/min, and pH = 5, complete removal of CIP was achieved in 5 min and, with only 1 h of electrolysis, removal of approximately 60% TOC and 65% COD was obtained. The PAEC process promoted greater mineralization of the solution in relation to the isolated techniques and the phytotoxicity tests indicated that, despite the high salinity of the effluent (0.3 mol/L NaCl), the PAEC process (UVC 250 W) did not generate an increase in toxicity of the treated solution. The elucidated CIP degradation mechanism indicates that the piperazine group was the most attacked site of the molecule. Furthermore, the identified intermediates show that CIP was gradually destroyed, generating compounds with a lower risk of increasing bacterial resistance proliferation.

Decentralized approach toward organic pollutants removal using UV radiation in combination with H2O2-based electrochemical water technologies

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CHEMOSPHERE

Revealing the double-edged roles of chloride ions in Fered-Fenton treatment of industrial wastewater

Article

May 2023
SEP PURIF TECHNOL

Hybrid process of adsorption and electrochemically based green regeneration of bentonite clay for ofloxacin and ciprofloxacin removal

Article

Full-text available

Mar 2023
ENVIRON SCI POLLUT R

Removal of emerging contaminants, such as antibiotics, from wastewater by adsorption is a simple, low-cost, and high-performance process; however, regeneration and reuse of the exhausted adsorbent are necessary to make the process economically viable. This study aimed to investigate the possibility of electrochemical-based regeneration of clay-type materials. For this, the calcined Verde-lodo (CVL) clay was saturated with the antibiotics ofloxacin (OFL) and ciprofloxacin (CIP) in one-component systems by an adsorption process and then subjected to photo-assisted electrochemical oxidation (0.45 A, 0.05 mol/L NaCl, UV-254 nm, and 60 min), which promotes both pollutant degradation and adsorbent regeneration. The external surface of the CVL clay was investigated by X-ray photoelectron spectroscopy before and after the adsorption process. The influence of regeneration time was evaluated for the CVL clay/OFL and CVL clay/CIP systems, and the results demonstrate high regeneration efficiencies after 1 h of photo-assisted electrochemical oxidation. Clay stability during regeneration was investigated by four successive cycles in different aqueous matrices (ultrapure water, synthetic urine, and river water). The results indicated that the CVL clay is relatively stable under the photo-assisted electrochemical regeneration process. Furthermore, CVL clay was able to remove antibiotics even in the presence of natural interfering agents. The hybrid adsorption/oxidation process applied here demonstrated the electrochemical-based regeneration potential of CVL clay for the treatment of emerging contaminants, since it can be operated quickly (1h of treatment) and with lower consumption of energy (3.93 kWh kg−1) than the traditional method of thermal regeneration (10 kWh kg−1).

Electro-oxidation of Quinoline Simulated Wastewater Containing Chloride in a Swirling Flow Reactor: Influence Factors, Kinetics, Biotoxicity, and Energy Consumption

Article

Full-text available

Sep 2022
INT J ELECTROCHEM SC

In this research, we used a swirling flow reactor to remove quinoline from aqueous solutions containing chloride using electro-oxidation (EO). We evaluated the effect of several operational variables, including current density, initial pH, Cl- concentration, and initial quinoline concentration, on EO effectiveness. Our results revealed a maximum total organic carbon (TOC) removal efficiency of 68.0% at a current density of 40 mA/cm2 , Cl- concentration of 2000 mg/L, and initial quinoline concentration of 250 mg/L. Of the variables tested, current density had the largest effect on TOC abatement. Kinetic analysis showed that quinoline abatement followed pseudo-first-order kinetics and was limited by charge transfer. The biotoxicity of quinoline simulated wastewater increased and then decreased during EO. Energy consumption and mineralization current efficiency during 90 min of electrolysis in the swirling flow reactor were 1.67 kWh/gTOC and 8.1%, respectively, indicating superior performance compared to the parallel plate reactor. This paper provides information on developing electrochemical reactors and their application to reduce the organic load of saline wastewater.

MnO2-RuO2/CFC composite electrode used in the treatment of high‑chlorine organic wastewater: Preparation, performance, mechanism and application feasibility

Article

Jan 2024

Research on the reaction path of chlorobenzene oxidation by electrochemical-sodium persulfate system

Article

Aug 2023
J CLEAN PROD

Tween 80 assisted washing ciprofloxacin-contaminated soil, and recycled it using active chlorines

Article

May 2023

Active chlorines (ACs) can selectively oxidize contaminants with benzene rings to recycle surfactants, which greatly facilitates the resource cycle. This paper firstly utilized Tween 80 to assist in ex-situ washing the ciprofloxacin (CI) contaminated soil, including the solubilization experiment, shake washing and soil column washing, all of which showed that 2 g/L of Tween 80 (TW 80) was the most effective in removing CI. Then electrochemically treated the collected soil washing effluent (SWE) at 10 V with an electrolyte of 20 mM NaCl + 10 mM Na2SO4; Pre-experiments screened the range of electrode spacing, pH and temperature, based on which an orthogonal design Table L9 (34) was designed. Visual analysis and ANOVA were performed on the ciprofloxacin removal efficiency and Tween 80 retention efficiency during the orthogonal experiments in 9 groups, and the results showed that CI was usually degraded within 30 min, and 50% of TW 80 was still present at the end of the experiment, and there was no significant effect of all three factors. LC-MS demonstrated that CI was mainly degraded synergistically by ·OH and ACs, and ·OH effectively reduced the biotoxicity of the SWE, so the mixed electrolyte may be more suitable for the electrochemical recycling system of ACs. This paper conducted the washing remediation study of CI-contaminated soil for the first time, and applied the theory of selective oxidation by ACs on benzene ring to treat the SWE, which provides a new treatment idea for antibiotic-contaminated soil.

Degradation of antibiotics by electrochemical advanced oxidation processes (EAOPs): Performance, mechanisms, and perspectives

Article

Sep 2022
SCI TOTAL ENVIRON

Global consumption and discharge of antibiotics have led to the rapid development and spread of bacterial antibiotic resistance. Among treatment strategies, electrochemical advanced oxidation processes (EAOPs) are gaining popularity for treating water/wastewater containing antibiotics due to their high efficiency and easiness of operation. In this review, we summarize various forms of EAOPs that contribute to antibiotic degradation, including common electrochemical oxidation (EO), electrolyte enhanced EO, electro-Fenton (EF) processes, EF-like process, and EAOPs coupling with other processes. Then we assess the performance of various EAOPs in antibiotic degradation and discuss the influence of key factors, including electrode, initial concentration and type of antibiotic, operation conditions, electrolyte, and water quality. We also review mechanisms and degradation pathways of various antibiotics degradation by EAOPs, and address the species and toxicity of intermediates produced during antibiotics treatment. Finally, we highlight challenges and critical research needs to facilitate the application of EAOPs in antibiotic treatment.

Enhanced solar photo-electro-Fenton by Theobroma grandiflorum addition during pharmaceuticals elimination in municipal wastewater: Action routes, process improvement, and biodegradability of the treated water

Article

Mar 2022

This work shows, for the first time, the use of the autochthonous Amazonian fruit copoazu (COPE, Theobroma grandiflorum) as an enhancer of the solar photoelectroFenton (SPEF) performance. SPEF, using a BDD anode with Na2SO4 or IrO2 anode in NaCl and actual sunlight, was applied to degrade four representative pharmaceuticals (acetaminophen, diclofenac, ciprofloxacin, and sulfamethoxazole) simultaneously in raw municipal wastewater (MWW). The effect of COPE addition on both pharmaceuticals degradation and keeping iron in solution at near-neutral pH is presented. Also, the combination of the enhanced SPEF process with an aerobic biological system was evaluated. In the SPEF process based on IrO2-NaCl, electrogenerated reactive chlorine species played the main degrading role. Meanwhile, in the BDD-based process, hydroxyl radical and photolysis were the main agents responsible for the elimination of pharmaceuticals. The two SPEF processes, IrO2-NaCl and BDD-Na2SO4, led to ~99 and ~49% of pondered degradation of pharmaceuticals, respectively. The addition of an extract of copoazu to the reactor equipped with the BDD anode improved the elimination, achieving ~70% of pondered removal of the pharmaceuticals. COPE acted as a natural complexing agent, favoring the catalytic cycle of iron in the system. Finally, the biodegradability (using aerobic microorganisms) of the MWW treated by the improved SPEF (with the BDD anode) was tested. It was found that the microorganisms were able to remove up to 54.6% of the organic carbon content in the sample, indicating the high biocompatibility of water resultant from the treatment by the SPEF improved with the copoazu presence.

Revisiting Tractable Strategies to Determine the Activity/Inactivity of Electrocatalysts towards O 2 / • OH Production

Article

Full-text available

Sep 2018
J ELECTROCHEM SOC

The measurement of the electroactivity of anode materials toward the generation of hydroxyl radicals or oxygen evolution from water oxidation is overriding to develop novel catalysts with tuned electrocatalytic applications. Thus, this work experimentally revisits chemical and electrochemical characterization techniques with the aims of establishing a comparison of the electrochemical performance of typical IrO2, RuO2, SnO2-Sb, and Boron doped diamond (BDD) electrodes toward H2O oxidation under feasible experimental conditions, and highlighting those conditions where variability cannot be removed. Tafel slopes corrected for ohmic resistance and active areas are 127, 175, 42, 48 mV dec⁻¹ for BDD, SnO2-Sb, IrO2 and RuO2, respectively; while in the same order, the onset potential for water oxidation is: 2.49, 2.29, 1.47, 1.38 V vs SHE, measured at a current density of 0.5 mA cm⁻². Additionally, a new interpretation is presented for the analysis of electrochemical impedance spectroscopy (EIS), and its connection with the OER mechanism: in the potential zone where Tafel is applicable is possible to appreciate the dielectric properties of the substrate for non-active anodes and elucidating the variation in the rate-determining step of water oxidation. EIS results suggest the possibility to use the time-constant associated with this stage as a parameter of the active or non-active behavior of the above electrodes. The advantages and drawbacks of different trapping molecules used to detect the •OH generation in electrocatalysis is discussed. The photoluminescence of coumarin could be used as a fast and reliable method for the evaluation of the electrocatalyst activity toward the •OH production.

Implications to enhance Sulfamethoxazole degradation using statistical optimization of either active chlorine concentration or ORP in an electrochemical reactor

Article

Jun 2020

A filter-press FM01-LC reactor electro-generating active chlorine on a synthesized Ti/RuO2-ZrO2-Sb2O3 anode is evaluated to account for whether the optimization of the active chlorine concentration, or the oxidation-reduction potential (ORP) in solution is the most important variable during the elimination of 20 mg L⁻¹ sulfamethoxazole (SMX). The three most important factors affecting the reactor performance (chloride concentration, current density and volumetric flow) are used in wide ranges via a Box–Behnken design (BBD) of experiments in the absence of SMX (4 h): 0.01 to 0.2 mol L⁻¹ NaCl, 10 to 250 A m⁻² and 1 to 5 L min⁻¹. An initial pH of 5.8 is utilized due to the HOCl predominance, presenting the most oxidizing potential among chlorine species. Higher chlorine concentrations are produced at higher NaCl contents (i.e. 0.2 mol L⁻¹ NaCl). Volumetric flows around 3.87 L min⁻¹ should be enough to furnish chloride ions to the anode surface by convection. The current density strongly depending on pH is the decisive parameter to either maximize the chlorine concentration or the ORP. A higher active chlorine production at 250 A m⁻² eliminates the pollutant before 5 min, and a lower amount of intermediates remain after 90 min of electrolysis; since this condition effectively acts against the reducing character of SMX. The ORP optimization cannot overcome this reducing environment due to a lower amount of chlorine species produced at 10 A m⁻², whereby traces of this contaminant and more intermediates are detected after the treatment.

Generation and application of reactive chlorine species by electrochemical process combined with UV irradiation: Synergistic mechanism for enhanced degradation performance

Article

Jan 2020
SCI TOTAL ENVIRON

Saline wastewater originates from many industries, containing a large amount of salt (NaCl) and other toxic and harmful organic matter, which have a great impact on the soil and groundwater. However, the treatment of saline wastewater is a serious problem because organic contents are hard to degrade with the high salinity by the common water treatment technologies. Herein, an electrochemical process coupled with ultraviolet (UV) irradiation was proposed for the saline wastewater treatment. High efficiency of p-nitrophenol (p-NP) and ammonia degradation were contributed from the in situ electrochemical produced active chlorine and photo-induced chlorine radicals. Under the optimal conditions (0.10 A, 0.05 M NaCl, and pH 6.00), approximately 98.91% p-NP was removed after 60 min with the rate constant of 7.521 × 10-2 min-1 in the electrochemical process, and 28.99% mineralization rate was obtained, while with the synergistic effect of UV and electrochemistry, approximately 100% of p-NP removal (k = 9.331 × 10-2 min-1) was achieved by 30 min treatment and about 83.70% of p-NP can be mineralized to CO2 after 60 min. The study on the synergistic mechanism of enhanced degradation performance illustrated that Cl with high oxidation capacity played an important role in the p-NP oxidation. Besides, based on the chlorine radical reactions, this method was also effectively applied to remove ammonia nitrogen (92.00% removal of total nitrogen in 100 min) for nitrogen-containing wastewater. Thus, this study offers a promising approach for the treatment of saline industry wastewater.

Comparison of UVC-based advanced oxidation processes in the mineralization of bisphenol A: Identification of oxidation by products and toxicity evaluation

Article

Dec 2019
CHEM ENG J

Water contamination by contaminants of emerging concern (CEC) represents a major challenge to our society regarding the need to assure a high quality drinking water to prevent humans from developing health problems. Thus, the performance of three different advanced oxidation processes (AOP: UVC/HOCl, UVC/S2O8²⁻, and UVC/H2O2) based on the homolysis of oxidants were investigated for the oxidation and mineralization of bisphenol A (BPA) containing solutions as well as assessment of biotoxicity and identification of oxidation by-products. In all AOP, UVC irradiation led to a significant improvement for the oxidation and mineralization of BPA due to the production of HO•/SO4•⁻ species. UVC/HOCl method was able to achieve high rates of conversion of BPA and its oxidation by-products to CO2. All detected oxidation by-products resulted from hydroxylation reactions. Considering the short chain carboxylic acids, mainly produced after opening the aromatic ring, high concentrations appeared mainly during the first two hours of treatment for the UVC/HOCl method with a complete elimination within 6 h of treatment, including the dichloroacetic acid. Biotoxicity assays using Artemia salina crustacean showed that the mortality was ceased after 4 h of treatment using the UVC/HOCl and UVC/S2O8²⁻ processes. In contrast, a low mortality decrease was observed when using the UVC/H2O2 process, probably due to the accumulation of toxic intermediates. In all scenarios, toxicity of the BPA compound and its oxidation by-products seem to be responsible for the distinct decays of mortality, as confirmed on the ECOSAR software. Finally, the UVC/HOCl method is an interesting option to eliminate CEC for removing levels attained and energy consumption.

Assessing the performance of electrochemical oxidation using DSA and BDD anodes in the presence of UVC light

Article

Aug 2019
CHEMOSPHERE

Significance of surface and ground water contamination by synthetic organic compounds has been pointed out in a very high number of papers worldwide, as well as the need of application of treatment technologies capable to assure their complete removal. Among these processes, the electrochemical advanced oxidation is an interesting option, especially when irradiated with UVC light (photo-electrochemical, P-EC) to promote homolysis of electrogenerated oxidants. In this work, the herbicide glyphosate (GLP) was used as model compound and it was electrochemically treated under UVC irradiation in the presence of NaCl and using a DSA® and BDD anodes. Total organic carbon concentration was measured throughout the electrolysis, as well as the concentration of short chain carboxylic acids and inorganic ions (NO3-, PO43-,ClO-, ClO3- and ClO4-). The synergism of the P-EC was more pronounced when using a DSA® electrode, which led to complete GLP mineralization in 1 h (0.52 A h L-1), as also confirmed by the stoichiometric formation of NO3- and PO43- ions, with an energy consumption as low as 1.25 kW h g-1. Unexpectedly, the concentration evolution of oxyhalides for the P-EC process using both anodes, especially for DSA® at 10 mA cm-2, showed the production of ClO3-, whereas detection of ClO4- species was only found when using BDD at 100 mA cm-2 for the electrochemical process. Finally, small amounts of carboxylic acids were detected, including dichloroacetic acid, especially when using a BDD electrode.

Bench-scale reactor for Cefadroxil oxidation and elimination of its antibiotic activity using electro-generated active chlorine

Article

May 2019

The Cefadroxil (CFDX) degradation and its associated antibiotic activity (AA) are analyzed on Sb2O3 doped Ti/RuO2-ZrO2 anodes electro-generating active chlorine (Cl2-active). The influence of the following parameters: (i) current density (ii) CFDX concentration (iii) volumetric flow and (iv) initial pH is evaluated in a filter-press FM01-LC reactor to account for controlling factors of the system. The CFDX removal is improved when HClO predominate in solution due to its higher oxidation potential, co-assisted with the presence of Cl2 (pH = 2), while the CFDX molecule undergoes a slight acid hydrolysis. The contaminant destruction is controlled by the kinetics arising between the active chlorine species adsorbed on the electrode surface (HClOads) and the pollutant, since the increase of flow rate in the reactor does not improve the abatement whatsoever. The total CFDX concentration and its antibiotic activity can be eliminated after 15 min using electro-generated active chlorine at the following operating conditions: 0.05 mol L⁻¹ NaCl, natural pH (5.5), 3 mA cm⁻² and 4 L min⁻¹. The energy consumption is considerably influenced by the cell voltage and the presence of active chlorine and H⁺ concentrations. An important biodegradability degree of the final byproducts is produced by active chlorine species, while only two intermediates of cefadroxil oxidation (CFDX-I-1 and CFDX-I-2) are detected after 2 h of treatment using high-performance liquid chromatography (HPLC).

Electrogeneration of inorganic chloramines on boron-doped diamond anodes during electrochemical oxidation of ammonium chloride, urea and synthetic urine matrix

Article

May 2019
WATER RES

Ubiquitous presence of chloride in water effluents may result in the unavoidable electrogeneration of active chlorine species when considering the application of electrochemical advanced oxidation processes as water treatment technologies. However, less attention has been drawn to the subsequent generation of other combined chlorine species such as chloramines. In this work, the electrogeneration of chloramines has been assessed in different water matrices containing NHCl4, urea or synthetic urine. The yield of chloramines has been followed in-situ by differential electrochemistry mass spectroscopy (DEMS) during electrochemical advanced oxidation process with boron-doped diamond (BDD) anodes. Furthermore, the influence of several variables such as chloride concentration, pH or organics concentration on the different distribution of inorganic monochloramine, dichloramine and trichloramine released as products has been considered.

Efficient cephalexin degradation using active chlorine produced on ruthenium and iridium oxide anodes: Role of bath composition, analysis of degradation pathways and degradation extent

Article

Aug 2018
SCI TOTAL ENVIRON

The elimination of cephalexin (CPX) using electro-generated Cl2-active on Ti/RuO2-IrO2 anode was assessed in different effluents: deionized water (DW), municipal wastewater (MWW) and urine. Single Ti/RuO2 and Ti/IrO2 catalysts were prepared to compare their morphologies and electrochemical behavior against the binary DSA. XRD and profile refinement suggest that Ti/RuO2-IrO2 forms a solid solution, where RuO2 and IrO2 growths are oriented by the TiO2 substrate through substitution of Ir by Ru atoms within its rutile-type structure. SEM reveals mud-cracked structures with flat areas for all catalysts, while EDS analysis indicates atomic ratios in the range of the oxide stoichiometries in the nominal concentrations used during synthesis. A considerably higher CPX degradation is achieved in the presence of NaCl than in Na2SO4 or Na3PO4 media due to the active chlorine generation. A faster CPX degradation is reached when the current density is increased or the pH value is lowered. This last behavior may be ascribed to an acid-catalyzed reaction between HClO and CPX. Degradation rates of 22.5, 3.96, and 0.576 μmolL−1min−1 were observed for DW,MWW and urine, respectively. The lower efficiency measured in these last two effluents was related to the presence of organic matter and urea in the matrix. A degradation pathway is proposed based on HPLC-DAD and HPLC-MS analysis, indicating the fast formation (5 min) of CPX-(S)-sulfoxide and CPX-(R)-sulfoxide, generated due the Cl2-active attack at the CPX thioether. Furthermore, antimicrobial activity elimination of the treated solution is reached once CPX, and the initial by-products are considerably eliminated. Finally, even if only 16% of initial TOC is removed, BOD5 tests prove the ability of electro-generated Cl2-active to transform the antibiotic into biodegradable compounds. A similar strategy can be used for the abatement of other recalcitrant compounds contained in real water matrices such as urine and municipal wastewaters.

In search of the active chlorine species on Ti/ZrO2-RuO2-Sb2O3 anodes using DEMS and XPS

Article

Apr 2018
ELECTROCHIM ACTA

Evidence to what it is identified in the literature as “active chlorine” in indirect oxidation processes occurring on Ti/ZrO2-RuO2-Sb2O3 anodes is provided in this study. To discriminate such behavior, different catalysts are prepared using the Pechini method varying ZrO2 content, at different Zr/Ru molar ratios: 1, 0.5 and 0.3. The characterization of the materials using X-ray photoelectron spectroscopy (XPS) reveals that no solid solution (Ru-Zr) or any doping that affects the crystalline phase of Zr are obtained, while Sb2O3 was surface-segregated from the bulk to the anode surface affecting the outmost 3–5nm surface layers. There are enormous impacts on the catalytic activity and adsorption properties of the structures as ZrO2 content is increased. The presence of ZrO2 and Sb2O3 shrink the number of favorable oxygen adsorption sites in Ti/ZrO2-RuO2-Sb2O3 catalysts, whence the adsorption energies for oxygen-metal interactions became lower than for Ti/RuO2. Differential electrochemical mass spectroscopy (DEMS) and electrochemical experiments qualitatively indicate that a lower amount of ZrO2 in the ternary electrode induce a better catalysis towards the oxygen evolution reaction (OER, O2 production), while the ionic currents for ClO − and HClO species drop. This behavior suggests that chloride oxidation needs to encompass the mitigation of the OER as the percentage of ZrO2 is increased in the anode. Active chlorine could stem from HClOads species since it was produced in larger amounts than according to the pH of the electrolyte, and in adequate levels to generate the degradation of organic compounds.

The effect of different operational parameters on the electrooxidation of Indigo Carmine on Ti/IrO2-SnO2-Sb2O3

Article

Apr 2018

The electrochemical oxidation of indigo carmine (IC) is evaluated on a Dimensionally Stable Anode (DSA) made up of Sb⁠2O⁠3 doped Ti/IrO⁠2-SnO⁠2 (Ir-Sn-Sb). Particular efforts are devoted to investigate different electrochemical parameters including current density, IC concentration, initial pH of the solution, and the content of multiple ions (Cl⁠−, SO⁠4⁠−2 or HCO⁠3⁠−) typically found in textile dyeing wastewater. The IC removal efficiency is calculated using the following physicochemical parameters: color removal (611nm), Chemical Oxygen Demand (CODmgL⁠−1 O⁠2), Total Organic Carbon (TOCmgL⁠−1C) and Average Oxidation State (AOS). The results reveal that IC oxidation is enhanced in the presence of chlorides due to the action of active chlorine species (Cl⁠2-active) electrogenerated on the anode surface. In this medium, the initial oxidation rate of IC was higher at pH 2 than any other value including natural pH of 6.62 and 10. Both the increase of the chloride concentration in the electrolyte and the rise of current density expedite the color removal with a lower energetic consumption. Optimum treatment conditions were found using 0.25molL⁠−1 NaCl at pH 2 and applying 9.375mAcm⁠−2. Under these conditions, a total color removal is achieved, along with 77.5% COD, 24% TOC and the rise of AOS value to 2.9. High performance liquid chromatography analysis and mass spectrometry provide insights concerning the first degradation stages, involving the attacks of electrogenerated HClO in the double bond C C chromophore group of IC, thus, generating isatin-5-sulfonic acid (m/z 226) as the main reaction intermediate. This compound is subsequently removed to form aliphatic byproducts. COD removal and the final AOS value suggest that the electrochemical process transforms the IC to biodegradable intermediates, which can be eventually eliminated in a subsequent biological treatment.

The influence of pH and current density on an UV254 photo-assisted electrochemical process generating active chlorine and radicals for efficient and rapid ciprofloxacin mineralization compared to individual techniques

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