4Diuron abatement in contaminated soil using Fenton-like process

Chemical Engineering Journal 183 (2012) 357–364

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Chemical Engineering

Journal

j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /c e

j

Diuron abatement in contaminated soil using Fenton-like process

Fernando Vicente ∗,Aurora Santos,Elena G.Sagüillo,Ángel M.Martínez-Villacorta,Juana María Rosas,Arturo Romero

Dpto Ingenieria Quimica,Facultad de Ciencias Químicas,Universidad Complutense Madrid,Ciudad Universitaria S/N,28040Madrid,Spain

a r t i c l e

i n f o

Article history:

Received 2September 2011Received in revised form 22December 2011

Accepted 3January 2012

Keywords:Citrate Diuron

Fenton-like

Soil remediation

a b s t r a c t

The use of catalyzed H 2O 2propagations (CHP)by the Fenton-like process has been evaluated for the treatment of contaminated soil by diuron ((q Diuron )o =40mg kg −1)at natural neutral pH.The interaction of H 2O 2with the soil in batch system has been previously studied at four different initial H 2O 2concen-tration (20,000–40,000–60,000–120,000mg kg −1)at room temperature in order to evaluate the oxidant decomposition by the natural reductants species (soil organic matter and iron minerals).

The oxidation of diuron using only H 2O 2at an initial concentration of 60,000mg kg −1was firstly determined (X Diuron =55%).Another test was developed to study the effect of the addition of citrate (C Citrate =3000mg kg −1)as a chelating agent to increase the removal of the contaminant up to 73%sug-gesting that the concentration of iron mobilized by citrate from the soil (C Fe ≈40mg kg −1)promotes the Fenton’s reaction.Finally,a third experiment was assessed using an extra amount of iron salt

(C Fe 3+=600mg kg −1

)in addition to citrate,resulting to an increase in the diuron removal (X Diuron >80%)because citrate makes stable iron chelates with Fe 3+and increases the generation of OH •in aqueous phase and a higher diuron removal is obtained.

Ecotoxicity measurements in the soil and liquid phases at initial and after the Fenton’s treatment by the Microtox ®bioassay demonstrated that low toxicity is obtained in the treated soil and temporal toxicity values in the liquid phase is in direct correlation with the residual H 2O 2.The toxicity values decrease with the H 2O 2concentration to not toxic values with a final total degradation of the oxidant.

© 2012 Elsevier B.V. All rights reserved.

1.Introduction

Herbicides are the most extensively type of pesticides used in agriculture.Due to their limited biodegradability,high vapour pres-sure and high lipid affinity,haloaromatic herbicides are considered a persistent class of chemicals [1].Diuron is one of these herbicides which has been frequently used in vineyards and it has been found in natural water at concentrations exceeding the regulatory limit of 0.1␮g L −1[2].It is considered a priority hazardous substance by the European Commission.The dispersion of this compound in agriculture leads to pollution of the aquatic environment by soil leaching [3].Because of its toxicity for aquatic organisms and sus-picion of being carcinogenic for humans,diuron is the object of growing environmental concern [4].

Agricultural use of herbicides results in relatively low soil con-tamination (diffuse contamination).In addition,near production

∗Corresponding author.Tel.:+34913944171;fax:+34913944171.

E-mail addresses:fervicen@quim.ucm.es (F.Vicente),aursan@quim.ucm.es (A.Santos),egsaguillo@quim.ucm.es (E.G.Sagüillo),angelmma@pas.ucm.es (Á.M.Martínez-Villacorta),jmrosas@quim.ucm.es (J.M.Rosas),aromeros@quim.ucm.es (A.Romero).

or storage of these herbicides may cause episodes of concentrated contaminated soil caused by spillage during pesticide mixing,load-ing and rinsing operations or direct dumplign into soil disposal sites.These practices are though to be responsible for approxi-mately 45%of cases of ground water contamination [5].

In situ chemical oxidation (ISCO)seems to be a viable technology for remediation of pesticides.In this technique a strong chemi-cal oxidant is injected into the contaminated surface to destroy the targeted contaminants [6].The oxidants frequently used are hydrogen peroxide (H 2O 2),permanganate (MnO 4−),persulphate (S 2O 82−)and ozone (O 3)[6–14].Each of these oxidants have limi-tations,(e.g.,persistence,reactivity,etc.)within a soil matrix.

H 2O 2has long been used in industrial applications and in water treatment processes.It is particularly effective when it is applied in combination with a catalyst such as ferrous iron (Fe 2+)to produce Fenton’s reagent.The reaction chemistry is complex,but poten-tially capable of degrading a wide range of organic contaminants depending on conditions [15].The following reactions may occur:

H 2O 2+Fe 2+→Fe 3++OH −+HO •

(1)Fe 3++H 2O 2→Fe 2++H ++HO 2•

(2)Fe 3++HO 2•→Fe 2++O 2+H +

(3)

1385-8947/$–see front matter © 2012 Elsevier B.V. All rights reserved.doi:10.1016/j.cej.2012.01.010