Open Journal of Applied Sciences, 2012, 2, 216-223
doi:10.4236/ojapps.2012.24032 Published Online December 2012 (http://www.SciRP.org/journal/ojapps)
Modeling Experimental Design for Photo-Fenton
Degradation of Methomyl
Abdelhadi Abaamrane
1,2*
, Samir Qourzal
2
, Saïd Mançour Billah
1
, Ali Assabbane
2
, Yhya Ait-Ichou
2
1
Laboratoire de Génie des Procédés, Département de Chimie, Faculté des Sciences,
Université Ibn Zohr, Agadir, Morocco
2
Equipe de Matériaux, Photocatalyse et Environnement, Département de Chimie, Faculté des Sciences,
Université Ibn Zohr, Agadir, Morocco
Email:
*
abd.abaamrane@yahoo.fr
Received August 27, 2012; revised September 30, 2012; accepted October 10, 2012
ABSTRACT
Modeling experimental design was used to study the main effects and the interaction effects between operational pa-
rameters in the photocatalytic degradation of pesticide methomyl. The important parameters which affect the removal
efficiency of methomyl such as concentration of Fe(NO
3
)
3
, concentration of H
2
O
2
, initial concentration of the pesticide
and pH. The parameters were coded as x
1
, x
2
, x
3
and x
4
, consecutively, and were investigated at two levels (–1 and +1).
The effects of individual variables and their interaction effects for dependent variables, namely, photocatalytic degrada-
tion efficiency (%) were determined. From the statistical analysis, the most effective parameters in the photocatalytic
degradation efficiency were initial concentrations of the methomyl and Fe(NO
3
)
3
. The interaction between initial con-
centration of the pesticide and Fe(NO
3
)
3
was the most influencing interaction. The optimum conditions that were ob-
tained for the photocatalytic degradation of methomyl were: minimum quantity of contaminant: 6 × 10
–5
mol·L
–1
,
maximum quantity of Fe(NO
3
)
3
: 5 × 10
–4
mol·L
–1
, initial pH of the solution: 3 and maximum quantity H
2
O
2
: 10
–2
mol·L
–1
.
Keywords: Methomyl; Photocatalytic Degradation; Response Surface Methodology (RSM); Full Factorial Design
1. Introduction
Pesticides are commonly used worldwide to face the
need for increasing and improving agricultural produc-
tion [1,2]. The detection of pesticides in storm and waste-
water effluent is reported to be a major obstacle as re-
gards wide ranging acceptance of water recycling. Fur-
thermore, their variety, toxicity and persistence can di-
rectly impact the ecosystem and threaten humans through
contamination of drinking water supplies (surface and
ground water).
Methomyl is an oxime carbamate insecticide (Figure
1). It is produced by reacting S-methyl-N-hydroxylthio
acetamidate (MHTA) in methylene chloride with gaseous
methyl isocyanate at 30˚C - 35˚C. Methomyl is highly
soluble in water (57.9 g·L
−1
) [3]. It has a low sorption
affinity to soil and can therefore easily cause groundwa-
ter contamination in agricultural areas.
Methomyl is effective in two ways: 1) as a “contact
insecticide” because it kills target insects upon direct
contact; and 2) as a “systemic insecticide” because of its
capability to cause overall “systemic” poisoning in target
insects, after it is absorbed and transported throughout
the pests that feed on treated plants. This insecticide is
mainly used in Morocco on a wide range of tomato crops.
However, it has been classified as a very toxic and ha-
zardous pesticide [4].
Recently, chemical treatment methods, based on the
generation of hydroxyl radicals (OH
), known as Ad-
vanced Oxidation Processes (AOPs), due to their effi-
ciency in oxidizing a great variety of organic contami-
nants [5-9].
The Fenton treatments are the requirement of H
2
O
2
,
Fe
2+
salts and pH adjustment (mostly acidic). With the
additions of H
2
O
2
and Fe
2+
salts, highly reactive and un-
selective oxidants are produced as shown in Equation (1)
that leads to the formation of less powerful hydroperoxyl
Figure 1. Chemical structure of methomyl.
*
Corresponding author.
Copyright © 2012 SciRes. OJAppS