Bull. Mater. Sci. © Indian Academy of Sciences
DOI 10.1007/s12034-017-1448-3
Facile fabrication of organobentonite–carboxymethyl chitosan
hybrid film that absorbs organophosphate insecticides
DAU HUNG ANH1 and KANCHANA DUMRI2,∗
1 Biogreen Material Research and Service Co. Ltd., Chiang Mai 50140, Thailand
2 Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
∗ Author for correspondence (, )
MS received 12 October 2016; accepted 25 January 2017
Abstract. Organophosphate (OP)-insecticide-absorbing hybrid film containing 10% (w/w) organobentonite and car-
boxymethyl chitosan (CMCh) was fabricated and tested. Bentonite clay was modified to organobentonite by two steps
modification with (1) NaCl and (2) plant alkaloid monovalent cation berberine. CMCh was synthesized from commercial
shrimp chitosan. Afterwards, organobentonite was immobilized into CMCh matrix via in situ polymerization of CMCh to
cast a hybrid film with 0.5 mm thickness. Scanning electron microscopy images of organobentonite powder and the film
revealed the porous material and layer-upon-layer structure, respectively, which is supposed to enhance the water perme-
ability of the film. Fourier transform infrared spectrometry analysis revealed similarly chemical characteristics of the CMCh
component in the film and synthesized CMCh polymer powder. The film was then investigated to remove four OP insecticides
including profenofos, chlorpyrifos, methyl parathion and dimethoate of 5 ppm concentration in spiked water samples via
batch filtration. High-pressure liquid chromatography analysis showed that the removal rates for profenofos, chlorpyrifos,
methyl parathion and dimethoate after seven batches were 42, 39, 24 and 20%, respectively. Hence, absorptivity of this
film for tested OP insecticides was demonstrated. Furthermore, the combination of organobentonite and natural chitosan is
promising for novel absorptive film material generation with regard to environmental clean-up study.
Keywords. Organobentonite; carboxymethyl chitosan; hybrid film; organophosphate insecticides; batch filtration.
1. Introduction candidate for bentonite modification, which is a major alka-
loid from Coscinium fenestratum. This plant is being used
Bentonite clay and carboxymethyl chitosan (CMCh) products to date as a traditionally pharmaceutical component in Asian
are now commercialized world-wide and studied variously for countries, e.g., Thailand, Vietnam and China [16]. The incor-
environmental application. Bentonite is a well-known mate- poration of berberine into different clays via cation exchange
rial for the development of environment clean-up techniques mechanism has been reported [14,17]. It resulted in the
by its absorptivity for diverse materials from heavy-metal expansion of the basal spacing in the clay structures, which
toxins, e.g., As (III), Cd (II), Cu (II, III), Ni (II) and Pb increased the absorptivity of the modified clay for the target
(II) [1–5], to agricultural herbicides and insecticides, e.g., pollutants [14,15]. CMCh, a water-soluble derivative polymer
atrazine, carbaryl, dichlovos, parathion, paraoxon [6–9], and from biological chitosan molecules with high water solubil-
hazardous polycyclic aromatic hydrocarbons, e.g. naphtha- ity, has found applications in pharmacy and cosmetics. The
lene, flouranthene, benzo[a]pyrene and benzo[a]anthracene hydrogel form of CMCh has biocompatibility and biodegrad-
[10,11]. For applications, bentonite can be chemically mod- ability properties, which have been applied for drug delivery
ified using a large selection of alkylammonium or qua- and wound healing [18,19]. CMCh also behaves as an antimi-
ternary ammonium cations, where these cations replace crobial and antioxidant agent and emulsion stabilizer, which
the interlaying inorganic cations in bentonite, e.g., Ca2+ makes it an applicable matrix for cosmetics.
and Na+ , to form organobentonite. For example, bentonite Interestingly, the combination of organobentonite or ben-
types modified by plant alkaloid berberine (5,6-dihydro-9,10- tonite and chitosan yields new absorptive material bio-
dimethoxybenzo[g]-1,3 benzodioxolo[5,6-a]quinolizinium), nanocomposites, which can absorb various industrial dyes
tetradecyltrimethyl ammonium bromide, dodecyltrimethy- and herbicides, e.g., cationic Rhodamine 6G, anionic Amido
lammonium bromide or hexadecyl trimethyl ammonium Black 10B or Bezactiv Orange V-3R and clopyralid, in
and phenyltrimethylammonium increasingly absorb pesti- wastewater treatment [20–24]. These materials have higher
cides malathion and butachlor, herbicides terbuthylazine and absorptive capacity for target absorbate than that of either
diuron and industrial dyeing wastewater [12–15]. Among organobentonite or chitosan [22,24]. The chitosan–bentonite
alkylammonium compounds, berberine is a selective nanocomposites also show antibacterial activity (both Gram
, D H Anh and K Dumri
positive, e.g., Bacillus subtilis and Staphylococcus aureus,
and Gram negative, e.g., Escherichia coli) as well as higher
tensile strength in comparison with chitosan moiety [25,26].
The organophosphate (OP) insecticides tested in this
work were chlorpyrifos, profenofos, dimethoate and methyl
parathion. They are classified into class II (moderately toxic)
and class IA (extremely toxic) for inhalation and ingestion
by WHO, respectively [27]. Agricultural-product-exporting
countries, e.g., Thailand, use these OP insecticides but the
control of use is always problematic; therefore, their residues
can be detected ubiquitously not only in harvested products
but also in nearby agricultural water zones or even in fresh
water sources due to rainfall event [28,29]. Towards this end,
we fabricated a film composed of berberine-modified ben-
tonite and synthesized CMCh. The film materials were tested
to remove the four aforementioned OP insecticides in spiked
water. The absorptivity of the film based on their structures
and the interactions between film components and OP insec-
Figure 1. Structures of berberine chloride and tested OP insecti-
ticides are described and discussed.
cides.
2. Experimental pipetted step-wise (100 µl in 10 s) into the Na-bentonite mix-
ture with vigorous stirring. Subsequently, the reaction mixture
2.1 Materials was stirred at 600 rpm for 8 h. The yellow sediment was
allowed to settle within 2 h, collected and dried at 95◦ C for
The commercial bentonite or calcium bentonite (designated as 12 h. The dried sediment was ground to powder and sieved
bentonite) was purchased from Srichand United Dispensary using a 300-mesh sieve (Gallenkamp and Co, London). The
Co., Ltd. (Bangkok, Thailand). Commercial grade shrimp chi- latter was used for all insecticides absorption tests through-
tosan of flake polymer type (molecular weight in the range out this work and it was designated as BBr-bentonite. Both
900–1,300 kDa) was purchased from Taming Enterprises Na-bentonite and BBr-bentonite are generally designated as
(Samutsakon, Thailand). modified bentonite in all following contexts.
All chemicals were of analytical grade. Berberine chlo-
ride (98%, designated as BBrCl) and OP insecticides (>97%, 2.3 Synthesis of CMCh
PESTANAL , including methyl parathion, chlorpyrifos, pro-
fenofos and dimethoate, were purchased from Sigma and CMCh was synthesized by the procedure of Chen and Park
Riedel de Haen (Germany) (figure 1). Stock solutions (100 [33]. The chitosan powder (25 g) was suspended in a solution
mM) of insecticides were prepared in methanol (MeOH) and of NaOH:i-propanol:H2 O (1:8:2) and stirred at room temper-
kept at 4◦ C until further use. Working insecticide solutions ature for 1 h. The appropriate amount of monochloroacetic
were prepared at 5 ppm in distilled water of pH 7.2. acid was added into the mixture and continuously stirred for
30 min. The mixture was covered with an aluminium foil and
2.2 Two steps modification of commercial bentonite by placed in an oven at 50◦ C for 4 h. Later, it was separated
NaCl and BBrCl into liquid and solid phases. The solid phase was further sus-
pended in MeOH and neutralized with glacial acetic acid.
In the first step, bentonite was modified by NaCl to form Na- Subsequently, it was filtered and washed 5 times with ethanol
bentonite; 100 g of bentonite was well dispersed in 1 litre (70% v/v EtOH) to remove undesirable products and the last
of NaCl (0.1 M, pH 7.5) and vigorously stirred at 600 rpm time with absolute MeOH. The final product, designated as
for 8 h at room temperature. Afterwards, the reaction mix- CMCh, was dried in the oven at 50◦ C for 18 h and kept in a
ture was allowed to settle for 2 h and the supernatant was sealed polyethylene bag until further use.
decanted. Later, the bentonite sediment was washed repeat-
edly 4–6 times by deionized water to eliminate the redundant 2.4 Casting of hybrid film containing organobentonite and
NaCl. Subsequently, NaCl residue in the supernatant was CMCh
tested using a Chloride Low Range Test Kit, Model 8-P, Hach
(USA). The bentonite sediment was dried at 95◦ C for 12 h Modified bentonite (2 g, BBr-bentonite and Na-bentonite)
and ground to powder afterwards. This was designated as was firstly added step-wise (50 mg in 10 s) into 500 ml distilled
Na-bentonite. In the second step, 30 g of Na-bentonite was water at 80◦ C under 500 rpm stirring in a 1-litre glass beaker
re-dispersed in 1 litre of deionized water and 10 ml homo- until a homogeneous grey suspension solution (Na/bentonite)
geneous BBrCl solution (0.3 g BBrCl in 10 ml MeOH) was or yellow suspension solution (BBr/bentonite) was formed.
DOI 10.1007/s12034-017-1448-3
Facile fabrication of organobentonite–carboxymethyl chitosan
hybrid film that absorbs organophosphate insecticides
DAU HUNG ANH1 and KANCHANA DUMRI2,∗
1 Biogreen Material Research and Service Co. Ltd., Chiang Mai 50140, Thailand
2 Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
∗ Author for correspondence (, )
MS received 12 October 2016; accepted 25 January 2017
Abstract. Organophosphate (OP)-insecticide-absorbing hybrid film containing 10% (w/w) organobentonite and car-
boxymethyl chitosan (CMCh) was fabricated and tested. Bentonite clay was modified to organobentonite by two steps
modification with (1) NaCl and (2) plant alkaloid monovalent cation berberine. CMCh was synthesized from commercial
shrimp chitosan. Afterwards, organobentonite was immobilized into CMCh matrix via in situ polymerization of CMCh to
cast a hybrid film with 0.5 mm thickness. Scanning electron microscopy images of organobentonite powder and the film
revealed the porous material and layer-upon-layer structure, respectively, which is supposed to enhance the water perme-
ability of the film. Fourier transform infrared spectrometry analysis revealed similarly chemical characteristics of the CMCh
component in the film and synthesized CMCh polymer powder. The film was then investigated to remove four OP insecticides
including profenofos, chlorpyrifos, methyl parathion and dimethoate of 5 ppm concentration in spiked water samples via
batch filtration. High-pressure liquid chromatography analysis showed that the removal rates for profenofos, chlorpyrifos,
methyl parathion and dimethoate after seven batches were 42, 39, 24 and 20%, respectively. Hence, absorptivity of this
film for tested OP insecticides was demonstrated. Furthermore, the combination of organobentonite and natural chitosan is
promising for novel absorptive film material generation with regard to environmental clean-up study.
Keywords. Organobentonite; carboxymethyl chitosan; hybrid film; organophosphate insecticides; batch filtration.
1. Introduction candidate for bentonite modification, which is a major alka-
loid from Coscinium fenestratum. This plant is being used
Bentonite clay and carboxymethyl chitosan (CMCh) products to date as a traditionally pharmaceutical component in Asian
are now commercialized world-wide and studied variously for countries, e.g., Thailand, Vietnam and China [16]. The incor-
environmental application. Bentonite is a well-known mate- poration of berberine into different clays via cation exchange
rial for the development of environment clean-up techniques mechanism has been reported [14,17]. It resulted in the
by its absorptivity for diverse materials from heavy-metal expansion of the basal spacing in the clay structures, which
toxins, e.g., As (III), Cd (II), Cu (II, III), Ni (II) and Pb increased the absorptivity of the modified clay for the target
(II) [1–5], to agricultural herbicides and insecticides, e.g., pollutants [14,15]. CMCh, a water-soluble derivative polymer
atrazine, carbaryl, dichlovos, parathion, paraoxon [6–9], and from biological chitosan molecules with high water solubil-
hazardous polycyclic aromatic hydrocarbons, e.g. naphtha- ity, has found applications in pharmacy and cosmetics. The
lene, flouranthene, benzo[a]pyrene and benzo[a]anthracene hydrogel form of CMCh has biocompatibility and biodegrad-
[10,11]. For applications, bentonite can be chemically mod- ability properties, which have been applied for drug delivery
ified using a large selection of alkylammonium or qua- and wound healing [18,19]. CMCh also behaves as an antimi-
ternary ammonium cations, where these cations replace crobial and antioxidant agent and emulsion stabilizer, which
the interlaying inorganic cations in bentonite, e.g., Ca2+ makes it an applicable matrix for cosmetics.
and Na+ , to form organobentonite. For example, bentonite Interestingly, the combination of organobentonite or ben-
types modified by plant alkaloid berberine (5,6-dihydro-9,10- tonite and chitosan yields new absorptive material bio-
dimethoxybenzo[g]-1,3 benzodioxolo[5,6-a]quinolizinium), nanocomposites, which can absorb various industrial dyes
tetradecyltrimethyl ammonium bromide, dodecyltrimethy- and herbicides, e.g., cationic Rhodamine 6G, anionic Amido
lammonium bromide or hexadecyl trimethyl ammonium Black 10B or Bezactiv Orange V-3R and clopyralid, in
and phenyltrimethylammonium increasingly absorb pesti- wastewater treatment [20–24]. These materials have higher
cides malathion and butachlor, herbicides terbuthylazine and absorptive capacity for target absorbate than that of either
diuron and industrial dyeing wastewater [12–15]. Among organobentonite or chitosan [22,24]. The chitosan–bentonite
alkylammonium compounds, berberine is a selective nanocomposites also show antibacterial activity (both Gram
, D H Anh and K Dumri
positive, e.g., Bacillus subtilis and Staphylococcus aureus,
and Gram negative, e.g., Escherichia coli) as well as higher
tensile strength in comparison with chitosan moiety [25,26].
The organophosphate (OP) insecticides tested in this
work were chlorpyrifos, profenofos, dimethoate and methyl
parathion. They are classified into class II (moderately toxic)
and class IA (extremely toxic) for inhalation and ingestion
by WHO, respectively [27]. Agricultural-product-exporting
countries, e.g., Thailand, use these OP insecticides but the
control of use is always problematic; therefore, their residues
can be detected ubiquitously not only in harvested products
but also in nearby agricultural water zones or even in fresh
water sources due to rainfall event [28,29]. Towards this end,
we fabricated a film composed of berberine-modified ben-
tonite and synthesized CMCh. The film materials were tested
to remove the four aforementioned OP insecticides in spiked
water. The absorptivity of the film based on their structures
and the interactions between film components and OP insec-
Figure 1. Structures of berberine chloride and tested OP insecti-
ticides are described and discussed.
cides.
2. Experimental pipetted step-wise (100 µl in 10 s) into the Na-bentonite mix-
ture with vigorous stirring. Subsequently, the reaction mixture
2.1 Materials was stirred at 600 rpm for 8 h. The yellow sediment was
allowed to settle within 2 h, collected and dried at 95◦ C for
The commercial bentonite or calcium bentonite (designated as 12 h. The dried sediment was ground to powder and sieved
bentonite) was purchased from Srichand United Dispensary using a 300-mesh sieve (Gallenkamp and Co, London). The
Co., Ltd. (Bangkok, Thailand). Commercial grade shrimp chi- latter was used for all insecticides absorption tests through-
tosan of flake polymer type (molecular weight in the range out this work and it was designated as BBr-bentonite. Both
900–1,300 kDa) was purchased from Taming Enterprises Na-bentonite and BBr-bentonite are generally designated as
(Samutsakon, Thailand). modified bentonite in all following contexts.
All chemicals were of analytical grade. Berberine chlo-
ride (98%, designated as BBrCl) and OP insecticides (>97%, 2.3 Synthesis of CMCh
PESTANAL , including methyl parathion, chlorpyrifos, pro-
fenofos and dimethoate, were purchased from Sigma and CMCh was synthesized by the procedure of Chen and Park
Riedel de Haen (Germany) (figure 1). Stock solutions (100 [33]. The chitosan powder (25 g) was suspended in a solution
mM) of insecticides were prepared in methanol (MeOH) and of NaOH:i-propanol:H2 O (1:8:2) and stirred at room temper-
kept at 4◦ C until further use. Working insecticide solutions ature for 1 h. The appropriate amount of monochloroacetic
were prepared at 5 ppm in distilled water of pH 7.2. acid was added into the mixture and continuously stirred for
30 min. The mixture was covered with an aluminium foil and
2.2 Two steps modification of commercial bentonite by placed in an oven at 50◦ C for 4 h. Later, it was separated
NaCl and BBrCl into liquid and solid phases. The solid phase was further sus-
pended in MeOH and neutralized with glacial acetic acid.
In the first step, bentonite was modified by NaCl to form Na- Subsequently, it was filtered and washed 5 times with ethanol
bentonite; 100 g of bentonite was well dispersed in 1 litre (70% v/v EtOH) to remove undesirable products and the last
of NaCl (0.1 M, pH 7.5) and vigorously stirred at 600 rpm time with absolute MeOH. The final product, designated as
for 8 h at room temperature. Afterwards, the reaction mix- CMCh, was dried in the oven at 50◦ C for 18 h and kept in a
ture was allowed to settle for 2 h and the supernatant was sealed polyethylene bag until further use.
decanted. Later, the bentonite sediment was washed repeat-
edly 4–6 times by deionized water to eliminate the redundant 2.4 Casting of hybrid film containing organobentonite and
NaCl. Subsequently, NaCl residue in the supernatant was CMCh
tested using a Chloride Low Range Test Kit, Model 8-P, Hach
(USA). The bentonite sediment was dried at 95◦ C for 12 h Modified bentonite (2 g, BBr-bentonite and Na-bentonite)
and ground to powder afterwards. This was designated as was firstly added step-wise (50 mg in 10 s) into 500 ml distilled
Na-bentonite. In the second step, 30 g of Na-bentonite was water at 80◦ C under 500 rpm stirring in a 1-litre glass beaker
re-dispersed in 1 litre of deionized water and 10 ml homo- until a homogeneous grey suspension solution (Na/bentonite)
geneous BBrCl solution (0.3 g BBrCl in 10 ml MeOH) was or yellow suspension solution (BBr/bentonite) was formed.
