COMPARISON OF THE ADSORPTION CAPACITIES OF TWO ALBANIAN CLAYS FOR THE REMOVAL OF METRIBUZINE FROM CONTAMINATED WATERS

NATURA MONTENEGRINA, Podgorica, 2013, 12(3-4) : 949-965

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ORIGINAL RESEARCH PAPER COMPARISON OF THE ADSORPTION CAPACITIES OF TWO ALBANIAN CLAYS FOR THE REMOVAL OF METRIBUZINE FROM CONTAMINATED WATERS Kledi X H A X H I U 1, Lorenc S U L A 1, Jehona S H L L A K U 1, Arjan X H E L A J 2 and Teodor K O T A 2 1 Department of Chemistry, Faculty of Natural Sciences, blv. “Zogu I” 1001, Tirana, Albania 2 Department of Physics, Faculty of Natural Sciences, blv. “Zogu I” 1001, Tirana, Albania Corresponding author: [email protected]

Key words: Metribuzine adsorption, natural and activated Albanian clays, adsorption capacity.

SYNOPSIS

The distinctive adsorptive properties of clays are very appealing for the removal of organic pollutants from contaminated waters. Taking advantage of this property, we investigated the adsorptive capacities of two natural and H2SO4 activated Albanian clays toward metribuzine. A 0.200 g/l metribuzine aqueous solution at 25 °C placed in contact upon stirring with the clays of Brari and Prrenjasi for a period of 72 h, exhibited significantly higher adsorption of the latter. For 24 h clay-pesticide solution contact time, natural Prrenjasi clay adsorbs up to 0.218 mg/g compared to 0.05 mg/g for natural Brari clay. Increases of the clay-pesticide solution contact time leads to enhanced adsorbed amounts for both clays. Within the time interval 48-72 h, the clay of Prrenjasi shows a steeper adsorption compared to Brari clay. The H2SO4 activation changes insignificantly the adsorptive properties of Prrenjasi clay, but enhances dramatically the adsorption behavior of Brari clay. Increasing the metribuzine concentration from 0.200 g/l to 0.400 g/l increases the adsorption capacity approx. 7 times for both activated clays. At such metribuzine concentration, activated Prrenjasi clay reaches the max. adsorption of 1.732 mg/g within 48 h of contact time compared to 0.636 mg/g exhibited by Brari clay for 72 h.

INTRODUCTION The increasing demand for food and agricultural products is nowadays

associated with continuously enhanced usage of fertilizers and pesticides which often bear hazardous environmental side-effects. The occurrence organic pollutants, such as phenols, hydrocarbons, pesticides, pharmaceuticals etc. in superficial and ground waters as a result of uncontrolled and their systematic application is rising big environmental issues especially in development countries. In this context several

Natura Montenegr ina 12 (3 -4 ) , 2013

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water purifying strategies are proposed in order to alleviate somehow this burden contributing in this way in the recovery of millions of cubic meters of water (Petrie et al., 1993; Lin & Chen, 1997; Mota & Lyubchik, 2006, Ali et al., 2012). Among all of these strategies, the water purifying via adsorption has resulted the most effective (Ali et al., 2012). The adsorption itself occurring as an equilibrium process in a bi- or multi-phase system, diminishes the quantity of the contaminant, also called adsorbate, accumulating it in the interface between phases, causing therefore the decrease of its concentration in precedent one.

The classical and most exploited adsorbent employed for the adsorption of diverse organic contaminants is activated coal represents (Ali & Aboul-Enein, 2004; Damià, 2005). In spite of its vast applications, the cost related to its production restricts its abundant industrial and environmental application. Alternative cheap adsorbents such as: Scrap tyres, bark, tannin-rich materials, industrial wastes i.e. sugar industry wastes, fly ash are tested and reported (Hutchinson et al., 1993; Streat et al., 1995; Bras et al., 1999; Albanis et al., 1998; Gupta & Ali, 2001).

Following this trend, semi-natural products such as bamboo charcoal is proposed by Zhao et al. for the removal and determination of atrazine and simazin in environment aqueous samples (Zhao et al., 2008).Castro et al. proposed a method which combines the adsorption features of activated carbon and the oxidation properties of iron oxides composite to produce new materials for atrazine removal from aqueous solution (Castro et al., 2009). Focusing on the removal of triazine from aqueous solutions, Lemić et al. expanded the range of sorbents, including even organic zeolites (Lemić et al., 2006). The food waste is often seen as a contributor for the environment relief. Ara et al. (2013) determined the influence of physico-chemical parameters on the metribuzin adsorbing capacity of corn cob. Using Langumir isotherm data they found a considerable monolayer adsorbing capacity for corn cob ranging up to 4.07 mg/g.

Beside all of these alternative materials proposed, sediments and soils are becoming very appealing because of their abundance and promising adsorption properties related to the large surface area and porosity (Oren & Chefetz, 2012). Exploiting these natural materials, Kibe et al. reported on the adsorption of five herbicides by paddy soil in Japan (Kibe et al., 2000). Successive sorption–desorption cycles of dissolved organic matter in mineral soil matrices are reported by Oren & Chefetz (Oren & Chefetz, 2012). In this course of investigations, Zhang et al. and Liu et al. reported on the influence of pH on the adsorption of tetracycline from soil, sediment, Na- and organo-montmorillonites (Zhang et al., 2011; Liu et al., 2012). The latter found adsorbing capacities up to 1000–2000 mmol tetracycline per kg of clay. Carbendazim adsorption in Polish mineral soils is studied by Paszko, which reported carbendazim adsorption coefficients ranging between 0.3 and 151.8 ml/g (Paszko, 2012).

Xhaxhiu et al.: COMP ARISON OF THE ADSORPTION C AP ACIT IES OF TWO ALB ANI AN . . .

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Endorsing adsorption studies of pharmaceuticals and herbicides onto soils and natural clays have revealed significant influence of cationic exchanging as a result of the adsorption process. Versatile studies assess the adsorption of pesticides by soils and clays which are recently employed as pesticide holders for controlled released formulations (Hermosin et al., 2006; Sanchez-Verdejo et al., 2008). Granulate formulations made of alginate beads, alginate-kaolin-linseed oil and organo-montmorillonte have been successfully used as metribuzin absorber/holders with typical low metribuzin release rate for the prolongation of the crop treatment (Pepperman & Kuan, 1993; Selin et al., 1998; Singh, 2006; Flores-Cespedes, 2007). Considering the adsorbing properties of clays toward organic contaminants and pesticides we focused our laboratory research on the adsorbing capacities of two natural and activated Albanian clays aiming the removal of metribuzin from contaminated waters. The influence of contact time and metribuzin concentration on the clay adsorption capacity makes the leitmotif of this study which among others aims to compare the efficiency of each considered clay.

Taking advantage of their properties we report herein on the adsorption properties of natural and acid activated Prrenjasi clay toward metribuzin from aqueous solutions. Important process parameters such as contact time and concentration are considered in this study.

MATERIALS AND METHOD CHEMICALS Metribuzin analytical standard (Supelco) in ampoules of 250 mg is supplied by

the company Sigma-Aldrich, Seelze, Germany. Dibutyl phthalate, analytical standard for environmental analysis, Fluka, Buchs, Germany. Chloroform analysis grade (≥ 99.9%), and the inorganic salts, such as KCl (99.999%) and Na2SO4 anhydrous for synthesis were delivered by Merck KGaA, Darmstadt, Germany.

METRIBUZIN AND ITS CHARACTERISTICS Metribuzine with its systematic name: 4-Amino-6-tert-butyl-3-methylthio-1,2,4-

triazin-5-on is an asymmetric triazine herbicide, containing a single N-amino group in the 4-position of the ring. It is vastly applied as pre- and post-emergent broadleaf weeds control for a variety of agricultural crops all over the world.

Figure 1 : S t ructura l formula o f metr ibuz ine.


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Metribuzin shows relatively high water solubility (Table 1) and a moderate persistence in soil. Direct light causes its photolysis and reduces its persistence (Muszkat et al. 1998). Some important physico-chemical characteristics of it are summarized in table 1.

Table 1 . Some phys ico-chemica l proper t ies o f metr ibuz ine (Kamr in , 1997) .

Metribuzin (C8H14N4OS)

Molecular weight (g/mol) 214.29

Density/20° C (g/ml) 1.28

Melting point (° C) 126.2

Vapor pressure/20° C (mmHg) < 1.3 x 10-3 Pa

Solubility in water/20° C (g/l) 1.2

TOXICITY Triazines as many other herbicides is nowadays continuously more and more

present in surface and ground waters affecting often the existence of non-target organisms (Carabias-Martínez et al., 2003; Noppe et al., 2007, Quednow & Püttmann 2007). Metribuzin similarly to the other triazines interfere with photosynthesis in plants having as a primary target the inhibition of the Hill reaction of photosynthetic electron transport (Waxman, 1998). Metribuzin depresses the aquatic plant growth (Pauli et al., 1990) and is more toxic to them than atrazine, alachlor, or metolachlor (Fairchild et al., 1998). A latter 6-week study conducted by them, aiming the examination of the aquatic fate and effects of metribuzin concentration in 0.1-ha outdoor aquatic mesocosms (Fairchild & Sappington, 2002) revealed no significant effects of metribuzin on water quality, periphyton biomass, macrophyte biomass, macrophyte species composition, fish survival, or fish growth at concentrations up to 75 µg/l. LC50 value for rainbow trout juveniles of 83.9 mg/l corresponding to 62.51 mg/l of pure metribuzin were reported by Velisek et al. based on an acute semistatical toxicity test lasting 96 h, while using the formulated trade product “Sencor WG 70“ which consisted of 70 % metribuzin (Velisek et al. 2008). Plhalova et al. assessed recently the impact of metribuzin dissolved in surface waters on Danio rerio fish. A 28-day toxicity test on it revealed the presence of pathological lesions in the liver of pesticide-exposed fish at metribuzin concentration of 53 mg/l (Plhalova et al., 2012). Furthermore the LOEC (Lowest Observed Effect Concentration) and NOEC (No Observed Effect Cncentration) values fort his fish were 33 mg/l and 16 mg/l. Acute oral metribuzin LD50 on birds and mammals range from 164 mg/kg for bobwhite quail to 2345 mg/kg for rats (Worthing & Walker 1987; Löser and Kimmerle 1972). Wnuk et al. reported NOEC values of 15 mg/kg and 300 mg/kg for rats and rabbits (Wnuk et al., 1987). Regarding the risk that metribuzin


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represents, the Canadian interim water quality guideline for protection of livestock has ascertained 80 µg/l the maximal aloud limit of metribuzin in drinking water (Health Canada 1996).

DEGRADATION AND HALF-LIFE The behavior and persistence of metribuzin in soil and pond waters is

thoroughly covered in the literature. Webster et al. (Webster et al., 1978) reported that metribuzin persisted in Manitoba soil to the year following application with estimated half-lives of 60-90 days in various soils. Laboratory and field behavior of metribuzine at 20°C was studied and reported by Hyzak and Zimdahl (Hyzak & Zimdahl, 1974). They indicated a variable half-life of metribuzin from 43 to 46 days and described its degradation in soil according to a first order kinetics. This fact was confirmed later by Savage for six soils under greenhouse conditions using GC-techniques (Savage, 1977). He reported metribuzin half-lives ranging from 17-28 days. Parallel and simultaneous researches with Hyzak and Zimdahl were conducted by Lay and Ilnicki (Lay & Ilnicki, 1974) revealing a degradation rate of metribuzin up to 90 %, at 28°C within 42 days. Consequent studies of Ladlie et al. followed by Smith and Walker correlated the metribuzin half-life with the soil moisture content, penetration depth, temperature and soil pH (Ladlie et al. 1976a; Smith and Walker 1989). Despite of nonbiological degradation of metribuzin occurring at a certain level as reported by Webster et al. (Webster et al. 1978), one of the main natural mechanisms for the removal of metribuzin from soil relays on the microbial metabolism (Ladlie et al. 1976b). The latter found a close relation between the metribuzin degradation rate constants and the microbial activity which of course was correlated to the available amount of herbicide in the soil. Savage reinforced the discovery on the role of microbial activity on the degradation of metribuzin in soil, adding to it the role of the soil glucose content and temperature increase (Savage, 1977). Unlike the reported metribuzin life-time in soils, its half-life in pond water according to Kidd and James is approx. 7 days (Kidd & James, 1991). A latter study of Fairchild and Sappington shows even faster metribuzin half-life in water ranging up to 5 days (Fairchild & Sappington, 2002).

THE CHARACTERISTICS OF NATURAL CLAYS OF BRARI AND PRRENJASI For the purpose of this study, natural clays samples from Brari (Tirana)

41°21'14.49"N; 19°50'17.74"E and Prrenjasi (Librazhd, Albania) 41°4'3.88"N; 20°33'2.33"E were selected based on a registered database from the Institute of Geological Researches, University of Tirana. The collected samples were mixed, grinded, air-dried for 4 h at 150°C, and sieved by a 74 mesh sieve (fraction: 0-0.250 mm). Their chemical compositions, along with the physico-chemical properties as previously determined and reported by Kola (Kola, 1986) are listed in tables 2, 3.


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Table 2 : Chemica l composi t ion (w t . %) o f natura l c lays o f Brar i and Prrenjas i (Ko la , 1986) .

Region SiO2 Al2O3 Fe2O3 CaO MgO TiO2 Na2O+K2O HK

Brari 43.4-53.9 11-15.8 5.4-7.7 7.7-11 4-7.9 - 3.03-3.93 10-14.9

Prrenjasi 46.5-52.9 6.4-9.2 2.8-18 0.1-3.5 5-16 0.3-0.7 0.3-0.8 16-20

Tab le 3 : Phys ico-chemica l parameters o f na tura l c lays o f Brar i and Prrenjas i (Ko la , 1986) .

Region pH density (g/cm3)

s. surface* (m2/g)

porosity (%)

Brari 7.5 2.77 42 0.490

Prrenjasi 7.4 2.78 175 0.558

* determined using a blue methylene solution The high ratio SiO2:Al2O3 is directly related to the clay montmorillonite content

and their good adsorbing properties, typical for the natural clay of Prrenjasi. Detailed thermogravimetric measurements combined with microscopic investigations have shown considerable contents of monmorillonite, halloysite and kaolinite in it (Kola, 1986). It contains < 1 % carbonate and is a high Na-content. The natural clay of Brari instead, is distinguishe for its typically high carbonate content in form of CaCO3 (21.8-23.2 %), the absence of titanium dioxide as well as the low ratio SiO2:Al2O3.

The natural clay of Brari has a lower surface area (42 m2/g) and porosity (0.490 %) (table 3) compared to Prrenjasi Clay which shows a specific surface area of 175 m2/g estimated as approx. 3 times higher than the average of the majority of natural Albanian clays (Kola, 1986) and a porosity of 0.558 %. These parameters which probably are related with the high content of montmorillonites in it, make this clay very appealing for various adsorption/separation processes.

SULPHURIC ACID ACTIVATION OF THE CLAYS The chemical activation of Brari and Prrenjasi clays were carried out in each

case by adding 200g of the clay to 600 ml of 10% sulphuric acid solution and refluxing at120 °C under the atmospheric pressure in a round bottomed 1 l flask. The process occurred under continuous stirring using a magnetic stirrer for 4h. The obtained clay suspension in each case was filtered and repeatedly washed with distilled water to remove the remaining of unreacted acid. After it, the clay was dried


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in an oven, at 105 °C for 24h, ground in a mortar pastel to powder form and then sieved to obtain the particle fraction 0-0.250 mm.

CHARACTERISATION TECHNIQUES The gas chromatographic analyses were performed on a Hewlett Packard HP

GC equipped with a single FID detector. Nitrogen was the carrier gas with a flow rate of 2.5 ml/min. The column was manufactured by Agilent J&W HP-5, 25 m x 0.32 mm x 0.17 μm film thickness. The column working temperature was set to 160-180°C, the detector and injection temperature: 250°C; head pressure 50 kPa. All the experiments ran in splitless mode.

Powder X-Ray measurements for the characterisation of clay samples were performed with a powder diffraction device D5000 delivered by SIEMENS company (XRD; Siemens D5000, Bruker-AXS, Karlsruhe, Germany) using CuKα1-radiation (λ = 1.54051 Å) in transmission mode. For the measurements, 50-100 mg of fine powdered sample was spread on a Mylar-foil (covered with a thin layer of silicon grease) and the foil was fixed on a flatbed holder. The diffraction patterns were recorded within the 2θ angle interval 5-80° by means of a “Braun” Position Sensitive Detector (PSD-50M) with an angular increment of 0.025°/min.

EXTRACTION AND STANDARD SOLUTIONS Chloroform was employed as extracting agent. Dibutyl phthalate was employed

as internal standard. A solution of dibutyl phthalate in absolute ethanol with a concentration of 2.5 mg/ml was prepared. To endorse the experiments, a reference metribuzin solution with a concentration of 3 mg/ml was prepared using metribuzin analytical standard in a mixture of absolute ethanol and dichloromethane 1:1 (v/v).

ADSORPTION EXPERIMENTS PROCEDURE To perform the adsorption experiments, an initial metribuzin stock solution of 1

g/l was prepared by dissolving the appropriate amount of metribuzin in distilled water. The experimental solutions with the concentrations of 0.200 g/l and 0.400 g/l were obtained by diluting the initial stock solution with distilled water. In a series of glass bottles equipped with stoppers 30 g of clay and 150 ml of metribuzin aqueous solution were added in each case, respecting the ratio clay-solution 1:5. The obtained suspension was kept in continuous stirring during the whole experiment time to avoid the clay sedimentation. In selected time intervals of 24, 48, 72 h, 40 ml of suspension was drawn in each case for centrifuging. The samples were centrifuged in an Eppendorf centrifuge 5403 for 15 min at 5000 rot/min until the suspension was clearly separated. In a 25 ml clear solution obtained right after centrifuging 3 g of crystalline KCl were added and shaken until the salt was completely dissolved. After that, 10 ml of extracting solvent (chloroform) were added and well shaken for 15 min in a Fritsch Analysette (type 03502) mechanical vibrator.


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This procedure was repeated 3 times. The collected extracts were unified and dried over Na2SO4. Prior to GC analysis, the dried solution in each case was spiked with 0.1 ml of internal standard dibutyl phthalate (5 mg/ml) using a chromatographic micro-syringe. The amount of metribuzin adsorbed at a time t (min) was calculated by the equation (1):

( )0 t

t

C C Vm−

Γ = (1)

Where Γ t is the amount of metribuzin adsorbed at a time t (mg/g), C0 and C t

are the initial and the concentration of metribuzin at a time t (g/l), V is the volume of the suspension (ml) and m is the clay weight (g). The adsorption experiments were triplicates to ensure the data reproducibility.

DISCUSSION OF THE RESULTS THE EFFICIENCY OF ACID ACTIVATION ON THE SELECTED CLAYS The improvement of the adsorbing properties of clays which are directly

related to the clay’s surface area and porosity occur through altering of its chemical composition as well as its structure (Panda et al., 2010; Zhao et al., 2013). This process of improving the physical properties of the clays is called acid activation. It consists on a chemical treatment based on the leaching of the clay with inorganic acids such as HCl or H2SO4, etc. for the elimination of mineral impurities. Previous sulfuric acid activation (10 %) performed by Kola (Kola, 1986) to the Brari and Prrenjasi natural clays, followed by blue methylene adsorption technique, exhibited increases of their specific surfaces from 42 and 175 m2/g to 86 and 425 m2/g respectively. Blue methylene adsorption method represents a simple, uncomplicated, rapid and economical way of for specific surface area determination which is quite reliable and applicable for minerals under aqueous conditions (Hang & Bridley, 1970). These authors while studying samples originating from Florida kaolinite and Wyoming Na montmorillonite found comparable surface area values obtained by this method as by N2 adsorption.

Following the previous works of Kola (Kola, 1986) we activated the natural clays of Brari and Prrenjasi with 10 % sulphuric acid (approx. 1.1 M) for 4 h under continuous stirring followed by several washing/filtration steps and 1 d of drying/thermal treatment. For comparison reasons, the recorded powder X-Ray measurements of the natural and activated Brari and Prrenjasi clays are plotted in fig. 2.

Fig. 2 exhibits an obvious difference in the XRD-powder pattern of Brari and Prrenjasi natural clays which is strongly related to the kaolinite content in Prrenjasi


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clay unlike Brari clay as well as the content of various binary compounds found in them. The higher background noise present in natural Prrenjasi XRD pattern, as well as the low intensity of its reflections is due to the considerable presence of nano- and micro particle fraction (0-2μ) in it, responsible for intensity poor/amorphous-like diffraction patterns. The acid activation process caused a the decrease of the sample crystallinities in both of them visible by the diminishing of the reflection intensities associated by consequent increases of the amorphous content in them due to the leaching of Al3+ ions from the clay structures. Panda et al. have reported that a reduction of the Al-content in kaolinite containing clays increases the Si/Al ratio which combined to the simultaneous amorphization of the silica phase lead to enhancement of porosity and surface area (Panda et al., 2010). Meanwhile, according to Zhao et al. the presence of the persistent reflections in them after the acid activation is dedicated to the monmorillonitic content of these clays which preserved the layered structural features and their crystallinities (Zhao et al., 2013). Based on these reports and observations, Prrenjasi clay was prone of more significant changes after acid activation (Fig. 2), due to a considerable kaolinite phase in it.

Figure 2 : XRD pow der d i f f rac t ion pat terns o f natura l and act iva ted Brar i and Prren jas i c lay. The presence of montmor i l lon i te in the Pr renjas i c lay is notab le a lso f rom the f i rs t broad re f lec t ion a t 2θ < 10° .

METRIBUZIN ADSORPTION/REMOVAL The efficiency of natural and activated Brari and Prrenjasi clays on metribuzin

removal/adsorption from aqueous solutions was studied in each case by suspending fractions 0-0.250 mm of them in two metribuzin solutions with initial concentrations of 0.200, 0.400 g/l under continuous stirring at 23°C. Considering the metribuzin


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degradation times from the literature, the maximal contact time clay-metribuzin solution was set to 72 h. Samples for analyses were drawn from the batch solutions each 24, 48 and 72 h. The obtained results are depicted in figures 3 and 4. As shown by fig. 3, which corresponds to initial metribuzin concentration of 0.200 g/l the natural clays of Brari and Prrenjasi exhibit different adsorption profiles. These differences are smoothed upon their activation. The natural clay of Brari shows a very low initial adsorption (24h) 0.05 mg/g followed by a linear increase up to 0.081 mg/g. This adsorption picture changes for the activated clay. From 0.07 mg/g recorded within 24 h of contact time it increases quickly up to 0.244 mg/g at 48h and then steadily further reaching 0.269 mg/g at the end of the process. In contrast to it, the natural and activated clay of Prrenjasi exhibit a comparable metribuzin adsorption behavior within the whole investigation period with a slightly higher initial adsorption in favor of the natural clay. Within the first 24 h of contact time the values of metribuzin adsorption for the natural and activated clay were 0.215 and 0.185 mg/g the adsorption increases up to 126 % and 163 % respectively at 48 h of contact time, followed by a further increase of 26.5 % and 29.2 % at 72 h which corresponds to 0.615 mg/g and 0.628 mg/g of metribuzin adsorbed. In both cases similar to the activated Brari clay, the initial adsorption slope (0 – 48 h) is steeper in comparison to the interval 48 – 72 h. For metribuzin aqueous solution with a concentration 0.200 g/l, Prrenjasi clay results much more effective than Brari clay in the removal of metribuzin, although that the adsorption increase through clay activation results more efficient for the Brari clay. At this metribuzin concentration, the adsorption process for both considered clays isn’t completed even at 72 h which suggests therefore a longer clay-metribuzin solution contact time.

Figure 3 : Met r ibuz in adsorpt ion f rom i ts aqueous so lu t ion w i th a concent ra t ion o f 0 .200 g / l , by natura l and act iva ted c lays o f Brar i and Prren jas i .


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Metribuzin concentration increase from 0.200 g/l to 0.400 g/l enhances considerably the initial (24 h) adsorbed quantity of the activated Brari clay in comparison to the natural one. The doubling of the metribuzin concentration was associated by an initial adsorption increase of 60% (0.08 mg/g) for the natural clay and over 600 % (0.513 mg/g) for the activated Brari clay (Fig. 4). Both clays adsorb linearly within the investigated time (72 h), revealing adsorption lines which run parallel but quite distant to each other. The max adsorbed amounts of the natural and activated Brari clay at this metribuzin concentration and 72 h of contact time were 0.235 mg/g and 0.636 mg/g respectively.

Figure 4 : Met r ibuz in adsorpt ion f rom i ts aqueous so lu t ion w i th a concent ra t ion o f 0 .400 g / l , by natura l and act iva ted c lays o f Brar i and Prren jas i .

The same trend was observed for Prrenjasi clay upon doubling of metribuzin

concentration too. The initial adsorption (24 h) of this clay compared to the adsorption at metribuzin concentration of 0.200 g/l increased over 5 and 6 times which corresponds respectively to 1.356 mg/g and 1.385 mg/g for the natural clay activated clay (Fig. 4). The extension of the adsorption time to 48 h emphasizes the superiority of the Prrenjasi activated clay toward the natural one, resulting in an adsorption difference of 0.22 mg/g (14.6 %). Beyond this time, the picture exhibited by the metribuzin adsorption of the natural and activated Prrenjasi clay unveils unusual anomalies. Adsorption curve inflections right after the adsorption maxima are observed in each case. This is related to the decrease of metribuzin quantity adsorbed with time, a phenomenon which is strongly related with metribuzin: a) degradation in the active sites of the clays, in these cases the clay plays the role of the catalyst, b) desorption from clay adsorbing sites to reestablish the equilibrium concentration due to its concentration decrease in solution as a consequence of degradation. Once metribuzin is degraded into smaller molecules, the smaller


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molecules are better adsorbed in the clay surface due to their smaller sizes which enhance and favor their pore diffusivities. This phenomenon is also reported by Ara et al. (Ara et al., 2013) in their study of metribuzin removal from aqueous solutions using corn cob. They found for this adsorbent an inflection point/adsorption decrease starts right after of 72 min of contact time. Meanwhile our recent research on methomyl adsorption by Prrenjasi clay exhibited the same phenomenon for the whole range of investigated concentrations (Xhaxhiu et al., 2013). The time-dependent metribuzin adsorption decrease for this clay is better observable at higher metribuzin concentrations. Its concentration decrease seems to hide this phenomenon which occurs simultaneously with the adsorption. Hence, this might be a lateral factor which probably influenced the slope decrease in metribuzin adsorption for a concentration of 0.200 g/l (Fig. 3). Finally the metribuzin adsorption values recoded after 72 h of contact time for the natural and activated clay were: 1.414 mg/g and 1.555 mg/g corresponding to adsorption decreases of 6.5% and 10.2% respectively. Therefore, the high metribuzin adsorbing capacity of Prrenjasi clay can be directly attributed to its high montmorillonite content along with halloysite and kaolinite. This fact is already reported by Sha’ato et al. (Sha’ato et al., 2000).

A comparison between Prrenjasi and Brari clay for metribuzin concentration of 0.400 g/l shows significant differences visible not only in their adsorption evolution but also in the amounts of metribuzin adsorbed (Fig. 4). The natural and activated Prrenjasi clay adsorbs 17 and 2.7 times more metribuzin within 24 h compared to natural and activated Brari clay. This difference slightly is deepen until a clay-metribuzin solution contact time of 48 h and turns later to initial values due to the metribuzin degradation in Prrenjasi clay. Metribuzin like methomyl and other pesticides degrade easily on Prrenjasi clay due to: its high specific area (high number of active sites) in comparison to other Albanian clays, and b) the content of different inorganic compounds incorporated to its structure, e.g. such as TiO2, which act as catalysts/activators of pesticide/herbicide degradation in the clay active sites. Finally, activated Prrenjasi clay reaches the max. metribuzin adsorption of 1.732 mg/g after 48 h resulting much more effective than activated Brari clay which exhibits a max adsorption of 0.636 mg/g for a contact time of 72 h.

CONCLUSIONS We reported in this study the feasibility of metribuzin removal/adsorption from

its aqueous solutions using natural and activated Brari and Prrenjasi clays, aiming also the comparison of the adsorption capacities of these clays. The adsorption process itself is characterized in terms of: a) herbicide-clay contact time and b) the influence of metribuzin concentration on the adsorption. The adsorption process was


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investigated within a time period of 72 h taking into considerations two aqueous metribuzin concentrations of 0.200 g/l and 0.400 g/l.

For metribuzin aqueous solution with a concentration 0.200 g/l, the natural and activated clays of Prrenjasi resulted much more effective than natural and activated Brari clay in the removal of metribuzin, showing max. adsorption values of 0.615 mg/g and 0.628 mg/g respectively toward 0.081 mg/g and 0.269 mg/g recorded for natural and activated Brari clay. In spite of it, the clay acid activation resulted more efficient regarding the adsorption increase for Brari clay compared to Prrenjasi clay. At such metribuzin concentration, the adsorption process for both considered clays isn’t completed even at 72 h which suggests therefore a longer clay-metribuzin solution contact time.

The doubling of metribuzin concentration from 0.200 g/l to 0.400 g/l reveals significant differences not only in the amount of metribuzin adsorbed but also in the adsorption behavior of both clays. Natural and activated Prrenjasi clays reach the max. metribuzin adsorption of 1.512 and 1.732 mg/g respectively within 48 h of contact time resulting therefore much more effective than natural and activated Brari clays which exhibit their max adsorption of 0.235 and 0.636 mg/g respectively within 72 h. In contrast to natural and activated Brari clay shows regular adsorption curves resembling to straight lines, Prrenjasi clay shows a regular adsorption behavior within the first 48 h of contact time, after that, the quantity of metribuzin adsorbed decreases as a consequence of its degradation and the easier adsorption of the degradation products competing with the unchanged molecules. This suggests 48 h of contact time for max efficiency for natural and activated Prrenjasi clays for metribuzin removal from aqueous solutions and over 72 h for the natural and activated Brari clays. Since the clay acid activation is associated with significant metribuzin adsorption increases in both cases it is highly recommended for both clays.

REFERENCES:

ALBANIS, T. A., DANIS, T. G., KOURGIA, M. G. 1998: Adsorption-desorption studies of

selected chlorophenols and herbicides and metal release in soil mixture with fly ash. -

Environmental Technology, 19: 25-34.

ALI, I., ABOUL-ENEIN, H. Y. 2004: Chiral Pollutants: Distribution, Toxicity and Analysis by

Chromatography and Capillary Electrophoresis. - John Wiley & Sons, Chichester.

ALI, I., ASIM, M., KHAN, T. A. 2012: Low cost adsorbents for the removal of organic

pollutants from wastewater. - Journal of Environtal Management, 113: 170-183.

ARA, B., SHAH, J., JAN, M. R., ASLAM, S. 2013: Removal of metribuzin herbicide from

aqueous solution using corn cob. - International Journal of Science, Environment and

Technology, 2(2): 146-161.


962

BRAS, I. P., SANTOS, L., ALVES, A. 1999: Organochlorine pesticides removal by pinus bark

sorption. - Environmental Science and Technology, 33: 631-634.

CARABIAS-MARTÍNEZ, R., RODRÍGUEZ-GONZALO, E., FERNÁNDEZ-LAESPADA, M. E.,

CALVO-SERONERO, L., SÁNCHEZ-SAN ROMÁN, F. J. 2003: Evolution over time of

the agricultural pollution of waters in an area of Salamanca and Zamora (Spain). -

Water Research, 37(4): 928-938.

CASTRO, C. S., GUERREIRO, M. C., GONCALVES, M., OLIVEIRA L. C. A., ANASTACIO, A.

S. 2009: Activated carbon/iron oxide composites for the removal of atrazine from

aqueous medium. - Journal of Hazardous Materials, 164: 609-614.

DAMIÀ, B. 2005: (Ed.), Emerging Organic Pollutants in Waste Waters and Sludge. -Springer,

Berlin, pp. 1-24.

FAIRCHILD, J. F., RUESSLER, D. S., CARLSON, A. R. 1998: Comparative sensitivity of five

species of macrophytes and six species of algae to atrazine, metribuzin, alachlor, and

metolachlor. - Environmental Toxicology and Chemistry, 17(9): 1830-1834.

FAIRCHILD J. F., SAPPINGTON L. C. 2002: Fate and effects of the triazinone herbicide

metribuzin in experimental pond mesocosms. - Archives of Environmental

Contamination and Toxicology, 43(2): 198-202.

FLORES-CESPEDES, F., VILLAFRANCA-SANCHEZ, M., PEREZ-GARCIA, S., FERNANDEZ-

PEREZ, M. 2007: Modifying sorbents in controlled release formulations to prevent

herbicides pollution. - Chemosphere, 6, 785-94.

GUPTA, V. K., ALI, I. 2001: Removal of DDD and DDE from wastewater using bagasse fly

ash- a sugar industry waste. - Water Research, 35: 33-40.

HANG, P. T., BRINDLEY, G. W. 1970 Methylene blue absorption by clay minerals.

determination of surface areas and cation exchange capacities (clay-organic

studies XVIII). - Clays and Clay Minerals, 18: 203-212.

HEALTH CANADA, 1996: Guidelines for Canadian drinking water quality. 6th ed. Prepared

by the Federal–Provincial Subcommittee on Drinking Water of the Federal–Provincial

Committee on Environmental and Occupational Health.

HERMOSIN, M. C., CELIS, R., FACENDA, M. J., CARRIZOSA, M. J., ORTEGA-CALVO, J. J.,

CORNEJO, J. 2006: Bioavailability of the herbicide 2,4-D formulated with organoclays.

- Soil Biology and Biochemistry, 38: 2117-2124.

HUTCHINSON, L. E., BERRY, D. F., MULLINS, D. E., HELZEL, G. H., YONG, R. W. 1993:

Evaluation of economical sorbents for removal of metolachlor from rinsate wastewater.

- Waste Management, 13: 83-87.

HYZAK, D. L. ZIMDAHL, R. L. 1974: Rate of degradation of Metribuzin and two analogue in

soil. - Weed Research, 22: 74-79.

KAMRIN, M. A. 1997: Pesticide profiles, toxicity, environmental impact, and fate. -Lewis

Publishers, CRC Press LLC, Boca Raton, Florida, US, pp. 1-704.


963

KIBE, K., TAKAHASHI, M., KAMEYA, T., URANO, K. 2000: Adsorption equilibriums of

principal herbicides on paddy soils in Japan. - Science of the Total Environment, 263:

115-125.

KIDD, H. JAMES, D. R., 1991: Eds. The Agrochemicals Handbook, Third Edition. Royal

Society of Chemistry Information Services, Cambridge, UK, (as updated). pp. 1-1500.

KOLA, V. 1986: Theoretical-experimental studies on the preparation, production and usage

of the

adsorbents from indigenous raw materials and their application in economy and defense.

PhD thesis, University of Tirana.

LADLIE, J.S., MEGGITT, W.F., PENNER, D. 1976a. Effect of soil pH on microbial

degradation, adsorption, and mobility of metribuzin. - Weed Science, 24(5): 477-481.

LADLIE, J.S., MEGGITT, W.F., PENNER, D. 1976b. Effect of pH on metribuzin activity in the

soil. - Weed Science, 24(5): 505-507.

LAY, M. M., ILNICKI, R. D. 1974: The residual activity of metribuzin in soil. - Weed

Research, 14: 289-291.

LEMIĆ, J., KOVACEVIĆ, D., TOMASEVI-CANOVIĆ, M., KOVACEVIĆ, D., STANIĆ, T.,

PFEND, R. 2006: Removal of atrazine, lindane and diazinone from water by organo-

zeolites, - Water Research, 40: 1079-1085.

LIN, S. H., CHEN, M. L. 1997: Treatment of textile wastewater by chemical methods for

reuse. - Water Research, 31: 868-876.

LIU, N., WANG, M.-X., LIU, M.-M., LIU, F., WENG, L., KOOPAL, L. K., TAN, W.-F. 2012:

Sorption of tetracycline on organo-montmorillonites. - Jorunal of Hazardous Materials,

225-226:28-35.

LÖSER, E., KIMMERLE, G. 1972: Acute and subchronic toxicity of Sencor active ingredient.

- Pflanzenschutz Nachrichten. 25:186-209.

MOTA, J. P., LYUBCHIK, S. 2006: Recent Advances in Adsorption Processes for

Environmental Protection and and Security. NATO Science for Peace and Security

Series C: Environmental Security. – Springer, Dordrecht, pp. 1-177.

MUSZKAT, L., FEIGELSON, L., BIRAND, L., MUSZKAT, I. C. A. 1998: Reaction patterns in

photopxidative degradation of two herbicides. - Chemosphere, 36: 1485-1492

NOPPE, H., GHEKIERE, A., VERSLYCKE, T., WULF, E. D., VERHEYDEN, K., MONTEYNE,

E., POLFLIET, K., CAETER, PV., JANSSEN C.R., DE BRABANDER, H. F. 2007:

Distribution and ecotoxicity of chlorotriazines in the Scheldt Estuary (B-Nl). -

Environmental Pollution, 147(3): 668-676.

OREN, A., CHEFETZ, B. 2012: Successive sorption–desorption cycles of dissolved organic

matter in mineral soil matrices. - Geoderma, 189-190: 108-115.

PANDA, A. K., MISHRA, B. G., MISHRA, D. K., SINGHA, R. K. 2010: Effect of sulphuric acid

treatment on the physico-chemical characteristics of kaolin clay. - Colloids and

Surfaces A: Physicochemical and Engineering Aspects, 363: 98-104.

PASZKO, T. 2012: Effect of pH on the adsorption of carbendazim in Polish mineral soils. -

Science of the Total Environment, 435-436: 222-229.


964

PAULI, B. D., KENT, R. A., WONG, M. P. 1990: Canadian water quality guidelines for

metribuzin, Environment Canada Scientific Series no. 179, Inland Waters Directorate,

Water Quality Branch.

PEPPERMAN, A. B.; KUAN, J. W. 1993: Slow release formulations of metribuzin based on

alginate-kaolin -linseed oil. - Journal of Controlled Release, 26: 21-30.

PETRIE, A. J., MELVIN, M. A. L., PLANE, N. H., LITTLEJOHN, J. W. 1993: The

effectiveness of water treatment processes for removal of herbicides. - Science of the

Total Environment, 135:161-169.

PLHALOVA, L., STEPANOVA, S., PRASKOVA, E., CHROMCOVA, L., ZELNICKOVA, L.,

DIVISOVA, L., SKORIC, M., PISTEKOVA, V., BEDANOVA, I., SVOBODOVA, Z. 2012:

The Effects of Subchronic Exposure to Metribuzin on Danio rerio. - The Scientific

World Journal, ID 728189, 6 pp.

QUEDNOW, K., PÜTTMANN, W. 2007: Monitoring terbutryn pollution in small rivers of

Hesse, Germany. - Journal of Environmental Monitoring, 9(12):1337-1343.

SANCHEZ-VERDEJO, M. T., UNDABEYTIA, T., NIR, S., MAQUEDA, C., MORILLO, E. 2008:

Environmentally friendly show release formulations of alachlor based on clay -

phosphatidylcholine. - Environmental Science and Technology, 42: 5779-5784.

SAVAGE, K. E. 1977: Metribuzin Persistence in Soil. - Weed Science, 25(1): 55-59.

SELIN, H. M., MCGOWEN, S. L., JOHNSON, R. M., PEPPERMAN, A. B. 1998: Fate of

metribuzin from alginate controlled formulations in a sharkey soil: 2. Transport. - Soil

Science, 16: 535-543.

SHA’ATO, R., BUNCEL, E., GAMBLE, D. G., VANLOON, G.W. 2000: Kinetics and equilibria

of Metribuzin sorption on model soil components. - Canadian journal of soil science,

301-307.

SINGH, N. 2006: Reduced downward mobility of metolachlor and metribuzin from surfactant-

modified clays. - Journal of Environmental Science and Health, Part B, 41: 17-29.

SMITH, A.E., WALKER, A.1989: Prediction of the persistence of the triazine herbicides

atrazine, cyanazine and metribuzin in Regina heavy clay. - Canadian Journal of Soil

Science, 69: 587-595.

STREAT, M., PATRICK, J. W., CAMPORRO-PEREZ, M. J. 1995: Sorption of phenol and p-

chlorophenol from water using conventional and novel activated carbons. - Water

Research, 29: 467-472.

VELISEK, J. SVOBODOVA, Z. PIACKOVA, V. NOVOTNY, L. BLAHOVA, J. SUDOVA, E.

MALY, V. 2008: Effects of metribuzin on rainbow trout (Oncorhynchus mykiss). -

Veterinarni Medicina, 53 (6): 324-332.

WAXMAN, M. F. 1998: Agrochemical and Pesticide Safety Handbook. Lewis Publishers, CRC

Press LLC, Boca Raton, Florida, US, pp. 1-611.

WEBSTER, G.R.B., SARNA, L.P. MACDONALD, S. R. 1978: Nonbiological degradation of

the herbicide metribuzin in Manitoba soils.- Bulletin of Environmental Contamination

and Toxicology, 20: 401-408.


965

WNUK, M., KELLEY, R., BREUER, G., JOHNSON, L. 1987: Pesticides in water supplies

using surface water sources. NTIS PB88-136916. Iowa Department Natural Resources,

Des Moines, IA, pp. 1-33.

WORTHING, C.R., WALKER, S.B. 1987: (eds.). The pesticide manual. A world compendium.

8th ed. British Crop Protection Council, Thornton Heath, UK, pp. 1-1081.

ZHANG, Z., SUNA, K., GAO, B., ZHANG, G., LIU, X., ZHAO, Y. 2011: Adsorption of

tetracycline on soil and sediment: Effects of pH and the presence of Cu(II). - Journal

of Hazardous Materials, 190:856-862.

ZHAO, R. S., YUAN, J. P., JIANG, T., SH, J. B., CHENG, C. G. 2008: Application of bamboo

charcoal as solid-phase extraction adsorbent for the determination of atrazine and

simazine in environmental water samples by high-performance liquid chromatography-

ultraviolet detector. - Talanta, 76: 956-959.

ZHAO, H., ZHOU, C. H., WU, L. M., LOU, J. Y., LI, N., YANG, H. M., TONG, D. S., YU,

W. H. 2013: Catalytic dehydration of glycerol to acrolein over sulfuric acid-activated

montmorillonite catalysts. - Applied Clay Science, 74:154-162.

XHAXHIU, K., PRIFTI, E., MELE, A., XHELAJ, A., KOTA, T. 2013: Methomyl adsorption from

aqueous solutions by four natural Albanian clays. Proceedings of VIII th Dubrovnik

Conference on Sustainable Development of Energy, Water and Environment Systems.

September 22-27, Dubrovnik, Croatia.

RECEIVED: 7 August 2013


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COMPARISON OF THE ADSORPTION CAPACITIES OF TWO ALBANIAN CLAYS FOR THE REMOVAL OF METRIBUZINE FROM CONTAMINATED WATERS

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