Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate

JES-00970; No of Pages 10 J O U RN A L OF E N V I RO N ME N TA L S CI EN CE S X X (2 0 1 6 ) XX X–XXX

Available online at www.sciencedirect.com

ScienceDirect www.elsevier.com/locate/jes

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Jun Dai1 , Wenqin Wang2 , Wenchen Wu3 , Jianbo Gao1 , Changxun Dong1,⁎

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1. College of Sciences, Nanjing Agricultural University, Nanjing 210095, China. E-mail: [email protected] 2. College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China 3. South China Institute of Environmental Sciences, Ministry of Environmental Protection, Guangzhou 510655, China

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Adsorption and desorption of Cu 2 + on paddy soil aggregates pretreated with different levels of phosphate

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AR TIC LE I NFO

ABSTR ACT

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Article history:

Interactions between anions and cations are important for understanding the behaviors of 16 Q4

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Received 3 November 2015

chemical pollutants and their potential risks in the environment. Here we prepared soil 17

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Revised 2 December 2015

aggregates of a yellow paddy soil from the Taihu Lake region using low-energy ultrasonic 18

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Accepted 27 June 2016

dispersing and freeze-drying techniques, and investigated the effects of phosphate (P) 19

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Available online xxxx

pretreatment on adsorption–desorption of Cu2+ of soil aggregates, free iron oxyhydrates- 20

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Keywords:

mechanisms by which P preadsorption influenced Cu2+ adsorption–desorption were also 22

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Paddy soil

discussed. The results showed that Cu2+ adsorption was reduced on the aggregates 23

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Aggregates

pretreated with low concentrations of P, and promoted with high concentrations of P, 24

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Copper (II)

showing a V-shaped change. Compared with the untreated aggregates, the adsorption 25

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Adsorption and desorption

capacity of Cu2+ was reduced when P application rates were lower than 260, 220, 130 and 26

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removed soil aggregates, goethite, and kaolinite with batch adsorption method. The 21

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110 mg/kg for coarse, clay, silt and fine sand fractions, respectively. On the contrary, the 27

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adsorption capacity of Cu2+ was higher on P-pretreated soil aggregates than on the control 28 ones when P application rates were greater than those values. However, the desorption of 29

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Cu2+ was enhanced at low levels of P, but suppressed at high levels of P, displaying an 30 inverted V-shaped change over P adsorption. The Cu2+ adsorption by the aggregate particles 31 correlation coefficient (r2) of 0.9805. The adsorption constant K was in order of high 33 concentrations of P pretreated > untreated > low concentrations of P pretreated aggregates. 34 Similar results were obtained on P-pretreated goethite. However, such P effects on Cu2+ 35 adsorption–desorption were not observed on kaolinite and free iron oxyhydrates-removed 36 soil aggregates. The present results indicate that goethite is one of the main soil substances 37 responsible for the P-induced promotion and inhibition of Cu2+ adsorption.

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Introduction

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Atmospheric pollutant precipitation, agricultural applications of industrial sludge and sewage, and long-term applications of mineral fertilizers and pesticides containing heavy metals,

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© 2016 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. 39

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with and without P pretreatments was well described by the Freundlich equation, with 32

Published by Elsevier B.V. 40

have caused the accumulation of heavy metals in farmland soils at an unprecedented rate (Luo et al., 2009), which thus poses serious risks to human health and environmental quality (Das, 2010). Studies have shown that the adsorption and desorption of heavy metals determine their retentions in

⁎ Corresponding author. E-mail: [email protected] (Changxun Dong).

http://dx.doi.org/10.1016/j.jes.2016.06.037 1001-0742/© 2016 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

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1. Materials and methods

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1.1. Preparation of soil aggregates

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Soil was sampled at 0–20 cm from a rice paddy field near Jinjiaba Township (31°5′N, 120°46′E), Wujiang Municipality, Jiangsu, China, using an Edelman auger. The soil sample was stored in refrigerator at 4°C. Soil fractions representing coarse sand of 2.00–0.20 mm, fine sand of 0.20–0.02 mm, silt of 0.02–0.002 mm, and clay of <0.002 mm, were obtained by using the method described by Stemmer et al. (1998). In brief, 50 g soil was placed in a glass beaker containing 250 mL distilled water (soil: distilled water ratio of 1:5) and allowed to stand overnight. Then, the soil in the beaker was subject to ultrasonic dispersion at low energy of 170 J/sec for 300 sec by a probe ultrasonic disaggregator (JYD-650, Zhisun Instrument Co., Ltd., Shanghai, China). Coarse sand fraction was obtained by wet sieving. Fine sand and silt fractions were isolated by sedimentation using Stock's law. Silk and clay fractions were fractionationed by centrifugation. All fraction samples were dried in a freeze-drier (Thermo Savant 100 Colin Drive, Holbrook, USA). The soil samples of <0.2 mm were sieved through 0.25 mm mesh, homogenized, and stored for use (Wang et al., 2009).

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preteated soil may be different from the higher concentration P preteated soil, and the mechanism should be investigated. Due to the large differences between the actual P content of soil environment, in the present study, the paddy soil aggregates from the Tai Lake region and soil minerals (goethite and kaolinite) were employed to investigate Cu2+ adsorption– desorption and their mechanisms by the soil aggregates and the clay minerals pretreated with different P concentrations. This work would shed light on the appropriate agricultural use of P fertilizers, the in-situ P immobilization remediation of heavy metal-polluted soils, and the environmental risk assessment of heavy metals.

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the soil and the forms of heavy metals control their mobility and bioavailability in the soil (Mirlean et al., 2009). Currently, a lot of research has been done on the chemical behaviors of Cu2+ in soil and the prevention and the control of soil Cu2+ pollution. Adsorption of Cu2+ in soil is influenced by many environmental factors (soil surface charge, pH, ionic strength, coexisting ions, oxides, organic matter, etc.). The net results show the promotion or inhibition of Cu2+ adsorption– desorption by soil (Arias et al., 2005; Basta et al., 2005; Kumpiene et al., 2007). Phosphorus (P) fertilization is one of major means to improve crop production in modern agriculture (Van Rotterdam et al., 2012). Since the 1980s, the applications of P fertilizers have increased greatly but the organic fertilizer uses have declined in most areas. In Jianghan plain of China, over 30% of farmland is P-rich, causing soil structure to change gradually (Li et al., 2007). In addition, P-containing compounds are often used for in-situ remediation of heavy metal polluted soils and it is one of the commonly used methods at home and abroad (Raicevic et al., 2005; Garrido et al., 2006; Ma et al., 2008). On one hand, P may directly interact with heavy metals to form precipitates. On the other hand, P adsorption by soil often changes surface charge properties, affecting the adsorption– desorption of metals in soil and the heavy metal bioavailability and the trace element supplies to plants (Pérez-Novo et al., 2009; Zhao and Selim, 2010). So far, there have been many investigations of phosphate adsorption impacting heavy metal adsorption by soils and soil minerals. These studies have showed that P increases soil surface negative charges and forms the coprecipitation with heavy metals on the soil surface, which could enhance the adsorbing capacity of heavy metals by soils (Pérez-Novo et al., 2011a; Tiberg et al., 2013). Pérez-Novo et al. (2009) found that the presence of large amount of P reduced the adsorption of Cu2+ on aluminum oxide and mineral surfaces. Li et al. (2007) noticed that the adsorption of phosphorus on goethite enhanced copper adsorption. Nelson (2012) has attributed the anion enhancement of Cu2+ adsorption on goethite to the formation of two ternary complexes on the surface. In these studies, the relatively high concentrations of P (greater than 100 mg/kg) have been used (Peltovuori and Soinne, 2005; Tiberg et al., 2013). They were much higher than the actual levels of P fertilizers for agricultural soils. For agricultural soils, the actual amount of P fertilizers (superphosphate) was usually less than 75 kg/km annually (Jiao et al., 2007), or about 5 mg/kg. while the usage amount of phosphates in the immobilization technology of heavy metal contaminated soil is larger, reach to 352 mg/kg (Huang et al., 2012). Thus, it is critical to study the adsorption of heavy metals by soil under low concentrations of P. In fact, a few studies have showed that P pretreatments at different concentrations had different impacts on the adsorption of heavy metals by soils. Li et al. (2006) observed that the pretreatment with the low concentrations of P suppressed the adsorption of Cu2+ and Cd2+ on hematite and had different influences for heavy metal adsorption. Currently, the most research for heavy metal on P pretreated soil was carried out using higher concentration P pretreatment, which led to increase the heavy metal adsorption capacity (Tiberg et al., 2013; Pérez-Novo et al., 2011a, 2011b) However, the effects of the heavy metal adsorption on lower concentration P

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137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154

1.2. Removal of free iron oxyhydrates (Fed) in soil aggregates 155 In order to investigate the effect of soil iron oxyhydrates on adsorption of Cu2+ on paddy soil aggregates pretreated with phosphate, the soil aggregates was treated with removal of free iron oxyhydrates (Fed). Subsamples from the above soil aggregate fractions were subject to removal of free iron oxyhydrates with dithionite-citrate-bicarbonate (DCB) according to the description by Wang et al. (2009). Briefly, 1.0 g aggregate sample was placed in a 50 mL plastic tube. Then, 15 mL of 0.3 mol/L citrate and 5 mL of 1 mol/L bicarbonate were added. The tube was heated to 80°C in a water bath, followed by addition of 0.5 g dithionite. After that, the tube was stirred for 10 min, and then centrifuged after cooling. Finally, the residue was washed with the distilled water for 2 to 3 times, and dried prior to use.

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1.3. Clay minerals

170

1.3.1. Preparation of kaolinite

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157 158 159 160 161 162 163 164 165 166 167 168 169

Kaolin was obtained from Maoming Municipality, Guangdong, 172 China. It was treated with 30% H2O2 to remove organic matter 173

Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

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J O U RN A L OF E N V I RO N ME N TA L S CI EN CE S X X (2 0 1 6 ) XX X–XXX

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Goethite used in this study was synthesized using the method described by Schwertmann and Cornell (1991). To form iron hydroxide, Fe(NO3)3 solution was rapidly neutralized by adding NaOH solution to reach pH 12.0. The resultant suspension was then aged at 60°C for 72 hr, followed by continuous washing and drying in air at room temperature. The synthesized material was confirmed to be the same material as one used by Fischer et al. (1996), using X-ray powder diffraction (XRD, Bruker-D8 Advance Super speed, Germany) and the Bragg reflection characteristics (Fig. 1a). The BET surface area of the goethite sample was determined to be 53.14 m2/g. A photomicrograph (Fig. 1b) of the exterior surface of the goethite was obtained by scanning electron microscopy (SEM, Hitachi S-4800, Japan).

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1.4. Experimental methods

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1.4.1. Pretreatment of soil aggregates with phosphorus

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Soil aggregate samples of 1.000 g were placed into 50 mL plastic tubes and shaken with 20 mL of 0, 5, 10, 15, 20, 40, 60, 80 and 200 mg/L KH2PO4 solution containing 0.01 mol/L KCl as the background electrolyte (initial pH (5.50 ± 0.02) and 3 drops of chloroform added to inhibit microbial growth), respectively, in a rotatory shaker (ZD-88-B, Bolaite Instrument

188 189

194 195 196 197 198

Aggregate samples of 1.000 g pretreated with 0–80 mg/L P were equilibrated with 20 mL of 65 mg/L aqueous Cu2+ solution containing 0.01 mol/L KCl as background electrolyte (initial pH 5.50 ± 0.02) in a rotatory shaker at 180 r/min and 25°C for 24 hr. The amount of Cu2+ adsorbed by soil aggregates was calculated by Eq. (1):

Q¼

3000

a

2500 2000 1500 1000 500 0 10

20

30

40

50

60

70

80

Degree (2θ)

Fig. 1 – X-ray diffraction (a) and scanning electron microscopy (b) of goethite.

ðCe −C0 ÞV W

200 201 202 203 204 205 206 207 208

211 212 213 214 215 216

ð1Þ

where, Q (mg/kg) is the amount of adsorbed Cu2+ at the equilibrium, Ce (mg/L) is the equilibrium concentration of Cu2+, C0 (mg/L) is the initial concentration of Cu2+, V (mL) is the volume of the solution used, and W (g) is the weight of the soil aggregate samples. Immediately following the adsorption of Cu2+, the residues were weighed to determine the amount of residual solution and were then resuspended in 20 mL of 0.01 mol/L KCl and left to equilibrate for 24 hr. The suspension was centrifuged and the concentrations of Cu2+ in the supernatants were measured. The amount of Cu2+ desorbed was calculated following the method used in the adsorption experiment. The 20 mL of different initial concentrations of Cu2+ (0, 10, 20, 40, 80, 120, 160 and 200 mg/L, respectively) were added to 1.000 g soil samples pretreated with 0, 5 and 200 mg/L P. The adsorption and desorption of Cu2+ were measured following the above the adsorption–desorption experiment.

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1.4.2. Adsorption–desorption of Cu2 + by P pretreated aggregate 209 particles 210

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Line (counts)

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1.3.2. Synthesis and characterization of goethite

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Company, China) at 180 r/min and 25°C for 24 hr. The equilibrated suspensions were centrifuged at 4000 r/min for 10 min. The supernatant was discarded. The centrifuged residues were washed with 95% ethanol (5 mL each time) until no P was detected, then air-dried and ground by glass rod for future use. The adsorbed P was calculated from the difference in solution P concentrations before and after equilibration. Point of zero charge (PZC) of the soil aggregates pretreated with P was determined by the potentiometric titration (Metrohm-848 Titrino plus, Switzerland) (Bernardo and Michael, 1972).

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(OM). Kaolinite (< 2 μm) was separated by sedimentation, dried at room temperature, homogenized and stored for later use.

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218 217 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234

1.4.3. Adsorption–desorption of Cu2 + on goethite, kaolinite and 235 Fed-removed aggregates 236 Phosphorus-pretreated goethite, kaolinite, and Fed-removed aggregates were obtained following the method of Section 1.4.1. The adsorption–desorption of Cu2+ was conducted according to the method of Section 1.4.2. Each mineral sample was 1.000 g with Cu2+ concentration of 65 mg/L pretreatment. The other conditions were similar to the above experiment. The experiment was repeated 3 times. The control experiment was carried out without P.

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1.5. Measurement methods

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The basic properties of soil aggregates were determined with the methods described by Lu (1999). The surface charges were measured using the Mehlich method (Mehlich, 1960). The PZC was assessed using the potentiometric titration method (Kingston et al., 1972). Available P was quantified by Mo-Sb colorimetric method (Ultraviolet–Visible Spectrophotometer,

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Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

238 239 240 241 242 243 244

247 248 249 250 251

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Table 1 – Basic properties of microaggregates.

18.80 42.25 29.53 9.42

252 253 254 255 256 257 258 259

5.80 6.05 5.81 6.02

± ± ± ±

0.01 0.02 0.05 0.05

36.32 25.72 28.64 46.94

± ± ± ±

0.18 0.41 0.05 0.08

Free iron oxide (g/kg) 29.02 14.34 19.21 32.01

Pierzynski 2000, Sweden). Concentrations of Cu2+ in solution were measured by atomic absorption spectrophotometry (AAS, Hitachi Z-2000, Hitachi, Japan). A standard Cu2+ solution (GSB G62024-90/2902) and a P solution (GSB G62008-90) with a concentration of 1000 μg/mL were used for quality control. The recovery percentage for Cu2+ was in a range of 92.3%– 105.1% and that for P 94.5%–102.3%. The basic properties of the samples are reported in Table 1.

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All data were processed using Microsoft Excel 2007 and statistical analyses were conducted using the software program, Origin Pro 8.5.1.

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2. Experimental results

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2.1. Effect of P pretreatments on surface charge of aggregates

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The surface potential of soil aggregates pretreated with the different amounts of phosphorus was listed in Fig. 2a. The adsorption of P on aggregates switched the surface potential from positive to negative, and caused a significant decrease in the PZC. The PZC was significantly negatively related to the P adsorption capacity (r > 0.98), indicating that the amount of the surface negative charge increased with increasing amount of P adsorbed. When the P concentrations increased from 0 to 120 mg/L, the PZC of coarse, fine, silt and clay fractions decreased from 5.22 to 2.73, 4.21 to 1.98, 4.65 to 2.28, and 4.93 to 2.71, respectively. According to the Nernst equation (Eq. (2)):

273 274 275 276 277 278

282 283 284 285 286 287 288 289 290 291 292 293 294

± ± ± ±

2.22 2.42 3.11 2.14

5.890 3.331 5.760 9.132

± ± ± ±

0.24 0.07 0.02 0.12

298 299 300

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Coarse sand fraction, r2 =0.9931 Fine sand fraction, r 2 =0.9658 Silt sand fraction, r2 =0.9861 Clay-sized fraction, r 2 =0.9952

1

0

0

200

400

600

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P adsorption (mg/kg) 40

b

0

ð2Þ

where, φ0 is surface potential; R, T and F are constants; PZC is the point of zero charge; pH is the one in the equilibrium solution. Surface potential (φ0) depends on PZC and equilibrium pH. At the equilibrium solution pH (4.5–4.8), which was higher than the PZC, the surface potential of all soil aggregates was thus negative after P adsorption, thereby facilitating cation adsorption on aggregates. Fig. 2b showed the surface potential (φ0) changes of aggregates over different amount of phosphorus adsorbed. As P adsorption amount increased, the z-potential (φ) of four soil aggregates decreased obviously and the symbol of φ0 changed from the positive to the negative. The surface potential and P adsorption showed a significant negative correlation (r > 0.98), suggesting that ligand exchanges of P anion with \OH2 or \OH on the surface of soil

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φ0 ¼ 2:303RT=F  ðPZC−pHÞ 280 279

21.40 16.69 15.36 47.32

2.2.1. Effect of P preadsorption on Cu2 + adsorption

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2.2. Effects of P pretreatments on Cu2+ adsorption and desorption on soil aggregates

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± ± ± ±

Surface negative charge amount (cmol/kg)

aggregates caused more negative charges on the aggregate 295 surface and thereby decreased the PZC and surface potential 296 (φ0) (Pérez-Novo et al., 2009). 297

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4.37 2.07 3.70 5.31

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1.6. Statistical analysis

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3.08 0.10 0.22 0.41

Cation exchange capacity (cmol/kg)

Different sizes of soil aggregates pretreated with different 301 concentrations of P (0–120 mg/L) showed similar Cu2+ adsorp- 302 tion curves at 65 mg/L of Cu2+ concentration (Fig. 3). The 303

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± ± ± ±

Free aluminum oxide (g/kg)

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Coarse (2.0–0.20) Fine (0.20–0.02) Silt (0.02–0.002) Clay (< 0.002)

Organic matters (g/kg)

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pH (H2O)

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Diameter (mm)

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PZC

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ϕ0 (mV)

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Coarse sand fraction, r2 =0.993 Fine sand fraction, r2 =0.9658 Silt sand fraction, r2 =0.9952 Clay-sized fraction, r2 =0.9861

-160 -200

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P adsorption (mg/kg) Fig. 2 – Points of zero charge (PZC) (a) and z-potentials (b) of the four fractions at various adsorption amounts of P. φ0: surface potential.

Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

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Clay-sized fraction Coarse sand fraction Silt sand fraction Fine sand fraction

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P adsorption (mg/kg)

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40

2+

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Equilibrium Cu concentration (mg/L)

160

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Cu2+ adsorption (mg/kg)

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Cu2+ adsorption (mg/kg)

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adsorption of P and Cu2+ by different fractions of aggregates (including ones pretreated with P) was closely related with free iron oxide, aluminum oxide and organic matter, and decreased in order: clay > coarse > silt > fine sand fractions. The amount of Cu2+ adsorption by soil aggregates showed rapid decrease, quick increase and then leveling off pattern as P adsorption increased. When the amount of adsorbed P was less than 260, 220, 130 and 110 mg/kg (corresponding to the P concentrations of 20, 20, 15 and 10 mg/L) for coarse, clay, silt and fine sand fractions, respectively, the corresponding Cu2+ adsorption by aggregates with P pretreatments was lower than those without P pretreatment. However, the Cu2+ adsorption by soil aggregates was greater with P pretreatment than without P pretreatments when the amount of P adsorption exceeded the above values. That is to say that the Cu2+ adsorption curves displayed a V-shaped change over P rates. The adsorption of Cu2+ by the aggregates was inhibited by P preadsorption at low amount of P, but promoted at higher levels of P (Fig. 3). When P preadsorption by the clay, coarse, silt and fine sand fractions was 170, 56, 52 and 43 mg/kg, the

Cu2+ adsorption (mg/kg)

304

P

Fig. 3 – Effects on the adsorption of Cu2+ by different adsorption amounts of P.

800

P5 P0 P200

400

0

0

100

Equilibrium Cu2+ concentration (mg/L)

200

1200

800

P5 P0 P200

400

0

0

d

2500 Cu2+ adsorption (mg/kg)

Cu2+ adsorption (mg/kg)

1200

Cu2+ adsorption was the lowest, being 1037, 804, 540 and 380 mg/kg, respectively, compared to 1120, 1060, 770 and 740 mg/kg without P preadsorption. The reduction was 7.4%, 24%, 30% and 48%, respectively. However, the soil aggregates pretreated with 120 mg/L had the greatest Cu2+ adsorption, which was increased by 11%, 6.7%, 18% and 39% for the clay, coarse, silt, and fine sand fractions, respectively, as compared with the control. Therefore, the greatest inhibitory or promoting effects of P preadsorption on Cu2+ adsorption occurred on the silt fraction, whereas P preadsorption had the least inhibition and promotion on Cu2+ adsorption on clay and coarse fractions, respectively. In order to further confirm the results above, another Cu2+ adsorption study was performed on the aggregates pretreated with lower P concentration (P 5 mg/L, the most inhibition) and higher P concentration (P 200 mg/L, the most promotion), respectively. A wider Cu2+ concentrations range (0–200 mg/L) was used. Compared with the control without P pretreatment, high P pretreatment significantly enhanced Cu2+ adsorption on the aggregates, while the low P pretreatment decreased Cu2+ adsorption on the aggregates (Fig. 4). Such promotion and inhibition were more obvious on the coarse fraction. As the Cu2+ concentrations increased, the promoting or inhibiting effects of P pretreatments on Cu2+ adsorption by soil aggregates became greater. Compared with the control, the amount of Cu2+ adsorption increased by 34.2%, 34.8%, 2.7%, and 22.6% under 200 mg/L (P200) pretreatment, but decreased by 17.7%, 7.1%, 5.8% and 5.9% under 5 mg/L pretreatment (P5), for coarse, silt, fine and clay sand fractions, respectively. Copper ion adsorption on soil aggregates with and without P pretreatments was fitted various adsorption isotherm models (Table 2). The Freundlich model was the best (r > 0.9805), indicating a multilayer adsorption of Cu2+ on soil aggregates. This was consistent with the results of previous studies (Srivastava et al., 2005; Jalali and Moharrami, 2007). Kf is a constant related to the adsorption capacity and adsorption intensity, n indicates the nonlinear degree or form of adsorption isotherms. Some scholars believe that the greater the constant, Kf, the stronger the adsorption of heavy metals on soil, and vice versa (Anderson and Christensen, 1988; Alloway, 1995). The Kf values of Cu2+ adsorption by the different soil aggregates with and without P pretreatments decreased in order: clay > coarse > silt > fine sand fractions (Table 2). For one kind of aggregate, Kf values at the different P pretreatments were high P > no P > low

100

Equilibrium Cu2+ concentration (mg/L)

200

2000 1500 1000

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500 0

0

30

60

90

Equilibrium Cu2+ concentration (mg/L)

120

Fig. 4 – Isothermal adsorption curves of Cu2+ by soil aggregates pretreated with different P concentrations. (a) Coarse sand fraction; (b) fine sand fraction; (c) silt sand fraction; (d) clay-sized fraction. P0: without P pretreatment; P5: 5 mg/L P pretreatment; P200: 200 mg/L P pretreatment. Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367

6 t2:1 t2:2 t2:3

t2:4

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Table 2 – Matching parameters of Cu2+ adsorption equation (Freundlich) under different concentration of phosphate in aggregates. Diameter (mm)

Untreated

t2:5

Treated with low concentrations of P

Treated with high concentrations of P

Kf

n

r

Kf

n

r

Kf

n

r

319.01 174.35 201.65 383.18

0.3976 0.4076 0.4462 0.4173

0.9945 0.9934 0.9853 0.9981

267.18 156.08 160.51 335.35

0.3679 0.3307 0.3405 0.4354

0.9980 0.9957 0.9970 0.9974

486.97 218.02 286.68 563.38

0.3807 0.4011 0.4113 0.4047

0.9946 0.9993 0.9895 0.9805

Coarse (2.0–0.20) Fine (0.20–0.02) Silt (0.02–0.002) Clay (< 0.002)

t2:11 t2:10

X: adsorption capacity (mg/kg), C: equilibrium concentration (mg/L), K, n: constant.

382 383 384 385 386 387 388 389 390 391

C

381

E

380

R

379

R

378

O

377

40

C

376

N

375

30

U

374

Desorption rate of Cu2+ (%)

373

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Heavy metals adsorbed onto soil components exist in distinct forms, showing various bioavailability or toxicity, and thus different risks to the environmental quality and human health. In this study, 0.02 mol/L KCl solution was selected to desorb Cu2+ from the samples. The desorbed Cu2+ was a part of the Cu2+ adsorbed by soil aggregates via electrostatic force, which was easily exchangeable (Galunin et al., 2014). The rate of Cu2+ desorption (the percentage of Cu2+ desorbed to the adsorption amount) indicates soil's capability of electrostatic adsorption. For P-treated soil aggregates, the shape of Cu2+ desorption rate curves was reverse to that of Cu2+ adsorption curves (Fig. 5). As P adsorption increased, the Cu2+ desorption rates increased rapidly at lower P adsorption stage, decreased sharply, and became flat evently. The desorption rates of Cu2+ from the coarse and clay fractions were generally low, being 9.0% and 5.7% at low P adsorption, increased to 14.6% and 13.1%, and then gradually dropped to 4.4% and 3.8%. The amount of adsorbed P corresponding to the Cu2+ desorption peaks was 56.0 mg/kg and 68.0 mg/kg for the coarse and clay fractions, respectively.

P

372

D

2.2.2. Effect of P preadsorption on Cu2+ desorption

E

371

369

The rates of Cu2+ desorption from the fine and silt sand fractions were higher, being 13.5% and 17.5% at low P adsorption, increased to 39.0% and 36.2%, and gradually dropped to 9.1% and 8.8%. The P adsorption corresponding to the Cu2+ desorption peaks was 43.0 for fine fraction and 53.0 mg/kg for silt sand fraction. These results indicated that P preadsorption by aggregates promoted Cu2+ desorption at lower P adsorption (116–140 mg/kg), and inhibited it at higher P adsorption amount. Fig. 6 showed the desorption rates of Cu2+ adsorbed by the soil aggregates pretreated with or without P. The desorption rates of Cu2+ increased with increasing concentrations of Cu2+ added. However, the Cu2+ desorption rates were different between the soil aggregates treated with two P concentrations. Compared with the control, the Cu2+ desorption rates for the coarse, silt, fine, and clay fractions were increased by up to 19.4%, 25.0%, 28.6%, and 11.4%, respectively, under high concentration of P, but decreased by 37.8%, 20.4%, 22.3%, and 25.8%, under low concentration of P.

T

370

P. This showed that the Cu2+ adsorption capacity was increased by the high concentrations of P, but decreased by low concentrations of P pretreatment.

368

O

F

t2:6 t2:7 t2:8 t2:9

20

Coarse sand fraction Silt sand fraction Fine sand fraction Clay-sized fraction

10

0

300

600

900

1200

P adsorption (mg/kg) 2+

Fig. 5 – Effects on the desorption of Cu amounts of P.

by different adsorption

392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410

2.3. Effects of P pretreatments on Cu2+ adsorption by soil 411 minerals and Fed-removed soil aggregates 412 To further investigate the mechanisms of Cu2+ adsorption suppression by low concentrations of P, the enhancements by high concentrations of P, soil minerals, goethite and kaolinite, which play an important role in P and Cu2+ adsorption, and Fed-removed soil aggregates, were employed to examine the effects of P pretreatment on Cu2+ adsorption. The secondary adsorption of Cu2+ by minerals and Fed-removed soil aggregates pretreated with different P concentrations was shown in Fig. 7. The low concentrations of P suppressed but the high concentrations of P promoted the Cu2+ adsorption, displaying a V-shaped variation of Cu2+ adsorption over P concentrations. This phenomenon was more obvious on goethite. Our preliminary experiment showed that goethite had much higher P adsorption capacity than others did. Compared with no-P pretreatment, the Cu2+ adsorption on goethite was inhibited by P when P adsorption ranged from 98 to 1450 mg/kg, but enhanced when the amount of adsorbed P was higher than 1450 mg/kg. However, the suppression of Cu2+ adsorption by P preadsorption was observed neither on kaolinite (Fig. 7b) nor on Fedremoved soil aggregates (Fig. 7c). Their Cu2+ adsorption capacities increased with increasing P amount. The previous studies have shown that cation exchange capacity of kaolinite obtained

Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

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P0 P5 P200

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439 440 441 442 443 444 445 446

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3. Discussion

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3.1. Effects of P pretreatments on Cu2+ adsorption and desorption

451

Most of previous studies have showed that the adsorption of Cu2+, Zn2+ and Cd2+ or other heavy metals by soils is enhanced significantly after pretreatments with phosphate, because the ligand exchange of P anion with \OH2 or \OH on soil aggregates causes increases in the negative charges the surface of soil aggregates (Pérez-Novo et al., 2011a, 2011b; Tiberg et al., 2013), and thus decreases in PZC and surface potential (φ0) and even a reverse in the nature of soil surface

457 458

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Cu2+ adsorption (mg/kg)

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charge, resulting in increased electrostatic adsorption of Cu2+ on soils (Pérez-Novo et al., 2009). Moreover, the specific adsorption could occur on the surface of soil aggregates, forming n+ complexes such as S-POn− (soil–phosphate–metal) ternary 4 -M surface complex (Agbenin, 1998; Bolan et al., 1999) and thereby increasing the number of active sites for Cu2+ adsorption (Yu et al., 1996; Bolan et al., 2003; Pardo, 2004). Tiberg (Tiberg et al., 2013) also found that P preadsorption significantly increased the secondary adsorption capacity of Cu2+ and lead (II) on ferrihydrite. However, the present results also showed that the Cu2+ adsorption by soil aggregates displayed a V-shape change over P pretreatment concentrations (initial decline followed by rise). The Cu2+ adsorption by soil aggregates was promoted by P pretreatments only when P preadsorption was higher than 110 mg/kg; whereas it was inhibited when P preadsorption was lower than that amount, compared to the control. The Cu2+ desorption showed just opposite pattern to its adsorption (Figs. 4 and 6). The P adsorption capacity, PZC, Cu2+ adsorption and desorption amount of the aggregates pretreated with 0–120 mg/L P were shown in Table 3. It could be clearly seen that PZC decreased with the increases in P adsorption, while Cu2+ adsorption showed an initial decrease followed by gradual increase. However, Cu2+ desorption ratio first increased but then decreased. We also tried to adsorb P using the aggregate samples pretreated with different concentrations of Cu2+, and

D

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from Ubulu-Ukwu, Delta state of Nigeria, significantly increased after the modification with sodium dihydrogen phosphate and sodium tripolyphosphate (Adebowale et al., 2006; Unuabonah et al., 2007). Compared with untreated soil aggregates, the Cu2+ adsorption by Fed-removed soil aggregates significantly reduced. Similar results were observed by Wang et al. (2009). By comparing Fig. 7a with Fig. 7b, it was found that the P and Cu2+ adsorption by kaolinite was much less than that by goethite. Therefore, goethite was the main component responsible for P-induced inhibition or enhancement of Cu2+ adsorption by soils. Whether organic matter and other minerals have such effects needs further research.

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Fig. 6 – Desorption rates of Cu2 + by soil aggregates pretreated with different P concentrations. (a) Coarse sand fraction; (b) fine sand fraction; (c) silt sand fraction; (d) clay-sized fraction.

150

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500

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P adsorption (mg/kg)

Fig. 7 – Effects on the adsorption amount of Cu2+ by goethite (a), kaolinite (b) and Fed-removed fractions (c) pretreated with different P concentrations. Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484

8

t3:5

963.1 571.5 927.5 1005 1013.8 1054.8 1077.9 1100

R O

17.5 36.2 13.4 12.2 11.4 10.7 9.9 8.8

O

F

0.0 68.0 142.0 170.9 361.3 639.6 894.5 1130.0

4.93 4.67 4.50 4.45 4.11 3.48 2.86 2.71

1123.3 1088.9 1037.9 1109.2 1129.9 1199 1239.9 1247

5.7 13.1 5.6 4.7 4.4 4.4 4.0 3.8

found the phenomenon that P adsorption on soil aggregates was suppressed by Cu2+ pretreatments at low but enhanced at high Cu2+ concentrations. This suggested that the test result was not an accidental phenomenon. The inhibition or promotion of Cu2+ adsorption by P preadsorption was more prominent on goethite. This is different from the previous studies. It is because the previous studies used the relatively higher phosphate concentrations. The concentrations of phosphorus were usually greater than 100 mg/L and the adsorption capacities of P were over 450 mg/kg (Pérez-Novo et al., 2009; Wang and Xing, 2002), much higher than the critical value of inhibition or promotion obtained in the present experiment (110 mg/kg). In fact, the field use of P fertilizer was mostly less than 110 mg/kg. For example, the highest amount of P fertilizer in paddy soil was 75 kg/ha in Tai Lake region after the 1980s, corresponding to 5 mg/kg (Jiao et al., 2007). So our results would be of more practical significance for understanding the P fertilizer impacts on heavy metals in paddy soils.

E T C

E

R

R

486 487 488 489 490 491 492 493 494 495 Q5 496 497 498 499 500 501 502 503

P

The data also showed that Cu2+ adsorption on soil aggregates was suppressed by P pretreatments at low but enhanced at high P concentrations. Such phenomenon was very prominent on goethite. It appeared neither on Fed-removed soil aggregates, nor on kaolinite mineral (Fig. 7a), which suggested that goethite had greater adsorption ability than hematite and kaolinite, and might be one of the main carriers of P and Cu2+ in soils. Furthermore, goethite might be the main substance responsible for low-P suppressing but high-P promoting effects on Cu2+ adsorption. Li et al. (2006) found that P pretreatments suppressed Cu2+ secondary adsorption on goethite at low concentrations of P. the research has suggested that P is mainly adsorbed on sites in the inner-sphere of hematite and occupies the adsorption sites for Cu2+ at low P concentrations pretreatment. Both competitive adsorption and steric hindrance thus suppress the Cu2+ adsorption. With increasing amount of P, P adsorption might occur on the surface of hematite after the saturation of the inner-sphere of hematite by P (Perassi and Borgnino, 2014), thereby causing changes in the surface chemical properties of the mineral. The P adsorption generates the stronger specific adsorption sites for Cu2+ on the hematite surfaces, and P also plays a bridge role between the hematite surface and Cu2+ by forming ternary surface 2+ complex such as S–L–Mn+ (L was PO3− 4 ), thus enhancing Cu adsorption (Agbenin, 1998; Bolan et al., 1999; Galunin et al., 2014). Moreover, P anions specifically adsorbed into the inner of the electric double layer of colloids could increase the negative charges on colloidal surface but decrease PZC, facilitating the electrostatic adsorption of positively charged Cu2+ (Pérez-Novo et al., 2009), and thus increasing the adsorption of Cu2+. The desorption of Cu2+ on soil aggregates and goethite was just opposite to its adsorption, showing that the low concentrations of P promoted but high concentrations of P reduced the Cu2+ desorption. In addition, Antelo et al. (2010) reported that the specifically adsorbed P via anionic ligand exchange has formed ternary

D

4.65 4.51 4.28 4.19 3.98 3.21 2.73 2.28 0.0 53.0 117.0 142.0 295.3 593.6 866.0 1074.0

O

485

3.2. Mechanism analysis of phosphate pretreatment effect on 504 Cu2+ adsorption 505

13.6 39.0 17.1 11.2 11.3 11.6 10.2 9.1 741.4 383.5 514.2 765.8 755.9 782.1 839.8 876 4.51 4.15 4.02 3.79 3.40 2.66 2.37 1.98 0.0 43.0 94.0 136.0 271.3 552.6 734.5 995.0 9.0 14.6 7.4 6.5 5.8 5.5 4.6 4.4 1059.8 804.5 1006.8 1076.2 1095.7 1101.7 1112 1130 5.22 4.99 4.83 4.63 4.44 3.65 3.22 2.73 0 56.0 118.0 177.9 324.3 622.6 843.0 1123.0 0 5 10 15 20 40 80 120 t3:6 t3:7 t3:8 t3:9 t3:10 t3:11 t3:12 t3:13

N

C

Cu2+ P adsorption PZC Cu2+ Cu2+ P adsorption PZC Cu2+ Cu2+ P adsorption PZC Cu2+ Cu2+ P adsorption PZC Cu2+ adsorption desorption capacity adsorption desorption capacity adsorption desorption capacity adsorption desorption capacity capacity rate (%) (mg/kg) capacity rate (%) (mg/kg) capacity rate(%) (mg/kg) capacity rate(%) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg)

Clay (<0.002 mm) Silt (0.02–0.002 mm) Fine (0.20–0.02 mm)

t3:3 t3:2 t3:4

P concentration (mg/L)

U

Coarse (2.00–0.20 mm)

t3:1 Q6 Table 3 – P adsorption capacity, Point of zero charge (PZC), Cu2+ adsorption capacity and Cu2+ desorption rate on soil aggregates after P pretreatment.

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Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

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environment owing to increase adsorption-holding capacity 600 of heavy metals, and reduce their bioavailability and environ- 601 mental mobility. 602

surface complexes, such as S–O–PO3H (S is the adsorption sites on soil colloids) monodentate complex or S–O–PO2–O–S bidentate complex, with soil colloids. In investigating the forms of P adsorbed on goethite by XPS (Imaging Photoelectron Spectrometer), Liu et al. (1994) have found that there are two similar chemical states on the goethite surface, namely monodentate complex and bidentate complex with mutual transformation:

Acknowledgments

604 603

This work was supported by the Science and Technology 605 Support Plan Program of Jiangsu Province (No. BE 2013711). 606

551 552 553 554

O

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The effects of adsorption and desorption of Cu2+ by the paddy soil aggregates were different under different P concentrations pretreated. The Cu2+ adsorption was reduced on soil aggregates pretreated with low levels of P, but promoted with high amount of P, showing a V-shaped change over P concentrations. Moreover, the promoting or inhibiting effects of P pretreatments on Cu2+ adsorption by the soil aggregates enhanced with increasing Cu2+ concentrations. The Cu2+ desorption curves was just opposite to its adsorption. Similar effects of P pretreatments on Cu2+ adsorption and desorption were observed on goethite, but not on kaolinite and Fedremoved soil fractions. These findings indicated that goethite was one of the main substances responsible for P-induced suppression or facilitation of adsorption of Cu2+ in soils. It is necessary to investigate the appropriate rates of P fertilizers when P is used as an immobilizing agent of soil heavy metals as low amount of P fertilizers. The excessive P utilization may increase the risks of heavy metals to the

569 570 571 572 573 574 575 576 577 578

583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599

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4. Conclusions

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When solution pH decreased, monodentate complexes increased, while bidentate surface complexes reduced (Zhong et al., 2007). At the same pH, bidentate surface complexes were the main species at low P concentrations. Increasing P would change the main species from bidentate to monodentate, leading to the dominance of the monodentate species at high P concentrations (Liu et al., 1997). Both complexes have great differences in morphological stability and Cu2+ adsorption. Compared with a monodentate complex, a bidentate complex has one less P\OH bond but one more Fe\O bond, and it thus decreases the adsorbing sites for Cu2+, thereby suppressing the adsorption of Cu2+ at low P concentrations. However, the P on goethite was present as bidentate complexes at high concentrations of P, thus increasing the number of \OH on the goethite surface and the Cu2+ adsorption. The effects of P pretreatments on Cu2+ adsorption and desorption on soil aggregates is the net results of the competitive effect, the bridge bonding effect and the electrostatic effect (Leleyter and Probst, 1999). The mechanisms of P preadsorption on Cu2+ adsorption and desorption and the structure of S–L–Mn+ complex need further investigation by EXAFS (Extended X-ray Absorption Fine Structure) or other technologies.

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Adebowale, K.O., Unuabonah, I.E., Olu-Owolabi, B.I., 2006. The effect of some operating variables on the adsorption of lead and cadmium ions on kaolinite clay. J. Hazard. Mater. 134 (1–3), 130–139. Agbenin, J.O., 1998. Phosphate-induced zinc retention in a tropical semi-arid soil. Eur. J. Soil Sci. 49 (4), 693–700. Alloway, B.J., 1995. Heavy Metal in Soils. Springer Science & Business Media, London. Anderson, P.R., Christensen, T.H., 1988. Distribution coefficients of Cd, Co, Ni, and Zn in soils. J. Soil Sci. 39 (1), 15–22. Antelo, J., Fiol, S., Pérez, C., Mari, O.S., Arce, F., Gondar, D., et al., 2010. Analysis of phosphate adsorption onto ferrihydrite using the CD-MUSIC model. J. Colloid Interface Sci. 347 (1), 112–119. Arias, M., Pérez-Novo, C., Osorio, F., López, E., Soto, B., 2005. Adsorption and desorption of copper and zinc in the surface layer of acid soils. J. Colloid Interface Sci. 288 (1), 21–29. Basta, N.T., Ryan, J.A., Chaney, R.L., 2005. Trace element chemistry in residual-treated soil: key concepts and metal bioavailability. J. Environ. Qual. 34 (1), 49–63. Bernardo, V.R., Michael, P., 1972. Electrochemical properties of some oxisols and alfisols of the tropics. Soil Sci. Soc. Am. J. 36, 587–593. Bolan, N.S., Naidu, R., Khan, M., Tillman, R.W., Syers, J.K., 1999. The effects of anion sorption on sorption and leaching of cadmium. Aust. J. Soil Res. 37 (3), 445–460. Bolan, N.S., Adriano, D.C., Duraisamy, P., Mani, A., Arulmozhiselvan, K., 2003. Immobilization and phytoavailability of cadmium in variable charge soils. I. Effect of phosphate addition. Plant Soil 250 (1), 83–94. Das, N., 2010. Recovery of precious metals through biosorption—a review. Hydrometallurgy 103 (1–4), 180–189. Fischer, L., Muhlen, E.Z., Brummer, G.W., Niehus, H., 1996. Atomic force microscopy (AFM) investigations of the surface topography of a multidomain porous goethite. Eur. J. Soil Sci. 47 (3), 329–334. Galunin, E., Ferreti, J., Zapelini, I., Vieira, I., Ricardo Teixeira Tarley, C., Abr, O.T., et al., 2014. Cadmium mobility in sediments and soils from a coal mining area on Tibagi River watershed: environmental risk assessment. J. Hazard. Mater. 265, 280–287. Garrido, F., Illera, V., Campbell, C.G., Garcia-Gonzalez, M.T., 2006. Regulating the mobility of Cd, Cu and Pb in an acid soil with amendments of phosphogypsum, sugar foam, and phosphoric rock. Eur. J. Soil Sci. 57 (2), 95–105. Huang, H.G., Li, T.Q., Gupta, D.K., He, Z.L., Yang, X.E., Ni, B.N., et al., 2012. Heavy metal phytoextraction by Sedum alfredii is affected by continual clipping and phosphorus fertilization amendment. J. Environ. Sci. 24 (3), 376–386. Jalali, M., Moharrami, S., 2007. Competitive adsorption of trace elements in calcareous soils of western Iran. Geoderma 140 (1–2), 156–163. Jiao, S.J., Hu, X.M., Pan, G.X., Zhou, H.J., Xu, X.D., 2007. Effects of fertilization on nitrogen and phosphorus run-off loss from Qingzini paddy soil in Taihu Lake region during rice growth season. Chin. J. Ecol. 26, 495–500.

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REFERENCES

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Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

60 7 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661

10

C

O

R

R

E

C

T

E

D

P

R O

O

F

Pérez-Novo, C., Bermúdez-Couso, A., López-Periago, E., Fernández-Calviño, D., Arias-Estévez, M., 2009. The effect of phosphate on the sorption of copper by acid soils. Geoderma 150 (1-2), 166–170. Pérez-Novo, C., Bermúdez-Couso, A., López-Periago, E., Fernández-Calviño, D., Arias-Estévez, M., 2011a. Zinc adsorption in acid soils: influence of phosphate. Geoderma 162 (3-4), 358–364. Pérez-Novo, C., Fernández-Calviño, D., Bermúdez-Couso, A., López-Periago, J.E., Arias-Estévez, M., 2011b. Influence of phosphorus on Cu sorption kinetics: stirred flow chamber experiments. J. Hazard. Mater. 185 (1), 220–226. Raicevic, S., Kaludjerovic-Radoicic, T., Zouboulis, A.I., 2005. In situ stabilization of toxic metals in polluted soils using phosphates: theoretical prediction and experimental verification. J. Hazard. Mater. 117 (1), 41–53. Schwertmann, U., Cornell, R., 1991. Iron Oxides in the Laboratory: Preparation and Characterization. Wiley-VCH, Weinheim, Germany. Srivastava, P., Singh, B., Angove, M., 2005. Competitive adsorption behavior of heavy metals on kaolinite. J. Colloid Interface Sci. 290 (1), 28–38. Stemmer, M., Gerzabek, M.H., Kandeler, E., 1998. Organic matter and enzyme activity in particle-size fractions of soils obtained after low-energy sonication. Soil Biol. Biochem. 30, 9–17. Tiberg, C., Sj Stedt, C., Persson, I., Gustafsson, J.P., 2013. Phosphate effects on copper(II) and lead(II) sorption to ferrihydrite. Geochim. Cosmochim. Acta 120 (0), 140–157. Unuabonah, E.I., Olu-Owolabi, B.I., Adebowale, K.O., Ofomaja, A.E., 2007. Adsorption of lead and cadmium ions from aqueous solutions by tripolyphosphate-impregnated kaolinite clay. Colloids Surf. A Physicochem. Eng. Asp. 292 (2–3), 202–211. Van Rotterdam, A.M.D., Bussink, D.W., Temminghoff, E.J.M., Van Riemsdijk, W.H., 2012. Predicting the potential of soils to supply phosphorus by integrating soil chemical processes and standard soil tests. Geoderma 189-190 (11), 617–626. Wang, K., Xing, B., 2002. Adsorption and desorption of cadmium by goethite pretreated with phosphate. Chemosphere 48 (7), 665–670. Wang, F., Pan, G.X., Li, L.Q., 2009. Effects of free iron oxyhydrates and soil organic matter on copper sorption–desorption behavior by size fractions of aggregates from two paddy soils. J. Environ. Sci. 21 (5), 618–624. Yu, T.R., Ji, J.L., Ding, C.P., 1996. Electrochemistry of Variable-Charge Soils. Science Press, Beijing. Zhao, K., Selim, H.M., 2010. Adsorption–desorption kinetics of Zn in soils: influence of phosphate. Soil Sci. 175 (4), 145–153. Zhong, B., Stanforth, R., Wu, S., Chen, J.P., 2007. Proton interaction in phosphate adsorption onto goethite. J. Colloid Interface Sci. 308 (1), 40–48.

N

762

Kingston, F.J., Posner, A.M., Quirk, J.P., 1972. Anion adsorption by goethite and gibbsite. 1. The role of the proton in determining adsorption envelopes. J. Soil Sci. 23, 177–193. Kumpiene, J., Lagerkvist, A., Maurice, C., 2007. Stabilization of Pb-and Cu-contaminated soil using coal fly ash and peat. Environ. Pollut. 145 (1), 365–373. Leleyter, L., Probst, J., 1999. A new sequential extraction procedure for the speciation of particulate trace elements in river sediments. Int. J. Environ. Anal. Chem. 73, 109–128. Li, W., Zhang, S., Jiang, W., Shan, X., 2006. Effect of phosphate on the adsorption of Cu and Cd on natural hematite. Chemosphere 63 (8), 1235–1241. Li, X., Lu, J., Lu, J., Chen, F., 2007. Effect of the combined application of N and P fertilizer on yield and nutrients uptake of ryegrass. J. Huazhong Agric. Univ. 26 (2), 195–199. Liu, F., He, J., Li, X., Xu, F., He, H., 1994. The concentration of P and chemistry status of P adsorbed on geothite surface. Chin. Sci. Bull. 39, 1996–1999. Liu, F., Ji, X., He, J., Li, X., Zhou, D., Xu, F., 1997. Coordination forms and transformations of phosphate adsorbed by goethite surface on different pH. Acta Pedol. Sin. 34, 367–374. Lu, R.K., 1999. Chemistry Analytical Methods on Soil Agricultural. China Agricultural Science and Technology Press, Beijing. Luo, L., Ma, Y., Zhang, S., Wei, D., Zhu, Y., 2009. An inventory of trace element inputs to agricultural soils in China. J. Environ. Manag. 90 (8), 2524–2530. Ma, L.Q., Santos, J., Cao, X., Saha, U., Harris, W., 2008. Field application of phosphate rock for remediation of metal contaminated soils. Florida Institute of Phosphate Research, Project Number: 97-01-148R, Final Report. Mehlich, A., 1960. Charge Characterization of Soils. Transactions 7th Int. Congr. Soil Sci 88 (2) pp. 292–302. Mirlean, N., Baisch, P., Medeanic, S., 2009. Copper bioavailability and fractionation in copper-contaminated sandy soils in the wet subtropics (southern Brazil). Bull. Environ. Contam. Toxicol. 82 (3), 373–377. Nelson, H., 2012. Modelling Precipitation and Surface Complexation Reactions in Systems with Goethite, Cu(II) and Oxyanions Containing As(V) or P(V). (Doctoral thesis). Umeå University, Sweden. Pardo, M.T., 2004. Cadmium sorption–desorption by soils in the absence and presence of phosphate. Commun. Soil Sci. Plant Anal. 35 (11–12), 1553–1568. Peltovuori, T., Soinne, H., 2005. Phosphorus solubility and sorption in frozen, air-dried and field-moist soil. Eur. J. Soil Sci. 56 (6), 821–826. Perassi, I., Borgnino, L., 2014. Adsorption and surface precipitation of phosphate onto CaCO3–montmorillonite: effect of pH, ionic strength and competition with humic acid. Geoderma 232-234, 600–608.

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Please cite this article as: Dai, J., et al., Adsorption and desorption of Cu2 + on paddy soil aggregates pretreated with different levels of phosphate, J. Environ. Sci. (2016), http://dx.doi.org/10.1016/j.jes.2016.06.037

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