Access the full text.
Sign up today, get DeepDyve free for 14 days.
Loading next page...
/lp/de-gruyter/nh-4-adsorption-and-adsorption-kinetics-by-sediments-in-a-drinking-N32FZUkpqz
- Publisher
- de Gruyter
- Copyright
- Copyright © 2016 by the
- ISSN
- 2083-4810
- eISSN
- 2083-4810
- DOI
- 10.1515/aep-2016-0039
- Publisher site
- See Article on Publisher Site
Abstract
The sorption isotherm and sorption kinetics of NH4+ by the Fen River reservoir sediment were investigated for a better understanding of the NH4+ sorption characteristics and parameters. The results showed that Q (adsorption content) increased with the increase of Ceq (equilibrium concentration), sorption isotherms could be described by Freundlich equation (R2 from 0.97 to 0.99). Cation exchange capacity (CEC) had a significant correlation with the parameters K and n (R2 was 0.85 and 0.95, respectively). The ENC0 (Ceq as Q was zero) of S1, S2, S3 and S4 was 1.25, 0.57, 1.15 and 1.14 mg L-1, respectively, and they were less than the NH4+ concentrations in reservoir water. The sediments released NH4+ to the Fen River reservoir water and acted as a pollution source, in the form of complex and heterogeneous adsorbents. The NH4+ adsorption kinetic process was composed of `fast' and `slow' reaction patterns and could be fitted using both Elovich equation and Pseudo second-equation. More than one-step may be involved in the NH4+ sorption processes, and interior diffusion was not dominant ion action. Introduction Nitrogen is one of the most important nutrients for plant growth. In recent years, the fertilizer has been excessively applied for plant growth and economic benefit. However, these behaviors usually lead to much fertilizer losses and soil erosion, and then give rise to serious environmental problems (Brankov et al. 2012; Darvishi et al. 2016). NH4+ is usually found in aqueous environments, which is the major component among the nitrogen-contaminating compounds in lakes or rivers and is produced in sediments during the decomposition of organic matter by various heterotrophic organisms (Machin and Aller 1984). After NH4+ release to solution by the processes of air stripping, chemical treatment, selective ion exchange and biological nitrification-denitrification (Metcalf 2003, Kelly 1996, de-Bashan et al. 2004), it also can be reoxidized, reincorporated into organisms, adsorbed onto particles, migrate to other parts of the sediments, can be diffused along concentration gradients to other regions of the sediment or to the overlying water. Sediments usually act as a sink for ammonium. However, under certain conditions, the sediments may act as a source and support the trophic status of the lake ecosystem (Zhou et al. 2001, Kaiserli et al. 2002). When present in extremely high concentrations, NH4+ may also be a constituent of authigenic minerals (Martens et al. 1978). Physical chemistry of adsorption and desorption are fundamental and important processes for element transference, and have obviously effect on the content of a nutrient. Reservoir plays a special role in society and people's life, the water and sediment of reservoir directly affect the water quality and ecological environment, as well as human's physical health. Therefore, studies on adsorption and desorption characteristics are significant for the understanding of the role of sediments in the biogeochemical cycling of ammonium in shallow lakes and reservoirs. The objective of this study was to investigate NH4+ adsorption isotherm of the sediments from the Fen River reservoir, to calculate collected parameters and analyze the adsorption characteristics, and understand the kinetics process of NH4+ adsorption. Materials and methods Study area The Fen River reservoir is a subtropical reservoir located at 38°0259N and 111°5458E in Shanxi Province, China. It was formed by damming of the Fen River in 1958. The reservoir has a maximum storage capacity of 7.0×108 m3, controlling 5268 km2 upstream areas, and it could irrigate 90×103 ha fields. The upstream area of the Fen River reservoir consists of loess hilly gully region, soils in this area are impoverished and easily eroded. The area experiences a typical continental monsoon climate, the mean annual precipitation is 456 mm and the mean annual temperature is 9.5ºC. The concentration of NH4+ in the reservoir was higher than in the river, which was 0.150.18 mg L-1 and 0.120.16 mg L-1 respectively. Methods In this study, four sediment samples S1, S2, S3 and S4 were taken from the Fen River reservoir using a special messenger-activated core-sampler (ETC-200) in August, 2014 (Fig 1). Water depth of the sample stations was 5 m for S1 and S3, and 7 m for S2 and S4, respectively. The collected samples were stored in an icebox and transported immediately to the laboratory, and then centrifuged for 10 min at 5,000 rpm to remove most of the water. Subsequently the samples were air dried, passed through a 100 mesh sieve and stored at 4ºC. Sediment pH was measured in distilled water (w/v ratio of 1:2.5). NH4+ was extracted with 2 mol L-1 KCl and measured by indigotin spectrophotometry. Total nitrogen (TN) was measured by Kjeldahl apparatus (Kjelflex k-360) after digestion with sulphuric acid (H2SO4). Total phosphorus (TP) content was determined using the molybdenum-blue complex method after extraction with HClO4/H2SO4 at 370ºC (Krom et al. 1981). The organic matter (OM) was measured by the dichromate volumetric method. Cation exchange capacity (CEC) was measured by ammonium acetate exchanging method. Particle size distribution of the sediment was determined using the hydrometer method (Bouyoucos 1951). The sediments characteristics are depicted in Table 1. For NH4+ adsorption experiment, 0.5 g sediment samples were loaded into a series of 50 mL tubes, then 25 mL NH4Cl solution in concentrations of 0, 0.5, 1, 2, 5, 10, 15, 20, 30 and 50 mg L-1, respectively, was injected, two drops of toluene (0.1% chloroform) were added to restrict microbial activity. After shaking at 250 rpm on an orbital shaker at 25ºC for 24 h, suspensions were centrifuged at 3,500 rpm for 10 min. Then the supernatants were filtered through a 0.45 m filter membrane. The NH4+ concentration (Ceq) in the supernatant solution was determined by the salicylate-hypochlorous acid spectrophotometric method using UV-750. The adsorbed amount of NH4+ by the sediment was calculated by the difference between Co and Ceq. The formula (1) was: Q = ( C o - C eq ) × v w (1) Where, Q is the sorbed amount (mg kg-1), Co is the initial NH4+ concentration (mg L-1), Ceq is the equilibrium concentration (mg L-1), w is the sample weight (g), and v is the solution volume (mL) of NH4Cl. For adsorption kinetics, 0.5 g samples were loaded into a series of 50 ml polyethylene centrifuge tube, then mixed with 25 mL NH4Cl solution of 2 mg L-1 that was selected as near the grade five of water in China (2 mg L-1 for lake and reservoir). Two drops of toluene (0.1% chloroform) were also added to restrict microbial activity. The centrifuge tubes were capped and shaken at 250 rpm on an orbital shaker at 25ºC for different times range from 0 to 720 min (5, 15, 30, 60, 120, 240, 720 min). After shaking, the suspensions were centrifuged and the supernatants were filtered in accordance with the above method. The NH4+ concentration (Ceq) in the supernatant and the adsorbed amount by the sediment was determined and calculated as described by the method of NH4+ adsorption experiment. All data were the mean values of three replicates. The Office Excel and SPSS 13.0 software were used for calculation and statistical analysis, and Origin 8.0 was used to fit curves and calculate parameters. Results and discussion NH4+ adsorption isotherm and related parameters The adsorption isotherms were one of the most important data to understand the mechanism of the adsorption systems. Fig. 1. Map of sampling sites at the Fen River reservoir Table 1. Sediment characteristics S1 pH NH4 (mg kg) S2 7.28±0.18 15.01±3.21 436.72±18.46 648.25±19.76 350.02±20.15 67.01±6.71 25.72±5.32 34.53±4.53 39.75±3.28 S3 7.36±0.22 26.72±1.96 370.04±25.30 581.61±24.32 427.93±16.87 59.56±5.48.62 29.58±5.46 36.02±5.32 34.4±3.25 S4 7.4±0.16 24.36±2.36 398.45±27.18 742.35±22.34 406.72±20.13 52.39±7.23 27.46±3.25 33.56±4.32 38.98±2.33 7.45±0.23 28.07±2.41 415.42±20.32 842.84±28.14 415.55±17.62 54. 54±8.64 26.39±4.32 35.23±3.25 38.38±2.56 TN (mg kg) TP (mg kg) OM (mg kg) CEC (cmol kg) Sand (%) Silt (%) Clay (%) H. Sun, X. Wang The adsorbed NH4+ was negative while Ceq was less than a specific value (Fig. 2). It demonstrated that sediments released NH4+. Therefore, when the adsorbed NH4+ was zero, it was considered important and it has a special meaning. Similar to the report by Zhou et al. (2005), we called the Ceq adsorption/desorption equilibrium concentration (ENC0) while the adsorbed NH4+ was zero, in other words when Cep is lower than ENC0 sediments will release NH4+, otherwise they will adsorb NH4+. The ENC0 values in Fig. 2 were 1.25, 0.57, 1.15 and 1.14 mg L-1 respectively for S1, S2, S3 and S4. This indicates that S2 was easier adsorbing NH4+ than S1, S3 and S4. The NH4+ concentrations were ranged from 0.120.15 mg L-1 in the Fen River reservoir, more than the concentration in rivers, and less than ENC0. Therefore, the sediments in the Fen River reservoir released NH4+ to reservoir water and acted as a pollution source, according to the comparison of values of NH4+ concentration in reservoirs and rivers It was reported that EPC0 has a positive relationship with NAP (native adsorbed phosphorus) (Aminot and Andrieux 1996) in sediment (Zhou et al. 2005, Aminot and Andrieux 1996). There was a similar relationship (R2=0.97) between ENC0 and NH4+ in sediments. As a result, we could estimate the ENC0 value from the NH4+ content, furthermore we could judge roles sediment played in water by comparing the values of ENC0 and NH4+ concentration. The relationship between CEC and parameter K or n, and the correlation between OM and K are showed in Fig. 3, CEC being positively related to the K (R2=0.85) and negatively related to n (0.95). CEC was a very important parameter that influenced the NH4+ adsorption extent and the degree of nonlinearity of adsorption process. The diversity of K and n suggested differences in the extent of the adsorption and the degree of nonlinearity. K had a negative relationship with OM of the sediments (R2=0.68). It indicated that organic material may have a diluting effect on the exchange capacity in finegrained sediments, and that organic coatings may block ion exchange sites on clay surfaces (Holmboe and Kristensen 2002). Adsorption kinetics NH4+ adsorption process was a complex kinetic process. The contents of adsorbed NH4+ increased rapidly over the first 120 min and then exhibited slow increases over the remainder of the experiment (Fig. 4 left). This `fast' and `slow' adsorption patterns indicated that significant adsorption occurs after the first 2 h, which was similar with the previous report (Morin and Morse 1999). The mechanism of adsorption depended on the physical and/or chemical characteristics of the adsorbent as well as on the mass transport process. In order to investigate the mechanism of adsorption, the pseudo-first-order kinetics model, the pseudo-second-order kinetics model, Elovich model and the intra-particle diffusion model were usually used to analyze and model these dynamical adsorption data. However, in the present study, the sediment NH4+ adsorption kinetics in the Fen River reservoir was found to conform to Elovich equation. The equations were as follows: Elovich equation: Q = + ln t Pseudo first-equation: ln(qe - qt ) = ln qe - k1t (3) (4) Langmuir and Freundlich adsorption isotherms were two important isotherms which were usually used in the sediment-water system (Hou et al. 2003). The present study showed that the NH4+ adsorption by sediments from the Fen River reservoir fitted to the Freundlich adsorption isotherm and did not fit to the Langmuir isotherm within the controlled range of NH4+ concentration in the overlying water during the simulation experiment. Freundlich isotherm: Q = K Ceq 1/ n (2) Where Q (mg kg-1) was the adsorption amount; Ceq was the equilibrium concentration in the overlying water (mg L-1); K (L kg-1) and n was constants, being indicative of the extent of the adsorption and the degree of nonlinearity between solution concentration and adsorption, respectively, and when n was almost equivalent to 1, the ion adsorption by sediments was linear (Machin and Aller 1984). The fitting curves and parameters of the Freundlich isotherm are presented in Fig. 2 and Table 2, which was not consistent with the linear relationship of previous reports (Machin and Aller 1984, Hou et al. 2003, Rosenfeld 1979, Rysgaa et al. 1999). However, similar to other reports (Balci and Dincel 2002, Dixit et al. 2002, Ugurlu and Karaoglu 2011, Ma et al. 2011), Q increased with the increase of Ceq. Table 2 showed that Freundlich equations could better describe the NH4+ adsorbed process, and R2 ranged from 0.97 to 0.99. K values were relatively lower for S4 and S3 (26.49~38.11 L kg-1), and higher for S1 and S2 (41.85~87.12 L kg-1), while n values were lower for S4 and S1 (-1.60~-1.95), and higher for S2 and S3 (-0.98 ~ -1.36). 2500 Adsorbed NH4 (mg/kg) 2000 1500 1000 500 0 0 1 2 3 Ceq (mg/l) Fig. 2.NH4+ adsorption isotherm S1 S2 S3 S4 Table 2. The parameters of Freundlich isotherm S1 K n R2 41.85 2.60 0.98 S2 87.12 1.98 0.99 S3 38.11 2.36 0.98 S4 26.49 2.95 0.97 Pseudo second-equation: t / qt = 1 /( k 2 qe 2 ) + t / qe Intra-particle diffusion equation: qt = ki t 1/ 2 (5) (6) Where Q and t was the amount adsorbed at time t (mg kg-1), respectively, qt and qe were the amount adsorbed at time t and equilibrium (mg kg-1), respectively, t was the sorption time (min), and k1 and k2 were sorption contents, and were sorption rate content (mg (kg·h)-1) and desorption rate content (mg (kg·h)-1). In the data fitting process, the qe was designed as the adsorbed amount at the time 720 min. Fitting curves are shown in Fig. 3. The pseudo first-equation, second-equation and Elovich equation were useful in describing adsorption on highly heterogeneous adsorbents (Demirbas et al. 2008). Therefore, using these models could effectively describe the NH4+ adsorption kinetics process by the Fen River reservoir sediment. The NH4+ adsorption kinetics process was modeled using Elovich (Fig. 4 left) equation and pseudo-second-order (Fig. 4 right) model. The figure on the left indicates that the amount of adsorbed NH4+ increased rapidly with the increasing time within the initial dozens minute. After this time, the adsorption process slowly reached equilibrium with a slow adsorption rate. The correlation coefficients and other parameters calculated from the pseudo-first-order, pseudo-second-order and Elovich models are given in Table 3. It was observed that the first-order kinetics model did not adequately fit the experimental values (R20.52) (Table 3). In contrast, the Elovich equation and pseudo-second order for sorption of NH4+ on sediment agreed well with the data. It indicated that the sediment in the Fen 100 90 80 param eter K (l/kg) 70 60 50 40 30 20 3.0 2.9 K n 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.9 52 54 56 58 60 62 64 66 68 CEC (cmol/kg) 100 90 80 param eter K (l/kg) param eter n OM (mg/kg) Fig. 3. Relationship between Freundlich isotherm parameters with CEC and OM 28 24 t/q t (m in k g /m g ) 20 16 12 8 4 0 0 Adsorbed NH 4+ (mg/kg) S1 S2 S3 S4 S1 S2 S3 S4 0 100 200 300 400 500 600 700 800 Time (min) 100 200 300 400 500 600 700 Time (min) Fig. 4. NH4+Adsorption kinetic process Table 3. The parameters of Elovich equation Sample S1 S2 S3 S4 21.55 7.85 -4.33 26.71 Elovich equation 4.20 3.44 4.94 3.94 R2 0.96 0.96 0.98 0.98 Pseudo first-equation K1 -0.013 -0.028 -0.030 -0.011 R2 0.62 0.92 0.97 0.52 K2 0.0016 -3.76 -2.05 0.0013 Pseudo second-equation qe 49.29 28.33 26.67 54.04 R2 0.99 0.99 0.96 0.99 H. Sun, X. Wang index: A case study of the Timok River (The Danube River Basin), Serbia, Archives of Environmental Protection, 38, 1, pp. 4961. Darvishi, G., Kootenaei, F.G., Ramezani, M., Lotfi, E. & Asgharnia, H. (2016). Comparative Investigation of River Water Quality by OWQI, NSFWQI and Wilcox Indexes (Case study: the Talar RiverIRAN), Archives of Environmental Protection, 42, 1, pp. 4148. de-Bashan, L.E., Hemandez, J.P., Morey, T. & Bashan, Y. (2004). Microlgae growth-promoting bacteria as "helpers" for microalgae: a novel approach for removing ammonium and phosphorus from municipal wastewater, Water Research, 38, 2, pp. 466474. Demirbas, E., Kobya, M. & Sulak, M.T. (2008). Adsorption kinetics of a basic dye from aqueous solutions onto apricot stone activated carbon, Bioresource technology, 99, 13, pp. 53685373. Dixit, S.G., Vanjara, A.K., Nagarkar, J., Nikoorazm, M. & Desi, T. (2002). Co-adsorption of quaternary ammonium compounds-nonionic surfactants on solid-liquid interface, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 205, 12, pp. 3946. Gurses, A., Karaca, S. Dogar, C., Bayrak, R., Acikyidiz, M. & Yalcin, M. (2004). Determination of adsorptive properties of clay/water system: methylene blue sorption, Journal of Colloid and Interface Science, 269, 2, pp. 310314. Holmboe, N. & Kristensen, E. (2002). Ammonium adsorption in sediments of a tropical mangrove forest (Thailand) and a temperate Wadden Sea area (Denmark), Wetlands Ecology and Management, 10, pp. 453460. Hou, L. J., Liu, M., Jiang, H.Y., Xu, S.Y., Ou, D.N., Liu, Q.M. & Zhang, B.L. (2003). Ammonium adsorption by tidal flat surface sediments from the Yangtze Estuary, Environmental Geology, 45, 1, pp. 7278. Ji, Z.Y., Yuan, J.S. & Li, X.G. (2007). Removal of ammonium from wastewater using calcium from clinoptilolite, Journal of Hazardous Materials, 141, 3, pp. 483488. Kaiserli, A., Voutsa, D. & Samara, C. (2002). Phosphorus fractionation in lake sediments-Lakes Volvi and Koronia, N. Gress, Chemosphere, 46, 8, pp. 11471155. Kelly, G. (1996). Environmental Engineering. Mc Graw Hill, Maidenhead, England 1996. Krom, M.D. & Berner, R.A. (1981). The diagenesis of phosphorus in a nearshore marine sediment, Geochimca et Cosmochimica Acta, 45, 2, pp. 207216. Ma, Z.H., Li, Q., Yue, Q.Y., Gao, B.Y., Li, W.H., Xu, X. & Zhong, Q.Q. (2011). Adsorption removal of ammonium and phosphate from water by fertilizer controlled release agent prepared from wheat straw, Chemical Engineering Journal, 171, 3, pp. 12091217. Machin, J.E. & Aller, R.C. (1984). Ammonium adsorption in marinesediments, Limnology and Oceanography, 29, 2, pp. 250257. Martens, C.S., Berner, R.A. & Rosenfeld, J.K. (1978). Interstitial water chemistry of anoxic Long-Island Sound sediments. 2. Nutrient regeneration and phosphate removal 1, Limnolgy and Oceanography, 23, 4, pp. 605617. Metcalf, E. (2003). Wastewater Engineering: Treatment and Reuse, Mc Graw Hill. New York 2003. Morin, J. & Morse, J.W. (1999). Ammonium release from resuspended sediments in the Laguna Madre estuary, Marine Chemistry, 65, 12, pp. 97110. Qzcan, A., Oncu, E.M. & Ozcan, A.S. (2006). Adsorption of Acid Blue 193 from aqueous solution onto DEDMA-sepiolite, Journal of Hazardous materials, 129, 13, pp. 244252. Rosenfeld, J.K. (1979). Ammonium adsorption in nearshore anoxic sediments, Limnology and Oceanography, 24, 2, pp. 356364. Rysgaa, S., Thastum, P., Dalsgaard, T., Christensen, P.B. & Sloth, N.P. (1999). Effects of salinity on NH4+ adsorption capacity, Rvier reservoir had a complex and heterogeneous adsorbents and more than one-step involved in the sorption processes, which agreed with other studies (Ji et al. 2007, Gurses et al. 2004, Qzcan et al. 2006). However, the Intra-particle diffusion equation could not fit the data, it indicated that the interior diffusion was not dominant ion action during the ion sorption process. Conclusion The present study showed that the NH4+ adsorption by sediments from the Fen River reservoir fitted to the Freundlich adsorption isotherm. Q increased with the increase of Ceq. CEC was an important factor influenced by the ammonium adsorption, and had a significant positive and negative correlation with the parameters K and n, while K had a negative relationship with OM. The sediments in the Fen River reservoir released NH4+ to reservoir water and acted as a pollution source. ENC0 had a positive relationship with the NH4+ contained in sediments. We were able to estimate that the ENC0 value from the NH4+ content and judged sediments acted as "NH4+ pollution source" or "NH4+ source sink" by comparing the values of ENC0 and NH4+ concentration in water. The sediment in the Fen River reservoir was a complex and heterogeneous adsorbent, and more than one-step may be involved in the NH4+ sorption processes. The NH4+ adsorption kinetics process was composed of `fast' and `slow' reaction patterns and could be fitted by Elovich equation and Pseudo second-equation. Further studies are needed to analyze the sediment which could adsorb NH4+, and evaluate the effects of this sediment behavior on the reservoir ecosystem and surrounding environment. Acknowledgement This work was supported by the National Natural Science Foundation of China (31401319), the Program for the Top Young Academic Leaders of Higher Learning Institutions of Shanxi of China (20151006), Shanxi Province Science Foundation for Youths (2013021031-4, 2015021146), and the laboratory construction project of Shanxi Science and Technology Department, the project of "The nitrogen transport-loss mechanism and progress under different land usages" and "Study on the characteristics of nitrogen loss from sloping farmland with different slope gradients and its influence on river water quality" which were financed by the Scientific Research Foundation of Shanxi Provincial Department of Water Resources. Reference Aminot, A. & Andrieux, F. (1996). Concept and determination of exchangeable phosphate in aquatic sediments, Water Research, 30, 11, pp. 28052811. Balci, S. & Dincel, Y. (2002). Ammonium ion adsorption with sepiolite: use of transient uptake method, Chemical Engineering Processing: Process Intensification, 41, 1, pp. 7985. Bouyoucos, G.J. (1951). A recalibration of the hydrometer method for making mechanical analysis of soils, Agronomy Journal, 43, 9, pp. 434438. Brankov, J., Milijasevi, D. & Milanovi, A. (2012). The assessment of the surface water quality using the water pollution nitrification, denitrification in Danish estuary sediments, Estuaries, 22, 1, pp. 2130. Ugurlu, M. & Karaoglu, M.H. (2011). Adsorption of ammonium from an aqueous solution by fly ash and sepiolite: Isotherm, kinetic and thermodynamic analysis, Microporous and Mesoporous Materials, 139, 13, pp. 173178. Zhou, A.M., Tang, H.X. & Wang, D.S. (2005). Phosphorus adsorption on natural sediments: Modeling and effects of pH and sediment composition, Water Research, 39, 7, pp. 12451254. Zhou, Q.X., Gibson, C.E. & Zhu, Y.M. (2001). Evaluation of phosphorus bioavailability in sediments of three contrasting lakes in China and the UK, Chemosphere, 42, 2, pp. 221225.
Journal
Archives of Environmental Protection – de Gruyter
Published: Dec 1, 2016