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Wastewater treatment by batch adsorption method onto micro-particles of dried Withania frutescens plant as a new adsorbent
Journal of Environmental Management 95 (2012) S61eS65
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Wastewater treatment by batch adsorption method onto micro-particles of dried Withania frutescens plant as a new adsorbent Mohamed Chiban a, *, Amina Soudani a, Fouad Sinan a, Michel Persin b a b
Department of Chemistry, Faculty of Science, BP. 8106, Hay Dakhla, Agadir 80000, Morocco European Membrane Institute, CRNS, No. 5635, 1919 Route Mende, Montpellier, France
a r t i c l e i n f o
a b s t r a c t
Article history: Received 17 August 2009 Received in revised form 17 March 2011 Accepted 21 June 2011 Available online 30 July 2011
A new adsorbent for removing metallic elements, nitrate and phosphate ions from municipal and industrial wastewaters has been investigated. This new adsorbent consists of micro-particles of dried Withania frutescens plant (<500 mm). Batch experiments were conducted to evaluate the removal of metallic elements and anions from raw wastewaters by W. frutescens particles. The results show that the micro-particles of W. frutescens plant presented a good adsorption of metallic elements, nitrate and phosphate ions from both real wastewaters. This adsorption increased with increasing of contact time. The percentage of metallic elements removal from industrial wastewater by W. frutescens plant was 98w99% for Pb(II), 92w93% for Cd(II), 91w92% for Cu(II) and 92w93% for Zn(II). The maximum adsorption capacity was dependent on the type of ions. The results also indicate that the values of chemical oxygen demand (COD) decrease after the contact with W. frutescens particles. Based on the results it can be concluded that the dried W. frutescens plant appears to be an economical and environmentally friendly material for wastewater treatment. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: W. frutescens Adsorption Metallic elements Phosphate Nitrate Wastewater treatment
1. Introduction Municipal and industrial wastewaters frequently contain heavy metals, nitrate and phosphate ions. Heavy metals pollution is spreading throughout the world because of the expansion of industrial activities. The industrial use of metals increases their concentrations in air, water and soil. The trace metals are widely spread in environment and may enter the food chain from the environment. It is well recognized that the presence of heavy metals in the environment can be detrimental to a variety of living species, including human. Unlike organic pollutants, metals are non-biodegradable and because of this the removal of heavy metal ions becomes essential. Also, nitrate and phosphates are commonly found in various raw wastewaters. They can cause serious water pollution and threaten the environment. It is therefore, essential to control and prevent their unsystematic discharge in the environment. For this reason, increased attention is being focussed on the development of technical know how for their removal from nitrate, phosphate and metal bearing effluents before being discharged into water bodies and natural streams. A number of physico-chemical technologies such as chemical precipitation, coagulation and flocculation, ion exchange and * Corresponding author. Tel.: þ212 660 60 22 29; fax: þ212 282 20 100 E-mail address: [email protected] (M. Chiban). 0301-4797/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2011.06.044
membrane techniques are available for wastewater treatment. These methods often involve high capital and operational costs and may also be associated with the generation of secondary wastes, which present treatment problems. This had as result a need for innovative treatment technologies for anions and metallic elements removal. The adsorption is one of the techniques, which is comparatively more useful and economical at a low pollutant concentration. In recent years, considerable attention has been devoted to the study of different types of low cost materials as adsorbents such as tree bark, wood charcoal, saw dust, alum sludge, red mud, peanut hulls, peat, corncobs, cocoa shells and other waste materials for the adsorption of some toxic substances (Periasamy and Namasivayam, 1995; McKay and Porter, 1997; Reddad et al., 2002; Clave et al., 2004; Meunier et al., 2003; Kadirvelu and Namasivayam, 2001; Cengeloglu et al., 2002). The use of crushed and dried plants in the wastewaters treatment has been studied in recent years and the results of the laboratory investigations showed that dried plants are good adsorbents for the removal of nitrate, phosphate and heavy metals ions from wastewaters (Abdel-Halim et al., 2003; Benhima et al., 2008; Chiban et al., 2005, 2008). The plant selected to be used as an environmentally friendly adsorbent of wastewater treatment was Withania frutescens plant from the southewestern part of Morocco. It is a shrub with little leathery leaves belonging to the Solanaceae family. The calyx of this plant increases after flowering and forms a small addition that completely hides reddish Bay
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M. Chiban et al. / Journal of Environmental Management 95 (2012) S61eS65
(Ozenda, 1983). This plant is used against poisoning and skin diseases. It also has hepatoprotector (Montilia et al., 2006) and antiinflammatory (Ahmad et al., 1990) properties. For the present work the adsorptive properties of W. frutescens plant, which is a low cost adsorbent, have been evaluated for copper, cadmium, lead, zinc, nitrate and phosphate ions adsorption from two real wastewaters, the municipal and industrial ones. The objective of this study is to investigate the efficiency of a new process for wastewater treatment by batch adsorption method onto an abundantly available and a low cost adsorbent. 2. Materials and methods
ion concentrations at different contact time, Ct (mg/l) were determined and the uptake capacity (qa, mg/g) and percentage removal (%) of pollutant were calculated as follows:
qa ¼
C0 Ct V m
%Adsorption ¼
C0 Ct 100 C0
where V (mg/l) is the volume of the solution and m (ml) is the mass of the adsorbent.
2.1. Preparation of the natural adsorbent
2.5. Instruments and apparatus
W. frutescens plant was collected from the semi-arid zones of Morocco (Agadir zone). Then it was air-dried for 2e3 days and grinded. Afterward, W. frutescens powder was sieved using 500 mm sieves and used as such without any pre-treatment. The dried plants are used as adsorbents for wastewaters treatment and inorganic pollutants removal such as: cadmium, copper, lead, zinc, nitrate and phosphate, classified as major pollutants of domestic and industrial wastewaters (Benhima et al., 2008). A recent screening (Chiban et al., 2007) of chemical composition and surface characterization has shown that the major functional groups in W. frutescens plant are polar hydroxyl, aldehydic and carboxylic groups. These groups made W. frutescens plant to have great potential as an adsorbent for metal ions in aqueous solutions. These micro-particles of W. frutescens plant are also known to be non toxic (Montilia et al., 2006; Ahmad et al., 1990). Their selection was made in close relation to their relative abundance in the southewestern Morocco zones where they are considered a worthless matter.
The instrument used for the determination of lead, cadmium, copper and zinc ions concentration was a Varian model 220FS atomic absorption spectrophotometer. The concentration of nitrate and phosphate ions was measured by Waters model capillary electrophoreses and HP model spectrophotometer, respectively. The pH values of the wastewater samples were measured by a Mettler-Toledo meter (MP120). The specific surface of W. frutescens particles was determined by N2/BET method (Micromeritics ASAP 2010) and found to be 3.8 m2/g. The surface structure, morphology and the elements of W. frutescens particles were measured by scanning electron microscope coupled with energy dispersive X-ray analysis (SEM/ EDX, LEICA-S-260) (IEMeMontpellier-France).
2.2. Collection and preparation of wastewater samples
SEM images of W. frutescens micro-particles (Figure not shown) indicated the presence of grains in the structure. The morphology of this material can facilitate the adsorption of anions and metallic elements, due to the irregular surface of W. frutescens particles. Thus it makes possible the adsorption of anions and metallic elements in different parts of the material. So, based on the morphology, as well as on high amounts of amino acid and tannins (Chiban et al., 2007), can be concluded that this material presents an adequate morphological profile to retain heavy metal and anions. The qualitative EDX spectra for dried W. frutescens microparticles (Fig. 1) indicated that Oxygen, Calcium, Carbon, Silicon,
The wastewaters used in this study were raw wastewaters collected from two Agadir zones, M’zar and Anza regions. Several raw wastewater samples were collected and stored in polyethylene bottles from two Agadir zones. M’zar and Anza wastewater samples are municipal and industrial wastewaters from Agadir zones. These samples were decanted and filtered on Whatman paper of 0.45 mm porosity. The pollutant charge of wastewater samples has been determined before using them for the batch experiments. All the glassware and sample bottles which were used, were washed first with a detergent solution, rinsed with tap water, soaked with 1.0% subboiled HNO3 for at least 12 h, and finally rinsed with Milli-Q water several times.
3. Results and discussion 3.1. W. frutescens adsorbent characterization
2.3. Batch adsorption studies Batch adsorption experiments were carried out by batch process. 40 ml of wastewater solution with a given ions concentration, C0, was mixed with 1 g of dried and grinded W. frutescens plant. The solutions put in contact with the plant matter were maintained at a constant temperature of 25 C in a water bath thermostat, the mixture being vigorously stirred by means of a magnetic stirrer. The sampled solutions were then centrifuged at 8500 g for 15 min (Biofuge primo, Heraeus Instruments). The preliminary experiments had shown that ions adsorption losses to the walls of flask and during centrifugation process were negligible. 2.4. Apparent capacity measurements The pollutant uptake was calculated by the simple method of concentration difference. The initial concentration, C0 (mg/l) and
Fig. 1. EDX spectrum of W. frutescens particles.
M. Chiban et al. / Journal of Environmental Management 95 (2012) S61eS65
Sulfur, Aluminum, Sodium, and Magnesium are the main constituents. These have been known as the main elements of W. frutescens plant.
120 100
3.2. Composition of wastewater samples
3.3. Metallic elements adsorption from municipal and industrial wastewater samples The M’zar wastewater samples contain a low concentration of metallic elements including Cu(II), Cd(II), Pb(II) and Zn(II) (Table 1). For this reason, it is not necessary to study the adsorption process at different contact times. It has been studied the removal of metallic elements by W. frutescens micro-particles after 3 h of contact time. The % removal of the metallic elements from M’zar wastewaters was noticed for all metal ions (Pb(II), Cd(II), Cu(II) and Zn(II)) at about 100%, using crushed plant as adsorbent. The variations of the % removal of metallic elements ions by W. frutescens micro-particles from Anza wastewaters versus the contact time are presented in Fig. 2. These results show that the percentage of the removed metallic elements by 1 g of W. frutescens increased with the increasing of the contact time. For all heavy metal ions, adsorption was very fast and the equilibrium was reached within 60 min. Equilibrium adsorption efficiency for Pb(II) was achieved w98e99% with an initial solution concentration of w6.09 mg/l. About w90% of the equilibrium Pb(II) uptake was adsorbed rapidly within first 15 min. This indicates a high Table 1 Characteristics of municipal and industrial wastewaters. M’zar wastewater (mg/l)
Anza wastewater (mg/l)
ESDW (Directive 98/83/CE) (mg/l)
0.40 0 0.75 1.13 123.5 98.5 1274 1023 7.6 24
6.093 0.068 2.13 17.35 2.97 81.58 1575 1034 2.2 24
0.050 0.005 1 5 50 0.05 30 25 6.5 < pH < 9.5 <25
All values are in mg/l except for pH and T, ESDW : European standard in drinking water (mg/l), COD : chemical oxygen demand, TSS : total suspended solids.
% Adsorption
80
The characteristics of the raw wastewater samples selected in this study are presented in Table 1. The treatment of two different types of wastewaters in Agadir zone was studied. M’zar and Anza wastewater samples are municipal and industrial wastewater from Agadir zones (Morocco), respectively. These results indicate that M’zar wastewater samples contain a low concentration of metallic elements but high concentration of 3 NO 3 and PO4 ions. It also shows high values of Chemical Oxygen Demand (COD). The values obtained for nitrate and phosphate ions are superior comparing to the European norms. For Anza wastewater samples, we note that the wastewater samples contain higher concentrations of metallic elements such as Pb(II), Cu(II) and Zn(II) comparing to those of M’zar wastewater samples. The adsorption studies of all pollutants from both real wastewaters on micro-particles of W. frutescens adsorbent are studied using the average concentration of these pollutants from several wastewater samples. The values of pH and temperature of M’zar wastewater samples are 7.6 and 24 C respectively. The values of pH and temperature of Anza wastewater samples are 2.2 and 24 C respectively.
Pb2þ Cd2þ Cu2þ Zn2þ NO 3 PO3 4 COD TSS pH T ( C)
S63
Anzawastewater Anza wastewater 60
Pb(II) Pb(II) Cd(II) Cd(II)
40
Cu(II) Cu(II) 20
Zn(II) Zn(II)
0 0
300
600
900
1200
1500
Contact time (min) Fig. 2. Adsorption of metallic elements from Anza wastewater by 1 g of W. frutescens plant: C0(Cd) ¼ 0.068 mg/l, C0(Cu) ¼ 2.13 mg/l, C0(Pb) ¼ 6.09 mg/l, C0(Zn) ¼ 17.35 mg/l, m/V ¼ 25 g/l, pH ¼ 2.2 and T ¼ 25 C.
adsorption rate for metallic elements from real wastewaters. It is also noticed that : i) The adsorption quantities of Cu(II), Cd(II), Pb(II) and Zn(II) ions by W. frutescens particles are about w78, w2, w241 and w640 mg/g respectively and ii) the treated wastewater onto micro-particles of dried W. frutescens plant fulfills the requirements of World Health Organization (WHO, 2004). The results show that the percentage adsorption of metallic elements from wastewaters by W. frutescens plant was found to be w99% for Pb(II), w92% for Cd(II), w91% for Cu(II) and w92% for Zn(II). It is clear that the maximum %removal was depending on the type of the metal ions. Similar results were found for metallic elements removal onto Carpobrotus edulis plant (Chiban et al., 2008). These values are much lower comparing to those obtained for laboratory solution at various concentrations, i.e. the concentrations adsorbed by these inert materials of metallic elements from laboratory solution are 1.08 g/l for copper and 0.72 g/l for zinc (Chiban et al., 2006). In the studied conditions, the %adsorption of metal ions from Anza wastewater followed the order of Pb(II) > Cd(II) > Zn(II) > Cu(II). A similar trend has been noticed in the removal of divalent metal ions (Cu(II), Cd(II), Zn(II) and Pb(II)) by other plants (Benhima et al., 2008). 3.4. Nitrate and phosphate ions adsorption from real wastewaters The variations of the % removal of nitrate and phosphate ions from selected municipal and industrial wastewaters, versus the contact time are plotted in Fig. 3 for W. frutescens plant as adsorbent. For both nitrate and phosphate, we note that the % adsorption of W. frutescens particles increased with the increasing of the contact time. The equilibrium time was found to be 60, 240 min for nitrate and phosphate ions, respectively. It is also noticed a rapid kinetic adsorption with up to w95% nitrate ions removal in the first 30 min. After the fast initial process, the adsorption continues at a slower rate, before reaching a constant level. The final nitrate ions concentrations (Cf < 3 mg/l) are lower than 25 mg/l, which is the European standard for drinking water (Directive 98/83/CE, 1998). The adsorption process of phosphate ions by W. frutescens plant appeared to follow a process in two phases characterized by an initial fast retention step lasting at the maximum, less than 30 min, and corresponding to an uptake concentration of about w48ew56% of the initial PO3 4 concentration of Anza wastewater,
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M. Chiban et al. / Journal of Environmental Management 95 (2012) S61eS65
a 120
1800
100 1600 COD supp (mg/l)
% Adsorption
80
M'zar wastewater 60
Nitrate Phosphate
40
1400
Anza wastewater M'zar wastewater
1200
20 1000
0 0
300
600
900
1200
1500
0
300
600 900 1200 Contact time (min)
1500
Contact time (min)
b
Fig. 4. Effect of contact time variation of the COD supplement by gram of W. frutescens plant: T ¼ 25 C, m/V ¼ 25 g/l and natural pH.
120
% Adsorption
100 80 60
Anza wastewater
40
Nitrate
20
Phosphate
0 0
300
600
900
1200
1500
wastewaters) by W. frutescens particles is presented in Fig. 4. For Anza wastewater samples, the results show that COD supplement decreased with the increasing of the contact time. In the case of M’zar municipal wastewater, the results indicate that the release of the organic matter in the solution by the adsorbent obtained from W. frutescens increased with the increasing of the contact time. This difference can be explained by the variation of the pH of wastewater samples (pH(Anza) ¼ 2.2, pH(M’zar) ¼ 7.6). The tests of adsorption process with distilled water showed that the microparticles of W. frutescens plant can release important amounts of organic matter in solution, which suggests the necessity of a prewash before using these micro-particles of dried W. frutescens plant.
Contact time (min) 3 Fig. 3. Adsorption of NO 3 and PO4 ions by 1 g of W. frutescens plant from: (a): M’zar 3 wastewater; C0(NO 3 ) ¼ 123.5 mg/l, C0(PO4 ) ¼ 98.5 mg/l, pH ¼ 7.6 and T ¼ 25 C. (b): 3 Anza wastewater; C0 (NO 3 ) ¼ 2.97 mg/l, C0 (PO4 ) ¼ 81.58 mg/l, pH ¼ 2.2 and T ¼ 25 C.
followed by a much slower step lasting for hours and tending to a stable state. The equilibrium is attained in less than 5 h for M’zar wastewater and more than 5 h for Anza wastewater. This difference can be explained by the type of wastewater. Under these experimental conditions, the maximum efficiency for nitrate and phosphate ions uptake by unit of weight of dried plant is higher than 4.91 mg/g. These values depend on the type of 3 anions because the uptake of NO 3 is higher than that for PO4 ions. This indicates some specificity of the interactions between anions and active sites of W. frutescens plant responsible for the ions adsorption. These results are much lower in comparison with those obtained for the laboratory solutions. The concentrations retained by W. frutescens of nitrate and phosphate ions from aqueous solu3 tions are 2.8 g/l (115 mg/g) for NO 3 and 0.61 g/l (22 mg/g) for PO4 ions (Chiban et al., 2006). The results of adsorption onto micro-particles of W. frutescens plant with distilled water show that the negligible quantities of nitrate and phosphate ions are released by W. frutescens plant (Qreleased (NO 3 ) << 0.01 mg/g, after 24 h of contact time). 3.5. Chemical oxygen demand (COD) The effect of the contact time under agitation on the supplement COD from two types of raw wastewaters (M’zar and Anza
4. Conclusion In this study, tests were performed to evaluate the use of W. frutescens plant as an adsorbent for nitrate, phosphate and metallic elements. The results showed that the micro-particles of W. frutescens plant can be used as an adsorbent for the effective 3 removal of Pb2þ, Cu2þ, Cd2þ, Zn2þ, NO 3 and PO4 ions from raw wastewater samples of Agadir zones (Morocco). It was found that zinc, lead, cadmium and copper were adsorbed by dried and crushed W. frutescens plant very rapidly (within the first 30 min), while equilibrium was reached in 60 min for metallic elements and nitrate and 240 min for phosphate ions. The % removal of metallic elements from Anza wastewater samples by W. frutescens plant was 98w99% for Pb(II), 92w93% for Cd(II), 91w92% for Cu(II) and 92w93% for Zn(II). The adsorption’s percentage of metal ions from Anza wastewaters followed the order: Pb(II) > Cd(II) > Zn(II) > Cu(II). The experimental results of this study can be used to design batch adsorption systems for the metallic elements, nitrate and phosphate removal. Such a batch system will be applicable to small industries which generate metallic elements-containing wastewaters. Acknowledgments This joint program was made possible thanks to the «comité Mixte inter Universitaire Franco- Marocain (A.I. N 128/MA)». We gratefully acknowledge funding through European Membrane Institute for technical support and analytical screening of samples.
M. Chiban et al. / Journal of Environmental Management 95 (2012) S61eS65
References Abdel-Halim, S.H., Shehata, A.M.A., El-Shahat, M.F., 2003. Removal of lead ions from industrial wastewater by different types of natural materials. Water Res. 37, 1678e1683. Ahmad, A.M., Miro, M., Ocete, M.A., Jimenez, J., Navarro, M.C., 1990. Echalliul elatertrium (L) A. Richard.III. Assessment of its anti-inflammatory behaviour, Ethnopharmacologie: Sources, méthodes, objectifs. SFE e Ed. ORSTOM, ParisMetz, pp. 389e392. Benhima, H., Chiban, M., Sinan, F., Seta, P., Persin, M., 2008. Removal of lead and cadmium ions from aqueous solution by adsorption onto micro-particles of dry plants. Colloids Surf. B. 61, 10e16. Cengeloglu, Y., Kir, E., Ersoz, M., 2002. Removal of fluoride from aqueous solution by using red mud. Sep. Purif. Technol 28, 81e86. Chiban, M., Amzeghal, A., Benhima, H., Sinan, F., Tahrouch, S., Seta, P., 2007. Phytochemical study of some plants from South part of Morocco (Etude phytochimique de certaines plantes inertes du sud marocain). Rev. Biol. Biotechnol. 6, 40e43. Chiban, M., Benhima, H., Saadi, B., Nounah, A., Sinan, F., 2005. Isotherms and kinetic 2 study of dihydrogen and hydrogen phosphate ions (H2PO 4 and HPO4 ) onto crushed plant matter of the semi-arid zones of Morocco: Asphodelus microcarpus, Asparagus albus and Senecio anthophorbium. J. Physique IV 123, 393e399. Chiban, M., Benhima, H., Sinan, F., Eddaoudi, H., Seta, P., Persin, M., 2006. Récents Progrès en Génie des Procédés. Study of a new adsorbent used as membrane filter for anions and metallic elements removal. (Etude des propriétés adsorbantes de nouveaux biomatériaux inertes solides utilisables comme membrane filtre pour l’élimination des ions métalliques et minéraux), vol. 93. SFGP, Paris, ISBN 2-910239-67-5, pp. 46e54.
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Chiban, M., Soudani, A., Sinan, F., Persin, M., 2008. Wastewater treatment by adsorption onto Carpobrotus edulis used as natural adsorbent. In: Proceedings of XIIITH IWRA World Water Congress, 1e4 September, Montpellier, France. Available on website: http://196.36.166.88/iwra/Proceedings/. Clave, E., Francois, J., Billon, L., Sebe, G., De Jeso, B., Guimon, M.F., 2004. Crude and modified corncobs as complexing agents for water decontamination. J. Appl. Polym. Sci. 91, 820e826. Directive 98/83/European Community of council, 3 November 1998. Relating to the quality of water intended for human consumption. Official J. Euro. Community, Brussels, pp. 32e54. Kadirvelu, K., Namasivayam, C., 2001. Removal of heavy metals from industrial wastewaters by adsorption onto activated carbon prepared from an agricultural solid waste. Bioresour. Technol. 76, 63e65. McKay, G., Porter, J.F., 1997. Equilibrium parameter for the sorption of copper, cadmium and zinc ions onto peat. J. Chem. Technol. Biotechnol. 69, 309e320. Meunier, N., Laroulandie, J., Blais, J.F., Tyagi, R.D., 2003. Cocoa shells for heavy metal removal from acidic solutions. Bioresour. Technol. 90, 255e263. Montilia, M.P., Cabo, J., Navarro, M.C., Risco, S., Jiménez, J., Anerios, J., 2006. The protective and curative action of Withania frutescens leaf extract against CCl4induced hepatotoxicity. Phytother. Res. 4, 212e215. doi:10.1002/ptr.2650040603. Ozenda, P., 1983. The Flora of Sahara. (Flore du Sahara). CNRS, Paris, pp. 56e68. Periasamy, K., Namasivayam, C., 1995. Removal of nickel(II) from aqueous solution and nickel electroplating industry wastewater using an agricultural waste: peanut hulls. Waste Manag. 15, 63e68. Reddad, Z., Gerente, C., Andres, Y., Le Cloirec, P., 2002. Adsorption of several metal ions onto a low cost biosorbent: kinetic and equilibrium studies. Environ. Sci. Technol. 36, 2067e2073. WHO (World Health Organization), Guidelines for drinking-water quality, vol. 1, Recommendations. third ed., Geneva, 2004.
Contents lists available at ScienceDirect
Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman
Wastewater treatment by batch adsorption method onto micro-particles of dried Withania frutescens plant as a new adsorbent Mohamed Chiban a, *, Amina Soudani a, Fouad Sinan a, Michel Persin b a b
Department of Chemistry, Faculty of Science, BP. 8106, Hay Dakhla, Agadir 80000, Morocco European Membrane Institute, CRNS, No. 5635, 1919 Route Mende, Montpellier, France
a r t i c l e i n f o
a b s t r a c t
Article history: Received 17 August 2009 Received in revised form 17 March 2011 Accepted 21 June 2011 Available online 30 July 2011
A new adsorbent for removing metallic elements, nitrate and phosphate ions from municipal and industrial wastewaters has been investigated. This new adsorbent consists of micro-particles of dried Withania frutescens plant (<500 mm). Batch experiments were conducted to evaluate the removal of metallic elements and anions from raw wastewaters by W. frutescens particles. The results show that the micro-particles of W. frutescens plant presented a good adsorption of metallic elements, nitrate and phosphate ions from both real wastewaters. This adsorption increased with increasing of contact time. The percentage of metallic elements removal from industrial wastewater by W. frutescens plant was 98w99% for Pb(II), 92w93% for Cd(II), 91w92% for Cu(II) and 92w93% for Zn(II). The maximum adsorption capacity was dependent on the type of ions. The results also indicate that the values of chemical oxygen demand (COD) decrease after the contact with W. frutescens particles. Based on the results it can be concluded that the dried W. frutescens plant appears to be an economical and environmentally friendly material for wastewater treatment. Ó 2011 Elsevier Ltd. All rights reserved.
Keywords: W. frutescens Adsorption Metallic elements Phosphate Nitrate Wastewater treatment
1. Introduction Municipal and industrial wastewaters frequently contain heavy metals, nitrate and phosphate ions. Heavy metals pollution is spreading throughout the world because of the expansion of industrial activities. The industrial use of metals increases their concentrations in air, water and soil. The trace metals are widely spread in environment and may enter the food chain from the environment. It is well recognized that the presence of heavy metals in the environment can be detrimental to a variety of living species, including human. Unlike organic pollutants, metals are non-biodegradable and because of this the removal of heavy metal ions becomes essential. Also, nitrate and phosphates are commonly found in various raw wastewaters. They can cause serious water pollution and threaten the environment. It is therefore, essential to control and prevent their unsystematic discharge in the environment. For this reason, increased attention is being focussed on the development of technical know how for their removal from nitrate, phosphate and metal bearing effluents before being discharged into water bodies and natural streams. A number of physico-chemical technologies such as chemical precipitation, coagulation and flocculation, ion exchange and * Corresponding author. Tel.: þ212 660 60 22 29; fax: þ212 282 20 100 E-mail address: [email protected] (M. Chiban). 0301-4797/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvman.2011.06.044
membrane techniques are available for wastewater treatment. These methods often involve high capital and operational costs and may also be associated with the generation of secondary wastes, which present treatment problems. This had as result a need for innovative treatment technologies for anions and metallic elements removal. The adsorption is one of the techniques, which is comparatively more useful and economical at a low pollutant concentration. In recent years, considerable attention has been devoted to the study of different types of low cost materials as adsorbents such as tree bark, wood charcoal, saw dust, alum sludge, red mud, peanut hulls, peat, corncobs, cocoa shells and other waste materials for the adsorption of some toxic substances (Periasamy and Namasivayam, 1995; McKay and Porter, 1997; Reddad et al., 2002; Clave et al., 2004; Meunier et al., 2003; Kadirvelu and Namasivayam, 2001; Cengeloglu et al., 2002). The use of crushed and dried plants in the wastewaters treatment has been studied in recent years and the results of the laboratory investigations showed that dried plants are good adsorbents for the removal of nitrate, phosphate and heavy metals ions from wastewaters (Abdel-Halim et al., 2003; Benhima et al., 2008; Chiban et al., 2005, 2008). The plant selected to be used as an environmentally friendly adsorbent of wastewater treatment was Withania frutescens plant from the southewestern part of Morocco. It is a shrub with little leathery leaves belonging to the Solanaceae family. The calyx of this plant increases after flowering and forms a small addition that completely hides reddish Bay
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M. Chiban et al. / Journal of Environmental Management 95 (2012) S61eS65
(Ozenda, 1983). This plant is used against poisoning and skin diseases. It also has hepatoprotector (Montilia et al., 2006) and antiinflammatory (Ahmad et al., 1990) properties. For the present work the adsorptive properties of W. frutescens plant, which is a low cost adsorbent, have been evaluated for copper, cadmium, lead, zinc, nitrate and phosphate ions adsorption from two real wastewaters, the municipal and industrial ones. The objective of this study is to investigate the efficiency of a new process for wastewater treatment by batch adsorption method onto an abundantly available and a low cost adsorbent. 2. Materials and methods
ion concentrations at different contact time, Ct (mg/l) were determined and the uptake capacity (qa, mg/g) and percentage removal (%) of pollutant were calculated as follows:
qa ¼
C0 Ct V m
%Adsorption ¼
C0 Ct 100 C0
where V (mg/l) is the volume of the solution and m (ml) is the mass of the adsorbent.
2.1. Preparation of the natural adsorbent
2.5. Instruments and apparatus
W. frutescens plant was collected from the semi-arid zones of Morocco (Agadir zone). Then it was air-dried for 2e3 days and grinded. Afterward, W. frutescens powder was sieved using 500 mm sieves and used as such without any pre-treatment. The dried plants are used as adsorbents for wastewaters treatment and inorganic pollutants removal such as: cadmium, copper, lead, zinc, nitrate and phosphate, classified as major pollutants of domestic and industrial wastewaters (Benhima et al., 2008). A recent screening (Chiban et al., 2007) of chemical composition and surface characterization has shown that the major functional groups in W. frutescens plant are polar hydroxyl, aldehydic and carboxylic groups. These groups made W. frutescens plant to have great potential as an adsorbent for metal ions in aqueous solutions. These micro-particles of W. frutescens plant are also known to be non toxic (Montilia et al., 2006; Ahmad et al., 1990). Their selection was made in close relation to their relative abundance in the southewestern Morocco zones where they are considered a worthless matter.
The instrument used for the determination of lead, cadmium, copper and zinc ions concentration was a Varian model 220FS atomic absorption spectrophotometer. The concentration of nitrate and phosphate ions was measured by Waters model capillary electrophoreses and HP model spectrophotometer, respectively. The pH values of the wastewater samples were measured by a Mettler-Toledo meter (MP120). The specific surface of W. frutescens particles was determined by N2/BET method (Micromeritics ASAP 2010) and found to be 3.8 m2/g. The surface structure, morphology and the elements of W. frutescens particles were measured by scanning electron microscope coupled with energy dispersive X-ray analysis (SEM/ EDX, LEICA-S-260) (IEMeMontpellier-France).
2.2. Collection and preparation of wastewater samples
SEM images of W. frutescens micro-particles (Figure not shown) indicated the presence of grains in the structure. The morphology of this material can facilitate the adsorption of anions and metallic elements, due to the irregular surface of W. frutescens particles. Thus it makes possible the adsorption of anions and metallic elements in different parts of the material. So, based on the morphology, as well as on high amounts of amino acid and tannins (Chiban et al., 2007), can be concluded that this material presents an adequate morphological profile to retain heavy metal and anions. The qualitative EDX spectra for dried W. frutescens microparticles (Fig. 1) indicated that Oxygen, Calcium, Carbon, Silicon,
The wastewaters used in this study were raw wastewaters collected from two Agadir zones, M’zar and Anza regions. Several raw wastewater samples were collected and stored in polyethylene bottles from two Agadir zones. M’zar and Anza wastewater samples are municipal and industrial wastewaters from Agadir zones. These samples were decanted and filtered on Whatman paper of 0.45 mm porosity. The pollutant charge of wastewater samples has been determined before using them for the batch experiments. All the glassware and sample bottles which were used, were washed first with a detergent solution, rinsed with tap water, soaked with 1.0% subboiled HNO3 for at least 12 h, and finally rinsed with Milli-Q water several times.
3. Results and discussion 3.1. W. frutescens adsorbent characterization
2.3. Batch adsorption studies Batch adsorption experiments were carried out by batch process. 40 ml of wastewater solution with a given ions concentration, C0, was mixed with 1 g of dried and grinded W. frutescens plant. The solutions put in contact with the plant matter were maintained at a constant temperature of 25 C in a water bath thermostat, the mixture being vigorously stirred by means of a magnetic stirrer. The sampled solutions were then centrifuged at 8500 g for 15 min (Biofuge primo, Heraeus Instruments). The preliminary experiments had shown that ions adsorption losses to the walls of flask and during centrifugation process were negligible. 2.4. Apparent capacity measurements The pollutant uptake was calculated by the simple method of concentration difference. The initial concentration, C0 (mg/l) and
Fig. 1. EDX spectrum of W. frutescens particles.
M. Chiban et al. / Journal of Environmental Management 95 (2012) S61eS65
Sulfur, Aluminum, Sodium, and Magnesium are the main constituents. These have been known as the main elements of W. frutescens plant.
120 100
3.2. Composition of wastewater samples
3.3. Metallic elements adsorption from municipal and industrial wastewater samples The M’zar wastewater samples contain a low concentration of metallic elements including Cu(II), Cd(II), Pb(II) and Zn(II) (Table 1). For this reason, it is not necessary to study the adsorption process at different contact times. It has been studied the removal of metallic elements by W. frutescens micro-particles after 3 h of contact time. The % removal of the metallic elements from M’zar wastewaters was noticed for all metal ions (Pb(II), Cd(II), Cu(II) and Zn(II)) at about 100%, using crushed plant as adsorbent. The variations of the % removal of metallic elements ions by W. frutescens micro-particles from Anza wastewaters versus the contact time are presented in Fig. 2. These results show that the percentage of the removed metallic elements by 1 g of W. frutescens increased with the increasing of the contact time. For all heavy metal ions, adsorption was very fast and the equilibrium was reached within 60 min. Equilibrium adsorption efficiency for Pb(II) was achieved w98e99% with an initial solution concentration of w6.09 mg/l. About w90% of the equilibrium Pb(II) uptake was adsorbed rapidly within first 15 min. This indicates a high Table 1 Characteristics of municipal and industrial wastewaters. M’zar wastewater (mg/l)
Anza wastewater (mg/l)
ESDW (Directive 98/83/CE) (mg/l)
0.40 0 0.75 1.13 123.5 98.5 1274 1023 7.6 24
6.093 0.068 2.13 17.35 2.97 81.58 1575 1034 2.2 24
0.050 0.005 1 5 50 0.05 30 25 6.5 < pH < 9.5 <25
All values are in mg/l except for pH and T, ESDW : European standard in drinking water (mg/l), COD : chemical oxygen demand, TSS : total suspended solids.
% Adsorption
80
The characteristics of the raw wastewater samples selected in this study are presented in Table 1. The treatment of two different types of wastewaters in Agadir zone was studied. M’zar and Anza wastewater samples are municipal and industrial wastewater from Agadir zones (Morocco), respectively. These results indicate that M’zar wastewater samples contain a low concentration of metallic elements but high concentration of 3 NO 3 and PO4 ions. It also shows high values of Chemical Oxygen Demand (COD). The values obtained for nitrate and phosphate ions are superior comparing to the European norms. For Anza wastewater samples, we note that the wastewater samples contain higher concentrations of metallic elements such as Pb(II), Cu(II) and Zn(II) comparing to those of M’zar wastewater samples. The adsorption studies of all pollutants from both real wastewaters on micro-particles of W. frutescens adsorbent are studied using the average concentration of these pollutants from several wastewater samples. The values of pH and temperature of M’zar wastewater samples are 7.6 and 24 C respectively. The values of pH and temperature of Anza wastewater samples are 2.2 and 24 C respectively.
Pb2þ Cd2þ Cu2þ Zn2þ NO 3 PO3 4 COD TSS pH T ( C)
S63
Anzawastewater Anza wastewater 60
Pb(II) Pb(II) Cd(II) Cd(II)
40
Cu(II) Cu(II) 20
Zn(II) Zn(II)
0 0
300
600
900
1200
1500
Contact time (min) Fig. 2. Adsorption of metallic elements from Anza wastewater by 1 g of W. frutescens plant: C0(Cd) ¼ 0.068 mg/l, C0(Cu) ¼ 2.13 mg/l, C0(Pb) ¼ 6.09 mg/l, C0(Zn) ¼ 17.35 mg/l, m/V ¼ 25 g/l, pH ¼ 2.2 and T ¼ 25 C.
adsorption rate for metallic elements from real wastewaters. It is also noticed that : i) The adsorption quantities of Cu(II), Cd(II), Pb(II) and Zn(II) ions by W. frutescens particles are about w78, w2, w241 and w640 mg/g respectively and ii) the treated wastewater onto micro-particles of dried W. frutescens plant fulfills the requirements of World Health Organization (WHO, 2004). The results show that the percentage adsorption of metallic elements from wastewaters by W. frutescens plant was found to be w99% for Pb(II), w92% for Cd(II), w91% for Cu(II) and w92% for Zn(II). It is clear that the maximum %removal was depending on the type of the metal ions. Similar results were found for metallic elements removal onto Carpobrotus edulis plant (Chiban et al., 2008). These values are much lower comparing to those obtained for laboratory solution at various concentrations, i.e. the concentrations adsorbed by these inert materials of metallic elements from laboratory solution are 1.08 g/l for copper and 0.72 g/l for zinc (Chiban et al., 2006). In the studied conditions, the %adsorption of metal ions from Anza wastewater followed the order of Pb(II) > Cd(II) > Zn(II) > Cu(II). A similar trend has been noticed in the removal of divalent metal ions (Cu(II), Cd(II), Zn(II) and Pb(II)) by other plants (Benhima et al., 2008). 3.4. Nitrate and phosphate ions adsorption from real wastewaters The variations of the % removal of nitrate and phosphate ions from selected municipal and industrial wastewaters, versus the contact time are plotted in Fig. 3 for W. frutescens plant as adsorbent. For both nitrate and phosphate, we note that the % adsorption of W. frutescens particles increased with the increasing of the contact time. The equilibrium time was found to be 60, 240 min for nitrate and phosphate ions, respectively. It is also noticed a rapid kinetic adsorption with up to w95% nitrate ions removal in the first 30 min. After the fast initial process, the adsorption continues at a slower rate, before reaching a constant level. The final nitrate ions concentrations (Cf < 3 mg/l) are lower than 25 mg/l, which is the European standard for drinking water (Directive 98/83/CE, 1998). The adsorption process of phosphate ions by W. frutescens plant appeared to follow a process in two phases characterized by an initial fast retention step lasting at the maximum, less than 30 min, and corresponding to an uptake concentration of about w48ew56% of the initial PO3 4 concentration of Anza wastewater,
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a 120
1800
100 1600 COD supp (mg/l)
% Adsorption
80
M'zar wastewater 60
Nitrate Phosphate
40
1400
Anza wastewater M'zar wastewater
1200
20 1000
0 0
300
600
900
1200
1500
0
300
600 900 1200 Contact time (min)
1500
Contact time (min)
b
Fig. 4. Effect of contact time variation of the COD supplement by gram of W. frutescens plant: T ¼ 25 C, m/V ¼ 25 g/l and natural pH.
120
% Adsorption
100 80 60
Anza wastewater
40
Nitrate
20
Phosphate
0 0
300
600
900
1200
1500
wastewaters) by W. frutescens particles is presented in Fig. 4. For Anza wastewater samples, the results show that COD supplement decreased with the increasing of the contact time. In the case of M’zar municipal wastewater, the results indicate that the release of the organic matter in the solution by the adsorbent obtained from W. frutescens increased with the increasing of the contact time. This difference can be explained by the variation of the pH of wastewater samples (pH(Anza) ¼ 2.2, pH(M’zar) ¼ 7.6). The tests of adsorption process with distilled water showed that the microparticles of W. frutescens plant can release important amounts of organic matter in solution, which suggests the necessity of a prewash before using these micro-particles of dried W. frutescens plant.
Contact time (min) 3 Fig. 3. Adsorption of NO 3 and PO4 ions by 1 g of W. frutescens plant from: (a): M’zar 3 wastewater; C0(NO 3 ) ¼ 123.5 mg/l, C0(PO4 ) ¼ 98.5 mg/l, pH ¼ 7.6 and T ¼ 25 C. (b): 3 Anza wastewater; C0 (NO 3 ) ¼ 2.97 mg/l, C0 (PO4 ) ¼ 81.58 mg/l, pH ¼ 2.2 and T ¼ 25 C.
followed by a much slower step lasting for hours and tending to a stable state. The equilibrium is attained in less than 5 h for M’zar wastewater and more than 5 h for Anza wastewater. This difference can be explained by the type of wastewater. Under these experimental conditions, the maximum efficiency for nitrate and phosphate ions uptake by unit of weight of dried plant is higher than 4.91 mg/g. These values depend on the type of 3 anions because the uptake of NO 3 is higher than that for PO4 ions. This indicates some specificity of the interactions between anions and active sites of W. frutescens plant responsible for the ions adsorption. These results are much lower in comparison with those obtained for the laboratory solutions. The concentrations retained by W. frutescens of nitrate and phosphate ions from aqueous solu3 tions are 2.8 g/l (115 mg/g) for NO 3 and 0.61 g/l (22 mg/g) for PO4 ions (Chiban et al., 2006). The results of adsorption onto micro-particles of W. frutescens plant with distilled water show that the negligible quantities of nitrate and phosphate ions are released by W. frutescens plant (Qreleased (NO 3 ) << 0.01 mg/g, after 24 h of contact time). 3.5. Chemical oxygen demand (COD) The effect of the contact time under agitation on the supplement COD from two types of raw wastewaters (M’zar and Anza
4. Conclusion In this study, tests were performed to evaluate the use of W. frutescens plant as an adsorbent for nitrate, phosphate and metallic elements. The results showed that the micro-particles of W. frutescens plant can be used as an adsorbent for the effective 3 removal of Pb2þ, Cu2þ, Cd2þ, Zn2þ, NO 3 and PO4 ions from raw wastewater samples of Agadir zones (Morocco). It was found that zinc, lead, cadmium and copper were adsorbed by dried and crushed W. frutescens plant very rapidly (within the first 30 min), while equilibrium was reached in 60 min for metallic elements and nitrate and 240 min for phosphate ions. The % removal of metallic elements from Anza wastewater samples by W. frutescens plant was 98w99% for Pb(II), 92w93% for Cd(II), 91w92% for Cu(II) and 92w93% for Zn(II). The adsorption’s percentage of metal ions from Anza wastewaters followed the order: Pb(II) > Cd(II) > Zn(II) > Cu(II). The experimental results of this study can be used to design batch adsorption systems for the metallic elements, nitrate and phosphate removal. Such a batch system will be applicable to small industries which generate metallic elements-containing wastewaters. Acknowledgments This joint program was made possible thanks to the «comité Mixte inter Universitaire Franco- Marocain (A.I. N 128/MA)». We gratefully acknowledge funding through European Membrane Institute for technical support and analytical screening of samples.
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