International Journal of Environmental Science & Technology Vol . 1, No . 2, pp . 125 -133 , Summer 2004
Investigation of ammonia removal from polluted waters by Clinoptilolite zeolite
1* A. R. Rahmani, 2A. H. Mahvi, 2A. R. Mesdaghinia and 2S. Nasseri 1Department of Environmental Health, School of Public Health, Hamadan University of Medical Sciences, Ha madan, Iran
2Department of Environmental Health Engineering, School of Public Health and Institute of Health Research Center, Tehran University of Medical Sciences, Tehran, Iran Abstract Ammonia nitrogen compounds in the wastewaters and effluents have harmful effects on water resources. Ion exchange with zeolites is a separation process for ammonia removal from effluents. The objective of this research was to study the efficiency of an ammonia removal and the factor affecting to this process. The Clino ptilolite was obtained from Semnan mines at the north part of Iran. The samples were grounded and sieved based on the U .S. standard mesh number 20 , 30 , 40 and conditioned by ammonia sulfate and sodium chloride solutions. The characteristics of samples for ammonia removal and the selectivity sequence for adsorbing interfering cations were then determined. Results shown that the average ion exchange capacity of zeolite in + batch and continuous systems were 6.65 -16 and 16.31 -19.5 mg NH 4 /g zeolite weight, resp ectively. In study on + + + 2+ 2+ the zeolite for selective cations showed the ranking of K , NH 4 , Na , Ca and Mg respectively. Results indicated that high level of regeneration (95 -98% ) might be achieved with NaCl solution . Based on the results, Clinoptilolite m ay be effective applied in wastewater treatment, both from technical and economical aspects. Key words: Clinoptilolite, zeolite , wastewater treatment, ammonia, ion exchange *Corresponding Author, E -mail: rahmani @umsha.ac.ir
Introduction Ammonia nitrogen discharges from and ammonia ions from aqueous solutions municipal, industrial and agricultural (Mercer, et al., 1970; Koon and Kaufman, wastewater sites, which subsequently mixes 1975 and Schoman, 1986). In addition to have into water resources. Some of deleterious a greater affinity for ammonia ions than other effects include accelerated eutrophication of exch ange media, it is relatively inexpensive lake, dissolved oxyge n depletion in receiving when compared to synthetic sorbents waters and fish toxicity (EPA, 1975). The employed. Several authors have investigated maximum limit of ammonia set by the ammonia removal form polluted water by European Association for drinking water is natural zeolite . Ames (1967) and Mercer approximately 0.5 mg l –1 and also a guide level (1970) suggested that the use of Clinoptilolite –1 + is given as 0.05 mg l ( AWWA, 1990 and for remo val of NH 4 from wastewater. In these Gaspard, et al., 1983). The raw water with high studies sedimentation effluent with 10 to 19 + ammonia concentration must therefore be mg/l NH 4 treated and efficiency of process treated before it reaches the consumer and also was obtained 93 to 98%. Koon and Kaufman the wastewater discharge into the receiving (1975) were concerned with ammonia removal water. The most widely used methods for from municipal wastewater by Clinoptilolite. removing ammonia from wastewater are air The pilot study by Liberti (1981) on ammonia stripping, ion ex change, breakpoint removal by Clinoptilolite showed that the ion chlorination and biological nitrification- selectivity by zeolite for ammonia. Gaspard, et denitrification (Metcalf and Eddy, 2003). Ion al., ( 1983) examined the ammonia removal exchange has been demonstrated to be characteristics from drinking water by competitive with other methods both in terms Clinoptilolite . Ershov (1984) studied the of performance and cost (Mercer, et al., 1970 ammonia removal in laboratory and semi and Culp, et al., 1978). Clinoptilolite is one of industrial scale . In these studies the 10% NaCl the natural zeolites used to remove the cations solution was used for regeneration. Schoeman A. R. Rahmani, et al. Investigation of ammonia removal…
(1986) evaluated NH 3-N removal from an with investigations batch sorption and column underground mine water by South African studi es. The chemical properties of Semnan Clinoptilolite and compared it with H ector Clinoptilolite used in this study were studied Clinoptilolite from the USA. Haralambous, et by Kazemian (1993), are given in Table 1. al., ( 1992) compared natural and synthetic zeolites for ammonia removal from aqueous Table 1: Chemical analysis of Semnan Clinoptilolite based on XRD* solution. Constituent % By weight In the aqueous solution, ammonia may exist SiO 2 69.53 in either the nonionized form (NH 3) and/or + CaO 3.67 ionized form (NH 4 ) dep ending on the pH and temperature. The ion-exchange process can K 2O 2.77 remove only the ionized one. The equilibrium- Al 2O3 7.75 exchange capacity remains constantly up to pH Na 2O 0.63 7. The pH of the aqueous solution must be Fe 2O3 1.41 at /or below 7 for optimum ion-exchange TiO 2 0.19 operation. During the ion-exchange process, LOI 12.94 + + the Na ion is replaced by the NH 4 ion, and Total 99.37 hence the Na + ion concentration increases in * X Ray Diffraction the liquid phase during the ion-exchange processes. When the ion-exchanger reaches All analysis was made according to the breakthrough, the up flow or down flow Standard Methods (1992). Ammonia was then regeneration method is applied. Gaspard, et al., determi ned by the Nessler method. Ammonia (1983) reported that the up flow regeneration is chloride stoke solution was prepared by more attractive than down flow regeneration. dissolving 1g NH 4Cl in 1 liter of demonized Thus the first is ion exchange and as soon as water. For preparation of synthetic samples the Clinoptilolite containing a large amount of appropriate amounts of ammonia chloride ammonia ions is in contact with salt solutio n stoke were added to distilled water to give the and ion exchange takes place according to desired ammonia concentration. equation 1: The collected Clinoptilolite samples were grounded and sieved and the fractions between + + + + Z-NH 4 + Na Z-Na + NH 4 ( 1) U.S. standard mesh numbers 20, 30 and 40 (0.84, 0.589 and 0.42 mm ) were used for the The ammonia ion-exchange capacity study. The zeolite samples after being washed varies depending on the presence of another for rem oval of fine, conditioned by 0.25-M cations in the aqueous phase and initial ammonia sulfate and 1 M sodium chloride ammonia concentration (Gaspard, et al ., 1983 respectively. The samples were then rinsed and and Singh and Prasad, 1997). stored dry. The characteristics of the zeolite for The present work considers ammonia ammonia exchange were determined in two removal by a natural ion-exchange resin. This batch and continuous systems. investigation concentrates on defining various operati onal parameters necessary to remove Batch studi es ammonia through ion exchange by using the 1) In the first phase of runs, 500 ml of Clinoptilolite, zeolite. ammonia chloride solution with 1000 mg /l The main objective of this paper is to strength were conducted in separate stages evaluate the characteristics of Semnan with different weights and sizes of conditioned Clinoptilolite for removing ammonia ions from zeolite samples . After mixing for 48 hours aqueous solutions under varyi ng conditions. ammonia remained in solution was meas ured with Nessler method. The cation exchange Materials and Methods capacities for ammonia were determined by In this study the Clinoptilolite in rock form dividing the amount of ammonia removal by was supplied from Semnan mines in the north the mass of zeolite in the flask. part of Iran during 2000-2001. The 2) In the second phase of runs, batch experiments were conducted in two phases sorption isotherms for the removal of ammonia
126 Investigation of ammonia remov al…
were i nvestigated . In 1000 ml conical flasks at These models are rearranged to the linear 20° C . Weighed amounts (30 g with mesh 30) form by taking logarithms on both sides: of Clinoptilolite were introduced into 12 conical flasks, in which 500 ml of ammonia log Q = log K f + n log Ce (5) solution concentrations of 50 to 1400 mg /l were added. The flasks were then shaken and Ce 1 a = + C (6) mixed until equilibrium was reached in each e Q K L K L flask . Samples were taken periodically each 30 minutes for measurement of aqueous-phase ammonia concentration. The amount of 3) In the third phase of runs, the cation ammonia accumulated on the Clinoptilolite selectivity of zeolite for ammonia to other was calculated by the following equation as the cations was investigated . One liter of 1M difference between the amounts present in the ammonia chloride solution was contacted with initial ammonia solution and that remained in 1 gram of conditioned sample with mesh 30. solution after equilibrium with the After mixing for 24 hours ammonia in solution Clinoptilolite: were measured with Nessler method and the ammonia adsorbed in solid phase in (C − C )V equilibrium condition was determined. Q = 0 e (2) M Simultaneously the ammonia equilibrium Where: concentration with addition of 1 M of Ca, Mg Q ( mg/g) is the amount of ammonia and K sal ts to sample in a separate stage was determined. Then the binary separation factor adsorbed is defined as the ratio of the distribution of ion C0 (mg/l) represents initial ammonia A between the solution and zeolite phases and concentration the distribution of ion B between these two Ce (mg/l) represents equilibrium ammonia phases: concentration V (l) is the volume of solution A q A C A M (g) is the mass of zeolite α B = (7) q B C B After the runs, the equilibrium point for each concentration will be selected. The Where q A is the amount of ion A adsorbed equilibrium removal of the ammonia ion to the zeolite (meq/g Clinoptilolite), CA the considered can be mathematically expressed in concentration of ion A in solution (meq/l), terms of adsorption isotherms. At equilibrium, qB the amount of ion B a dsorbed to zeolite the distribution of ammonia between the resin (meq/g Clinoptilolite), and CB the phase and solution phase can be described by concentration of ion B in solution (meq/l). The the Freundlich or the Langmuir isotherm separation factors between K, Ca, Mg and Na (Weber, 1972): to NH 4 were determined using the method described by Clifford (1990). 1/ n Q = K f Ce (3) Column studies or In the column studies, operational and K C Q = L e (4) regeneration parameters and ion-exchange 1+ aC e capacity of Clinoptilolite were investigated. Respectively, where: Thus 30 grams of conditioned zeolite in
( K f ), and ( l / n ) are indicative isotherm three mesh sizes 20, 30 and 40 were parameters of sorption capacity and intensity, transferred to three glass columns having 1cm respec tively ( K ) and ( a ) are Langmuir internal diameter by 60cm length. A peristaltic L pump was used and employed to feed the model parameters. ammonia chloride solution 100 mg /l
127 Investigation of ammonia removal… A. R. Rahmani, et al.
+ Table 2: Clinoptilolite capacity measurements recorded as mg of NH 4 per gram of dry Clinoptilolite in batch system Test M Mesh 20 Mesh 30 Mesh 40 No. Ce Q Ce Q Ce Q 1 0 1000 - 1000 - 1000 - 2 10 750 12.5 730 13.5 680 16 3 20 550 11.25 500 12.5 480 13 4 30 460 9.0 385 10.25 370 10.5 5 40 380 7.75 320 8.5 210 9.88 6 50 220 7.8 225 7.75 130 8.7 7 60 160 7.0 202 6.65 105 7.46 to the ion exchange column at the desired flow the up flow mode. The absence of ammonia in rate respectively. The ammonia concentration the effluent indicated the completion of of the samples collected from the column exit regeneration. Another loading cycle was then was monitored. The breakthrough curve so carried out. obtained was used to calculate the capacity of the zeolite for ammonia exchange. The basic Results experimental setup is shown in Figure 1. Batch studies
+ 1) The cation exchange capacity (CEC ) of 1- NH4 solution reservoir = 100 mg /l 2- Dosing pump the Semnan Clinoptilolite w as determined 3- Ion exchanger column 4- NaCl solution reservior from the batch system. Three measurements of the zeolite capacity were made for three different mesh sizes : 20, 30 and 40 mesh . The same preconditioning treatment and the same technique for measuring capacity was used for each mesh size, and the results obtained are tabulated in Table 2. The tests results showed that average ion exchange capacity for particles with 20, 30 and + 40 mesh were between 6.65 to 16 mg NH 4 /g zeolite weight. Furthermore the results showed that the rate of ion exchange has reverse Figure 1: Schematic description of the process relationship with the particle size. Thus the use (a - Ion Exchange phase, b - Regeneration p hase) of small particles increases the efficiency of processes. For determination of the effect of the 2) For determination of adsorption velocity on the ion exchange, three columns isotherms, the results obtained by using with 30 grams conditioned zeolite and mesh Equation (2) are plotted vs . time and shown in sizes of 20, 30 and 40 were used . The zeolite Figure 2. Th e equilibrium points for each columns were exhausted by down flow at three concentration are then selected. different superficial velocities of 5, 10 and 15- The equilibrium removal of the ammonia bed volume per hour (BV/h), until an ammonia + ion considered can be mathematically breakthrough of more than 2 mg /l NH 4 -N was expressed in terms of adsorption isotherms. achieved. The columns were then regenerated Plotting the experimental data using Equations with three different NaCl solutions (0.3, 0.5 (5) and (6) in Figures 3 and 4 indicates that and 1 M NaCl ) and at 10 BV /h. The both models give good fit for the data. regeneration was passed th rough the column in
128 Investigation of ammonia remov al…
25
1392 20 1170 970 780 15 530
mg NH 4/ g 405 zeolite 340 10 265
215 180
5 111 56
0
0 0 60 20 6 120 180 240 300 3 4 Time (minute)
Figure 2: Effect of initial ammonia concentration in the aqueous solution on the excha nge capacity
Figure 3: Linearised Freundlich isotherm for ammonia removal by zeolite
Figure 4: Linearised Langmuir isotherm for ammonia removal by zeolite
129 A. R. Rahmani , et al. Investigation of ammonia removal…
+ Table 3: Langmuir and Freundlich mode ls the level of 100 mg /l of NH 4 . The parameters for best fit and corresponding breakthrough curves of ammonia removal by correlation coefficients Clinoptilolite and for various velocities (5, 10 , 15 BV /hr .) of the aqueous solution are shown Kf 0.49 Freundlich model 1/n 0.475 in Figure 5 and 6 respectively . Changing the R2 0.981 flow rate fro m 5 to 10 and 15 BV /h resulted has no significant decrease in ammonia KL 0.081 Langmuir model a 0.007 adsorption capacity (Figure 6). R2 0.966 Regeneration Columns were prepared by complete The values of K , a, K and 1/ n that best L f regeneration with 0.3 , 0.5 and 1 M NaCl . fitted the data as well as the corresponding Ammonia elution by regenerate solutions is correlation coefficients are presented in Table shown in Figure 7. It is concluded that a 3. As a consequence, the Freundlich and volume of 3.5 liter 1 M NaCl solution is Langmuir isotherms for ammonia removal can sufficient for nearly complete regeneration of be represented by the following empirical the zeolite column. In lower concentration of equations 8 and 9 respectively: regenerate solution for complete regeneration of column, more volumes of regenerate 0.475 solution must be p assed through the ion Q = 0.49 Ce (8) exchanger bed. The results indicated that high and level of regeneration (95 -98% ) might be 0.081 Ce Q = (9) achieved with solution of NaCl. 1 + 0.007 Ce Discussion and Conclusion The separation factors between K, Ca, Mg and In this study, Semnan Clinoptilolite + Na to NH 4 were determined by using samples were tested in batch and continuous equation (7). The binary separation factors systems to evaluate their ability to adsorb wer e then obtained: ammonia from aqueous solutions. The removal of ammonia from synthetic solution was
NH 4 NH4 NH 4 demonstrated successfully on a laboratory α = 1 , αCa = 4.71 , αMg =8.17 , NH 4 scale with a selective ion -exchange process. NH α NH 4 = 2.3 , α 4 =0.85 (10 ) The results from batch studies showed that Na K the a verage of ion exchange capacity for samples have reverse relationship with the Column studies particle size and the use of small particles In continuous system, total cation exchange increases the efficiency of processes. and till breakthrough p oint capacity obtained + The data obtained from tests were applied 17.31 to 18.98 and 9.61 to 11.17 mg NH /g 4 to Langmuir and Freundlich isotherms. The zeolite weight. The results indicated that high Freundli ch isotherm gives an adequate level of regeneration (95 -98% ) might be correlation coefficient value compared to the achieved with solution of NaCl (Table 4). other. The concentrations of the solution for column studies were prepared synthetically at
+ Table 4: Clinoptilolite capacity measurements recorded as mg of NH 4 per gram of dry Clinoptilolite in continuous system
+ + + Test Zeolite Particle NH 4 , C 0 Breakthrough Total Total NH 4 Total NH 4 No. weight size (mg/l.) Capacity capacity adsorbed in regeneration (mg) (g) (Mesh ) (mg/g) (mg/g) column (mg) 1 30 20 101 9.61 17.31 519.3 507.63 2 30 30 101 10.06 18.38 551.4 539.37 3 30 40 101 11.17 18.98 569.4 558.37
130 Investigation of ammonia remov al…
120
100
80
NH 4 (mg/l) 60
40 mesh 20
mesh 30 20 mesh 40
0 0.5 1.5 2.5 3.5 4.5 5.5 6.5 7.5 Volume (Liter)
+ Fi gure 5: Clinoptilolite capacity measurements recorded as mg of NH 4 per gram of dry Clinoptilolite in continuous system
120
100
80
NH 4 (mg/l) 60
40 5 BV /hr
10 BV /hr 20 15 BV /hr
0 5 10 15 20 25 30 35 40 45 Time (hour)
+ Figure 6: Effect of the velocity on the breakthrough curve of NH 4 removal at 100 mg /l initial ammonia concentration
300
250
200
NH 4 ( mg /l) 150
ClNa =0.3 M 100 ClNa =0.5 M
50 ClNa =1M
0 012345678 Volume (Liter) Fi gure 7: Ammonia elution by regenerate solutions in column system
131 A. R. Rahmani, et al. Investigation of ammonia removal…
So t he results obtained from the cation Results of the experimental investigation selectivity of zeolite present high selectivity of are used to develop optimum operational + + the Clinoptilolite toward K and NH 4 while conditions for Clinoptilolite exchangers. Now much lower selectivity towards Na +, Ca 2+ and days , the most wastewater treatment plants in Mg 2+. Based on the separation factors results, Iran are designed only for removal of organic the following Clinoptilolite affinity order can matter and ammonia remain in effluent. The be written: use of ion exchange with Clinoptilolite can be + lead to an economical removal of NH 4 from + + + 2+ 2+ K > NH 4 > Na > Ca > Mg wastewater effluent.
The results obtained from column studies Acknowledgments showed that the total exchange capacity of the The authors would like to express their Semnan Clinoptilolite for three d ifferent mesh appreciation and thanks to the Department of sizes were determined between 17.31 to 18.98 Environmental Engineering, School of Pu blic + mg NH 4 /g of dry Clinoptilolite weight. The Health and Institute of Health Research Center, zeolite particles with mesh 40 gives a higher Tehran University of Medical Sciences for the ammonia adsorption capacity than that the valuable financial support. The great thanks others. The adsorption capacities calculated by also forwarded to Mr. H. Ehsani for his close graphical integr ation of the area above the Cooperation during the study. breakthrough curves are about 0.96 , 1.02 and + 1.05 meq/g NH 4 for particle sizes ranging References between 0.42 to 0.84 mm, respectively . This Ames, L. L., zeolite rem oval of ammonium ions indicates that the smaller particle size has a from agriculture wastewater . Proc . 13 th. Pacific higher ion -exchange capacity due to greater North West Indus. Waste Conf., Washington avail able surface area. The capacity to 2 mg /l University, 52 -135 , 1967 + NH 4 breakthrough was reached in 93 , 87 and AWWA, Water quality and treatment. Mc Graw Hill 83 BV for the samples column with velocities Co ., New York, 1990 of 5, 10 and 15 BV /h. respectively . As the velocity of the aqueous solution decreases, the Clifford D. A., Ion exchange and inorganic hydraulic residence time increases, resulting in ads orption, in water quality and treatment. + McGraw -Hill, AWWA, Washington D .C., 1990 more NH 4 being removed by the ion - exchange resin. These are reasonable velocities Culp, H. L., G. M. Wesner, and G. L. Culp, and have no negative effect on adsorption Handbook of advanced wastewater treatment . 2nd. capacity. The column regeneration phase Ed ., Van Nostrand Reinhold Co ., New York, 1978 carried out with 10 BV /h showed that in lower concentration of regenerate so lution for EPA, Process design manual for nit rogen control. U.S.EPA, Technology Transfer, 1975 complete regeneration of column, more volumes of regenerate solution must be passed Ershov A. V., Use of transcarpathin clinoptilotic through the ion exchanger bed. The results rock to remove ammonium nitrogen from indicated that high level of regeneration (95 - municipal sewage . Khim Technol, Vody, (6): 71 - 98% ) might be achieved with solution of NaCl . 75 , 1984 Three loading and three re generation cycles + Gaspard, M., A. Neveu and G. Martin, were carried out without loss of NH 4 Clinoptilolite in drinki ng water treatment for + adsorption capacity. This shows that on NH 4 removal. Water Res., 17 (3): 279 -288 , 1983 regeneration of the zeolite column with NaCl solution, the Na ions have activated the zeolite Haralambous A., E. Maliou and M., Malamis, The column . After the 2nd and 3rd regenerations, use of zeolite for ammonium uptake. Water Sci. Technol., 25 (1): 139 -145 , 1992 the loading process w as repeated and it was found that the ammonia adsorption capacity of Kazemian H., Chemical analysis, Characterization, the Clinoptilolite remained constant. This and det ermination of Ion -Exchange properties of indicates that using NaCl solution, the an Iranian Natural zeolite. M. S. thesis, regeneration of the column could be done Department of Chemistry, School of Sciences, repeatedly without loss of ammonia adsorption University of Isfahan, Iran, 1993 capacity. 132 Investigation of ammonia remov al…
Koon J. H., and W. J. Kaufman, Ammonium from an underg round mine water. Water SA., 12 removal from municipal wastewaters by ion (2): 73 -82 , 1986 exchange. J . WPCF 47 (3): 448 -465 , 1975 Singh G. and B. Prasad, Removal of ammonium Liberti L., Nutrient removal and recovery by ion from coke plant wastewater by using synthetic exchange. J. Water Res. 15 : 337 -342 , 1981 zeolite. Water Environ. Res., 69 (2): 157 -161 , 1997 Mercer, B. W., L. L. Ames, J. C. Touhill, W. J. Van Slyke and R. B. Dean, Ammonium removal from Standard Methods for the Examination of Water secondary effluents by selective ion -exchange. J. and Wastewater 18 th. Ed., American Public WPCF. 42 (2): R95 -R107 , 1970 Health Association, NW . DC ., 1992 Metcalf and Eddy, Wastewater Engineering: Weber W. J., Physicochemical processes for water Treatment and Reuse . 4th. Ed., Mc Graw Hill Co., quality control. Wiley Interscience, 9: 261 -304 , New York, 2003 1972 Schoeman J. J., Evaluation of a South African Clinoptilolite for ammonium -nitrogen removal
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