RECYCLING OF THE EXHAUSTED CATION EXCHANGE RESIN FOR STABILIZED LANDFILL LEACHATE TREATMENT

RECYCLING OF THE EXHAUSTED CATION EXCHANGE RESIN FOR STABILIZED LANDFILL LEACHATE TREATMENT Mohammed J.K. Bashir 1,*, Hamidi Abdul Aziz 2, Mohd Suffian Yusoff 3 1: Assistant Professor. Environ. Eng. Dept., Fac. Eng. Green Tech. (FEGT), Universiti Tunku Abdul Rahman, Perak, Malaysia. jkbashir@utar.edu.my; modbashir@gmail.com 2: Professor, School of Civil Eng., Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, MALAYSIA. cehamidi@eng.usm.my 3: Associate Professor, School of Civil Eng., Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, MALAYSIA. ABSTRACT Ion exchange is a reversible process. Thus, once the media becomes exhausted, it can be regenerated and the resin is returned to its original ionic form for reuse. Regeneration involves pollutants desorption from the media using processes that drive the pollutants from the media without destroying it. In previous studies, cation exchange resin was used for mature municipal landfill leachate treatment, particularly for ammoniacal-nitrogen (NH 3 -N) removal. The effectiveness of the media in NH 3 -N removal was promising. However, the most important disadvantage of cation resins was their high cost. Furthermore, storage or dumping of the exhausted media will significantly increase the related cost. Thus, the exhausted media regeneration is economically essential. In the present study, the experiments resolved the effects of several solvents (i.e. sulfuric acid (H2SO4), sodium chloride (NaCl) and distilled water) on the recovery efficiency of cationic resin, optimum concentration of the regenerant, optimum regeneration contact time, regenerant regeneration capacity and the maximum losses of resin after regeneration. The results indicated that cation exchange resin can be reused for several times with good recovery efficiency. After 5 times reuse, the cation exchanger regenerated via 0.5N H 2 SO 4 at 15min contact time achieved about 83.4% recovery efficiency for NH 3 -N from landfill leachate. Keywords: Regeneration, landfill leachate Treatment, INDION225Na, Recovery efficiency. 1

I. INTRODUCTION The application of ion exchange processes in municipal landfill leachate treatment was recently investigated [1-3]. The treatment of stabilized landfill leachate using resincationic, anionic, cationic followed by anionic (cationic-anionic), and anionic followed by cationic (anionic-cationic) were established and documented [3]. Response surface methodology (RSM) concerning central composite design (CCD) was used to optimize each treatment process and to evaluate the individual and interactive effects of operational variables on the effectiveness of each application in terms of colour, chemical oxygen demand (COD) and NH 3 -N removal efficiencies [1-3]. According to Bashir et al. [3], cationic resin was an effective media for NH 3 -N removal. The optimum cationic dosage, contact time and shaking speed were found to be 24.0 cm 3, 10 min and 150 rpm, respectively at which 68.9% colour, 38% COD and 91.8% NH 3 -N removals were achieved. Equilibrium removal data for NH 3 -N by cationic resin fitted well with Langmuir and Freundlich linear adsorption isotherms [1]. The results obtained from each kinetic model showed good compliance with the pseudo-second-order equation indicating that the rate of the sorption reaction was controlled by the second-order mechanism which indicated a chemical sorption [1]. In general, ion exchange is a reversible process. Thus, once the media becomes exhausted, it can be regenerated and the resin is returned to its original ionic form for reuse. Typically, regeneration involves pollutants desorption from the media using processes that drive the pollutants from the media without destroying it. Grote and Schumacher, [4] reported that an ion exchange resin is expensive. However, in most cases, the ion exchanger is reused many times in cyclic operations. Thus, the regeneration and ruse of the resin is often cost-effective. Thermal and chemical processes can be used for media regeneration. However, thermal regeneration of ion exchangers may result in incomplete regeneration and damage to the structure. Due to thermal degradation, this method is only useful for the zeolites and not for the organic resins. For example, Wang et al. [5] recovered about 88% of zeolite capacity (used in dye removal) by thermal process at 540 o C after duration of 1 h. Meanwhile, chemical process (solvent wash) is the most common method used for the regeneration of ion exchange resins due to its efficiency. In chemical regeneration, the exhausted resins are subject to a solution containing a high concentration of the original ions. Later, the resin is subject to rinsing with distilled water to remove loosely bound ions and traces of the regenerant solution [6]. According to Ryoo et al. [7], the countercurrent regeneration is a very effective system for the regeneration of exhausted media. The results indicated that the capacity of the exhausted media was completely recovered. Several solvents are used for resins regeneration including HCl, H 2 SO 4, HNO 3 and NaCl (for cationic resins) and NaOH and NaCl (for anionic resins). Celik et al. [8] used HCl and NaCl as solvents to desorb ammonia from natural clay minerals (sepiolite and clinoptilolite). The results indicated that all the regenerants used (HCl and NaCl) achieved removals well compared to the untreated sepiolite. The results also showed that regenerated clinoptilolite was able to remove 2

ammonia from both synthetic and actual water at a much higher rate than the untreated clinoptilolite. According to Sapari et al. [9], the Amberlite IR- 120 and Dowex 2-X4 were used as the cation and anion exchanger for heavy metals removal from mixed plating rinse wastewater. The exhausted media were effectively regenerated by using 2% H 2 SO and 5% NaOH for the cationic and anionic exchangers, respectively. Zagorodni [10] mentioned that the efficiency of the regeneration method can be characterized by the following factors: i. Required amount (volume and concentration) of the solvent ii. Degree of the exchanger conversion i.e. which part of sorbed substances is recovered from the material and which part of the sorbent is converted to the new ionic form iii. Concentration of the effluent According to the literature, one of the most significant drawbacks of cation exchange resin utilization in treatment processes is its cost. Therefore, the present study aimed to investigate the effectiveness of the exhausted media regeneration in order to be reused several times in ammonia removal from stabilized landfill leachate. II. MATERIALS AND METHODS Sampling The study was conducted on a semi-aerobic stabilized leachate sample from Pulau Burung Landfill Site (PBLS) in Nibong Tebale, Penang, Malaysia. PBLS is in Penang, Malaysia which is around 20 km southeast from the Penang Island. PBLS is located near shoreline approximately 50m from the Straits of Malacca. The site location is shown in Figure 1. PBLS normally received MSW that collected from Penang state. Leachate samples were collected manually (20L per sample) from PBLS aeration pond. In accordance with the Standard Method of Water and Wastewater Examination, the samples were immediately transported to the USM Environmental Engineering Laboratory and stored in a cold room at 4 C prior to experimental use in order to minimize biological and chemical reactions. All chemical analyses for leachate characterization were carried out within the following 24 hours. The samples were analyzed for COD, NH 3 -N, colour, turbidity, SS, ph and conductivity according to the Standard Methods for the Examination of Water and Wastewater [11]. 3

Figure 1: Satellite image of PBLS Resins Properties: The cationic exchanger INDION 225 Na is an available synthetic ion-exchanger resin were used in this study. The resin was supplied by Ion Exchange (INDIA) Ltd. The physicochemical properties are presented in Table 1. The INDION 225 Na (gel-type) was chosen due to its characteristics such as its capability to work as a strong acid cation resin if used in hydrogen form, its ability to be used in both hydrogen form (cation resin carry H + mobile ion) and sodium form (cation resin carry Na + mobile ion) and its potential applications over wide range of ph levels and temperatures. Conventional ion exchange resin (gel-type) has relatively homogenous polymer density across the bead. The gels have no pore structure; however, the molecular and nanoscale open areas between the hydrocarbon chains are usually designated as pores without considering the true geometry. Instead, these resins depend on a polar solvent, which causes the matrix to swell for pores to be established [12]. 4

Table 1: The main physico chemical properties of the studied resin Type Matrix Property INDION 225 Na strongly acid cation exchange resin cross-linked polystyrene, gel type Functional group sulphonic acid (-SO 3 - ) lonic form (as supplied) Sodium form Maximum operating Temperature 120 o C (H + form) 120 o C (Na + form) Operating ph range 0-14 Particles size range (mm) 0.3-1.2 Total exchange capacity (meq/ml) 2.0 Particle size (mm) 0.3-1.18 Particle density (g/cm 3 ) 1.328 Bulk density (g/cm 3 ) 0.81 Specific gravity 1.328 Moisture content (%) 48.5 Void ratio (%) 39.0 Surface area (m 2 /g) 0.0996 ph 3.7 Cation exchange capacity (meq/g) 1.89 Appearance Yellow Experimental Procedure: Treatment of stabilized leachate samples that collected from PBLS were studied by a batch experiment technique. The experiments were carried out after pre-treating the cationic exchange resin as discussed by Bashir et al. [13]. The batch experiments were carried out by shaking 100 ml of raw stabilized leachate sample in a 250 ml volumetric flask by using an orbital shaker (model PROTECH 720, Malaysia). The raw leachate samples used in this study were not subjected to any pretreatment process prior to ion exchange. Different concentrations of H 2 SO 4 and NaCl solutions [6, 9] were used for the regeneration of exhausted strong cationic exchanger in this study. On the other hand, NaCl and NaOH solutions [8-9] of different concentrations were used for the regeneration of the exhausted media The media was shaken with sufficient amount of leachate until the media was exhausted after about 1hr. The particles of the adsorbent were removed, washed and air dried. 1M concentration solvents were used based on the preliminary experiments. The dried exhausted media was introduced into 250mL conical flasks each containing 200mL of regenerate. Control tests were performed by repeating all the procedures using fresh media. 5

The media were separated from the regenerants via filter paper, washed and air dried for 24 hrs. Later, the removal efficiencies of the regenerated media were tested by repeating the adsorption process. The regeneration ratio was considered by the following equation: removal percentage of regenerated media Recovery efficiency (%) = 100 removal percentage of fresh media (1) Consequently, the most effective/suitable regenerant, optimum concentration of the chosen suitable solvent, and optimum contact time were selected based on the highest regeneration ratio for NH 3 -N. III. RESULTS AND DISCUSSION Leachate Characterization: Stabilized leachate generated from PBLS had a high concentration of COD and high colour intensity due to the presence of high molecular weight organic compounds (Table 2). The concentration of NH 3 -N was also high in raw leachates (1630 2200mg/L). The characteristics demonstrated that the amount of contaminants exceeded the Malaysian discharge limits as stipulated by the Environmental Quality (Control of Pollution from Solid Waste Transfer Station and Landfill) Regulations 2009, under the Laws of Malaysia-Malaysia Environmental Quality Act 1974 [14]. Table 2: Characteristics of raw leachate from PBLS Parameters Units Feb 2008- May 2010 (23 samples) Standard* Values Average ph --- 8.30 9.17 8.58 6.0-9.0 COD mg/l 1810-2850 2321 400 NH 3 -N mg/l 1630-2200 1949 5 Colour Pt-Co 4250-5760 5094 100 Turbidity FAU 128-330 211 ----- SS mg/l 114-360 181 50 Conductivity µs/cm 21850-26230 24340 ---- *Environmental Quality (Control of Pollution from Solid Waste Transfer Station and Landfill) Regulations 2009, under the Laws of Malaysia-Malaysia Environmental Quality Act 1974 [14]. 6

Effectiveness of INDION 225 Na regeneration and reuse for NH 3 -N removal form landfill leachate The optimum results attained from the previous study [1] indicate that 6.0 min of contact time was required to achieve 94.2 percent of NH 3 -N removal when the cationic resin dosage and shaking speed were 24.6 cm 3 and 147 rpm, respectively. However, in the present study, 1 hr was used as contact time for shaking the media with sufficient amount of leachate in order to make sure that the media is exhausted. Subsequently, the exhausted media was taken and washed via several solvents i.e. sulfuric acid (H 2 SO 4 ), sodium chloride (NaCl), and distilled water in order to investigate the recovery efficiency of cationic resin (Figure 2). The figure illustrates that H 2 SO 4 gave a high degree of NH 3 -N recovery from cationic resin with recovery efficiency of 98.3%. Sodium chloride (NaCl) exhibited high level of NH 3 -N recovery (89.6%). About 63% of NH 3 -N was recovered when cation resin was washed by distilled water only. The results of parameter s recoveries demonstrate that H 2 SO 4 gave the best result. The high influence of H 2 SO 4 in cation resin regeneration indicated that cation resin in H + form gave better removal efficiencies of NH 3 - N than those obtained via cation resin in Na + form. The effectiveness of the regeneration process using different concentrations of H 2 SO 4 was evaluated in this study. Figure 3 displays the effect of the changeable initial concentration (0.1 0.6 N) on the recovery efficiency of NH 3 -N from cation resin. As can be seen in Figure 3, the recovery efficiency of the regenerant solutions was 96.5% for NH 3 -N. This optimum condition was obtained at H 2 SO 4 concentration of 0.50 N. Experiments were carried out using 0.5N H 2 SO 4 solution at different regeneration contact times for cation resin regeneration in order to assess the corresponding optimum regeneration contact time as demonstrated in Figure 4 with H 2 SO 4 solution. Figure 2: Influence of solvents in cation resin regeneration (solvent volume, 200mL; media volume, 25cm 3 ; solvent concentration, 1N; contact time, 1hr) 7

Figure 3: The influence of H 2 SO 4 concentration on cation resin regeneration (solvent volume, 200mL; media volume, 25cm 3 ; contact time, 1hr). Figure 4: The influence of contact time on cation resin regeneration by H 2 SO 4 (solvent volume, 200mL; media volume, 25cm 3 ; H 2 SO 4 concentration, 0.5N) The results indicate that only a small increment in recovery efficiency was observed after 15min. The contact time of 15min appeared to be the optimal regeneration contact time. The influence of recycling times or the reuses of ctaion resin on the recovery efficiency of NH 3 -N are demonstrated in Figure 5. The figure indicates that cation exchange resin can be reused for several times with good recovery efficiency. After 5 times reuse, the cation exchanger regenerated via 0.5N H 2 SO 4 at 15min contact time achieved about 83.4% recovery efficiency for NH 3 -N. The high recovery efficiency can be attributed to the stability of cation resin structure which was tested via FTIR spectrum as illustrated in Figure 7. 8

Figure 5: The influence of number of recycling on cation resin regeneration by H 2 SO 4 (solvent volume, 200mL; media volume, 25cm 3 ; H 2 SO 4 concentration, 0.5N; time, 15min) Figure 7: FTIR spectra of cation resin before and after leachate treatment 9

The FTIR spectrum of the resin shows bands at 3446cm 1 which is attributed to O-H and N-H stretching vibration, 2930cm 1 (attributed to the C-H stretching), 1639cm 1 (assigned to -C=O group) and 1180-1008cm 1 (-O=S-O) which are assigned to the sulphonic group [15-16] O-H and C-O bending (in-plane) was detected at 1412cm 1 [15-16]. The sharp peak in cation resin after treatment at 1400cm 1 + may due to the NH 3 deformation. The differences in the band frequencies for cation and anion resin before and after treatment were insignificant. This indicated that the physical and chemical structure of the media did not change. Thus, the used resin can be reused after regeneration. IV. CONCLUSION The most important disadvantage of using ion exchange resins in landfill leachate treatment is their high cost. Furthermore, storage or dumping of the exhausted media will significantly increase the related cost. In the present study, the experiments resolved the appropriate regenerant, optimum concentration of the regenerant, optimum regeneration contact time, and regenerant regeneration capacity. The maximum recovery efficiency of the regenerant solutions was 96.5% for NH 3 -N. This optimum condition was obtained at H 2 SO 4 concentration of 0.50 N. The contact time of 15min appeared to be the optimal regeneration contact time. After 5 times reuse, the cation exchanger regenerated via 0.5N H 2 SO 4 at 15min contact time achieved about 83.4% recovery efficiency for NH 3 -N. The high recovery efficiency was attributed to the stability of cation resin structure. Thus, it can be concluded that the exhausted media regeneration is economically essential. V. REFERENCES [1] Bashir, M.J.K., Aziz, H.A., Yusoff, M.S., Adlan, M.N. Application of response surface methodology (RSM) for optimization of ammoniacal nitrogen removal from semi-aerobic landfill leachate using ion exchange resin : Desalination, 2010, 254, 154-161. [2] Bashir, M.J.K., Aziz, H.A., Yusoff, M.S., Aziz, S.Q., Mohajeri. S. Stabilized Sanitary Landfill Leachate Treatment Using Anionic Resin: Treatment optimization by Response Surface Methodology : Journal of Hazardous Materials, 2010, 182, 115 122. [3] Bashir, M.J.K., Aziz, H.A., Yusoff, M.S. New sequential treatment for mature landfill leachate by applying cationic/ anionic and anionic/ cationic processes: optimization and comparative study : Journal of Hazardous Materials, 2011 doi:10.1016/j.jhazmat.2010.10.082. [4] Grote, M., Schumacher, U. Bipolar ion- exchange resins based on functional acidic tetrazolium groups-their synthesis, structure and properties : Reactive & Functional Polymers, 1997, 35, 179-196. [5] Wang, S., Li, H., Xie, S., Liu, S., Xu, L. Physical and chemical regeneration of zeolite adsorbents for dye removal in wastewater treatment : Chemosphere, 2006,65, 82-87. 10

[6] Jorgensen, T.C. Removal of ammonia from wastewater by ion exchange in the presence of organic compounds. Msc. thesis. Chemical & Process Engineering, University of Canterbury Christchurch, New Zealand, 2002. [7] Ryoo, K.S., Kim, T.D., Kim, Y.H. Regeneration of exhausted activated carbon by a countercurrent oxygen reaction : bull. Korean Chem. Soc., 1999, 20 (12), 1447-1450. [8] Celik, M.S., Ozdemir, B., Turan, M., Koyuncu, I., Atesok, G., Sarikaya, H.Z. Removal of ammonia by natural clay minerals using fixed and fluidized bed column reactors : Water Science and Technology: Water Supply, 2001, 1, 81-88. [9] Sapari, N., Idris, A., Hamid, N.H.A. Total removal of heavy metal from mixed plating rinse wastewater : Desalination, 1996, 106, 419-422. [10] Zagorodni, A.A. Ion Exchange Materials: properties and applications : Elsevier publisher, online Book, 2006. [11] APHA: Standard Methods for the Examination of Water and Waste Water : 21 th ed., American Public Health Association, Washington D.C, 2005. [12] Helfferich, F. Ion Exchange : McGraw-Hill Book, USA, 1962. [13] Bashir, M.J.K., Aziz, H.A., Yusoff, M.S., Huqe, A.A.M., Mohajeri. S. Effects of ion exchange resins in different mobile ion forms on semi-aerobic landfill leachate treatment : Water Science & Technology, 2010, 61, 641-649. [14] Environmental Quality (Control of Pollution from Solid Waste Transfer Station and Landfill) Regulations 2009, under the Laws of Malaysia-Malaysia Environmental Quality Act 1974. [15] Sacmacia, S., Sacmacib, M., Soykanb, C., Kartala, S. Synthesis and characterization of new chelating resin: adsorption study of copper (II) and chromium (III) ions : Journal of Macromolecular Science, Part A, 2010, 47, 552-557. [16] Viswanathan, N., Meenakshi, S. Role of metal ion incorporation in ion exchange resin on the selectivity of fluoride : Journal of Hazardous Materials, 2009, 162, 920-930. 11