Results and Discussion 1 Motive 2 Objective 3 Materials 4 Experiments 5 Results and Discussion 6 Environmental Implications

1 Motive 1 Motive

Motive Medicine Animal husbandry 1 Motive Used 1831 tons in Germany.(1994) 181 tons in Denmark.(1995) 13288 tons in EU. (1999) 16200 tons in USA, (2000) 28000 tons in China. (2003) Medicine Animal husbandry Threat and Impact Increase bacterial resistances to antibiotics. Restrain vegetation growth. Cancer, deformity, mutation. Thus, the removal of antibiotics from soil and water, particularly from drinking water or groundwater, is becoming an emerging issue.

2 objective 2 Objective

Rectorite Illite TC SYn-1 SAz-1 SHCa-1 SWy-2 palygorskite 1 objective 1 Rectorite Although extensive studies were conducted to investigate the mechanisms of antibiotic adsorption on swelling clays, no systematic research was reported on desorption of TC from these clays. In this study, the desorption of TC from a swelling clays SAz-2 was tested under different kinetic conditions, different pH, and in the presence of different desorbing agents in order to see the stability of TC adsorbed on the surface and in the interlayer of swelling clays. Illite palygorskite 7 2 TC SYn-1 SAz-1 6 3 SHCa-1 a synthetic mica- montmorillonite SWy-2 a high charge Ca- montmorillonite 4 5 a Li- bearing trioctahedral smectite a low charge Na- montmorillonite

3 materials 3 Materials Adsorbent SAz-2 Adsorbate Tetracycline

SAz-2 clays CEC(meq/kg) Rectorite 410 PFL-1 165 SAz-2 1230±3 SHCa-1 materials The sorbent used was a Ca-montmorillonite SAz-2, a dioctahedral smectite, obtained from Clay Minerals Society, and was used as received without further purification. Cation exchange capacity (CEC) ： 1200 meq / kg clays CEC(meq/kg) Rectorite 410 PFL-1 165 SAz-2 1230±3 SHCa-1 66±4 SWy-2 850±3 SYn-1 700~1400 IMt-2 100 montmorillonite

Tetracycline D C B A + Property~ pKa1=3.3 pKa2=7.7 pKa3=9.7 materials pKa3 = 9.7 + D C B A NHMe2 OH Property~ pKa1=3.3 pKa2=7.7 pKa3=9.7 pKa2 = 7.7 pKa1 = 3.3 1.0 acid dissociation constant - +  TCH TCH3 TCH2 TC 2- The capacity of acid dissociation H+ 0.8 HA(aq) + H2O(l) H3O(aq)+ + A-(aq) 0.6 Fraction 0.4 pKa=-logKa 0.2 It bears different charges on different sites depending on solution pH. 0.0 2 3.3 4 6 7.7 8 9.7 10 12 pH

Desorbing agents and instruments 4 experiments 4 Experiments Batch experiment Batch studies Batch conditions Desorbing agents and instruments

Batch experiments-batch studies 4 experiments TC desorption from SAz-2 脫附 動力式脫附 反覆脫附 效應 Kinetic of desorption Effect of Repetitive Desorption pH值效應 Effect of pH on TC desorption

Batch experiments-batch conditions 4 experiments Kinetic of Desorption Initial concentration ( Ci ) = 3000 ppm. Time : 0.25, 0.5, 1, 2, 4, 8 and 24h. Solid / Solution = 0.1 g / 20 mL. TC Desorption from SAz-2 Ci = 100, 200, 400, 600, 800, 1000, 1500, 2000, 2500 and 3000 ppm. Time : 24h. Solid / Solution = 0.1 g / 20 mL. Effect of pH on TC Desorption Ci = 1000 and 3000 ppm. Time : 24h. Solid / Solution = 0.1 g / 20 mL. pH = 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11. ( ±0.2 ) Effect of Repetitive Desorption Cycle time : 6, 12, 18, 24 and 30h. Time : 24h. Solid / Solution = 0.1 g / 20 mL.

Desorbing agents and instruments 4 experiments Desorbing agents instruments AlCl3 UV-VIS CaCl2 wavelength standards TC : 254nm CIP : 275nm TC : 5, 10, 20, 25 and 50 ppm CIP : 2, 4, 6, 8, 10 and 15 ppm NaCl XRD 0.05M angle speed 2~10° 1° 2θ/min

Results and discussion 5 Results and discussion 5 Results and discussion

Results and discussion Effect of pH on TC Desorption 5 Results and discussion Equilibrium Time (h) Amount TC Desorbed (mg g-1) 20 40 60 80 100 120 140 5 10 15 25 AlCl3 Kinetic of desorption CaCl2 TC Desorption from SAz-2 NaCl Effect of pH on TC Desorption Figure 1. Desorption kinetics of TC from SAz-2 by AlCl3 (), CaCl2 () and NaCl () at an initial TC loading of 400 mg g-1. The lines are pseudo-second order fit to the observed data. Effect of Repetitive Desorption Desorbing agents Initial rate (mg g-1 h-1) Rate constant (g mg-1 h-1) qe (mg g-1) r2 Time to reach equilibrium (h) AlCl3 2000 0.104 139 1.000 6 CaCl2 313 0.042 86 0.999 NaCl 263 0.094 53 XRD Analyses

Results and discussion Effect of pH on TC Desorption 5 Results and discussion (b) 20 40 60 80 100 120 140 50 150 200 250 300 350 400 450 Amount TC Initially Adsorbed (mg g-1) Amount TC Desorbed (mg g-1) (a) 500 600 800 1000 Equilibrium TC concentration (mg L-1) TC Adsorbed (mg g-1) AlCl3 133±4 mg g-1 Kinetic of desorption CaCl2 83±6 mg g-1 TC Desorption from SAz-2 NaCl 50±4 mg g-1 Effect of pH on TC Desorption Figure 2. TC adsorption on SAz-2 (a), and TC desorption from SAz-2 at different initial loadings by AlCl3 (), CaCl2 (), and NaCl() (b). Effect of Repetitive Desorption The results indicated that ions with high charge could desorb more TC in comparison to low charged ones. XRD Analyses The results from this study further confirmed that cation exchange as the major mechanism for TC desorption from SAz-2.

Results and discussion Effect of pH on TC Desorption 5 Results and discussion 280 300 1.0 - Desorption from 400 mg g-1 TCH 0.8 + 250 TCH3 TCH2  2- pka3 Kinetic of desorption 0.6 TC Adsorption equilibrium 0.4 pka2 200 0.2 Desorption from 187 mg g-1 Amount TC Desorbed (mg g-1) 0.0 150 2 4 6 8 10 12 3.3 7.7 9.7 TC Desorption from SAz-2 pH 157 Adsorption non-equilibrium 100 pka1 50 50 Figure 3. TC desorption from SAz-2 as affected by solution pH at initial TC loadings of 187 mg g-1 () and 400 mg g-1 (). Effect of pH on TC Desorption 26 2 3 4 5 6 7 8 9 10 11 Solution pH Effect of Repetitive Desorption The pH of a solution is an important factor that can affect the form and the quantity of TC in water. Previous research showed that TC adsorption decreased significantly when solution pH was greater than the pKa2 of TC. XRD Analyses The quick increase in TC desorption in this study agreed well with previous TC adsorption study. At pH 11, about 70% of previously adsorbed TC was desorbed.

Results and discussion Effect of pH on TC Desorption 5 Results and discussion (a) (b) Kinetic of desorption 100 Desorption from 400 mg g-1 Desorption from 187 mg g-1 40 80 30 60 TC Desorption from SAz-2 Amount TC Desorbed (mg g-1) Amount TC Desorbed (mg g-1) 20 40 10 20 Effect of pH on TC Desorption 1 2 3 4 5 1 2 3 4 5 cycle cycle Figure 4. TC removal by AlCl3 (), CaCl2 (), NaCl (), and distilled water () under different desorption cycles at initial TC loadings of 187 mg g-1 (a) and 400 mg g-1 (b). Effect of Repetitive Desorption A systematic decrease in the amount of TC desorbed as the number of repetitive desorption increased, reflecting progressive difficulties in TC removal from the external surfaces or interlayer spaces of SAz-2. XRD Analyses

Results and discussion Effect of pH on TC Desorption 5 AlCl3 CaCl2 NaCl Results and discussion 24 h 8 h 4 h 2 h 1 h .5 h .25 h Kinetic of desorption Intensity( cps) TC Desorption from SAz-2 (a) (b) (c) No d-spacing change 2θ (º) 2θ (º) 2θ (º) Adsorption Effect of pH on TC Desorption 22 Å Non-equilibrium Equilibrium (d) TC-SAz-2 Al Ca Na CIP (f) (e) 2θ (º) Intensity( cps) Effect of Repetitive Desorption XRD Analyses Figure 5a. X-Ray diffraction patterns of SAz-2 desorbed by 0.05 M AlCl3 (a), CaCl2 (b), and NaCl (c) at different time; desorbed by different agents from SAz-2 at TC loading levels of 19 (d), 150 (e), and 332 mg g-1 (f).

Results and discussion Effect of pH on TC Desorption 5 Results and discussion AlCl3 CaCl2 NaCl Water (h) 1 2 3 4 5 (g) (j) (i) 2θ (º) Intensity( cps) Kinetic of desorption TC Desorption from SAz-2 Effect of pH on TC Desorption Figure 5b. X-Ray diffraction patterns of SAz-2 desorbed by 0.05 M AlCl3 (g), CaCl2 (h), NaCl (i), and water (j) under different desorption cycles. Effect of Repetitive Desorption The XRD patterns gave strong evidences that TC intercalation in SAz-2 was very stability while the desorbed TC almost came from SAz-2 surfaces. XRD Analyses

Environmental implication 6 Environmental implication 6 Environmental Implication

Environmental implication 6 Environmental implication Montmorillonite is one of the most important minerals present in soils and sediments. Application of animal manure containing non-degraded antibiotics may result in retention of antibiotics on the surface and in the interlayer of montmorillonite. The data collectively from this study suggested that TC intercalation in SAz-2 was highly stable while the desorbed TC largely came from the surface in the presence of multivalent cations. The stable form of antibiotic retained in the interlayer and the slow release of antibiotics from the surface may induce further antibiotic resistance of the environmental microbes and even change the microbial community in the soil. Moreover, competitive sorption and interaction of various antibiotics and metal cations within swelling clays may vary in different soil and sediment environments and worth further studies.

Conclusions The maximum TC desorption from SAZ-2 were 137, 89 and 54 mg/g or 310, 201 and 122 mmol/kg for 0.05M AlCl3, CaCl2 and NaCl, respectively. The TC desorption was on the external surfaces of SAz-2. Desorption of TC from SAz-2 was strongly dependent on solution pH. The desorption amounts of TC were abruptly increase when solution pH was higher than the pKa2 of TC and the desorption capacity can reach to 280 mg/g. XRD analyses showed no basal spacing changes after desorption, further confirming that the desorption was on the external surfaces again.

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