Materials-palygorskite, tetracycline 1. Goal 2. Outline Result and discussion 3. Batch study IC XRD TG FT-IR Kinetic adsorption Isotherm adsorption Desorbed cation pH edge adsorption effect Ionic strength effect Temperature effect

Materials 1 一. Materials 1.clay:playgorskite 2.tetracycline

Materials-clay Palygorskite 1 Palygorskite Palygorskite is a special type of clay made of periodic reversal of the building block so that the interlayer space is made of one dimensional channel, thus limiting its expandability. Even though, it is still a good adsorbent for a variety of compounds. SEM:short fiber﹛~0.1μm wide and 1-2μm long﹜

Materials-antibiotic 1 Materials-antibiotic D C B A NHMe2 OH pKa2 = 7.7 pKa3 = 9.7 pKa1 = 3.3 + Tetracycline (TC) Properties~ pKa1=3.3 0.0 0.2 0.4 0.6 0.8 1.0 2 4 6 8 10 12 pH Fraction TCH3 + TCH2  TCH - TC 2- pKa2=7.7 pKa3=9.7 +00 +-0 +-- 0-- Fig. 1. Molecular structure of TC on an planar view A(a) and speciation under different pH (b). 3.3 7.7 9.7

二. Goal Rectorite Illite TC SYn-1 SAz-1 SHCa-1 SWy-2 palygorskite 7 2 TC The goal of this research is to study the adsorption of TC on palygorskite under different physical and chemical conditions in conjunction with X-Ray diffraction (XRD) and Fourier transform infrared (FTIR), in order to access the feasibility and applicability of using palygorskite as a potential adsorbent to treat wastewater containing higher amounts of TCs. 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

Result and discussion-kinetic adsorption 3 Ci:200ppm Amount TC Sorbed (mg/g) Equilibrium Time (h) 6 12 18 24 30 5 10 15 20 25 y = 0.0347x + 0.0083 r2= 0.9992 0.0 0.2 0.4 0.6 0.8 1.0 t/qt (h-g/mg) 2 equilibrium 24 Fig. 1. Sorption kinetics of TC on palygorskite. The solid line is pseudo-second order fit to the observed data.

Result and discussion- Langmuir sorption isotherm 3 Result and discussion- Langmuir sorption isotherm 20 40 60 80 100 200 300 400 500 600 700 pH=8.7 pH=1.5 pH=6 pH=11 Amount TC Sorbed (mg/g) Equilibrium TC Concentration (mg/L) TCH- TCH3+ At pH 8.7, although the TC is in its anionic form TCH-, its sorption reached a Maximum of 210 mmol/kg. Due to the presence of positively charged functional group of dimethylammonium, cation exchange may still play a role. TCH20 TC2- Fig. 2. Sorption isotherm of TC on palygorskite at pH1 (), 4-5 (), 8.7 (), and 11 ().The lines are Langmuir fit to the observed data.

Result and discussion- IC data: pH=6 3 Result and discussion- IC data: pH=6 50ppm 100ppm 200ppm 400ppm 600ppm 800ppm The extra Ca2+ desorption associated with TC sorption could be attributed to the Replacement of H+ for Ca2+ as the TC used is in HCl form. Fig. 3. Amount of Na (), K (), Mg () Ca (), and total cation ( ) desorbed as affected by TC sorption on palygorskite.

Result and discussion- effect of pH on TC sorption edge 3 Result and discussion- effect of pH on TC sorption edge Ci:200ppm 8 9.5 The trend in TC sorption as effected by pH agrees well with the TC sorption isotherm study. Fig. 4. Sorption of TC on palygorskite as affected by solution pH.

Result and discussion- effect of ionic strength on TC sorption 3 Result and discussion- effect of ionic strength on TC sorption Amount TC Sorbed (mg/g) Log (Ionic strength as NaCl, log(mol/L) y = -5.2x + 18 r2=0.95 20 25 30 35 -3 -2 -1 50.0 62.5 75.0 87.5 Percentage of TC Sorbed 82% of the input TC was removed from water 56% of the input TC was removed from water 0.01M 0.001M 0.1M Fig. 5. Sorption of TC on palygorskite as affected by solution ionic strength. The line is just a linear fit on a semi-log scale showing reverse relationship between TC sorbed and solution ionic strength. The competing of present ion against TC for sorption sites shows that part of the TC sorption was due to ion exchange mechanism, same as that observed for TC sorption on rectorite and montmorillionite.

Result and discussion- effect of temperature on TC sorption 3 Result and discussion- effect of temperature on TC sorption 55℃ 40℃ 25℃ 11 Ci:200ppm pH=1.5 10 pH=6 y = -12522x + 48.487 9 R 2 = 0.9307 y = -9061.6x + 37.025 8 2 pH=8.7 R = 0.937 Ln Kd (L/kg) 7 y = -2738.2x + 16.136 pH=11 2 6 R = 0.6002 The small positive S indicates that the sorption is spontaneous due to an increase in system randomness as TC molecules remove themselves from water onto solid surfaces. 5 y = -5936.1x + 24.35 R 2 = 0.8112 4 0.0030 0.0031 0.0032 0.0033 0.0034 1/T (1/K) Fig. 6. Influence of temperature on TC sorption on palygorskite. Positive: Endothermic process Negative:spontaneous

Result and discussion- XRD analyses 3 Result and discussion- XRD analyses 700 1400 2100 2800 3500 4200 2 6 10 14 18 22 26 30 2θ (º) Intensity (cps) pH 11 pH 8.7 pH 6 pH 1.5 Raw PFl-1 d110=10.53 Å 8.4 Fig. 7. X-Ray diffraction patterns of palygorskite after treated with TC at an initial concentration of 800 mg/L at different pH conditions.

Result and discussion- XRD analyses 3 Result and discussion- XRD analyses These results are completely different from those of TC sorption on montmorillionite (Porubcan et al. 1978; Kulshrestha et al. 2004), on soils (Pils and Laird, 2007), and on rectorite(Chang et al. 2008). 700 1400 2100 2800 3500 4200 2 6 10 14 18 22 26 30 800 mg/L 600 mg/L 400 mg/L 200 mg/L 100 mg/L 50 mg/L Raw PFl-1 The invariability of d-spacing after adsorbing different amounts of TC at different pH conditions suggest that the uptake of TC by palygorskite is on the external surface. Intensity (cps) 2θ (º) Fig. 8. X-Ray diffraction patterns of palygorskite after treated with TC at different initial concentrations at neutral pH.

Derivative of mass (g/min) result 3 Result and discussion-Derivative of thermogravimetric (DTG) analyses 350 If the Tpeak at 205 ℃ is thought as a composite peak made of 214 ℃ for the removal of zeolitic water and the decomposition of TC at a slightly lower temperature, the thermal stability of the TC sorbed on PFL-1 is less stable compared to crystalline TC. 300 Dehydration temperature Dehydroxylation temperature 250 83℃ 420℃ 200 220℃ Derivative of mass (g/min) 150 Raw PFL-1 pH1.5 pH6 pH8.7 Crystalline TC 600℃, mass loss is 56% 100 214℃ 50 205℃ 20 120 220 320 420 520 620 decomposition temperature (Tpeak) :230℃。Mass loss is 25% T℃ Fig. 9. Derivative of thermogravimetric analysis of raw PFL-1, and PFL-1 with TC adsorbed at an initial concentration of 800 mg/L and pH 1.5, pH 6, and pH 8.7. Also drawn is the DTG of crystalline TC, whose vertical scale is reduced by 50%.

Result and discussion-FT-IR 3 20 40 60 80 100 400 800 1200 1600 2000 2400 2800 3200 3600 4000 pH 11 pH8.7 pH6 pH1.5 PFl-1 Wave number (cm–1) Transmittance (%) TC The TC vibrations were much weaker compared to that sorbed to montomorillonite (Kulshrestha et al. 2004) and rectorite (Chang et al. 2008), → indicating that less amount of TC was adsorbed on PFL-1. Figure 8. FTIR spectra of palygorskite after equilibrated with TC at an initial concentration of 800 mg/L at different pH.

Result and discussion-FTIR 3 Result and discussion-FTIR 20 40 60 80 100 1250 1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 pH 11 pH8.7 pH6 pH1.5 PFl-1 TC Wave number (cm–1) Transmittance (%) The most characteristic peaks are those in 1250–1750 cm–1. At a solution pH of 1.5, the bands at 1311, 1356, 1456, 1524, 1579 and 1616cm−1 all shifted about 10–15 cm−1 to higher frequencies. A shift to higher frequencies resulted from strong interaction between palygorskite surface and the intercalated TC molecules. Figure. FTIR spectra of palygorskite after equilibrated with TC at an initial concentration of 800 mg/L at different pH in the range of 1250–1750 cm–1.

Conclusions 1. Sorption of TC on palygorskite followed a pseudo-second-order kinetics. Sorption equilibrium could be reached in 2 h. 2. Sorption of TC on palygorskite followed a Langmuir sorption isotherm with the sorption maximum reached to 99mg/g, or 210 mmol/kg at pH 8.7. 3. Solution pH and ionic strength had strong effects on TC uptake by palygorskite. 4. Sorption of TC on palygorskite is an endothermic reaction, and thus, increasing temperature will enhance the uptake of TC by palygorskite. The moderate negative G indicates that physisorption or surface complexation may be the dominant mechanism. The small positive S suggests that the sorbed TC molecules adopted a random arrangement on palygorskite surfaces. 5. XRD analyses showed no d-spacing changes at different pH values or different sorption amounts, further suggesting that the sorption is on the external surfaces.