Supporting Information

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1 Supporting Information One-pot Synthesis and Combined Use of Modified Cotton dsorbent and Flocculant for Purifying Dyeing Wastewater Chunli Song 1#, Junhong Zhao 1#, Hongyan Li 1, Lina Liu 1, Xuan Li 1, Xing Huang 1, Hailin Liu 1, Yikai Yu 1,2 * [1] College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang , China [2] Key Laboratory of Chemical Biology of Jiangxi Province, Nanchang, , China # Co-first authors: Chunli Song and Junhong Zhao * Corresponding author: Yikai Yu, yuyikai1980@163.com The supporting information includes 15 pages, 12 Figures, and 4 Tables. UV-Vis analysis and C curves of selected dyes UV-Vis spectral analysis was carried out to confirm the maximum absorption wavelength of the dyes using the U-3310 spectra. The maximum absorption wavelength of Reactive Scarlet 3BS was 588 nm [Figure S1()]. This meant the corresponding absorption wavelengths of Reactive Black M and Reactive Blue KNR could also be obtained, which were 589 nm and 590 nm, respectively. Subsequently, the absorbance concentration ( C) curves of Reactive Scarlet 3BS [Figure S1(B)], Reactive Black M [Figure S1(C)], and Reactive Blue KNR [Figure S1(D)] were established according to the relationship between the concentration and the absorbance of the dye aqueous solution based on the maximum absorption wavelengths. S1

2 bsorbance a y= x B nm C (mg/l) y= x C =0.011C R= D C(mg/L) C( mg/l) Figure S1. UV-Vis spectra of Reactive Scarlet 3BS (). C curves of Reactive Scarlet 3BS (B), Reactive Black M (C), and Reactive Blue KNR (D). FT- IR analysis of LP-cotton The Fourier Transform-Infrared Spectroscopy (FT-IR) spectra of the obtained LP-cotton samples in KBr pellets were recorded using a Nicolet FT-IR (510 P) spectrophotometer (Figure S2). The FT-IR spectra of the untreated cotton showed the absorption of cellulose, with peaks relating to the absorption of the OH group at 3349 cm 1, of the CH linkage at 2901 cm 1, of the CH 2 group at 1435 cm 1, and of the C O C group at 1029 cm 1, 1053 cm 1, 1108 cm 1, and 1160 cm 1. systematic comparison of the FT-IR spectra from untreated cotton, G-cotton, and selected LP-cotton showed that the absorption strengths of the C O C linkages at 1029 cm 1, 1053 cm 1, 1108 cm 1, and 1160 cm 1 were the same, indicating that the cellulose-skeletons of the modified cottons (G-cotton and LP-cotton) were not destroyed. These absorption peaks (Peak 1) could thus be considered as the reference absorption peaks for investigating the relative quantitative analysis of S2

3 the IR results between the modified cottons and untreated cotton. For the same reference absorption peaks, the absorption of the OH groups at 3349 cm 1 (Peak 4) for G-cotton and LP-cotton were both lower than of untreated cotton, suggesting that some OH groups were substituted by cationic units. Moreover, the absorption strengths of the CH 2 linkages at 1435 cm 1 and 2850 cm 1 (Peaks 2-3) of LP-cotton were higher than those of untreated cotton and G-cotton, possibly due to the long-chain alkylation polycationic film that formed on the cotton surface and increased the absorption strengths of the IR spectrum. Figure S2. FT-IR analysis of untreated cotton (), G-cotton (B), and LP-cotton (C). Key peaks that are mentioned in the text are labeled 1 4. Solid-state 13 C NMR and 1 H NMR analysis of LP-cotton The solid-state 13 C nuclear magnetic resonance (NMR) and 1 H NMR spectra of the LP-cottons (which were sheared into solid powers) were recorded on a Bruker DRX-500 (500 MHz) instrument, with the following measurement parameters: P/N Console: H03128T21430; Shim system: BOSS II; Original dataset: 8996_0011sc131; Probe: 4 mm MS BB119F/1H H8996/0011; Spinng rate: 12 khz; CCEPT-System: VWBIII600. S3

4 B Figure S3. Solid-state 13 C NMR analysis of untreated cotton () and LP-cotton (B). The solid-state 13 C NMR spectra of untreated cotton [Figure S3()] showed the six carbon characteristic peaks of the D-glucose unit of cotton cellulose at ppm, ppm, ppm, ppm, ppm, and ppm, respectively. Compared to the 13 C NMR spectra of untreated cotton, the 13 C NMR spectra of LP-cotton [Figure S3(B)] showed the six untreated cotton peaks and a new characteristic peak for the cationic unit at ppm, indicating that the new cationic structures formed on the cotton surface. B Figure S4. Solid-state 1 H NMR analysis of untreated cotton (), and LP-cotton (B). Key peaks that are mentioned in the text are labeled New Peak 1 3. The solid-state 1 H NMR spectra of untreated cotton [Figure S4()] showed the hydrogen characteristic peaks of the D-glucose unit of cotton cellulose at 2.08 ppm and 5.13 ppm, respectively. Compared to the 1 H NMR spectrum of untreated cotton, the 1 H NMR spectrum of LP-cotton [Figure S4 (B)] also showed the new characteristic peaks of the cationic unit at 1.44 ppm S4

5 (New Peak 1), 3.82 ppm (New Peak 2), and 6.43 ppm (New Peak 3). Moreover, the characteristic peak at 2.08 ppm was strengthened, while the characteristic peak at 5.13 ppm was weakened. These new and altered characteristic peaks further implied a structural change of the cotton surface that was caused by the cationic modification. SEM analysis of LP-cotton Scanning Electron Microscopy (SEM) analysis of the obtained LP-cotton was carried out with a JSM-5610 SEM instrument (Figure S5). Untreated cotton presented a smooth surface, while the surface of the selected G-cotton was rougher due to the grafting derivative of the cotton surface. However, the surface of the selected LP-cottons became very smooth again and was obviously covered with a film, indicating that the long-chain alkylation polycationic film was successfully formed and coated the cotton surface. Figure S5. SEM analysis of untreated cotton (), G-cotton (B), and LP-cotton (C). FT-IR analysis of PTDMC The FT-IR spectra of the PTDMC samples in KBr pellets were recorded using a Nicolet FT-IR (510 P) spectrophotometer (Figure S6). Compared to the FT-IR spectrum of the TDMC monomer (curve a in Figure S6), the FT-IR spectrum of PTDMC (curve b in Figure S6) showed that the bending vibration absorptions of =CH 2 at 887 and 955 cm 1 (Peaks 1 and 2) were both absent, and that the absorption of the linkage of C=C at 1641 cm 1 (Peak 6) was weakened, all of which indicated that TDMC monomers could be effectively polymerized into PTDMC. Moreover, several characteristic absorptions of the TDMC monomers at 1015 cm 1 (Peak 3), S5

6 1091 cm 1 (Peak 4), 1305 cm 1 (Peak 5), 1932 cm 1 (Peak 7), and 2128 cm 1 (Peak 8) were also absent, and the characteristic absorption of TDMC at 3028 cm 1 was further shifted to 3039 cm 1 (Peak 9). These changed absorptions indirectly implied a structural change of the TDMC monomer caused by the polymerization. Thus, the structure of the obtained PTDMC was as expected. Figure S6. FT-IR analysis of TDMC monomer (a) and PTDMC (b), with key peaks mentioned in the text labeled H NMR analysis of PTDMC The liquid 1 H NMR spectrum of PTDMC was recorded on a Bruker DRX-500 (500 MHz) instrument, based on the following measurement parameters: solvent: D 2 O; PROBHD: 5 mm PBBO BB-; PULPROG: zg 30; TD: 65536; NS: 16; DS: 2; SWH: Hz; FIDRES: Hz; Q: s; RG: 7.12; DW: usec; DE: 6.50 usec. The 1 H NMR spectrum of TDMC [Figure S7()] had the characteristic peaks of a CH 2 =CH linkage at ppm, a N CH 2 linkage at ppm, a N CH 3 group at ppm, a CH 2 linkage in the tetradecyl group at ppm, and CH 3 group in the tetradecyl unit at 0.84 ppm. The 1 H NMR spectrum of PTDMC [Figure S7(B)] had the characteristic peaks of a N + CH 2 linkage at 3.86 ppm, a N CH 3 group at ppm, a methyne unit at ppm, the CH 2 linkage at ppm in main chain and tetradecyl unit, and the CH 3 group in tetradecyl unit at 0.78 ppm. Compared to the 1 H NMR spectrum of TDMC [Figure S7()], the characteristic peak of the S6

7 CH 2 =CH linkage at ppm was almost absent, further indicating that the expected homo-polymerization of the TDMC monomer occurred to form the PTDMC. B Figure S7. 1 H NMR analysis of the TDMC monomer () and PTDMC (B) Comparing the adsorption capacities and isotherms of LP-cotton to several typical adsorbents ccording to the basic process in the section experimental: adsorption capacity and isotherms of LP-cotton, the equilibrium adsorption ( ) of LP-cotton and the equilibrium dye concentration in the solution ( ) could be obtained. Considering the variable function nature of adsorption isotherm equation, we selected the adsorption data at the adsorption stage when the adsorption results varied between the different dosages (dosages of LP-cotton = g), to fit the Langmuir and Freundlich equations. The adsorption isotherm of LP-cotton [Fig. S8 ()] was not a typical single molecular layer adsorption process, which could be confirmed by the fact that the equilibrium data did not well fit the Langmuir model [Fig. S8 (B] and Freundlich model [Fig. S8 (C)], and the correlation coefficients (R) were respectively 0.49 and The correlation coefficient of fitting the Langmuir model was so low that it was meaningless to obtain the bsed on the Langmuir model in this case. Thus, we turned to calculate the of the LP-cotton based on the average values of the saturated adsorption states at the dosages being g. Here of the LP-cotton was S7

8 mg g 1. We further selected the adsorption results of several typical and similar adsorbents under the equal test conditions (the adsorbed anionic dyes and other test conditions were the same in this work) that were employed in our previous work 1 to compare the adsorption superiority of LP-cotton (Table S1). Under the same test conditions, the adsorption capacity of the widely used activated carbon was 1.9 mg g 1 and those of untreated cotton, G-cotton, and PF-cotton were 0.2 mg g 1, 24.3 mg g 1, and 37.1 mg g 1, respectively. This meant that the adsorption capacity of LP-cotton (polycationic cotton with long-chain tetradecyl groups) was 57.5 times higher than that of activated carbon and 531.7, 4.4, and 2.9 times higher than those of the untreated cotton, G-cotton, and PF-cotton (polycationic cotton without any long-chain alkyl groups), respectively B q e (mg/g) /q e (g/mg) y= x R= C e (mg/l) /C e (L/mg) C D logq e y= x R=0.18 Zeta potential/mv logc e Dosage/g Figure S8. () dsorption isotherm of HP-cotton. (B) Fitting Langmuir model with adsorption data. (C) Fitting Freundlich model with adsorption data. (D) Zeta potential analysis of LP-cotton adsorption. S8

9 Table S1. Comparison of the adsorption capacities of LP-cotton to several typical adsorbents under the same test conditions. dsorbent dsorbate (mg g 1 ) Reference ctivated carbon Reactive Scarlet 3BS 1.9 [1] Untreated cotton Reactive Scarlet 3BS 0.2 [1] G-cotton Reactive Scarlet 3BS 24.3 [1] PF-cotton Reactive Scarlet 3BS 37.1 [1] LP-cotton Reactive Scarlet 3BS This work Test conditions of the adsorption capacities: Under magnetic stirring, with g of the adsorbent added to 10 ml of 100 mg L 1 of Reactive Scarlet 3BS dye solution at 30 to absorb the anionic dye in water for 100 h. The zeta potentials of LP-cotton adsorption under the adsorption conditions in Figure 1 were analyzed using a Zetasizer nano zs90 potential measuring instrument [Figure S8(D)]. The zeta potential gradually increased from 31.2 to mv as the LP-cotton dosage was increased from g to 0.1 g. Compared to the adsorption results shown in Figure 1, the satisfactory dye removal percentages of % could be obtained for a wide range of zeta potentials ( 25.8 to mv, with the LP-cotton dosages being g, respectively, and corresponding to the adsorption results in Figure 1), indicating that the zeta potential had little effect on the adsorption capacity of LP-cotton. Comparing the adsorption kinetics constants of LP-cotton to several typical adsorbents S9

10 log(q e -q t ) y= x R= k 1 = t/q t (min g/mg) B y= x R= k 2 = t/min t/min C D q t (mg/g) y= x R= k i = x i = ln(1-q t /q e ) y= x R= k p = t 1/2 (min 1/2 ) t/min Figure S9. () Fitting pseudo-first kinetic model with adsorption data. (B) Fitting pseudo-second kinetic model with adsorption data. (C) Fitting the intra-particle diffusion model with adsorption data. (D) Fitting the particle diffusion model with adsorption data. The results in Figure 2 show that, at a dosage of 0.05 g, it takes only 4 min for the LP-cotton product to adsorb 94.5% of the selected dyes in water, making the dye solution very clear and showing the rapidity of dye removal in water. Moreover, considering the variable nature of the adsorption kinetics equation, the adsorption equilibrium data at the stage when the adsorption results varied for different adsorption times (adsorption time = 1 4 min) were selected to fit the kinetics equation. The results showed that all of these data followed pseudo-first kinetic, pseudo-second kinetic, intra-particle diffusion, and particle diffusion models with very strong correlation coefficients ( ) of > 0.96 [Figures S9( D)]. Comparison of the corresponding kinetic parameters to those of PF-cotton and G-cotton in our S10

11 previous work 1 (Table S2) highlight that the adsorption rate constants corresponding to pseudo-first kinetic ( = min 1 ), pseudo-second kinetic ( = g mg 1 min 1 ), and particle diffusion models ( = min 1 ) of LP-cotton were far lower than those of both PF-cotton and G-cotton, suggesting that the electrostatic combination rates between the cationic groups of LP-cotton and anionic dyes were decreased by blocking the long-chain alkyl groups. However, the adsorption rate constant ( = 9.60 mg g 1 min 1/2 ) for the intra-particle diffusion model of LP-cotton was 2.85 and 2.46 times higher than those of PF-cotton ( = 3.37 mg g 1 min 1/2 ) and G-cotton ( = 3.91 mg g 1 min 1/2 ), respectively, indicating that the dye diffusion rate inside the LP-cotton was far higher than that of PF-cotton or G-cotton, possibly because the long-chain tetradecyl groups prevented the adsorbed internal dyes from being desorbed by water outside the LP-cotton. Table S2. Comparison of the adsorption kinetics constants of LP-cotton to several similar adsorbents. dsorbent dsorbate (min 1 ) (g mg 1 min 1 ) (min 1 ) (mg g 1 min 1/2 ) Reference G-cotton Reactive Scarlet 3BS [1] PF-cotton Reactive Scarlet 3BS [1] LP-cotton Reactive Scarlet 3BS This work Comparing the adsorption thermodynamics constants of LP-cotton to several typical adsorbents ccording to the basic process described in the section experimental: adsorption thermodynamics of LP-cotton, all the data obtained were substituted into the thermodynamic model, and the adsorption thermodynamics of LP-cotton were compared to those of PF-cotton reported in our previous contribution. 1 The results are shown in Figure S10. S11

12 lnk c y= x R= H m = kj/mol S m = kj/mol /T(K -1 ) Figure S10. The analysis on the adsorption thermodynamics of LP-cotton Figure S10 showed that the obtained data of the adsorption thermodynamics of LP-cotton fitted the thermodynamic model well, with a high correlation coefficient (R = 0.96). The molar adsorption enthalpy ( H m ) of LP-cotton was kj/mol. The absolute values of molar enthalpy were near to the 20 kj mol 1 of the range of chemical adsorption energy. 2 It indicated that LP-cotton could produce a certain electrostatic interaction with the anionic dyes but this electrostatic interaction strength was relatively weak. However, when compared to the similar PF-cotton, the LP-cotton s absolute value of the molar adsorption enthalpy was further lower for LP-cotton (the values of the molar adsorption enthalpy of PF-cotton was kj/mol), while its molar entropy ( S m = kj mol -1 K -1 ) was obviously higher (the values of the molar entropy of PF-cotton was kj mol -1 K -1 ) (Table S3). It could be deduced that the electrostatic combination force and tendency between the internal cationic groups of LP-cotton and anionic dyes would be reduced, possibly because the steric hindrance of the long-chain tetradecyl groups on the cotton surface, thus weakening the electrostatic combination of LP-cottons and anionic dyes. Table S3. Comparison of the adsorption thermodynamics constants of LP-cotton to similar PF-cotton adsorbent. S12

13 dsorbent dsorbate m (kj mol 1 ) m (kj mol 1 K 1 ) Reference PF-cotton Reactive Scarlet 3BS [1] LP-cotton Reactive Scarlet 3BS This work Comparing the flocculation results of PTDMC to several similar flocculants The optimal dosages of PTDMC ( mg L 1 ) were higher than those of PDMDC (40 mg L 1 ) and HC-PDMDC (18 mg L 1 ), reported in our previous contribution. 3 However, compared to some traditional flocculants in this work, including polyaluminum chloride (PC) and poly ferric sulfate (PFS), the optimal dosages of PTDMC were below those of PC (150 mg L 1 ) and PFS (180 mg L 1 ), indicating that the PTDMC flocculant maintained a medium dosage level. More importantly, PTDMC had a better adaptability, removing > 97.0% of all the selected anionic dyes (Reactive Scarlet 3BS, Reactive Blue KNR, and Reactive Black M), while PDMDC, PC, and PFS failed to achieve an effective purification effect in removing both Reactive Blue KNR and Reactive Black M, and HC-PDMDC failed to achieve an effective purification effect in removing Reactive Blue KNR (Table S4). Table S4. Comparing the flocculation results of PTDMC to several similar flocculants. Flocculant Dosage (mg L 1 ) Removed Dye Dye removal (%) Reference 40 Reactive Scarlet 3BS 88.5 [3] PDMDC No optimal dosage Reactive Black M No effective purification effect [3] No optimal dosage Reactive Blue KNR No effective purification effect [3] HC- PDMDC 18 Reactive Scarlet 3BS 98.1 [3] 30 Reactive Black M 92.4 [3] No optimal dosage Reactive Blue KNR No effective purification effect [3] 150 Reactive Scarlet 3BS 91.5 Traditional flocculant PC No optimal dosage Reactive Black M No effective purification effect Traditional flocculant S13

14 No optimal dosage Reactive Blue KNR No effective purification effect Traditional flocculant 180 Reactive Scarlet 3BS 90.7 Traditional flocculant PFS No optimal dosage Reactive Black M No effective purification effect Traditional flocculant No optimal dosage Reactive Blue KNR No effective purification effect Traditional flocculant 140 Reactive Scarlet 3BS 97.0 This work PTDMC 140 Reactive Black M 99.1 This work 70 Reactive Blue KNR 98.4 This work Zeta potential and FT-IR analysis of the formed flocs The zeta potential of the flocs derived from the interaction between PTDMC and Reactive Scarlet 3BS was analyzed using a Zetasizer nano zs90 potential measuring instrument [Figure S11()]. The zeta potential gradually increased from 31.7 to mv as the PTDMC dosage increased from 130 to 190 mg L 1. Compared to the flocculation results shown in Figure 4(), the satisfactory dye removal percentages of % could be obtained within a suitable range of zeta potentials, 16.2 to mv (corresponding to PTDMC dosages of mg L 1 ), while the flocculation results for zeta potentials greater than mv or less than 16.2 mv were both worse. The reason for this phenomenon could be explained as follows. s the PTDMC dosage increased, the anionic groups of the dyes were gradually combined with the cationic groups of PTDMC, and the decrease in the negative charges of the dyes caused a decrease in their water solubility, thus allowing them to form flocs. However, when the PTDMC dosage was excessive, the excess PTDMC cations attached to the floc surface, increasing the resolubility of the flocs in water, resulting in a worse flocculation result. FT-IR analysis of flocs derived from the interaction between PTDMC and Reactive Scarlet 3BS was analyzed using a Nicolet FT-IR (510 P) spectrophotometer, with the results shown in Figure 11(B). The FT-IR spectra of the flocs exhibited absorption of the CH 3 groups at 2968 cm 1, of the CH 2 linkage at 2926 cm 1, and of the methyne linkage at 2853 cm 1, which were similar to those of PTDMC, indicating that structures of the flocs consisted of both PTDMC (Peak 1), which exhibited absorption at cm 1, and dyes (Reactive Scarlet 3BS; Peak 4). Conversely, S14

15 after forming flocs, the dye absorption at 1558 cm 1 (Peak 2) was shifted to 1568 cm 1 (Peak 3), and the dye adsorption strength at cm 1 (Peak 4) changed markedly, which could be attributed to the flocculation interactions between the PTDMC and dye (Reactive Scarlet 3BS). Therefore, we could further confirm that PTDMC produced flocculation interactions with the anionic dyes to form flocs, thus effectively removing the anionic dyes in water B Zeta petential/m V Dosage(mg/L) Figure S11. () Zeta potential and (B) FT-IR analysis of flocculation precipitations derived from the interaction between PTDMC and Reactive Scarlet 3BS. The three curves in (B) are for PTDMC (a), the flocculation precipitation (b), and Reactive Scarlet 3BS (c). Key peaks that are mentioned in the text are labeled 1 4. FT-IR analysis of combined interaction of LP-cotton and PTDMC The LP-cotton, after being combined with the flocs, was further analyzed by FT-IR analysis (Figure S12). The results showed that the absorption at cm 1 was similar to that of pure LP-cotton (Peak 1), indicating that the structure of LP-cotton was maintained under the combined use of LP-cotton and PTDMC. Moreover, this FT-IR spectrum also detected the absorption of PTDMC (which was included in the floc of PTDMC and anionic dye) at 2853 cm 1 and 2926 cm 1 (Peak 2), further confirming that the associations occurred between LP-cotton and the formed flocs. S15

16 Figure S12. FT-IR analysis of combined use of pure LP-cotton (a), flocs of PTDMC and Reactive Scarlet 3BS (b), and the LP-cotton after being interacted with the flocs (c). Key regions that are discussed in the text are labeled 1 and 2. References 1. Jia, Q.; Song, C.; Li, H.; Huang, Y.; Liu, L.; and Yu, Y. Construction of Polycationic Film Coated Cotton and New Inductive Effect to Remove Water-soluble Dyes in Water. Materials and Design 2017, 124, Zhou Y. The study on the biosorption of acid and basic dye from aqueous solution using entermorpha prolifera, a green marine macroalga. Master Dissertation, Ocean University of China, Qingdao, CN, Jia, Q.; Song, C.; Li, H.; Zhang, Z.; Liu, H.; Yu, Y.; and Wang, T. Synthesis of Strongly Cationic Hydrophobic Polyquaternuim Flocculants for Enhancement in Removal of Water-soluble Dyes in Waste-water. Research on Chemical Intermediates 2017, 43, S16