Supporting Information Clay Based Nanocomposites as Recyclable Adsorbent toward Hg(II) Capture: Experimental and Theoretical Understanding Sankar Das, Arnab Samanta, Gautam Gangopadhyay and Subhra Jana * Department of Chemical, Biological & Macro-Molecular Sciences, S. N. Bose National Centre for Basic Sciences, Block - JD, Sector-III, Salt Lake, Kolkata -700 106, India. Technical Research Centre, S. N. Bose National Centre for Basic Sciences, Block - JD, Sector- III, Salt Lake, Kolkata -700 106, India. E-mail: subhra.jana@bose.res.in S1
Materials All chemicals were used as received without any further purification. Halloysite nanotubes (HNTs), trimethoxy[3-(methylamino)propyl]silane and Copper(ll) chloride were purchased from Sigma-Aldrich. (3-aminopropyl) triethoxysilane was obtained from Alfa Aesar. Mercuric acetate, lead nitrate, cadmium acetate, sodium chloride, and sodium hydroxide were received from Sisco Research Laboratory (SRL), India. Toluene, ethanol, and hydrochloric acid were procured from Merck, India. S2
Figure S1. 29 Si CP-MAS NMR spectrum of S-HNTs. The new peak at -67 ppm demonstrates the formation of a chemical bond between the surface hydroxyl groups of HNTs and the organosilanes. S3
Figure S2. XRD patterns of HNTs, P-HNTs and S-HNTs respectively, indicating the absence of any intercalation of aminosilanes into the interlayer of HNTs. S4
A B Figure S3. The nitrogen adsorption-desorption isotherms of (A) P-HNTs and (B) S-HNTs respectively, representing the signature of mesoporous materials. The specific surface area was estimated using nitrogen adsorption-desorption study at 77 K. S5
Figure S4. FTIR spectra of P-HNTs and S-HNTs after adsorption of Hg(II) ions, indicating metal-ligand complex formation between Hg(II) and the reactive functional groups (-NH 2 or - NHR) present in the adsorbents, since the lone pair of electrons on the nitrogen are the key adsorption sites for Hg(II) capture. S6
Table S1. Comparison of Hg(II) Uptake Efficiency of P-HNTs with the Reported Amine Based Adsorbents. Adsorbents Conc. of Hg(II) (mg L -1 ) Adsorption Capacity (mg g -1 ) References P-C-CTS-(Hg) 50 12.5 1 MWCNT-AA 50 45.05 2 GO 100 16.7 3 MGO 100 59.9 3 Bent-NH 2 100 39.0 4 NM 1 150 68.8 5 MIL-101-200 51.75 6 Thymine MIL-101-NH 2 200 30.67 6 P-HNTs 200 52.18 This work References: 1. Tang, X.; Niu, D.; Bi, C.; Shen, B. Hg 2+ Adsorption from a Low-Concentration Aqueous Solution on Chitosan Beads Modified by Combining Polyamination With Hg 2+ -Imprinted Technologies. Ind. Eng. Chem. Res. 2013, 52, 13120-13127. 2. Deb, A. S.; Dwivedi, V.; Dasgupta, K.; Ali, S. M.; Shenoy, K. T.; Novel Amidoamine Functionalized Multi-Walled Carbon Nanotubes for Removal of Mercury (II) Ions from Wastewater: Combined Experimental and Density Functional Theoretical Approach. Chem. Eng. J. 2017, 313, 899-911. 3. Guo, Y.; Deng, J.; Zhu, J.; Zhou, X.; Bai, R. Removal of Mercury (II) and Methylene Blue from a Wastewater Environment with Magnetic Graphene Oxide: Adsorption Kinetics, Isotherms and Mechanism. RSC Adv. 2016, 6, 82523-82536. 4. Anirudhan, T. S.; Jalajamony, S.; Sreekumari, S. S. Adsorption of Heavy Metal Ions from Aqueous Solutions by Amine and Carboxylate Functionalised Bentonites. Appl Clay Sci. 2012, 65, 67-71. 5. Zhu, Z.; Yang, X.; He, L. N.; Li, W. Adsorption of Hg 2+ from Aqueous Solution on Functionalized MCM-41. RSC Adv. 2012, 2, 1088 1095. 6. Luo, X.; Shen, T.; Ding, L.; Zhong, W.; Luo, J.; Luo, S.; Novel Thymine-Functionalized MIL- 101 Prepared by Post-Synthesis and Enhanced Removal of Hg 2+ from Water. J. Hazard. Mater. 2016, 306, 313-322. S7