A novel method for the disassembly of synthetic hydrogels in situ and thereby enhanced adsorption of crystal violet dye is reported. Silicon present in the husk ashes of Panicum miliare is used as the trigger for disassembly of poly(2-acrylamido-1-propane sulfonic acid-co-itaconic acid) hydrogels. Disassembling ability of the ash was determined by changing the temperature of the husk ash. Surface area and particle sizes of both the disassembled and assembled forms of the hydrogels were determined by E. Suito’s method. Removal of crystal violet dye from aqueous solution and the respective adsorption capacities of disassembled and assembled forms of hydrogels were compared by varying parameters such as pH, temperature, and agitation speed. Concentration of the dye in aqueous solution was determined by using UV-Visible spectrophotometer. FTIR analysis was carried out for the characterization of the hydrogels, ash blended hydrogels, and the free ashes. SEM imaging was carried out to differentiate the surfaces of the assembled and disassembled hydrogels. 1. Introduction Many researches are being done on hydrogels to increase and improve their applications in various fields. Cross-linked hydrophilic polymers made hydrogels have capacity for expanding their volumes by their high capacity for water absorption [1, 2] that makes them suitable for purification of wastewater, drug delivery [3], and so forth. The use of hydrogels is known since the late 1950s in the form of the bioengineered contact-lenses [4]. Recently hydrogels such as poloxamers are useful in regenerative medicine. The adsorption ability of aromatic organic molecules of the polymer hydrogels [5] has provided a very good option for polymer adsorbents. Like few other hydrogels poly(2-acrylamido-1-propane sulfonic acid-co-itaconic acid) [poly(AMPS-co-IA)] hydrogels are reported to be good adsorbents for the removal of methylene blue dye [6] and few metal ions [7, 8] from aqueous solution. Crystal violet has been largely used in numerous commercial textile processes as a dye and also in human and veterinary medicines as a biological stain [9, 10]. When discharged into the aquatic system, it can cause severe environmental degradation. The dye has a blue-violet colour with an extinction coefficient of 87,000？M？1？cm？1 and an absorbance maximum at 590？nm when dissolved in water [11]. Crystal violet has been classified as a recalcitrant. That makes it difficult for the metabolism of living microbes and hence the dye has extended lifetime in various environments [12]. Crystal violet is highly toxic,
References
[1]
M. A. Barakat, “New trends in removing heavy metals from industrial wastewater,” Arabian Journal of Chemistry, vol. 4, no. 4, pp. 361–377, 2011.
[2]
J. A. Zimberlin, N. Sanabria-Delong, G. N. Tew, and A. J. Crosby, “Cavitation rheology for soft materials,” Soft Matter, vol. 3, no. 6, pp. 763–767, 2007.
[3]
A. S. Hoffmann, “Hydrogels for biomedical applications,” Advanced Drug Delivery Reviews, vol. 54, no. 1, pp. 3–12, 2002.
[4]
N. A. Peppas, Y. Huang, M. Torres-Lugo, J. H. Ward, and J. Zhang, “Physicochemical foundations and structural design of hydrogels in medicine and biology,” Annual Review of Biomedical Engineering, vol. 2, pp. 9–29, 2000.
[5]
X. Y. Hu and Y. B. Chen, “Adsorption properties of chemical crosslinked polymer gel,” Advanced Materials Research, vol. 87-88, pp. 22–26, 2009.
[6]
R. Coskun, “Removal of cationic dye from aqueous solution by adsorption onto crosslinked poly(4-vinylpyridine/crotonic acid) and its N-oxide derivative,” Polymer Bulletin, vol. 67, no. 1, pp. 125–140, 2011.
[7]
S. ？avu？ and G. Gürda？, “Noncompetitive removal of heavy metal ions from aqueous solutions by poly[2-(acrylamido)-2-methyl-1-propanesulfonic acid-co-itaconic acid] hydrogel,” Industrial and Engineering Chemistry Research, vol. 48, no. 5, pp. 2652–2658, 2009.
[8]
S. ？avu？ and G. Gürda？, “Competitive heavy metal removal by poly(2-acrylamido-2-methyl-1-propane sulfonic acid-co-itaconic acid),” Polymers for Advanced Technologies, vol. 19, no. 9, pp. 1209–1217, 2008.
[9]
J. A. Bumpus and B. J. Brock, “Biodegradation of crystal violet by the white rot fungus Phanerochaete chrysosporium,” Applied and Environmental Microbiology, vol. 54, no. 5, pp. 1143–1150, 1988.
[10]
Y. I. Yang, D. W. Jung, D. G. Bai, G. S. Yoo, and J. K. Choi, “Counterion-dye staining method for DNA in agarose gels using crystal violet and methyl orange,” Electrophoresis, vol. 22, no. 5, pp. 855–859, 2001.
[11]
E. Q. Adams and L. Rosenstein, “The color and ionization of crystal-violet,” Journal of the American Chemical Society, vol. 36, pp. 1452–1473, 1914.
[12]
C. C. Chen, H. J. Liao, C. Y. Cheng, C. Y. Yen, and Y. C. Chung, “Biodegradation of crystal violet by Pseudomonas putida,” Biotechnology Letters, vol. 29, no. 3, pp. 391–396, 2007.
[13]
W. Au, S. Pathak, C. J. Collie, and T. C. Hsu, “Cytogenetic toxicity of gentian violet and crystal violet on mammalian cells in vitro,” Mutation Research, vol. 58, no. 2-3, pp. 269–276, 1978.
[14]
R. Usha, “Little millet (Panicum miliare l.)—a source of functional food for sustainable nutrition security,” in Proceedings of the 7th Asia Pacific Conference on Clinical Nutrition, Bangkok, Thailand, June 2011.
[15]
A. Bozkurt, O. Ekinci, and W. H. Meyer, “Synthesis and characterization of proton-conducting copolymers on the basis of vinylpyrrolidone and acrylamido sulfonic acid,” Journal of Applied Polymer Science, vol. 90, no. 12, pp. 3347–3353, 2003.
[16]
F. Rosa, J. Bordado, and M. Casquilho, “Hydrosoluble copolymers of acrylamide-(2-acrylamido-2-methylpropanesulfonic acid). Synthesis and characterization by spectroscopy and viscometry,” Journal of Applied Polymer Science, vol. 87, no. 2, pp. 192–198, 2003.
[17]
J. Travas-Sejdic and A. Easteal, “Study of free-radical copolymerization of acrylamide with 2-acrylamido-2-methyl-1-propane sulphonic acid,” Journal of Applied Polymer Science, vol. 75, no. 5, pp. 619–628, 2000.
[18]
B. L. Rivas, S. A. Pooley, M. Luna, and K. E. Geckeler, “Synthesis of water-soluble polymers containing sulfonic acid and amine moieties for the recovery of metal ions using ultrafiltration,” Journal of Applied Polymer Science, vol. 82, no. 1, pp. 22–30, 2001.
[19]
O. G. Marambio, G. D. C. Pizarro, M. Jeria-Orell, M. Huerta, C. Olea-Azar, and W. D. Habicher, “Poly(N-phenylmaleimide-co-acrylic acid)-copper(II) and poly(N-phenylmaleimide-co-acrylic acid)-cobalt(II) complexes: synthesis, characterization, and thermal behavior,” Journal of Polymer Science A: Polymer Chemistry, vol. 43, no. 20, pp. 4933–4941, 2005.
[20]
K. F. Arndt, A. Richter, S. Ludwig et al., “Poly(vinyl alcohol)/poly(acrylic acid) hydrogels: FT-IR spectroscopic characterization of crosslinking reaction and work at transition point,” Acta Polymerica, vol. 50, no. 11-12, pp. 383–390, 1999.
[21]
M. R. Alexander, S. Payan, and T. M. Duc, “Interfacial interactions of plasma-polymerized acrylic acid and an oxidized aluminium surface investigated using XPS, FTIR and Poly(acrylic acid) as a model compound,” Surface and Interface Analysis, vol. 26, no. 13, pp. 961–973, 1998.
[22]
J. Dong, Y. Ozaki, and K. Nakashima, “FTIR studies of conformational energies of poly (acrylic acid) in cast films,” Journal of Polymer Science B: Polymer Physics, vol. 35, no. 3, pp. 507–515, 1997.
[23]
J. G. Noh, Y. J. Sung, K. E. Geckeler, and S. E. Kudaibergenov, “Synthesis, characterization, and stimuli-sensitive properties of novel polycarbobetaines,” Polymer, vol. 46, no. 7, pp. 2183–2190, 2005.
[24]
J. D. S. Candido, R. C. F. Leit？o, N. M. P. S. Ricardo, J. P. A. Feitosa, E. C. Muniz, and F. H. A. Rodrigues, “Hydrogels composite of poly(acrylamide-co-acrylate) and rice husk ash. I. Synthesis and characterization,” Journal of Applied Polymer Science, vol. 123, no. 2, pp. 879–887, 2012.
[25]
E. Suito, M. Arakawa, and T. Arakawa, “Surface area measurement of powders by adsorption in liquid phase—calculation of specific surface area of calcium carbonate powders from the adsorption of stearic acid,” Journal of Chemical Society of Japan, vol. 75, pp. 596–599, 1954.
[26]
L. Zhang, F. Rakotondradany, A. J. Myles, H. Fenniri, and T. J. Webster, “Arginine-glycine-aspartic acid modified rosette nanotube-hydrogel composites for bone tissue engineering,” Biomaterials, vol. 30, no. 7, pp. 1309–1320, 2009.
[27]
A. Groza, A. Surmeian, M. Ganciu, and I. I. Popescu, “Infrared spectral investigation of organosilicon compounds under corona charge injection in air at atmospheric pressure,” Journal of Optoelectronics and Advanced Materials, vol. 7, no. 5, pp. 2545–2548, 2005.
[28]
L. J. Bellamy, The Infrared Spectra of Complex Molecules, vol. 1, John Wiley & Sons, New York, NY, USA, 3rd edition, 1975.
[29]
Q. Xing, Modeling mechanisms of water affinity and condensation on Si-based surfaces via experiments and applications [Ph.D. thesis], Arizona State University, 2011.
[30]
O. Kulygin and M. S. Silverstein, “Porous poly(2-hydroxyethyl methacrylate) hydrogels synthesized within high internal phase emulsions,” Soft Matter, vol. 3, no. 12, pp. 1525–1529, 2007.
[31]
M. V. Flores-Merino, S. Chirasatitsin, C. Lopresti, G. C. Reilly, G. Battaglia, and A. J. Engler, “Nanoscopic mechanical anisotropy in hydrogel surfaces,” Soft Matter, vol. 6, no. 18, pp. 4466–4470, 2010.
[32]
M. A. Azagarsamy, P. Sokkalingam, and S. Thayumanavan, “Enzyme-triggered disassembly of dendrimer-based amphiphilic nanocontainers,” Journal of the American Chemical Society, vol. 131, no. 40, pp. 14184–14185, 2009.
