03568nas a2200217 4500008004100000022001400041245008800055210006900143260009900212300001000311490000700321520275900328653001303087653002503100653002403125653002303149653001503172100002103187700002303208856011903231 2008 eng d a0144-861700aComplexation of heavy metals by crosslinked chitin and its deacetylated derivatives0 aComplexation of heavy metals by crosslinked chitin and its deace aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcJAN a66-730 v713 a

Chitin was crosslinked using diisocyanatohexane (HDI), trimellitic anhydride (TMA), and dibromodecane (DBD), then deacetylated in strong aqueous alkali. This led to a product with amine functional groups on the exposed surface of the crosslinked chitin, which could be utilized for complexation with heavy metals. Thus, a key feature of the crosslinked derivatives prepared was that only the hydroxy Groups were utilized in the crosslinking reaction, and the acetylamino groups of chitin were hydrolyzed only after the crosslinking was accomplished. This ensured that all amino groups of the chitosans so produced would be available for metal complexation, and not partially used up in crosslinking. This proposed advantage was proved by the similar binding observed for heavy metals like Hg (348-372 mg/g), Cu (91-119 mg/g), Zn (71-92 mg/g), Mn (3-10 mg/g), Cd (121-160 mg/g), and Pb (32-86 mg/g) using these crosslinked polymers, whereas the control polymer (uncrosslinked chitosan powder) had complexation values for Hg (348-361 mg/g), Cu (100-106 mg/g), Zn (81-92 mg/g), Mn (4-7 mg/g), Cd (135 mg/g), and Pb (25-59 mg/g). Additionally, in a case where chitosan was crosslinked with HDI. the amino groups were consumed in the crosslinking reaction, and the metal complexation capacity has found to be decreased for Cu (91-109 mg/g), Cd (133 mg/g), and Zn (71-77 mg/g), while remaining nearly the same for Hg (362 mg/g). The literature value for Cu complexation is 59.67 mg/g for chitosan crosslinked with glutaraldehyde. The crosslinked derivatives have the added advantage of insolubility even in low pH aqueous media, making their repeated re-use possible. Further, these crosslinked derivatives could be used in powder form, and the additional step of preparing beads was found to be not necessary for ease of separation of the crosslinked powder by filtration. The binding capacity of various crosslinked chitin and deacetylated derivatives for Cu, Cd, Hg, Zn, Mn. and Pb was in the region of 100, 140, 360 88, 5, and 60 mg/g (rounded off values) of polymer, respectively, very close to the values obtained for uncrosslinked chitosan. The metal binding for crosslinked chitosan was slightly lower than that of crosslinked chitin and deacetylated derivatives, due to use of some amino groups in crosslinking. For Cu ions, the Langmuir equation was found to be the best fit for HDI crosslinked deacetylated chitin and TMA crosslinked deacetylated chitin. The morphological studies conducted using WAXRD are in close agreement with the metal complexation data, showing complete loss of original chitosan peaks for the heavily complexed derivatives, and minor changes for the weakly complexed metals. (c) 2007 Elsevier Ltd. All rights reserved.

10aChitosan10aCrosslinked chitosan10adeacetylated chitin10ametal complexation10aMorphology1 aTrimukhe, K., D.1 aVarma, Anjanikumar uhttps://library.ncl.res.in/content/complexation-heavy-metals-crosslinked-chitin-and-its-deacetylated-derivatives-002102nas a2200229 4500008004100000022001400041245010400055210006900159260009900228300001200327490000700339520126100346653001301607653002501620653001801645653001501663653000801678653001001686100002101696700002301717856013201740 2008 eng d a0144-861700aMorphological study of heavy metal complexes of chitosan and crosslinked chitosans by SEM and WAXRD0 aMorphological study of heavy metal complexes of chitosan and cro aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcMAR a698-7020 v713 a

Metal complexes of salts of Hg, Cu, Cd, Pb, Zn, and Mn with chitosan and crosslinked chitosans were prepared, and their morphologies were studied using scanning electron microscopy and wide angle X-ray diffraction. The metal ions which were specifically and strongly complexed to the amino functions of chitosans, like Hg, showed smooth surface morphology inspite of large number of ions complexed (372 mg/g of chitosan). The presence of metal ions on the surface of the chitosans could be detected with decrease in metal ion binding, in the following sequence Hg > Cu > Cd > Zn > Pb > Mn. Particularly in the case of Pb ions, the presence of these ions is clearly seen on the surface of the polymer by SEM. The number of ions of Mn complexed on the polymers was too few (5 mg/g of chitosan) to be visible. SEM of Hg and Cu complexes do not show the ``holes'' observed in the crosslinked polymers as they bind specifically to amino groups of chitosan, but for Cd, Zn, Mn, and Pb complexes, these ``holes'' are clearly visible. These results are also in agreement with the morphologies studied by WAXRD. The metal complexation data for each of these metal ions was also in the same sequence. (c) 2007 Elsevier Ltd. All rights reserved.

10aChitosan10aCrosslinked chitosan10ametal complex10aMorphology10aSEM10aWAXRD1 aTrimukhe, K., D.1 aVarma, Anjanikumar uhttps://library.ncl.res.in/content/morphological-study-heavy-metal-complexes-chitosan-and-crosslinked-chitosans-sem-and-waxrd-001672nas a2200229 4500008004100000022001400041245011000055210006900165260009900234300001200333490000800345520083000353653002301183653001401206653000801220653001501228653001801243653000801261100002501269700002301294856012501317 2014 eng d a0144-861700aFunctionalized celluloses and their nanoparticles: morphology, thermal properties, and solubility studies0 aFunctionalized celluloses and their nanoparticles morphology the aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcAPR a135-1420 v1043 a

Agricultural residues derived cellulose was used to synthesize a new series of carboxy functionalized cellulosic nanoparticles (quasi-spherical shaped, 13.2-21.5% carboxyl content) and macro-sized 6-carboxycelluloses (long-fibril shaped, 1.7-22% carboxyl content). The DP (50-70) and yield (upto 46%) of nanoparticles were manipulated by controlling the reaction temperature and time. TGA/DTG thermographs of the carboxycelluloses gave thermostability data and co-related well with the residual crystalline, amorphous, and anhydroglucuronic acid content. The particle shape and size had no effect on the thermal stability. Some derivatives were fully or partially soluble in aqueous alkali and non-aqueous solvents, which can lead to increased versatility of these polymers. (C) 2014 Elsevier Ltd. All rights reserved.

10a6-Carboxycellulose10acellulose10aDTG10aMorphology10aNanoparticles10aTGA1 aSharma, Priyanka, R.1 aVarma, Anjanikumar uhttps://library.ncl.res.in/content/functionalized-celluloses-and-their-nanoparticles-morphology-thermal-properties-and-0