Cation removal using cellulose chemically modified by a Schiff base procedure applying green principles

Production of galactan phthalates derivatives extracted from Gracilaria birdie: Characterization, cytotoxic and antioxidant profile

The present work explores the esterification reaction in the polysaccharide extracted from the seaweed Gracilaria birdiae and investigates its antioxidant potential. The reaction process was conducted with phthalic anhydride at different reaction times (10, 20 and 30 min), using a molar ratio of 1:2 (polymer: phthalic anhydride). Derivatives were characterized by FTIR, TGA, DSC and XRD. The biological properties of derivatives were investigated by assays of cytotoxicity and antioxidant activity (2,2-diphenyl-1-picrylhydroxyl - DPPH and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt - ABTS). The results obtained by FT-IR confirmed the chemical modification, there was a reduction related to the presence of carbonyl and hydroxyl groups when compared to the in nature polysaccharide spectrum. TGA analysis showed a change in the thermal behavior of the modified materials. X-ray diffraction, it was shown that the in nature polysaccharide appeared as an amorphous material, while the material obtained after the chemical modification process had increased crystallinity, due to the introduction of phthalate groups. For the biological assays, it was observed that the phthalate derivative was more selective than the unmodified material for the murine metastatic melanoma tumor cell line (B16F10), revealing a good antioxidant profile for DPPH and ABTS radicals.

Photooxidation of triarylphosphines under aerobic conditions in the presence of a gold(iii) complex on cellulose extracted from Carthamus tinctorius immobilized on nanofibrous phosphosilicate

Triarylphosphines were converted to the corresponding oxides via photooxidation as a novel method.

Synthesis and characterization of poly(carboxymethyl)-cellulose for enhanced La(III) sorption

The grafting of amino and carboxylic acid groups on cellulose increased La(III) sorption efficiency of cellulose: maximum sorption capacity increased from 38mgLag^-1 for cellulose to 101 and 170mgLag^-1 for amino derivative (PAC) and amino-carboxylic derivative (PCMC). Langmuir equation successfully fits sorption isotherms while uptake kinetics are effectively modeled using the pseudo-first order rate equation (though resistance to intraparticle diffusion plays a significant role in the control of metal recovery). Uptake equilibrium occurred within 150-180min. The thermodynamic study shows that the reaction is spontaneous, endothermic and entropic. Nitric acid solutions (0.5M concentration) can be efficiently used for metal recovery and sorbent can be recycled for at least 5 cycles with limited decrease in sorption performance for the three sorbents. The materials were characterized by elemental analysis, acid-base titration, FTIR spectrometry, x-ray diffraction analysis, X-ray photoelectron spectroscopy, SEM-EDX analysis and also by TGA.

Cellulose derivatives modified by sodium tellurate and a chromium(III) tellurate complex

A novel cellulose (Cell) derivative, sodium-tellurato (Cell-TeO(OH)4(ONa)/Cell-Cl), has been synthesized from the reaction of 6-chloro-6-deoxycellulose (Cell-Cl) with telluric acid in the presence of sodium hydroxide. The subsequent reaction of this polymeric material with chromium(III) in aqueous solution yields the [Cr(Cell-TeO3(OH)3/Cell-Cl)(Cell-TeO2(OH)4/Cell-Cl)(H2O)3] complex. The molecular structures and morphology of the new polymer and the Cr(III) complex have been examined using elemental analysis, solid-state (13)C NMR, UV-vis, XRD and FTIR spectroscopy, and SEM-EDX, TGA and magnetic measurements. The results are considered to be consistent with the formulations proposed. The deprotonation constants of the modified cellulose and the stability constant of the Cr(III) complex have been determined by pH-metric measurements.

New cellulose-lysine Schiff-base-based sensor-adsorbent for mercury ions

Mercury is a highly toxic environmental pollutant; thus, there is an urgent need to develop new materials for its simultaneous detection and removal from water. In the present study, new oxidized cellulose-based materials, including their Schiff bases, were synthesized and investigated as a sensor-adsorbent for simple, rapid, highly selective, and simultaneous detection and removal of mercury [Hg(II)] ions. Cellulose was extracted from the pine needles, etherified, oxidized, and modified to Schiff base by reaction with l-lysine. The well-characterized cellulose Schiff base materials were used as a sensor-adsorbent for Hg(II) from aqueous solution. Hg(II) sensing was analysed with naked-eye detection and fluorescence spectroscopy. Schiff base having a decyl chain, C10-O-cell-HC═N-Lys, was observed to be an efficient adsorbent with a very high maximum adsorption capacity of 258.75 mg g(-1). The data were analyzed on the basis of various kinetic and isotherm models, and pseudo-second-order kinetics and Langmuir isotherm were followed for Hg(II) adsorption.

Adsorption of heavy metal ions from aqueous solution by carboxylated cellulose nanocrystals

A novel nanoadsorbent for the removal of heavy metal ions is reported. Cotton was first hydrolyzed to obtain cellulose nanocrystals (CNCs). CNCs were then chemically modified with succinic anhydride to obtain SCNCs. The sodic nanoadsorbent (NaSCNCs) was further prepared by treatment of SCNCs with saturated NaHCO3 aqueous solution. Batch experiments were carried out with SCNCs and NaSCNCs for the removal of Pb2+ and Cd2+. The effects of contact time, pH, initial adsorption concentration, coexisting ions and the regeneration performance were investigated. Kinetic studies showed that the adsorption equilibrium time of Pb2+ and Cd2+ was reached within 150 min on SCNCs and 5 min on NaSCNCs. The adsorption capacities of Pb2+ and Cd2+ on SCNCs and NaSCNCs increased with increasing pH. The adsorption isotherm was well fitted by the Langmuir model. The maximum adsorption capacities of SCNCs and NaSCNCs for Pb2+ and Cd2+ were 367.6 mg/g, 259.7 mg/g and 465.1 mg/g, 344.8 mg/g, respectively. SCNCs and NaSCNCs showed high selectivity and interference resistance from coexisting ions for the adsorption of Pb2+. NaSCNCs could be efficiently regenerated with a mild saturated NaCl solution with no loss of capacity after two recycles. The adsorption mechanisms of SCNCs and NaSCNCs were discussed.

Removal and recovery of Chrysoidine Y from aqueous solutions by waste materials

This article describes the use of bottom ash [a power plant waste] and de-oiled soya [an agricultural waste] as effective adsorbents for the removal of a hazardous azo dye [Chrysoidine Y] from its aqueous solutions. This paper presents an experimental study and discussion of the adsorption characteristics of this dye on the two adsorbents. The adsorbents have been characterized, and also the effects of time, temperature, concentration, pH, and sieve size on the extent of adsorption have been evaluated. Batch adsorption measurements, kinetic studies, and column operations have been performed to elucidate the dye uptake capacity of the adsorbents. The monolayer adsorption capacities at 30 degrees C have been found from Langmuir analysis to be 7.27x10(-5) mol g(-1) and 3.35x10(-5) mol g(-1) for bottom ash and de-oiled soya, respectively. Adsorption kinetics experimental data are indicative of pseudo-second order kinetics during these processes. Column experiments indicate practical utility of the adsorbents for eradicating hazardous dyes from effluents. The recovery of the adsorbed dye from bottom ash and de-oiled soya, have been found to be 85% and 99%, respectively.