Sapana Kumari

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.

A new guar gum-based adsorbent for the removal of Hg(II) from its aqueous solutions

Modification of biopolymers by oxidation is an easy process to develop effective adsorbents for the removal of toxic metal ions from their aqueous solutions. In the present study, guar gum (GG) was crosslinked with epichlorohydrin and then oxidized to the polydialdehyde form (GG-clPDA). The latter was converted to a Schiff-base, GG-clCHN(CH2)6NCHGG, by reaction with hexamethylenediamine. Different forms of the modified GG were characterized by SEM, FTIR and XRD and investigated as adsorbents for the removal of Hg(II) ions from their aqueous solutions. The adsorption process was carried out through the variation of time, temperature, pH and initial concentration of Hg(II) ions. GG-clCHN(CH2)6NCHGG was observed to be an efficient adsorbent with a maximum adsorption capacity of 41.13 mg/g. It is reusable up to five cycles at the optimum conditions obtained for the maximum ions uptake. The kinetic data generated fit the Freundlich isotherm and pseudo-second order kinetics.

A green and highly efficient sulfur functionalization of starch

In this study, sulfur functionalized starch has been successfully prepared, via an iso-thiouronium salt intermediate, from the reaction of thiourea with chloroacetylated starch. The later was synthesized by a chloroacetylation reaction. Thiolation via an iso-thiouronium ion intermediate is an innovative green approach to achieve thiol functionalization of starch with an innocuous low cost thiourea reagent. The thiol products are amenable for further derivatization and were modified to a sulfide and a sulphonium salt. The sulphonium structure was accomplished by exhaustive alkylation with iodoethane as an alkylating agent, which resulted in permanent charge generation on the starch backbone. The above-mentioned reactions were also carried out using microwave heating to achieve maximum yet uniform modification of starch. The extent of the derivatization processes was confirmed by iodine titration and precipitation titration and also by characterization of the synthesized samples by FTIR spectroscopy, 1H-NMR, 13C-NMR, SEM-EDX, XRD, zeta potential measurements and elemental analysis (CHNS) to confirm the reaction output at every synthetic stage. Evidence that the degree of substitution of the thiol groups was ≥ 2 was obtained from titrimetry, SEM-EDX and elemental (CHNS) characterization results. Additionally, the generation of the permanent charge on the sulphonium structure was confirmed using zeta potential measurements.

New lignin-based polyurethane foam for wastewater treatment

Utilization of renewable feedstock for the development of alternative materials is rapidly increasing due to the depletion of petroleum resources and related environmental issues. Lignin, the second major constituent of lignocellulosic biomass, is catching the attention of researchers for the synthesis of various value-added materials due to its renewable and biodegradable nature, large abundance, non-food value and high functionality. In the present work, lignin was extracted from pine needles, a considerable bio-waste material, and was used as the polyol for the synthesis of polyurethane foam (PUF). The synthesized lignin-PUF (LPUF) was characterized for its physical and thermal properties, and employed as an adsorbent of dyes. The results demonstrated that LPUF is an efficient material to remove a cationic dye, malachite green, and was better in comparison to an anionic dye, methyl orange, from their aqueous solutions. Dye adsorption was a spontaneous and endothermic process. The adsorption kinetics and isotherms fitted well the pseudo second-order model and Langmuir adsorption isotherm, respectively, with a maximum adsorption capacity of 80 mg g−1. In addition, LPUF was reusable for a number of repeat cycles with a cumulative adsorption capacity of 1.33 g g−1 after twenty regeneration cycles.

Bio-waste derived dialdehyde cellulose ethers as supports for α-chymotrypsin immobilization

Enzyme immobilization is an important technique to enhance stability, storability and reusability of enzymes. In the present work, pine needles, a forest bio-waste, were used as a feedstock of cellulose to synthesize new materials as supports for immobilization of α-chymotrypsin (CT) enzyme. The extracted cellulose from pine needles was etherified with different alkyl bromides (RBr) and etherified products were further modified to dialdehyde via oxidation with NaIO4 to get the desired products, dialdehyde cellulose ethers (ROcellCHO). CT was then covalently immobilized onto as-synthesized dialdehyde cellulose ethers via Schiff-base formation, i.e., imine linkage. The synthesized products and enzyme immobilization were confirmed by different characterization techniques and the activity assay of the free and the immobilized CT was carried out using standard protocol with variation of different parameters such as temperature, pH and substrate concentration. The storage stability and reusability of the immobilized CT were also investigated. CT activity was also studied in simulated physiological conditions in the artificial gastric fluid and artificial intestinal fluid. Artificial neural network (ANN) model was employed to correlate the relationship with% relative activity and time, temperature and pH affecting enzyme activity. A good correlation of experimental data was predicted by ANN model.