Cellulose-based colorimetric sensor with N, S sites for Ag+ detection.

A novel cellulose-based colorimetric sensor (DAC-Tu) with N, S sites for Ag+ was prepared. The DAC-Tu exhibited excellent selectivity and sensitivity for Ag+ with a naked eyes color change from white to black in mixed metal ions aqueous solutions. The naked-eye in-situ detection limit of DAC-Tu for Ag+ was 10-6 mol/L within 10 min. The cellulose matrix and the grafted functional groups (CS, NH2) of DAC-Tu all contributed to the low naked-eye in-situ detection limit. The mechanism of the visual recognition of DAC-Tu sensor for Ag+ was proposed, the N and S atoms of DAC-Tu preferentially coordination chelated with Ag+ to form NAg, SAg, and Ag2S, and enriched on the cellulose matrix, thus the DAC-Tu presented different color change in response to different concentrations of Ag+. The as-prepared DAC-Tu colorimetric sensor showed a great application prospect for in-situ naked eyes detection of Ag+.

Multiple active sites cellulose-based adsorbent for the removal of low-level Cu(II), Pb(II) and Cr(VI) via multiple cooperative mechanisms.

A novel multiple active sites cellulose-based adsorbent (MCC/TEPAA-BCTTC) with a high density of multiple active adsorption sites (N, O, S) was prepared by using epichlorohydrin cross-linking microcrystalline cellulose (MCC) with tetraethylenepentamine (TEPA), followed by grafting with bis(carboxymethyl) trithiocarbonate (BCTTC). It was shown that the removal rates of MCC/TEPAA-BCTTC for Pb(II) (1 mg/L), Cu(II) (3 mg/L) and Cr(VI) (1 mg/L) reached 100 %, 98 % and 99 %, respectively, and the remaining concentration after adsorption reached the United States Environmental Protection Agency (US EPA) standards for Pb(II) and Cu(II) and the China integrated wastewater discharge standard for Cr(VI). These results indicate that the high removal rate of MCC/TEPAA-BCTTC for removing anionic and cationic heavy metal ions in low-concentration mixed heavy metal ions environments was mainly due to the high density of multiple adsorption sites that act via multiple cooperative mechanisms.

Structural design of a high sensitivity biomass cellulose-based colorimetric sensor and its in situ visual recognition mechanism for Cu2.

A novel biomass cellulose-based colorimetric sensor (DAC-PDH) was prepared by a Schiff base reaction between the aldehyde groups of dialdehyde cellulose (DAC) and the amino groups of 2,6-pyridine dihydrazide (PDH). The as-prepared sensor (DAC-PDH) showed selective recognition of Cu2+ and a visual colour change from white to green. The visual limit of detection for Cu2+ was 10-7 mol/L. Furthermore, DAC-PDH responded to Cu2+ within 30 s by the method of dynamic condition. The sensor possessed the properties of a high density of functional groups (CO, NH, NH2), a large external surface area, a short transit distance and flexibility; thus, Cu2+ can be rapidly absorbed and enriched on the DAC-PDH through multi-dentate ligand chelation between Cu2+ and the carbonyl groups (CO) and the amino groups (NH, NH2) of DAC-PDH. The as-prepared DAC-PDH colorimetric sensor exhibits promising prospects for in situ identification of Cu2+.

Preparation and properties of pH-responsive reversible-wettability biomass cellulose-based material for controllable oil/water separation.

Two novel pH-responsive reversible-wettability biomass cellulose-based materials of cellulose-g-PAA and cellulose-g-PAM were conveniently prepared by grafting acrylic acid (AA) and acrylamide (AM), respectively, onto eucalyptus pulp cellulose. The hydrophobic-oleophilic of cellulose-g-PAA and the oleophobic-hydrophilic of cellulose-g-PAM were converted to oleophobic-hydrophilic and hydrophobic-oleophilic, respectively, as the pH converted from 1 to 9. The pH-responsive mechanism of these cellulose-based materials was investigated by 13C nuclear magnetic resonance, X-ray photoelectron spectroscopy, and atomic force microscopy analyses. The resulting cellulose-g-PAA and cellulose-g-PAM papers were applied in the switchable separation of oil/water mixtures. Water passed through the cellulose-g-PAA paper at pH = 9 and cellulose-g-PAM paper at pH = 1, while oil was retained. After changing the pH value, oil permeated these papers, but water did not. The papers exhibited excellent regeneration performances; the oil adsorbed on the papers was completely desorbed via pH control.