Hongxiang Zhu

The removal of heavy metal ions from aqueous solutions by amine functionalized cellulose pretreated with microwave-H2O2

A new biosorbent (PEI/SA-MCCMV) with abundant amino and carboxyl groups was prepared by grafting polyethylenimine (PEI) onto carboxylated microcrystalline cellulose (SA-MCCMV), which was obtained through grafting succinic anhydride (SA) on pretreated microcrystalline cellulose (MCCMV) with microwave-H2O2. It was confirmed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron microscopy (XPS) and thermogravimetric (TG) that the amino and carboxyl groups were introduced onto the microcrystalline cellulose, and the amino and carboxyl groups content were 2.61 mmol g−1 and 4.64 mmol g−1, respectively. The effects of the contact time and pH on heavy metal ion uptake were investigated. The adsorption kinetic data was described well with the pseudo-second-order model (R2 > 0.99) and the adsorption isotherms were well fitted by the Freundlich isotherm model, demonstrating that chemisorption was the rate-controlling factor for heavy metal ion adsorption on the PEI/SA-MCCMV biosorbent. Furthermore, the remarkable adsorption capacity (217.3 and 357.1 mg g−1 for Cd(II) and Pb(II), respectively) obtained from the Langmuir isotherm indicated that this biomass adsorbent has a promising application in water treatment.

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.

Thermo-Responsive Cellulose-Based Material with Switchable Wettability for Controllable Oil/Water Separation

A thermo-responsive cellulose-based material (cellulose-g-PNIPAAm) was prepared by grafting N-isopropylacrylamide (NIPAAm) onto bagasse pulp cellulose via Ce (IV)-initiated free radical polymerization. The surfaces of the obtained cellulose-g-PNIPAAm paper showed a rapid wettability conversion from being hydrophilic (water contact angles (WCA) of 0°) at 25 °C to becoming hydrophobic (WCA of 134.2°) at 45 °C. Furthermore, the thermo-responsive mechanism of cellulose-g-PNIPAAm was examined by the in situ variable-temperature 13C NMR, 1H NMR and AFM analysis. At the same time, the resulting cellulose paper was applied for a switchable separation of oil/water mixtures. Water can pass through the paper under 45 °C, while oil is kept on the paper. When the temperature is above 45 °C, oil can permeate through the paper, while water cannot pass through the water. Moreover, the paper exhibited excellent regeneration performance after five cycles and maintained its switchable wettability.