Jian Rong

Synthesis and characterization of porous fibers/polyurethane foam composites for selective removal of oils and organic solvents from water

In the field of oil/water separation, functional oil-absorbing materials with both controllable porous structures and swelling properties are highly desirable. In the present study, we report a novel strategy for fabricating Mg–Al porous fiber (Mg–Al PF)/polyurethane (PU) foam composites using a combined biotemplate method and foaming technology, and discuss their application in the absorption of oils and organic solvents. The Mg–Al PF composites with a hierarchical porous structure are fabricated based on nanoplatelets on the surfaces of microscale inorganic fibers. The PU foam composites with excellent oil swelling properties are synthesized by addition of Mg–Al PF composites to PU foams. In order to enhance the hydrophobic and oleophilic properties, the surfaces of Mg–Al PF composites are chemically modified using silane coupling agent (KH 570). The surface modified Mg–Al PF composites show high repellency towards water with a water contact angle of 146.6°. Owing to their unique pore structures and superhydrophobic and swelling properties, the foam composites can remove oils and organic solvents from water with high selectivity and absorption capacity, and can absorb not only floating oil but also heavy organic solvents underwater. In general, the absorption capacities of the PU foam composites for oils and organic solvents are 5.06–44.81 times their own weight, partly depending on the density and viscosity of the absorbate. The PU foam composites still maintain relatively consistent absorption properties for oil and organic solvent absorption after 10 cycles. These outstanding properties potentially make the as-prepared PU foam composites promising candidates for practical oil absorption and oil/water separation.

Enhanced adsorption of fluoride from aqueous solutions by hierarchically structured Mg-Al LDHs/Al2O3 composites

Hierarchically structured layered double hydroxides (LDHs)/Al2O3 composites were fabricated from waste paper fibers using a two-step method. In the first step microscaled Al2O3 fibers were prepared by template-directed synthesis employing waste paper fibers as templates; and in the second step nanoscaled LDHs platelets were fabricated into hierarchical architectures based on crystal growth on Al2O3 fibers surface. The morphology and structure of asprepared samples were characterized by scanning electron microscopy (SEM), N2 adsorption/desorption analysis and X-ray diffraction (XRD) analysis. The SEM results revealed that the inorganic fibers were covered by LDHs platelets, forming the hierarchical structures with micro- to nanoscales. The BET analysis showed that the surface area was increased from 76.66m2/g (Al2O3 fibers) to 165.0m2/g (composites) by the growth of LDHs platelets on the surfaces of Al2O3 fibers. As compared to bare LDHs particles and Al2O3 fibers, the LDHs/Al2O3 composites show a high fluoride adsorption capacity, and the maximum adsorption capacity can reach up to 58.7mg/g. The Langmuir isotherm model was found to agree well with the equilibrium data, while the pseudo-second order model provided the highest correlation of the kinetic data for fluoride adsorption. The as-prepared LDHs/Al2O3 composites and corresponding design strategies developed herein are expected to be applicable to the synthesis of other LDHs based composites for the removal of pollutants from water.

Structural evolution of hierarchical porous NiO/Al2O3 composites and their application for removal of dyes by adsorption

Hierarchical porous NiO/Al2O3 composites were successfully prepared by two-steps. First, the core-shell structured Al2O3 microspheres were prepared via a template-free hydrothermal route using KAl(SO4)2·12H2O and Al2(SO4)3·18H2O as aluminum source. Then, the NiO/Al2O3 composites with micro- and nano-hierarchical structures were prepared by a hydrothermal method combining the subsequent calcination process. The obtained characterization result presented that the morphology of hierarchical Al2O3 microsphere tuned to irregular platelets by simply varying Ni/Al ratios. The BET analysis showed that the special surface area from 52.12m2 g−1 to 214.8m2 g−1 after two hydrothermal complex process. Effects of Ni/Al ratio, adsorbent dosage, Congo red (CR) concentration, coexisting ions, adsorption time and temperature were investigated. The obtained results indicated that NiO/Al2O3 composite had the high adsorption efficiency (99.6%) and great adsorption capacity (186.9mg g−1) under the optimum conditions. The adsorption isotherm and kinetics data were found to be well fitted and in good agreement with the Langmuir isotherm model and pseudo-second order model, respectively. The hierarchical porous NiO/Al2O3 composites presented remarkably higher adsorption efficiency during five recycling, which showed their potential as the highly efficient adsorbent for removal of CR in wastewater.

Controlled and facile synthesis of a self-assembled enzyme–inorganic catalyst based on flexible metal-coated fiber for an excellent removal of synthetic pollutants from aqueous environment

The development of green sustainable chemistry opens the door to the application of biocatalytic in numerous fields for the research in industry and academia. As a common biological catalyst, enzyme catalysis is ideally suited and widely applicable for various desired reaction. In this work, a hierarchical structure laccase–Cu3(PO4)2·3H2O nanoflower-coated silica fiber (La–CNSF) was successfully fabricated with hundreds of Cu3(PO4)2 nanosheets formed on the processed silica fibers as the petal and laccase as the enzyme catalyst. It included two processes: first, Cu nanoparticles were directly grown on silica fiber cloth as a precursor and three-dimensional (3D) Cu3(PO4)2·3H2O nanoflower was self-assembled on Cu-coated fibers by post-processing. Then, La–CNSF was successfully immobilized via a simple one-step immersion reaction in a laccase-phosphate buffer solution (PBS) solution. The product was characterized by FTIR, XRD, SEM and UV–visible spectroscopy. Congo red was realized using La–CNSF as a biocatalyst. Compared with pure laccase, La–CNSF sample exhibits an enhanced catalytic activity. The flower-like structure assembled on the fiber provided La–CNSF high storage stability and reusability in contrast with free laccase. The superior catalytic performance of La–CNSF supports a potential strategy for purification of water pollutants, and it favors the realization of the engineering of large scale applications of enzyme catalysis.