Xinqing Chen

Precious metal recovery by selective adsorption using biosorbents.

Silk sericin and chitosan biosorbents are low cost and highly efficient biosorbents derived from waste biomass. Both biosorbents displayed good capacity and excellent selectivity for gold adsorption. Silk sericin and chitosan adsorbed respectively 1 and 3.3mmolg(-1) of gold and have K(d) values of 450 and 34,000, respectively. Experimental evidence showed that gold adsorbed on the amide groups of the silk sericin, while gold and copper adsorbed on the amino groups of chitosan via charge-interactions and complexation. Binary (Au-Cu), five (Au-Co-Ni-Cu-Zn) and six (Au-Pd-Co-Ni-Cu-Zn) component separations consistently showed that silk sericin has better selectivity (Sel(Au)>2.4) than chitosan. It is possible to recover gold at 99.5% purity by silk sericin and 90% if the solution contained palladium.

Distinguished Cr(VI) capture with rapid and superior capability using polydopamine microsphere: Behavior and mechanism

Toxic heavy metal containing Cr(VI) species is a serious threat for ecological environment and human beings. In this work, a new mussel-inspired polydopamine microsphere (PDA-sphere) is prepared through in situ oxidative polymerization at air condition with controllable sizes. The adsorption of Cr(VI) ions onto PDA-sphere is highly pH dependent with the optimal pH ranging from 2.5 to 3.8. A rapid Cr(VI) removal can approach in 8min for equilibrium. More importantly, the prepared materials exhibit a remarkable sorption selectivity, coexisting SO42-, NO3- and Cl- ions at high levels; The applicability model further proves its effective performances with treated capacity of 42,000kg/kg sorbent, and the effluent can be reduced from 2000ppb to below 50ppb, which meets the drinking water criterions recommended by WHO. 1kg sorbent can also purify approximately 100t Cr(VI) contaminated wastewaters basing on the wastewater discharges of China. Such capacity for application ranks the top level for Cr(VI) removal. Additionally, the exhausted materials can be well regenerated by binary alkaline and salts mixtures. Such efficient adsorption can be ascribed to the well-dispersed morphology as well as the strong affinity between Cr(VI) and catechol or amine groups by XPS investigation. All the results suggest that polydopamine microspheres may be ideal materials for Cr(VI) treatment in waters.

Fast capture of methyl-dyes over hierarchical amino-Co0.3Ni0.7Fe2O4@SiO2 nanofibrous membranes

Flexible polydopamine–Co0.3Ni0.7Fe2O4@SiO2 NFMs with a hierarchical structure and strong magnetism were prepared by gelation, calcination and dopamine self-polymerization on electrospun SiO2 NFMs. The resulting membranes displayed a short response time (10 min/80%), high adsorption capacity and excellent adsorption affinity (97%) for methyl orange capture.

Direct manipulation of particle size and morphology of ordered mesoporous silica by flow synthesis

The precision by which the fluid mixing, flow pattern, and reaction can be manipulated in a flow-synthesis reactor enables the deliberate preparation of ordered mesoporous silicas (OMS) of controlled particle size (ca. 50 to 650 nm) and shapes (i.e., spheres and random), as well as complex microstructures (i.e., hollow spheres). Fluid mixing and flow pattern were generated using Tee- and slit interdigital micromixers under laminar and Taylor flow conditions, while hydrolysis reactions was governed by the alkoxide precursors (i.e. TEOS & TMOS) and temperature. The hollow OMS spheres can host molecules and clusters as demonstrated by the incorporation of ferrocene and iron nanoparticles.

Coke suppression in MTO over hierarchical SAPO-34 zeolites

Hierarchical SAPO-34 crystals were synthesized by a facile TEAOH etching post-treatment for the first time. Owing to the diffusion intensification and unchanged catalytic activity, the single-run lifetime of the resultant zeolites was significantly prolonged in the MTO process from 320 to 640 min without sacrificing the excellent methanol conversion and C2–4 selectivity.

Assessment of Sericin Biosorbent for Selective Dye Removal

Abstract The silk sericin is the main residue in silk production and it is found to be a low cost and efficient biosorbent. In this study, sericin was characterized with various techniques including SEM (scanning electron microscope), XRD, N 2 physisorption, FTIR (Fourier transformed infrared spectroscopy) and XPS (X-ray photoelectron spectroscopy). The nitrogen content of sericin was ca. 8.5 mmol·g −1 according to elemental analysis. Dye adsorption by sericin biosorbent was investigated with the acid yellow (AY), methylene blue (MB) and copper (II) phthalocyanine-3,4′4″4‴-tetrasulfonic acid (CuPc) dyes from water. Sericin displayed large capacity for AY and CuPc adsorption with adsorption capacities of respectively 3.1 and 0.35 mmol·g −1 , but it did not adsorbed methylene blue dye. This selectivity is due to the basicity of amide groups in sericin biosorbents.

Facile one-pot solvent-free synthesis of hierarchical ZSM-5 for methanol to gasoline conversion

A hierarchical ZSM-5 zeolite with high crystallinity, high surface area, adjustable Si/Al ratio and suitable acidic properties was synthesized by a one-pot solvent-free method. The resultant zeolite exhibited complete methanol conversion, high C5+ selectivity (>60%) and a long lifetime (350 h) in the MTG process.

Accelerated Sorption Diffusion for Cu(II) Retention by Anchorage of Nano-zirconium Dioxide onto Highly charged Polystyrene Material.

The development of nanocomposite with strong adsorption ability exhibits great potential applications for environmental remediation. However, the pore blocking in preparation frequently constrains sorption diffusion, resulting in low utilization efficiency. Here we synthesized a new nano-ZrO2/Polystyrene (NZO-PS) material tailored with a specific fixed SO3-Na group to enhance Cu(II) removal. The NZO-PS exhibits efficient Cu(II) sequestration in a wide pH range (3.0–6.5) and preferential sorption performances. The efficient kinetic behavior and column applicability suggest the blocked pore channel is not a matter when presence of negatively charged moiety, which accelerates Cu(II) sorption diffusion and enrichment toward target active site. Moreover, the exhausted NZO-PS can be readily regenerated through HCl-NaCl binary solution. The preparation route can be extended to synthesize other functional composited materials. Simultaneously, the characteristics of simplicity, high-yield and regeneration provide some promising industrial merits.

Enhanced MTO performance over acid treated hierarchical SAPO-34

Abstract Hierarchical SAPO-34 crystals were synthesized by a facile acid etching post-treatment. Butterfly-shaped porous patterns on four side faces and hierarchical pores composed of micropores, mesopores and macropores were formed after a nitric acid or oxalic acid treatment. The catalytic performance of the hierarchical SAPO-34 for the methanol to olefins (MTO) process showed that the synergistic effect of the hierarchical pores and acid sites resulted in a longer catalyst lifetime (from 210 to 390 min for the acid treated SAPO-34) and higher selectivity to light olefins of 92%–94%. The ethylene selectivity can be adjusted between 37.4% and 51.5% by the pore size. No hierarchical SAPO-34 was obtained after a treatment with butanedioic acid, and with this sample, fast deactivation was detected after 100 min.

Chromium-based metal–organic framework/mesoporous carbon composite: synthesis, characterization and CO2 adsorption

New composites of a water-stable chromium-based metal organic framework MIL-101 and mesoporous carbon CMK-3 were in situ synthesized with different ratios of MIL-101 and CMK-3 using the hydrothermal method. The composites as well as the parent materials were characterized by X-ray diffraction, thermo gravimetric analysis, scanning electron microscope, transmission electron microscope and nitrogen/carbon dioxide adsorption isotherms. The hybrid material possesses the same crystal structure and morphology as its parent MIL-101, and exhibits an enhancement in CO2 adsorption uptakes when compared to MIL-101 and CMK-3. The increase in CO2 uptakes was attributed to the combined effect of the formation of additional micropores, the enhancement of micropore volume and the activation of unsaturated metal sites by CMK-3 incorporation.