Jinshui Yao

Adsorption–reduction of chromium(VI) from aqueous solution by phenol–formaldehyde resin microspheres

A novel adsorbent of phenol–formaldehyde resin (PF) microspheres was prepared at a low temperature, and had an excellent performance for the adsorption–reduction of Cr(VI). The microspheres were characterized by transmission electron microscope (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS). The effects of contact time, pH value and initial concentration, adsorbent dosage and temperature were studied by batch mode. The results showed that the adsorption process fitted a pseudo-second-order model and a Langmuir isotherm model very well, and an intra-particle diffusion model gave three stages in the whole process. Thermodynamic constant values (ΔH° > 0, ΔS° > 0, ΔG° < 0) indicated that the adsorption process was endothermic and spontaneous. The maximum adsorption capacity of Cr(VI) on the adsorbent reached 280.9 mg g−1 at 303 K. The PF microspheres could be applied to Cr(VI)–water treatment with the reduction and adsorption of the heavy metal ion.

PolyPEGylation of Protein using Semitelechelic and Mid-functional Poly(PEGMA)s synthesized by RAFT polymerization

A series of well defined semitelechelic and mid-functionalized poly(poly(ethylene glycol) methyl ether methacrylate)s (poly(PEGMA)s) were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization using thiazolidine-2-thione-functionalized chain transfer agents (CTAs). The thiazolidine-2-thione group was located either at the end or in the middle of polymer chains depending on the different structural CTAs. All polymers were fully analyzed by 1H NMR spectroscopy and GPC, confirming their well-defined structures, such as predesigned molecular weights, narrow polydispersity indices, and high yield chain-end or chain-middle functionalization. The thiazolidine-2-thione functionality located at the end of or at the middle of the polymer chains can react with amine residues on protein surfaces, forming protein-polymer conjugates via amide linkages. The bioactivity of protein conjugates were subsequently tested using micrococcus lysodeikticus cell as substitute. The protein conjugations from the mid-functionalized polymer remained much more protein bioactivity comparing to their semitelechelic counterpart with similar molecular weights, indicating the steric hindrance of the mid-functionalized poly(PEGMA)s lead to the better selective conjugation to protein. The number of polymer chains on the protein surface was additionally evaluated by TNBS analysis, exhibiting that there are less mid-functionalized poly(PEGMA)s linked on the protein surface than the semitelechelic polymers, also supporting the hypothesis that the steric hindrance from branch-structural polymers results in the better reaction selectivity. This synthetic methodology is suitable for universal proteins, seeking a balance between the protein bioactivity and the protein protection by the covalent linkage with polymer, and exhibits promising potential for pharmaceutical protein conjugation.

New optically active poly(amide-imide)s based on N,N′-(pyromellitoyl)-bis-L-amino acid and methylene diphenyl-4,4′-diisocyanate: synthesis and characterization

Five new optically active poly(amide-imide)s were synthesized through the direct polycondensation reaction between chiral N,N′-(pyromellitoyl)-bis-L-amino acids and methylene diphenyl-4,4′-diisocyanate in a medium consisting of N-methyl-2-pyrrolidone (NMP) and xylene. The resulted polymers were fully characterized by means of Fourier transform infrared spectroscopy, elemental analyses, and solubility tests. Thermal properties of these polymers were investigated by using thermal gravimetric analysis/SDTA. All of the polymers were soluble at room temperature in polar solvents such as N,N′-dimethyl acetamide, N,N′-dimethyl formamide, dimethyl sulfoxide (DMSO), NMP, sulfuric acid, and para-methyl phenol. Same specific rotations of these polymers in these different solvents were obtained.

Synthesis and biodegradation studies of optically active poly(amide–imide)s based on N,N′-(pyromellitoyl)-bis-l-amino acid

Five new optically active poly(amide–imide)s (PAIs) (PAI3a–PAI3e) were synthesized through the direct polycondensation reaction between chiral N,N′-(pyromellitoyl)-bis-l-amino acids and 4,4′-diaminodiphenyl ether. The resulted polymers were fully characterized by means of Fourier transform infrared (FTIR) and proton nuclear magnetic resonance spectroscopy, elemental analysis, inherent viscosity measurement, solubility tests, specific rotation, and thermogravimetric analysis (TGA). The biodegradation studies of the PAIs were performed in soil and in phosphate buffer solution. The surface morphology and hydrophobicity of the biodegraded PAI films were investigated. FTIR spectra showed structural changes on PAI powders being treated in phosphate buffer solution. The TGA data showed that the thermal stability of PAI powders decreased with the degradation time. The collected degradation products were soluble in water and had absorption in ultraviolet and visible light region. Possible biodegradation mechanism of amino acid-based PAIs was explored.

Green synthesis of tannin-hexamethylendiamine based adsorbents for efficient removal of Cr(VI)

Newly developed adsorbents, poly(tannin-hexamethylendiamine) (PTHA), were fabricated by varying the mole ratio of tannin (TA) and hexamethylendiamine (HA) under one-pot reaction. The specific forming process of the adsorbent which had undergone the transition from hydrogen bonds to covalent bonds was subsequently explored. Based on the efficiency of Cr(VI) removal from aqueous solution over all prepared adsorbents, the PTHA-4 (mole ratio of TA/HAu202f=u202f1:12.5) exhibited an excellent adsorption behavior. Adsorption experiments affected by contact time and ionic strength have been conducted successively by PTHA-4, and the equilibrium was reached at 24u202fh. The kinetic data revealed that the adsorption was good agreement with pseudo-second order model and needed to undergo the rate-controlling step. The maximum adsorption capacity was 283.29u202fmg/g at 30u202f°C, relying on the isothermal curve suitably described by Langmuir model. Furthermore, toxic Cr(VI) had been reduced to the low toxic Cr(III) during adsorption process. The structures and adsorption performance of adsorbent were confirmed by means of SEM, FT-IR, XPS etc. Thus, the cheap-sustainable adsorbents have a superior feature for Cr(VI)-wastewater purification in future.

Removal of hexavalent chromium from aqueous solution using novel dye-based adsorbent prepared by flocculation

ABSTRACT In this paper, the dye sludge which was prepared from Congo red solution by flocculation method was further modified by catechol and 1, 6-hexanediamine before usage to remove Cr(VI) ions. This particles were characterized by multiple testing means and the effects of removal, such as contact time, pH value, initial concentration, and temperature, were studied by batch mode. The maximum adsorption capacity of Cr(VI) was 282.48 mg/g and the whole process was spontaneous and endothermic. Hopefully, with the advantages of facile preparation and high adsorption capacity, the dye-based adsorbent has broad application prospects in the field of wastewater treatment.

Highly Sensitive Detection of Melamine Based on the Fluorescence Resonance Energy Transfer between Conjugated Polymer Nanoparticles and Gold Nanoparticles

Adding melamine as additives in food products will lead to many diseases and even death. However, the present techniques of melamine detection require time-consuming steps, complicated procedures and expensive analytical apparatus. The fluorescent assay method was facile and highly sensitive. In this work, a fluorescence resonance energy transfer (FRET) system for melamine detection was constructed based on conjugated polymer nanoparticles (CPNs) and gold nanoparticles (AuNPs). The energy transfer efficiency is up to 82.1%, and the system is highly selective and sensitive to melamine detection with a lower detection limit of 1.7 nmol/L. Moreover, the interaction mechanism was explored. The results showed that the fluorescence of CPNs were firstly quenched by AuNPs, and then restored after adding melamine because of reducing FRET between CPNs and AuNPs. Lastly, the proposed method was carried out for melamine detection in powdered infant formula with satisfactory results.

Silane-based hyper-cross-linked porous polymers and their applications in gas storage and water treatment

A series of novel silane-based hyper-cross-linked porous polymers was prepared through the Friedel–Crafts alkylation reaction of dimethyldiphenylsilane as the monomer and formaldehyde dimethyl acetal as the external cross-linker. The structures of the polymers were confirmed by FTIR and solid-state cross-polarization magic-angle spinning 13C NMR. We investigated the porous polymers with different ratios of dimethyldiphenylsilane to formaldehyde dimethyl acetal. Porous properties were determined by nitrogen, carbon dioxide and hydrogen adsorptions. The results revealed that the porous materials possessed surface areas from 742 to 1205xa0m2xa0g−1 with the increasing amount of formaldehyde dimethyl acetal. Moreover, this material exhibited high thermal stabilities, good CO2 capture, and H2 storage capacities. The material was also used as adsorbent for organic dyes in aqueous solution and showed an excellent adsorption capacity of 952xa0mgxa0g−1 for Congo red dye. These results suggest that the silane-based hyper-cross-linked porous polymers are promising materials for CO2 capture, H2 storage, and water treatment.

Facile Synthesis of New Optically Active Unsaturated Amides Monomers Based on S-(+)-α-Phenyl Ethylamine

Three new optically active unsaturated amides monomers which could be polymerized were synthesized through the direct condensation between S-(+)-α-phenyl ethylamine and prop-2-enoyl chloride, 2-methyl-prop-2-enoyl chloride and undec-10-enoyl chloride, respectively. The resulted unsaturated amides were proven by means of 1H-NMR spectroscopy, FT-IR spectroscopy, elemental analyses and specific rotations. The polymerization of one of synthesized monomers, N-(1S-1-phenylethyl)-undec-10-enamide, is reported for the first time.