Papers by Keyword: Chemical Modification

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Authors: Samia Benhammadi, Andrei Shishkin, Abdelkader Iddou, Hakim Aguedal, Louis Charles de Menorval
Abstract: The removal of lead from aqueous solutions was studied using the liquid-solid extraction method. The solids used are the crude phosphocalcic hydroxapatite [Ca10(PO4)6(OH)2] (HAPc), and phosphocalcic hydroxapatite treated with 5 % lactic acid solution (HAPal). The extraction results showed the influence of the initial concentration of Pb (II) and temperature of the suspensions. The maximum adsorption capacities of each material (HAPc and HAPal) were obtained with the application of Langmuir adsorption model. The most important quantity was founded as 41,84mg/g for HAPal. Isotherms established at different temperatures showed that this parameter affects greatly the adsorption of Pb (II) on both adsorbents. The best results were obtained at room temperature (25°C) compared with those recorded at 50°C.Finally, the results of this study allow us to note that the hydroxiapatite material can be as good extractant solid, for heavy metals, especially when it is modified with lactic acid.
Authors: Luizângela Reis Osório, Idglan Sá Lima, Humberto Medeiros Barreto, Josy Anteveli Osajima, Edson Cavalcanti Silva Filho
Abstract: A novel chitosan derivative was prepared through direct reaction of pure chitosan with acetylacetone in the absence of a solvent, and it was characterized by elemental analysis, Fourier transform infrared spectrometry (FTIR), and 13C Nuclear Magnetic Ressonance (NMR) spectroscopy. Moreover, the antibacterial properties of the new biomaterial were tested by the direct contact method against multi-drug resistant strains of Staphylococcus aureus and Escherichia coli. The results from the characterization were consistent with the modification of the chemical structure made. The new derivative showed a better antibacterial activity than raw chitosan against E. coli strains, indicating that incorporation of imine link (Schiff base) enhanced its antibacterial activity against Gram-negative bacterium. On the contrary, this chemical change did not decrease its antibacterial activity against Gram-positive bacterium.
Authors: Jana Daňková, Tereza Majstríková, Pavel Mec
Abstract: Water in liquid and gaseous form is the main factor which significantly affects degradation processes in the wood. The mechanism and rate of wooden degradation processes can be effectively influenced by appropriate methods and technologies for its protection. However new knowledge, based on the possibilities of application of modern physical and chemical analytical methods, confirms that most well-known and previously commonly used protective equipment damages wooden structure. Many chemical substances, which are included in preservatives such as organic and inorganic biocides, or also flame retardants, are declared to be environmentally unacceptable. Nowadays, environmentally friendly treatment technologies of wood have increased attention to the above reasons. Wooden treatment by silicones ranks among the technologies which repellent, fire resistant and corrosion effectiveness is demonstrated by many authors. This article presents results of the experimental study that deals with the mechanical properties of bonded joints in the wood treated by silicones.
Authors: Cheolmun Yim, Do Hoon Shin, Yun Hae Kim, Yasunobu Moriguchi, Riichi Murakami
Abstract: Diamond film was deposited on the pure titanium substrate by CH4-H2 gas mixture using MPCVD method. In order to carboxylate the surface of the diamond film, it was chemically treated in H2SO4:HNO3 (9:1, case 1) stirred at room temperature or in H2SO4:HNO3 (3:1, case 2) stirred at reflux. The oxidized diamond film was successively treated with 0.1M NaOH for 2hours and 0.1M HCl at 363K for 2hours, and then washed by distilled water. The surface of diamond film was observed by scanning electron microscopy (SEM). The diamond film was characterized using Raman spectroscopy and X-ray diffraction (XRD). Carboxylated diamond film was evaluated by Fourier transform infrared spectrometer (FT-IR), Mini secondary ion mass spectrometer (Mini SIMS) and X-ray photoelectron spectroscopy (XPS). In the FT-IR spectrum, the peak at 1640cm -1 was assigned with C=O stretching vibration of carboxylic acid. In the Mini SIMS profile, the peak intensities of mass number 16 (-O-) and 17 (-OH) were increased after the chemical treatment. The XPS results indicated COO- group and C=O group on the surface of diamond film.
Authors: Kentaro Egawa, Ken-ichi Minami, Yoshiyuki Sugahara
Authors: Ying Ya Yang, Dan Yu, Wei Wang
Abstract: Antibacterial polyester (PET) fibers with high electric conductivity were introduced by pretreatment-free electro-less silver plating in this study. The PET fibers were modified with the amide-siloxane film before silver coating, which was proved by the ATR-FTIR spectra, energy dispersive X-Ray (EDX) analysis and thermo-gravimetric (TG) analysis, respectively. Uniform and compact silver-coated film was found on the surface of PET fibers, evidenced by scanning electron microscopy (SEM). With 16% silver loading, the results indicted that silver-coated fibers have high electric conductivity (2.66Ω/cm) and exhibit strong antimicrobial activity against Escherichia coli (with 6.5 mm inhibition ring).
Authors: Guo Feng Wu, Qian Lang, Bin Wang, Yi Fei Jiang, Jun Wen Pu
Abstract: In this research, the chemical and multilayer hot-press drying was used to modify poplar wood. The timbers were compressed and dried in the multilayer hot-press drying kiln. The combination of chemical modification and hot-press drying can improve the mechanical properties. The influence of chemical and hot-press drying on the compressive strength parallel to grain, the bending strength, the density, the water absorbent and the crystallinity of poplar wood have been investigated in this study. The chemical treated conditions close to real technological regimes selected. The samples were impregnated with three conditions. The samples were dried in a hot-press drying kiln for 130hrs. It was showed that the urea carbamate and hot-press drying treatment increase the properties. The density and mechanical properties increased with increasing urea carbamate, while the water absorption decreased. The crystallinity is 37.03%, 37.11%, 37.78%, separately, compared with the natural wood of 35.09%. The TAG showed the thermal stability increased.
Authors: Shui Li Lai, Qiang Chai, Wu Jun Han, Bin Wang
Abstract: The synthesis of a novel chitosan (CTS) derivative bearing β-cyclodextrin (β-CD) was studied, which was divided into two steps. The first step was the preparation of carboxymethyl-β-CD, then it was acyl chlorided. The second step was that β-CD was grafted onto the CTS skeleton by the reaction of acidamide. Its adsorption property on Pb2+ was investigated. The factors that influence on the effect were discussed, including adsorption time, pH value, and temperature. The results show that its adsorption content is superior to that of the unmodified CTS. And the adsorption content (Qmax) is 246 mg.g-1 when the temperature is 35°C, pH is between 3.0~4.0 and adsorption time is 6 h.
Authors: Tae Hee Kim, In Kyu Park, Su Il Kim, Hwan Jeong Jeong, Hee Seung Bom, Chong Su Cho
Abstract: Chitosan has been considered to be a good candidate for gene delivery system, since it is already known as a biocompatible, biodegradable, and low toxic material with high cationic potential. However, low specificity and low transfection efficiency of chitosan need to be overcome prior to clinical trial. In this review paper, chemical modification of chitosan for enhancement of cell specificity and transfection efficiency was explained. Also, chemical modification of chitosan for the stability of chitosan/DNA complexes was reviewed.
Authors: Zheng Hao Fei, Wei Zhong Shi, Zhong Tang Liu, Jian Chen, Rong Xing, Yun Lan Gu, Gen Cheng Zhang
Abstract: Functional groups modified into adsorption resins were designed based on semiempirical molecular orbital theory, and the newly adsorption resin (named FZH01 modified with phthalic anhydride) having both the lower LUMO level and the higher HOMO level was prepared. The static adsorption and static desorption characteristics for gallic acid in aqueous solution onto FZH01, NDA150 and GAC at the temperature range of 288~318K were studied with bottle point method to confirm the existence of chemisorption between adsorbate and adsorbents modified, which was interpreted by the approximate orbital energy level of several adsorbents and gallic acid calculated with the semiempirical molecular orbital method PM3. The result shows that chemical interaction will be in existence in the adsorption system of gallic acid in aqueous solutions with FZH01 as like that of GAC at the proper temperature. The adsorption capacities of gallic acid in aqueous solutions with the adsorption resins modified with 2-carboxylbenzoyl increase greatly and mechanism for adsorbing gallic acid in aqueous solution was investigated.
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