Advanced Materials Research Vols. 821-822

Abstract: In this article,cassava starch was cross-linked by crosslinking agent sodium tripolyphosphate in the microwave oven. The effect of microwave time on the cross-linking degree and morphology of cross-linked starch were investigated. The results show that with the increase of microwave processing time, the degree of crosslinking of starch increases.Phosphate ester group is formed on the starch molecular chains and the structure of cross-linked starch becomes amorphous by microwave irradiation .

Abstract: Chemical semi-syntheticmethod for efficient low toxicity of paclitaxelanalogues is the hot issue quite a longtime in the present and the future of chemical, biological medicine and relatedinterdisciplinary researches. 10-DABIII is the main precursor semi-syntheticraw materials. Taking Enshi’s perennial natural taxus chinensis and taxuschinensis leaves of artificial cultivation as raw material to study the effectof different drying methods and extraction methods on the contents of 10-DABIII.Experimental results show that the 10-DABIII in the natural taxus chinensis ishigher than that of artificially cultivated taxus chinensis; different dryingmethods affect the amount of 10-DABIII, that is, by contrast, drying processingmethod in 50°Clow temperature is superior to drying in the shade of the nature, and microwaveextraction is more efficient than conventional solvent one. Knowing the contentof 10-DABIII in Enshi’s taxus chinensis can provide the necessary experimentaldata for rational utilization of taxus chinensis medicinal material resources, topromote Enshi’s local economic development.

Abstract: The reaction of the xylan-type hemicellulose with 2,3-epoxypropyltrimethylammonium chloride and acrylamide in ethanol-water-alkali slurry yielded water-soluble, cationic etherified xylan-type hemicellulose derivatives. The degree of substitution (DS) value reaches up to 0.40 by adjusting the mass ratios (NaOH/hemicellulose, total etherifying agents/hemicellulose and 2,3-epoxypropyltrimethylammonium chloride/acrylamide), the reaction temperature and the reaction time in a one-step synthesis. The etherified hemicellulose was characterized by infrared spectroscopic analysis (FT-IR), Zeta potential analysis, charge density analysis and thermogravimetric analysis (TGA). It is found that Zeta potential is promoted from-30.50mv to +35.81mv and charge density is promoted from-0.50mmol/g to +0.88mmol/g during etherification under the conditions used. The thermal stability of the etherified hemicellulose is lower than that of the unmodified xylan-type hemicellulose polymers.

Abstract: In this work, hemicellulose was extracted from corn stover by pretreatment with potassium hydroxide (KOH) solution, and the influences of pretreatment conditions on hemicellulose extraction were investigated. The dissolution rate of xylan from the raw material was used to indicate the extraction yield of the hemicellulose. The results showed that under the conditions of temperature 85 °C, alkali concentration 6%, liquor/solid ratio 8:1 and time 120 min, high xylan extraction yield of 43.74% (based on the xylose content of raw material) was achieved. The content of saccharides and uronic acids in the hemicellulose was 80.22%. The hemicellulose was characterized by FT-IR and TG/DTG after being separated from the hydrolysates by precipitation of the neutralized hydrolysate with 3 times volumes of ethanol.

Abstract: The advanced pretreatment by electrolysis of Bohai seawater in Tianjin used a diaphragm electrolyzer in the experiment. Removal efficiency and influence factors of the method were analyzed. Results show that turbidity, organic compounds, SDI and chroma of seawater were effectively decreased by electrolysis. Removal efficiency was significantly increased by current density, operation time and inter-electrode distance, and the optimum electrolytic conditions was determined as inter-electrode distance of 2 cm, current density of 15.87 mA·cm^-2, operation time of 10 minutes. It was investigated that when the water quality after electrolysis was of pH 8.6, the chroma and turbidity decreasing trend slowed down, with chroma of 0.052 A, removal rate reached 88.4%; the residual turbidity reduced to 2.52 NTU, removal rate reached 90.71%. A PH of about 8.5, COD_Cr decreasing trend slowed down, and when COD_Cr < 750 mg/L, it conformed to the requirements of the reverse osmosis water. With the study on neutralization of steel pickling waste liquor by the by-product of magnesium hydroxide, it is found that the quality of treated water reached 3^rd level national emissions standards (300-1000 mg/L). Magnesium hydroxide slurry of Cr (VI) removal rate reached 100%, conforming to the 1^st level national industrial wastewater discharge standards (< 0.5 mg/L).

Abstract: The catalytic activity of many Lewis and Bronsted acid for the synthesis of diethyl carbonate (DEC) from ethyl carbamate (EC) and ethanol was evaluated in a bath reactor. Pyrophosphoric acid (H₄P₇O₂) which showed the best activity was selected to further investigate the effect of reaction conditions, such as reaction temperature, catalyst dose and reaction time, on the yield of DEC. Under the optimal conditions, DEC yield can reach 29.1%.

Abstract: Batch test had been carried out to determine the potential and the effectiveness of the novel composite adsorbent in removal of fluoride, iron and manganese from aqueous solution. It was found that the composite adsorbent could effectively not only remove Fe (II) and Mn (II) also fluoride from water, the maximum adsorption capacities for F^-, Fe (II) and Mn (II) were 4.09mg·g^-1 4.00mg·g^-1 and 3.50mg·g^-1 respectively. Kinetics data obtained for the adsorption process fitted the Lagergren First-order equation. The Langmuir adsorption isotherm was found to fit the experimental data derived from F^- (R²= 0.9992), Fe (II) (R²=0.9858) and Mn (II) (R²=0.9876) removal. Both Fe (II) and Mn (II) removal increased with increase in solution pH, but F^- removal remained relatively stable in pH 4.0~9.0. The process of adsorption of F^-, Fe (II) and Mn (II) from aqueous solutions by the composite adsorbent was an endothermic process. The above results indicated the composite adsorbent can be possibly applied in F^-, Fe (II) and Mn (II) removal from drinking water.

Abstract: As a novel nanofunctional material, bacterial cellulose (BC) has been widely applied in food, papermaking, medical, spinning, acoustics, and chemical fields owing to the high purity, the nanoscale fine network structure and etc. The production of BC is significantly affected by nutrients such as carbon and nitrogen sources. Particularly, the output, form and structure of BC are affected by ethanol, organic acids and other chemical substances. Cheaply available raw materials, including fruits, molasses and other natural ones, are emphasized in this review.

Abstract: Reverse Osmosis (RO) is an effective method to get fresh water from seawater or brackish water. The uncontrolled discharge of RO concentrated brine can contaminate water aquifers and damage marine ecosystems. The techniques to treat or utilize the rejected brine are the research focus in recent years. This paper tried to give an overview of latest development in this filed in order to provide references for its actual application in large-scale engineering.

Abstract: One new pretreatment method was developed for solving the formed fouling on the equipments in the process of reverse osmosis seawater desalination, and the effect of different pretreatment methods on the membrane fouling was investigated. The experiment results showed that the flux attenuation rate of reverse osmosis membrane used in hardness-removed seawater was slower than the one of direct ultrafiltration seawater, and the salt reject rate and conductivity of output water from reverse osmosis membrane were not obviously affected by these two different pretreatment methods respectively. By according to the characterization of SEM, EDX and IR, the rapid attenuation of membrane flux was caused by the piled inorganic crystals on the membrane surface in direct ultra-filtration process, and the hardness-removed pretreatment process can effectively decrease the membrane fouling.