Wheat straw washed

The samples used in this study were Danish wheat straw pellets which were milled on a laboratory ultra centrifugal mill (Retzsch ZM 100) mounted with a 1 mm screen. In addition, washed wheat straw was used. The washing procedure was as follows 1 g of milled straw was placed in 200 ml deionized water and stirred for 20 hours at room temperature, then filtered and washed with 300 ml deionized water, before drying [1,6,8]. 

The pyrolysis of wheat straw and washed wheat straw show different pyrolysis behavior. Besides a lower onset temperature of the pyrolysis and a higher char yield of the wheat straw, the main difference is the shape of the mass loss rate curves. The pyrolysis of wheat... 

Fig. 1 The pyrolysis of wheat straw and washed wheat straw at lO CVniin.

The shape of the mass loss and mass loss rate curves determine the types of kinetic models that can be applied to fit the data. Simple kinetic models, which only include one reaction, may be applied to describe the pyrolysis of wheat straw, but cannot describe the two peaks observed in the pyrolysis of washed wheat straw. 

All four models were used to fit the pyrolysis of wheat straw, but only the superposition model was used to fit the pyrolysis of washed wheat straw. Ail four models have the flaw that they arc not able to predict the char yield, which then has to be given as input to the models. Prediction of char yield can only be done by more complicated models. 

The superposition model was also applied for the pyrolysis of washed wheat straw, where a multi-reaction model is required to fit the data. Experiments show that the DTG-curves have two distinct peaks, which makes the kinetics determination easier than for raw straw. Fig. 9 shows the fit of three reactions to the mass loss rate data from the pyrolysis of... 

Table 5 Kinetics for the pyrolysis of washed wheat straw at 10°C/min 3 parallel reactions (for both mass and mass loss rate data).

Pyrolysis of wheat straw and washed wheat straw has been carried out by simultaneous thermogravimetric analysis and differential scanning calorimetry at heating rates of 5,10 and 40 C/min. 

Powdered wheat (Triticum aestivum) straw has been modified with urea under the effect of microwave radiation and used for the removal of Cd(II) ions from aqueous solution in a batch process [102]. Dried straw from wheat was washed, ground, and screened to a particle size of less than 100 pm. The powder was soaked in distilled water for 2 days, then washed with distilled water, and dried at 80°C to constant mass. Wheat straw and urea were blended in a ratio of 1 2 by mass and were exposed to microwave radiation (2450MHz) for 12min. Then it was boiled in water for 300min and filtered while hot, washed with hot water, and dried at 80°C to constant mass. The chemical modification of wheat straw with urea through microwave radiation is illustrated in Figure 5.18. 

To the flasks for the crop and soil samples (Section 6.1), add 2mL of 0.01 M Tris-HCl buffer solution (pH 7.7) and 50 and 100 qL of 1M Tris-HCl buffer solution for wheat grain, bariey grain and rice straw, and for soil, respectively. Adjust the pH to about 7.7 (confirm the pH with a pH test paper using the sample of untreated area). Homogenize the residue with ultrasonication and transfer the homogenate to the top of an ion-exchange column. Wash the flask twice with 2mL of 0.01 M Tris-HCl buffer solution and transfer the washings to the column. Elute the column with 40 mL of the same buffer solution. Discard this eluate. 

In the latter part of the 1950s, this author (Hayes, 1960) attempted to repeat the experimentation used by Waksman and Iyer (1932,1933). He exhaustively washed powdered wheat straw with boiling water, then with hot dilute hydrochloric acid, and extracted twice for 5h in an autoclave at 120 °C, each time with a 4% sodium hydroxide solution. The combined filtrates were acidified to pH 4 with hydrochloric acid and the precipitate formed was washed free of chloride and freeze-dried. A ligno-casein complex was formed by reacting three parts of the lignin extract and one part casein in a 0.1 M solution of sodium hydroxide and collecting the precipitate formed when the pH was adjusted to 4. This complex was washed free of chloride and freeze-dried. A 6 1 lignin-protein complex was formed in the same way. 

A sample of 5 g dry ground straw was treated with 200 ml NaOH solution (concentrations of 0.25 and 0.50 mol/l) for 2 h at different temperatures (30 and 55 °C). After the indicated period of treatment, the sample was acidified to pH 5 with glacial acetic acid, concentrated to about 30 ml under reduced pressure, and then filtered. The alkali-soluble hemicelluloses were then precipitated by pouring the concentrated supernatant fluid with four volumes of 95% ethanol (20 °C, 24 h). The precipitates were recovered by filtration, washed with 70% ethanol, and air dried. The scheme for fractionation of hemicelluloses from wheat straw is illustrated in Fig. 3. 

Previous studies investigating the SSF of pretreated wheat straw have mostly been conducted with washed material, substrate concentrations less than 10% DM, and higher enzyme loading [6, 11, 26, 27]. Nevertheless, the overall ethanol yields obtained in those studies (60-70%) are in the same range as the results reported herein. In an SSF study with wheat straw with rather similar substrate concentration (16% DM), a cellulose conversion of 70% was obtained [8]. However, this yield was obtained with washed pretreated material, which could be due to the potential removal of inhibitors for both enzymes and the yeast. 

Unlabeled wheat straw obtained locally was hexane washed, dried, soaked at 4 C in water that was decanted, and then either fermented directly or after further water washing. Also, at the end of the 4 soak the straw was broken up in a Waring Blendor to prevent trapping of water Inside the hollow straw stem. 

Wheat bran and sodium hydroxide were blended at room temperature in a separate reactor one hour before each experiment. Tlie initial L/S ratio was seven and the mixture was stirred for five minutes. The L/S ratio was increased to ten just before the introduction of the mixture into the twin screw extruder with a Nemo excentric-screw pump. Straw was introduced in the extruder s first section with a screw feeder. Straw was mixed with the alkaline dough in the first zone of the barrel through the neutral pitch element and the reverse-pitch screw element successively. The washing water was injected downstream from this zone, and the mixture was conveyed through the second reverse pitch located just downstream from the filtration module. The filtrate was collected and kept in a cold room before further processing, while the refined cellulosic fibres were gathered at the barrel outlet. 

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