| The usage of oil usually causes much pollution, and they may occur during variousstages of its production, transportation and utilization. Oil pollutants are not only a loss ofenergy but also an adverse effect on wildlife. Recently, oil spill has become one of the mostserious problems, so it causes widespread concern and research hotspot. Although someadvanced technologies have been developed and introduced into the oily water treatment,such as chemical coagulation, microfiltration and ultrafiltration, the expensive initial andoperating cost inhibit the application of these methods. So, it is necessary to develop aneffective, economical and green technology to deal with the oil pollutants in water. Recentyears, Cellulose-based organic materials have been started to be used for oil removal frompolluted water. They have the advantages of selective removal of oil over water,biodegradability, relatively low cost, and limited impact on the environment.Corn is one of the major economical crops all over the world, and it produce abundant ofbyproducts such as corncob, corn leave and corn stalk, so the importance of utilization of ithas been realized. The usage of corn stalk as an oil-sorbent in the recovery of spilled oils hasreceived attention recently. Considering the oil sorption capacity of raw corn stalk isrelatively low, some modification methods should be taken in order to producehigh-efficiency oil-sorbent.In this paper, raw corn stalks (RCS) were used as raw materials, and the choices ofbiotechnology based on the use of cellulase and solid-state fermentation bylignincellulosic-degrading fungi in modification process were taken. These materials wereanalyzed by characterization, and their adsorption isotherm and kinetics were evaluated inbatch experiments. The main results are as follows:1. Corn stalks were treated using two kinds of cellulase as modifier, which includecellulase from Aspergillus niger and cellulase R-10, so as to achieve new kinds of modifiedbiosorbent for oil removal from water (named ACCS and RCCS). After6h cellulasetreatment of corn stalk at an enzyme loading of100U/g under45°C, ACCS got high sorption capacity of oils. After4h cellulase R10treatment of corn stalk at an enzyme loading of100U/g under50°C, RCCS got high sorption capacity of oils.2. Corn atalks, corncob and oak wood were treated using Aspergillus niger andPhanerochaete chrysosporium, and the optimum modification conditions were as follows: ForAspergillus niger modification with additional carbon, at30℃, the initial solid-liquid ratiowas1:3, and modification time was6days, ANCS, ANCC and ANWC were prepared; ForPhanerochaete chrysosporium modification in millet and wheat bran system (ratio was2:1),at37℃, after modification time of21days, PCCS, PCCC and PCWC were prepared.Compared the modification of both fungi, the effect of Aspergillus niger was better thanPhanerochaete chrysosporium, and cellulase as modifier was better than Aspergillus niger.Lignin is favor for oil adsorption.3. The main modification mechanisms were conclused from characrerization results andlignocellulose analysis. Both of cellulase and fungi modification could transformation of thecellulose structure, and decrease the value of CrI, and increase BET areas. The main reasonfor modification can be attributed to the penetration of cellulase and hyphae into thecrystalline region of cellulose, weakening of the glycosidic bonds and formation ofamorphous structures. Meanwhile, they could increase relative amount of hydrophobic lignin,and reduce relative amount of hydrophilic cellulose, so that the improvement of hydrophobicwas benefit to oil adsorption in oil/water system.4. The effects of sorbent dose (0.1to0.5g), initial oil amount (5to30g), and thesorption time were also studied. When at high initial oil amount and in small dosage, thesorption capacities of all materials were better, and ACCS was the best sorbent. The sorptionprecesses of ACCS, RCCS, ANCC, ANWC, PCCC and PCWC fitted for Langmuir sorptionisotherm, which means oil moleculors were adhered on their surface by single layer. Thesorption process of ANCS and PCCS was found to fit for Freundlich isotherm, which meanstheir sorption process takes place in a non-homogeneous surface of the multilayer adsorption,and they occurred physical sorption. All of these sorbents met the pseudo-second-orderkinetics, describing that the adsorption rate was relation with square driving force. Compared the half time of adsorption and initial adsorption rate, ANCS is the highest among thesesorbents.5. The main mechanism of adsorption of oil by cellulase and lignocellulose-degradingfungi modified corn stalks was physical adsorption depending on their larger surface, lowerdegree of crystallinity, and higher relative amount of lignin, leading to improve the adhesionto oil molecules by capillary force. |
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