镰刀菌HJ01对对氯苯酚的降解特性

采用实验室分离的一株镰刀菌HJ01,以对氯苯酚(4-CP)为降解底物,以蔗糖为外加碳源,考察了蔗糖质量浓度、降解温度、初始pH对4-CP降解效果的影响,初步探讨了镰刀菌HJ01对4-CP的降解动力学和降解机理.实验结果表明:该菌株能以4-CP为惟一碳源和能源生长;在外加蔗糖为碳源,蔗糖质量浓度为3 g/L、降解温度为30℃、初始pH为8的条件下,50 mg/L4-CP能在6 d内被完全降解.以4-CP为惟一碳源和外加蔗糖下的降解动力学分别符合Haldane模型和一级动力学方程.     

不同碳源对微生物修复石油污染土壤的促进作用

为解决石油污染土壤中以石油为唯一碳源的土著微生物生长缓慢的问题,研究了分别添加玉米淀粉、玉米粉、可溶性淀粉和葡萄糖4种碳源对土样细菌总量和石油烃降解率的影响。研究结果表明：玉米淀粉作为碳源时土样TN和TP的下降幅度均最大;添加玉米淀粉和玉米粉比添加可溶性淀粉和葡萄糖更有利于细菌的生长繁殖;细菌对直链烷烃化合物均具有较好的降解效果,但对较为复杂的芳香烃化合物降解效果较差。降解反应第40天时,分别添加玉米淀粉、玉米粉、可溶性淀粉和葡萄糖的石油烃降解率分别为67.25%、48.60%、46.30%和28.57%。     

外加营养源对氯氰菊酯降解菌GF31降解特性的影响

利用本实验室保存的一株铜绿假单胞菌(Pseudomonas aeruginosa)GF31,考察了外加不同的碳、氮源对菌株降解氯氰菊酯特性的影响.实验结果表明:适量浓度的碳、氮源对降解有明显的刺激作用,外加碳源中葡萄糖的刺激作用最为明显,外加0.8 g/L的葡萄糖,氯氰菊酯降解率提高了13.7%;外加氮源中以蛋白胨对微生物的促进作用最突出,当外加5.0 g/L蛋白胨时,氯氰菊酯降解率从27.5%提高到70.0%;降解5 d后,氯氰菊酯的降解已基本趋于平衡.     

Si-FeOOH催化臭氧氧化法降解苯胺

通过掺杂Si提高FeOOH的机械强度,制备无定型Si-FeOOH,并用于催化臭氧氧化降解苯胺。考察了n(Si)∶n(Fe)、Si-FeOOH加入量、溶液p H、初始苯胺质量浓度等因素对苯胺去除率的影响,并研究了SiFeOOH的重复利用效果与铁离子的溶出情况。实验结果表明:Si-FeOOH对臭氧氧化降解苯胺具有明显的催化作用,Si-FeOOH催化臭氧氧化对苯胺的降解效果明显高于单独臭氧氧化和FeOOH催化臭氧氧化;在溶液p H为11、Si-FeOOH加入量为1.0 g/L、n(Si)∶n(Fe)=0.55的最佳降解条件下处理初始苯胺质量浓度为300 mg/L的苯胺溶液,降解10 min后,苯胺去除率可达100%;Si-FeOOH催化剂经5次重复使用后,苯胺的去除率仍高达97.8%,且铁离子的溶出量明显低于FeOOH。     

镰刀菌HJ01对苯酚的降解性能

为了研究真菌对苯酚的降解能力，采用本实验室分离的一株镰刀菌HJ01，考察了外加碳源、降解体系初始pH、温度对HJ01菌体生长量和苯酚降解效果的影响，初步探讨了镰刀菌降解苯酚的动力学与机理。实验结果表明，该菌能以苯酚为惟一碳源生长，添加适量的蔗糖可促进HJ01菌体的生长及苯酚的降解。在蔗糖加入量为3g／L、降解体系初始pH为6．0、温度为30℃的最佳条件下，经HJ01菌处理4d后的质量浓度为420mg／L苯酚废水中的苯酚完全降解。镰刀菌的生长和苯酚降解动力学符合Andrews模型。     

SBR工艺脱除苯胺废水中的总氮

采用SBR工艺脱除苯胺废水中的总氮。实验结果表明:在废水温度为30℃、废水pH为7.8、COD为513.6mg/L、ρ(NH3-N)为75.95mg/L、总氮质量浓度为521mg/L、m(C)∶m(N)为1∶1、不补充碳源的条件下,停曝搅拌时间需8h,废水的总氮去除率为22.0%。以甲醇作为补充碳源,当m(C)∶m(N)为3∶1时,总氮去除率较低,停曝搅拌时间需10h;当m(C)∶m(N)为5∶1时,总氮去除率较高,达46.5%,停曝搅拌时间需12h。补充碳源为甲醇时,所需停曝搅拌时间最短,总氮去除率最高,优于以葡萄糖和有机废水为碳源。     

电气石对脱氯菌降解三氯乙烯的影响

以电气石作为环境微生物强化介质材料,协同以Dehalococcoides spp.为主体的脱氯混合菌群(简称脱氯菌)对水中的三氯乙烯(TCE)进行降解,探讨了电气石对降解效果的影响。实验结果表明:电气石可调节水溶液的p H使之趋向于中性并提高水溶液的电导率;在脱氯菌接种量为8%、电气石加入量为5.0 g/L的条件下降解20mg/L的TCE,84 h时TCE已全部降解,而未加电气石体系只降解了54.7%;外加电子供体甲醇和外加电气石均可明显提高脱氯菌对TCE的降解速率,且外加电气石的降解效果更好,说明电气石可能在促进微生物生长繁殖的同时也能为其提供合适的电子供体,这对降解地下水中的TCE具有重要意义。     

活性艳蓝X-BR降解菌的筛选

从某印染厂废水排放出口的污泥中分离到一株活性艳蓝X-BR染料高效降解菌LPY68-14,经生理生化鉴定,该菌为埃希氏菌(Escherichia sp.).研究了影响菌株LPY68-14降解效果的因素,实验结果表明:在缺氧、质量分数为0.2%葡萄糖为外加碳源、温度37℃、接种量4 mL、pH 7的最佳条件下,质量浓度为30 mg/L的活性艳蓝X-BR经菌株LPY68-14处理24 h后的降解率可达80%;当活性艳蓝X-BR质量浓度为100～400 mg/L时,该菌处理48 h后的降解率可稳定在70%左右.     

Fenton试剂降解选矿废水中残余黄药

采用Fenton试剂处理选矿废水中残余的黄药,分别考察了氧化时间、反应初始pH、Fe^2 浓度及H2O2用量对黄药降解效果的影响;用正交实验确定了4个因素的最佳条件。结果表明,反应初始pH和H2O2用量是影响黄药去除效果的主要因素。氧化时间为60min、反应初始pH为4、Fe^2 质量浓度为20mg／L、H2O2质量浓度为20mg／L、黄药质量浓度为：125mg/L时,黄药的去除率达到99．5％,COD去除率为87．5％。     

选矿废水中微量黑药的测定

介绍用分光光度法测定选矿废水中微量黑药的技术。该法具有良好的重现性和准确性，用该法测定废水中黑药，检出限为０．０１ｍｇ／Ｌ，变异系数为１．８２％，回收率为９８％－１０２％。采取控制加热、加入锌盐和调节溶液酸碱度等措施，可分别消除黄药、硫化物及铁离子的干扰。     

Biodegradability of Starch Based Self-Supporting Antimicrobial Film and Its Effect on Soil Quality

Alarming environmental pollution from petroleum based non-biodegradable disposable packaging films has generated concern for development of alternatives from natural polymers such as starch. In the present work, the biodegradability of a self-supporting film made from starch and polyvinyl alcohol (PVA) (starch:PVA?=?9:1 as the polymer) together with glutaraldehyde as crosslinker and sodium propionate (SP) as antimicrobial was investigated by soil burial method. The changes in soil composition namely pH, organic carbon, available and total nitrogen, and water holding capacity as a result of biodegradation were also estimated. The film underwent ≈?90% biodegradation within a period of 28 days, with simultaneous increase in soil nutrients. Moreover, the pH remained in the accepted limit for plant growth. Thus, antimicrobial in the film did not hamper its biodegradation, rather disposal of the film in soil might facilitate plant growth.     

Physical Properties of Chemically Modified Starch(RS4)/PVA Blend Films—Part 1

In this paper, we report on the physical properties of films that have been synthesized by using native corn starch (NS) and chemically modified starch (RS4). NS or RS4/PVA blend films were synthesized by using the mixing process and the casting method. Glycerol (GL), sorbitol (SO), and citric acid (CA) were used as additives. The chemically modified starch (RS4) was synthesized by using sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) as a crosslinker. Then, the RS4 thus synthesized was confirmed by using the pancreatin-gravimetric method, swelling power and an X-ray diffractometer (XRD). Tensile strength (TS), elongation (%E), swelling behavior (SB), and solubility (S) of the films were measured. The result of the measurements indicated the RS4-added film was better than the NS-added film. Especially, the RS4/PVA blend film with CA as an additive showed the physical properties superior to other films.     

Evaluation of the Biodegradability of Polyvinyl Alcohol/Starch Blends: A Methodological Comparison of Environmentally Friendly Materials

Polyvinyl alcohol (PVA) and starch are both biodegradable polymers. These two polymers can be prepared as biodegradable plastics that are emerging as one of the environmental friendly materials available now. In this study, after reacting with sodium trimetaphosphate (STMP), modified corn starch was blended with PVA in different ratios by a barbender. Test samples were prepared for mechanical and thermal properties measurements. The surface roughness and morphology of fractured surface of the samples were observed by an atomic force microscopy (AFM) and scanning electron microscope (SEM) measurements. Aqueous degradation by enzyme, water absorption and biodegradability behavior were evaluated for the degradability. The biodegradability of these materials was followed by bio-reactivity kinetics models. Results showed that the addition of modified starch could enhance its water uptake. With an addition of 20 wt% of modified starch, the blend had a maximum weight loss during enzymatic degradation. It was found that the degradability was enhanced with the addition of the starch. Analyzing the results of the biodegradability based on the kinetic models, the growth rate of the microorganism was found to be increasing with the increase of the content of starch in the PVA/starch blends in the first order reaction fashion. In our biodegradability analysis, i.e., based on the China national standards (CNS) 14432 regulations, we estimated the decomposition behavior based on the mentioned first order reaction. We found that the PVA/starch blends would take 32.47, 16.20 and 12.47 years to degrade by 70% as their starch content 0, 20 and 40 wt%, respectively.     

Photodegradation and Biodegradation Study of a Starch and Poly(Lactic Acid) Coextruded Material

To simulate the behavior of agricultural mulch coextruded poly(lactic acid)(PLA)/starch films, two stages were carried out. The first was an ultraviolet treatment (UV) at 315 nm, during which glass transition temperature T_g, weight, and molecular weight (MW) decreased and a separation between PLA and starch phase was observed. For the second stage, the mineralization of the carbon of the material was followed using the ASTM (D 5209–92 and 5338–92) and ISO/CEN (14852 and 14855) standard procedures. To measure the biodegradability of polymer material, the assessment of the carbon balance allowed determination of the distribution between the carbon rate used to the biomass synthesis or the respiration process (released CO₂), as well as the dissolved organic carbon into the culture medium and the carbon in the residual insoluble material. The influence of the nature of the medium and the standardized procedures on the final rate of biodegradation was investigated. Whatever the standardized method, the biodegradation percentage was significantly stronger in liquid medium (92.4–93.4) than on inert medium (80–83%). In the case of the compost process, only released CO₂ was measured and corresponded to 79.1–80.3%.     

Biodegradable kinetics of plastics under controlled composting conditions

This study models and evaluates the kinetics of C-CO₂ evolution during biodegradation of plastic materials including Polyethylene (PE), PE/starch blend (PE/starch), microcrystalline cellulose (MCE), and Polylactic acid (PLA). The aerobic biodegradation under controlled composting conditions was monitorated according to ISO 14855-1, 2004. The kinetics model was based on first order reaction in series with a flat lag phase. A non-linear regression technique was used to analyze the experimental data. SEM studies of the morphology of the samples before and after biodegradation testing were used to confirm the biodegradability of plastics and the accuracy of the model. The work showed that MCE and PLA produced the high amounts of C-CO₂ evolution, which gave readily hydrolysable carbon values of 55.49% and 40.17%, respectively with readily hydrolysis rates of 0.338 day⁻¹ and 0.025 day⁻¹, respectively. Whereas, a lower amount of C-CO₂ evolution was found in PE/starch, which had a high concentration of moderately hydrolysable carbon of 97.74% and a moderate hydrolysis rate of 0.00098 day⁻¹. The mineralization rate of PLA was 0.500 day⁻¹ as a lag phase was observed at the beginning of the biodegradability test. No lag phase was observed in the biodegradability testing of the PE/starch and MCE. The mineralization rates of the PE/starch and MCE were found to be 1.000 day⁻¹, and 1.234 day⁻¹, respectively. No C-CO₂ evolution was observed during biodegradability testing of PE, which was used for reference as a non-biodegradable plastics sample.     

Production of Curdlan Grown on Cassava Starch Waste Hydrolysates

Cassava starch waste hydrolysates (CSWHs) with different degrees of polymerisation, i.e., CSWHs-1, CSWHs-2 and CSWHs-3, were prepared through the hydrolysis of cassava starch waste with thermostable a-amylase from Thermococcus sp. HJ21. The prepared CSWHs were then used as a carbon source for curdlan production with Alcaligenes faecalis ATCC 31749. The amount of curdlan produced and the glucosyltransferase activity during curdlan synthesis increased more obviously when CSWHs-2 was used as the carbon source than when glucose was used. Using both carbon sources, the maximum curdlan production was observed at day 5, and the maximum glucosyltransferase activity was observed at day 4. Glucosyltransferase activity decreased thereafter, and biomass continued to increase until the end of the experiment (day 6). Results indicated that the enhanced curdlan production with CSWHs as the carbon source was highly correlated with glucosyltransferase activity.     

Structure-biodegradation relationships of polymeric materials. 1. Effect of degree of oxidation on biodegradability of carbohydrate polymers

The biodegradability of oxidized starch and inulin has been studied in relation to the degree of periodate oxidation to dialdehyde derivatives, by measuring oxygen consumption and mineralization to carbon dioxide. A higher degree of oxidation of dialdehyde starch and dialdchyde inulin results in a lower rate at which the polymers are biodegraded. It is demonstrated that the biodegradation rate of dialdehyde inulin derivatives decreases more than that of equivalent starch derivatives. The differences in biodegradation behavior between dialdehyde starch and dialdehyde inulin, resulting from comparable modifications, are discussed in terms of conformational structure.     

New Biopolymer Nanocomposite of Starch-Graft Polystyrene/Montmorillonite Clay Prepared Through Emulsion Polymerization Method

Starch-g-polystyrene (Starch-g-PS)/Montmorillonite nanocomposites were prepared via free-radical graft copolymerization of styrene and starch in the presence of montmorillonite clay, by emulsion polymerization method using potassium persulfate (KPS) as an initiator/catalyst and sodium dodecylbenzensulfonate (SDBS) as an emulsifier. The nanocomposites with different clay content 0, 2.5, 5.0, 7.5 and 10 weight percent of starch were prepared and the changes in layer-stacked structures of the clay particles in the resulted nanocomposite compounds were examined by using of X-ray diffraction and FT-IR spectroscopy. Finally the thermal degradation behavior and morphology of nanocomposites were studied using thermal gravimetric analysis (TGA) and SEM, respectively.     

A Novel Hybrid 2,4-Dichlorophenoxy Acetate Bead from Modified Cassava Starch and Sodium Alginate with Modified Natural Rubber Coating

A novel herbicide bead was developed by phase separation, utilizing modified cassava starch (CSt), sodium alginate (SA) and 2,4-dichlorophenoxy acetate (2,4 DA), and the beads were also coated with natural rubber grafted with cassava starch (NR-graft-CSt) to aid their water resistance. The alginate gel beads with 65% entrapped 2,4 DA showed 90% release within 24 h. The incorporation of CSt in the beads markedly improved their encapsulation efficiency to 98% and sustained the release of the herbicide for 700 h. The water resistance was improved by coating the beads with NR-graft-CSt when compared with the pure CSt/SA bead. The synthesized bead has excellent potential for agricultural applications.