聚氯乙烯(PVC)类医疗废物的热解特性研究

为研究含聚氯乙烯医疗废物的热解特性,选取输液管和尿样盒为对象,利用差热热重分析仪,在氮气气氛下进行热重实验,探讨了二者热失重行为和机制,分析了反应过程中热量变化及热解剩余物性状,建立了反应动力学模型.结果表明,输液管和尿样盒的降解过程以主要成分PVC的热解机制为主导,分别在约200～390℃和约390～550℃区间内,呈现两段主要的热解过程,最大热解速率分别出现在315℃和470℃左右;增塑剂可降低样品脱氯的温度并增加失重率,样品复杂的成分导致失重峰不规则且不平滑;热解过程为吸热反应,呈现2个明显的阶段,分别对应试样的两段热解,热延迟的存在导致DTA峰温稍滞后于对应的DTG峰温;建立的"整体两步四反应模型"能很好地描述输液管和尿样盒的热解行为.     

铝塑包装废物的热解特性研究

利用热重-差热-傅立叶变换红外光谱联用仪对铝塑包装废物热解特性进行分析,并对物料性质、纸质存在对热解过程的影响进行研究. 结果表明:铝塑包装废物热解主要发生于438～500 ℃,最大失重速率出现在470～475 ℃;产物中主要是—C—C—以及少量的—CC—与芳香烃;反应温度由50 ℃升至850 ℃,铝塑包装废物依次经历聚乙烯熔融软化、热解,铝熔融,铝与焦状物反应等过程;铝塑包装废物中含纸质时,在312.4～363.2 ℃增加了一个失重过程,同时高温时的热解反应更为复杂.      

城市生活垃圾典型组分的热解动力学模型研究

对城市生活垃圾中的典型组分进行热重特性试验，根据热失重曲线得出了反应力学参数及反应速率控制方程，进而提出了一个通用的反应速率函数式，提出热解指数这个指标来表征垃圾的热解特性。结果表明：１．垃圾组分中，塑料、橡胶、植物类厨余热解符合三段模型，其余组分符合二段热解模型，在不同的温度范围内，热解的反应机理是不同的，且反应动力学参数也不相同。２．同一种组分，影响其反应速率的主要因素是反应动力学常数，升温速     

模拟医疗废物在管式电阻炉上的热解特性研究

在管式电阻炉上对由聚丙烯、面巾纸、纱布、医用脱脂棉、一次性口罩、医用乳胶手套等按一定比例组成的模拟医疗废物在氮气气氛进行了热解研究。重点探讨了10K／min，20K／min，30K／min和40K／min等不同升温速率对热解产物分布、产气特性和热解过程的影响。结果表明，随着温度升高，模拟废物的热解产生气体的主要成分逐渐由CO2和CO转变为C3H6、CH4、C2H6、C2H4和C3H8。同时，热解处理对模拟废物的减量化效果比较明显，固体残留率仅为5．61％～7．02％。而且，加热速率对模拟医疗废物热解过程的影响较大。     

热重法研究模化城市生活垃圾燃烧和热解特性

利用热重技术研究了模化城市生活垃圾(model municipal solid waste，MMSW)的热解和燃烧过程的特性。结果表明，在小于300℃的温度范围内，热解和燃烧的失重曲线基本一致，不同升温速率对失重特性有影响。利用分峰拟合处理技术对MMSW热处理过程的DSC曲线进行分析，发现MMSW燃烧和热解的失重特性基本上是所含物质失重特性的叠加。对MMSW热处理过程进行动力学分析，计算结果表明反应级数在1．2～1．8之间，化学反应的平均活化能在30～50kJ／mol之间。     

医疗废物典型组分在回转窑内的热解-气化研究

在小型回转窑上对模拟医疗废物的4种典型组分进行了批量热解-气化试验.实验结果表明,热解-气化反应物料的转化率较高（80%～100%）,基本上随热解-气化终温（FPT）的升高而升高.热解-气化反应中物料的热裂解反应在30min以内基本结束.FPT的升高,有利于挥发分的析出、减少残渣量和处置时间.从试验结果来看,第一段初级处理中采用约700℃的回转窑反应温度比较适合实现医疗垃圾的完全热解和气化.     

废旧聚氨酯硬泡热解特性

采用热重分析仪对废旧聚氨酯硬泡在氮气中的热失重行为进行了研究,并对升温速率、热解终温对热解的影响进行了分析. 结果表明:在氮气气氛条件下,废旧聚氨酯硬泡热解主要发生在200～492 ℃;随着升温速率的提高,废旧聚氨酯硬泡热失重时挥发分初析温度向高温方向偏移,失重速率峰值(DTG_max)显著增大.利用热重-红外(TG-FTIR)联用方法对氮气气氛中10 ℃/min升温速率下的样品热解气体产物进行了检测. 结果表明:废旧聚氨酯硬泡热解产物有H₂O,CO₂,CO,CFC-11,以及含氯化合物、烯烃类、烷烃类和带有苯环等官能团的化合物,且主要气体产物有相似的析出规律.      

医疗废物典型物料热解过程中无机氯的气相迁移规律

在温度为600～900℃、氮气气氛下.用管式炉实验台对医疗废物典型组分--棉花和聚丙烯(PP)进行了快速热解实验.为了研究氯的迁移规律,对物料添加了适量的盐水,结果表明,医疗废物典型组分和NaCl溶液混合热解的过程中Cl的析出随着热解温度、热解时间和物料与Cl元素质量配比的改变而改变.研究发现,Cl的析出峰在以棉花为物料时出现在800℃,而用PP为物料时出现在700℃;随着热解时间的变化,Cl的析出率呈现不规律的变化:700℃棉花热解实验中,热解时间5min时.Cl的析出率只有0.0002,在10min时,析出率达到了0.0003;而在800℃棉花的热解实验中,5min时Cl的析出率为0.00062.而随着热解时间的增加,10min时,Cl的析出率却降到了0.00045.同时还发现,随着Cl元素含量的增加.其析出率也在提高,当Cl和物料质量比值增加1倍时,Cl的析出率也随着温度的变化相应的增加2～4倍.     

麦草浆黑液固形物热解特性及动力学研究

通过热重分析实验和固定床热解实验研究了麦草碱性亚硫酸钠-蒽醌法制纸桨黑液固形物的热解特性和热解产物分布。结果表明:黑液固形物热解过程分为干燥脱水、有机物热解和无机物转化三个阶段,主要失重发生在200～550℃间;在热重分析基础上按一级反应动力学模型得到了黑液固形物热解各阶段的动力学参数;实验条件下,麦草浆黑液固形物固定床热解后约三分之一转化为挥发分,余下为固体残渣。     

升温速率对医疗垃圾热解机理的影响

用TGA-DTA差热失重联用分析仪研究升温速率对输液瓶、一次性医用手套、敷料内心和白鼠肌肉4种典型医疗垃圾热解过程的影响规律.结果表明:在其他试验条件都相同的情况下,随着升温速率的提高,热解反应起始温度、终止温度、峰温升高,反应区间ΔT变宽,发生最大热失重速率的温度也升高,热失重峰的峰高也随之增加;升温速率对热失重率的影响随医疗垃圾种类而不同,对较难分解的医疗垃圾（如敷料内心和白鼠肌肉等）影响大,对容易分解的医疗垃圾（如输液瓶和一次性医用手套等）影响较小.      

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.