焦化厂土壤中PAHs的热脱附行为及其对土壤性质的影响

采用滚筒式间接加热设备,在50~450℃加热温度和30 min停留时间实验条件下,测试了焦化厂污染场地低含量(S1)和高含量(S2)PAHs污染土壤中16种PAHs的热脱附效率和残留量的变化,并初步分析了热脱附处理对土壤有机碳(TOC)、可溶性有机碳(DOC)、比表面积(SA)和粒径分布的影响,结果表明:加热温度、污染物含量和污染物分子量对PAHs的脱附效率均存在极显著影响(p0.01),其中加热温度影响程度最大。S1和S2土壤中各类PAHs在加热温度达到其熔点附近开始有效脱附,LPAHs(低分子量PAHs)与HPAHs(高分子量PAHs)之间的热脱附效率仅在不超过300℃(S1土壤)和400℃(S2土壤)加热条件下存在明显差别。土壤中各类PAHs的脱附与其有效态密切相关,S1和S2土壤中有效态PAHs分别在200~250℃和250~300℃加热条件下几乎全部脱附。450℃加热温度条件下,S1和S2土壤中∑PAHs(总PAHs)脱附效率能够达到91.3%和98.4%,其中8种目标PAHs的含量范围分别为0.07~0.71 mg·kg-1和0.26~40.20 mg·kg-1,土壤中部分PAHs仍超过相应的北京市《场地土壤环境风险评价筛选值》住宅用地筛选值;450℃加热温度下,S1和S2土壤中TOC含量分别下降51.4%(p0.05)和23.1%(p0.05),S1和S2土壤中DOC变化趋势相反,SA的下降、较粗颗粒比例略有增加和电镜扫描中土壤颗粒团聚现象相吻合。     

聚苯乙烯改性聚丙撑碳酸酯的制备和表征

在聚苯乙烯(PS)的黏流温度以下制备了聚丙撑碳酸酯(PPC)和PS的共混物,研究了配比对PPC/PS共混物的热降解、形貌、力学性能和水蒸气阻隔性的影响。结果表明,共混物的黏度随PS含量增加而增大。PS促进了PPC的热降解。PS质量分数为50%～70%时,共混物为共连续结构。其他配比下,共混物呈海岛分相,分散相呈片层状。随PS含量的提高,共混物的弹性模量、拉伸强度和洛氏硬度提高,断裂伸长率降低。38℃下,共混物的水蒸气渗透率随PS含量的增加而降低,而在20℃下,变化趋势相反。当PS质量分数为50%时,共混物的水蒸气渗透率在20～38℃内不随温度改变。     

聚乳酸的热降解性能研究

研究了聚乳酸(PLA)在10-40 min和170-200℃的条件下热降解后的特性粘数和端羧基含量的变化。结果表明,在一定温度下,PLA熔体特性粘数随熔融时间的延长而下降,在一定时间下,随熔融温度升高而下降,端羧基含量随熔融温度升高而增大,在PLA成型加工中,应严格控制加工温度。     

共混沥青烟中16种多环芳烃的释放规律

通过气相色谱仪和气相色谱-质谱联用仪(GC-MS)对共混沥青(即煤焦油沥青(CTP)与石油沥青(PP)混合)受热时,释放沥青烟中多环芳烃(PAHs)的组成及含量进行分析。着重研究不同CTP掺混量、受热温度、受热时间和气氛等因素对美国环保署(EPA)重点监控的16种PAHs释放规律的影响。结果表明:共混沥青烟中含有8种EPA重点监控的PAHs,分别分布在三环和四环;受热时间对共混沥青中PAHs释放量影响较小,在1.5 h左右接近平衡;加热温度对PAHs释放量的影响很大,三环上的PAHs在160℃～180℃范围内释放增量最大,达到0.355 mg/g;四环上的PAHs在140℃～200℃范围内释放增量稳定在0.151 mg/g左右,未出现峰值;PAHs总释放增量在160℃～180℃范围内最大,达到0.507 mg/g;有氧条件下会降低沥青烟中PAHs的含量。     

燃烧条件对燃煤过程多环芳烃生成特征的影响

采用小型管式实验炉,通过控制燃烧温度、过剩空气量研究了不同燃烧条件对燃煤过程16种多环芳烃(PAHs)生成与分布的影响。实验结果表明:燃煤烟气中PAHs生成量随燃烧温度的升高而增加,灰渣中PAHs生成量随燃烧温度的升高呈先增加后减少的规律;随着过剩空气系数(α)的增大,烟气中PAHs生成量逐渐减少,灰渣中PAHs生成量呈先明显减少而后基本不变的趋势;PAHs组成的分布表现出三、四环含量突出的特征;烟气中PAHs毒性当量(TEQ)远大于灰渣;在保证煤完全燃烧的情况下,综合考虑对烟气和灰渣中PAHs生成总量以及毒性当量TEQ的控制,燃烧条件为温度为850℃,α=1.57时,PAHs对环境的影响较小。     

紫外光激活过硫酸盐降解硫氰根研究

为探明不同条件下的紫外光(UV)激活过硫酸盐(PS)降解硫氰根(SCN~-)的情况,在SCN~-质量浓度为100mg/L、温度30℃条件下分别研究了辐照度、pH、S_2O_8~(2-)含量对SCN~-降解效果的影响,并对反应产物和机理进行了分析。结果表明,SCN~-的降解率随光照强度的增大而增大,辐照度9.94 m W/cm~2时SCN~-降解率最大;随S_2O_8~(2-)含量的增加而增大,S_2O_8~(2-)浓度大于4 mmol/L后,SCN~-降解率变化缓慢;出水中残余的TOC含量随着S_2O_8~(2-)含量的增加而降低,S_2O_8~(2-)浓度4.5 mmol/L时最低;随着pH的增加SCN~-降解率在pH为5处达到最大;pH为11时出水中残余的CN~-的质量浓度为0.156 mg/L,达到GB 16171-2012排放标准。UV激活PS降解SCN~-过程中可能的反应历程为:硫元素首先被除去,转变成SO_4~(2-),而氮元素则主要转变为CN~-和NH_4~+-N。     

海产养殖常用药物三氯异氰尿酸的光化学降解行为

[目的]含氯杀菌剂是渔业生产中广为应用的水体消毒药剂,光化学降解是其在水中分解的主要途径和速率限制步骤之一。研究典型海产养殖药物的光化学降解行为,有助于保证其施用效果及降低海产品农残。选择海产养殖常用药物三氯异氰尿酸(TCCA),在不同的光照强度下测定其反应速率。选择较优的光照条件,在不同的pH值、不同的温度条件下,通过离子色谱法对水中各时间段的氯离子浓度进行测定,研究其水中光化学降解行为。[结果]不同的光照强度和条件下,TCCA中氯离子解离速度变化较为明显,且解离速度随波长的增加而减小。紫外光照射条件下,酸性溶液抑制解离,碱性溶液促进解离;温度升高有利于药物的降解。TCCA的降解基本符合一级动力学,且时段不同反应速率常数不同。[结论]水产养殖的用药杀菌过程中,应该尽量使水质保持中性。对于海产养殖而言,由于通常情况下海水的pH值显弱碱性,所以在使用药物时应尽量在晴天使用,此时的光照效果及紫外强度均较大,这样既能使药物完全发挥效果也会使药物尽快解离。     

水解锌纳米结构对甲基橙的光催化降解

利用滚压振动磨在干法室温条件下将金属锌制备成为尺度大约在3～5 nm的锌量子点,并使产物与水蒸气在不同温度下进行化学反应,得到纳米氧化锌或纳米氧化锌与锌的混合物。在250℃反应温度下得到的产物具有最好的分散性,其特征是棒状和片状结构共存,而且纳米棒具有显著的沿着［0,1,-1,1］晶向的生长趋势。在几个不同水解温度得到的产物中,这种纳米结构对甲基橙的光催化降解效率最高,在距离30 cm的30W紫外灯照射下,在30 min内降解了95%,1 h则几乎完全降解。而在阳光照射下,15 min内甲基橙的衰减率就达到95%,30 min则几乎完全降解。这种优异的催化性能主要归功于产物的特殊结构和形貌,为提高金属及其氧化物纳米结构对有机染料的降解提供了一条新途径。     

高能紫外光降解硫化天然橡胶降解能力及降解机理的研究

采用高能紫外光反应容器,研究了硫化天然橡胶的光降解过程。通过溶胶凝胶含量、GPC、核磁共振氢谱,表征硫化天然橡胶降解程度以及溶胶分子结构,通过红外光谱、接触角、元素分析表征硫化天然橡胶紫外光降解机理。结果表明,硫化天然橡胶在高能紫外光照射下能够快速降解,溶胶含量随照射时间增加而增加,溶胶分子量随照射时间增大而减小。紫外光照射过程中氧气参与紫外光降解过程,使得硫化天然胶主链发生断裂,导致降解产物含有含氧基团,亲水性及氧原子数目增加,但随着照射时间的增加含氧基团继续在紫外光作用下发生反应,导致含氧基团减少,亲水性下降。     

韩家湾煤及其热解半焦中多环芳烃分布特征研究

低阶煤的热解是其深加工工艺的基础，为探究其固体产物半焦中多环芳烃(PAHs)的含量水平及组成特征，以陕西榆林韩家湾次烟煤及其不同温度条件下(350℃～700℃)生成的热解半焦为样品，采用溶剂萃取结合GC/MS方法分析其中PAHs分布特征。结果显示：韩家湾原煤中16种优控母体(美国环保署规定)PAHs含量(∑16PAHs, 15 161 ng/g)低于对应烷基取代PAHs含量(∑aPAHs, 24 055 ng/g),380℃热解半焦中∑16PAHs(19 003 ng/g)和∑aPAHs(45 009 ng/g)均呈极大值；半焦中∑16PAHs和∑aPAHs随温度呈先增后降的变化趋势，但aPAHs含量随热解温度变化的幅度大于16PAHs含量变化的幅度，推测热解过程释放的PAHs可能以aPAHs为主；16PAHs组成上，原煤以4环母体PAHs为主,半焦中则以2～3环PAHs为主；350℃～400℃热解半焦中萘和烷基萘含量显著高于原煤中相应成分的含量，表明煤在低温热解时发生裂解反应并生成大量萘系物。     

Protective space coatings: a ceramer approach for nanoscale materials

There is a concerted and focused push to develop protective space coatings for vehicles in low earth and geosynchronous orbit. The space environment is not suitable for organic materials due to atomic oxygen, high energy particles, and deep UV light being able to degrade polymeric organic resins. An inorganic/organic hybrid coating, known as a ceramer, will be fabricated using a polysiloxane binder and nanophase silicon/metal-oxo-clusters derived from sol–gel precursors. The binder of the coating will be a substituted polysiloxane terminated with a cyclohexyl epoxide. The cyclohexyl epoxide will be cured at ambient temperature via a cationic UV curing mechanism. PDSC will also be used to investigate the effects of temperature, UV light intensity, sol–gel precursor concentration, and exposure time have on the rate of polymerization. Nuclear magnetic resonance and Fourier transform infrared spectroscopy were used to characterize the synthesis of the polysiloxanes. The rate of polymerization was found to increase as temperature, intensity, sol–gel precursor concentration, and exposure time were increased.     

A Facile Method for the Synthesis of a MoS2/g‐C3N4 Photocatalyst

A MoS₂/g‐C₃N₄ composite was synthesized by a significantly simple method using Na₂MoO₄ and thiourea as precursors, without the need for a hydrothermal or an ultrasound step. The photocatalytic activity of the synthesized material was evaluated by the degradation of rhodamine B (RhB) in aqueous solution under blue light. The composites with low content of MoS₂ performed better than pure g‐C₃N₄. Using a low‐power light‐emitting diode light source, an improvement of two orders of magnitude in the photochemical space‐time yield was achieved, proving enhanced energy efficiency and productivity compared to earlier studies. The degradation pathway of organic pollutants was confirmed by the effects of selective scavengers.     

阿维菌素光化学降解研究及其光稳定剂的筛选

研究了光源波长、光照强度以及阿维菌素初始浓度对其光降解的影响,并系统考察了紫外吸收剂阿凡达、抗氧化剂BHT、光屏蔽剂纳米SiO_2和表面活性剂十二烷基硫酸钠对阿维菌素光降解的影响。结果表明:光源波长越短,光照强度越大,初始浓度越低,则阿维菌素的光解速率越高。紫外吸收剂、抗氧化剂及光屏蔽剂对阿维菌素光降解有显著抑制作用。     

新型光化学反应器及二氧化碳光解反应研究

研究设计了可产生波长小于200 nm真空紫外光的光化学反应器,首次利用该波段的光在该反应器中进行了CO2光解反应的研究。用氮气为发光介质对其进行光强标定,实验表明主要产生120、149、174 nm波长的光(N原子谱线);实验条件下CO2光解后生成产物CO,结果表明光源电流一定时产生CO的量与光源工作气体的压力有关,在CO2和N2反应物系中,光源内发光介质N2的压力在2 500 Pa左右时CO的产率最大,而在该反应物系中加入甲烷后,CO的产率明显增大。     

Modeling of an external light irradiation slurry photoreactor: UV light or sunlight-photoassisted Fenton discoloration of azo-dye Orange II with natural mineral tourmaline powder

A model for design and scale-up of an external light irradiation slurry photoreactor was developed on the basis of a model for the average light intensity in the photoreactor. In order to assess the design parameters in the proposed model, experiments for UV light or sunlight-photoassisted Fenton discoloration of azo-dye Orange II in water with iron ion eluted from the natural mineral tourmaline powder containing 4.49 wt% Fe₂O₃ were conducted using an external light irradiation cylindrical column photoreactor. The efficiency of discoloration increased as initial Orange II concentration decreased and the tourmaline concentration and UV light intensity increased. It was found that the optimal hydrogen peroxide concentration and pH are and 3, respectively. The proposed model, in which the change of light intensity with degradation time due to the discoloration of Orange II and the light scatter due to solid photocatalysts are taken into account, could simulate the experimental results both for UV light and sunlight irradiation conditions reasonably well. The model is applicable commonly both for UV light and sunlight irradiation. The results will be very useful for designing slurry photoreactors in the treatment of textile effluents.     

光照强度及温度对青草沙水库蓝藻暴发风险的模拟试验

青草沙水源地正成为上海市新兴的重要水源地,其水源安全直接影响地区安全和发展,蓝藻暴发[1-3]是危害其水源安全的重要方面。以长江中下游地区常见的铜绿微囊藻、四尾栅藻作为试验藻种,选择光照强度、温度为影响因子,设计不同因素水平进行室内单因素模拟试验和原水稳态模拟试验,并结合青草沙水库实际水质水文条件进行分析,以寻找该地区蓝藻生长的优势条件。结果表明铜绿微囊藻比四尾栅藻对温度变化更敏感;铜绿微囊藻在低光照下有较高的适应性和较高的比增殖速率,四尾栅藻对强光照更为敏感;在3 300~6 600 lux、24℃的青草沙原水中,铜绿微囊藻倍增周期为20 d左右,对温度变化较光照变化更敏感。应加强青草沙水库库首、滞水区等局部水域水质监测,并据此及时提出预警和防范措施,同时应在夏季预期有持续高温晴天出现时提高预警级别,防范持续日照增长后蓝藻暴发。     

调理剂对污泥生物减水的影响

采用自主研发的发酵罐污泥生物减水装置,以稻草、木屑为碳源调理剂,研究不同碳源调理剂种类和配比对堆体温度、含水率的影响。试验结果表明,以稻草为碳源调理剂的堆体升温速率最快,50℃高温保持时间在5d以上,含水率可降至50％以下;稻草的用量越大,堆体升温速率越大,高温保持时间越长,含水率越低,最佳物料配比为污泥、稻草、木屑、回料质量比为1：0．1：0．05：0.3。稻草是污泥生物减水比较合适的碳源调理剂．木屑不适合作为碳源调理剂,但木屑可以作为延长高温期时间的调理剂。     

Microbial Degradation of High Molecular Weight Polycyclic Aromatic Hydrocarbons with Emphasis on Pyrene

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) is a major concern in the environment due to their toxic nature and ubiquitous occurrence. PAHs remain sorbed to soil organics and interact with non-aqueous phases and therefore, become less available for degradation. Several microorganisms like bacteria, fungi, and algae have the capability to degrade soil-sorbed PAHs using different metabolic pathways. The focus of this review is microbial degradation of high molecular weight PAH pyrene by pure and mixed culture, including biological aspects of biosurfactants produced during the process for increasing the bioavailability of soil-sorbed or non-aqueous phase pyrene. High molecular weight PAHs are generally recalcitrant to microbial attack, although some bacteria, fungi, and algae are capable of transforming these compounds by using them as the sole source of carbon and energy. Also, the use of microbial consortium has been found to be more efficient and better from an economic point of view for degradation due to synergistic interactions among microbial species. The review also explains the role of catabolic genes involved in the degradation of pyrene.     

Photostability of organic materials used in polymer solar cells

To make polymer solar cells (PSCs) a competitive market technology, integrated efforts are required toward the development of highly efficient light harvesting and charge transporting materials with good thermal and photochemical stability, and which can be processed from solution. Nowadays, a critical issue to be solved is enhancing the stability and durability of PSCs. Indeed, the photoactive material used in the active layer dictates the efficiency of the device on the one hand but, on the other hand, it is well known that organic materials are unstable when exposed to light irradiation, which provokes a degradation of their properties. Making long lifetime solar cells with polymers that are susceptible to degradation under light exposure could be an unrealistic challenge. Therefore, elucidating the mechanism of polymer photodegradation is a key point for developing strategies to decrease or prevent the loss of the functional properties of the material. In this paper, the basic concepts of polymer photo‐aging are explained first. Then the photodegradation mechanisms of conjugated polymers currently used in PSCs are reported. Finally, as barrier materials able to cut off moisture and oxygen ingress are essential for the stability of PSCs, methods for designing coatings for PSC encapsulation are presented, based on recent publications. © 2013 Society of Chemical Industry     

Study of special cases where the enhanced photocatalytic activities of Pt/TiO2 vanish under low light intensity

Surface platinized TiO₂ (Pt/TiO₂) has been widely used and investigated but their properties are yet to be understood fully. Although it is known that the Pt effects depend on many experimental parameters and the kind of substrates, this study newly finds that the Pt effects could be also influenced by the light intensity. As for the photocatalytic degradation of trichloroethylene (TCE), the Pt effect was positive at high light intensity but was negative at low light intensity. A similar behavior was also observed in the photocurrent collection in the Pt/TiO₂ suspension with polyoxometalate (POM: PW₁₂O₄₀³⁻) used as an electron shuttle. The photocurrent collection in the Pt/TiO₂ suspension was less efficient than in TiO₂ suspension when the light intensity was low. Such abnormal light intensity-dependent behaviors were not observed in the photocatalytic degradation of dichloroacetate on Pt/TiO₂ and the Fe³⁺-mediated photocurrent collection in the Pt/TiO₂ suspension. It is proposed that the photochemical interactions between the Pt surface and reactive intermediates (TCE radical anions and reduced POM anions) induce a null reaction favorably at low light intensity condition.