TG-DSC and FTIR study on pyrolysis of irradiation cross-linked polyethylene

Irradiation cross-linked polyethylene (PEX) and irradiation cross-linked polyethylene with carbon black filler (CB-PEX) are two types of scraps, generated in electric cable production. Their pyrolysis is studied in this work using instrumental TG\DSC\FTIR techniques and kinetic analysis. The experiments are performed at a constant heating rate of 10 °C/min in nitrogen flow at atmospheric pressure. It is found that the main pyrolysis stage is in the temperature range of 395–503 °C for PEX, and in range of 408–515 °C for CB-PEX. In the main pyrolysis stage, CB-PEX requires more external heat than PEX does. Olefins are the major products of pyrolysis for both materials, but they are quite different in their composition and molecular weight distribution. PEX can be converted almost quantitatively into volatile compounds. CB-PEX has a stronger coking tendency, as well as a larger residue composed of carbon black.     

Heterogeneous reactions of suspended parathion, malathion, and fenthion particles with NO(3) radicals

Organophosphorus pesticides (OPPs) emit into the atmosphere in both gas and particulate phases via spray drift from treatments and post-application emission, but most of their degradations in the atmosphere are not well known. In this study, the heterogeneous reactions of nitrate (NO₃) radicals with three typical OPPs (parathion, malathion, and fenthion) absorbed on azelaic acid particles are investigated using an online vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). The reaction products observed with the VUV-ATOFMS are identified on the basis of GC/MS analysis of the products in the reaction between NO₃ radicals and the coating of the pesticide. Paraoxon is identified as the only product of parathion; malaoxon and bis(1,2-bis-ethoxycarbonylethyl)disulfide as the products of malathion; fenoxon, fenoxon sulfoxide, fenthion sulfoxide, fenoxon sulfone, and fenthion sulfone as the products of fenthion. The degradation rates of parathion, malathion, and fenthion under the experimental conditions are 5.5 × 10⁻³, 5.6 × 10⁻², and 3.3 × 10⁻² s⁻¹, respectively. The pathways of the heterogeneous reactions between the three OPPs and NO₃ radicals are proposed. The experimental results reveal the possible transformations of these OPPs through the oxidation of NO₃ radicals in the atmosphere.     

Pathways of reductive degradation of crystal violet in wastewater using free-strain Burkholderia vietnamiensis C09V

A new strain isolated from activated sludge and identified as Burkholderia vietnamiensis C09V was used to biodegrade crystal violet (CV) from aqueous solution. To understand the degradation pathways of CV, batch experiments showed that the degradation using B. vietnamiensis C09V significantly depended on conditions such as pH, initial dye concentration and media components, carbon and nitrogen sources. Acceleration in the biodegradation of CV was observed in presence of metal ions such as Cd and Mn. More than 98.86C of CV (30 mg l^?1) was degraded within 42 h at pH 5 and 30 °C. The biodegradation kinetics of CV corresponded to the pseudo first-order rate model with a rate constant of 0.046 h^?1. UV–visible and Fourier transform infrared spectroscopy (FTIR) were used to identify degradation metabolites. Which further confirmed by LC-MS analysis, indicating that CV was biodegraded to N,N-dimethylaminophenol and Michler’s ketone prior to these intermediates being further degraded. Finally, the ability of B. vietnamiensis C09V to remove CV in wastewater was demonstrated.     

硫铁矿废水处理污泥制备聚合硫酸铁铝

探讨了以硫铁矿废水处理污泥为原料制备聚合硫酸铁铝的可行性,确定酸溶提取-离心分离-氧化聚合制备聚合硫酸铁铝的工艺流程。用硫铁矿废水与浓硫酸的混合液(体积比9∶1)提取污泥中铁铝元素,在混合液与干污泥的体积质量比3.4∶1,酸溶时间15 min的条件下,污泥中铁的提取效果较好。离心分离后的污泥提取液,经过氧化聚合制备聚合硫酸铁铝。结果表明,在反应溶液初始pH 0.9,反应温度40℃,反应时间2 h,氧化剂投加量为理论投加量2倍的条件下,制备得到的聚合硫酸铁铝质量最好;对印染废水的混凝沉淀实验发现其混凝沉淀效果已达到市售聚合硫酸铁铝水平。     

汶川县映秀镇红椿沟特大型泥石流形成机制及堵江机理研究

2010年8月14日,汶川县映秀镇红椿沟因连日强降雨,发生灾害性特大泥石流,完全中断都汶公路的交通,并冲入岷江形成堰塞体,致使河水改道,冲进映秀新区使数十幢房屋成为孤岛,严重危胁到灾后重建的胜利成果。研究红椿沟泥石流的基本特征、变形破坏机制、类型规模及防治对策,对防治高地震烈度泥石流灾害、确保灾后重建成果具有重要意义。以红椿沟特大型泥石流为例,在研究地质灾害形成的地质背景及条件、基本特征的基础上,分析了泥石流的形成机理及断路堵江的具体原因,预测了泥石流发展的趋势,对重要物源点进行了稳定性分析,提出了红椿沟泥石流的形成及堵江除丰富的震后松散物源、强降雨外,还与其独特的地形地貌密切相关。研究表明,红椿沟特大泥石流是从其上游甘溪铺支沟开始启动、汇集溃决,随后带动主沟物源冲入岷江,与岷江上游烧房沟泥石流冲入江中物质在江中汇集,形成堵江。红椿沟内物源丰富,必须加强防治,防止泥石流的再次危害。     

复合絮凝剂APAC中铝形态分布及絮凝性能研究

用慢速滴碱法合成聚合氯化铝的过程中加入酸改性的凹凸棒,制备了新型絮凝剂APAC。采用Al-Ferron逐时络合比色法和烧杯絮凝实验法分别研究了APAC复合絮凝剂中铝的形态分布和絮凝性能。结果表明,Ala随盐基度的升高而逐渐降低;Alb随盐基度的升高而升高;Alc则先随盐基度的升高而升高,达到最大值后,再随盐基度的升高而降低。在相同实验条件下,盐基度愈高,混凝效果愈好,Alb含量愈高,混凝效果并不一定愈好。因此,APAC的质量控制以及追求目标应当是尽量提高Alc的含量,而不是Alb的含量。     

Palm Oleic Acid Based Alkyds: Effect of the Fatty Acid Content on the Polyesterification Kinetics

The kinetic behavior of polyesterification of the alkyd resins synthesized using glycerol and phthalic anhydride modified with oleic acid from the palm oil at temperatures between 120 and 240 °C was studied. Three alkyds having oleic acid contents of 28, 40, and 65% were prepared by employing fatty acid method. The extent of the polyesterification reaction and average degree of polymerization were monitored by determining the acid number of the aliquot of the reaction mixture at various intervals of time and by measuring the volume of water evolved. Kinetic studies revealed that initial reaction rates followed a second-order kinetics up to certain limit and thereafter deviations were observed. The extent of reaction varied from 77.4 to 86.3% before deviation for all the three samples and exhibited a considerable degree of conversion. The second-order rate constants calculated from the linear part were found to be of the order of 10⁻⁵ g (mg KOH)⁻¹ min⁻¹. Molecular weight of the alkyd samples was determined by GPC; number average molecular weight of the alkyds ranged from 980 to 2,070.     

Oxidation of bisphenol F (BPF) by manganese dioxide

Bisphenol F (BPF), an environmental estrogen, is used as a monomer in plastic industry and its environmental fate and decontamination are emerging concern. This study focused on the kinetics, influencing factors and pathways of its oxidation by MnO₂. At pH 5.5, about 90% of BPF was oxidized in 20 min in a solution containing 100 μM MnO₂ and 4.4 μM BPF. The reaction was pH-dependent, following an order of pH 4.5 > pH 5.5 > pH 8.6 > pH 7.5 > pH 6.5 > pH 9.6. Humic acids inhibited the reaction at low (≤pH 5.5) and high pH (≥pH 8.6) at high concentrations. In addition, metal ions and anions also suppressed the reaction, following the order Mn²⁺ > Ca²⁺ > Mg²⁺ > Na⁺ and HPO₄²⁻ > Cl⁻ > NO₃⁻ ≈ SO₄²⁻, respectively. A total of 5 products were identified, from which a tentative pathway was proposed.     

页岩气开采水力压裂返排水中化学污染物的组成特征

伴随全球页岩气规模化开发,相关的区域环境问题引起了学界和公众的持续关注.页岩气开采与区域水资源息息相关,水力压裂不仅消耗大量水资源,而且产生返排废水,成分复杂,含数以千计的化学物质.因此,有关返排水中有机单体的相关研究越来越受关注.本文系统总结了近年来的相关文献和成果,重点论述了压裂返排水中有机污染物的来源、种类、浓度...     

扬中水体氮素转化规律及其影响因素

本文选用扬中县江、河、塘泥,进行了实验室模拟试验,得出了这三种水体氮素的转化规律及其影响因素。结果表明,底泥的性质、水温及pH、溶解氧和藻类的生长,对氮素转化都有一定的影响。底泥速效氮含量(x)与水体氮素转化速度常数(k)呈正相关。Arrhenius活化能△E=52815.67(J/mol)。水中pH中性和微碱性、溶解氧含量高以及良好的藻类生长,均有利于硝化作用的进行。