无皂乳液聚合改性废聚苯乙烯

以聚(甲基丙烯酸丁酯—丙烯酸钠)(P (BMA- AANa))为乳化剂,采用无皂乳液聚合技术,利用BMA对废聚苯乙烯(PS)泡沫塑料进行接枝改性.实验得出适宜的工艺条件:P(BMA - AANa)质量分数为51.5％,m(BMA)∶m(丙烯酸)=4∶6,PS和BMA质量分数之和为10.0％;m(PS)∶m(BMA) =...     

How do different process options and evaluation settings affect economic and environmental assessments? A case study on methyl methacrylate (MMA) production processes

We present an investigation on how economic and environmental assessment results change when different process options or evaluation settings are considered. As the main case study the production technology of methyl methacrylate (MMA) is investigated. Six commercial processes using different reaction routes are modelled and evaluated with respect to their economic and environmental performance. On these six base case models different process options and evaluation settings are considered and the resulting impacts on the assessment results are quantified. Major findings of the study are that the more decision-variables become fixed, the smaller becomes the impact of the decisions still to be taken—but not only with respect to the economic performance but also with regard to the environmental assessment result. Along the process development steps the potential impacts on the economic and environmental performance decrease to the same degree. The results obtained for the evaluation settings do not show such a systematic pattern as those for the process options. This finding indicates that decision makers face many options in the economic and especially the environmental assessment of chemical processes which might lead to quite different magnitudes in variability due to either the choice of method or the choice of method parameters. This paper demonstrates that the resulting variability might be crucial with respect to the decision making outcome.     

气相色谱法测定空气中丙烯酸酯

讨论了用气相色谱仪测定被污染空气中丙烯酸甲酯、丙烯酸乙酯、甲基丙烯酸甲酯、丙烯酸丁酯的方法条件。方法检出下限在６ｎｇ范围,相对标准偏差为１４～６９％,回收率为９０６～１１０５％。实验还显示丙烯酸酯污染空气问题不容忽视。     

铅锌硫化矿浮选废水及尾矿库外排水中VOSCs的组成特征及其来源解析

利用臭氧氧化技术对铅锌硫化矿浮选过程各单元作业废水及尾矿库外排水进行处理,根据硫酸根离子浓度增量计算废水中低价态硫(价态小于+6)浓度.采用吹扫捕集-气相色谱质谱联用仪(PTC-GC/MS)检测浮选药剂(丁基二硫代碳酸钠(n-BX)、二乙基二硫代氨基甲酸钠(DDTC)、腐殖酸钠(SH)、松醇油)水溶液的自然降解产物、尾矿库进水及外排水中的挥发性有机硫化物(VOSCs).结果表明,尾矿库主要进水水源中低价态硫浓度为112 mg·L-1,其中,二硫化碳(CS2)在检测组分中所占相对比例为35.60%,是主要的VOSCs物质.各单元作业中浮选作业工段加入大量浮选药剂,浮选药剂水溶液自然降解产物中均检出CS2,而用药量最大的n-BX(C5H9Na OS2)自然降解产物中CS2相对比例最高(80.33%),因此,n-BX是浮选废水中VOSCs主要药剂来源.尾矿库外排水中低价态硫浓度为22 mg·L-1,其中,VOSCs物质主要有3,6-二甲基-1,2,4,5-四硫环己烷(C2H4S4)、N-巯基-甲酰胺(CH2SNO)和2-甲基-3-噻唑啉(C4H7NS),尾矿库外排水中C2H4S4所占相对比例为22.59%,是主要VOSCs物质.尾矿库水体中微生物通过消耗CS2生成C2H4S4进行新陈代谢.本研究结果可为铅锌硫化矿浮选工艺改进和安全排放提供参考.     

多胺改性PGMA-DAAM树脂的合成及对Pb2+的吸附性能

甲基丙烯酸缩水甘油酯(GMA)与双丙酮丙烯酰胺(DAAM)发生共聚,生成一种含环氧基和DAAM亲水链节的PGMA-DAAM共聚物,再与三乙烯四胺反应,合成了一种多胺改性的PGMA-DAAM树脂(TETA-PGMA-DAAM)。树脂的结构经元素分析、红外光谱和热重分析进行表征。探讨了合成树脂对Pb2+的吸附性能,考察了吸附温度、pH、金属离子浓度等因素对吸附效果的影响。结果表明,树脂对Pb2+的吸附量随着温度的升高而略有增大,在pH约为4.7、温度为40℃和Pb2+平衡浓度为0.01299 mol/L时其最高吸附量可达到1.581 mmol/g。树脂对Pb2+的吸附符合Boyd模型,表现为液膜扩散控制,其扩散系数在30℃和35℃时分别为0.0131 min-1和0.0175 min-1。吸附过程符合Langmuir和Freundlich等温吸附式。吸附热力学参数ΔG,ΔH和ΔS分别为-3.912 kJ/mol(25℃)、2.058 kJ/mol和20.025 J/mol,表明吸附过程为自发进行的吸热过程。     

脉冲电强化微电解对铅锌浮选废水中锌和丁基黄药的去除

研究了脉冲电强化微电解流化床技术去除铅锌浮选废水中的锌及丁基黄药,考察不同溶液初始pH值和反应器中不同电流密度、脉冲周期及极板间距对模拟废水中锌和丁基黄药的去除效果,采用扫描电镜(SEM)和X射线衍射能谱仪(XRD)进行填料表面特征、物相和形态分析,并对废水中锌和丁基黄药的去除过程和降解途径进行探究。结果表明,在pH值为4、电流密度为20 mA·cm-2、脉冲周期为2 s、极板间距为5 mm的最佳条件下,废水中锌和丁基黄药去除率分别达99.53%和99.03%。锌主要通过电催化还原沉积和铁羟基聚合物絮凝去除,而丁基黄药则被体系电催化原位生成的H2O2、羟基自由基氧化降解矿化,以及铁羟基聚合物絮凝去除。     

基于O3/AC耦合工艺对丁基黄药与COD的同步去除性能及降解机理

针对臭氧氧化技术处理含丁基黄药废水COD去除率低等问题,提出了O₃/AC耦合工艺。在探讨单独、耦合工艺的丁基黄药去除率和COD去除率、反应影响因素和降解路径的基础上,进一步发掘该耦合工艺对丁基黄药及COD的同步去除性能。结果表明：臭氧(O₃)及活性炭(AC)的单独作用均对丁基黄药或COD有一定的去除效果,通过O₃/AC的耦合作用则可使丁基黄药的去除率达99.9%,亦使COD的去除率由O₃单独作用下的42.9%显著提升至77.2%,且实现最高去除率的时间由AC单独处理所需的80 min缩减至30~40 min;拟一级反应动力学分析结果表明,丁基黄药的反应速率常数表现为$k{_\text{(O3/AC)}}$>$k{_\text{O3}}$>k_AC,COD的反应速率常数表现为$k{_\text{(O3/AC)}}$>k_AC>$k{_\text{O3}}$,O₃/AC耦合工艺去除丁基黄药及COD的反应速率常数均大于两种单独处理工艺;紫外-可见(UV-vis)光谱分析表明丁基黄药在O₃、O₃/AC作用下生成中间有机产物,结合GC-MS对产物的鉴定结果表明其中间有机产物可能为丁酸等物质,并以此对O₃/AC耦合工艺同步去除丁基黄药及COD的降解路径进行了初步推测。     

Probe into effect of the initiator on the thermal runaway hazards of methyl methacrylate bulk polymerization

The bulk polymerization of methyl methacrylate (MMA) is of great importance in chemical industry, but the polymerization process is highly hazardous, and few reports have focused on the effect of initiators on its thermal hazards. In this work, to thoroughly explore the thermal hazard characteristics, the runaway behavior of MMA bulk polymerization is investigated by a combination of thermodynamics experimental and kinetics theoretical methods. The results indicate that the presence of initiator exhibits an undesirable thermal hazard to the MMA bulk polymerization, and its exothermic behavior is also greatly influenced by the type and concentration of initiator. For azobisisoheptanenitrile (ABVN), azodiisobutyronitrile (AIBN) and dibenzoyl peroxide (BPO) initiators as examples, the AIBN-initiated reaction has the shortest adiabatic induction period (39.51 min), whereas the BPO-initiated polymerization exhibits the strongest maximum temperature-rising rate and maximum pressure-rising rate. Under adiabatic runaway, the temperature and pressure change significantly with increasing AIBN concentration, revealing a great potential risk of thermal runaway. Kinetic parameters are calculated to further understand the thermal runaway mechanisms, showing a strong agreement with the adiabatic experimental data. Finally, based on the cooling failure scenario, severity grading is determined by the evaluation criteria. The current work provides extensive data as a reference and guidance for the process design and optimization of MMA bulk polymerization from the perspective of safety.     

丁铵黑药在水稻土中的降解及其影响因素研究

通过室内模拟实验,探讨了水稻土中丁铵黑药的降解规律及影响因素.结果表明,水稻土中丁铵黑药的降解率随着初始浓度的增大而降低,其半衰期均小于4d.丁铵黑药的降解率在一定范围内随着土壤含水量和温度的升高而显著提高,当含水量为60%、温度为25℃时,培养7d内丁铵黑药的最高降解率达84%.水稻土中丁铵黑药的降解机制主要是微生物的降解作用(约占80%),其次是光降解作用(约占20%).     

包覆型纳米铁的制备及其去除三氯乙烯的研究

采用微乳聚合法成功的用聚甲基丙烯酸甲脂(PMMA)包覆了纳米铁粒子.透射电镜、红外光谱和热重分析证明,PMMA包覆层存在于铁表面,包覆型纳米铁在空气中的稳定性明显提高.批次实验结果表明,该纳米材料能有效降解环境污染物三氯乙烯(TCE),包覆型纳米铁对TCE的还原反应符合准一级反应动力学.