氨水混合吸收剂脱除CO2实验研究

氨水作为一种很有应用前景的CO2化学吸收剂,存在吸收速率慢的问题.使用湿壁塔实验台,考察了不同种类的添加剂(MEA、PZ、1-MPZ、2-MPZ)对氨水吸收CO2速率的影响.结果表明,4种添加剂均能明显提高氨水吸收CO2的速率,其中PZ具有最好的促进效果.0、0.1、0.3和0.5 mol·mol-1负荷下,3 mol·L-1NH3+0.3 mol·L-1PZ溶液的总传质系数(KG)分别是3 mol·L-1NH3溶液在相应负荷下的3、3.2、3.2和2.9倍.改变反应温度、添加剂量、PZ浓度等条件对基于NH3/PZ混合吸收剂吸收CO2的反应过程进行实验,得到了其在不同条件下的KG,初步探讨CO2吸收的反应机制,并计算出准一级反应速率常数为42.7 m3·(mol·s)-1.     

吸收CO2新型混合化学吸收剂的研究

以吸收剂吸收速率和再生程度为指标,在小型实验装置台上研究了3种混合吸收剂不同配比的吸收和再生特性,以确定其吸收剂主体和添加剂的合适配比.结果表明,在甲基二乙醇胺(MDEA)中添加哌嗪(PZ),当混合吸收液CO2负荷为0.2 mol·mol-1时,MDEA∶PZ=1∶0.4(m∶m)混合液CO2吸收速率比MDEA∶PZ=1∶0.2(m∶m)混合液提高了约70%.再生40 min,PZ 相对浓度为0的吸收液再生程度为91.04%,PZ相对浓度为0.2、0.4和0.8时,混合吸收液的再生程度分别降低为83.06%、77.77%和76.67%.综合比较,MDEA∶PZ=1∶0.4(m∶m)是该混合吸收液合适的配比,吸收速率和再生特性都有较好改善.在10%一级胺中添加2%三级胺既能保持高吸收效率,又能略微降低再生能耗.在10%二乙醇胺(DEA)中加入2%2-氨基-2-甲基-1-丙醇(AMP),混合液表现出DEA/AMP混合吸收剂中较好的吸收和再生特性.3种配方中,在一级胺中添加少量三级胺吸收速率最高,二级胺和少量空间位阻胺混合吸收剂的再生性能最好.而综合吸收和再生2个指标,三级胺和中量活化剂的混合液有优势.     

MDEA-TETA混合液捕集电厂烟气中CO2的实验研究

分别以MDEA溶液和MDEA-TETA混合液为吸收剂对电厂烟气中的CO_2进行捕集.在相同的实验条件下,研究了吸收时间、吸收液浓度配比和反应温度对CO_2吸收率的影响,并对两种吸收剂的吸收效果进行对比分析.结果表明:吸收效率随着温度的升高而下降,温度低于45℃时,混胺吸收剂MDEA-TETA的吸收效率受温度的影响显著,温度高于45℃时,单一吸收剂MDEA的活化性能大幅度增强.MDEA-TETA混合液中两种胺的配比为6∶1,反应温度在25~65℃内,反应时间在5~20 min内时CO_2的吸收效果较佳,吸收率达90%以上,不同配比的混胺吸收剂的吸收效果均优于MDEA的吸收效果.     

气液膜接触器分离混合气中CO_2过程研究

建立了膜接触器吸收CO2 ,溶液热再生连续循环实验装置 ,评价了疏水性PP(聚丙烯 )微孔膜 ,MDEA(N 甲基二乙醇胺 )溶液及添加活化剂PZ(哌嗪 )的活化MDEA溶液吸收CO2 传质过程。结果表明 :在溶液浓度 2 5mol L ,气速0 5～ 3 0L min,液速 15～ 15 0mL min时 ,总传质系数Kov为 1 0× 10 - 5～ 3 6× 10 - 5m s(MDEA) ,1 6× 10 - 5～ 4 5×10 - 5m s(MDEA +PZ)。采用阻力层无因次关联方程模型预测Kov值 ,计算值和实验值符合较好。基于模型和实验结果 ,将PZ的吸收行为作为溶液的活化作用 ,在计算Kov值时 ,考虑活化作用因素并归结于化学增强因子E中 ,模型能更好地预测实验结果。实验证明在单一醇胺组份MDEA中添加少量PZ能提高总传质系数Kov值     

吸收CO2新型混合化学吸收剂的研究

以吸收剂吸收速率和再生程度为指标,在小型实验装置台上研究了3种混合吸收剂不同配比的吸收和再生特性,以确定其吸收剂主体和添加剂的合适配比.结果表明,在甲基二乙醇胺（MDEA）中添加哌嗪（PZ）,当混合吸收液CO₂负荷为0 .2 mol·mol^-1时,MDEA∶PZ=1∶0 .4（m∶m）混合液CO₂吸收速率比MDEA∶PZ=1∶0 .2（m∶m）混合液提高了约70％.再生40 min,PZ相对浓度为0的吸收液再生程度为91 .04％,PZ相对浓度为0 .2、0 .4和0 .8时,混合吸收液的再生程度分别降低为83 .06％、77 .77％和76 .67％.综合比较,MDEA∶PZ=1∶0 .4（m∶m）是该混合吸收液合适的配比,吸收速率和再生特性都有较好改善.在10％一级胺中添加2%三级胺既能保持高吸收效率,又能略微降低再生能耗.在10％二乙醇胺（DEA）中加入2％ 2-氨基-2-甲基-1-丙醇（AMP）,混合液表现出DEA/AMP混合吸收剂中较好的吸收和再生特性.3种配方中,在一级胺中添加少量三级胺吸收速率最高,二级胺和少量空间位阻胺混合吸收剂的再生性能最好.而综合吸收和再生2个指标,三级胺和中量活化剂的混合液有优势.     

喷雾塔中氨水吸收CO2的速率

为考察氨水细喷雾吸收CO2的能力,对喷雾塔中氨水细喷雾吸收CO2的反应过程进行了实验研究,测定了氨水吸收CO2的速率.实验结果表明,CO2的吸收速率随着氨水浓度、气体流量的升高而明显增大,随氨水流量升高也有所增加,CO2的吸收速率随CO2进口浓度的升高呈线性增加.当喷雾塔中温度低于40℃时,CO2的吸收速率随着塔内温度...     

负载量对氨水吸收CO2的影响规律及添加剂的作用研究

进行了氨法脱碳过程中吸收剂中CO2负载量对CO2脱除率影响的实验研究.结果发现,CO2脱除率随着负载量的增大而显著减小,高负载量(≥0.4)时,增加吸收液中总氨质量分数(吸收液中所有包含氨分子和铵离子的物质,并统一换算成NH3的质量分数)并不能有效地提高CO2的脱除率.同时,分别对有机和无机添加剂进行筛选,选取哌嗪(PZ)和十二水磷酸钠(Na3PO4·12H2O)对吸收剂中高CO2负载鼍条件下的氨水溶液进行改性.实验结果表明,当哌嗪(PZ)浓度与总氨浓度之比为0.08,在吸收荆中CO2负载量为0.4、0.5和0.6的条件下,CO2脱除率可分别提高29.4%、31.0%和21.7%;当Na3PO4·12H2O浓度与总氨浓度之比为0.10,在吸收剂中CO2负载量为0.4、0.5和0.6的条件下,CO2脱除率可分别提高11.0%、11.7%和17.1%.     

膜法氨水吸收脱除烟气中CO2的研究

以氨水为吸收剂,对聚丙烯中空纤维膜分离烟气中CO2进行了实验研究.结果表明:随着气体流量和入口CO2浓度的增加,CO2去除率下降而传质速率增加;随着氨水浓度和氨水流量的增加,CO2去除率和传质速率均显著增加,但当氨水浓度大于2.5 mol·L-1,吸收液流量大于80m L·min-1后,膜接触器对CO2去除率和传质速率基本保持不变;膜接触器连续运行15 d后其吸收性能显著下降,CO2去除率、传质速率、总传质系数均下降约40%~50%.接触角测量、SEM及XPS表征结果表明:随着操作的进行,聚丙烯膜在吸收液环境中接触角逐渐降低,疏水性减弱,造成膜孔润湿;同时碳酸盐在膜孔形成结晶,堵塞膜孔,使得传质阻力进一步增加,从而造成膜接触器吸收性能的下降.     

碳酸氢铵溶液解吸二氧化碳研究

对氨法脱碳主要吸收产物碳酸氢铵溶液受热解吸CO2的过程开展实验研究,借以了解吸收剂再生特点.同时,考虑到常温下碳酸氢铵溶解度和不相称溶解的限制,选择对2mol·L-1以下浓度溶液进行60～90℃常压加热,考察加热温度及溶液浓度对CO2解吸过程的影响.结果表明,在实验条件下,碳酸氢铵溶液解吸CO2的选择性强,解吸比例随加热温度的升高和溶液浓度的增大而上升,但低于50%.反应动力学分析结果表明,碳酸氢铵溶液热分解过程为二级不可逆反应,反应速率常数k=4.4×1013exp(-13541/T).     

自然型氨基酸及其钾盐的 CO2吸收和再生特性

在CO2吸收过程中,选择具有不挥发和不发生氧化降解特性的氨基酸盐吸收剂有助于降低吸收剂损失和减轻环境污染风险,故本研究以CO2吸收速率和再生速率为指标,对L-精氨酸和精氨酸钾（PA）吸收剂的CO2吸收性能和常压下热再生性能进行了实验分析,并研究了吸收剂质量分数、反应温度及吸收-再生循环次数对CO2吸收特性的影响,同时还与乙醇胺（MEA）、二乙醇胺（DEA）和三乙醇胺（TEA）进行了对比分析.结果表明,在实验的质量分数范围内,PA具有最高的CO2吸收速率和吸收能力,分别为24.5×10-3mol.（L.min）-1和1.99 mol.mol-1,比相同质量分数的MEA高2.1%和290.2%.温度影响结果表明,40℃时PA和MEA的CO2吸收速率均高于其他实验温度.相同再生条件下,PA的贫液CO2负荷要略高于MEA,但PA的再生程度可达72.8%,比MEA高19%.同时,3次＂吸收-再生＂循环之后,10%PA的CO2吸收能力仍可保持在1.03mol.mol-1,比10%MEA高255.2%.实验结果也表明,L-精氨酸具有较强的CO2吸收能力,其CO2吸收速率与同质量分数的DEA可比.     

Distribution and ecological effect of mercury in Laogang landfill, Shanghai, China

Laogang landfill near Shanghai is the largest landfill in China, and receives about 10000 t of daily garbage per day, Samples of topsoil and plants were analyzed to evaluate mercury pollution from the landfill. For topsoil samples, there were significant correlations among total mercury （HgT）, combinative mercury （Hgc） and gaseous mercury （HgG）, and content of total organic carbon （TOC）, but, no significantly relationship was found between Hg content and filling time. Hg content changes in vertical profiles with time showed that the average Hgv of profiles 1992, 1996, and 2000 was similar, but their average HgG was quite different. HgT was significantly correlated with Hgc in profile 1992 and 2000, and Hgv was significantly correlated with Hg6 in profile 1996. HgG/Hgv ratio in profile samples decreased in the order of （HgG,/HgT）1992〉（HgG/HgT）1996〉〉（HgG/HgT）2000. A simple outline of Hg release in landfill could be drawn： with increasing of filling time, degradation undergoes different biodegradation, accordingly, gaseous mercury goes through small, more, and small proportion to total mercury. Distribution of Hg in plants was inhomogeneous, following the order of leaf〉root〉stem. The highest value of leaf may be associated with higher atmospheric Hg from landfill. Ligneous plants （e.g. Phyllostachys glanca, Prunus salicina and Ligustrum lucidum） are capable of enriching more Hg than herbaceous plants.     

EDTA-enhanced phytoremediation of lead contaminated soil by Bidens maximowicziana

Phytoremediation is a potential cleanup technology for the removal of heavy metals from contaminated soils.Bidens maximowicziana is a new Pb hyperaccumulator,which not only has remarkable tolerance to Pb but also extraordinary accumulation capacity for Pb.The maximum Pb concentration was 1509.3 mg/kg in roots and 2164.7 mg/kg in overground tissues.The Pb distribution order in the B. maximowicziana was:leaf>stem>root.The effect of amendments on phytoremediation was also studied.The mobility of soil Pb and the Pb concentrations in plants were both increased by EDTA application.Compared with CK(control check),EDTA application promoted translocation of Pb to overground parts of the plant.The Pb concentrations in overground parts of plants was increased from 24.23-680.56 mg/kg to 29.07-1905.57 mg/kg.This research demonstrated that B.maximowicziana appeared to be suitable for phytoremediation of Pb contaminated soil,especially,combination with EDTA.     

Decomposition of alachlor by ozonation and its mechanism

Decomposition and corresponding mechanism of alachlor, an endocrine disruptor in water by ozonation were investigated. Results showed that alachlor could not be completely mineralized by ozone alone. Many intermediates and final products were formed during the process, including aromatic compounds, aliphatic carboxylic acids, and inorganic ions. In evoluting these products, some of them with weak polarity were qualitatively identified by GC-MS. The information of inorganic ions suggested that the dechlorination was the first and the fastest step in the ozonation of alachlor.     

Enzymatic oxidation of aqueous pentachlorophenol

The influence of the nonionic surfactant Tween 80 on pentachlorophenol （PCP） oxidation catalyzed by horseradish peroxidase was studied. The surfactant was tested at concentrations below and above its critical micelle concentration （CMC）. Enhancement of PCP removal was observed at sub-CMCs. The presence of Tween 80 in the reaction mixture reduced enzyme inactivation which occurred through a combination of free radical attack and sorption by precipitated products. A simple first-order model was able to simulate time profiles for enzyme inactivation in the presence or absence of Tween 80. At supra-CMCs, the surfactant caused noticeable reductions in PCP removal, presumably through micelle partitioning of PCP which precluded the hydrophobic PCP molecule from interacting with the enzyme.     

基于综合水质标识指数和对应分析法的校园河道水质评价

以三峡大学的校园河道求索溪为研究对象,利用综合水质标识指数法确定求索溪水质类别,分析其水质时空变化规律,并利用对应分析法得出求索溪中不同监测点的主要污染因子.研究结果表明:求索溪整体的综合水质标识指数为7.423,整体水质为劣V类(地表水环境质量标准GB 3838-2002)且黑臭.从时间变化来看,求索溪4月份的水质最差,5月份次之,4、5月份所有监测点的水质都劣于V类且黑臭;8月份水质最好,水质为Ⅳ类;从空间分布来看,8个监测点综合水质标识指数均超过6.0,水质为劣V类,其中6号监测点的水质相对最好,监测点3号的水质相对最差;对应分析法得出求索溪的整体水体污染程度受总氮因子的影响最大,其次为总磷.该研究拟为求索溪及类似校园河道的水环境治理研究提供基础依据和参考.     

Effects of chitosan on growth of an aquatic plant (Hydrilla verticillata) in polluted waters with different chemical oxygen demands

Effects of chitosan on a submersed plant, Hydrilla verticillata, were investigated. Results indicated that H. venicillata could prevent ultrastructure phytotoxicities and oxidativereaction from polluted water with high chemical oxygen demand (COD). Superoxide dismutase (SOD) activity and malondialdehyde (MDA) contents in H. verticillata treated with 0.1% chitosan in wastewater increased with high COD (980 mg/L) and decreased with low COD (63 mg/L), respectively. Ultrastructural analysis showed that the stroma and grana of chloroplast basically remained normal. However, plant cells from the control experiment (untreated with chitosan) were vacuolated and the cell interval increased. The relict of protoplast moved to the center, with cells tending to disjoint. Our findings indicate that wastewater with high COD concentration can cause a substantial damage to submersed plant, nevertheless, chitosan probably could alleviate the membrane lipid peroxidization and ultrastructure phytotoxicities, and protect plant cells from stress of high COD concentration polluted water.     

Removal of cadmium using MnO2 loaded D301 resin

MnO2 loaded weak basic anion exchange resin D301 （Anion exchange resin, macroreticular weak basic styrene） as adsorbent has been prepared and applied to the removal of cadmium. The adsorption characteristics have been investigated with respect to effect of pH, equilibrium isotherms, removal kinetic data, and interference of the coexisting ions. The results indicated that the Cd^2＋ could be efficiently removed using MnO2 loaded D301 resin in the pH range of 3-8 from aqueous solutions with the co-existence of high concentration of alkali and alkaline-earth metals ions. The saturate adsorption capacity of the Cd^2＋ was 77.88 mg/g. The adsorption process followed the pseudo first-order kinetics. The equilibrium data obtained in this study accorded excellently with the Langmuir adsorption isotherm.     

Effect of coagulation pretreatment on the fouling of ultrafiltration membrane

The purpose of this study is to understand the effect and mechanism of preventing membrane fouling, by coagulation pretreatment, in terms of fractional component and molecular weight of natural organic matter （NOM）. A relatively higher molecular weight （MW） of hydrophobic compounds was responsible for a rapid decline in the ultrafiltration flux. Coagulation could effectively remove the hydrophobic organics, resulting in the increase of flux. It was found that a lower MW of neutral hydrophilic compounds, which could remove inadequately by coagulation, was responsible for the slow declining flux. The fluxes in the filtration of coagulated water and supernatant water were compared and the results showed that a lower MW of neutral hydrophilic compounds remained in the supernatant water after coagulation could be rejected by a membrane, resulting in fouling. It was also found that the coagulated flocs could absorb neutral hydrophilic compounds effectively. Therefore, with the coagulated flocs formed on the membrane surface, the flux decline could be improved.     

Penetration analysis of elements and bioleaching treatment of spent refractory for recycling

Acidithiobacillus ferrooxidans ATCC23270 and Acidithiobacillus thiooxidans TM-32 were used for bioleaching of spent refractories of aluminium and copper melting furnaces for their recycling.Firstly,penetration of elements into aluminium melting furnace refractory was investigated and it was found that up to 7 cm from surface was contaminated.Comparison on leaching efficiency by the strains ATCC23270 and TM-32 found that the strain ATCC23270 could treat larger amount of the refractories than the strain TM-32 could do.In the experiment of bioleaching of spent refractory aluminium melting furnace by the strain ATCC23270,high leaching efficiency were obtained on Al,Si,and Ca,and extremely low leaching performance was,however,shown on the rest of elements i.e.,Na,Mn,and Zn.Under the strain TM-32 use,relatively high leaching performance was recognized on Al,Si,Ca,Na,Mn,and Zn.In the experiment of bioleaching for spent refractory copper melting furnace,almost the same leaching trends were shown on Cu,Zn,Al,and Si under the strains ACTT23270 and TM-32 uses.     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.