H_(2)S、HCN、PH_(3)在FeO(100)表面吸附的密度泛函理论研究

基于密度泛函理论研究了H_(2)S、HCN、PH_(3)在FeO(100)表面的吸附行为,其吸附位点主要考虑四个:Fe-top(铁顶位)、O-top(氧顶位)、Hollow(空位)、Bridge(桥位).结果表明H_(2)S吸附在O-top吸附位点的吸附能最小,为-1.02 eV,即在该位点的吸附体系最稳定.当HCN吸附在FeO(100)表面时,各吸附位点的稳定顺序为Hollow>Fe-top>Bridge>O-top.PH_(3)的最稳定的吸附位点与H_(2)S的一致,为O-top吸附位点,其吸附能为-1.11 eV.当H_(2)S吸附在O-top吸附位点时,H_(2)S与FeO(100)表面的电荷转移量最多,说明该吸附构型最稳定,而HCN吸附在FeO(100)表面,在Hollow吸附位点的电荷转移量最多,也即该吸附位点属于最稳定吸附位点.PH_(3)与FeO(100)表面之间的电荷转移量最多的吸附位点与H_(2)S的相同.当H_(2)S和PH_(3)吸附在O-top吸附位点时,吸附后的态密度曲线整体向低能级移动,峰值降低,其吸附结构变得更加稳定.而HCN吸附在Hollow位点时,吸附后的HCN态密度曲线向能量更低的区域移动,吸附体系变得更稳定.

剧毒气体PH_(3)的干法净化技术研究进展

磷化氢(PH_(3))是一种来源广泛的剧毒气体,未经处理排放到大气中会对人体和环境造成严重危害。近年来,国家对PH_(3)的排放进行了严格的规定,因此,尾气中PH_(3)的深度净化受到了广泛的关注。干法是主流的PH_(3)净化技术,主要包括吸附法和催化法。相较于湿法,干法具有性能好、稳定性强、耗水量小以及不产生二次污染等优点。本文首先从吸附法入手,分别探讨了复合金属氧化物吸附剂、活性炭基吸附剂及其他材料(分子筛、二氧化硅等)的研究现状,深入分析了各类脱磷吸附剂的结构性质及优缺点。其次对催化分解PH_(3)的机理进行了总结归纳,重点讨论了各类催化剂的构-效关系。最后,介绍了其他干法(燃烧法、等离子体降解法、生物法)在PH_(3)净化领域的应用。在此基础上,讨论了干法脱磷技术的主要优势以及面临的挑战,并对干法脱除PH_(3)技术的发展方向进行了展望。本工作可以为脱磷吸附剂/催化剂的构建和设计提供参考和指导。

改进型人工快渗除磷效果及途径研究

针对人工快渗对磷去除效率低的问题,将碳酸钙作为改良剂用于构建人工快渗系统,以研究不同水力负荷下磷的去除效果及除磷途径和机理。结果显示:水力负荷在0.1 m^(3)/(m^(2)·d)和0.2 m^(3)/(m^(2)·d)时,人工快渗出水溶解氧质量浓度均高于2 mg/L,总磷去除率均达到99%以上。当废水经过系统上层时,磷主要以固化的形式去除,占总去除量的95.78%;在落干期,磷去除过程仍持续进行,以PH_(3)形式去除,磷转化为PH_(3)的过程可持续14 h,PH_(3)瞬时质量浓度最大为1.67 mg/m^(3)。填料中的脱氢酶、碱性磷酸酶活性均明显提高。高通量测序分析表明,系统中聚磷菌(Phosphate Accumulating Organisms,PAOs)较多,各菌属自上而下相对丰度分别为:陶厄氏菌属Thauera上层7.36%、中层0.24%、下层2.67%,不动杆菌属Acinetobacter上层0.35%、中层6.27%、下层0.93%,假单胞菌属Pseudomonas上层0.19%、中层0.38%、下层1.25%,节杆菌属Arthrobacter上层0.21%、中层0.09%、下层0.34%。尽管出水溶解氧质量浓度高于2 mg/L,但系统中厌氧菌、兼氧菌含量较高。与磷转化有关的菌群自上而下相对丰度分别为:变形菌门Proteobacteria上层57.05%、中层50.15%、下层46.79%,厚壁菌门Firmicutes上层1.14%、中层1.82%、下层6.74%,Clostridium_sensu_stricto上层0.06%、中层0.21%、下层1.09%。在快渗系统微生态中,同时具备好氧和厌氧菌群是磷转化为PH_(3)的重要原因。

Cu/ACF adsorbent modified by non-thermal plasma for simultaneous adsorption–oxidation of H_(2)S and PH_(3)

Non-thermal plasma(NTP)surface modification technology is a new method to control the surface properties of materials,which has been widely used in the field of environmental protection because of its short action time,simple process and no pollution.In this study,Cu/ACF(activated carbon fiber loaded with copper)adsorbent was modified with NTP to remove H_(2)S and PH_(3) simultaneously under low temperature and micro-oxygen condition.Meanwhile,the effects of different modified atmosphere(air,N_(2) and NH_(3)),specific energy input(0–13 J/mL)and modification time(0–30 min)on the removal of H_(2)S and PH_(3) were investigated.Performance test results indicated that under the same reaction conditions,the adsorbent modified by NH_(3) plasma with 5 J/mL for 10 min had the best removal effect on H_(2)S and PH_(3).CO_(2) temperature-programmed desorption and X-ray photoelectron spectroscopy(XPS)analyzes showed that NH_(3) plasma modification could introduce amino functional groups on the surface of the adsorbent,and increase the types and number of alkaline sites on the surface.Brunauer-Emmett-Teller and scanning electron microscopy showed that NH_(3) plasma modification did not significantly change the pore size structure of the adsorbent,but more active components were evenly exposed to the surface,thus improving the adsorption performance.In addition,X-ray diffraction and XPS analysis indicated that the consumption of active components(Cu and Cu_(2)O)and the accumulation of sulfate and phosphate on the surface and inner pores of the adsorbent are the main reasons for the deactivation of the adsorbent.

磷化氢生物净化体系及抑制作用机理

在PH_(3)生物净化体系中添加呼吸链电子传递抑制剂,对比分析微生物生长代谢、磷的迁移转化、活性氧(ROS)产生及氧化酶活性等变化规律.当鱼藤酮或抗霉素A分别添加至R1、R2PH_(3)生物反应器后,其微生物体O_(2)^(-)·含量在运行时间14~17d期间的平均值分别上升至0.68,0.96mmol/g,明显高于空白对照组R0反应器.除自由基O_(2)^(-)·外,另一类型的活性氧HO·也存在于PH_(3)净化系统中;受累积的活性氧影响,生物体内丙二醛(MDA)含量处于较高水平,PH_(3)净化效率通常不超过75%,添加抑制剂的R1与R2反应体系在15~17d期间PH_(3)平均去除率分别下降至65.1%、59.5%.pH值、ROS含量以及氧化酶活性等因素均明显影响PH_(3)生物净化效果,当Fe^(3+)、Cu^(2+)、Mg^(2+)等金属阳离子迁移转运至微生物体内时,超氧化物歧化酶(SOD)与过氧化氢酶(CATase)活性得以不同程度的增强,可缓解活性物质O_(2)^(-)·或HO·导致的氧化胁迫作用,PH_(3)净化效能得以适度提升.

Influence of drying and calcination temperatures for Ce-Cu-Al trimetallic composite catalyst on simultaneous removal H_(2)S and PH_(3):Experimental and DFT studies

This work explored the influences of the drying and calcination temperatures on a Ce-Cu-Al trimetallic composite catalyst for the simultaneous removal of H_(2)S and PH_(3).The effects of both temperatures on the structural features and activity were examined.The density functional theory method was used to calculate adsorption energies and further analyze their adsorption behavior on different slabs.Experiments revealed suitable drying and calcination temperatures to be 60 and 500℃,respectively.The capacity reached 323.8 and 288.1 mg/g.Adjusting drying temperature to 60℃is more inclined to form larger and structured grains of CuO.Rising calcinating temperature to 500℃could increase the grain size and redox capacity of CuO to promote performance.Higher temperatures would destroy the surface structure and lead to a crystal phase transformation,which was that the CuO and Al_(2)O_(3)were gradually recombined into CuAl_(2)O_(4)with a spinel structure.The exposed crystal planes of surficial CuO and CuAl_(2)O_(4)were determined according to characterization results.Calculation results showed that,compared with CuO(111),H_(2)S and PH_(3)have weaker adsorption strength on CuAl_(2)O_(4)(100)which is not conducive to their adsorption and removal.

A Cu-modified active carbon fiber significantly promoted H_(2)S and PH_(3) simultaneous removal at a low reaction temperature

Poisonous gases,such as H_(2)S and PH3,produced by industrial production harm humans and damage the environment.In this study,H_(2)S and PH3 were simultaneously removed at low temperature by modified activated carbon fiber(ACF)catalysts.We have considered the active metal type,content,precursor,calcination,and reaction temperature.Experimental results exhibited that ACF could best perform by loading 15%Cu from nitrate.The optimized calcination temperature and reaction temperature separately were 550℃ and 90℃.Under these conditions,the most removal capacity could reach 69.7 mg/g and 132.1 mg/g,respectively.Characterization results showed that moderate calcination temperature(550℃)is suitable for the formation of the copper element on the surface of ACF,lower or higher temperature will generate more cuprous oxide.Although both can exhibit catalytic activity,the role of the copper element is significantly greater.Due to the exceptional dispersibility of copper(oxide),the ACF can still maintain the advantages of larger specific surface area and pore volume after loading copper,which is the main reason for better performance of related catalysts.Finally,increasing the copper loading amount can significantly increase the crystallinity and particle size of copper(oxide)on the ACF,thereby improving its catalytic performance.In situ IR found that the reason for the deactivation of the catalyst should be the accumulation of generated H_(2)PO_(4)^(-) and S0_(4)^(2-)(H_(2)0)^(6) which could poison the catalyst.