铅在棉秆基活性炭上的吸附动力学与热力学

以棉秆与棉秆纤维为原料,利用磷酸活化法制备了低成本的高比表面微孔棉秆基活性炭,通过静态实验研究了活性炭对水溶液中铅的吸附特性,测定了溶液pH值、吸附时间、溶液温度对吸附的影响,探讨了吸附动力学、热力学及吸附机制.根据低温液氮(N2/77K)吸附测定数据,以BET方程、BJH法及H-K法对活性炭孔结构进行了表征,以Boehm滴定、FTIR、零电荷点pHPZC测定及元素分析定量表征活性炭表面含氧官能团.结果表明,以棉秆和棉秆纤维为原料制备的活性炭的比表面积分别为1570和1731m2·g-1,含氧酸官能团含量分别为1.43和0.83mmol·g-1,均高于商业活性炭ST1300.静态吸附实验表明,棉秆基活性炭对铅有较大的吸附容量和吸附效率,最大吸附量超过120mg·g-1,溶液pH对吸附有较大的影响,吸附量随时间增大而增大,在5min内可达饱和吸附量的80%;吸附动力学数据符合假二级方程,Freundlich方程能更好地描述等温吸附行为;热力学研究表明,吸附吉布斯自由能(ΔG0)0,而焓变(ΔH0)0,说明吸附为吸热的自发反应过程,升温有利于吸附,离子交换可能在吸附过程中起了重要作用.     

巢湖周围池塘氮、磷和有机质研究

巢湖周围池塘众多,根据池塘位置和地表径流补给差异,池塘可以分为村庄内池塘、毗邻村庄池塘和农田区域池塘(远离村庄的池塘).本研究采集了巢湖周围136口池塘上覆水和沉积物样品,调查巢湖周围池塘中氮、磷以及有机质污染现状.结果表明,池塘上覆水中总氮、氨氮、硝态氮、亚硝态氮、总磷、溶解态磷和COD平均含量分别为2.53、0.65、0.18、0.02、0.97、0.38和51.58mg·L-1;池塘沉积物中总氮、氨氮、硝态氮、亚硝态氮、总磷、无机磷、有机磷和烧失量平均含量分别为1575.36、35.73、13.30、2.88、933.19、490.14、414.75mg·kg-1和5.44%;90%以上的池塘总氮、总磷含量达到或超过富营养化水平.位于村庄内的池塘上覆水和沉积物中总氮和氨氮的含量显著高于位于农田区域的池塘.上覆水和沉积物中无机氮表现为:氨氮硝态氮亚硝态氮.池塘上覆水和沉积物中有机质与总氮、总磷之间存在显著的正相关性.池塘中氮、磷和有机物质主要为陆源性输入,池塘位置和径流补给方式明显影响其中的氮、磷和有机质含量.通过截留径流中的氮、磷和有机质,池塘能够有效减少进入巢湖的营养盐含量.     

Effects of irrigation,fertilization and crop straw management on nitrous oxide and nitric oxide emissions from a wheat–maize rotation field in northern China

One-year winter wheat–summer maize rotation is the most popular double cropping system in north-central China, and this highly productive system is an important source of nitrous oxide (N₂O) and nitric oxide (NO) emissions due to the high fertilizer N and irrigation water inputs. To sustain the high crop production and mitigate the detrimental impacts of N₂O and NO emissions, improved management practices are extensively applied. The aim of this study is therefore to evaluate the effects of an improved management practice of irrigation, fertilization and crop straw on grain yield and N₂O and NO emissions for a wheat–maize rotation field in northern China. Using automated and manual chamber measuring systems, we monitored N₂O and NO fluxes for the conventional (CT, 2007–2008), improved (IT, 2007–2008), straw-amended (WS, 2008–2009), straw-not-amended (NS, 2008–2009), and no N-fertilizer treatments (WS–NN, 2008–2009), respectively, for one rotation-year. The grain yields were determined for CT and IT for three rotation-years (2005–2008) and for WS, NS and WS–NN for one rotation-year (2008–2009). The improved management of irrigation and fertilization reduced the annual N fertilization rate and irrigation amount by 17% and 30%, respectively; increased the maize yield by 7–14%; and significantly decreased the N₂O and NO emissions by 7% (p < 0.05) and 29% (p < 0.01), respectively. The incorporation of wheat straw increased the cumulative N₂O and NO emissions in the following maize season by 58% (p < 0.01) and 13%, respectively, whereas the effects of maize straw application were not remarkable. The N₂O and NO emission factors of applied N were 2.32 ± 2.32% and 0.42 ± 1.69% for wheat straw and 0.67 ± 0.23% and 0.54 ± 0.15% for chemical N-fertilizers, respectively. Compared to conventional management practices using high application rates of irrigation water and chemical N-fertilizer as well as the field burning of crop straw, the improved management strategy presented here has obvious environmentally positive effects on grain yield and mitigation of N₂O and NO emissions.     

太湖沉积物酸可挥发性硫化物分布特征及重金属生物有效性评价

对太湖4个湖区沉积物的酸可挥发性硫化物（AVS）和同步可提取重金属（SEM）的水平和垂直分布特征进行了研究,并对沉积物重金属的潜在生态风险进行初步评价.结果表明,氧化还原电位（Eh）与AVS和SEM含量均无显著相关性;表层沉积物中AVS含量分布在研究区差异较大,变异系数达134.28%;∑SEM含量波动较小,变异系数为...     

低温A/O-MBR工艺启动试验研究

研究了A/O-MBR工艺低温(水温在5~12℃)启动效能,结果表明,低温下A/O-MBR工艺启动迅速,活性污泥的培养驯化时间较短。启动过程中根据出水水质情况,逐渐提高负荷,运行34 d,系统对COD的去除率能达到90%以上,系统对氨氮的去除率能达到96%以上,至稳定运行后氨氮的负荷平均可达到0.419kg/(m3.d),反硝化效果系统去除率基本能稳定在60%左右。     

五种重点关注的重金属废渣的处理方法与利用现状

近年来,随着我国经济的迅速发展,重金属废渣的总量逐步扩大,引发了很多社会、经济、环境问题,成为了企业和环保领域关注的热点问题,国家近期提出了五种需重点关注的重金属废渣。本文在对国内外资料的总结和回顾的基础上,着重论述了这五种重金属废渣的来源、产量,对于现在常用的各种处理方式进行对比分析,指出其优缺点;总结了一般重金属废渣的处理模式,提出了自己的看法;展望了重金属废渣处理技术的发展方向。     

Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash

The mutual e ects of metal cations (Cu2+, Pb2+, Zn2+, and Cd2+) and p-nitrophenol (NP) on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2+, Pb2+, and Zn2+ diminished the adsorption and increased the desorption of NP remarkably, while Cd2+ had no such e ect. In contrast, NP diminished the adsorption of Cu2+, Pb2+, and Zn2+ onto ash, however, this suppression e ect depended on the initial concentrations of metal cations. NP had no e ect on Cd2+ adsorption on ash. Fourier transform infrared (FT-IR) and X-ray absorption spectroscopic (XAS) studies suggested the following mechanisms responsible for the metal suppression e ect on NP adsorption: (1) large hydrated Cu2+, Pb2+, and Zn2+ shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; (2) Cu2+, Pb2+, and Zn2+ may block the micropores of ash, resulting in decreased adsorption of NP; (3) complexation of Cu2+, Pb2+, and Zn2+ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a “soft acid”, Cd2+ is less e cient in the complexation of oxygencontaining acid groups than Cu2+, Pb2+, and Zn2+. Thus, Cd2+ had no e ect on the adsorption of NP on wheat ash.     

Roles of manganese oxides in degradation of phenol under UV-Vis irradiation: Adsorption, oxidation, and photocatalysis

The effect of crystal structure on photocatalytic activities of manganese oxides and underlying reaction mechanism were investigated.     

Visible light responsive N-F-codoped TiO2 photocatalysts for the degradation of 4-chlorophenol

Visible light responsive N-F-codoped TiO₂ photocatalysts exhibit a higher catalytic activity than N-doped TiO₂ for the degradation of 4-chlorophenol due to the synergistic effect of nonmetal elements.     

Preliminary report on methane emissions from the Three Gorges Reservoir in the summer drainage period

Considerable variations may exist in CH4 emissions from the Three Gorges Reservoir.