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931.
以高铁低铝煤矸石为原料,经机械活化,酸浸提取有价元素铝、铁.首先利用硫酸盐在不同温度和不同硫酸质量分数条件下的溶解度差异,通过结晶分离法从酸浸液中转移出硫酸盐,然后利用新鲜煤矸石中和酸浸液中的游离酸,调节pH值至1.5~2.0,制备酸浸初步净化液.以初步净化液为研究对象,利用不同离子水解pH值的差异进行物质分离,再经纯化处理制备相应产品.用XRD对原料和产品进行了表征.结果表明,在硫酸质量分数为75%的条件下,反应液固比为4、温度为125℃、3h时煤矸石中铝、铁溶出率分别为92.5%、99.7%.通过项目经济效益分析可知,该法可以产生良好的环境效益、社会效益,同时可实现煤矸石增值,产生较好的经济效益. 相似文献
932.
933.
934.
Haoran Dong Guangming Zeng Chang Zhang Jie Liang Kito Ahm Piao Xu Xiaoxiao He Mingyong Lai 《环境科学学报(英文版)》2015,27(6):180-188
This study investigated the interaction between Cu2+ and nano zero-valent iron (NZVI) coated with three types of stabilizers (i.e., polyacrylic acid [PAA], Tween-20 and starch) by examining the Cu2+ uptake, colloidal stability and mobility of surface-modified NZVI (SM-NZVI) in the presence of Cu2+. The uptake of Cu2+ by SM-NZVI and the colloidal stability of the Cu-bearing SM-NZVI were examined in batch tests. The results showed that NZVI coated with different modifiers exhibited different affinities for Cu2+, which resulted in varying colloidal stability of different SM-NZVI in the presence of Cu2+. The presence of Cu2+ exerted a slight influence on the aggregation and settling of NZVI modified with PAA or Tween-20. However, the presence of Cu2+ caused significant aggregation and sedimentation of starch-modified NZVI, which is due to Cu2+ complexation with the starch molecules coated on the surface of the particles. Column experiments were conducted to investigate the co-transport of Cu2+ in association with SM-NZVI in water-saturated quartz sand. It was presumed that a physical straining mechanism accounted for the retention of Cu-bearing SM-NZVI in the porous media. Moreover, the enhanced aggregation of SM-NZVI in the presence of Cu2+ may be contributing to this straining effect. 相似文献
935.
Resource conservation strategies for rice‐wheat cropping systems on partially reclaimed sodic soils of the Indo‐Gangetic region,and their effects on soil carbon 下载免费PDF全文
V.K. Mishra S. Srivastava A.K. Bhardwaj D.K. Sharma Y.P. Singh A.K. Nayak 《Natural resources forum》2015,39(2):110-122
The Indo‐Gangetic plain is characterized by intensive agriculture, largely by resource‐poor small and marginal farmers. Vast swathes of salt‐affected areas in the region provide both challenges and opportunities to bolster food security and sequester carbon after reclamation. Sustainable management of reclaimed soils via resource conservation strategies, such as residue retention, is key to the prosperity of the farmer, as well as increases the efficiency of expensive initiatives to further reclaim sodic land areas, which currently lay barren. After five years of experimentation on resource conservation strategies for rice‐wheat systems on partially reclaimed sodic soils of the Indo‐Gangetic region, we evaluated changes in different soil carbon pools and crop yield. Out of all resource conservation techniques which were tested, rice‐wheat crop residue addition (30% of total production) was most effective in increasing soil organic carbon (SOC). In rice, without crop residue addition (WCR), soils under zero‐tillage with transplanting, summer ploughing with transplanting and direct seeding with brown manuring showed a significant increase in SOC over the control (puddling in rice, conventional tillage in wheat). In these treatments relatively higher levels of carbon were attained in all aggregate fractions compared to the control. Soil aggregate sizes in meso (0.25‐2.0 mm) and macro (2‐8 mm) ranges increased, whereas micro (< 0.25 mm) fractions decreased in soils under zero‐till practices, both with and without crop residue addition. Direct seeding with brown manuring and zero tillage with transplanting also showed an increase of 135% and 95%, respectively, over the control in microbial biomass carbon, without crop residue incorporation. In zero tillage with transplanting treatment, both with and without crop residue showed significant increase in soil carbon sequestration potential. Though the changes in accrued soil carbon did not bring about significant differences in terms of grain yield, overall synthesis in terms of balance between yield and carbon sequestration indicated that summer ploughing with transplanting and zero tillage with transplanting sequestered significantly higher rates of carbon, yet yielded on par with conventional practices. These could be appropriate alternatives to immediately replace conventional tillage and planting practices for rice‐wheat cropping systems in the sodic soils of the Indo‐Gangetic region. 相似文献
936.
以2,4-二氯酚(2,4-DCP)为目标污染物,采用间歇试验,接种厌氧混合微生物,考察葡萄糖共基质条件下不同pH值时零价铁(Fe)0对2,4-DCP生物降解的效应,并对Fe0与厌氧微生物联合体系的作用机理进行探讨。结果表明:Fe0与厌氧微生物联合作用可提高2,4-DCP的降解效果,且中性或偏碱性环境下联合体系对目标污染物的促进效果较酸性环境明显,初始pH值为8时目标污染物的降解效果最好。Fe0在厌氧条件下腐蚀产生的OH-可有效平衡葡萄糖发酵产生的有机酸,使体系挥发性脂肪酸(VFA)的浓度维持在较低水平(300 mg/L),同时促使联合体系pH值上升从而利于目标物2,4-DCP的降解。Fe0在酸性环境的腐蚀较强,腐蚀产物以Fe2+为主,Fe3+含量较少。不同pH值时"Fe0+微生物"体系的COD去除率与目标物降解效果有一定相关性。 相似文献
937.
北京市密云水库上游金铁矿区土壤重金属污染特征及对比研究 总被引:14,自引:4,他引:10
不同金属矿山选冶活动造成的矿区及周边土壤中重金属的分布累积特征不同.为了解密云水库上游金矿和铁矿矿区土壤中重金属地球化学特征的异同及污染状况,对区域内典型的金矿和铁矿矿区进行土壤样品采集,应用地球化学方法研究了2种土壤中重金属的污染特征,并应用地累积指数法评价了其污染状况.结果表明,2种土壤中除As外的其它重金属含量明显高于北京市土壤重金属背景值,金矿矿区土壤重金属含量普遍高于铁矿矿区.相关性分析表明,金矿矿区土壤中Cu含量与Pb、Zn(p<0.01)及Cr、有机质(OM)含量(p<0.05)之间显著相关,pH值与Pb含量(p<0.01)及Hg含量(p<0.05)呈显著负相关,而铁矿矿区土壤中重金属含量之间的相关性不显著.金矿尾砂中重金属含量明显高于铁矿尾砂,与矿区土壤污染状况一致.地累积指数法评价结果显示,金铁矿区土壤中重金属的污染程度均已十分严重,金矿矿区土壤污染程度高于铁矿,金矿矿区土壤重金属的污染程度由高到低依次为:Pb>Hg>Cd>Cr>Cu>Zn>Co>As;铁矿矿区土壤重金属的污染程度由高到低依次为:Pb>Cd>Cr>Co>Cu>Zn>Hg>As.该研究数据可为同一区域内不同金属矿区重金属污染的有效监控与治理提供科学依据. 相似文献
938.
Dynamics of arsenic in salt marsh sediments from Dongtan wetland of the Yangtze River estuary, China
The mobility and transformation of arsenic (As) in salt marsh sediments were investigated in Dongtan wetland of the Yangtze River estuary, China. As in surface water, pore water and the rhizosphere sediments were quantified. The microcosm incubation experiments were conducted during the flooding of the sediments to examine As dynamics that occurred during changing redox conditions. The concentrations of dissolved As in pore water (0.04-0.95 μmol/L) were significantly greater than that in surface water (0.03-0.06 μmol/L). Under anoxic conditions, the reactive As could be initially mobilized by the reductive dissolution of Fe(III) (hydr)oxides. Subsequently, most of the dissolved As was likely to be associated with secondary iron (hydr)oxide phases and remained in solid phases. The seasonal variability of acid volatile sulfide concentrations suggest the anoxic conditions are enhanced during summer by Spartina alterniflora compared to Phragmites australis and Scirpus mariqueter, causing a notable increase in As mobility. Generally, there was a typical variation in redox conditions with season in salt marsh sediments of Dongtan wetland, in which the dynamics of As mobility and transformation possibly were controlled by iron, and all of this could be significantly influenced by the rapid spread of S. alterniflora. 相似文献
939.
以Fe(NO3)3为前驱物,制备了水合氧化铁吸附剂样品,以NaOH为解吸剂,研究了样品对模拟废水中磷酸根的吸附和解吸性能。结果表明,水合氧化铁对磷酸根有较好的吸附效果;随着pH的降低,水合氧化铁对磷酸根的吸附能力增强,在pH为2时吸附达92.5%;吸附前15 min吸附速率较快,约150 min达到平衡,吸附动力学曲线符合二级动力学模型;用水合氧化铁对初始浓度为50~100 mg/L模拟含磷废水吸附,随着初始浓度的增大,磷的去除率下降;水合氧化铁对磷酸根的吸附等温线较符合Langmuir吸附模型;用NaOH对水合氧化铁行解吸,浓度为40 g/L有最好的解吸率,60 min时达到解吸平衡。 相似文献
940.