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Electromigration in porous media is enhanced by a new type of electrokinetic processing. Compared with a single-oriented electric field, a continuously reoriented electric field was proven to sharply enhance mass transport of several heavy metals in kaolin. The initial concentration of the metals was: Cd: 250 mg/kg; Cu: 250 mg/kg; Ni: 250 mg/kg; Zn: 900 mg/kg. Electric field reorientation was obtained by the use of a fixed anode and a cathode that rotated at different frequencies (0, 0.25, 1.00, 1.25, 2.00, 5.00 and 10.00 r/m). Mass transport evidently increased from 0 r/m to 1.25 r/m, and then decreased as the rotation speed reached 10 r/m. From 0 r/m to 1.25 r/m, mass transport increased 2.87 times for Cd, 3.17 times for Cu, 2.11 times for Ni, and 4.13 times for Zn. We suggest that continuous reorientation of the electric field facilitates the advance of ions through kaolin pores, minimizing the retardation effect caused by media tortuosity. 相似文献
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An improved configuration of the membrane stack was adopted in the electrodeionization （EDI） cell to prevent precipitation of bivalent metal hydroxide during the running. The operational parameters that influenced the removal of copper ions from the dilute solution were optimized. The result showed that a moderate decrease in the inlet pH value and a moderate increase in the applied voltage could achieve a better removal effect. The steady process of electroplating wastewater treatment could be achieved with a removal efficiency of more than 99.5% and an enrichment factor of 5-14. The concentration of copper in purified water was less than 0.23 mg/L. This demonstrated the applicability of recovering heavy metal ions and purified water from electroplating effluent for industrial reuse. 相似文献
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王安春 《江西教育学院学报》2001,22(2):80-84
清代前期，江西地主阶级追逐地租的欲望有增无减。围绕着分配问题，阶级与广大佃农之间的斗争进一步激烈，斗争的原因大致是佃农反对地主的夺佃、佃农急取永佃权、佃农要求减租、佃农反对交纳押租、预租以及反对地主的残酷镇压等几类型，其中，由地主阶级残酷镇压引起的佃农抗租起义，将清朝前期佃农抗租斗争推向了新的阶段，使清朝的封建统治处于风雨遥之中。 相似文献
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高考在为国家选拔人才,提供公平竞争的平台等方面发挥了积极功能,但它同时也带来了一定的负面影响：高考给考生、家长、教师和学校带来了巨大压力。以缓解考生压力这一心理问题立论,从四个方面分析了形成高考压力的深层原因及其所带来的消极影响,并提出相关的对策与建议。 相似文献
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Genotypic and environmental variation in cadmium, chromium, arsenic, nickel, and lead concentrations in rice grains 总被引：1，自引：0，他引：1
Genotypic and environmental variation in Cd, Cr, As, Ni and Pb concentrations of grains, and the relationships between these heavy metals and Fe, Zn were investigated using 9 rice genotypes grown in 6 locations for two successive years. Significant genotypic variation was detected in the five heavy metal concentrations in grains, indicating the possibility to reduce the concentration of these heavy metals in grains through breeding approach. The environmental effect varied with metal, with Pb and Ni having greater variation than the other three metals. There was significant genotype-environment （location） interaction of the concentrations of all five heavy metals in grains, suggesting the importance of cultivar choice in producing rice with low heavy metal concentrations in grains for a given location. Correlation analysis showed that Cd and As, Cr and Ni, and As and Pb concentrations in rice grains were closely associated, and that Ni concentration in grains was negatively correlated with Zn concentration. 相似文献
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应用地积累指数法评价淮河淮南段沉积物中重金属污染 总被引：1，自引：0，他引：1
采集淮河淮南段4个采样点的12个沉积物样品,应用电感耦合等离子质谱仪对Pb、Zn、Cu、Cr等重金属的质量浓度进行了测试,并用地积累指数法评价了河流沉积物的重金属污染。结果表明:淮河淮南段沉积物中重金属总量及富集程度不高,富集的时间延展性不甚明显,沉积物受重金属污染的程度轻微。 相似文献
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文章运用文献资料法、观察法、数理统计法等研究方法,对我国和国外大级别运动员比赛中技术动作的运用进行了统计分析,得出国外运动员多项技术动作的成功率明显高于我国运动员的结论。建议我国大级别运动员加强冲拳、鞭腿、摔法的训练,以提高其在比赛中的成功率。 相似文献