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排序方式: 共有163条查询结果,搜索用时 31 毫秒
131.
铬(Ⅵ)污染高岭土电动修复影响因素研究 总被引:1,自引:0,他引:1
通过正交试验研究了电动修复Cr(Ⅵ)污染高岭土的主要影响因素。试验选用重铬酸钾作为污染物,配制高岭土中Cr(Ⅵ)初始质量分数为500mg.kg-1。实验研究了电动修复过程施加电压、处理时间、含水量以及对阴极电解产生的OH-的控制等4种影响因素对修复效率的影响。正交实验结果表明对阴极电解产生的OH-的控制对修复效率影响最大,其次为施加电压和处理时间,含水量影响最小。阴极电极产生的OH-的控制试验表明电动修复过程中,一部分Cr(Ⅵ)还原为Cr(Ⅲ),Cr(Ⅲ)与阴极电解产生的OH-生成沉淀,从而显著影响其去除效率。随着施加电压、处理时间和含水率增加,Cr(Ⅵ)去除效率增加。各种因素综合作用下,最高去除效率为96.5%,最低仅为3.0%。土壤含水率对去除效率存在一定影响,建议下一步针对土壤含水率进行单因素研究。 相似文献
132.
Removal of chromium (VI) from aqueous solution using walnut hull 总被引:2,自引:0,他引:2
In this study, removal of chromium (VI) from aqueous solution by walnut hull (a local low-cost adsorbent) was studied. The extent of adsorption was investigated as a function of solution pH, contact time, adsorbent and adsorbate concentration, reaction temperature and supporting electrolyte (sodium chloride). The Cr (VI) removal was pH-dependent, reaching a maximum (97.3%) at pH 1.0. The kinetic experimental data were fitted to the first-order, modified Freundlich, intraparticle diffusion and Elovich models and the corresponding parameters were obtained. A 102.78 kJ/mol Ea (activation energy) for the reaction of chromium (VI) adsorption onto walnut indicated that the rate-limiting step in this case might be a chemically controlled process. Both the Langmuir and Freundlich isotherms were suitable for describing the biosorption of chromium (VI) onto walnut hull. The uptake of chromium (VI) per weight of adsorbent increased with increasing initial chromium (VI) concentration up to 240-480 mg/L, and decreased sharply with increasing adsorbent concentration ranging from 1.0 to 5.0 g/L. An increase in sodium chloride (as supporting electrolyte) concentration was found to induce a negative effect while an increase in temperature was found to give rise to a positive effect on the chromium (VI) adsorption process. Compared to the various other adsorbents reported in the literature, the walnut hull in this study shows very good promise for practical applicability. 相似文献
133.
Cr(VI) was often reported to oxidize soil organic matter at acidic environments due to its high ORP, probably thus changing cationic metal species bound to soil organic matter, and influencing their electro-migration patterns. However, such an effect on the electro-migration was not confirmed in most previous studies. Therefore, this study applied a fixed voltage direct current field on an aged electroplating contaminated clayed soil, with a special interest in the direct or indirect influence of Cr(VI) on the electro-migration of other coexisting metals. After 353 h electrokinetic process, 81% of Zn, 53% of Ni and 22% of Cu in the original soil were electro-migrated into the electrolyte, and most of the remaining concentrated near the cathode. The Cr(VI) oxidized some soil organic matter along its migration pathway, with a pronounced reaction occurred near the anode at low pHs. The resulting Cr(III) reversed its original movement, and migrated towards the cathode, leading to the occurrence of a second Cr concentration peak in the soil. Metal species analyses showed that the amount of metals bound to soil organic matter significantly decreased, while a substantial increase in the Cr species bound to Fe/Mn (hydro-)oxides was observed, suggesting an enhancement of cationic metal electro-migration by the reduction of Cr(VI) into Cr(III). However, the Cr(VI) may form some stable lead chromate precipitates, and in turn demobilize Pb in the soil, as the results showed a low Pb removal and an increase in its acid-extractable and residual fractions after electrokinetic remediation. 相似文献
134.
We compared the fatty acid composition of leaves taken from poplars on a metal-contaminated landfill, and on the uncontaminated roadside bordering this site. For the first time, it is shown that the percentage of linolenic acid, which is mainly associated with thylakoid lipids, was significantly lower in tree species within the landfill than within the control area. A correlation study was carried out to investigate relationships between the C18:3/(C18:0 + C18:1 + C18:2) fatty acid ratios and the metal contents in soils and leaves. Lead and chromium leaf contents were significantly negatively correlated to this fatty acid ratio. The impact of each of these metals remains difficult to evaluate, but chromium in leaf likely plays a major role in toxicity. In addition, the decrease in the C18:3/(C18:0 + C18:1 + C18:2) fatty acid ratio occurred at low leaf metal content, and therefore it is shown that this ratio can be used as an early indicator of the effect of metals. 相似文献
135.
火焰原子吸收光度法测定废水中总铬 总被引:6,自引:3,他引:3
刘荣臻 《环境监测管理与技术》2000,12(1):35-35
阐述了硝酸-高氯权消解、火焰原子吸收法直接测定工业废水中总铬。方法特征度0.054mg/L(1%吸收),检测限0.036mg/L,加标回收率96%~102%,相对标准左1%~17%。 相似文献
136.
ICP- AES法测定防腐处理后木材中可溶性铜铬砷 总被引:2,自引:1,他引:1
采用电感耦合等离子发射光谱法同时测定防腐处理后木材中可溶性铜、铬、砷,优化了试验条件,确定了最佳分析线。方法在0.500mg/L—10.0mg/L范围内线性良好,铜、铬、砷的检出限分别为0.003mg/L、0.01mg/L、0.07mg/L.木材样品平行测定的RSD为0.5%—1.2%,加标回收率为97.0%—102%,与原子吸收光谱法的测定结果相吻合。 相似文献
137.
The term “phytoremediation” is used to describe the cleanup of heavy metals from contaminated sites by plants. This study
demonstrates phytoremediation potential of Indian mustard (Brasicca juncea (L.) Czern. & Coss.) genotypes for chromium (Cr). Seedlings of 10 genotypes were grown hydroponically in artificially contaminated
water over a range of environmentally relevant concentrations of Cr (VI), and the responses of genotypes in the presence of
Cr, with reference to Cr accumulation, its phytotoxity and anti-oxidative system were investigated. The Cr accumulation potential
varied largely among Indian mustard genotypes. At 100 μM Cr treatment, Pusa Jai Kisan accumulated the maximum amount of Cr
(1680 μg Cr g−1 DW) whereas Vardhan accumulated the minimum (107 μg Cr g−1 DW). As the tolerance of metals is a key plant characteristic required for phytoremediation purpose, effects of various levels
of Cr on biomass were evaluated as the gross effect. The extent of oxidative stress caused by Cr stress was measured as rate
of lipid peroxidation. The level of thiobarbituric acid reactive substances (TBARS) was enhanced at all Cr treatments when
compared to the control. Inductions of enzymatic and nonenzymatic antioxidants were monitored as metal-detoxifying responses.
All the genotypes responded to Cr-induced oxidative stress by modulating nonenzymatic antioxidants [glutathione (GSH) and
ascorbate (Asc)] and enzymatic antioxidants [superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase
(GR)]. The level of induction, however, differed among the genotypes, being at its maximum in Pusa Jai Kisan and its minimum
in Vardhan. Pusa Jai Kisan was grown under natural field conditions with various Cr treatments, and Cr-accumulation capacity
was studied. The results confirmed that Pusa Jai Kisan is a hyperaccumulator of Cr and hypertolerant to Cr-induced stress,
which makes this genotype a viable candidate for use in the development of phytoremediation technology of Cr-contaminated
sites. 相似文献
138.
139.
通过建立2个简单的铬生物地球化学循环模型PM和CM,来说明人类工业活动对铬的生物地球化学循环的影响。通过对PM和CM的比较发现,人类的工业活动向陆地、海水和大气圈的输入通量,占其各自总输入通量的69.65%、56.96%和38.23%。 相似文献
140.