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排序方式: 共有840条查询结果,搜索用时 15 毫秒
831.
对不同浓度KCL和不同pH下,3种可变电荷土壤和4种恒电荷土壤CI-吸附量进行了测定。结果表明,土壤CI-吸附量随平衡 CI-浓度 C(e)增加而增大,恒电荷土壤呈线性,可变电荷土壤在添加 CI- 0.5-5.0 mmol/L.下,符合 Langmuir吸附等温式。同一浓度下的CI-吸附量及其随浓度增加的速率均为砖红壤>红壤>赤红壤>黄棕壤>棕壤、暗棕壤和黑土,与这些土壤所带正电荷量顺序相一致。Langmuir方程K值较小且几种土壤差异不大。恒电荷土壤对CI-的吸附量很小,在浓度较低时常出现负吸附,其吸附机理可能更多的是与K+吸附时的同时吸附。7种土壤CI-吸附量均随pH增加而降低,但降低强度可变电荷土壤远大于恒电荷土壤。 相似文献
832.
Singh KP Singh VK Malik A Sharma N Murthy RC Kumar R 《Environmental monitoring and assessment》2007,131(1-3):237-254
Rain water samples were collected to study the chemical composition of wet atmospheric precipitation (first event) over the
Lucknow city in the northern Indo-gangetic alluvial plains. The samples were collected in the month of July, 2005 from different
sites. The wet precipitation samples were analyzed for pH, EC, major ions (, Cl−, , , , F−, Na+, K+, Ca2+, Mg2+, ) and heavy metals (As, Cd, Al, Co, Cr, Cu, Fe, Mn, Mo, Ni, Hg, Pb, Se, Sn, Ti, V, Zn). The pH values of wet precipitation
samples ranged between 6.5 and 8.7. The analysis of linear regression applied to the set of studied variables and computation
of neutralization factors showed that neutralization occurred in precipitation samples and Ca2+ had the maximum neutralization capacity. It was found that Cl−, , Ca2+, Mg2+, Na+ and K+ in the precipitation samples originated mainly from crustal/anthropogenic sources in the region. On an average Fe, and Al
accounted for >72% of the total concentration of trace metals in the wet precipitation samples followed by Zn (>10%). Enrichment
factors calculated for heavy metals over reference background level in seawater and Earth’s crust showed relatively higher
enrichment of Zn. The principal component analysis (PCA) identified the possible sources of ionic species and heavy metals
in the wet precipitation samples. 相似文献
833.
Research on precipitation carried out systematically at the University station at Jeziory in the Wielkopolski National Park
(western Poland) allowed the determination of pollutants deposited with precipitation in this forest ecosystem. During 13 years
of study, the pH of precipitation was found to persist at a low level (4.33 on average), which resulted a substantial deposition
of H+. Values of acidifying and basic ions deposited in this area were determined and compared with the respective figures obtained
at selected EMEP stations studying background pollution, the means for Poland, and areas subjected to considerable human impact.
The use of the critical load function made it possible to establish that the S and N deposition for 2002–2005 were below its
line. 相似文献
834.
835.
探讨不同离子浓度与不同无机溶液的混合对紫外光吸收的影响,结果表明,盐酸盐在较高浓度下吸收值迅速增大,吸收峰向红区移动,而硫酸盐在远紫区有一定程度的吸收,KH2PO4与NH4F接近无吸收。多数情况下,无机溶液对紫外光的吸收主要决定于阴离子类型,而与阳离子无关.不同类型溶液的混合基本不改变溶液的吸收特性,硝酸盐在低浓度下对紫外的吸收极为稳定,基本不受共存离子的干扰。0.01mol/LCuSO4与2mol/LKCI吸收峰与硝酸盐吸收峰重叠,但饱和CaSO4与硝酸盐吸收峰不重叠。 相似文献
836.
生命周期评价方法在氧化钴生产中的应用 总被引:1,自引:0,他引:1
氧化钴生产是锂钴氧二次电池全生命周期重要阶段之一。本实验是以粗氢氧化钴为原材料,利用生命周期评价方法对氧化钴生产进行综合分析,全面评价氧化钴生产中资源、能源消耗以及环境污染物排放,并对由此产生的环境影响潜值进行量化估算。结果显示,氧化钴生产中环境潜在影响大小依次是富营养化、粉尘和烟尘、酸化、全球变暖、固体废弃物负担,其相对值依次是:24.04、22.88、4.30、3.29、1.49。根据评价结果,提出对氧化钴生产过程进行技术改造及相关材料使用更换来降低氧化钴生产对环境的影响。 相似文献
837.
The adsorption of lead, cadmium and nicel from aqueous solution by sawdust of walnut was investigated. The effect of contact time, initial metal ion concentration and temperature on metal ions removal has been studied. The equilibrium time was found to be of the order of 60 min. Kinetics fit pseudo first-order, second-order and intraparticle diffusion models, hence adsorption rate constants were calculated. The adsorption data of metal ions at temperatures of 25, 45 and 60~C have been described by the Freundlich and Langmuir isotherm models. The thermodynamic parameters such as energy, entropy and enthalpy changes for the adsorption of heavy metal ions have also been computed and discussed. Ion exchange is probably one of the major adsorption mechanisms for binding divalent metal ions to the walnut sawdust. The selectivity order of the adsorbent is Pb(I1)~Cd(II)〉Ni(I1). From these results, it can be concluded that the sawdust of walnut could be a good adsorbent for the metal ions from aqueous solutions. 相似文献
838.
Removal of heavy metals using waste eggshell 总被引:2,自引:0,他引:2
PARK Heung Jai JEONG Seong Wook YANG Jae Kyu KIM Boo Gil LEE Seung Mok 《环境科学学报(英文版)》2007,19(12):1436-1441
The removal capacity of toxic heavy metals by the reused eggshell was studied.As a pretreatment process for the preparation of reused material from waste eggshell,calcination was performed in the furnace at 800℃for 2 h after crushing the dried waste eggshell.Calcination behavior,qualitative and quantitative elemental information,mineral type and surface characteristics before and after calcination of eggshell were examined by thermal gravimetric analysis(TGA),X-ray fluorescence (XRF),X-ray diffraction(XRD) and scanning electron microscopy(SEM),respectively.After calcination,the major inorganic composition was identified as Ca(lime, 99.63%)and K,P and Sr were identified as minor components.When calcined eggshell was applied in the treatment of synthetic wastewater containing heavy metals,a complete removal of Cd as well as above 99% removal of Cr was observed after 10 min. Although the natural eggshell had some removal capacity of Cd and Cr,a complete removal was not accomplished even after 60 min due to quite slower removal rate.However,in contrast to Cd and Cr,an efficient removal of Pb was observed with the natural eggshell rather than the calcined eggshell.From the application of the calcined eggshell in the treatment of real electroplating wastewater, the calcined eggshell showed a promising removal capacity of heavy metal ions as well as had a good neutralization capacity in the treatment of strong acidic wastewater. 相似文献
839.
Unravelling the effects of complexation of transition metal ions on the hydroxylation of catechol over the whole pH region 下载免费PDF全文
Zexiu An Jianfei Sun Qiong Mei Bo Wei Mingxue Li Ju Xie Maoxia He Qiao Wang 《环境科学学报(英文版)》2022,34(5):392-402
Catechol pollutants (CATPs) serving as chelating agents could coordinate with many metal ions to form various CATPs-metal complexes. Little information is available on the effects of complexation of metal ions on CATPs degradation. This work presents a systematical study of •OH-mediated degradation of catechol and catechol-metal complexes over the whole pH range in advanced oxidation processes (AOPs). Results show that the pH-dependent complexation of metal ions (Zn2+, Cu2+, Ti4+ and Fe3+) promotes the deprotonation of catechol under neutral and even acidic conditions. The radical adduct formation (RAF) reactions are both thermodynamically and kinetically favorable for all dissociation and complexation species, and OH/O− group-containing C positions are more vulnerable to •OH attack. The kinetic results show that the complexation of the four metal ions offers a wide pH range of effectiveness for catechol degradation. At pH 7, the apparent rate constant (kapp) values for different systems follow the order of catechol+Ti4+ ≈ catechol+Zn2+ > catechol+Cu2+ > catechol+Fe3+ > catechol. The mechanistic and kinetic results would greatly improve our understanding of the degradation of CATPs-metal and other organics-metal complexes in AOPs. The toxicity assessment indicates that the •OH-based AOPs have the ability for decreasing the toxicity and increasing the biodegradability during the processes of catechol degradation. 相似文献
840.
根据“粒子设计”思想,以粉煤灰为载体,采用非均匀形核法制备了一种核壳结构粉煤灰负载纳米氢氧化镁复合材料,并对其吸附废水中Cu (II)、Ni (II)和Pb (II)性能进行研究.采用扫描电子显微镜(SEM)、EDS能谱、比表面积分析仪(BET)、X射线衍射(XRD)、红外光谱(FTIR)等技术对包覆前后的复合粉体进行了表征.结果表明,复合粉体表面均匀包覆了大量纳米氢氧化镁和少量水合碳酸镁,比表面积增大到原来(粉煤灰1.79m2/g)的30多倍,平均孔径由11nm增加至14.7nm.平均孔隙宽度从12.8nm增加至15.4nm.粉煤灰表面的Si-O-Si、Si-O-C与氢氧化镁之间形成Si-O-C-O-Mg和Si-O-Mg-OH.复合粉体材料去除重金属的效率明显高于原粉煤灰和氢氧化镁,其单位饱和吸附量分别达到了216.30、116.50、160.96mg/g.根据Zeta电位、FTIR及模拟方程分析了复合粉体吸附重金属离子机理,结果表明复合粉体材料对重金属离子通过沉淀反应、静电吸引、离子交换等方式进行吸附,吸附过程等温线符合Langmuir等温模型,动力学符合颗粒内扩散模型,热力学符合自发吸热反应.通过解吸再生试验发现,经过5次循环再生利用后,复合粉体对重金属离子的去除率达到50%以上,这说明复合粉体在吸附过程中具有良好的再生性能. 相似文献