Adsorption of Chromium (VI) on <Emphasis Type="Italic">Azadirachta Indica</Emphasis> (Neem) Leaf Powder

A novel adsorbent was developed from mature leaves of the Neem tree (Azadirachta Indica) for removing metal ions from water. The adsorbent, in the form of fine powder, was found to be very effective in removing chromium (VI) from aqueous solution. The adsorption was carried out in a batch process taking different concentrations of the metal ion in aqueous solution with variation in adsorbent amount, pH, agitation time and temperature. The suitability of the adsorbent was tested with Langmuir and Freundlich isotherms and with various equilibrium kinetic data. A small amount of the Neem Leaf Powder (NLP) (1.6 g dm^–3) could remove as much as 87% of Cr (VI) in 300 min from a solution of concentration 14.1 mg dm^–3 at 300 K. The optimum range of pH for the adsorption process was 4.5–7.5 and since the natural pH of the Cr (VI) solution was 5.5, no addition of acid or alkali was necessary for achieving maximum adsorption. The adsorption coefficients indicated a high potentiality for the NLP to be used as an adsorbent for removing Cr (VI) from water.     

Verbindungen des Germainums und Zinns. 17. Alkylarylstannylen-Komplexe des Chroms und Molybdäns ohne Donorstabilisierung

Compounds of Germanium and Tin. 17 [1]. Alkylarylstannylene Complexes of Chromium and Molybdenum without Donor Stabilization Reaction of the complexes [(OC)₅M(THF)], M = Cr, Mo, with the alkylarylstannylene RR′Sn: R = 2,4,6-tBu₃C₆H₂, R′ = CH₂C(CH₃)₂-3,5-tBu₂C₆H₂, provides the donor-free stannylene complexes [(OC)₅Cr?SnRR′] ( 6 ) and [(OC)₅Mo?SnRR′] ( 8 ), respectively. The X-ray structure analyses of the isotypic compounds 6 and 8 reveal the three coordinate tin atoms in strictly planar environments and acute CSnC angles of 91.2° ( 6 ) and 91.3° ( 8 ).     

One-electron redox reactions involving chromium(0) and molybdenum(0) bis-1,3,5-trimethylbenzene derivatives

The reaction of M(η⁶-1,3,5-Me₃C₆H₃)₂, M = Cr, Mo, with the tetrahalides of Groups 4 and 5 elements proceeds with the monoelectronic oxidation of the metal bis-arene to the [M(η⁶-Me₃C₆H₃)₂]⁺ cation. In the case of MX₄, M = Ti, X = Cl, Br, M = V, X = Cl, and of Nb₂Cl₁₀ the reduction products are the titanium(III), vanadium(III) halides and the niobium(IV) chloride, isolated as the solvate anions [MCl₄(THF)₂]⁻ and [NbCl₄(CH₃CN)]⁻. The reaction of the tetrachloro complexes MCl₄(THF)₂, M = Zr, Hf, with Cr(η⁶-1,3,5-Me₃C₆H₃)₂ in THF produces the ionic [Cr(η⁶-1,3,5-Me₃C₆H₃)₂][MCl₅(THF)], which has been characterized by single-crystal X-ray diffraction in the case of hafnium.     

(Z)-1-methoxy-4-(diphenylphosphino) but-1-ene-3-yne: A versatile synthon for unsymmetrically substituted (diphenylphosphino) diacetylene derivatives

An efficient synthesis of Ph₂P-C≡C-C≡C-Li, 1, was found, starting from commercially available (Z)-1-methoxybut-1-ene-3-yne and its diphenylphosphino derivative 2. The lithio compound 1 was condensed with electrophiles to give Ph₂P-C≡C-C≡C—Σ (Σ = SiR₃, SnR₃, B(NⁱPr)₂) 3. Compound 2 was easily transformed into the phosphonium salt 6 and the phosphine oxide 7 using MeI and H₂O₂ respectively. Derivatives 3 (Σ = SiMe₃, SnMe₃) are reactive at phosphorus and at the Σ group; complexation with W(CO)₅THF gave the expected derivatives W(CO)₅Ph₂P-C≡C-C≡C—Σ (Σ = SiMe₃, SnMe₃), 10, and in the case of Σ = SnMe₃, coupling reaction between Ph₂P-C≡-C-C≡C-SnMe₃, 3c, and (η⁵-IC₅H₄)Mn(CO)₃ in the presence of PdCl₂(CH₃CN)₂ as a catalyst gave the complex 11, Ph₂P-C≡C-C≡C-(η⁵-C₅H₄)Mn(CO)₃.     

中铬钢堆焊层冲蚀腐蚀磨损特性

本文以中铬钢为对比材料，对三种焊条堆焊层在不同介质、冲蚀角度下浆体冲蚀腐蚀磨损特性进行了研究．结果表明：新研制的堆焊ｌ＃堆焊层的浆体冲蚀腐蚀磨损抗力与中铬钢相当，并依次高于Ｄ６０８和Ａ１３２堆焊层；除Ａ１３２堆焊层外，随着介质ＰＨ值升高，其冲蚀腐蚀磨损抗力增强；当冲蚀角度为９０°时，堆焊层的浆体冲蚀腐蚀磨损抗力显著高于冲蚀角度为６０°时。     

铬镀液中CrO3的电化学还原

通过对酸性铬镀液的电化学测试以及对电极表面的XPS分析,发现在金属铬沉积前,铜阴极上发生多步骤的铬酸电还原反应,其中间产物与电极表面发生化学作用,形成主要成分为CuOCrOH的氧化膜;与此同时,电极表面附近形成阴极膜,氧化膜及阴极膜的存在引起异常的循环伏安图和负阻现象。     

9-呲啶基荧光酮与铬显色反应的研究

本文研究了9-吡啶基荧光酮与铬的反应条件,确定在pH5.0～6.0范围内形成稳定的络合物,λ_(max)=590nm,组成为Me∶R=1∶3,表观摩尔吸光系数ε=1.12×10~5L·mol~(-1)·cm~(-1)。应用拟定的方法测定了水中的铬,结果令人满意。     

电镀非晶铬的研究

研究了多种镀液在不同工艺参数条件下电镀铬层的结构特性。文献上应用X射线衍射方法研究镀铬层的结构特性时,其 2θ(Cu·Ka)角仅测到85°为止,但在本研究中,将2θ(Cu·Ka)的测定扩大到145°,并且在135°附近发现了新的非晶结构。结果表明,在一定条件下可以得到非晶镀层,并获得了形成非晶镀层的工艺条件。文章还讨论了非晶镀层的形成原因及其耐蚀性。     

45钢表面激光铬合金化层的组织与性能

本文讨论了45钢表面铬合金化层的形成过程和激光工艺参数、铬粉厚度对合金化层深度和铬含量的影响,并与未经激光处理的45钢,1Cr18Ni9Ti钢进行了电化学性能和耐腐蚀性能比较;文中最后分析讨论了合金化层的组织结构与耐腐蚀性的关系。     

The Cumulation of Chromium and Arsenic Species in Fish (Poecilia reticulata)

Abstract

Chromium-51 and arsenic-74 were used for the investigation of the uptake and the release of different chromium and arsenic species in fish. It has been found that only trimethylarsine can be rapidly taken up directly from water. The release of chromium(III), consumed by fish in food, is very rapid: about 99.9% of chromium is released within a few days. The same results were obtained with chromium(III) acetylacetonate or chromium(III) ethylenediaminotetraacetate. About 95% of arsenic acid, methylarsonic acid, dimethylarsinic acid or arsenic(III) diethyldithiocarbamate are released within a few days whereas the remaining arsenic is released with the biological half time 35 ± 5 days.