水样中重金属铬的测定方法研究进展

介绍了利用化学分析法、分光光度法、原子吸收法以及荧光分析法来测定水样中铬含量的方法,对水样中铬测定方法的发展方向进行了展望。     

水样中六价铬测定方法的研究进展

综述了近几年水样中铬(Ⅵ)的测定方法,包括光度法、原子光谱法、荧光分析法、化学发光法、电化学分析法、化学传感器等,探讨了这几种分析检测方法的优缺点,展望了水样中铬(Ⅵ)测定方法的发展方向。     

测定环境中铬的分析方法

铬及不同形态铬、特别是水、土壤和空气中六价铬的定量分析步骤已逐步完善。本文对已发表的文献加以综合评述,重点放在环境样品的采集、保存、浸出以及溶出后铬分离与测定的方法与要求。尽管有一些新进展,但对环境中铬的准确和可信形态的了解仍然是分析化学的一项艰巨任务。     

不同基体改进剂在石墨炉原子吸收法测定水中铬元素的研究

采用石墨炉原子吸收分光光度法测定水中铬元素含量,探讨了不同基体改进剂对实验结果的影响。较系统地研究了5种基体改进剂在测定水样中铬含量的运用,并讨论了基体改进剂消除干扰的作用机理。结果表明,采用磷酸二氢铵作为基体改进剂检测的精密度和回收率更高,实验稳定性更好。     

腐植酸对Cr在污染土壤中吸附形态影响的研究

选用人为污染土壤为供试样品,在土样中加入腐植酸,采用连续浸提法研究了腐植酸对污染土壤中有毒重金属铬离子不同形态的影响。结果表明:在污染土壤中添加腐植酸可以改变土壤对铬离子各形态的吸持能力,使具有直接毒性的可溶态铬急剧减少,同时使铬的氧化物结合态、碳酸盐结合态及有机结合态增加,降低了铬在土壤中的流动性、活性和生物可利用性。以粘土与砂土作对比,结果说明由于腐植酸的加入,在增加土壤有机质的同时可以明显地固定土壤中的铬。     

昆明滇池铬形态分布研究

对滇池水中铬形态化合物进行了分离和测定。依据实验数据和滇池环境对滇池中铬形态的迁移转化进行了讨论。为滇池铬污染的研究和治理提供了一定依据。     

聚合氯化铝的盐基度与混凝性能关系研究

用三氯化铝滴碱法和铝酸钙酸溶一步法,分别制备了纯聚合氯化铝(PAC)和含钙的聚合氯化铝(CaPAC),对两种聚合铝的盐基度、铝的形态分布、混凝性能等进行了对比研究.采用Ferron逐时络合比色法对具有不同盐基度的PAC、CaPAC中的Ala、Alb和Alc形态分布进行了分析检测,并用烧杯试验方法考察了PAC、CaPAC对模拟水样和实际水样的混凝除浊性能.结果表明,PAC、CaPAC在对不同水样进行混凝处理后,水中余浊随两种聚合铝盐基度的增加而降低,余浊与盐基度表现出较好的相关性;在相同加药量条件下,CaPAC混凝除浊效果略好于PAC.另外,研究表明,Alb或Alc的形态分布与混凝除浊性能之间,未表现出明显的相关性.     

废水中Cr(Ⅲ)的吸附热力学和动力学研究进展

含铬废液中三价铬含量控制是含铬废液处理的重要组成部分.作为微量元素,体内含铬量不能超标吸收或体内缺失.铬在不同情形下显示不同形态化学变化.三价铬吸附热力学与动力学为从宏观和微观角度理解三价铬在吸附剂上的吸附行为提供理论基础.本文介绍铬价态变化、三价铬含量的传统与最新测试方式,分析近期三价铬吸附相关文献的吸附热力学与动力...     

铬渣特性及解毒利用技术

介绍了铬渣的来源,化学组成和矿物组成,并对铬渣中铬的5种形态进行了分析.此外,还介绍了铬渣解毒技术及其原理,并就铬渣处置、利用进行了探讨和展望.     

污泥中重金属在厌氧消化前后的形态分布分析

对污泥中的 8种重金属在厌氧消化前后的存在形态进行了分析试验。试验结果表明 :在 8种重金属元素中 ,汞、镉、铅、砷经厌氧消化后几乎全部以稳定形态存在 ,而锌、镍、铜、铬经厌氧消化后 ,其稳定形态含量亦不同程度增加     

Cation Exchange Equilibria with Chromium (III) Species by Strong Acid Ion Exchangers

The exchange of hydrogen ions for trivalent chromium species with strongly acidic exchange resins has been investigated. The experiments comprised of systems with chromium chloride and basic chromium sulphate which are applied in leather tanning. Exchange equilibria at ambient temperature were investigated as a function of pH and total chromium concentration. Exchange strongly depends on the speciation in each system. As can be expected, with chromium chloride solutions a strong preference of chromium species occurs. However, a complete pattern is found for systems with basic chromium sulphate where chromium species are not fully preferred.     

水浴振荡碱消解-火焰原子吸收法测定土壤中六价铬

建立了水浴振荡碱消解-火焰原子吸收法测定土壤中的六价铬的方法.称取经风干、研磨并过0.15 mm孔径筛的土壤样品2.0 g(精确至0.01 g)置于150 mL锥形瓶中,加入25.0 mL碱性提取溶液,再加入400 mg氯化镁和0.5 mL磷酸氢二钾-磷酸二氢钾缓冲溶液,用聚乙稀薄膜封口,置于水浴恒温振荡器中.常温振荡...     

耐温型CMC冻胶堵水剂的性能研究

羧甲基纤维素（CMC）的多环、多羟基结构有良好的油水选择性、耐温性和反应活性,适合与高价金属离子进行羟桥络合反应制备冻胶型堵水剂。作者对CMC铬冻胶耐温性、耐酸碱性、耐盐性及抗剪切性进行考察。实验结果表明与聚丙烯酰胺（HPAM）铬冻胶相比,CMC铬冻胶耐温性提高约40℃,可承受140℃高温;在pH=6-10、矿化度低于9000mg／L时,胶体强度较大,稳定性良好;胶体在剪切速率为2-100s-1时,冻胶粘度始终高于1000mPa·s,明显优于HPAM铬冻胶,可用于双液法堵水。     

Promoted Fe2O3‐Al2O3‐CuO Chromium‐Free Catalysts for High‐Temperature Water‐Gas Shift Reaction

Promoted Fe₂O₃‐Al₂O₃‐CuO (FAC) chromium‐free catalysts were prepared for high‐temperature water‐gas shift reactions and characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller method (BET), temperature‐programmed reduction (TPR), and transmission electron microscopy (TEM) techniques. The catalytic results revealed that among the investigated promoted catalysts with Ce, La, Zn, Y, and Mn as promoters, the Mn‐promoted sample showed higher activity compared to the other promoted catalysts. Increasing the Mn content improved the surface area and catalytic activity. The FAC catalyst promoted with a high Mn content exhibited maximum activity and relatively high stability in high‐temperature water‐gas shift reaction.     

Hydrogels as a Potential Chromatographic System: Absorption,Speciation, and Separation of Chromium Species from Aqueous Media

Hydrogels with highly charged forms and amphiphilic character, based on an anionic monomer 2-acrylamido-2-methyl-1-propansulfonic acid sodium salt (AMPSNa) and a cationic monomer 3-acrylamidopropyltrimethylammoniumchloride (APTMACl), were synthesized via a photo-polymerization technique and investigated for potential use in the separation of chromium species with different oxidation states. They were used for three main purposes. First, a single chromium species was successfully removed from an aqueous medium in the presence of other forms using the appropriate design and synthesis of the hydrogels. Secondly, the copolymerized p(AMPSNa-co-APTMACl) hydrogels were used to remove two chromium species simultaneously from an aqueous medium. Lastly, in addition to speciation of the chromium species, their separation and removal by an externally applied magnetic field using magnetically responsive hydrogels was demonstrated.     

Solid phase extraction of chromium (VI) from aqueous solutions by adsorption of its diphenylcarbazide complex on an alumina column

A simple method has been developed for the solid phase extraction of chromium (VI) based on the adsorption of its diphenylcarbazide (DPC) complex on an alumina column. The effect of various parameters such as acidity, stability of the column, sample volume, and interfering ions have been studied in detail. The adsorbed complex could be easily desorbed using sulphuric acid and the concentration of chromium has been established using atomic absorption spectrophotometry and visible spectrophotometry. The calibration graph was linear in the range of 0–1 µg/mL chromium (VI) with a detection limit of 4 µg/L. A highest preconcentration factor of 125 could be obtained for 5000 mL sample volume using glass wool as support for alumina. Chromium (VI) could be effectively separated from other ions such as zinc, nickel, copper, chloride, sulphate, and nitrate and the method has been successfully applied to study the recovery of chromium in spiked well water and tap water samples.     

酸化-预热处理方法解离去除高浓度络合态铬

金属铬络合染料废水中的铬Cr(Ⅲ)与偶氮类有机配体结合,呈络合状态,结构非常稳定。采用常规的中和混凝法对黑色、黄色和橙色三种铬络合物的废水进行处理,均不能有效地去除铬。研究表明．温度和酸度是影响络合态铬离子热力学稳定性的主要因素。对于黄色或橙色铬络合物,将废水进行预热以提高处理温度,或加酸酸化,都会使络合态铬离子结构破坏;而对于黑色铬络合物,其结构更为稳定,必须酸化并同时提高处理温度．才能有效地破坏黑色铬络合物的结构,游离出的铬离子极易通过投加石灰乳中和沉淀去除。因此,通过酸化、预热、中和混凝等步骤,可将该类高浓度络合态铬离子完全解离并去除,处理后含铬质量浓度降至1．0mg／L以下,达到了重金属处理排放要求。     

反应条件及陈化过程对氢氧化铬氧化速率的影响

氢氧化铬是含铬二次资源中铬的重要存在形式,也是含六价铬污染物还原时的主要产物,其氧化过程的研究对铬资源的提取和铬污染的控制具有重要意义。以亚硫酸钠还原重铬酸钠制备的氢氧化铬为研究对象,实验考察了氧化温度（室温~200 ℃）、氧化时间（0~168 h）、添加剂种类（碳酸钠、硫酸钠）等因素对氢氧化铬氧化的影响,并进行了氧化方程选取和动力学拟合计算。结果表明,温度越高两种氢氧化铬样品氧化反应越充分、氧化限度越大。在无添加剂条件下,200 ℃时新制、陈化氢氧化铬的氧化速率K值分别是80 ℃时的617、4 375倍;添加剂的加入会促进其氧化反应,140 ℃条件下,新制氢氧化铬添加碳酸钠、硫酸钠为n（Na）∶n（Cr）=0.2时的氧化速率K值分别是无添加时的10、4倍;新制氢氧化铬较陈化氢氧化铬更易氧化,氧化速率K值为陈化氢氧化铬样品的1.4~1.9倍,可能与其所含结合水较多有关。     

铬渣中铬的氧化法浸出工艺条件的研究

采用碱性条件下氧化处理铬渣的方法研究了氧化剂种类及各工艺条件对铬渣中铬浸出量的影响。结果表明,NaOH加入量为0.12 g,氧化剂NaClO3的加入量达0.2 g或Na2C2O6加入量为0.2 g时,在80℃水浴条件下反应120 min后,Cr(Ⅵ)与总铬的浸出量最高。延长反应时间和提高水热反应温度,有利于提高铬渣中铬的浸出量,但温度过高会导致铬渣中Cr(Ⅵ)及总铬的浸出量下降。