罗威邦COD多参数水质综合测定仪的使用及注意事项

化学需氧量(COD)是综合评价水体受还原性物质污染程度的重要指标之一.在诸多的测定方法中,重铬酸钾回流氧化法被用于国内标准.本文尝试了罗威邦(Lovibond) COD多参数水质综合测定仪检测水样中COD的方法.     

化学需氧量

化学需氧量（COD）又称化学耗氧量，是利用化学氧化剂（如高锰酸钾）将废水中可氧化物质（如有机物、亚硝酸盐、亚铁盐、硫化物等）氧化分解，然后根据残留氧化剂的量计算出氧的消耗量，以粗略地表示废水中的有机物含量，反映水体有机物的污染程度。     

催化消解密封法测定水中化学需氧量

文章介绍了用密封管催化消解,分光光度计测定水中化学需氧量的过程;COD浓度5～5 0 mg/L时,其剩余Cr2 O2 -7的吸光度与COD有良好的线性关系;方法检测限为1 .6mg/L ;用COD标准溶液进行校核试验,其精密度、准确度和加标回收效果理想;水样中氯离子浓度2 0 0 0 mg/L时不影响测定结果。     

基于紫外光谱法的水质化学需氧量在线检测技术

化学需氧量(COD)是水质有机物污染的代表性指标,也是水质监测的必测项目之一。基于紫外光谱法直接测定COD是一种无需化学试剂、无样品前处理、无二次污染的绿色检测技术。本文详细论述了紫外光谱法的检测原理,研制开发了基于此技术的COD在线监测仪器。通过国家标准规定的邻苯二甲酸氢钾标准溶液实验与针对实际水样的检测实验,紫外吸光度与水质COD之间的线性度达0.99,将检测COD值与真实COD值进行配对T检验,二者无显著性差异,且检测技术具有快速、无试剂和重复性好的优点。     

快速测定CODcr的方法进展

作为水体中有机污染的重要指标之一的化学需氧量的测定 ,一直以来都沿用标准回流法 ,这一方法存在明显的缺点 ,费时费电 ,试剂用量大 ,银盐、汞盐、铬盐易造成二次环境污染 ,对于含氯离子浓度较高而 COD值较低的水样 ,准确度较差 ,于是 ,人们纷纷着手对经典方法进行改进 ,寻求快速准确的测定方法 ,本文按消解方法分别加以讨论。1　密封消解法 [1 7]1978年 ,Best和 Cusseres[1 ] 采用密封管来测定 COD。国内有黄君礼 2 ]、黄彩海 [3 ]、陈学德 [4] 等分别开展了这方面的工作。他们把温度控制在 15 0℃左右恒温加热 2小时 ,优势并不明显 ,…     

一种在线式水体化学需氧量检测系统设计

化学需氧量(COD)是水体有机污染物的代表性参数,也是水质检测中一个必测指标。紫外吸收光谱法测定水体COD具有实时、在线检测等优点。基于此技术,设计开发了一套自动采样、在线式检测水体COD系统。通过国家标准规定的水体COD测量实验,确定紫外最大特征吸收波长为281nm,特征吸收波长区域峰面积与水体COD之间的线性度R2达到0.9853,并通过实际预测待测溶液的COD含量,结果表明相对误差小于6%。实验结果表明该系统具有原位、在线、无污染检测等优点,满足水体COD在线检测要求。     

一种用于COD测定修正的氯离子在线检测技术

化学需氧量(COD)是评价水质污染程度的重要指标,我国采用重铬酸钾法作为国家标准的 COD测定方法.针对该方法的测量结果受氯化物影响较大的问题,从原理上分析了氯离子对于 COD测定过程的影响规律,并设计了一种基于纳米玻璃探针结构的氯离子浓度检测系统,在较大的量程范围内实现了氯离子浓度的快速测量,为提高COD测量的准确性提供了一种新的技术方案.同时还对离子电流检测的影响因素进行了理论研究和实验验证,讨论了探针直径和偏置电压对系统量程和灵敏度的影响.     

紫外-可见光谱水质多参数监测分析方法研究北大核心CSCD

为了研究水质污染参数COD、TOC和NO_(3)-N的紫外-可见光谱吸收及交叉干扰特性,搭建了一套水质多参数监测系统,采用化学计量法和偏最小二乘回归算法建立解析模型,并对实际水样进行验证测试。实验表明:对浊度、COD、TOC、NO_(3)-N等溶液进行单因变量建模时,预测结果的R2优于0.9987;对浊度、COD和TOC混合溶液进行三因变量建模时,COD和TOC预测结果的R2分别为0.9576和0.9506;对浊度、COD、TOC和NO_(3)-N混合溶液进行四因变量建模时,NO_(3)-N预测结果的R2为0.9460;测量结果呈现良好的线性回归关系。     

浏阳河水成功去“味”

长沙市环保局消息,长沙上半年完成COD（化学需氧量）污染减排45.72%,较去年同期减少排放8.08%,城市污水处理能力大幅提高,浏阳河等水体水质明显改善。     

COD快速分析仪的开发和研制

根据纳米TiO2光催化原理，开发研制了一种以光度分析为检测手段的COD快速分析仅。本仪器检测时间短，消解时间在10min以内，操作简单，测量精密度高，能同时测定各类废水及地表水的COD值，且与标准法有良好的相关性．大大降低了对环境的二次污染，实现了对水体中COD值的快速分析。     

Proficiency testing programs to improve traceability in chemical analysis

The results of the proficiency test program T062 organised by CNACL (China National Accreditation Committee for Laboratories) were analysed with different statistical procedures: the robust statistic procedure used by the proficiency test organisers and the UNI ISO 5725-2 [8] procedure which is a basic method for the determination of the repeatability and the reproducibility of a standard measurement method to improve the traceability in chemical analysis.The data are taken from a program of chemical analysis on a low alloy steel.The obtained results are commented; the paper aim to give elements of discussion about standard test method, uncertainty evaluations, and repeatability of test results on chemical analysis performed by chemical laboratories.     

Fabrication of high-quality SNOM probes by pre-treating the fibres before chemical etching

A new method to fabricate high‐quality fibre probes for scanning near‐field optical microscopes by pre‐treating the fibre before chemical etching was proposed and implemented. In the pre‐treating process, the diameter of the fibre is reduced to a range of 7 –20 μm by etching one end of the fibre in the HF solution and a taper angle is formed simultaneously. Then the tapered part of the fibre is coated with a thick layer of plastic film and etched in the HF solution again. High‐quality probes are obtained with an apex diameter as low as ∼20 nm and a large cone angle.     

Real time in situ ellipsometric and gravimetric monitoring for electrochemistry experiments

This work describes a new system using real time spectroscopic ellipsometer with simultaneous electrochemical and electrochemical quartz crystal microbalance (EQCM) measurements. This method is particularly adapted to characterize electrolyte/electrode interfaces during electrochemical and chemical processes in liquid medium. The ellipsometer, based on a rotating compensator Horiba Jobin-Yvon ellipsometer, has been adapted to acquire Psi-Delta spectra every 25 ms on a spectral range fixed from 400 to 800 nm. Measurements with short sampling times are only achievable with a fixed analyzer position (A=45 degrees ). Therefore the ellipsometer calibration is extremely important for high precision measurements and we propose a spectroscopic calibration (i.e., determination of the azimuth of elements according to the wavelength) on the whole spectral range. A homemade EQCM was developed to detect mass variations attached to the electrode. This additional instrument provides further information useful for ellipsometric data modeling of complex electrochemical systems. The EQCM measures frequency variations of piezoelectric quartz crystal oscillator working at 5 MHz. These frequency variations are linked to mass variations of electrode surface with a precision of 20 ng cm(-2) every 160 ms. Data acquisition has been developed in order to simultaneously record spectroscopic ellipsometry, EQCM, and electrochemical measurements by a single computer. Finally the electrodeposition of bismuth telluride film was monitored by this new in situ experimental setup and the density of electroplated layers was extracted from the optical thickness and EQCM mass.     

基于双光束光路系统在线监测COD的稳定性研究

针对光度法测定COD的在线监测仪受环境温度影响较大、测定结果稳定性差的问题,对光路和信号采集条件等因素进行验证与探讨,提出优化光纤结构和信号采集、处理方式,以提高系统的稳定性,降低系统受环境温度等因素的影响程度。结果表明,采用特殊结构双光束光纤传导光信号,在信号采集温度为50℃,信号采集时间为1s的条件下,测定结果稳定,受环境温度影响小。根据标准HJ 377-2019要求,对仪器的检出限、示值误差、重复性、低浓度漂移等指标进行测试,其结果均优于仪器测试指标要求,该装置及监测方法可用于水质COD的在线监测。     

水中总氮无损快速分析方法

总氮（TN）是水质监测的重要指标，快速、准确的检测水体中TN的含量对水质监测具有重大意义。本文在空气背景下使用不同光程石英样品池（1mm、2mm和4mm）采集了55个自然水样近红外光谱(NIRS)，并应用逐步多元线性回归（SMLR）和偏最小二乘（PLS）方法对水样的TN含量进行回归分析，建立相应的定量分析模型。结果发现：样品池为1mm时模型的TN分析值与国标法得到的标准值相关性最高，达到0.97，在显著性水平大于0.05的条件下对近红外光谱分析方法与国标法的测定结果进行t-检验，二者无显著性差异。结果表明，使用近红外光谱分析方法不需任何化学试剂，检测时间短，能够实现水样总氮指标的无损快速分析，并且可以为进一步开发研制总氮在线自动监测系统提供参考。     

Electrogenerated chemical polishing of copper

Stress free polishing method is preferred for a damage free surface of copper with ultra-flatness and ultra-smoothness. Such a surface offers a perfect substrate for integrated circuits and micro-electromechanical systems fabrication. A new polishing method, called electrogenerated chemical polishing (EGCP), is proposed based on the principle of the scanning electrochemical microscope (SECM) and the diffusion controlled chemical reaction. Roughness of a Cu surface is reduced from 100.5 nm to 3.6 nm by the proposed method. To demonstrate the planarization capability of this new method, a patterned Cu surface with an array of micro-columns is planarized with a peak-valley (PV) value from 4.7 μm to 0.059 μm.     

Hierarchical optimal control of large-scale nonlinear chemical processes

In this paper, a new approach is presented for optimal control of large-scale chemical processes. In this approach, the chemical process is decomposed into smaller sub-systems at the first level, and a coordinator at the second level, for which a two-level hierarchical control strategy is designed. For this purpose, each sub-system in the first level can be solved separately, by using any conventional optimization algorithm. In the second level, the solutions obtained from the first level are coordinated using a new gradient-type strategy, which is updated by the error of the coordination vector. The proposed algorithm is used to solve the optimal control problem of a complex nonlinear chemical stirred tank reactor (CSTR), where its solution is also compared with the ones obtained using the centralized approach. The simulation results show the efficiency and the capability of the proposed hierarchical approach, in finding the optimal solution, over the centralized method.     

Minipal4便携X射线荧光光谱仪现场快速测定水系沉积物中多种元素

直接使用粉末样品,用Minipal 4便携式能量色散X射线荧光光谱仪现场测定水系成积物样品中的Cu、Zn、AS、Ba、Ni、Co、Mo、Mn等元素,方法简便、快速,把采到的样品再送到实验室内进行测量,两者的分析结果基本符合;精密度试验结果,除Mo以外,各组分的RSD(n=12)均小于5%,能满足矿山和野外现场快速测定的要求。     

基于化学碰撞理论的绿色模块划分方法

针对在产品设计初期传统绿色模块划分方法普遍存在模块绿色程度区分能力不足的问题,提出了一种基于化学碰撞理论的绿色模块划分方法.首先,构建了化学碰撞理论应用于绿色模块划分模型,模型中,重点探讨了表征零件自身化学反应活性的绿色程度矩阵和表征零件碰撞形成化学键难易的能量矩阵建立过程,在此基础上,通过有效碰撞评估,确保绿色模块组...