浅谈铁氧体法处理电镀含铬废水

铁氧体法是化学法处理电镀含铬废水中较为实用的一种方法。介绍了铁氧体法处理含铬废水的基本原理,一般工艺流程、间歇式工艺流程与连续式工艺流程,以及主要技术参数,包括硫酸亚铁的投加量和投加方式、氧化还原反应时间、不同阶段废水酸碱度的控制、加热温度的控制以及通气量。提出了铁氧体法处理电镀含铬废水今后研究的重点。     

螯合沉淀法处理含铬电镀废水

以NaHSO3为还原剂,新型重金属离子捕集剂DTCR为螯合剂,采用螯合沉淀法处理含铬电镀废水。研究了还原剂投加量、还原反应阶段的废水pH、螯合剂投加量、絮凝剂(PAM)投加量、螯合沉淀阶段的废水pH和搅拌时间对处理效果的影响。还原反应的较优工艺为:NaHSO3200mg/L,废水pH1.84,搅拌时间30min。螯合沉淀的最佳工艺条件为:DTCR70mg/L,PAM8mg/L,废水pH8.0,搅拌时间40min。采用最佳螯合沉淀工艺处理含铬电镀废水时,总铬去除率在95%以上,出水总铬为0.14mg/L,且未检测到其他重金属离子,可达标排放。     

铝型材生产含铬废水处理工艺研究

为使铝型材生产产生的含铬废水的处理出水达到Cr6+≤0.5 mg/L要求,分别选用Na2SO3和Na2S2O5进行还原沉淀处理,并对影响处理效果的因素进行了分析比较。结果表明,还原处理铝型材生产产生的含铬废水时,Na2S2O5的投加量可比Na2SO3减少25.0%～37.5%;处理过程中,应控制混凝沉淀pH为8.2～9.0、PAM投加量为0.010g/L、沉淀时间为1~2 h。     

混凝法处理含铬废水的工艺条件研究

采用混凝沉淀工艺处理含铬废水,考察了还原反应pH值、还原剂投加量和反应时间对六价铬去除效果的影响,以及PAM投加量对混凝反应的影响,试验优化了还原反应和混凝反应条件,并将研究结果应用于实际含铬电镀废水处理。工程运行结果表明,六价铬还原反应的最佳条件为:pH值为2~3,六价铬与还原剂的质量比为1∶5,反应时间为20 min;混凝剂PAM的最佳投加量为8 mg/L,出水中总铬的质量浓度低于0.005 mg/L。     

化学实验室含铬废液的快速检测与回收利用的探讨

研究了在二苯基碳酰二肼显色剂中加入硫酸和磷酸对实验室含铬废液中铬量的测定,并选择还原—沉淀—氧化法对实验室含铬废液进行了处理,由制得的产品及其回收率可见该方法起到了环境保护、废物回收及综合利用的目的。     

焦亚硫酸钠处理电工钢含铬涂层废液的工艺研究

电工钢表面的涂层大多为半无机涂层，涂液中含有剧毒的六价铬，在涂层机清洗和涂层切换过程中，会产生一定量的含铬涂层废液，废液具有六价铬含量高和成分复杂的特点。为使该废液中六价铬能够还原彻底，并且防止处理试剂过量添加，采用焦亚硫酸钠作为还原剂对电工钢含铬涂层废液进行处理，分别对pH、焦亚硫酸钠添加方式和反应时间对六价铬处理效果的影响作出了研究。结果表明，六价铬还原过程的最佳pH为1.8～2.0；焦亚硫酸钠添加方式以溶液ORP（氧化还原电位）控制，当溶液ORP小于400 mV时即可停止添加焦亚硫酸钠；搅拌反应40 min使六价铬与焦亚硫酸钠完全反应，即可满足处理后六价铬质量浓度小于0.05 mg/L的处理要求。     

ORP自控技术在处理含铬废水中的应用

ORP 自控技术处理含铬废水时,还原六价铬所需的氧化还原电势的设定,不能照抄文献数据,而必须根据含铬废水的组分,确定正确的电势值。     

活性炭处理含铬废水的方法

活性炭具有优良的吸队性和还原性，已广泛用于废水处理工业，阐述了活性炭处理含铬废水的基本原理，采用吸附－还原联用处理含铬废水，介绍了其工艺流程、特点及处理过程中的注意事项。实践证明，经处理的废水中六价铬含量达国家排放标准。     

含铬废水还原处理的条件及效果研究

研究了硫酸亚铁、亚硫酸氢钠、亚硫酸钠、焦亚硫酸钠4种还原剂处理含铬废水时的还原性能,用吉布斯自由能分析了pH值对还原效果的影响.通过试验确定最佳加药量.用硫酸亚铁和亚硫酸氢钠调试含铬废水,最后选用亚硫酸氢钠还原剂.     

抽屉窑还原气氛的自动控制

国内间歇式抽屉窑的自动控制都是采用开环控制的方式，在氧化阶段较易实现温度、气氛的自动控制，在还原阶段能实现温度的自动控制，但对气氛无法进行真正的自动控制。针对抽屉窑还原气氛自动控制的问题，我们对窑炉控制系统、执行机构、控制方式进行了设计和改造，实现了抽屉窑在还原阶段温度、气氛都能进行自动控制，在技术上达到了国内先进水平。     

钒铬还原渣酸浸液中钒铬初步分离工艺

钒铬还原渣是钠化提钒过程的典型危险固体废弃物,其资源化利用需求迫切。中国科学院过程工程研究所提出钒铬还原渣硫酸酸解-钒铬初步分离-铬/钒/铁络合深度分离技术路线,并在攀钢集团建成万吨级示范工程。本文重点考察钒铬还原渣酸解液中钒铬初步分离原理及工艺,研究了H₂O₂和Na₂S₂O₈两种氧化剂对沉钒效果的影响,并通过实验确定了最佳工艺条件。结果表明：以H₂O₂为氧化剂时,H₂O₂与钒摩尔比为0.75、氧化温度为60℃、初始溶液pH为2.0、氧化时间为60min、水解温度为95℃、水解时间为2.5h的条件下可得到84.2%的沉钒率;以Na₂S₂O₈为氧化剂时,Na₂S₂O₈与钒摩尔比为0.65、氧化温度为90℃、氧化时间为45min、沉钒初始溶液pH为2.5、沉钒温度为90℃、沉钒时间为2.5h的条件下可获得93.1%的沉钒率。过硫酸钠氧化过程温和,沉钒率高,铬损失小,更适合工业推广应用。采用SEM获得了沉淀产物的微观形貌,煅烧后得到V₂O₅产品,采用XRF获得了产品组成,通过X射线衍射确定得到的V₂O₅产品为正交晶型。     

Electrolytic removal of hexavalent chromium from aqueous solutions

The removal of hexavalent chromium from a synthetic solution and from an industrial sample by electrolysis using stainless steel plate and titanium mesh cathodes is studied. It is found that the process proceeds in two steps: (1) electroreduction of hexavalent chromium to trivalent chromium in highly acidic medium and (2) electrochemical precipitation of trivalent chromium in an alkaline medium. A comparative study of electroreduction, electrochemical reduction and chemical reduction of hexavalent chromium is carried out and the electroreduction process is shown to be a clean technique. It is concluded that, in the absence of addition of any chemical as reducing agent, the Cr(III) solution formed on the reduction of Cr(VI) can be recycled in other industrial processes. Copyright © 2003 Society of Chemical Industry     

镀铬废水中铬的回收及其应用

介绍了用离子交换法处理含铬废水的离子交换柱的洗脱液中Cr6 的处理方法。该处理方法为:洗脱液中的Cr6 经还原处理为Cr3 ,用化学沉淀法和絮凝法将其转化为Cr(OH)3沉淀,经硫酸酸化,结晶为高纯硫酸铬,作为一种铬鞣剂,应用于皮革工业的鞣革,取得了良好的效果。     

Reduction of hexavalent chromium using polyaniline films. Effect of film thickness, potential and flow velocity on the reaction rate and polymer stability

Reduction of very toxic hexavalent chromium (Cr(VI)) to its trivalent state (Cr(III)) is necessary to facilitate the treatment of wastewater by precipitation or adsorption. The present study proposes the use of thin films of polyaniline on a conducting substrate for this purpose. The reduction rate of hexavalent chromium and the degree of degradation of the polyaniline film were studied as a function of the solution flow velocity, applied potential and film thickness. The reduction rate was significantly affected by the flow velocity, while the film thickness was observed to have little effect. The potential had no effect on the reduction rate within the range studied. The current efficiency was 100% in all experiments and no significant degradation of polyaniline was observed.     

还原-氧化-碱性沉淀-重捕-铁碳法处理电镀废水

结合含氰、含铬、酸洗电镀废水的特点,采用氧化法破氰;6价铬还原,碱性沉淀后,加入重金属捕集剂反应,再利用铁碳还原法进一步降低废水中的重金属含量,达到深度去除重金属的目的;采用接触氧化法降解污水中的有机污染物,各级沉淀池的污泥通过静水压定期排入集泥池,然后通过机械压滤后作无害化处理.运行结果表明,该工艺处理效果稳定可靠,...     

Effect of preparation method on structure and catalytic activity of Cr-promoted Cu catalyst in glycerol hydrogenolysis

Relationships between surface structure and catalytic properties were investigated for a series of copper chromium catalysts. The catalysts were prepared using methods involving impregnation and precipitation, and their catalytic activities were evaluated for the hydrogenolysis of glycerol. Catalyst (10I and 50I) prepared by the impregnation method contained a mixed phase of both individual copper and chromium oxide structures, while the catalyst (50P) prepared by precipitation showed a single phase, with a copper chromite spinel structure (CuCr₂O₄). XPS data indicated that, after the reduction step, the copper species in the impregnated catalyst was reduced to Cu⁰, but the catalyst prepared by the precipitation method retained a spinel structure evidenced by the large amount of Cu²⁺ species. In hydrogenolysis reactions, the precipitated catalyst showed a higher catalytic activity than the impregnated catalyst. Thus, the reduced copper chromite spinel structure, which constitutes a single phase, appears to be responsible for the high catalytic activity in the hydrogenolysis of glycerol to propylene glycol.     

制革废水中铬的形态及其沉淀过程研究进展

在制革过程中,有机络合态的铬是主鞣段和复鞣染色段废水中铬的主要赋存形态。在主鞣废水中,主要存在低分子有机酸及胶原水解产物的铬络合物,除了具有强稳定性的多元有机酸外,传统的蒙囿剂及胶原水解产物不会影响铬的碱沉淀去除效果。染整工段废水中的铬与该工段的各类皮革化学品形成络合物,其主要以水溶性、憎液溶胶以及颗粒物等多种形式存在,其中,水溶性铬-有机物络合物主要以阴离子型存在,通常的加碱沉淀法很难将其有效去除。系列研究表明,探索制革染整废水中水溶性阴离子铬配合物的去除是制革含铬废水脱铬的关键。     

沉钒废水除硅制备冶金级氢氧化铬研究

研究了以石灰为脱硅剂,采用石灰+片碱（氢氧化钠）沉淀法脱除沉钒废水中的硅,以除硅液为原料制备冶金级氢氧化铬。结果表明,先用石灰调节pH为7.5~8.0,再用片碱调节pH为9.5以上,除硅温度为55~65 ℃,除硅时间为20~30 min,在此条件下除硅率达到67.9%。沉钒废水用石灰除硅后制备的氢氧化铬硅含量低,以二氧化硅质量分数计达到4.2%,可用于冶炼焊剂用、铝剂用金属铬的原料。     

Reticulated ceramic foams from alumina-chromia solid solutions: A feasibility study

Open cellular ceramic foams were manufactured from plain and chromia-doped alumina, with a chromium concentration ranging between 1.25 mol% and 5.0 mol%. The (AlCr)₂O₃ starting powders were prepared by precipitation of a chromia precursor onto the surface of an alumina powder and subsequent calcination. Characterization of the starting powders as well as the foam samples made therefrom were carried out with respect to the chromium concentration in the alumina phase and the influence of the dopant on the cellular structure and sintering behavior of the doped material. While no positive effect on the compressive strength of the ceramic foams was found, the dopant influences the sintering behavior resulting in an increased shrinkage and in a reduction of total porosity.     

三氯化铁蚀刻废液中铬离子去除的研究

研究磷酸盐沉淀法去除三氯化铁蚀刻废液中铬离子的工艺过程,实现三氯化铁再生利用。主要考察沉淀剂磷酸钠使用量、反应温度、溶液pH、搅拌速度等因素对溶液中铬去除率、铁损失率的影响。结果表明,该方法处理效果好,能有效降低溶液中的铬浓度,铬去除率为97.97%,铁损失率为7.25%。