Study on anaerobic treatment of wastewater containing hexavalent chromium

A self-made anaerobic bio-filter bed which was inoculated with special sludge showed high efficiency in removing hexavalent chromium. When pump flow was 47 ml/min and CODCr of wastewater was about 140 mg/L, it took 4 h to decrease the Cr6+ concentrations from about 60 mg/L to under 0.5 mg/L, compared with 14 h without carbon source addition. Cr6+ concentra- tions ranged from 64.66 mg/L to 75.53 mg/L, the system efficiency was excellent. When Cr6+ concentration reached 95.47 mg/L, the treatment time was prolonged to 7.5 h. Compared with the contrast system, the system with trace metals showed clear supe- riority in that the Cr6+ removal rate increased by 21.26%. Some analyses also showed that hexavalent chromium could probably be bio-reduced to trivalent chromium, and that as a result, the chrome hydroxide sediment was formed on the surface of microor- ganisms.

Pilot study on microbial treatment of high concentration chromium wastewater from cold rolling mills

The microbial treatment of wastewater containing a high concentration of chromium from cold rolling mills was carried out as a pilot study. The pilot-scale equipment, technological process and results are described in this paper. Two kinds of wastewater with a high concentration of chromium were tested ： one from a color coating line ; the other from a silicon steel line. The removal effect of Cr^6＋ , T-Cr and chemical oxygen demand （COD） in wastewater was studied. The results showed that this microbial treatment technology could be used to treat the above two kinds of chromium-containing wastewater. The average concentrations of Cr^6＋ in the color coating line effluent and the silicon steel line effluent were 0.02 mg/L and 0.04 mg/L respectively, and the average concentrations of T-Cr in the effluents were 0.71 mg/L and 0.74 mg/L respectively. Both were lower than the Sewage Discharge Standard （Cr^6＋ 〈 0.5 mg/L,T-Cr 〈 1.5 mg/L）. Furthermore, up to 60% of the COD was removed from chromate wastewater containing a high concentration COD （ 〉 3 g/L）. The removal rate of COD was lower than 25% for chromate wastewater containing a low concentration COD （ 〈 3 g/L）. Adding a flocculating agent was one of the effective ways of improving the COD removal rate from chromium-containing wastewater.

Preparation of Al2O3-Supported Nanoscale FeS Based on High-Gravity Technology and Its Application for Removing Chromium (Ⅵ) in Wastewater

AbstFeS has an excellent performance in removing heavy metal chromium(Ⅵ)in wastewater due to its good adsorption and reduction.The properties of easy aggregation and oxidization of nano-FeS,however,limit the applications of FeS in engineering.In this study,one FeS adsorbent supported by Al_(2)O_(3) was prepared using high-gravity technology in IS-RPB(Impinging Stream Rotating Packed Bed)to overcome polymerization and oxidation of nano-FeS.Experimental results showed that FeS was uniformly loaded on the surface and pores of Al_(2)O_(3).The specific surface area of FeS/Al_(2)O_(3) is 125 m2·g^(-1) which is nearly 1.6 times that of pure FeS.The adsorption capacity of FeS/Al_(2)O_(3) for chromium(Ⅵ)is 200 mg·g^(-1),1.4 times that of pure FeS.pH value and ionic strength are strongly correlated with the chromium removal performance of FeS/Al_(2)O_(3).Over 98%of chromium can be removed when pH values of FeS/Al_(2)O_(3) ranged from 4 to 6.Higher adsorption capacity is achieved with higher ionic strength in FeS/Al_(2)O_(3).The FeS/Al_(2)O_(3) maintained more than 95%of the adsorption capacity after being preserved for one month,but only 70%for pure FeS.The removal processes of chromium(Ⅵ)conformes to a pseudo-second-order kinetic model(R2≥0.9986),indicating that the rate-limiting step is a chemical sorption process instead of a mass transfer.

Removal of arsenic from acid wastewater via sulfide precipitation and its hydrothermal mineralization stabilization

To achieve a safe treatment of arsenic-containing acid wastewater,a new process was proposed,including arsenic removal via sulfide precipitation and hydrothermal mineralization stabilization.Under optimal conditions of sulfide precipitation,99.65%of arsenic from wastewater was precipitated in the form of amorphous As2S3.The As leaching concentration of amorphous As2S3 in TCLP(toxicity characteristic leaching procedure)test was up to 212.97 mg/L,therefore,hydrothermal mineralization was adopted to improve the stability of amorphous As2S3.The results showed that the As leaching concentration of mineralized As2S3 was only 4.82 mg/L.Furthermore,the amorphous As2S3 could be transformed into crystallized As2S3(orpiment)in the presence of mineralizer Na2SO4.Simultaneously,the As leaching concentration of crystallized As2S3 was further reduced to 3.86 mg/L.Hydrothermal mineralization was an effective method for the stabilization of As2S3.Therefore,this process has a greater application in the treatment of arsenic-containing wastewater.

Removing contaminants from tannery wastewater by chemical precipitation using CaO and Ca(OH)2

The removal of Cr,sulfates and Chemical Oxygen Demand(COD)from industrial tannery wastewater by chemical precipitation was carried out using Calcium oxide(CaO)and Calcium hydroxide(Ca(OH)2).Different doses of alkalis,ranging from deficiency to excess hydroxyl species over the stoichiometric necessary,were used to remove theoretically the 100%of Cr[0.3-3.2 g alkali·(g Cr^3+)^-1].The precipitation was carried out at room temperature,10 min of vigorous stirring,200 r·min^-1 and a settling time of 24 h,followed by separation and characterization of liquid product.As result of addition of alkalis,pH underwent increase as did the alkali concentration.The removal of Cr,and sulfates also increased as alkali concentration did,although for first species the changes at higher alkali contents were less evident.COD removal on the other hand,did not follow a unique trend,instead exhibited a maximum.Based on our results,selection of a specific dose of alkali was carried out taking as reference the efficiency on total chromium removal,keeping the pH in the range 7 to 9 to ensure Cr precipitation as chromium hydroxide.With those conditions,jar test was used to produce enough liquid product in order to determine the removal percent of several other species.The removal percent of the species was as follows:Cr,SO4^2-,ZnSO4,FeSO4,CN^-1,NiSO4,Fe2[Fe(CN)6]at 99.8%,66.9%,99.6%,21.4%,70.9%,52.8%and 76.4%with CaO,and 99.8%,61.6%,99.9%,7.1%,84.0%,54.4%and 90.5%with Ca(OH)2,respectively.

Removal of Some Toxic Ions from Seawater and Wastewater by Sorption onto Natural, Synthetic Hydroxyapatite and Alginate-Hydroxyapatite Composite Nanoparticles: A Comparative Study

The main objective of this paper is to study the removal of Cadmium(II), Lead(II), Chromium(VI), and Mercury(II) ions by sorption onto different natural and synthetic nanoparticles. Special attention has been given to the application of fish bone in nanoform as a useful, inexpensive and eco-friendly alternative material. A comparison between natural hydroxyapatite (fish bone), synthetic hydroxyapatite nanoparticles (HAP) and alginate-hydroxyapatite composite (Alg/Hap) to assess their removal efficiencies to remediate the selected heavy metals has been done. Surface characterization by using different techniques has also been performed to understand the influence of surface characteristics of the adsorbent materials in the removal process. Different parameters (pH, contact time, mass dose and metal ion concentration) have been examined to identify the optimum conditions for remediation of different metals from polluted water. The potential applications of the biosorbents for removal and sorption of these metal ions from seawater and wastewater samples were also investigated and evaluated.

Microwave-assisted Fenton-like decolorization of methyl orange solution using chromium compounds

Azo dyes discharged in the environment are persistent organic pollutants （POPs）, which are very difficult to remove. We developed a microwave-assisted Fenton-like process to degrade methyl orange （MO）, an azo dye, with hydrogen peroxide （H2O2） catalyzed by chromium compounds coexisting with MO in the solution. Comparison between the Cr（Ⅲ）-H2O2 and Cr（Ⅵ）-H2O2 systems shows＂ that Cr（Ⅵ） has a stronger and more stable catalytical activity than Cr（Ⅲ）, and Cr（Ⅲ） is more susceptible to a change in the acidity or alkalinity of the reaction system. With a Cr（Ⅵ） concentration of 10 mmol L^-1 or a Cr（Ⅲ） concentration of 12 mmol L^-1 in the solution under the microwave irradiation of a power larger than 300 W for 3 min, 10 mmol L^-1 H2O2 can degrade more than 95% of 1 000 mg L^-1 methyl orange; when the microwave power is increased to 700 W, the same amount of H2O2 can degrade all methyl orange in the solution with the same amount of Cr（Ⅵ ） catalyst. Ultraviolet-visible spectrography indicates the cleavage of the azo bond in methyl orange after treatment, suggesting the potential o of this Fenton-like process to degrade azo dye POPs. Reusing waste chromium compounds coexisting with dyestuff in wastewater to catalyze the degradation of azo dyes could be a cost-effective technique for azo dyes and chromate manufacturers and/or users to treat their wastewater and prevent POPs from endangering the environment. This is of particula importance to controlling the water quality of the Three Gorges Reservoir.

Soil Explorations and Groundwater Monitoring to Evaluate Subsurface Contamination Due to Chromium in District Kasur, Pakistan

Due to improper tannery wastewater management in district Kasur Pakistan, groundwater has been reported to be highly contaminated. It was aimed to find out the extent up to which subsurface has contaminated due to chromium in areas adjacent to the tannery units. Eight （8） soil bores were conducted up to the depth of 30.5 meters and soil samples were tested for total and hexavalent chromium concentrations retained in soil by aqua regia digestion at the every depth of 1.5 meters. Afterwards monitoring wells were installed in these eight （8） bores so as to monitor chromium concentrations in the groundwater on monthly basis. The main source of contamination was considered to be the four （4） drains carrying tanneries effluent therefore samples were collected from these drains so as to observe seasonal variation in chromium concentration.

综合法二氧化氯生产系统废水除铬实例

以某浆纸厂含铬废水处理工程实例为研究对象,针对综合利用自产化学药品和现有设备开发的间歇性六价铬(Cr^(6+))综合处理系统,探讨了二氧化氯车间Cr^(6+)废水产生原因及性质,根据不同的反应池pH值、反应温度、反应时间和硫磺投加量对废水中Cr^(6+)还原效果的影响,确定了二氧化硫还原法去除Cr^(6+)的最佳反应条件,并结合实际生产数据,展示了Cr^(6+)还原效果。结果表明,有效去除高浓度含铬废水中Cr^(6+)的条件为:pH值=2~4、反应温度控制在40~60℃、硫磺投加量为理论反应所需投加量的1.4~1.6倍、反应时间40 min。3次二氧化氯车间停修废水出水中Cr^(6+)含量均低于0.005 mg/L,总铬含量均低于0.06 mg/L,符合《污水综合排放标准》(GB 8978—1996)中的要求,证实了间歇性Cr^(6+)综合处理系统处理的有效性。

粉煤灰负载纳米FeS处理酸性含铬废水动态试验

针对矿区生态环境受酸性含铬废水污染严重的问题,采用超声沉淀法制备了粉煤灰负载纳米FeS吸附材料(nFeS-F)。并以粉煤灰、nFeS-F为填料分别构造1^(#)、2^(#)动态柱,进行酸性含铬废水动态处理试验,通过XRD、SEM、TEM、XPS对粉煤灰、nFeS-F进行表征,探究粉煤灰和nFeS-F处理酸性含铬废水的规律性、长效性和去除机理。结果表明:在进水Cr(Ⅵ)浓度为100 mg/L条件下,动态柱运行28 d内,1^(#)柱对Cr(Ⅵ)和总铬的平均去除率分别为42.86%和36.65%;2^(#)柱对Cr(Ⅵ)和总铬的平均去除率分别为70.74%和53.12%,至试验结束时,1^(#)柱和2^(#)柱的pH分别为5.50和6.38。通过nFeS-F的XRD、XPS表征分析表明,Cr(Ⅵ)被还原为Cr(Ⅲ),并以氢氧化物和硫化物沉淀的形式固定在nFeS-F的表面上。nFeS-F对Cr(Ⅵ)表现出优异的吸附性能,该研究可为处理酸性含铬废水提供一定的技术参考。

华北平原制革废水Cr(Ⅲ)和氨氮在典型包气带中迁移模拟与污染评价

【研究目的】为探明制革废水中的特征污染物铬(Cr(Ⅲ))和氨氮(NH_(4)^(+)–N)在华北平原典型包气带中的迁移规律,评价其可能产生的土壤与地下水污染风险。【研究方法】采用土柱淋滤实验研究Cr(Ⅲ)和NH_(4)^(+)–N在典型粉土中的吸附和迁移转化特征,结合Hydrus–1D建立的包气带水流和溶质运移模型,模拟预测深0.5 m渗坑中NH_(4)^(+)–N连续入渗状态下通过包气带到达地下水面所需时间及不同深度浓度值的变化规律。【研究结果】在3 cm定水头,污染液(Cr(Ⅲ)20 mg/L,NH_(4)^(+)–N 250 mg/L)定浓度持续淋滤120 d的情况下,Cr(Ⅲ)在土柱中垂向迁移距离小于10 cm,且以残渣态(73%)为主,未检出Cr(VI)。NH_(4)^(+)–N则迁移能力较强,淋滤40 d后即穿透50 cm厚粉土柱。在高含盐量(电导率为10.08 ms/cm)条件下,NH_(4)^(+)–N在粉土中的迁移主要受吸附作用控制,土-水分配系数为25.87 L/kg,未发生硝化作用。持续淋滤150 d时NH_(4)^(+)–N迁移至地下水面(18 m埋深)且浓度超过Ⅲ类地下水质量标准(0.5 mg/L,GB/T 14848–2017),在223 d完全穿透包气带,严重污染地下水。【结论】高含盐量制革废水中Cr(Ⅲ)在粉土中迁移能力较弱,且难以被氧化为Cr(Ⅵ),对地下水威胁较小。NH_(4)^(+)–N则随水流快速迁移至地下水面,严重威胁地下水安全。

含铬废水和污泥中铬的处理研究进展

随着“绿色发展”观念的持续推进,传统制革行业因其生产工艺中产生的污染而逐渐受到冲击。制革鞣制过程所产生铬鞣废水及其处理后所产生的污泥,若得不到有效处理和利用,不仅会对环境和人的身体健康产生危害,还会造成铬资源的大量浪费,经济、高效的铬处理与利用技术的开发已迫在眉睫。基于此,分别对制革过程产生的含铬废水及其沉淀过程产生的污泥中铬的处理方法进行了介绍,如循环利用法、电絮凝法、生物沥滤法和超临界水氧化法等,并对含铬废水和污泥中铬的处理回收方法的发展进行了总结和展望,旨在为我国皮革行业的绿色化发展提供一种新的思路。

基于物联网的电镀铬镍混合废水浓度监控系统

监测废水中的铬和镍浓度有助于早期发现和处理潜在的问题,减少对自然环境和水资源的污染风险。为此,设计了基于物联网架构的电镀铬镍混合废水浓度监控系统。在指挥层中使用LoRaWAN通信方式连接电化学传感器和监控系统,监控系统可以实时采集废水中的铬和镍浓度数据。在网络层中使用箱线图对指挥层中采集的数据进行异常值识别,并去除这些异常值。为保证数据的安全性和稳定性,通过物联网技术中的监控系统软件协议代码将数据传输至云平台。在云平台中利用孤独森林算法对传输到云平台的数据进行模式识别和监测,通过感知层将废水浓度数据以可视化的形式展示出来,使用户能够直观地了解混合废水的浓度情况。实验结果表明,本文系统的监测准确度保持在95%以上,且数据传输效率保持在96%以上,具有较高监测准确度的同时具有良好的运行性能。

以不同磷源制备的磷掺杂g-C_(3)N_(4)光催化剂的表征及在降解含铬电镀废水中应用的初步研究

[目的]对环境有严重污染的电镀含铬废水需处理后才能排放。[方法]以尿素为原料,采用不同磷源(焦磷酸、正磷酸、亚磷酸和次磷酸),通过热缩聚法和液相蒸发法合成含氮空位的磷掺杂多孔石墨相氮化碳(g-C_(3)N_(4)),通过X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、比表面(积)分析仪(BET)、X射线光电子能谱仪(XPS)、透射电镜(TEM)、扫描电镜(SEM)、紫外−可见分光光度计(UV-Vis)和电化学测试方法对该材料进行表征,评价其对六价铬的光催化降解性能。[结果]使用正磷酸作为磷源得到的磷掺杂g-C_(3)N_(4)降解还原六价铬的效率约为本征态g-C_(3)N_(4)的12.65倍。[结论]在氮空位、氰基和磷元素存在的情况下,磷掺杂g-C_(3)N_(4)的能带结构发生改变,电荷转移加快,展现出良好的光催化反应活性。

基于分类处理-分质利用的电子电镀废水中金属离子资源化处理新技术研究进展

随着城市化、工业化以及农业现代化进程加快,电子信息行业快速发展的同时产生了大量电子电镀重金属废水。这类型废水成分复杂、赋存稳定、危害极大且具有一定资源属性,目前较流行的混凝沉淀法处理效果不佳,污泥量大,存在二次污染且无法资源化回收。基于此,归纳总结了电子电镀重金属废水的来源与危害,归纳分析了现行主要技术存在的不足,系统介绍了基于分类处理-分质利用的电子电镀废水中金属离子资源化处理的进展与最新研究成果,为电子信息行业清洁生产、重金属废水污染防治和资源化处理提供借鉴与技术支撑。

预氧化法制备棉花秸秆活性炭去除印染废水中的铬(Ⅵ)

以新疆南疆棉花秸秆为原料,采用H_(2)SO_(4)预氧化和KOH活化制备活性炭,其Langmuir比表面积达到1 580.94 cm^(2)/g。采用静态吸附试验研究活性炭对印染废水中铬(Ⅵ)的吸附性能。结果表明:p H为2,Cr(Ⅵ)的初始质量浓度为0.5 mg/L,活性炭投加量为0.1 g,吸附时间为150 min时,Cr(Ⅵ)的吸附量为28 mg/g。Langmuir吸附等温线能更好地描述棉花秸秆活性炭吸附Cr(Ⅵ)的过程,R^(2)为0.988 24,说明棉花秸秆活性炭的表面Cr(Ⅵ)主要以单分子层形态吸附。活性炭对铬(Ⅵ)的吸附符合准二级动力学模型,R^(2)为0.950 25。

Bi_(2)S_(3)/NiS复合催化剂光催化还原Cr(VI)的研究

通过水热法制备了一种新型Bi_(2)S_(3)/NiS复合光催化剂,采用FT-IR、XRD、SEM、固体荧光和固体紫外等光谱对催化剂的组成、结构、形貌和光学性质进行了表征.Bi_(2)S_(3)/NiS复合催化剂在可见光照射下能有效将溶液中的Cr(VI)光催化还原为Cr(III).在最优条件下,复合催化剂的反应速率常数约为Bi_(2)S_(3)或NiS的反应速率常数的10倍.复合催化剂光催化还原Cr(VI)效率的提高主要是因为Bi_(2)S_(3)和NiS的复合降低了禁带宽度,扩大了光吸收范围,并且复合后有效降低了光生载流子的复合效率.催化剂循环实验表明Bi_(2)S_(3)/NiS复合催化剂具有良好的光学稳定性.研究结果为光催化处理含Cr(VI)废水的材料合成和设计研究提供了参考.

Fractionational and structural characterization of lignin and its modification as biosorbents for efficient removal of chromium from wastewater:a review

The removal of chromium(Cr)from wastewater by various adsorbents has been investigated.As compared with the commercial activated carbon,the biosorbents with inexpensive and high adsorption capacities are developed from lignocellulosic wastes.Lignin,existing in lignocellulosic biomass,is the second most abundant resource in nature.Recently,lignin-based bio-sorbents were served as an advanced novel material for the metal ions and dye adsorption from wastewater.It has showed several advantages in the wastewater treatments because of the lowcost,high adsorption capacity,easy recover,and possibility of metal recovery.In this review,the isolation of lignin from lignocellulosic biomass was summarized,and the structural characteristics of lignin were comparably analyzed.The modification of lignin was performed to obtain a large surface area,strong binding-site,and high and quick adsorption properties of lignin-based adsorption materials.The adsorption efficiency of Cr ions was found to be strongly dependent on the pH of the wastewater.To further illustrate the adsorption process,the structural changes and the interactions between the metal ions and the functional groups of the lignin-based biosorbents in the adsorption process should be further investigated.Once the cost-effective and high-efficiency modification techniques are developed,lignin-based adsorbents can be expected to be the most suitable alternatives for Cr ions removal from wastewater in industry.

不同还原剂处理含铬废水的效果和成本对比分析

电镀废水中含铬废水的处理一直以来都是企业在污水处理系统中的重点工艺部分,化学还原沉淀法作为含铬废水的处理方法目前被广泛应用。本文针对电镀行业产生的含铬废水,采用四种不同的还原剂进行处理,通过对比实验,研究不同还原剂处理含铬废水的最佳反应条件以及去除效果和综合成本对比。研究发现,结合药剂成本和污泥成本,在总铬标准控制没那么严格的情况下,宜选用焦亚硫酸钠来作为还原剂来处理含铬废水,如果对总铬的排放标准较为严格,可以采用硫酸亚铁作为还原剂来处理含铬废水。

山羊皮加工废水处理工艺设计

开封市某皮革企业年加工山羊皮600万张,从事由毛皮到成皮的全流程生产。厂区建有1座污水处理站,主要包括含铬废水预处理单元、含硫废水预处理单元和综合废水处理单元。结合污水处理站的设计规模和进出水水质,分析废水处理的工艺流程和主要设计参数,从而指导类似企业有效降低投资和运行成本,提高经济效益和环境效益。