Adsorption of Cr(Ⅵ) in wastewater using magnetic multi-wall carbon nanotubes

Magnetic multi-wall carbon nanotubes were prepared with wet chemical treatments and characterized by a transmission electron microscope(TEM) and X-ray diffraction(XRD). They were used as adsorbents for the removal of Cr(VI) in aqueous solutions. The effects of adsorbent dosage, the concentration of Cr(VI) in aqueous solution, temperature, and p H value on the removal efficiency were studied. Results showed that the adsorption capacity of the magnetic multi-wall carbon nanotubes increased with the initial Cr(VI) concentration, but decreased with the increase of adsorbent dosage. The adsorption amount increased with contact time. The adsorption kinetics were best represented by the pseudo second-order kinetic model, and the adsorption isotherms indicated that the Langmuir model better reflected the adsorption process. The obtained calculation results for the Gibbs free energy revealed that the adsorption was a spontaneous and endothermic process. The enthalpy deviation was 3.835 k J·mol 1. The magnetic multi-wall carbon nanotubes showed significant potential for application in adsorption of heavy metal ions.     

Efficient removal of Cr(VI) by tannic acid-modified FeS nanoparticles: Performance and mechanisms

Ferrous sulfide (FeS) nanoparticles constitute an effective hexavalent chromium (Cr(VI)) treatment reagent. However, FeS nanoparticles aggregate easily, significantly limiting their engineering applicability. To overcome this shortcoming and further improve Cr(VI) removal efficiency, this study used tannic acid (TA) to modify FeS nanoparticles. The results demonstrated that TA-modified FeS nanoparticles, TA-nano-FeS, had a significantly reduced tendency to agglomerate, and maintained particle diameters of 10–100 nm, which were much shorter than diameters of FeS nanoparticles. In addition, TA-nano-FeS could combine the surface-active functional groups of TA. The maximum removal capacity of TA-nano-FeS was 381.04 mg/g, which was 2.92 and 1.83 times higher than those of TA and nano-FeS, respectively. Furthermore, the acidic condition was more beneficial for Cr(VI) removal, and the coexisting cations (Ca²⁺ and Mg²⁺) slightly decreased the removal efficiency of Cr(VI). Adsorption, reduction, and co-precipitation were the removal mechanisms, and the reaction products included FeCr₂O₄, Cr₂O₃, Fe₂O₃, Cr(OH)₃, and S₈. The results provided valuable information for the practical application of TA-nano-FeS in Cr(VI) removal.     

零价铁处理水体中Cr（IV）污染研究进展

将零价铁的还原性能作为一种廉价、高效的处理方法对水体的重金属污染进行治理和修复,现已成为一个广受关注的研究领域。然而,诸多应用方式对这一反应的处理效果影响很大。通过查阅文献资料,比较了二元金属体系双电解异位修复含Cr (VI)废水和纳米铁原位修复技术的研究成果,同时整理了近期关于纳米零价铁改性制备的研究情况,分析得到：氧化还原反应过程中生成的Cr-Fe膜是阻断电子在Fe0与Cr2O72-之间传输,限制Cr (VI)去除效果的主要原因;在微电解异位修复中,当进水pH<2,停留时间控制在55-60min,浓度≤100mg/L条件下时, Cr (VI)的去除率可达99%,且运行较为稳定。讨论零价铁处理水体中的Cr (IV)污染,将有利于深入开发更多具有较强适应性的处理工艺和工程应用,更好地解决环境污染的应急处理问题。     

基于MODFLOW的地下水Cr(VI)污染水动力场模拟预测研究

随着社会和经济的快速发展,我国地下水污染问题已日益突出,地下水中Cr(Ⅵ)的污染已成为危害环境和人类健康的危险物质.由于Cr(Ⅵ)的毒性高、易迁移等特点,给地下水环境带来严重的安全隐患.在对某市城区水文地质及工程地质条件进行分析的基础上,依据2005年的资料用Visual Modflow进行参数率定,确定水文地质参数,建立了第四系地下水系统准三维非稳定流模型;再用2005-2009年的资料验证了模型的可靠性,利用此模型进行地下水流场模拟预测,并将现状条件下(2010年)Cr(Ⅵ)污染晕与预测的地下水流场形态进行叠加来预测Cr(Ⅵ)污染晕的发展趋势,为今后当地政府部门应对Cr(Ⅵ)污染地下水治理提供相关政策建议与决策参考,具有重要意义.     

微生物吸附低温水体中Cr(Ⅵ)、Cd(Ⅱ)离子研究

利用从活性污泥中分离、纯化、筛选得到的霉菌,进行吸附水体中Cr(Ⅵ)、Cd(Ⅱ)离子研究。结果表明:在Cr(Ⅵ)、Cd(Ⅱ)质量浓度分别为300mg/L时,菌种生长良好。吸附水体中Cr(Ⅵ)、Cd(Ⅱ)的最佳条件:pH值5.0,时间1h,温度10℃。吸附规律符合Langmuir等温吸附模型,由回归方程得到Cr(Ⅵ)的表观最大吸附量为14mg/g;Cd(Ⅱ)的表观最大吸附量为52mg/g。对菌种吸附低温水体中两种重金属离子时pH值变化影响及其吸附动力学进行了研究。证明该菌可以有效地去除低温水体中Cr(Ⅵ)、Cd(Ⅱ)离子。     

Efficient removal of Cr(VI) by polydopamine-modified lignin from aqueous solution: Batch and XAFS studies

Lignocellulose has the potential to become a bio-based adsorbent due to its biodegradability and renewability. In this study, a novel polydopamine-functionalized-lignin (lignin@PDA), prepared via self-polymerization of dopamine (PDA) on lignin, was used as a bio-based adsorbent for rapid scavenging of hexavalent chromium (Cr(VI)). The morphology, functional groups, crystalline structure, and chemical composition of lignin@PDA were characterized with a scanning electron microscope–energy dispersive spectrometer, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The Cr(VI) adsorption process of lignin@PDA was studied using batch experiments as a function of pH, ionic strength, adsorbent dose, and contact time at room temperature. The adsorption rate of lignin@PDA was five times greater than that of the unmodified lignin, with a maximum adsorption capacity of 102.6 mg/g in an acidic medium. The adsorption of Cr(VI) on lignin@PDA fit the pseudo-second-order equation and the Freundlich model, indicating that the adsorption process was mainly dominated by chemisorption and surface complexation. The thermodynamic parameters showed that adsorption of Cr(VI) on lignin@PDA was an endothermic and spontaneous process. The X-ray absorption fine structure results showed that sorption and reduction of Cr(VI) into Cr(III) occurred simultaneously on lignin. Moreover, PDA coating not only improved the reactivity of lignin but also promoted the complete reduction of Cr(VI) by lignin. According to these results, polydopamine-functionalized-lignin is a promising bio-based adsorbent for immobilization of Cr(VI) from wastewater.

     

利蒙(LLMO)浓缩微生物菌在江西赛得利粘胶化纤废水治理中的应用

研究了利用投加利蒙菌对赛得利污水厂生化池进行改进,以期提高出水的CODC r与SS去除率,稳定出水水质。实验结果表明,利蒙菌在对粘胶化纤废水生化处理上的改进是可行的,对废水中CODC r、SS的平均去除率可比未投加提高56%、44%,其出水水质良好、稳定,其中CODC r<40 m g/L、SS<50 m g/L。     

Removal of copper(II) from aqueous solution using chemically modified fruit peels as efficient low-cost biosorbents

Fruit peels, which are common agricultural byproducts, have been extensively used as abandoned or low-cost biosorbents to remove heavy metals. In this study, dragon fruit peel (DFP), rambutan peel (RP), and passion fruit peel (PFP) were used to remove Cu(II) ions from an aqueous solution. Concentrations of the adsorbed metal ions were determined using the atomic absorption spectroscopic method. Adsorption experiments were performed with different adsorbent dosages, pH values, contact times, and initial copper concentrations. The optimum set of conditions for biosorption of Cu(II) ions was found to be an adsorbent dosage of 0.25 g, a contact time of 180 min, an initial concentration of 100 mg/L, a pH value of 4 for RP and PFP, and a pH value of 5 for DFP. The adsorption conformed with the pseudo-second-order kinetic model. The adsorption data were consistent with the Langmuir and Freundlich isotherm models, but the best fit was with the Langmuir model. The Langmuir monolayer adsorption capacity values of DFP, RP, and PFP were calculated to be 92.593, 192.308, and 121.951 mg/g, respectively. RP showed a higher adsorption capacity of Cu(II) ions than PFP and DFP for all parameters. The results indicate that these biosorbents might be used to effectively adsorb Cu(II) ions from wastewater treatment plants.     

特定污泥对铬(Ⅵ)的吸附容量研究

接种了高效菌种A、B的驯化污泥在前期的生物滤床系统中体现了良好的铬(Ⅵ)去除效率,为了解决系统放大后污泥再生与使用周期等问题,对污泥的铬(Ⅵ)吸附容量进行了测定,测定项目包括一次连续吸附总量、营养添加前后吸附容量的变化等。以铬(Ⅵ)质量浓度为100mg/L的废水进行实验,得到该污泥吸附最佳时间为40min,此时污泥对铬的吸附能力为污泥自身干重的14 94%。一次连续吸附总量为27～28mg/g干污泥。营养液的加入使得污泥吸附能力提高了29 68%。     

壬基酚聚氧乙烯醚(NPEOs)在净水厂中的监测

低浓度内分泌干扰物长期作用会对人体健康产生不可忽视的负面影响.较详细地研究了北方某给水厂现有净水处理工艺对低浓度NPEOs的控制特性,结果表明,该厂常规工艺单元(无预氯化)对NPEOs(聚合度n＝4～15)基本上没有去除作用,后续活性炭单元对NPEOs的去除作用也不是很明显,有待进一步研究.由于氯的强氧化作用的存在,加氯能明显降低水中的NPEOs浓度.     

Biosorption of Ni(Ⅱ) ions from aqueous solution using modified Aloe barbadensis Miller leaf powder

This study aimed to investigate the biosorption potential of Na_2 CO_3-modified Aloe barbadensis Miller(Aloe vera) leaf(MABL) powder for removal of Ni(II) ions from a synthetic aqueous solution. Effects of various process parameters(pH, equilibrium time, and temperature) were investigated in order to optimize the biosorptive removal. The maximum biosorption capacity of MABL was observed to be 28.986 mg/g at a temperature of 303 K, a biosorbent dose of 0.6 g, a contact time of 90 min, and a pH value of 7. Different kinetic models(the pseudo-first-order,pseudo-second-order, Elovich, and intraparticle diffusion models) were evaluated. The pseudo-second-order kinetic model was found to be the best fitted model in this study, with a coefficient of determination of R~2 = 0.974. Five different isotherm models(the Langmuir, Freundlich,Temkin, Dubinin-Radushkevich, and Brunauer-Emmett-Teller(BET) models) were investigated to identify the best-suited isotherm model for the present system. Based on the minimum chi-square value(x~2 = 0 027) and the maximum coefficient of determination(R~2 = 0.996), the Langmuir isotherm model was found to represent the system well, indicating the possibility of monolayer biosorption. The sticking probability(S*) was found to be 0.41, suggesting a physisorption mechanism for biosorption of Ni(II) on MABL. The biosorbent was characterized using Fourier-transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM), zeta potential, and BET surface area, in order to understand its morphological and functional characteristics.     

磁场对厌氧生物处理系统除铬(Ⅵ)效率的影响

研究磁场对2株已知高效除铬菌生长繁殖的促进作用,以及厌氧生物处理系统(ASBR)中添加磁粉对合成含铬废水和实际含铬电镀废水的净化效果的影响。通过试验,确定最佳磁场强度为6.0mT,磁场对微生物作用4h后,表现出对微生物生长繁殖的促进作用。尽管实际废水的处理效果比模拟废水处理效果差,Cr6+、总铬、CODCr达标时间延长了3~5h,但在磁场条件下,厌氧污泥系统处理模拟废水和实际废水至达标排放所需时间分别较不加磁场条件下提前约1h和2~3h。     

水样保存方法及保存时间对黄河水体中总有机碳测定的影响

水环境监测中,对于总有机碳的测量,国内外相关标准和规范对其水样保存条件缺乏统一要求。结合黄河水体的水质特点,重点选择pH值、保存时间、保存温度、前处理和水样浓度5个方面评估水样保存条件对总有机碳测试结果造成的影响。结果表明,在采样后24 h内不能及时测试的水样,必须改进保存方法,使水样的pH值小于2、水样运输及保存过程中以4℃冷藏、样品测试前充分混匀、避光密封保存。     

Efficient degradation of dye pollutants in wastewater via photocatalysis using a magnetic zinc oxide/graphene/iron oxide-based catalyst

In this paper, we present a proof-of-concept study of the enhancement of photocatalytic activity via a combined strategy of fabricating a visiblelight responsive ternary heterostructure and improving overall photostability by incorporating magnetic zinc oxide/graphene/iron oxide (ZGF). A solvothermal approach was used to synthesize the catalyst. X-ray diffraction (XRD), scanning electron microscopic, energy dispersive X-ray, transmission electron microscopic, vibrating sample magnetometric, and ultravioletevisible diffuse reflectance spectroscopic techniques were used to characterize the synthesized samples. The obtained optimal Zn(NO₃)₂ concentration, temperature, and heating duration were 0.10 mol/L, 600 C, and 1 h, respectively. The XRD pattern revealed the presence of peaks corresponding to zinc oxide, graphene, and iron oxide, indicating that the ZGF catalyst was effectively synthesized. Furthermore, when the developed ZGF was used for methylene blue dye degradation, the optimum irradiation time, dye concentration, catalyst dosage, irradiation intensity, and solution pH were 90 min, 10 mg/L, 0.03 g/L, 100 W, and 8.0, respectively. Therefore, the synthesized ZGF system could be used as a catalyst to degrade dyes in wastewater samples. This hybrid nanocomposite consisting of zinc oxide, graphene, and iron oxide could also be used as an effective photocatalytic degrader for various dye pollutants.     

梯级水电开发下黄河上游龙-刘河段DOC时空分布特征及通量研究

针对梯级水电开发影响下河流生源物质循环的科学问题,选取黄河上游梯级开发河段（龙羊峡-刘家峡段,共5个水库）为研究区域,以溶解性有机碳（DOC）为主要研究对象,采用采样监测方法分析DOC以及理化指标的时空分布特征,并且基于静态箱式算法模型估算各水库DOC的输移通量。结果表明：DOC及常规理化指标存在明显的时空异质性,DOC浓度呈现汛期（5.37~7.00 mg/L）高于非汛期（2.90~5.56 mg/L）的特征,汛期由于水库出现垂向水温分层现象,DOC在沿水深垂直方向上呈波动变化。在采样年里,龙羊峡-刘家峡段DOC的年输入通量为258.53 kt,年输出通量为192.23 kt,拦截率为25.6%,具有拦截效应的水库为龙羊峡、公伯峡和刘家峡,其余水库为输送效应。     

颗粒活性炭吸附饮用水中卤乙酸特性研究

采用颗粒活性炭(GAC)对饮用水消毒副产物卤乙酸中的三氯乙酸(TCAA)和二氯乙酸(DCAA)的吸附特性进行了研究和对比。研究结果表明:在单底质条件下,活性炭对卤乙酸的吸附等温线最符合修正的Freundlich方程,浓度小于200μg/L时,活性炭对卤乙酸基本表现为单层吸附。活性炭投加量为1600mg/L时,GAC对TCAA和DCAA的去除率分别达到98.49%和98.01%。活性炭对TCAA的吸附能力高于DCAA,当平衡浓度为0.3μmol/L时,其对二者的摩尔吸附容量比为1.17∶1。酸性条件下有利于活性炭吸附卤乙酸。多底质共存条件下,两种卤乙酸之间存在竞争吸附,与单底质条件下相比,活性炭对TCAA的吸附受影响程度低于DCAA。同时吸附速率比较表明活性炭对DCAA的吸附速率较快。     

PDM复合混凝剂处理春季嘉陵江水的应用研究

通过小试考察了聚二甲基二烯丙基氯化铵(PDM)复配硫酸铝(AS)、氯化高铁(FC)、聚氯化铝(PAC)和聚硫酸铁(PFS)以及单独采用PAC处理某水厂春季嘉陵江水源水的效果,选择了复配比例为1:100的PAC-PDM复合混凝剂处理该时期原水。通过对矾花与沉降性能的研究,发现复配比例越低,投药量越少,矾花粒径越小。当矾花粒径达到0.5 mm以上时,矾花的沉降性能较好,且矾花的沉降性能还与矾花的密实程度有很大关系。通过对PAC和PAC-PDM连续生产对比试验研究,在出厂水满足《生活饮用水卫生标准》(GB 5749—2006)要求的情况下,PAC-PDM和PAC的平均投药量分别约为8mg/L和14.3mg/L,在春季该水厂采用PAC-PDM处理嘉陵江原水较单独采用PAC约节省30%混凝剂费用。     

水热法合成的LaVO4/WO3复合纳米片的可见光光催化还原工业废水中Cr（VI）效果分析

针对工业废水中Cr(Ⅵ)毒性大,迁移性强的问题,采用水热法制备了不同复合比例的LaVO_4/WO_3复合纳米片光催化剂,通过XRD、SEM、XPS和DRS测试手段进行了表征。结果表明:LaVO_4能进入WO_3晶格之中,使其产生晶格缺陷;晶格缺陷可作为活性位点,促进光生载流子的分离,提高WO_3的光催化活性。可见光下光催化还原工业废水中Cr(Ⅵ)测试表明:LaVO_4/WO_3复合纳米片的光催化还原效率比WO_3更高,当LaVO_4以质量比为3%负载WO_3时,复合纳米片光催化还原性最高,可达92%,是纯WO_3还原效率的8.3倍。分析结果表明,LaVO_4能使WO_3的氧空位得到扩散,提高界面光生电子的迁移速率,促进光生电子还原Cr(Ⅵ),提高复合纳米片的光催化还原性能。本研究为重金属工业废水,特别是难降解重金属污染物高效治理技术的研发提供了理论参考。     

Predicting pollutant removal in constructed wetlands using artificial neural networks(ANNs)

Growth in urban population,urbanisation,and economic development has increased the demand for water,especially in water-scarce regions.Therefore,sustainable approaches to water management are needed to cope with the effects of the urbanisation on the water environment.This study aimed to design novel configurations of tidal-flow vertical subsurface flow constructed wetlands(VFCWs) for treating urban stormwater.A series of laboratory experiments were conducted with semi-synthetic influent stormwater to examine the effects of the design and operation variables on the performance of the VFCWs and to identify optimal design and operational strategies,as well as maintenance requirements.The results show that the VFCWs can significantly reduce pollutants in urban stormwater,and that pollutant removal was related to specific VFCW designs.Models based on the artificial neural network(ANN) method were built using inputs derived from data exploratory techniques,such as analysis of variance(ANOVA) and principal component analysis(PCA).It was found that PCA reduced the dimensionality of input variables obtained from different experimental design conditions.The results show a satisfactory generalisation for predicting nitrogen and phosphorus removal with fewer variable inputs,indicating that monitoring costs and time can be reduced.     

Dissolved and particulate organic carbon concentrations in stream water and relationships with land use in multiple-use watersheds of the Han River (Korea)

This study examines temporal variation in dissolved organic carbon (DOC) and particulate organic carbon (POC) concentrations in streams in the Han River watershed, Korea. On days without significant antecedent rain, DOC and POC concentrations ranged from 0.87 to 3.23 mg C/L and 0.24 to 2.92 mg C/L, respectively. Following rain events, both DOC and POC concentrations were higher. Soil and compost had δ¹³C values similar to stream δ¹³C-DOC and δ¹³C-POC. These results demonstrate the importance of studies using tracer approaches and the value of research on sources of organic carbon transported in streams in multiple use monsoonal watersheds.