The coupling of sand with ZVI/oxidants achieved proportional and highly efficient removal of arsenic

• Simply doping sands with ZVI achieved an even activation of ZVI by oxidants. • Sand doping facilitated proportional As trapping along the ZVI/oxidants column. • ZVI/sand/oxidants are highly efficient for arsenic removal. • ZVI/sand/oxidants reduced significantly the Fe²⁺ leaching and effluent turbidity. • More than 54% of arsenic was reduced to As(III) in ZVI/sand/oxidants system. The coupling of zero-valent iron (ZVI) with common oxidants has recently achieved very rapid and highly efficient removal of Heavy metals from wastewater. However, the uniform activation of ZVI throughout the column and the proportional removal of target contaminants are urgently required for the prevention of premature filter clogging and the extension of the effective column operational time. In this study, we successfully achieved this objective by simply doping granular sand with ZVI at appropriate weight ratios. When pure ZVI packed column was spiked with oxidants, the majority of As trapping occurred between the column inlet and the first sampling point. In a packed column with a 1:20 mixture of ZVI and sand, the average As removal efficiency was 36 (1st), 13.1 (2nd), 18.5 (3rd), 19.2 (4th) and 5.9% (5th outlet). The overall arsenic removal performance of the composite filling system of ZVI/sand was equally as efficient as that of the previous pure ZVI-packed system. Moreover, the leaching of Fe was significantly reduced with an increased sand ratio, resulting in clearer water with less turbidity. The results of X-ray photoelectron spectroscopy (XPS) demonstrated that more than 54% of the arsenic was reduced to As(III). X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the extensive corrosion of the ZVI surface, which resulted in various species of iron oxyhydroxides responsible for the highly efficient sequester of arsenic through reduction, adsorption, and coprecipitation.     

Diphenylarsinic acid sorption mechanisms in soils using batch experiments and EXAFS spectroscopy

• DPAA sorption data was found to fit the Freundlich equation. • K_f was significantly positive correlated with oxalate-extractable Fe₂O₃. • Ligand exchange was the main mechanism for DPAA sorption on soils. • Bidentate binuclear and monodentate mononuclear DPAA bonds were identified. Diphenylarsinic acid (DPAA) is a phenyl arsenic compound derived from chemical warfare weapons. Macroscopic and microscopic work on DPAA sorption will provide useful information in predicting the partitioning and mobility of DPAA in the soil-water environment. Here, batch experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy were used to investigate the sorption mechanisms of DPAA. The DPAA sorption data from 11 soil types was found to fit the Freundlich equation, and the sorption capacity, K_f, was significantly and positively correlated with oxalate-extractable Fe₂O₃. The K_f values of eight of the 11 untreated soils (1.51–113.04) significantly decreased upon removal of amorphous metal (hydr)oxides (0.51–13.37). When both amorphous and crystalline metal (hydr)oxides were removed from the untreated soils, the K_f values either decreased or slightly increased (0.65–3.09). Subsequent removal of soil organic matter from these amorphous and crystalline metal (hydr)oxide-depleted samples led to further decreases in K_f to 0.02–1.38, with only one exception (Sulfic Aquic-Orthic Halosols). These findings strongly suggest that ligand exchange reactions with amorphous metal (hydr)oxides contribute most to DPAA sorption on soils. EXAFS data provide further evidence that DPAA primarily formed bidentate binuclear (²C) and monodentate mononuclear (¹V) coring-sharing complexes with As-Fe distances of 3.34 and 3.66 Å, respectively, on Fe (hydr)oxides. Comparison of these results with earlier studies suggests that ²C and ¹V complexes of DPAA may be favored under low and high surface coverages, respectively, with the formation of ¹V bonds possibly conserving the sorption sites or decreasing the steric hindrance derived from phenyl substituents.     

中国突发环境事件时间序列分析

突发性环境事件时间序列特征可表征环境风险管理成效及存在问题。研究表明2000年以来中国突发环境事件预防、控制与管理取得了显著成效,其中,突发性水污染事件、大气污染事件以及噪声振动危害年发生频次呈大幅度降低趋势,但固废污染事件自2003年以来的年发生频次变化不大,而其它突发性环境事件自2002年以来的年发生频次则呈快速增长态势,说明中国在强调突发性水环境和大气环境事件监管的同时,还需加强固废污染事件及其它类型突发环境事件的监控与管理。     

Intake fraction of nonreactive motor vehicle exhaust in Hong Kong

The intake fraction (iF) of nonreactive constituents of exhaust from mobile vehicles in the urban area of Hong Kong is investigated using available monitoring data for carbon monoxide (CO) as a tracer of opportunity. Correcting for regional transport of carbon monoxide into Hong Kong, the annual-average iF for nonreactive motor vehicle emissions within the city is estimated to be around 270 per million. This estimated iF is much higher than values previously reported for vehicle emissions in US urban areas, Helsinki and Beijing, and somewhat lower than those reported for a densely populated street canyon in downtown Manhattan, New York City, or for emissions into indoor environments. The reported differences in intake fractions in various cities mainly result from the differences in local population densities. Our analysis highlights the importance of accounting for the influence of upwind transport of pollutants when using ambient data to estimate iF for an urban area. For vehicle exhaust in Hong Kong, it is found that the in/near vehicle microenvironment contributes similarly to the indoor home environment when accounting for the overall iF for children and adults.     

活性炭对含铅废水吸附特性研究

采用静态法用活性炭吸附处理含铅废水,考察了活性炭对含铅废水的吸附特性。结果表明:活性炭对铅离子吸附平衡时间为100 m in;吸附等温方程为:Ce/qe=0.4298+0.0594Ce(25℃),该方程符合Langmu ir型吸附模式,不同温度下吸附平衡参数0RL1,表示该吸附为有利吸附。实验数据应用数学模型拟合,二级相关系数R2=0.9998,显示吸附过程动力学与二级动力学模型相关性较好;计算不同温度下各热力学参数:△Hθ大于零、△Gθ小于零,证实该吸附过程是一个自发吸热过程。△Sθ大于零,表明铅离子在固液界面有序性减小、混乱度增大。△Hθ值很小,说明该过程为物理吸附。     

AFB-SBR工艺处理蓝皮制革工业废水

采用厌氧流化床(AFB)-序批式反应器(SBR)工艺处理蓝皮制革工业废水。分别考察了水力停留时间(HRT)、容积负荷对厌氧流化床以及曝气时间、污泥浓度、溶解氧浓度对SBR反应器处理效果的影响。试验结果表明,AFB将实验废水的BOD_5/COD(B/C)值由0.19～0.26提高至0.35～0.42,有效提高了其可生化性;在进水COD浓度为1 700～1 890 mg/L、HRT为1 d、容积负荷为1.792 kg COD/(m~3·d)时,COD去除率达65.2%～68.5%,且具有良好的抗冲击负荷能力。SBR在进水COD浓度为628～712 mg/L、污泥浓度为2.9 g/L、曝气时间为10 h、溶解氧浓度为2 mg/L工况下,COD去除率达87.6%,NH_3-N去除率达93.6%,处理后出水水质符合污水综合排放标准(GB 8978-1996)中的一级标准要求。     

胞外聚合物对水中Cd(Ⅱ)的吸附性能研究

以Pseudomonas fluorescens C-2产生的胞外聚合物PF-2作为新型生物吸附剂,以傅里叶变换红外光谱(FTIR)对其进行表征。系统地研究了胞外聚合物PF-2对水中Cd(II)的吸附行为。结果表明,在pH值为6.0,该吸附剂对水中的Cd(II)具有很强的吸附能力。聚合物PF-2对Cd(Ⅱ)的吸附较易进行,吸附等温线能较好地用Langmuir模型来描述,最大单分子层吸附量为33.50 mg/g,吸附动力学很好地符合准二级动力学模型。胞外聚合物PF-2含有的主要官能团为羧基、羟基和氨基等,其中羧基、羟基参与了Cd(Ⅱ)的吸附。结果表明利用胞外聚合物PF-2去除环境水样中的Cd(Ⅱ)是可行的。     

脱硫石膏改良碱化土壤种植枸杞的效果研究

利用燃煤电厂脱硫石膏改良盐碱地对于废弃物资源化利用和发展循环经济具有重要意义。选择具有典型代表性的宁夏西大滩碱化土壤,采用两因素随机区组田间实验设计,进行脱硫石膏改良碱化土壤种植枸杞的效果实验研究。研究表明脱硫石膏施用量和施用深度不同,对于降低土壤碱化度、总碱度和pH值,改良土壤碱性的效果不同;脱硫石膏施用量不同,对于促进枸杞枝条和径杆的生长不同。施用量24 000 kg/hm2较48 000 kg/hm2提高枸杞枝条生长量10.5%～18.7%、径杆生长量10.5%～18.7%;脱硫石膏施用量24 000 kg/hm2,施用深度60 cm更有利于提高枸杞红果体积、红果鲜重和产量。脱硫石膏施用量24 000 kg/hm2,施用深度60 cm较未施脱硫石膏提高枸杞红果体积、红果鲜重和产量分别为28.3%、15.0%和37.9%。     

分光光度法与离子色谱法测定空气中氯化氢的对比研究

通过对硫氰酸汞分光光度法和离子色谱法测定空气中氯化氢含量的对比发现,两种方法对实验室质控样和实际样品的分析测定均能达到要求,且F检验法分析表明实测结果没有显著性差异。然而,硫氰酸汞分光光度法的测试过程操作繁琐,误差较大,稳定时间较长,且硫氰酸汞具有剧毒,危害操作人员的健康,残液也难以处理。离子色谱法分析操作简单,过程安全可靠,能够有效降低样品受污染的可能性并保证分析质量。     

转鼓铁碳微电解法预处理液晶废水

采用转鼓铁碳微电解法预处理液晶生产废水,优化了工艺参数,并进行了装置连续运行试验。结果表明：保持转鼓转速2 r/min,在废水pH=2.0、铁碳比（m（铸铁屑）∶m（活性炭））1∶1.5、填料装填率（填料体积与反应器有效容积之比）1∶10、HRT=3 h的优化工艺条件下,废水BOD₅/COD由处理前的0.181提高到0.265;电解装置连续运行30 d,COD去除率稳定在40.1%~43.2%之间,且填料未出现板结现象。