铜污染土壤电动修复研究

应用实验方法研究了土壤重金属污染的电动力学修复方法，分析了土壤重金属污染物的迁移和变化特征。实验结果表明，在电场作用下土壤中重金属的浓度分布发生明显变化，使得大部分重金属能在电极附近富集而被去除。当实验的电场强度为0.5 V/cm时，在阳极附近土壤中铜的去除效率达到71.1%。阳极附近的pH值由开始时的6.8逐渐变小到4.4，而阴极附近则相反，由开始时的6.6逐渐增大到9.1，此外电动修复过程中电极附近的温度会发生相应的变化。     

电动与渗透反应格栅联合修复镉污染地下水实验

通过实验方法研究了地下水中镉污染的电动力学修复效果，并分析其迁移变化特征。实验结果表明，电动修复中由于阴阳两极的氧化还原反应造成电极附近pH值产生明显变化，其中阳极附近的pH值由开始时的7.0逐渐变小到6.8，而阴极附近则相反，由开始时6.9逐渐增大到9.1，表明土壤的酸碱条件变化明显。Cd浓度变化反映在自然渗透条件下含水层中重金属污染物的迁移能力较弱，阳极附近地下水中Cd的去除率仅8.4%，而在电场作用下地下水中重金属的浓度发生明显变化，使得重金属污染物能在电极附近富集而被去除，当实验电场强度为0.5 V/cm时，Cd在阴极的累积使得阳极附近地下水中去除率为72.9%，说明电动修复重金属Cd污染地下水的效果明显好于自然渗透状态。     

重金属污染土壤电动力学修复技术

电动力学修复技术是把电极插入受污染的土壤并通入直流电 ,发生土壤孔隙水和带电离子的迁移。土壤中的污染物质在外加电扬作用下发生定向移动并在电极附近累积 ,抽出处理从而被除去。新兴的电动力学原位修复技术去除土壤重金属污染正越来越多地被各国研究人员接受。一系列实验规模的研究和技术已日渐成熟 ,其中Lasagna技术和Electro klean技术已在美国肯塔基州和路易斯安那州等地进行了原位修复     

重金属污染土壤电动力学修复技术

电动力学修复技术是把电极插入受污染的土壤并通人直流电，发生土壤孔隙水和带电离子的迁移。土壤中的污染物质在外加电扬作用下发生定向移动并在电极附近累积，抽出处理从而被除去。新兴的电动力学原位修复技术去除土壤重金属污染正越来越多地被各国研究人员接受。一系列实验规模的研究和技术已日渐成熟，其中Lasagna技术和E-lectro-klean技术已在美国肯塔基州和路易斯安那州等地进行了原位修复。     

电极材料对电解法处理循环式准好氧垃圾填埋场渗滤液效果的影响研究

分别用3种不同材料电极(不锈钢、Ti/Pt和Ti/RuO2-IrO2)作阳极、石墨电极作阴极在同一条件下分别对循环式准好氧填埋垃圾场渗滤液进行电解处理对比研究.研究结果表明,随着电解时间的变化,渗滤液中的COD、BOD5、BOD5/COD、重金属离子浓度、色度和pH值均会发生改变.当电解时间为10～20 min时,用上述3种电极作阳极电解均会出现渗滤液COD、BOD5、BOD5/COD增大的现象;当电解时间为30～40 min时,用Ti/RuO2-IrO2或Ti/Pt电极作阳极电解均可使渗滤液的色度降为0;当电解时间为120 min时,分别用3种电极作阳极电解都可使渗滤液中的COD、BOD5和重金属得到有效的去除,其中用Ti/RuO2-IrO2电极作阳极电解对COD、BOD5的去除效果最好:用Ti/Pt电极作阳极电解对Pb2 的去除效果最好.     

电絮凝法处理重金属底泥清淤尾水

采用电絮凝法处理湘江霞湾港重金属底泥清淤尾水,研究了电极转换方式、起始p H值和电流密度对尾水中各污染物去除效果的影响。实验结果表明,采用先由铁作为阳极反应20 min,然后转换铝作为阳极反应10 min的组合方式,当起始p H值为6,电流密度为100 A·m-2时,Cd、Zn、Cu、Pb、Hg、As、NH+4-N和TP的去除效率分别可以达到99.2%、98.6%、99.3%、98.4%、99.5%、99.7%、84.8%和95.9%。电絮凝法去除尾水中重金属的主要机制是分布于悬浮物中的重金属主要通过疏松态铝的絮凝以及氢气的气浮作用去除,而分布于过滤液中的重金属主要以其氢氧化物沉淀去除。     

电极材料对电解法处理循环式准好氧垃圾填埋场渗滤液效果的影响研究

分别用3种不同材料电极（不锈钢、Ti／Pt和Ti／RuO2-IrO2）作阳极、石墨电极作阴极在同一条件下分别对循环式准好氧填埋垃圾场渗滤液进行电解处理对比研究。研究结果表明，随着电解时间的变化，渗滤液中的COD、BOD5、BOD5／COD、重金属离子浓度、色度和pH值均会发生改变。当电解时间为10—20min时，用上述3种电极作阳极电解均会出现渗滤液COD、BOD5、BOD5／COD增大的现象；当电解时间为30—40min时，用Ti／RuO2-IrO2或Ti／Pt电极作阳极电解均可使渗滤液的色度降为0；当电解时间为120min时，分别用3种电极作阳极电解都可使渗滤液中的COD、BOD5和重金属得到有效的去除，其中用Ti／RuO2-IrO2电极作阳极电解对COD、BOD5的去除效果最好：用Ti／Pt电极作阳极电解对Pb^2＋的去除效果最好。     

土壤中铬电动修复过程及影响因素

实验筛选出阳极pH、阴极pH、电压梯度、电极形状4种影响因素,以黏土为研究对象,设计正交实验和对比实验研究铬的电动修复过程。结果表明,最重要的影响因素为电压梯度,其他影响因素重要性排序为阳极pH、阴极pH、电极形状;在电压梯度为1.5 V·cm~(-1)下,以去离子水作为电解质,分别控制阴极和阳极pH在11和3,取得很好的去除效果,144 h后铬迁移率达到80.9%。总铬和六价铬分布规律类似,从阳极到阴极呈现逐渐下降的趋势。经过电动修复后土壤中水溶态铬比例减少,可氧化态和残渣态比例增大。铬电动修复控制系统在微电流范围内可取得很好的去除效果。     

可渗透反应复合电极法对土壤重金属的电动去除

将零价铁(Fe0)、沸石等活性材料附着在电极上形成可渗透反应层并构成可渗透反应复合电极,采用不同的复合电极对Cd2+、Ni 2+、Pb2+和Cu2+等4种阳离子型重金属污染土壤进行了电动力学修复。研究了不同可渗透反应复合电极对土壤pH的控制效果以及对重金属的去除作用,分析了迁移到复合电极中的重金属形态变化。结果表明,复合电极中添加酸、碱性沸石并适时更换,可有效中和、截留阴阳极电解产生的OH-和H+,避免或减缓土壤酸碱迁移带的形成,防止重金属离子的过早沉淀及土壤过度酸化,极大提高了重金属的去除率。复合电极中Fe0可将迁移进来的重金属离子进行还原稳定,实现重金属污染物的捕获与固定,与迁移到沸石复合电极中的4种重金属不稳定态相比,"Fe0+沸石"复合电极中重金属不稳定态分别下降了61.4、60.5、61.4、57.1百分点。结果还显示,阴极采用"Fe0+沸石"复合电极并适时进行更换,施加1.5V/cm的直流电压修复10d后,土壤中Cd、Ni、Pb、Cu的总去除率分别为44.5%、41.5%、33.5%和36.7%,且进一步延长修复时间和持续更换电极可获得更为理想的修复效果。     

有机酸对成都平原镉污染土壤的淋洗效果

以成都平原某化工厂附近受Cd污染的2种土壤为对象,采用振荡淋洗技术,研究了有机酸在不同浓度、固液比、振荡时间和复合淋洗条件下对重金属Cd的去除效果。实验结果表明:柠檬酸和酒石酸对Cd含量为22.78 mg·kg~(-1)的SLT-01土壤具有更好的去除效果,分别达到73%和62%,而乙酸和草酸的去除能力较低;随着固液比的降低,有机酸对Cd的去除率逐步提高;随着时间的增加,Cd的去除率波动增加;柠檬酸和酒石酸复合淋洗并没有提高Cd的去除率;振荡淋洗前后土壤结构未发生明显变化。综合考虑土壤中Cd的去除效果和成本,选择柠檬酸作为最佳淋洗剂;最佳实验条件:溶液浓度为0.10 mol·L~(-1),固液比为1∶20,淋洗时间为8 h。     

Implications of rhizospheric heavy metals and nutrients for the growth of alfalfa in sludge amended soil

Rhizospheric distribution of nutrients and heavy metals in sludge amended soil was investigated using the rhizobag technique to give an indication of the release of metals from wastewater sludge. DTPA-extractable Zn, Cd, Ni and Mn, and available P, K and NH4+-N in the rhizosphere were markedly depleted when soil was amended with sludge. There was no conspicuous depletion or accumulation of DTPA-extractable Cu in the rhizosphere when the soil was amended with sewage sludge but DTPA-extractable Fe accumulated in the rhizosphere when the soil was amended with increasing amounts of sludge. The pH value in the rhizosphere increased with distance from the roots when soil was amended with larger amounts of sludge. The exchangeable fraction of Cu in the rhizosphere was depleted whether or not the soil was treated with sludge. Carbonate, oxide, organic and residual fractions of Cu and Zn were depleted in the rhizosphere at a distance of 0-2 mm from the roots when soil was amended with 50% sludge. Application of sewage sludge had a positive effect on alfalfa growth. With an increase in sludge amounts, the concentrations of Fe, Cu and Zn in alfalfa shoots did not change. Soil amendments with less than 25% sludge did not increase the availability or mobility of heavy metals. The depletion in rhizospheric DTPA-extractable Zn, Cd and Ni indicates that with the sole exception of Cu, release of metals from sludge amended soil was very limited.     

石灰干化污泥对土壤重金属稳定化处理的效果

以采自湖南省嘉禾县重金属复合污染土壤为研究对象,采用城市污水处理石灰干化污泥作为稳定剂,对污染土壤进行稳定化处理,并采用TCLP和BCR连续提取法对稳定化效果进行分析和评价。研究结果表明,单独使用石灰干化污泥,TCLP浸出浓度随着干化污泥质量分数的增加而显著减少,干化污泥的质量分数为40%时,稳定化率最大为Zn-98.92%、Cd-99.06%、Pb-96.84%;但是干化污泥的高pH值导致稳定后土壤中As的浸出增加。为了恢复植物生长功能,经过亚铁盐和磷酸调节pH后,石灰干化污泥稳定过的土壤pH有效降低,同时亚铁盐和磷酸有利于促进Pb和Zn的稳定效果;但是对Cd的稳定有负面影响;另外,亚铁盐的加入同时可以减少As的浸出浓度。经处理后土壤中重金属形态由不稳定态转为稳定态,使重金属的浸出浓度明显降低,减少了土壤重金属的浸出毒性。该研究结果表明,石灰干化污泥可以作为资源回收利用,应用于重金属污染土壤的修复中,并能改善稳定后土壤适宜植物生长的理化性质。     

Response of microbial activities to heavy metals in a neutral loamy soil treated with biosolid

Application of biosolid on land has been widespread in numerous countries for last several decades. This study performed incubation experiments by mixing a neutral loamy soil and biosolid enriched in Cu, Pb and Zn to explore how heavy metal affects soil mineralization and microbial biomass. The experimental results indicated that large nutrient, microorganism and C sources from biosolid were beneficial to microbial respiration. However, compared to the biosolid alone treatment, the supplemented Cu, Pb and Zn in biosolid reduced the mineralized C by roughly 36%. This phenomenon was probably caused by a portion of the Cu, Pb and Zn being complexed with organic matter to prevent decomposition of organic carbon by microorganisms. Equally, soil treated with biosolid increased the quantity of mineralized N by approximately five-fold and accelerated the rate of N mineralization by about one-fold compared to untreated soil. Notably, addition of heavy metals impaired the mineralization process, particularly when Pb reached about 64%. The reduced N mineralization occurred for similar reasons to the microbial respiration. The addition of biosolid in soil considerably increased the amount of mineralizable N; however, the increase was lower in biosolid-treated soil spiked by heavy metals. The addition of heavy metals in the soil-biosolid mixture clearly reduced the microbial biomasses C (MBC) and N (MBN), indicating that the microbial activities had been disrupted by the heavy metals. The microbial biomass C/N ratio had changed initially from 8 to 13 at the end of incubation period, owing to various groups of microbes expressing different mechanisms of metabolism, indicating that the microbial population had changed from bacteria to fungi, which had higher metal tolerance.     

模拟酸雨对大宝山尾矿淋滤实验研究

在模拟酸雨作用下,研究了大宝山尾矿中重金属Cd、Pb及Mn的释放规律及动力学。结果表明,在淋滤液不同酸度(pH为5.6、4.8、3.0)条件下,不同重金属呈现出不同的释放规律。随着淋滤量的增加,淋出液pH逐渐上升;Cd和Mn的释放可分为快速释放和慢速释放2个阶段,Pb的释放速度一直相对稳定。随着淋滤液pH的降低,淋出液pH降低,重金属的释放量及释放速度增加;淋滤液pH对3种重金属释放的影响程度为Pb>Mn>Cd。Cd和Mn的释放可用准二级动力学方程及Elovich方程很好拟合,准二级动力学方程更优;Pb的释放可用双常数方程和零级动力学方程很好拟合。     

Bioleaching of heavy metals from sediment: significance of pH

Bioleaching process, which causes acidification and solubilization of heavy metals, is one of the promising methods for removing heavy metals from contaminated sediments. The solubilization of heavy metals from contaminated sediments is governed by the sediment pH. In the present study, the significance of pH in bioleaching of heavy metals from contaminated sediment was evaluated at different solid contents of sediments in a bench-scale reactor. Results showed that a temporal change of pH in the bioleaching process was effected by the buffering capacity of the sediment particulates. The variations of pH in this bioleaching process were calculated by a modified logistic model. It was observed that solubilization of heavy metals from sediments is highly pH-dependent. In addition, a non-linear equation for metal solubilization relating pH value in the bioleaching process was established. This allows an easier and faster estimate of metal solubilization by measuring pH in the bioleaching process.     

The use of a sequential leaching procedure for assessing the heavy metal leachability in lime waste from the lime kiln at a caustizicing process of a pulp mill

A five-stage sequential leaching procedure was used to fractionate 13 heavy metals (Cd, Cu, Pb, Cr, Zn, Fe, Mn, Al, Ni, Co, As, V, Ba) and sulphur (S) in lime waste from the lime kiln at the causticizing plant of Stora Enso Oyj Veitsiluoto Pulp Mills at Kemi, Northern Finland, into the following fractions: (1) water-soluble fraction (H₂O), (2) exchangeable fraction (CH₃COOH), (3) easily reduced fraction (HONH₃Cl), (4) oxidizable fraction (H₂O₂ + CH₃COONH₄), and (5) residual fraction (HF + HNO₃ + HCl). Although metals were leachable in all fractions, the highest concentrations for most of the metals were observed in the residual fraction (stage 5). It was also notable that the total heavy metal concentrations in lime waste did not exceed the maximal allowable heavy metal concentrations for soil conditioner agents set by the ministry of the Agricultural and Forestry in Finland. The heavy metals concentrations in lime waste were also lower than the maximal allowable heavy metals concentrations of the European Union Directive 86/278/EEC on the protection of environment, and in particular of the soil, when sewage sludge is used in agriculture. The Ca concentration (420 g kg⁻¹; d.w.) was about 262 times higher than the typical value of 1.6 g kg⁻¹ (d.w.) in arable land in Central Finland. However, the concentration Mg (0.2 g kg⁻¹; d.w.) in lime waste was equal to the Mg concentration in arable land in the Central Finland. The lime waste has strongly alkaline pH (12.8) and a neutralizing value (i.e. liming effect) of 47.9% expressed as Ca equivalents (d.w.). This indicates lime waste to be a potential soil conditioner and improvement as well as a pH buffer.     

Evaluation of remediation process with plant-derived biosurfactant for recovery of heavy metals from contaminated soils

A washing process was studied to evaluate the efficiency of saponin on remediating heavy metal contaminated soils. Three different types of soils (Andosol: soil A, Cambisol: soil B, Regosol: soil C) were washed with saponin in batch experiments. Utilization of saponin was effective for removal of heavy metals from soils, attaining 90-100% of Cd and 85-98% of Zn extractions. The fractionations of heavy metals removed by saponin were identified using the sequential extraction. Saponin was effective in removing the exchangeable and carbonated fractions of heavy metals from soils. In recovery procedures, the pH of soil leachates was increased to about 10.7, leading to separate heavy metals as hydroxide precipitates and saponin solute. In addition recycle of used saponin is considered to be effective for the subsequent utilization. The limits of Japanese leaching test were met for all of the soil residues after saponin treatment. As a whole, this study shows that saponin can be used as a cleaning agent for remediation of heavy metal contaminated soils.