不同磷酸盐复合黑曲霉对水体铅污染修复的研究

本实验探究了难溶性磷酸铁和磷酸钙分别复合黑曲霉对水体铅污染修复的影响。结果表明,添加磷酸铁、磷酸钙和黑曲霉均能降低溶液中铅离子的含量,培养6天后,铅离子的去除率分别为97.20%,98.37%和97.45%。磷酸钙去除的铅离子中可被提取的TCLP-Pb含量最低,为0.06 mg/g,且不受黑曲霉的影响。通过XRD的测定结果表明,在添加磷酸钙与磷酸钙+黑曲霉的处理中均发现了磷氯铅矿的形成。与磷酸钙相比,经磷酸铁处理的TCLP-Pb的含量显著低于经磷酸铁+黑曲霉处理的含量(0.23 mg/g比7.38 mg/g)。与单独添加磷酸铁相比,黑曲霉能够分泌出草酸与铅反应形成的草酸铅矿物,从而降低了铅的有效性。

风化煤固定化微生物材料对铅的吸附特性及机理

风化煤固定化微生物材料较游离微生物能更好地钝化重金属。研究旨在探究风化煤固定化微生物材料的铅吸附性能及机理,为其污染场地应用提供理论指导和依据。以风化煤固定化微生物材料为对象,通过批量吸附试验系统研究材料的用量、pH、吸附时间和铅溶液质量浓度对其吸附性能的影响,并采用动力学、热力学模型拟合的方式描述铅吸附过程,结合扫描电镜和红外光谱技术对吸附机理进行探究。结果表明,风化煤固定化微生物材料用量为0.4 g/L、pH值为4、吸附时间大于12 h时,在200 mg/L铅溶液中吸附性能最优,最大吸附量达到338 mg/g;拟二级动力学模型和Langmuir模型显示,该吸附过程以化学吸附为主,且铅离子以单分子层的形式排列;热力学分析表明,该反应是自发的吸热反应,温度升高会促进反应的发生。材料表面钙、钠等元素的离子交换作用及羟基、羧基、羰基、酰胺基等活性基团的络合沉淀作用,促进了风化煤固定化微生物材料的铅吸附作用。在铅质量浓度为200 mg/L,材料用量为0.4 g/L、pH值为4、吸附时间大于12 h时,可实现材料吸附性能的最大化。材料表面的Ca、Na等元素与铅的离子交换作用以及羟基、羧基、羰基、酰胺基与铅的络合沉淀作用是其主要作用机制。

解磷真菌驱动磷灰石固定重金属铅的地球化学模拟研究

结合磷灰石和解磷菌进行农业土壤铅修复是环境修复领域的新兴技术。然而仅靠实验很难全面解析修复过程中的详细反应过程和铅的成矿机制,特别是难以解释目标稳定矿物氟基磷酸铅为何不是主要产物。本文主要利用GWB软件中的React和Act2两个程序模块,基于前人实验数据设置模拟参数,对这一科学问题进行探究。首先用React程序模块的滴定模式(Titration)来研究黑曲霉复合氟基磷灰石的除铅过程,即通过向反应体系中逐步滴加草酸来模拟黑曲霉分泌草酸的过程。反应体系中Pb^(2+)初始浓度为8.4 mmol·L^(-1),草酸总添加量为2.0 g·L^(-1),氟基磷灰石总添加量为8.3 g,其中草酸和氟基磷灰石分为100步添加到体系中。React模拟过程终止后,可得到体系pH值、主要离子浓度(Pb^(2+)、Ca^(2+)、H_2PO-_4^-、F^-和C_2O_4^(2-))以及生成产物随着草酸和氟基磷灰石添加的变化曲线。然后将黑曲霉与氟基磷灰石培养后的浸出液与Pb(NO-_3)_2溶液混合后,用Act2模块模拟其草酸和F^-浓度变化对铅矿物形态的影响。模拟结果表明:草酸引起的pH值变化是影响铅矿化结果的最重要参数,体系中的Pb^(2+)主要以草酸铅形式沉淀,和原实验结果吻合。此外,只有在弱酸或碱性环境下,且溶液中氟离子浓度大于27 mmol·L^(-1)时,体系中才会生成氟基磷酸铅。该结果为利用磷酸盐矿物材料进行土壤铅修复提供了理论指导。

黏土矿物对cd2+2+、Pb2+污染土壤的修复效果研究

随着我国重金属土壤污染日益严重,土壤污染修复技术也得到了高度重视,对修复技术在不同污染土壤中的应用效果的研究也更加细致和深入.本文介绍了我国土壤污染现状,从修复污染土壤的两个方向着手,重点介绍了化学修复、微生物修复以及联合修复技术,并总结探讨了黏土矿物对镉、铅污染土壤的修复效果的研究.

Improvement in electrokinetic remediation of Pb-contaminated soil near lead acid battery factory

To improve the conventional electrokinetic remediation of Pb-contaminated soil,the Pb-contaminated soil near a lead acid battery factory in the Pearl River Delta region of China was electrokinetically remedied with polarity exchange technique.The variations in Pb removal efficiency and the soil p H value with the treatment time and the exchange polarity interval were determined.It is found that the removal efficiency of Pb reaches a maximum of 87.7% when the voltage gradient is 1 V/cm and the exchange polarity interval is 48 h.This value is far higher than that obtained with conventional electrokinetic remediation（61.8%）.Additionally,the ＂focusing effect＂ which appears in the conventional electrokinetic remediation can be avoided,and thus additional chemicals are not needed for the polarity exchange technique.The mechanism of Pb electromigration behavior in soil during the treatment with the polarity exchange technique was described.

Effects of Red Mud on the Remediation of Pb, Zn and Cd in Heavy Metal Contaminated Paddy Soil

[Objective] To study the remediation efficiency of red mud on Pb, Zn and Cd in the heavy metal contaminated paddy soil of mine area, to clarify its remediation mechanism and fertilizer efficiency on heavy metal contaminated soil. [Method] The soil incubation experiment was conducted to study the effect of red mud on the pH values and electrical conductivity （EC）, and the remediation efficiency of red mud on lead （Pb）, zinc （Zn） and cadmium （Cd） in heavy metal contaminated soil. [Result] Red mud addition reduced the content of exchangeable Pb, Zn and Cd in the soil significantly. Compared with the control, when incubated for 30, 60 and 90 d with the red mud dosage of 4% （W/W）, the exchangeable Pb content was decreased by 39.25%, 41.38% and 50.19%; exchangeable Zn content was decreased by 49.26%, 57.32% and 47.16%; and exchangeable Cd content was decreased by 19.53%, 24.06% and 25.70%, respectively. The application of red mud had significant impact on the share of Pb, Zn and Cd contents in five forms, and different amounts of red mud application all reduced the proportion of exchangeable Pb, Zn and Cd to the total Pb, Zn and Cd. In addition, the proportion of exchangeable Pb, Zn and Cd to total Pb, Zn and Cd decreased with the increasing amount of red mud addition. [Conclusion] The study provided references for reasonable application of red mud and reduction of heavy metal pollution in paddy soil.

Remediation of Pb-contaminated port sediment by biosurfactant from Bacillus sp.G1

The remediation of Pb-contaminated port sediment by biosurfactant from a new isolated Bacillus sp.G1was studied.ThePb removal efficiencies were investigated under multi-levels of water-solid ratio,pH and ionic strength.Result showed thatexchangeable speciation of Pb could be removed by maximum removal capacity of76.8mg/g after leaching.The Langmuir isothermreflected the adsorption process best to fit the experimental adsorption equilibrium data.Fourier transform infrared spectra(FTIR)indicated that C=O and-CH3may be the functional groups.Scanning electron microscopy(SEM)analysis showed that thesurface of the port sediment became much smoother after adsorption interaction,which reflected that the complexation between Pbions and biosurfactant was more stable.The results indicated that the biosurfactant of Bacillus sp.G1could remove Pb effectivelyfrom the Pb-contaminated port sediment(PCPS)and suggested a novel method for PCPS remediation.

Application of polymeric aluminum salts in remediation of soil contaminated by Pb,Cd,Cu,and Zn

Soil contaminated with typical heavy metals (Pb,Cd,Cu,and Zn) was remedied by using the polymeric aluminum salt coagulants including polyaluminum chloride (PAC) and polyaluminum sulfate (PAS).The remediation efficiencies are influenced by reaction time,water amount,and dosage of remediation agent.The optimal remediation conditions are as follows:6 h of reaction time,1 kg/kg of water addition amount,and 0.25 kg/kg of remediation agent dosage.After PAC addition,the remediation efficiencies of diethylenetriamine-pentaacetic acid (DTPA)-extractable Pb,Cd,Cu,and Zn reach 88.3%,85.1%,85.4%,and 73.7%,respectively;and those for PAS are 89.7%,88.7%,83.5%,and 72.6%,respectively.The main remediation mechanism of the polymeric aluminum salt may contribute to the ionization and hydrolysis of PAC and PAS.H + released from ionization of polymeric aluminum salt can cause the leaching of heavy metals,while the multinuclear complex produced from hydrolysis may result in the immobilization of heavy metals.For PAC,the immobilization of heavy metals is the main remediation process.For PAS,both leaching and immobilization are involved in the remediation process of heavy metals.

Immobilization of Cd and Pb in soils by polymeric hydroxyl ferric phosphate

A polymeric hydroxyl ferric phosphate(PHFP)was prepared by using a byproduct of titanium dioxide containing ferrous sulfate and phosphates under alkaline condition.The PHFP was used to immobilize lead(Pb)and cadmium(Cd)in soils.Fourier transform infrared spectra,X-ray diffraction were applied to revealing the characteristics of PHFP,and the modified Tessier sequential extraction and column leaching experiment with simulated acid rain were used to assess the effectiveness of immobilization of Cd and Pb in soils by PHFP.The results showed that PHFP was indeed a polymer with complicated OH-Fe-P structure and consisted of Fe6(OH)5(H2O)4(PO4)4(H2O)2and Fe25(PO4)14(OH)24.Moreover,the removal rates of DTPA-extractable Cd and Pb in soils reached up to33%and45%,and the water-soluble Cd and Pb decreased by56%and58%,respectively,when PHFP was added in soils at4%dosage.In addition,the immobilization of Cd and Pb contributed to transforming water soluble,exchangeable and carbonate-bonded fractions to Fe and Mn oxides-bonded,organic-bonded and residual fractions.Under leaching with simulated acid rain,Cd and Pb release amount in PHFP amended soil declined by53%and52%,respectively,as compared with non-treated soil.The result implied that PHFP had a potential application for the remediation of Cd-and Pb-contaminated soils.

Isolation and Screening of Rhizobacteria from Scirpus Grossus Plant after Lead （Pb） Exposure

Phytoremediation is one of method which can be applied to remediate the contaminated environment. In most cases, microorganisms bacteria and fungi, living in the rhizosphere closely associated with plants, may contribute to mobilize metal ions by increasing the bioavailable fraction. Some studies have evidenced that heavy metal-resistant bacteria can enhance metal uptake by hyperaccumulator plants. Lead-resistant bacteria which could help to increase the lead uptake by Scirpus grossus was isolated and screened. The samples were taken from plant roots after being exposed in a range finding test by spiking analytical grade of Pb（NO3）2 solution in variation of Pb concentrations. The results of rhizobacteria isolation showed that there were several colonies having resistance to grow and survive in contaminated environment even the host plant had withered. Only a few of rhizobacteria colonies were affected by high concentrations of lead exposure during screening test. The screening test was conducted by growing the isolated colonies on plates containing tryptic soy agar （TSA） medium containing of 200, 400 and 600 mg/L Pb solution including the plate with only TSA media without any lead exposure acting as a control medium, and incubating them at 30℃ for 72 hours. Isolation of bacteria from rhizosphere had found 47 colonies including several colonies from the withered plants. These all 47 colonies then become 28 after characterization by using color and colony morphology, followed by Gram stain, catalase, oxidase and motility test. The screening test of lead resistant bacteria colonies resulted 3 groups which is scored high, medium and low. The screened colonies will then be used for further study.

Lead accumulation and tolerance of Moso bamboo(Phyllostachys pubescens) seedlings: applications of phytoremediation

A hydroponics experiment was aimed at identifying the lead（Pb） tolerance and phytoremediation potential of Moso bamboo（Phyllostachys pubescens） seedlings grown under different Pb treatments. Experimental results indicated that at the highest Pb concentration（400 μmol/L）, the growth of bamboo seedlings was inhibited and Pb concentrations in leaves, stems, and roots reached the maximum of 148.8, 482.2, and 4282.8 mg/kg, respectively. Scanning electron microscopy revealed that the excessive Pb caused decreased stomatal opening, formation of abundant inclusions in roots, and just a few inclusions in stems. The ultrastructural analysis using transmission electron microscopy revealed that the addition of excessive Pb caused abnormally shaped chloroplasts, disappearance of endoplasmic reticulum, shrinkage of nucleus and nucleolus, and loss of thylakoid membranes. Although ultrastructural analysis revealed some internal damage, even the plants exposed to 400 μmol/L Pb survived and no visual Pb toxicity symptoms such as necrosis and chlorosis were observed in these plants. Even at the highest Pb treatment, no significant difference was observed for the dry weight of stem compared with controls. It is suggested that use of Moso bamboo as an experimental material provides a new perspective for remediation of heavy metal contaminated soil owing to its high metal tolerance and greater biomass.

Biochar and alternate partial root-zone irrigation greatly enhance the effectiveness of mulberry in remediating lead-contaminated soils

Aims Soil lead contamination has become increasingly serious and phytoremediation can provide an effective way to reclaim the contaminated soils.This study aims to examine the growth,lead resistance and lead accumulation of mulberry(Morus alba L.)seedlings at four levels of soil lead contamination with or without biochar addition under normal or alternative partial root-zone irrigation(APRI).Methods We conducted a three-factor greenhouse experiment with biochar(with vs.without biochar addition),irrigation method(APRI vs.normal irrigation)and four levels of soil lead(0,50,200 and 800 mg·kg^(-1)).The performance of the seedlings under different treatments was evaluated by measuring growth traits,osmotic substances,antioxidant enzymes and lead accumulation and translocation.Important Findings The results reveal that mulberry had a strong ability to acclimate to soil lead contamination,and that biochar and APRI synergistically increased the biomass and surface area of absorption root across all levels of soil lead.The seedlings were able to resist the severe soil lead contamination(800 mg·kg^(-1) Pb)by adjusting glutathione metabolism,and enhancing the osmotic and oxidative regulating capacity via increasing proline content and the peroxidase activity.Lead ions in the seedlings were primarily concentrated in roots and exhibited a dose–effect associated with the lead concentration in the soil.Pb,biochar and ARPI interactively affected Pb concentrations in leaves and roots,translocation factor and bioconcentration.Our results suggest that planting mulberry trees in combination with biochar addition and APRI can be used to effectively remediate lead-contaminated soils.