Key Cr species controlling Cr stability in contaminated soils before and chemical stabilization at a remediation engineering site

This paper review the chemical stabilization in arsenic contaminated soil use the in situ chemical stabilization technology. Application of iron oxide, alkaline material and phosphorus are very effective agents to fix the arsenic-contaminated soil. In addition, the future study on remediation technology for arsenic-contaminated soils was prospected.

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Use of Soluble Phosphates to Stabilize Lead Contaminated Soils

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.692.161 ◽

2014 ◽

Vol 692 ◽

pp. 161-166

Author(s):

Zhong Zhong ◽

Ying Jun Sun ◽

Hui Min Lao ◽

Chi Zhang

Keyword(s):

Contaminated Soils ◽

Heavy Metal Contamination ◽

Day Treatment ◽

Ph Control ◽

Pilot Scale ◽

Soil Samples ◽

Contaminated Site ◽

Chemical Stabilization ◽

Lead Pollution ◽

Lime Treatment

Lead pollution, commonly found in lead-acid battery plants or electroplating manufactures, has drawn more and more attention due to its intrinsic toxicity to human health and potential disturbances to local ecological system. Soluble phosphates showed great advantages over other inorganic stabilizers and could provide a rapid, cost-effective approach for lead contaminated sites, despite of complex contaminants presence and heterogeneity distribution of contamination. Chemical stabilization using soluble phosphates was demonstrated by immobilize both lab samples and on-site samples from a local lead contaminated site in this study. The soil samples were mixed with soluble phosphates and stabilized for selected intervals, while adding supplements for the purpose of pH control and solidification. Experiments for treatment duration and immobilization rate in comparison with other stabilizers were also investigated to provide guidance for following demonstration project. Soil samples were analyzed before and after the treatments to compare lead immobilization rates under different circumstances. The results suggested that 90% of lead in lab soil samples was stabilized after one day treatment with phosphates, while on-site soil samples took another 30 to 50 days due to their complexity. Phosphates treatment showed great consistence over all the soil samples after 50 days in contrast with the performance of lime treatment and ferrous sulfate stabilization. It is recommended that the stabilization duration for the specific site should be longer than 30 days, at an average cost of stabilization per ton of soil around 300 RMB. This study demonstrated the use of soluble phosphates in pilot-scale lead pollution remediation, as well as the possibility of extending the remediation concept for other heavy metal contamination scenarios. In addition, chemical stabilization could also be combined with other remediation technology in future due to its simplicity and convenience.

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The key forms of Chromium influencing the long-term stability of Cr in Cr-contaminated soils and chemical stabilized soils

10.5194/egusphere-egu2020-4007 ◽

2020 ◽

Author(s):

Danni Li ◽

Guanghe Li ◽

Dayi Zhang

Keyword(s):

Contaminated Soils ◽

Southern China ◽

Chemical Properties ◽

Acid Leaching ◽

Northern China ◽

Chemical Stabilization ◽

Term Stability ◽

Long Term Stability ◽

Remediation Strategies

The toxicity and persistence of chromium in soils challenge the ecosystem and human health. Various remediation strategies have been developed to eliminate soil Cr contamination, and the most popular one is chemical stabilization. However, chemical stabilization only changes the form of Cr and does not change the concentration of Cr, so the long-term stability of Cr has been controversial. On the other hand, some researches found that the concentration of Cr(VI) in the stabilized soil after remediation has increased. We collected Cr-contaminated soils and one-year-stabilized soils from four research sites in northern, central, and southwestern China, trying to understand the difference of Cr species and structure in soils with various soil properties. Results showed despite the different clay content and mineral composition, all contaminated and stabilized soils are alkaline (pH 7.36 ~ 10.5). In addition, there are differences in the pollution levels of Cr and Cr (VI) in soils. In northern China, Cr(VI) was the main state of Cr-contaminated soils; however, Cr is mainly present in Cr-contaminated soil in the form of Cr(III) in southern China. For chemical stabilized soils, Cr concentrations remained similar to Cr-contaminated soils (1500~9000 mg/kg), but the concentration of Cr(VI) (5~55 mg/kg) was reduced through commercial remediation materials. The speciation of Cr in Cr-contaminated soils transformed from exchangeable Cr and Cr bound to carbonates into Cr bound to Fe-oxides and residuals in stabilized soils. SEM-EDS, XAFS and &#956;-XRF results revealed the main forms and structure of Cr, and showed Cr unevenly distributed on the surface or edge of the mineral. The acid leaching test revealed that Cr(VI) could be released from Cr-contaminated soils by acid, and soils can release Cr(VI) under different acidity conditions. Cr(VI) from soils collected from northern and southern China was released from acidity of [H+]=0.1M and [H+]=0.5M, respectively. This was due to erosion of coating minerals or Cr(VI)-bearing minerals. Our study suggested that stabilization technology not only reduces the toxicity of chromium, improves the stability of chromium, but also partially recovers the physical and chemical properties of soil. Meanwhile, in future remediation projects, it is necessary to consider the existing forms of chromium in different soils to develop remediation strategies.

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The Current Situation in Chemical Stabilization of Biological Materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100093912 ◽

1972 ◽

Vol 30 ◽

pp. 132-133

Author(s):

John H. Luft

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Osmium Tetroxide ◽

Molecular Level ◽

Cross Linking ◽

Chemical Stabilization ◽

Specimen Preparation ◽

Sufficient Condition ◽

Radio Telescopes

With information processing devices such as radio telescopes, microscopes or hi-fi systems, the quality of the output often is limited by distortion or noise introduced at the input stage of the device. This analogy can be extended usefully to specimen preparation for the electron microscope; fixation, which initiates the processing sequence, is the single most important step and, unfortunately, is the least well understood. Although there is an abundance of fixation mixtures recommended in the light microscopy literature, osmium tetroxide and glutaraldehyde are favored for electron microscopy. These fixatives react vigorously with proteins at the molecular level. There is clear evidence for the cross-linking of proteins both by osmium tetroxide and glutaraldehyde and cross-linking may be a necessary if not sufficient condition to define fixatives as a class.

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