『Abstract
Stabilisation/solidification (S/S) of heavy metals and a parallel
biodegradation of an organic contaminant using magnesium phosphate
cements (MPC) was investigated under laboratory conditions. The
study was aimed at improving the robustness of S/S technology
by encouraging biodegradation in order to bring about some form
of contaminant attenuation over time. A silty sand soil, amended
with compost was spiked with an organic contaminant, 2-chlorobenzoic
acid (2CBA), and two heavy metal compounds, lead nitrate and zinc
chloride. Two formulations of the MPC grouts based on different
proportions of the cement constituents, with paste pH of approximately
6.5 and 10, were utilised for S/S treatment. The study involved
treating the organic contaminant present in the soil with and
without the heavy metals by employing the low and high pH MPC
grout mixes, and using 10％ and 25％ compost content. Microbial
activity was monitored using dehydrogenase assay, whilst the tests
pertaining to the performance criteria such as contaminant concentration,
unconfined compressive strength, elastic stiffness, permeability
and batch leaching tests were evaluated at set periods. Contaminant
recovery analysis after 140 days indicated a similar reduction
in 2CBA concentration to approximately 56％ in the different grout
mixes. The cement constituents exhibited stimulatory and inhibitory
effects on soil dehydrogenase activity. heavy metal leachability
as well as the engineering behaviour of the treated soils conformed
to acceptable standards. The results of the investigations show
considerable promise for the application of MPC in contaminated
land remediation.
Keywords: Stabilisation/solidification: Biodegradation; Soil contamination;
magnesium phosphate cement; Land reclamation』
1. Introduction
2. materials and methods
2.1. Model-contaminated soil
2.2. Binder materials
2.3. Preparation of stabilised/solidified soil systems
2.4. Experimental design
2.5. Sampling
2.6. Testing and analytical methods
2.7. Statistical analysis
3. Results and discussion
3.1. pH of soil-CEMENT grout
3.2. Moisture content
3.3. Organic contaminant analysis
3.4. Microbial enzyme activity
3.5. Batch leaching
3.6. Linkage between dehydrogenase activity and concentration
of contaminants
3.7. Engineering properties
4. Conclusions
Acknowledgements
References