Soil Washing is a technique for the remediation of contaminated soil, through a process of physical separation of the pollutant and the recovery of the valuable part of the treated material. The technique consists in washing the contaminated soil with water, aqueous solutions of surfactants, biosurfactants or organic solvents.
Soil washing is used in case of soil contamination by heavy metals, hydrocarbons and pesticides.
Removal of contaminants occurs by two mechanisms:
- MECHANICAL: Disintegration of agglomerates that may be present in the soil and the release in suspension in the extracting liquid of the contaminant particles;
- PHYSICAL-CHIMICAL: Concentration and eventual dispersion of the contaminants in the extraction liquid in the form of suspended particles
EXTRACTIVE FLUIDS USED IN THE WASHING
Depending on the type of pollutant, Washing is done by choosing from the following possible extractive fluids, such as:
- Water, hot or cold;
- Water with surfactants;
- Acid solutions (usually with HCl, H2SO4 and NHO3);
- Alkaline solutions (typically with NaOH, Na2CO3);
- Complexing agents (citric acid, ammonium acetate, NTA and EDTA-ethylenediaminetetraacetic acid);
- Organic solvents.
THE MAIN PHASES OF SOIL WASHING
In Soil Washing we exploit the fact that pollutants tend to adhere more to fine particles. Due to their high specific surface area they tend to absorb a greater quantity of pollutants. Through the washing process with the different extracting fluids, we separate the fine particles impregnated with pollutants from the other particles, we select the different granulometries of the washed materials and finally, through the filtration and water treatment plant, we filter and treat the washing liquid used.
The main phases of the Soil Washing process are:
- Pretreatment of the contaminated soil,
- Washing and extraction of the contaminants,
- Phase separation (extracting liquid/soil),
- Soil Post-treatment,
- Purification of the extracting agent, and its subsequent re-entry into the extraction cycle.
MATEC SOIL WASHING
Matec Soil Washing plants, realized with advanced technology, wash, select and recycle all materials from quarries, mines and C&D plants.
MATEC has designed a line dedicated to WASHING, which includes various technological solutions to meet the customer’s needs, guaranteeing low management costs, high productivity, customization and modularity of the plant. All this while maintaining full respect for the environment.
“What was once waste, today, can become a resource. – Matteo Goich”
The line of machinery dedicated to Washing and Classification are: