Clay contaminant

Former Paint Factory, Groningen, The Netherlands 1987 400 yd of clay contaminated with copper, lead, and zinc 120,000... 

Galvanizing Plant, Delft, The Netherlands 1988 300 yd of clay contaminated with zinc and cadmium 160,000... 

The factors that affect the technical and economic performance of ChemTech soil treatment process technology include the following soil type (sand versus clay) contaminant (metals, petroleum compounds, particulate metals, etc.) type, form, and concentration cleanup objectives (residential, industrial, or risk-based) and the scale of the project. These factors determine optimum operating conditions, process kinetics, the quantity of residuals, and the operating costs (D177360, p. 9). 

The Therminator is an ex situ, commercially available medium-temperature portable thermal des-orption/destruction unit for soils and clays contaminated with petroleum hydrocarbons. According to the vendor, the Therminator offers an alternative to landfilling petroleum-contaminated soils. All information is from the vendor and has not been independently verified. 

Electrokinetics is an in situ remediation technology applicable to soil or soil-like material with low hydraulic conductivities (e.g., clay) contaminated with heavy metals, radionuclides, and selected organic pollutants. The technique has been used in the past in the oil recovery industry and to remove water from soils. 

SAND EQUIVALENT A measure of the amount of silt or clay contamination in fine aggregate as determined by test (ASTM D 2419). 

A chemo-elasto-plastic model for the behaviour of clays in contact with a single contaminant has been presented. The model has been implemented in the finite elements program LAGAMB JE providing an efficient tool for solving problems involving clay-contaminant interaction. Comparison of model predictions with available... 

For most limestone sands, the most significant impurity is likely to be clay and precautions may need to be taken to reduce clay contamination (e.g. by rinsing the sand, or by pre-screening stone to remove the clay-rich fine fraction before crushing). 

Yuan (2006) reported a study on the effect of Fe on EK remediation of clay contaminated with PCE. That work investigated the effect of iron wall position and Fe°quantity on the remediation efficiency and EK performance of PCE-contaminated clay under an electric potential gradient of 2V/cm for 5 days. The iron wall was composed of 2-16g of Fe° mixed with Ottawa sand at a ratio of 1 2. Its positions were located at the anode, the middle, and the cathode end of the EK cell, respectively. Test results showed that a relatively higher remediation of 66% of PCE was found as the iron wall located at the cathode side, which corresponded to a factor... 

Yuan C. (2006). The effect of Fe(0) on electrokinetic remediation of clay contaminated with perchloroethylene. Water Science and Technology 53(6) 91-98. 

An impure montmorillonite clay, contaminated and other minerals it is one of the few sources in this country. Fuller s Earth was formerly —removing fatty substances from wool, this to its large surface area, which gives it great It has a high cation-exchange capacity, the cation being Ca. The only important deposit near Nutfield, Surrey. 

A soil like clay contaminated by heavy metal pollution, can be considered as a porous medium containing water and ions adsorbed (heavy metals cations) on negatively charged sites (silicates). By applying a moderate electric field and injecting an appropriate solvent, one will obtain an electroosmotic flow of solvent containing the heavy metal ions to eliminate. 

Before this treatment, the cassiterite content of the ore is increased by removing impurities such as clay, by washing and by roasting which drives off oxides of arsenic and sulphur. The crude tin obtained is often contaminated with iron and other metals. It is, therefore, remelted on an inclined hearth the easily fusible tin melts away, leaving behind the less fusible impurities. The molten tin is finally stirred to bring it into intimate contact with air. Any remaining metal impurities are thereby oxidised to form a scum tin dross ) on the surface and this can be skimmed off Very pure tin can be obtained by zone refining. 

Others would include the addition of materials aimed at increa sing the bioavailabiUty of the contaminant to the degrading organisms. The most studied compounds are surfactants, but cations have been reported to increase the bioavailabiUty of some organic compounds, and sorbents and clays are also considered. The dispersion of spilled oil on water by the appHcation of dispersants is perhaps the major commercial use of this idea. 

Hydrating bentonite in fresh water before adding it to the mud greatly increases its efficiency when the makeup water is contaminated with salt and/or hardness. Prehydrated bentonite can be protected from dehydration by flgnosulfonate (70) or sulfomethylated tannin when used in saturated salt water. Salt water clays, such as sepioflte and attapulgite, provide no filtration control and are normally used with suitable filtration control agents. 

Various inorganic chemicals remove soluble contaminants encountered during drilling. Salt, NaCl, is a common contaminant that can be removed only by dHution. The adverse effects of salt, primarily clay flocculation, can be overcome by a deflocculant such as a Hgnosulfonate or sulfomethylated... 

Some producers beneficiate the phosphate ore prior to agglomeration to increase the phosphate content and remove undesirable contaminants. One approach uses a water wash to remove fines which are lower in assay and higher in contamination. If too much clay is removed from the ore by the beneficiation, a binder such as bentonite clay must be added back to the ore to faciUtate agglomeration. 

Four minerals are the principal commercial sources of potash (Table 2). In all ores, sodium chloride is the principal soluble contaminant. Extraneous water-iasoluble material, eg, clay and siUca, is a significant contaminant ia some of the evaporates being mined from underground deposits. Some European potassium ores contain relatively large amounts of the mineral kieserite, MgS04-H2 0. It is recovered for captive use to produce potassium sulfate compounds or is marketed ia relatively pure form as a water-soluble magnesium fertilizer. 

Both the Toth and Alcoa processes provide aluminum chloride for subsequent reduction to aluminum. Pilot-plant tests of these processes have shown difficulties exist in producing aluminum chloride of the purity needed. In the Toth process for the production of aluminum chloride, kaolin [1332-58-7] clay is used as the source of alumina (5). The clay is mixed with sulfur and carbon, and the mixture is ground together, pelletized, and calcined at 700°C. The calcined mixture is chlorinated at 800°C and gaseous aluminum chloride is evolved. The clay used contains considerable amounts of silica, titania, and iron oxides, which chlorinate and must be separated. Silicon tetrachloride and titanium tetrachloride are separated by distillation. Resublimation of aluminum chloride is requited to reduce contamination from iron chloride. 

Water and Waste Water Treatment. PAG products are used in water treatment for removal of suspended soHds (turbidity) and other contaminants such as natural organic matter from surface waters. Microorganisms and colloidal particles of silt and clay are stabilized by surface electrostatic charges preventing the particles from coalescing. Historically, alum (aluminum sulfate hydrate) was used to neutralize these charges by surface adsorption of Al cations formed upon hydrolysis of the alum. Since 1983 PAG has been sold as an alum replacement in the treatment of natural water for U.S. municipal and industrial use. 

Spill Anatomy and Remediation. Contrary to past arguments that leaks or spills from aboveground tanks would stay near the surface, they go straight down into the aquifer and spread out. Various obstacles, such as clay lenses, rock, or impermeable layers of sod, simply divert the downward path. Slow leaks from tank bottoms tend to form a narrow plume, whereas larger spills cover much wider areas. When the contaminant reaches groundwater, it tends to be dispersed in the direction of the groundwater current and movement. 

An innovative technology called the "lasagna" process is based on the electrokinetic phenomenon called electro osmosis. The lasagna process was created to treat difficult wastes in low permeabiUty, sdt- and clay-laden soils (40). The lasagna process is so named because it consists of a number of layered subsurface electrodes and treatment zones. These layers can be constmcted either horizontally where contaminants are forced to more upward or in vertical position where lateral contaminant movement is desired. 

A U.S. EPA study (41) showed that soil vapor extraction (SVE) is an effective treatment for removing volatile contaminants from the vadose zone. Sandy soils are more effectively treated than clay or soils with higher organic content because higher air flows are possible in sand and clays—organic soils tend to adsorb or retain more contaminants. Removal of volatiles is rapid in the initial phase of treatment and thereafter decreases rapidly thereafter-an important consideration in the design of air emissions control over the life of the project. 

---