Table 11165 Summary Of Factors That May Interfere With Solidification Processes

Characteristics Affecting Processing Feasibility

Potential Interference

Organic compounds Semivolatile organics or poly-

aromatic hydrocarbons (PAHs) Oil and grease

Fine particle size


Soluble salts of manganese, tin, zinc, copper, and lead Cyanides

Sodium arsenate, borates, phosphates, iodates, sulfides, and carbohydrates Sulfates


Presence of coal or lignite Sodium borate, calcium sulfate, potassium dichromate, and carbohydrates Nonpolar organics (oil, grease, aromatic hydrocarbons, PCBs) Polar organics (alcohols, phenols, organic acids, glycols) Solid organics (plastics, tars, resins) Oxidizers (sodium hypochlorite, potassium permanganate, nitric acid, or potassium dichromate) Metals (lead, chromium, cadmium, arsenic, mercury) Nitrates, cyanides Soluble salts of magnesium, tin, zinc, copper and lead Environmental/waste conditions that lower the pH of matrix Flocculants (e.g., ferric chloride) Soluble sulfates >0.01% in soil or T50 mg/L in water Soluble sulfates >0.5% in soil or 2000 mg/L in water Oil, grease, lead, copper, zinc, and phenol Aliphatic and aromatic hydrocarbons Chlorinated organics Metal salts and complexes Inorganic acids Inorganic bases

Organics may interfere with bonding of waste materials with inorganic binders.

Organics may interfere with bonding of waste materials.

Weaken bonds between waste particles and cement by coating the particles. Decrease in unconfined compressive strength with increased concentrations of oil and grease.

Insoluble material passing through a No. 200 mesh sieve can delay setting and curing. Small particles can also coat larger particles, weakening bonds between particles and cement or other reagents. Particle size >Af inch in diameter not suitable.

May retard setting, easily leached for cement and pozzolan S/S. May dehydrate thermoplastic solidification.

Reduced physical strength of final product caused by large variations in setting time and reduced dimensional stability of the cured matrix, thereby increasing leachability potential.

Cyanides interfere with bonding of waste materials.

Retard setting and curing and weaken strength of final product.

Retard setting and cause swelling and spalling in cement S/S. With thermoplastic solidification may dehydrate and rehydrate, causing splitting. Marked decreases in compressive strength for high phenol levels.

Coals and lignites can cause problems with setting, curing, and strength of the end product. Interferes with pozzolanic reactions that depend on formation of calcium silicate and aluminate hydrates.

May impede setting of cement, pozzolan, or organic-polymer S/S. May decrease long-term durability and allow escape of volatiles during mixing. With thermoplastic S/S, organics may vaporize from heat.

With cement or pozzolan S/S, high concentrations of phenol may retard setting and may decrease short-term durability; all may decrease long-term durability. With thermoplastic S/S, organics may vaporize. Alcohols may retard setting of pozzolans.

Ineffective with urea formaldehyde polymers; may retard setting of other polymers.

May cause matrix breakdown or fire with thermoplastic or organic polymer S/S.

May increase setting time of cements if concentration is high. Increase setting time, decrease durability for cement-based S/S.

May cause swelling and cracking within inorganic matrix exposing more surface area to leaching. Eventual matrix deterioration.

Interference with setting of cements and pozzolans. Endangerment of cement products due to sulfur attack. Serious effects on cement products from sulfur attacks.

Deleterious to strength and durability of cement, lime/fly ash, fly ash/cement binders. Increase set time for cement.

May increase set time and decrease durability of cement if concentration is high. Increase set time and decrease durability for cement or clay/cement. Decrease durability for cement (Portland Type I) or clay/cement.

Decrease durability for clay/cement; KOH and NaOH decrease durability for Portland cement Type III and IV.

Source: Reprinted from U.S. EPA, 1991.

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