WASTE ENCAPSULATION

Heavy metal contamination of soil and water supplies has steadily increased as a result of over population and the expansion of industrial activities (Wang & Peng, 2010). The presence of heavy metals in the environment is of significant concern due to their toxicity to humans, animals, and plants.

Pollutants include cyanide, silver, cobalt, aluminum, magnesium, arsenic, copper, iron, lead, and mercury. The application of natural zeolites for water treatment is a promising technique in the environmental cleaning process (Wang & Peng, 2010). The utilization of natural zeolites has focused on the removal of ammonium and heavy metals through ion exchange.

Encapsulation is a waste disposal method that packs hazardous materials in containers made of impervious and non-reactive material. The containers are sealed with concrete, plastic, or steel for burial or storage. In the United States, Portland cement is commonly used in the encapsulation process because it is inexpensive, highly alkali, and can incorporate wet waste (Hogg & Koop, 2001).

Hogg and Koop (2001) stated that the use of natural zeolite as a binding material prior to encapsulation capitalizes on the unique ability to absorb, trap, and immobilize the contaminants in the zeolite structure (Hogg & Koop, 2001, p. 2). When contaminants are confined, they do not interfere with the concrete development process. Lab results also indicate that there is a reduction in the amount of leachable contaminant when zeolite is included in concrete formation (Hogg & Koop, 2001).

In the process of waste encapsulation, zeolite stabilizes contaminants and contributes to the integrity and corrosion resistance of concrete (Hogg & Koop, 2001). Stabilization occurs in five ways: volatile organic compounds are captured by molecular sieving; non-volatile organics are adsorbed onto the surface area of zeolite grains; heavy metals are trapped by ion exchange; radioactive cations are trapped by ion exchange; metals are immobilized by the hydrogen bonding of oxyanions (Hogg & Koop, 2001).

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