(562b) Analysis of the leachates of the monoliths from cementhazardous waste ash mixture
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Environmental Division
Poster Session: Environmental Division
Wednesday, November 13, 2019 - 3:30pm to 5:00pm
Fly ash may come from different industries, whether from thermoelectric plants or incineration
plants. Fly ash may have a high toxic character derived from heavy metals, chloride salts and
organochlorine compounds. Generally, the content of heavy metals in fly ash is higher due
to the vaporization of metals during the combustion process and in parallel with the process
of adsorption of metals on the surface of the ash. They may contain traces of polycyclic
organic compounds, PCBs, dioxins, furans, among others. They have high contents of silicon
and aluminum oxides (crystal formers), sodium and potassium oxides (fluxing agents),
calcium, magnesium, zinc and lead oxides (stabilizers). The objective of this work was to
evaluate the capacity of Portland cement to encapsulate ashes of hazardous waste by means
of analysis of leaching of metals by simulation of acid rain conditions. The percentage of
replacement in cement monoliths for hazardous waste was 10% and for treated hazardous
waste it was 3% and 5%, all at a water-cement material ratio of 0.5. The already processed
monoliths are stored in a curing room that is at a temperature of 23 °C and a relative humidity
of 95%. The leaching tests were carried out at the ages of 1, 3, 7, 14 and 28 days. A monolith
was taken from each type of ash and the target for the test. The SPLP fluid will be prepared
by water and a mixture of H2SO4/HNO3 in a 60/40 weight-to-weight ratio adjusting the pH to
4.2∓0.05. The monolith is introduced into a bottle and 250 ml of SPLP fluid is added, and left
to stand for 24 hours, and then the fluid is filtered into extraction bottles preserved with nitric
acid for metal reading by ICP-OES. It was found that the only parameters that exceed
international standards are calcium and sodium, but these are not considered within
international standards as dangerous heavy metals. Likewise, the heavy metals detected in
the sample are below the limit of detection of the equipment and the regulations. Therefore,
the confinement that is given from the cement-ash matrix is considered good and this type of
stabilization processes can be carried out.
plants. Fly ash may have a high toxic character derived from heavy metals, chloride salts and
organochlorine compounds. Generally, the content of heavy metals in fly ash is higher due
to the vaporization of metals during the combustion process and in parallel with the process
of adsorption of metals on the surface of the ash. They may contain traces of polycyclic
organic compounds, PCBs, dioxins, furans, among others. They have high contents of silicon
and aluminum oxides (crystal formers), sodium and potassium oxides (fluxing agents),
calcium, magnesium, zinc and lead oxides (stabilizers). The objective of this work was to
evaluate the capacity of Portland cement to encapsulate ashes of hazardous waste by means
of analysis of leaching of metals by simulation of acid rain conditions. The percentage of
replacement in cement monoliths for hazardous waste was 10% and for treated hazardous
waste it was 3% and 5%, all at a water-cement material ratio of 0.5. The already processed
monoliths are stored in a curing room that is at a temperature of 23 °C and a relative humidity
of 95%. The leaching tests were carried out at the ages of 1, 3, 7, 14 and 28 days. A monolith
was taken from each type of ash and the target for the test. The SPLP fluid will be prepared
by water and a mixture of H2SO4/HNO3 in a 60/40 weight-to-weight ratio adjusting the pH to
4.2∓0.05. The monolith is introduced into a bottle and 250 ml of SPLP fluid is added, and left
to stand for 24 hours, and then the fluid is filtered into extraction bottles preserved with nitric
acid for metal reading by ICP-OES. It was found that the only parameters that exceed
international standards are calcium and sodium, but these are not considered within
international standards as dangerous heavy metals. Likewise, the heavy metals detected in
the sample are below the limit of detection of the equipment and the regulations. Therefore,
the confinement that is given from the cement-ash matrix is considered good and this type of
stabilization processes can be carried out.