abandoned with household waste. The unstable Cd-containing waste contaminates
the environment when it is disposed of in landfill or incinerated [2, 35].
Incineration can greatly reduce the mass and volume of municipal solid waste
(MSW) [38, 39]. The process creates a considerable amount of incineration residue,
mainly composed of bottom ash and fly ash [39–41]. Unlike organic compounds,
metal species are not destroyed in high-temperature conditions and remain in the
residue. Most of them condense and convert into metallic or metal oxide particles or
airborne aerosols. Residues from the incineration of MSW are therefore usually
enriched with toxic metals such as Zn, Ni, Cr, Cu, Pb, and Cd [4, 39–41]. Concentrations of Cd from 24 to 1500 μg/m
3 have been reported for flue gas from
incinerating MSW, and most of this Cd eventually accumulates in fly ash [4]. The
largest source of Cd pollutants in MSW is Ni-Cd batteries, which contribute 60–70%
of the total Cd, and the second largest source is waste plastics [42]. Wan et al. found
Cd content of 72 mg/kg in fly ash [43]. In the fly ash from two incineration plants in
China, the Cd contents were found to be 37 and 276 mg/kg [44, 45]. Quina et al.
reported that the content of Cd in MSW residues ranged from 16 to 1660 mg/kg
[46]. Using an adsorption process to remove Cd from aqueous solutions produces a
significant amount of waste containing Cd, with 98–600 mg Cd adsorbed per gram
of adsorbent [47–52]. Before disposal, the Cd-containing waste must undergo
suitable pretreatment or stabilization to reduce its adverse effects on the environment
[38, 41, 53–56].
Cadmium can induce a great number of acute and chronic illnesses, including
renal damage, hypertension, emphysema, testicular atrophy, and cancers [34, 36, 57,
58]. Due to its high toxicity, Cd has been classified as a group 1 carcinogen
[59]. According to a WHO document, the concentration of Cd in drinking water
should not exceed 0.005 mg/L [60].
Cadmium-containing waste requires detoxification and metal stabilization before
disposal. The development of novel and environmentally friendly technology should
be adopted to control and reduce the harm of Cd-containing waste [37, 58, 61]. A
solidification/stabilization (S/S) process is commonly used for the treatment of most
metal-containing waste, preventing the hazardous substances from migrating into the
surroundings by physically fixing toxic contaminants and/or chemically bonding
them to binders [22, 62]. Figure 7.2 shows a typical S/S process for toxic metal
immobilization. In the S/S process, pollutants can be converted into less mobile,
soluble, and toxic forms using various stabilizers, additives, or binders, such as
cement, clay, fly ash, zeolite, and red mud [63].
Common S/S technologies using sorption or cementation to immobilize metals
may not reliably control metal leaching in a variety of acidic environments because
the binding effect is not satisfactory in such environments [64]. It is not possible to
fix metals, especially highly mobile metals such as Hg, Cd, and Pb, for long-term
disposal because they are easily leached when the products are in acidic conditions
[63]. Furthermore, a large amount of cement would be consumed to achieve the goal
of stabilization, which may lead to a significant increase in the volume of end
products.
7 Advances in Cadmium Detoxification/Stabilization by Sintering with Ceramic. . .
303
the environment when it is disposed of in landfill or incinerated [2, 35].
Incineration can greatly reduce the mass and volume of municipal solid waste
(MSW) [38, 39]. The process creates a considerable amount of incineration residue,
mainly composed of bottom ash and fly ash [39–41]. Unlike organic compounds,
metal species are not destroyed in high-temperature conditions and remain in the
residue. Most of them condense and convert into metallic or metal oxide particles or
airborne aerosols. Residues from the incineration of MSW are therefore usually
enriched with toxic metals such as Zn, Ni, Cr, Cu, Pb, and Cd [4, 39–41]. Concentrations of Cd from 24 to 1500 μg/m
3 have been reported for flue gas from
incinerating MSW, and most of this Cd eventually accumulates in fly ash [4]. The
largest source of Cd pollutants in MSW is Ni-Cd batteries, which contribute 60–70%
of the total Cd, and the second largest source is waste plastics [42]. Wan et al. found
Cd content of 72 mg/kg in fly ash [43]. In the fly ash from two incineration plants in
China, the Cd contents were found to be 37 and 276 mg/kg [44, 45]. Quina et al.
reported that the content of Cd in MSW residues ranged from 16 to 1660 mg/kg
[46]. Using an adsorption process to remove Cd from aqueous solutions produces a
significant amount of waste containing Cd, with 98–600 mg Cd adsorbed per gram
of adsorbent [47–52]. Before disposal, the Cd-containing waste must undergo
suitable pretreatment or stabilization to reduce its adverse effects on the environment
[38, 41, 53–56].
Cadmium can induce a great number of acute and chronic illnesses, including
renal damage, hypertension, emphysema, testicular atrophy, and cancers [34, 36, 57,
58]. Due to its high toxicity, Cd has been classified as a group 1 carcinogen
[59]. According to a WHO document, the concentration of Cd in drinking water
should not exceed 0.005 mg/L [60].
Cadmium-containing waste requires detoxification and metal stabilization before
disposal. The development of novel and environmentally friendly technology should
be adopted to control and reduce the harm of Cd-containing waste [37, 58, 61]. A
solidification/stabilization (S/S) process is commonly used for the treatment of most
metal-containing waste, preventing the hazardous substances from migrating into the
surroundings by physically fixing toxic contaminants and/or chemically bonding
them to binders [22, 62]. Figure 7.2 shows a typical S/S process for toxic metal
immobilization. In the S/S process, pollutants can be converted into less mobile,
soluble, and toxic forms using various stabilizers, additives, or binders, such as
cement, clay, fly ash, zeolite, and red mud [63].
Common S/S technologies using sorption or cementation to immobilize metals
may not reliably control metal leaching in a variety of acidic environments because
the binding effect is not satisfactory in such environments [64]. It is not possible to
fix metals, especially highly mobile metals such as Hg, Cd, and Pb, for long-term
disposal because they are easily leached when the products are in acidic conditions
[63]. Furthermore, a large amount of cement would be consumed to achieve the goal
of stabilization, which may lead to a significant increase in the volume of end
products.
7 Advances in Cadmium Detoxification/Stabilization by Sintering with Ceramic. . .
303