Page 59 - Energy from Toxic Organic Waste for Heat and Power Generation

Toxic Waste From Textile Industries 47

4.7 HYDROCARBON SOLVENTS—ALIPHATIC
HYDROCARBONS

An aliphatic compound is a hydrocarbon compound containing carbon
and hydrogen joined together in straight chains, branched trains, or nonaro-
matic rings. Aliphatic compounds may be saturated (e.g., hexane and other
alkanes) or unsaturated (e.g., hexene and other alkene, as well as alkynes)
[15]. The aliphatic hydrocarbons present in the effluent of the textile indus-
try [16] are cyclohexene (C 6 H 10 ), cyclohexane (C 6 H 12 ), n-hexane (C 6 H 14 ),
n-heptane (C 7 H 16 ), pentane (C 5 H 12 ), and petroleum ether.
Most aliphatic compounds are flammable, allowing the use of hydro-
carbons as fuel. Aliphatic hydrocarbons are asphyxiants and central nervous
system (CNS) depressants. Serious toxic effects of aliphatic hydrocarbons
include asphyxia and chemical pneumonitis for many paraffins, axonal neu-
ropathy for n-hexane, and cancer for 1,3-butadiene [17].

4.8 HYDROCARBON SOLVENTS—AROMATIC
HYDROCARBONS

Effluents of textile-dyeing plants are extremely difficult to treat due to their
high content of pollutants such as polycyclic aromatic hydrocarbons (PAHs)
[18]. Some of the aromatic hydrocarbons found in the textile effluent are
benzene (C 6 H 6 ), naphthalene (C 10 H 8 ), toluene (C 7 H 8 ), and xylenes or
dimethylbenzene (C 8 H 10 ).
Most PAHs do not dissolve easily in water. They stick to solid particles and
settle to the bottoms of lakes or rivers. In soils, PAHs are most likely to stick
tightly to particles; certain PAHs move through soil to contaminate under-
ground water. Some people who have breathed or touched mixtures of PAHs
and other chemicals for long periods of time have developed cancer [19].

4.9 OXYGENATED SOLVENTS (ALCOHOLS/GLYCOLS/
ETHERS/ESTERS/KETONES/ALDEHYDES)
An oxygenated solvent contains oxygen molecule, with high solvency
and low toxicity. These solvents are widely used in textile processing and
found in the effluent of the textile industry [20]. Such oxygenated sol-
vents are methanol (CH 3 OH), ethanol (C 2 H 5 OH), propanol (C 3 H 7 OH),
butanol (C 4 H 9 OH), ethylene glycol (C 2 H 6 O 2 ), diethyl ether ((C 2 H 5 ) 2 O),