Environmental Engineering Reference
In-Depth Information
insecticidal and molluscicidal activities) and repellent activities against wood-
destroying organisms, marine animals, marine plants, rodents, etc.
The industrial uses of the organotin compounds, utilizing the first char-
acteristic, are as stabilizers for PVC and the other vinyl polymers, and
as catalysts. The industrial uses utilizing the second characteristic are as
wood preservatives, antifouling agents, agrochemicals, pharmaceuticals, dis-
infectants, rodent repellents, masonry and stonework-protecting agents, and
slime-preventing agents, etc. Other minor uses of organotin compounds are
in glass applications (such as easy handling of raw materials by using inor-
ganic tin compounds (SnO
2
), flame retardants, etc.) [16].
The industrial applications of the organotin compounds are shown in
Table 1 [16-22].
In 1950, the annual production of organotin compounds was only around
50 tons. This rose to 2000 tons in 1960 and 16 000 tons in 1970, and production
in the mid-1980s was estimated at over 40 000 tons [15].
As discussed by Blunden et al. [18] in 1985, the most important use of
the organotins was as PVC stabilizers (ca. 70%); biocidal uses such as an-
tifoulants, agrochemicals and wood preservatives, are ca. 20%. Around 3500
tons per year were used as organotin antifoulants.
2.2
Properties of Organotin Compounds
Organotin compounds are one of the organometallic compounds, since they
have the characteristic metal-carbon bonds. However, they are very different
from general organometallic compounds, especially, from organotransition
metal compounds in their stability. For example, tetramethyltin is very sta-
ble, and it decomposes between 440 and 493
◦
C over a range between 5 and
185 mm Hg initial pressure [23].
Basic organotin compounds, their related compounds and their physical
properties are shown in Table 2 [4, 16, 24]. They are liquid or solid at room
temperature, and they are stable and easy to handle.
Tributyltin (TBT) has a low aqueous solubility and relatively high affin-
ity for particulate matter, providing a direct and potentially persistent route
of its entry into benthic sediment. The need to determine the fate of TBT in
such environments is consequently a priority issue, as the sediment becomes
the major reservoir for this pollutant. Initial tests are shown in Fig. 1 [25].
The sorption of TBT to the sediment was rapid so that the major propor-
tion was taken up within 10 min and an equilibrium was achieved within
2 h, when 85.7% of the added TBT had bound with suspended particles in
the dark at 15
◦
C [25]. The difference of affinities of the organotin com-
pounds with water and sediment relates to the difference of the half-lives of
organotin compounds in water and the sediment as described in the next
section.
