Environmental Engineering Reference
In-Depth Information
Werner's theory on the nature of coordination compounds, awarded 1913 with the
Nobel Prize in Chemistry [ 26 , 27 ]. Another prominent example of a metal
ammine complex is Cisplatin, PtCl 2 (NH 3 ) 2 , currently one of
the most widely
used anticancer drugs in the world [ 28 ].
Just over one century has passed since Fritz Haber's Nobel-prize-winning work
on ammonia synthesis, in which he showed how ammonia could be synthesized
from its constituent parts, under high pressure, high temperature conditions in the
presence of an iron-containing catalyst (equation 12 ).
N 2 þ
3H 2 !
2NH 3
ð
12
Þ
This discovery led to the production of ammonia from atmospheric N 2 on an
industrial scale, thereby enabling agricultural intensification across the globe.
The equipment for the industrial production of ammonia was developed by the
engineer, Carl Bosch, so the process is called the Haber-Bosch process. Historically
and practically, it is closely associated with the Ostwald process in providing its
requisite raw material, NH 3 .
Unfortunately, the amount of reactive nitrogen entering the environment
has significantly increased as a result, leading to a host of ecological problems
[ 29 , 30 ]. Ammonia is a gas readily released into the air from a variety of
biological sources, as well as from industrial and combustion processes. It is the
most prevalent alkaline gas in the atmosphere. While NH 3 has many beneficial
uses, it can detrimentally affect the quality of the environment through acidifica-
tion and eutrophication of natural ecosystems, the associated loss of biodiversity,
and the formation of secondary particles in the atmosphere, which can reduce
visibility [ 31 ]. In the lower atmosphere, ammonia reacts readily with compounds
such as nitric acid (HNO 3 ) and sulfuric acid (H 2 SO 4 ) to form ammonium partic-
ulates and aerosols. Fine fraction particulate matter, including ammonium sulfate
[(NH 4 ) 2 SO 4 ] and ammonium nitrate (NH 4 NO 3 ), has been linked to medical con-
ditions such as asthma, and ammonium aerosols may influence the global climate
by altering the transmission of atmospheric and terrestrial radiation [ 32 , 33 ].
Anthropogenic perturbations of the nitrogen cycle originate from production
of energy and food to sustain human populations, which cause the release of
reactive nitrogen compounds, principally as nitrogen oxides (NO, NO 2 ), nitrous
oxide (N 2 O), nitrate, and ammonia. Human activities have more than doubled the
annual production of reactive nitrogen to satisfy human needs for food, energy,
fiber, and other products [ 34 - 36 ]. In consequence, the biogeochemical nitrogen
cycle has become severely unbalanced in recent decades and one main reason
for this fact is the anthropogenic supply of reduced nitrogen to the biosphere in
the form of NH 3 /NH 4 , for example during environmental fertilization and
livestock farming.
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