NMP Residues Treatment: Environmental Impacts and Risk Levels

This report comprehensively examines the environmental impact and ecotoxicity risks associated with N-Methyl-2-pyrrolidone (NMP) residues. It begins by outlining the properties of NMP, including its miscibility, solubility, and uses in various industries, such as petrochemicals and microelectronics. The report then explores NMP's environmental fate, including its potential for atmospheric emissions, water contamination, and soil mobility. It details the substance's biodegradation processes, highlighting its rapid degradation in various environments. Furthermore, the report assesses the toxicity of NMP, detailing its effects on organisms through various exposure routes, including inhalation, ingestion, and dermal absorption. It discusses studies in both rodents and humans, noting the metabolic pathways and potential health effects. The report also addresses the impact of NMP on corrosion in carbon steel, discussing how the presence of organic solvents like NMP and methanol can affect corrosion rates. This analysis includes mass loss measurements, surface image scanning using FESEM, and EDX to characterize corrosion behavior, providing a detailed understanding of NMP's environmental and health implications.

Experimental error
The weight loss was got using the weighing balance and the difference in weigh for each week
was then compute that is the difference between the weight of each coupon before and after each
week of the sample immersion in the different environments. To offer a minimum uncertainty in
the corrosion rate, this methods will implicitly assumes: the area does not vary as mass is loss to
corrosion, the corrosion rate does not vary with the exposure time, the actual and the projected
surfaces area are the similar, the penetration rate is uniform over the whole surface, the weight is
unaffected by corrosion product removal, and even assuming that the above criteria are fulfilled,
errors can be still be propagated due to the uncertainty in the measurement of dimensions, mass,
and time.
Environmental impacts of the treatment of NMP residues and their level of risk of eco-
toxicity
N-Methyl-2-pyrrolidone (NMP) is a water-miscible and hydroscopic organic solution with a
mild amine odour. It is a basic and polar compound with high stability. It is only slowly oxidized
by air and is easily purified by fractional distillation. NMP is hygroscopic. The substance is
completely miscible with water. It is highly soluble in lower alcohols, lower ketones, ether, ethyl
acetate, chloroform, and benzene and moderately soluble in aliphatic hydrocarbons. The solution
is utilised in the petrochemical industry, in the microelectronics fabrication industry, and the
production of many compounds such as cosmetics, drugs, fungicides, insecticides and
fungicides. An increasing application of NMP is an alternative for chlorinated hydrocarbons.
NMP may enter the environment as emissions to the atmosphere, as the substance is volatile and
widely used as a solvent, or it may be released to water as a component of municipal and

industrial wastewaters. The substance is mobile in soil, and leaching from landfills is thus a
possible route of contamination of groundwater. In air, NMP is expected to be removed by wet
deposition or by photochemical reactions with hydroxyl radicals. As the substance is completely
miscible in water, it is not expected to adsorb to soil, sediments, or suspended organic matter or
to bio concentrate. NMP is not degraded by chemical hydrolysis. Data from screening tests on
the biodegradability of NMP show that the substance is rapidly biodegraded.
In rats, NMP is absorbed rapidly after inhalation, oral, and dermal administration, distributed
throughout the organism, and eliminated mainly by hydroxylation to polar compounds, which are
excreted via urine. About 80% of the administered dose is excreted as NMP and NMP
metabolites within 24 h. A probably dose dependent yellow coloration of the urine in rodents is
observed. The major metabolite is 5-hydroxy-N-methyl-2- pyrrolidone. Studies in humans show
comparable results. Dermal penetration through human skin has been shown to be very rapid.
NMP is rapidly bio transformed by hydroxylation to 5-hydroxy-N-methyl-2-pyrrolidone, which
is further oxidized to N-methylsuccinimide; this intermediate is further hydroxylated to 2-
hydroxy-Nmethylsuccinimide. These metabolites are all colorless. The excreted amounts of
NMP metabolites in the urine after inhalation or oral intake represented about 100% and 65% of
the administered doses, respectively. NMP has a low potential for skin irritation and a moderate
potential for eye irritation in rabbits. Repeated daily doses of 450 mg/kg body weight
administered to the skin caused painful and severe haemorrhage and Escher formation in rabbits.
These adverse effects have not been seen in workers occupationally exposed to pure NMP, but
they have been observed after dermal exposure to NMP used in cleaning processes. No
sensitization potential has been observed. In acute toxicity studies in rodents, NMP showed low
toxicity. Uptake of oral, dermal, or inhaled acutely toxic doses causes functional disturbances

and depressions in the central nervous system. Local irritation effects were observed in the
respiratory tract when NMP was inhaled and in the pyloric and gastrointestinal tracts after oral
administration. In humans, there was no irritative effect in the respiratory system after an 8-h
exposure to 50 mg/m3. There is no clear toxicity profile of NMP after multiple administrations.
In a 28-day dietary study in rats, a compound-related decrease in body weight gain was observed
in males at 1234 mg/kg body weight and in females at 2268 mg/kg body weight. Testicular
degeneration and atrophy in males and thymic atrophy in N-Methyl-2-pyrrolidone 5 females
were observed at these dose levels.
The toxicity profile after exposure to airborne NMP depends strongly on the ratio of vapor to
aerosol and on the area of exposure (i.e., head-only or whole-body exposure). Because of higher
skin absorption for the aerosol, uptake is higher in animals exposed to aerosol than in those
exposed to vapor at similar concentrations. Studies in female rats exposed head only to 1000
mg/m3 showed only minor nasal irritation, but massive mortality and severe effects on major
organs were observed when the females were whole-body exposed to the same concentration of
coarse droplets at high relative humidity. Several studies in rats following repeated exposure to
NMP at concentrations between 100 and 1000 mg/m3 have shown systemic toxicity effects at the
lower dose levels. In most of the studies, the effects were not observed after a 4-week
observation period.
The vapor pressure of NMP (39–45 Pa) suggests that the substance will volatilize from dry
surfaces. Based on this value, substantial volatilization from water is not expected. According to
a simple fugacity calculation, more than 99% of NMP released into the environment will
partition to water (assuming equilibrium distribution). In the atmosphere, NMP is expected to
undergo a rapid gas-phase reaction with hydroxyl radicals; with an estimated half-life of 5.2 h.

Reaction with (tropospheric) ozone is expected to be an insignificant route of removal from the
atmosphere. Because of its high solubility in water, NMP may undergo atmospheric removal by
wet deposition. A calculated adsorption coefficient of 9.6 indicates that NMP is highly mobile in
soil. Soil thin-layer chromatography also indicates a high mobility in soil, RF values being 0.65–
1.0 in four different soils. The calculated adsorption coefficient further indicates that adsorption
to sediments or suspended organic matter in aquatic environments should be insignificant. The
dissipation of NMP showed half-lives of about 4 days in clay, 8 days in loam, and 12 days in
sand. Invalidated data on hydrolytic half-lives suggest that NMP is not degraded by chemical
hydrolysis. Screening studies using activated sludge indicate that NMP is biodegraded
aerobically after a lag phase of a few days. 95% degradation after 2 weeks was shown in a static
die-away system, and an average 7-day biodegradability of 95% was shown in a semi continuous
activated sludge system. A stable carbonyl compound was identified as a biodegradation product.
In a test conducted according to Guideline 301C of the Organisation for Economic Co-operation
and Development, 73% of an initial concentration of 100 mg NMP/liter was degraded within 28
days of incubation by the non-adapted activated sludge. From this result, NMP has been
classified as readily biodegradable under aerobic conditions. After 24 h, NMP underwent 94%
removal by 1-day acclimatized sludge, measured by chemical oxygen demand (COD). In a flow-
through biological treatment system with a retention time of 18 h, NMP underwent >98%
removal. In an inherent biodegradability study (SCAS test), NMP was removed to >98% as
measured by COD after 24 h. In another inherent biodegradability study, removal of COD was
>90% after 8 days, with a 3- to 5-day acclimation period. From NMP’s calculated bio
concentration factor of 0.16 and its low log octanol–water partition coefficient of! 0.38, only a
minor potential for bioaccumulation is to be expected.

In humans, as in rats, NMP is rapidly absorbed via inhalation, ingestion, and dermal
administration. An uptake of about 90% by the inhalation route was found when the difference
between inhaled and exhaled NMP concentrations was calculated. NMP is rapidly bio
transformed by hydroxylation to 5-HNMP, which is then further oxidized to MSI; MSI is in turn
hydroxylated to 2- HMSI. The peak plasma concentrations after an 8-h exposure to NMP
occurred at the termination of exposure for NMP, at 2 h post-exposure for 5-HNMP, at 4 h post-
exposure for MSI, and at 16 h post-exposure for 2- HMSI. The half-lives in plasma after a short
period of distribution were 4 h, 6 h, 8 h, and 16 h, respectively. The detected amounts in urine
after inhalation were as follows: NMP (2%), 5-HNMP (60%), MSI (0.1%), and 2- HMSI (37%).
The recovery was about 100%. After oral administration, the amounts detected in urine were as
follows: NMP (1%), 5-HNMP (67%), MSI (0.1%), and 2- HMSI (31%), corresponding to 65%
of the administered dose. There was no tendency for coloration in any of the urine samples
collected, and none of the synthesized metabolites was coloured. In a 6-h topical single-
application study with administration of 300 mg NMP in volunteers, the NMP concentration in
plasma reached a maximum 3 h after application in both males and females. Twenty-four per
cent and 22% of the dose in males and females,