1. USING JOB’S METHOD TO DETERMINE THE STOICHIOMETRIC RATIO OF A METAL-AMINOPOLYCARBOXYLATE
COMPLEX IN A NON-AQUEOUS MEDIUM
Nsombi J. Roberts
Department of Chemistry, Southern University and A&M College
Baton Rouge, LA
INTRODUCTION
First world countries are plagued with high density industrialized areas that produce large
amounts of pollutants on a daily basis. This is not to be confused with the general term for
unwanted remains and byproducts or waste that these corporations expel. A pollutant is
described as a waste material that pollutes or contaminates the environment. Pollution is
categorized into several different groups: air, thermal, soil, radioactive, and water. Water
pollution occurs when pollutants spread from a source to the environment, leaving natural
resources such as water systems fouled by human existence. Contaminated water sources
can contain various dense, potentially toxic metals or heavy metals that are a danger to the
human condition. The heavy metals of major health concern are cadmium, mercury, lead
and arsenic. Other heavy metals that are less toxic are manganese, chromium, cobalt,
nickel, copper, zinc, selenium, silver, antimony and thallium. These heavy metals can only
be removed through transformation from one oxidation state or organic complex to
another. As of 2016, the major environmental issue at hand in the United States is the
drinking water contamination crisis in Flint, Michigan. The city of Flint is currently in a
federal state of emergency which allows the federal government to take the forefront on
handling the issue at hand. The drinking water for the city of Flint was switched from the
same source used by the city of Detroit to the Flint River, a previous back up source. The
city originally did not use the Flint River as a primary source because the overall cost for the
treatment of that water was more expensive than water from Lake Huron, Detroit’s current
water source.. The water from the Flint River was contaminated by lead that leached into
the water system from outdated pipes. Leaching is described as the process of removing a
soluble mineral or chemical from a solid source with a liquid either naturally or through
forced means. The improper treatment of the water and the ineffective methods used to
remove the leached lead posed a serious health risk to the citizens of Flint. Lead is the
second most hazardous metal according to the Priority List of the US Environmental
Protection Agency. News stations across the country displayed the unnatural discoloration
of water in the homes of dozens of Flint residents. Many children were found having highly
elevated levels of lead in their blood stream which translates to lead poisoning. Lead
poisoning can lead to “deficits in intellectual functioning, academic performance, problem
solving skills, motor skills, memory and executive functioning are consistently observed in
lead-exposed children, in addition to an increased likelihood of experiencing ADHD and
having conduct problems in childhood, and decreased brain volume in adulthood.” Green
chemistry is “the utilization of a set of principles that reduces or eliminates the use or
generation of hazardous substances in the design, manufacture, and applications of
chemical products.” It is upon this foundation that purification systems were born. Water
purification methods are costly to the average citizen forced by their social economic status
to live in these nearly uninhabitable areas. The current green chemistry methods in place,
while less costly and efficient, employ an aminopolycarboxylic acid that is a suspected
carcinogenic to humans.. The increasing world population has led to a rapid increase in
pollution. The increasing cost of pollutant removal has led the world to turn to producing
newer methods. There is a need for a sequestering agent that has effectiveness in removing
heavy metals from solutions, has minimum health effect, and is cost efficient. Pollutants in
water systems and soils negatively affect the lifecycles of plants and animals, ultimately
affecting human life. Metal removal from aqueous and non-aqueous solutions through the
use of an aminopolycarboxylic acid can be a cheaper and more efficient purification
process. The purpose of this study is to develop a green chemistry method for removing
pollutants from aqueous or non-aqueous solvents.
ABSTRACT
The increasing world population has led to a rapid increase in
pollution. The increasing cost of pollutant removal has led the
world to turn to producing newer, cheaper, and safer methods.
There is a need for a sequestering agent that has effectiveness in
removing heavy metals from solutions, has minimum health
effect, and is cost efficient. This study sets to utilize an
aminopolycarboxylic acid to develop a method that is effective in
removing pollutants from aqueous and non-aqueous mediums.
The titrimetric methods of analysis were used to develop a
method that is cheap and safe for removing pollutants such as
toxic metals from non-aqueous and aqueous mediums. The
physiochemical properties of the aminopolycarboxylic acid
observed were used to develop a method that is cheap and safe
for removing pollutants such as toxic metals from non-aqueous
solutions. 3, 3’, 3”-Nitrilotripropionic acid (NTP) was synthesized
from acrylic acid and β-Alanine using Michael Addition and
coordinated to a metal complex in a non-aqueous solution. The
method of continuous variation was used to find the
stoichiometric ratio of the metal complex.
Specific Aim 1: Synthesis of 3, 3’, 3” –
Nitrilotriproionic acid from β-Alanine
and acrylic acid.
Specific Aim 2: Coordination of synthesized 3, 3’, 3” –
Nitrilotriproionic acid to Cupric chloride in a non-
aqueous medium using the Job’s Method
Results Conclusion
From the solubility test and melting point test, it can be concluded that NTP was
successfully made. The process of forming NTP from b-alanine and acrylic acid was
faster than previous methods and produced a substantial yield. The conclusion that the
time-consuming process is due to the third step of reaction has been disproven. Due to
the first leg of NTP already being attached, it can be concluded that the formation of
the primary amine compound, the first step, is the rate limiting step. It has also been
concluded that NTP fully deprotonates in basic mediums, making it the optimal
environment for coordination to metal ion. This confirms the pH dependency of NTP
coordination. Future studies of NTP coordination should be conducted in basic
mediums or with a salt form of NTP to allow maximum potential for coordination. The
NTP ligand successfully coordinated to Copper, as observed by the distinct color
changes with varying metal to ligand ratios. A single new peak emerged at 726.7 nm at
a metal to ligand ratio of 1:9, giving a starting point for future studies for finding the to
the stoichiometric ratio. Other methods such as the mole-ratio and slope-ratio methods
should be examined to find an exact ratio.
Acknowledgments
Dr. Scott A. Wicker
Southern University Chemistry Department
Zeta Phi Beta Sorority, Inc.
Dolores Margaret Richard Spikes Honors College
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Michael Addition Synthesis of NTP
Titration of NTP in NaOH
Volume
NTP (L)
moles of
NTP
Volume
Copper (II)
Chloride (L)
moles of
Copper (II) ion
Total Moles
Mole Fraction
of Ligand
Mole
Fraction of
Metal
Mole Ratio of
Ligand to
Metal
0 0.0000E+00 0.005 1.0265E-05 1.0265E-05 0 1 0/1
0.0005 1.0265E-06 0.0045 9.2385E-06 1.0265E-05 0.1 0.9 1/9
0.001 2.0530E-06 0.004 8.2120E-06 1.0265E-05 0.2 0.8 1/4
0.0015 3.0795E-06 0.0035 7.1855E-06 1.0265E-05 0.3 0.7 3/7
0.002 4.1060E-06 0.003 6.1590E-06 1.0265E-05 0.4 0.6 2/3
0.0025 5.1325E-06 0.0025 5.1325E-06 1.0265E-05 0.5 0.5 1/1
0.003 6.1590E-06 0.002 4.1060E-06 1.0265E-05 0.6 0.4 3/2
0.0035 7.1855E-06 0.0015 3.0795E-06 1.0265E-05 0.7 0.3 7/3
0.004 8.2120E-06 0.001 2.0530E-06 1.0265E-05 0.8 0.2 4/1
0.0045 9.2385E-06 0.0005 1.0265E-06 1.0265E-05 0.9 0.1 9/1
0.005 1.0265E-05 0 0.0000E+00 1.0265E-05 1 0 1/0
Molarity of
NTP (M)
Molarity of
Copper (II)
Chloride (M)
Total Volume
(mL)
0.002053 0.002053 5
Phase Diagram for NTP with Copper (II) Chloride
in DMSO
Varying ratios (M:L) of 2mM Copper (II) chloride and
2mM NTP in DMSO. From left to right: 1:0, 9:1, 8:2, 7:3,
6:4, 5:5, 4:6, 3:7, 2:8, 1:9, 0:1.
Varying ratios (M:L) of 0.05M Copper (II) chloride and
0.05M NTP in DMSO. From left to right: 1:0, 9:1, 8:2, 7:3,
6:4, 5:5, 4:6, 3:7, 2:8, 1:9, 0:1.
0
0.1
0.2
0.3
0.4
0.5
0.6
380 480 580 680 780 880
Absorbance
Wavelength (nm)
Continuous Variation of 0.002M CuCl_2 and 0.002M NTP in DMSO
1:0
9:1
8:2
7:3
6:4
5:5
4:6
3:7
2:8
1:9
0:1
Metal to
Ligand Ratio
Peak= 391.6 nm
Copper (II) chloride in
water and Copper (II)
chloride in DMSO
Enhanced spectrum of 2mM NTP and 2mM Copper
(II) Chloride in DMSO at (from top left to right to
bottom left to right) metal to ligand ratios of 4:6,
3:7, 2:8, and 1:9
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
380 480 580 680 780 880
Absorbance
Wavelength (nm)
Absorbance of 1:9 0.05M CuCl_2 and 0.05M NTP in DMSO
Peak= 726.7 nm