Equilenin comes from the steroidal estrogen family
Equilenin comes from the steroidal estrogen family and was discovered by A. Girard and his colleagues in 1932. It is one of the estrogens that are made only during pregnancy from mares. It is excreted to the environment through the pregnant mares’ urine. Equilenin binding capability to the estrogen receptor is similar to that of 17B-estradiol. It is a naturally occurring isomer that can be synthesized in a lab. The first successful experiment was done by Wayne Cole and W.E. Bachmann in 1939. In 1940, the scientists were able to synthesis some stereoisomer of equilenin.
In conjunction with equilin and other equine estrogens, equilenin is a component of a drug called Premarin. The drug was developed in 1941 by Wyeth, and it used hormone therapy for treating vaginal irritation and dryness and hot flashes in women that have experienced hysterectomies. However, the drug has several side effects and has been replaced by other drugs in some countries.
The molecular formula for Equilenin is C18H18O2, and it has a formula weight of 266.33g/mol. Its purity is 98% or more, and it a solid in its natural form. Its formal name is 3-hydroxy-estra-1,3,5,7,9-pentaen-17-one. Its melting point is between 2580C and 2590C. Equilenin’s water solubility is approximately 1.5mg/L, and it is soluble in water, benzene, alkali hydroxide solutions, dioxane, acetone, and chloroform.
.Its crystals are orthorhombic with the Carbon atoms of the first and second ring being coplanar. On the third ring, the Carbon atoms have a sofa conformation and an envelope conformation in the fourth ring. The molecules in the crystals are connected by the O-H⋯O hydrogen bonds that result in chains that are lying parallel to the c-axis.
Equilinen has a Hydrogen Bond Donor Count of 1 and a Hydrogen Bond Acceptor Count of 2. The Rotatable bond is 0 with an XLogP3-AA of 2.9. Its exact mass is 268.14633 g/mol, and this is equal to its monoisotopic weight. Its heavy atom count is 20 and it has a topological polar surface area of 37.3 Ų.
Equilenin is emerging as a contaminant of drinking. It is an emerging concern that the United States Environmental Protection Agency (EPA) has listed in on the contaminant candidate list 3 (CCL 3). Just like other steroidal estrogens, it is continuously discharged from sewage treatments works. This contaminated water then flows to surface water and ends up contaminating this clean water. As the water is treated, the compound stays in the water and used for humans. A buildup of Equilenin in humans disrupts a person’s normal processes resulting in adverse effects. Hence the need to remove the contaminant from drinking water.
The removal of Equilenin and other steroidal estrogens form water can be in three categories. It can be done through physical removal that can be through activated carbon, reverse osmosis, or nanofiltration. Secondly, the contaminant can be removed through biodegradation that involves the use of weed beds, bioreactors, and activated sludge. Finally, Equilenin can be removed from water through the use of advanced oxidation processes (AOP) that can be different techniques such as ozonation, ultrasound, Fenton’s oxidation, and a combination of the advanced technologies with different chemical treatment methods. However, using biodegradation methods is not efficient, and it is overly dependent on other factors such as temperature, water quality, and variability of loads. Most techniques used in wastewater treatment plants have resulted in less than 80% of the Equilenin. Similarly, using physical methods has produced less than 90% removal.
Advanced oxidation processes have become a suitable and effective method of removing Equilenin from contaminated water. The reactive hydroxyl radicals produced during the process destroys the compounds. One of the most successful methods is ozonation and Fenton’s oxidation. However, its expensive operational costs make it difficult to use. Thus the most cost-effective technique is sonolysis. In this AOP technique, ultrasound waves of high intensity are passed through the water to create cavitation. The acoustic energy is capable of degrading the compound in water either through radical or supercritical oxidation or thermal decomposition. Some reactions take place in the water with the thermal decomposition taking place in the gaseous phase. Pyrolysis of water causes the release of the hydroxyl radical that changes Equilenin’s chemical composition.
The ultrasound process uses oxidizing agents that are responsible for the reaction kinetics. Adding H2O2 enhances reactions through the formation of the hydroxyl radicals (OH*). However, if the HzO2 is in excess, then radical scavenging occurs.
Peroxide is stable in acidic conditions but then decreases with an increase in pH. In an alkaline environment, it would dissociate to form water and Oxygen. Thus during the sonolysis, the excess Oxygen formed in the alkaline conditions diffuses and reduces efficiency. Therefore Persulfate can be used to replace hydrogen peroxide. During sonification, the free sulfate radicals produced from the persulfate ions will react with water to form hydroxyl radicals and thus increasing the rate of removal. The free radicals then react with Epileinen to breakdown the compound, hence the more the radicals, the more the decomposition rate.
Andaluri and Suri carried a study on the process of Oxidative Sonication to eliminate estrogen hormone in municipal water. They studied the effects of oxidants and pH on the oxidation process. The results show that sonification was a suitable way to eliminate estrogen hormones from the water with the presence of oxidants: both hydrogen peroxide and Persulfate. The removal rate of the estrogen hormones was more than 90%, which is an indication of a successful process. Thus, the study is evidence that oxidative sonification can be used to remove the Equilenin from water as it is also an estrogen hormone. The process would be most successful if Persulfate is used as the oxidant and hence suitable for field application.
Similarly, the contaminant originates from animal farms.
Equilenin is emerging as a water contaminant, and hence there is a need to find the process that can be used to remove it from water bodies. The three main ways of removing the contaminant are through physical removal, biodegradation, and advanced oxidation process (AOP). Physical removal has only resulted in less than 80% removal, and biodegradation has resulted in less than 90% removal. AOPs offers a better solution. However, the most common techniques, such as ozonation and Fenton’s oxidation, are quite expensive. Thus the most suitable method to use to degrade Equilenin is oxidation sonification. The process has achieved more than 90% removal rate with the use of oxidants. The oxidants produced hydroxyl molecules that react with the compound and thus degrading it. Hence it can be used in field applications to achieve Equilenin-free water.