Patent Application
20200385288
The present invention relates to methods and compositions for removing metal contaminants from aqueous streams, and more specifically relates to methods and compositions for removing heavy metal contaminants from oil and gas industry waste waters.
Pollution from heavy metals has become a serious threat to public health. It has been well established that the nonessential heavy metals such as mercury, cadmium, and lead can be highly toxic even at low concentration through generation of reactive radicals. Heavy metals may be among the main contaminants found in industrial wastewater streams, such as wastewater streams from an oil and gas refinery, or oil and gas recovery operations. Many different processes and additives have been used to clean, purify, clarify and otherwise treat wastewater streams to remove such contaminants to meet environmental standards for discharge of the treated wastewater stream, reuse of the treated wastewater stream, and other purposes.
For example, natural material-based polymers, such as starch and chitosan, are well-known for their ability to clean up particulates and oily contaminants with their high-charge density from water. In addition, functionalized polymers with sulfur- and/or nitrogen-containing moiety chelating groups have been used for heavy metal removal from aqueous streams.
However, waste water streams from oil and/or gas recovery and/or refinery operations present particular challenges because of their complex composition. It would be desirable if further methods and additives were developed for treating aqueous waste waters produced during hydrocarbon recovery and oil and gas refining to remove heavy metals from these streams.
There is provided, in one non-restrictive form, a method for reducing a concentration of at least one metal in an aqueous stream contaminated therewith with at least one protein, where the protein includes chordin and/or chordin-like proteins. A chordin-like protein is a protein that contains a chordin domain of 60-80 amino acids in length and is characterized by at least ten cysteine residues. The at least one protein is present in an amount effective to ion bond with the metal. The method further includes ion bonding the protein with the at least one metal to give a metal protein complex; and removing metal protein complex from the aqueous stream.
There is provided, in a non-limiting embodiment, a treated aqueous composition that includes an aqueous stream, which may optionally be a waste water stream from an oil or gas recovery or refinery operation, comprising at least one heavy metal contaminant and at least one protein that includes chordin and/or chordin-like proteins, where a chordin-like protein is a protein that contains a chordin domain of 60-80 amino acids in length and characterized by at least ten cysteine residues, and where the protein is present in an amount effective to ion bond with the at least one heavy metal contaminant.
In order to more fully understand the drawings referred to in the detailed description, a brief description of each drawing is presented here:
It has been discovered that peptides with an abundance of cysteine (Cys) residues are known to bind heavy metals with high affinity. Sulfur-rich metal-sequestering peptides, such as glutathione (GSH), metallothioneins (MTs) and phytochelatins (PCs) are very important to biological defense strategies against heavy metal poisoning. Chordin and chordin-like are cysteine rich (CR) proteins and the CR domains are typically 60-80 amino acids in length and characterized by at least ten cysteine residues with a conserved spacing pattern. As defined herein, a “conserved spacing pattern” means that each domain has a defined amino acid sequence that forms a spacing pattern. Metals mainly bind to free SH groups in cysteine and spacing will not participate in this binding.
Shown in
It has been discovered that certain cysteine rich proteins with several cysteine repeats are useful for heavy metal decontamination (mainly mercury) of oil and gas waste water as shown in
The heavy metals will mainly bind to the —SH groups of the cysteine amino acids. Since the chordin proteins contain 60-80 amino acids in length and are characterized by at least ten cysteine residues, there are a large number of sites where the protein can ion bond with the metal. This ion bonding of the protein with the metal gives a metal protein complex. Other proteins not part of this method are relatively smaller in nature and do not have this signature sequence. The proteins and peptides are added in aqueous form. In one non-limiting embodiment, the molar ratio of —SH group metal scavenger to metal ranges from about 1:1 independently to about 10:1; alternatively from about 2:1 independently to about 8:1. As used herein with respect to a range, the term “independently” means that any threshold may be used together with any other threshold to give a suitable alternative range.
In one non-limiting embodiment of the method, there is an absence of delivering the protein metal scavenger along with live bacteria that produces it. Stated another way, the concentration of live bacteria that produces the at least one protein is below detection levels. It is important not to use live bacteria because the microbial population may grow unhindered, which growth would need treatment with biocides. Disadvantages of using live bacteria also include having to immobilize them and making them reusable. In another non-restrictive version, the protein metal scavengers can be recombinant proteins, synthetic proteins, and combinations thereof.
In another non-limiting embodiment, the method is not limited to any particular treatment conditions, but may be practiced at a temperature range between about 20 independently to about 50° C. (about 68 to about 122° F.), alternatively between about 5 independently to about 80° C. (about 41 to about 176° F.).
After protein(s) ion bond with the metal, the resultant metal protein complex may be removed from the aqueous stream by any suitable process including, but not necessarily limited to, flocculation, filtration, and combinations thereof.
The metals removed from the aqueous stream can include any one or more of the metals generally understood in the art as heavy metals. In one non-limiting embodiment the heavy metals include, but are not necessarily limited to, mercury, cadmium, lead, zinc, copper, cobalt, nickel, platinum, silver, gold, chromium, arsenic, thallium, and combinations thereof. In a particular non-restrictive version, the heavy metal is mercury.
The method for removing metals from aqueous streams using the protein scavengers may be generally used on any aqueous stream containing the metals or heavy metals. The method is particularly suitable for treating waste water streams from oil and/or gas recovery operations, that is, waste water streams produced during recovering oil and/or gas from subterranean formations, as well as waste water streams from oil and/or gas refinery operations.
In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been described as effective in providing methods, scavenger compositions, and treated fluid compositions for decreasing and/or removing metals, particularly heavy metals, in aqueous streams containing the metals. However, it will be evident that various modifications and changes can be made thereto without departing from the broader scope of the invention as set forth in the appended claims. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific aqueous fluids, metals, proteins, treatment protocols, treatment temperatures, additional components, scavenger proportions, amount of CR domains in the proteins, and the like falling within the claimed parameters, but not specifically identified or tried in a particular composition or method, are expected to be within the scope of this invention.
The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For instance, there may be provided a method for reducing a concentration of at least one metal in an aqueous stream, where the method consists essentially of or consists of contacting an aqueous stream contaminated with a metal with at least one protein selected from the group consisting of chordin, chordin-like proteins, and combinations thereof, where a chordin-like protein is a protein that contains a chordin domain of 60-80 amino acids in length and characterized by at least ten cysteine residues, where the protein is present in an amount effective to ion bond with the at least one metal; ion bonding the protein with the at least one metal to give a metal protein complex; and removing metal protein complex from the aqueous stream.
Alternatively, there may be provided a treated aqueous composition that consists of or consists essentially of an aqueous stream (optionally a waste water stream from an oil or gas recovery or refinery operation) comprising at least one heavy metal contaminant; and at least one protein selected from the group consisting of chordin, chordin-like proteins, and combinations thereof, where a chordin-like protein is a protein that contains a chordin domain of 60-80 amino acids in length and characterized by at least ten cysteine residues, and where the protein is present in an amount effective to ion bond with the at least one heavy metal contaminant.
As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method acts, but also include the more restrictive terms “consisting of” and “consisting essentially of” and grammatical equivalents thereof. As used herein, the term “may” with respect to a material, structure, feature or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure and such term is used in preference to the more restrictive term “is” so as to avoid any implication that other, compatible materials, structures, features and methods usable in combination therewith should or must be, excluded.
As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
As used herein, relational terms, such as “first,” “second,” “top,” “bottom,” “upper,” “lower,” “over,” “under,” etc., are used for clarity and convenience in understanding the disclosure and accompanying drawings and do not connote or depend on any specific preference, orientation, or order, except where the context clearly indicates otherwise.
As used herein, the term “substantially” in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met.
As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).
