REMOVAL OF SELENOCYANATE FROM INDUSTRIAL WATER SYSTEMS WITH SULFIDED METAL ADSORBENTS

Abstract

The invention provides a bound sulfided metal containing metals such as nickel, cobalt, iron manganese or zinc for removing selenocyanate from aqueous streams. The binder may be alumina, silica, clay or metal oxide. The amount of sulfur in the bound sulfided metal may range from 5-75% by weight. In one embodiment, the bound sulfided metal is formed and reduced and placed in a column system that comprises one or more columns and may comprise a Lead-Lag1-Lag2-Polisher series of columns.

Claims

1. A process for removing selenocyanate from an aqueous stream, comprising contacting the aqueous stream with an adsorbent comprising a bound sulfided metal or a powdered sulfided metal to remove selenocyanate wherein the process is without heating the aqueous stream and without adjustment of pH of the aqueous stream.

2. The process of claim 1 wherein the metal in the bound sulfided metal or the powdered sulfided metal is selected from the group consisting of nickel, copper, cobalt, iron, manganese, zinc and mixtures thereof.

3. The process of claim 1 wherein the metal in the bound sulfided metal comprises between 5 and 95 wt % of the bound sulfided metal.

4. The process of claim 1 wherein said bound sulfided metal comprises from 5-75 wt % sulfur.

5. The process of claim 2 wherein said metal comprises nickel.

6. The process of claim 2 wherein said metal comprises copper.

7. The process of claim 1 wherein said bound sulfided metal or a powdered sulfided metal comprises a mixture of metal sulfides.

8. The process of claim 1 wherein said bound sulfided metal comprises a binder selected from the group consisting of alumina, silica, clay, organic binders and metal oxides.

9. The process of claim 1 wherein said contacting of said aqueous stream with said bound sulfided metal is by mixing said aqueous stream with said bound sulfided metal.

10. The process of claim 1 wherein said aqueous stream is passed through at least one column containing said bound sulfided metal.

11. The process of claim 10 wherein the at least one column comprise four columns comprising a lead column, a first lag column, a second lag column and a polishing column.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention involves a product which is a bound sulfided metal. The metal sulfides can include metals such as nickel, copper, cobalt, iron, manganese, zinc and many other metals from 5-95% as metal by weight. The binder system can be alumina, silica, clay, organic binders or other metal oxides. A sulfided form of a nickel based product has shown superior performance than many other sulfur containing products but other sulfided forms can also be used. The amount of sulfur in these products can vary from 5-75% by weight. The treatment with these for removal of selenocyanate requires no pH adjustments nor does it need any heating of the water prior to treatment. It is a single use product and should be disposed off after it is saturated or exhausted. Testing results demonstrate that the product used in the present invention has very high capacity and is stable in water. These products are made mixing the respective metal salts or oxides (from 5-95% by weight) with the binder (balance) followed by forming it by extrusion or other forming methods commonly known into desired particle size. Alternately, these products can also be formed by impregnation method where a metal salt solution is impregnated on a formed media such as alumina or clay. These formed materials are dried followed by reduction to sulfided metals by treatment with any of the sulfidation techniques and chemicals. The formed metal sulfides have a very high surface area and can have shapes including granules, beads, or other shapes.

[0015] The formed sulfided metals can be used in a column system. The column system generally comprises of one or more columns in a series configuration as Lead-Lag1-Lag2-Polisher. When the lead column is exhausted it is removed from the system and Lag-1 becomes the lead column followed by addition of a new column at the end as a polisher. These products can also be used in other water treatment unit systems where contact between contaminated water and the formed product can be achieved including batch reactor, plug flow reactor, continuous stirred treatment reactor and in any type of filtration system such as multimedia filtration system.

[0016] Preliminary studies were performed by mixing the adsorbent with simulated stripped sour water containing selenocyanate and other competing anions in an Erlenmeyer flask. The ratio of liquid: solid was maintained at 500:1. The dosage of adsorbent was 2 g/L for the initial evaluation. These flasks were kept on a shaker at constant temperature for 72 hours. After this equilibrium duration the solution was filtered through a 0.2 micron filter and analyzed for selenium concentration. Adsorbent efficiency was determined by distribution coefficient, Kd which is defined as follows: Kd=(C0-Cf) V/Cf.Math.M where V=volume of solution of contaminant used for testing; mL C0 and Cf=Initial and Final concentration of contaminant respectively; g/L M=mass of adsorbent used for testing; g. Kd=distribution coefficient; mL/g.

[0017] Products exhibiting a distribution coefficient (Kd) of greater than 4000 mL/g were evaluated further. Adsorption isotherms were developed for promising products which included metal sulfides. The equilibrium adsorption isotherm studies were conducted by mixing known dosage of adsorbent (0.5 g/L to 15 g/L) with simulated stripped sour water containing selenocyanate. After the treatment the solutions were filtered and the residual concentration of selenium was measured in the filtrate. The data clearly exhibits that nickel sulfide based products had good capacity for removal of selenocyanate from stripped sour water as compared to other products that were considered.

TABLE-US-00001 TABLE Evaluation of products for Selenocyanate removal Material Kd, mL/g Chelating resin with sulfur 4,722 SAAMS with sulfur 142 SBA resin 9,763 WBA resin 438 Iron Powder 1-3micron 461 Titania based product 130 FeOOH 22 Nickel based product 64 Sulfided Ni based product 68,431 Cu based product 35 Sulfided Cu based product 8,552 Granular Activated Carbon (GAC) 157 Sulfur containing GAC 263

Specific Embodiments

[0018] While the following is described in conjunction with specific embodiments, it will be understood that this description is intended to illustrate and not limit the scope of the preceding description and the appended claims.

[0019] A first embodiment of the invention is a process for removing selenocyanate from an aqueous stream, comprising contacting the aqueous stream with an adsorbent comprising a bound sulfided metal. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal in the bound sulfided metal is selected from the group consisting of nickel, copper, cobalt, iron, manganese, zinc and mixtures thereof. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal in the bound sulfided metal comprises between 5 and 95 wt % of the bound sulfided metal. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the bound sulfided metal comprises from 5-75 wt % sulfur. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal comprises nickel. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the metal comprises copper. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the bound sulfided metal comprises a binder selected from the group consisting of alumina, silica, clay, organic binders and metal oxides. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the contacting of the aqueous stream with the bound sulfided metal is by mixing the aqueous stream with the bound sulfided metal. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the aqueous stream is passed through at least one column containing the bound sulfided metal. An embodiment of the invention is one, any or all of prior embodiments in this paragraph up through the first embodiment in this paragraph wherein the at least one column comprise a lead column, a first lag column, a second lag column and a polishing column.

[0020] Without further elaboration, it is believed that using the preceding description that one skilled in the art can utilize the present invention to its fullest extent and easily ascertain the essential characteristics of this invention, without departing from the spirit and scope thereof, to make various changes and modifications of the invention and to adapt it to various usages and conditions. The preceding preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limiting the remainder of the disclosure in any way whatsoever, and that it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

[0021] In the foregoing, all temperatures are set forth in degrees Celsius and, all parts and percentages are by weight, unless otherwise indicated.