Patent Description:
Activated carbon and other sorbents are commonly used in the drinking water industry for the removal of a variety of contaminants including chlorinated and halogenated organic compounds, trihalomethanes, adsorbable organic halogens (AOX), volatile organic compounds (VOCs), odorous materials, colored contaminants, compounds for biological treatment systems, aromatics, pesticides, and the like. The purification is accomplished by direct contact of the contaminated water with the sorbent. During purification, the various contaminants which are present in the water are adsorbed within the porous structure of the adsorbent material, which traps and holds the contaminants for later desorption and/or disposal. Activated carbon is the most common sorbent that is employed for this purpose, because it is effective at absorbing a wide variety of contaminants.

While this process is effective at removing the most common contaminants present in drinking water sources most commercially available activated carbon sorbents contain low levels of undesirable metals such as arsenic, antimony, and aluminum in amounts of parts per million (ppm). The metals originate from the source of the activated carbon, whether from coal-based activated carbon that includes the metals, or from waste organic matter that was grown on contaminated land or exposed to contaminated air or water. When metals are present in the activated carbon, they can leach into drinking water in the form of soluble oxy-anions during the start-up of a liquid phase treatment process, at parts per billion (ppb) levels. While small, these amounts are still undesirable.

The prior art has attempted to solve the problem by subjecting the activated carbon sorbents to a separate post-activation acid washing step. While these methods can effectively reduce metals leaching, the results are inconsistent and vary with the composition of the activated carbon feedstock.

<CIT> discloses zirconium-modified materials for selective adsorption and removal of aqueous arsenic.

<CIT> discloses adsorbents for removing heavy metals and methods for producing and using the same.

<CIT> discloses a sorbent comprising spherical particles of activated carbon depositing non-crystalline compound of zirconium and a process for preparing thereof.

There is a need to prevent the contamination of drinking water by the various organic contaminants which are best removed by sorbent materials, while also avoiding ancillary contamination by the metals which are present in the sorbent materials. There is also a need for improvement in the processes and methods of treating the sorbent materials, particularly the activated carbon sorbent materials, which avoids the shortcomings of prior art post-activation acid washing processes.

The object of the present invention is to prevent the contamination of drinking water by various organic contaminants, as well as avoiding the contamination of the water by leaching of metals and other elements present in the sorbents used to treat the water. This object is solved by providing the subject matter set out in the appended claims, as described in detail hereinbelow.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components unless context dictates otherwise. The illustrative embodiments described herein are not meant to be limiting.

Before the present invention is described, it is to be understood that the scope of the present invention is limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present invention, the preferred methods, devices, and materials are now described.

It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural reference unless the context clearly dictates otherwise. Thus, for example, reference to "a filter" is a reference to "one or more filters" and equivalents thereof known to those skilled in the art, and so forth.

As used herein, the term "about" means plus or minus <NUM>% of the numerical value of the number with which it is being used. Therefore, about <NUM>% means in the range of <NUM>%-<NUM>%.

As used here, the term "may" means that the later described element can either be present or that it can be excluded. For example, describing that the sorbent may include an additive means that the additive can be included, or that the additive can be excluded.

A water purification sorbent with low leaching of arsenic and antimony ions, where said sorbent is formed by depositing oxides and/or hydroxides on or within the sorbent is described herein. The term "depositing" or "deposition" in the context of the oxides and/or hydroxides on the sorbents of the present invention means that the oxides and/or hydroxides are added to the surface and/or interior of the sorbent, by any process. Depositing or deposition processes may include but are not limited to processes where the oxides and/or hydroxides are added to the sorbent by precipitation, where dissolved metals, oxides, and hydroxides are impregnated in or on the sorbent. Herein, the oxides and/or hydroxides are those of zirconium which are known to capture leaching arsenic, antimony, or other metals ions before they are carried away with the bulk water.

The oxides and/or hydroxides of zirconium capture any leaching arsenic and antimony ions before they are carried away with the bulk water. When blended with an untreated virgin sorbent, this sorbent has been shown to capture the majority of arsenic and antimony leached from the virgin carbon as well. The present invention also provides a method for making said zirconium oxide and/or hydroxide impregnated product and blends thereof.

The sorbents described herein may be for use in water purification and other processes where leaching of metals such as arsenic and antimony can be problematic. The sorbent may be a metal oxide containing sorbent having zirconium oxide as a metal oxide associated with a surface of the sorbent. Blends of metal oxide containing sorbents with untreated sorbents and filters, filter beds, and other apparatuses including metal oxide containing sorbents are also described herein.

The sorbent is activated carbon. Specifically, the sorbent is an activated carbon porous sorbent particulate formed from bituminous coal, sub-bituminous coal, lignite coal, anthracite coal, peat, nut shells, pits, coconut, babassu nut, macadamia nut, dende nut, peach pit, cherry pit, olive pit, walnut shell, wood, bagasse, rice hulls, corn husks, wheat hulls, or combinations thereof.

The sorbent may have a mean particle diameter (MPD) of about <NUM> or less. The sorbent may have a MPD about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, about <NUM> to about <NUM>, or any individual value or range encompassed by these values. Similarly, the pore geometry of the sorbent may vary, and the sorbent may have a distribution of pores including macropores (greater than <NUM> diameter), mesopores (<NUM> to <NUM> diameter), and micropores (less than <NUM> diameter). These and other pore geometries fall under the more general terms of "pores" or "porous" or "porosity" which is described throughout this specification.

The pore distribution may affect the types of materials that can be adsorbed by the sorbent. Thus, the sorbent may have a wide pore distribution indicating that the pores of each activated carbon particle have various sizes, and these are capable of adsorbing a wide range of compounds that correspond to the various pore geometries contained within the activated carbon. The pore geometries may be selected to selectively adsorb certain compounds which are expected to be found in the water to be treated.

The sorbent and pore geometries may be selected to adsorb compounds which are deleterious and which are commonly found in drinking water. These compounds include various organic compounds that cause taste and odor and/or color problems, synthetic organic chemicals from upstream discharges or runoff, organic precursor compounds that react with disinfectants, the by-products of disinfection, and natural organic compounds that have little toxicological importance. The sorbent composition and its pore geometries should be selected not only to account for the compounds for which it is desired to remove, but also to account for other compounds which may nonetheless be adsorbed, as these tend to compete for adsorption sites with the compounds which are to be adsorbed.

The activated carbon may have a moisture content of from about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>% or any individual value or range encompassed by these ranges. The moisture content may be the result of residual moisture from an impregnation process. For example, after impregnating, the activated carbon may be dried to a particular moisture level.

The amount of metal oxide or metal hydroxide associated with a surface of the sorbent may vary. For example, the sorbent may contain about <NUM> wt. % to about <NUM> wt. % metal oxide or metal hydroxide. The sorbent may contain about <NUM> wt. % to about <NUM> wt. %, about <NUM> wt. % to about <NUM> wt. % or about <NUM> wt. % to about <NUM> wt. % metal oxide or metal hydroxide or any range or individual amount encompassed by these ranges. The metal oxide or metal hydroxide containing sorbent may have about <NUM> wt. % metal oxide associated with a surface of the sorbent. The metal oxide or metal hydroxide may be attached or adhered or otherwise deposited to the surface of the sorbent by an electrostatic interaction, Van der Waals forces, adsorption, or deposition. Further, the sorbent may be within the pores of the sorbent. Herein, at least one of a zirconium oxide or zirconium hydroxide is deposited within the pores of the activated carbon porous sorbent particulate.

As used herein, the term "contact pH" means the pH water measured after immersion of a sample in about <NUM> of the water for a period of time. The period of time can be from about <NUM> minutes to about <NUM> minutes. The period of time for measuring the contact pH may be <NUM> minutes; may be <NUM> minutes; may be <NUM> minutes. Herein, the contact pH of the composition comprising the activated carbon porous sorbent particulate and the at least one of a zirconium oxide or zirconium hydroxide that is deposited within the pores of the activated carbon porous sorbent particulate is from about <NUM> to about <NUM>, e.g., from about <NUM> to about <NUM>. For all of these, the values can be measured after <NUM>, <NUM>, or <NUM> minutes of immersion. The sorbent produced in the manner of the present invention may exhibit a ten-fold reduction in arsenic, antimony, and aluminum leaching when compared to conventional sorbents that have been neutralized after acid washing and which exhibit a contact pH of about <NUM> to about <NUM>.

The sorbents of the present invention may exhibit reduced leaching of metals and other transition elements such as arsenic, antimony, and aluminum when immersed in water. Thus, the sorbents described above may be useful for use in water purification systems, and in particular, water purification systems that are used for purification of drinking water. The treatments of the present invention are also useful because they enable the selection of a wider variety of sorbent feedstocks without the possibility of leaching metals into water that is to be treated.

Methods for preparing the activated carbons described above are also disclosed. The method may include the step of impregnating a sorbent with a metal oxide such as, for example, any acidic solution of zirconium oxide, including but not limited to zirconyl chloride, zirconium sulfate, zirconium nitrate, zirconium phosphate, or analogs or combinations thereof. For example, methods include impregnating activated carbon with zirconium oxide by contacting the activated carbon with a dilute solution of zirconyl chloride. Without wishing to be bound by theory, the zirconium oxide may precipitate from this mixture into the pores of the activated carbon because the solution is inherently acidic and the pores of the sorbent, particularly activated carbon, are inherently basic.

The impregnated sorbent which has deposited metal oxides or hydroxides may be subjected to a thermal treatment such as drying and/or calcining by heating. The thermal treatment may be performed at about ambient temperature, for example, about <NUM> to about <NUM>. The thermal treatment may be performed at about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or any range made of any two of those values. The above temperature ranges are contemplated as producing effective activity in metal oxide and metal hydroxide impregnated sorbents, particularly activated carbon with included oxides and hydroxides of zirconium.

The thermal treatment using the above temperatures and temperature ranges may be performed under air, or it may be performed under an inert atmosphere, or it may be performed under a reducing atmosphere, or it may be performed under combinations of those. The inert atmosphere may be nitrogen, or any inert gas such as argon, helium, neon, krypton, xenon, and radon. Reducing gases or atmospheres may include gases such as hydrogen, carbon monoxide, and combinations thereof. It is noted that at higher temperatures, inert gases and/or reducing atmospheres are contemplated to avoid oxidation of the underlying sorbent, particularly if that sorbent is carbon. The temperature at which inert and/or reducing atmospheres are employed is about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or any range that is formed from the combination of those with an upper bound of about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, or about <NUM>. For instance, reducing and/or inert gases may be used in temperature ranges from about <NUM> to about <NUM> or about <NUM> to about <NUM> or about <NUM> to about <NUM>.

High temperature calcination occurs above <NUM> in either an inert or reducing atmosphere. Such embodiments are not limited to a particular temperature and can be carried out at any temperature from about <NUM> to about <NUM>. Effective activity has been shown in activated carbon that has been treated at about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, about <NUM>, and about <NUM>. The activity may also be produced by treatment in ranges that are formed from any two of these endpoints, such as about <NUM> to about <NUM> or about <NUM> to about <NUM>.

The methods may include a step of activating or reactivating a sorbent material, such as a carbonaceous sorbent material, before impregnating the sorbent. Activation can be carried out by any activation means known in the art including steam and chemical activation processes, and combinations of those processes. For example, the sorbent that is formed of a carbonaceous material may be exposed to an oxidizing agent such as carbon dioxide, oxygen, or steam at temperatures above <NUM>, for example, about <NUM> to about <NUM>. The carbonaceous material may be calcined at temperatures of from about <NUM> to about <NUM>, in an inert atmosphere with gases like argon or nitrogen. The carbonaceous material may be combined with an acid, strong base, or a salt such as phosphoric acid, potassium hydroxide, sodium hydroxide, calcium chloride, and zinc chloride and then subjected to temperatures of about <NUM> to about <NUM>.

The methods may include a step of washing the activated carbon in an acid solution prior to impregnation of the sorbent. Acid washing may be carried out using any acid known in the art including, for example, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, citric acid, maleic acid, fumaric acid, mono-basic organic acid, di-basic organic acid, formic acid, and the like, and can be carried out in a solution of about <NUM>% to about <NUM>% acid. Typically, washing in acid is carried out in a vessel. The activated carbon may be washed for any amount of time. For example, washing can be carried out from about <NUM> hour to about <NUM> hours, about <NUM> hours to about <NUM> hours, about <NUM> hours to about <NUM> hours, or any individual time or time period encompassed by these ranges. The step of acid washing is performed prior to the step or steps of oxide and/or hydroxide deposition on the sorbent.

The method may include the step of neutralizing the pH of the acid washed activated carbon prior to impregnation of the sorbent. Neutralization can be carried out by contacting the acid washed activated carbon with a basic solution including a base such as, for example, sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, potassium bicarbonate, and the like and combinations thereof. Contacting can be carried out by immersing the activated carbon in the basic solution, and contacting may include spraying or flowing the solution onto or over the acid washed activated carbon. Neutralization may be carried out by water washing the acid washed activated carbon, and water washing can be carried out by immersing the activated carbon in water or spraying or flowing water over the activated carbon. The methods may exclude the step of neutralizing.

The methods may include rinsing the activated carbon in water after neutralization prior to impregnation of the sorbent. Rinsing can be carried out by any means including, for example, immersion, spraying, or flowing water over the neutralized activated carbon. Rinsing may be carried out until the rinse water has a pH of about <NUM> to about <NUM>. The pH of the rinse water can be determined by measuring the pH after the water has contacted the activated carbon and has reached an ion concentration equilibrium with the neutralized activated carbon.

After washing, the method may include the steps of drying the activated carbon. For example, the activated carbon can be removed from the vessel and dried under atmospheric conditions in air at either ambient or elevated temperature. The activated carbon can be dried by heating. Further, drying may be carried out under vacuum. The activated carbon may be dried completely to a residual moisture level of about <NUM>% to about <NUM>%. The activated carbon may be dried to a residual moisture level of about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>% or any individual value or range encompassed by these ranges. The activated carbon prepared by these methods will have a contact pH of about <NUM> to about <NUM>, or any individual value or range encompassed by these values. Contact pH can be determined by contacting the dried activated carbon with purified and de-ionized water and after an amount of time, for example, about <NUM> minutes to about <NUM> minutes, determining the pH of the water. For comparison, virgin activated carbon or activated carbon that has been acid washed and rinsed until the rinse water is about neutral (i.e., pH of about <NUM>) will typically have a contact pH of greater than about <NUM>, for example, <NUM> to about <NUM>. The activated carbons described above and prepared by the method described above have a contact pH that is significantly lower than the contact pH of virgin activated carbon or activated carbon that has been washed to a neutral rinse water pH, yet the activated carbon provides significantly reduced leaching of arsenic, antimony, or other metals that can contaminate water.

The methods may further include the step of mixing the metal oxide containing sorbent with untreated sorbent. For example, activated carbon prepared by the method described above can be combined with activate carbon that is untreated, or that has been acid washed, neutralized, and/or rinsed, but does not contain metal oxides. The resulting composition, therefore, includes a mixture of metal oxide containing activated carbon and non-metal oxide containing activated carbon. Without wishing to be bound by theory, compositions including a mixture may exhibit substantially the same reduced metal leaching as compositions including only metal oxide containing activated carbon.

The mixtures may include any ratio of metal oxide containing activated carbon to non-metal oxide containing activated carbon. For example, the ratio of metal oxide containing activated carbon to non-metal oxide containing activated carbon may be <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and the like or <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, and the like. Thus, the mixtures may be about <NUM>% metal oxide containing activated carbon to about <NUM>% metal oxide containing activated carbon or less, and the mixtures may be about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, about <NUM>% to about <NUM>%, or about <NUM>% metal oxide containing activated carbon or any percentage or range encompassed by these ranges.

Filters and methods for purifying water using the metal oxide containing activated carbons described above are also disclosed. Such embodiments are not limited to particular types of filters. For example, the filter may be water filter for consumer use, or the filter may be a commercial water filter for use at, for example, an industrial or municipal water treatment plant.

The consumer filters may have any design and may at least include a housing, including a compartment configured to hold granulated activated carbon and allow water to flow over the activated carbon. Such filters may include various additional components such as, for example, screens or other means for holding the activated carbon in the compartment or additional purification devices such as filtration membranes and the like. The housing may include various components necessary to allow the filter to be integrated into a device such as a pitcher or bottle device in which water flows from one compartment to another and passes through the filter during transfer, a device that attaches to a water line or faucet that cause water to pass through the filter before being expelled from the faucet or otherwise delivered to a water dispensing device. In particular, the filter may include an inlet port for introducing water into the filter and an outlet port for dispensing the filtered or treated water from the filter. The filter may include a removable connecting means to connect to a water source such as a sink pipe, hose, tube fittings, faucet, water fountain and the like at the inlet port.

The filter may include a filter housing having an elongated envelope composed of an inert plastic material such as polyethylene, polypropylene, polyvinylchloride, polytetrafluoroethylene, or any combination thereof disposed within the filter housing for retaining the low contact pH activated carbon or mixture of low contact pH activated carbon and neutral activated carbon. The filter housing and the envelope can be spaced from one another, and a particulate filter such as, for example, filter paper may be disposed within the space to retain dust associated with the activated carbon. Additional adsorbents, such as, carbon cloth may be disposed within the space. The filter may include a perforated plate, slotted grate, mesh grill, screen, or other means for securing the envelope within the housing while allowing free flow of fluid through the housing.

Commercial or municipal water treatment devices may include larger filter devices or tanks designed to attach to large high flow water pipes that provide beds positioned to receive water from a natural source during treatment. Such devices are well known in the art and the metal oxide containing activated carbon can be included in any such device. Beds or tanks including granular activated carbon can be positioned at various places along the flow path of the treatment plant, and granular metal oxide containing activated carbon as described above can be used by any one or all of these beds or tanks. The water may be contacted with powdered activated carbon at one or more place in the treatment path, and the powdered activated carbon may be metal oxide containing activated carbon. As discussed above, in such treatment devices, the granulated or powdered metal oxide containing activated carbon can be metal oxide containing activated carbon and can be used alone or in a mixture of metal oxide containing activated carbon and non-metal oxide containing activated carbon. The treatment devices and facilities may include various additional tanks and components, such as, for example, equalization basins, clarifiers, biological treatment basins or tanks, sand filtration devices, membrane filtration devices, and the like and combinations thereof.

Methods for purifying water using the metal oxide containing activated carbon described above are also disclosed. The step of contacting can be carried out by any means including, for example, flowing water over a bed of metal oxide containing activated carbon or mixture of metal oxide containing activated carbon and non-metal oxide containing activated carbon, introducing water onto a filter including metal oxide containing activated carbon or a mixture of metal oxide containing activated carbon and non-metal oxide containing activated carbon, introducing activated carbon having metal oxide containing activated carbon or mixture of metal oxide containing activated carbon and non-metal oxide containing into a container for holding water, and the like, and such means for contacting can be combined. The method may include additional steps. For example, methods for purifying water may include the steps of filtering the water using, for example, a screen or sand filter before, after, or both before and after contacting with metal oxide containing activated carbon or mixture of metal oxide containing activated carbon and non-metal oxide containing to remove particulates. The methods may include the step of disinfecting the water to remove biological contaminants such as bacteria or other microorganisms, and the methods may include the step of introducing a disinfectant into the water. The methods may include the step of clarifying the water, adjusting the pH of the water, and the like and combinations thereof.

The present invention is further illustrated by the following Examples without, however, being limited thereto.

The objective of this process is to impregnate activated carbon with zirconium oxide in order to reduce or eliminate metals leaching. As detailed above, when acidic zirconyl chloride solution is added to inherently basic activated carbon, it is theorized that zirconium oxide is precipitated into the pores of the activated carbon. To ensure that the precipitated activated carbon is evenly distributed throughout the pores of an entire mass of activated carbon, the solution of zirconyl chloride is applied in a dilute form, with a moisture content of about <NUM>-<NUM>%. As used herein, the term "zirconyl chloride" includes but is not limited to any of the various permutations of zirconium oxides and hydroxides which are water soluble derivatives of zirconium. Zirconyl chloride is known by those of skill in the art to have the formula [Zr<NUM>(OH)<NUM>(H<NUM>O)<NUM>]Cl<NUM>(H<NUM>O)<NUM> or is sometimes written as ZrOCl<NUM> * <NUM><NUM>O or referred to as zirconyl chloride octahydrate. Zirconyl chloride is typically produced by hydrolysis of zirconium tetrachloride and/or treating zirconium oxide with hydrochloric acid.

As shown in Table <NUM> and Table <NUM>, the process of applying zirconyl chloride in dilute form is effective at reducing metals leaching, regardless of the moisture content being from <NUM>% (dry) all the way through <NUM>%. In addition, it was also observed that freshly prepared activated carbon which was treated with high moisture zirconyl chloride solution shows no leaching of zirconium. This supports the theory that the acidic zirconyl chloride, on contact with the basic activated carbon, precipitates into a water-insoluble zirconium oxide which is held within the pores of the activated carbon. It was further observed that the drying or calcination procedure is not critical and has demonstrate to be effective when conducted at <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. Activated carbon produced by this method resulted in low levels of arsenic, antimony, and aluminum for liquid phase applications as demonstrated in both static and dynamic leach tests.

In a static leaching test, the sorbent was submerged in deionized water for a period of time ranging from <NUM> to <NUM> hours, followed by filtration to remove the sorbent and analysis of the extract water for metals by methods such as inductively-coupled plasma (ICP) or ICP-Mass Spectrometry (ICP-MS).

In a dynamic leaching test, the sorbent was loaded into a column and contacted with an extraction water containing <NUM> ± <NUM> ppm total dissolved solids, <NUM> ± <NUM> ppm free chlorine and having neutral pH. Eight to ten bed volumes of extraction water is pumped through the sorbent then held static for <NUM> ± <NUM> hours. After the required hold time, the column effluent was sampled, the procedure was repeated two more times to generate a composite water samples. The water samples were then analyzed for metals by ICP or ICP-MS.

<FIG> show metals leaching profiles for accelerated column tests simulating the first <NUM> bed volumes of operation.

The zirconium content of the sorbent following the impregnation process was determined by Proton Induced X-ray Emission (PIXE) analysis. As is appreciated by those of skill in the art, PIXE analysis does not quantify the full amount of zirconium because PIXE is a surface analysis technique and does not report zirconium that is embedded within the sorbent. Table <NUM> shows data for the tested value by PIXE and the theoretical value based on the amount of chemical added to the sorbent. The value determined by PIXE was approximately <NUM>% of the theoretical value. While not accurate relative to the theoretical value, the difference between the two levels of ZrO<NUM> impregnation is accurate when compared to the feedstock.

Blending a virgin activated carbon with a ZrO<NUM> impregnated activated carbon decreased metals leaching by an amount significantly greater than that predicted by a mathematical average. Table <NUM> shows data for a virgin activated carbon feedstock, a <NUM> wt. % ZrO<NUM> impregnated activated carbon, and a <NUM>:<NUM> blend of the two. The activated carbons were blended by riffling. The data demonstrates that precipitated zirconium oxide is not only effective on the impregnated carbon but acts on metals in the process stream that may leach from other sources. In addition to reducing metals leaching, the addition of acidic zirconyl chloride followed by drying lowers the pH of the activated carbon to near neutral. This is seen in both in the contact pH of the activated carbon and in the initial bed volumes of column testing, as shown by Table <NUM> below.

As further evidence that the neutralization of the activated carbon was due to the addition of the zirconyl chloride, it was observed that when the activated carbon is calcined, residual hydrochloric acid is driven off and the pH effect is lost. This process is illustrated by <FIG>.

The impregnation of virgin activated carbon with ZrO<NUM> as described herein was more effective at reducing leachable metals than a dry mixture of the virgin carbon and the chemical zirconium oxide. To demonstrate this, two pairs of ZrO<NUM>-containing activated carbon samples were prepared. Within each pair, one sample was an admixture of dry ZrO<NUM> powder and activated carbon, while the other sample was impregnated with zirconyl chloride to target the same ZrO<NUM> loading on a dry basis. The two pairs represent intentionally different final zirconium contents, <NUM> wt. % and <NUM> wt. % (as ZrO<NUM>). Table <NUM> shows the results of the dynamic leaching test for virgin activated carbon feedstock, as well as the two pairs of treated activated carbon feedstocks described above in Examples <NUM> and <NUM>. The data in Table <NUM> shows that the treatment with zirconia in the manner described resulted in a <NUM>-<NUM>% advantage in suppressing the base activated carbon's tendency to leach arsenic or antimony relative to activated carbon that was not treated.

Claim 1:
A composition for water purification, comprising:
an activated carbon porous sorbent particulate formed from bituminous coal, sub-bituminous coal, lignite coal, anthracite coal, peat, nut shells, pits, coconut, babassu nut, macadamia nut, dende nut, peach pit, cherry pit, olive pit, walnut shell, wood, bagasse, rice hulls, corn husks, wheat hulls, or combinations thereof, and at least one of a zirconium oxide or zirconium hydroxide that is deposited within the pores of the activated carbon porous sorbent particulate,
wherein the contact pH of the composition is from about <NUM> to about <NUM>, and wherein the contact pH is measured as described in the application.