Process for preparation of granular material

Abstract

The present disclosure provides for a method for producing porous granular composite iron having high permeability, hydrophilicity, reactivity, and capacity for treatment of inorganic and organic contaminants. The method may include the steps of: mixing iron powder, or iron/metal mixture and adsorbent powders, with surface modifier and binder compounds to form a granular material. This granular material is used in a filter, vessel, and in situ permeable reactive barrier by passing a contaminated liquid stream through a bed of the granular product for removal of the contaminants. The porous granular iron materials have low bulk density, do not fuse together and can be regenerated for reuse.

Claims

1. A method for producing porous granular composite iron for removal of inorganic and organic contaminants from liquid streams, the method comprising the steps of: mixing raw iron powders with at least one surface modifier and binder compound to induce a formation of hydrophilic granules; drying the hydrophilic granules to form a porous aggregate, wherein the porous aggregate has a particle size in a range of about 0.15 mm to about 30 mm and a surface area larger than 0.5 m.sup.2/g; passing a contaminated liquid through a bed of the porous aggregate.

2. The method of claim 1 wherein the bed of the porous aggregate is in a filter, a vessel, or in situ permeable reactive barrier.

3. The method of claim 1 wherein the bed of the porous aggregate is in a batch reactor.

4. The method of claim 1, wherein said at least one surface modifier and binder compound are selected from the group consisting of: polyvinyl alcohol, povidone, polyvinyl pyrrolidone, and polyvinyl acetate.

5. The method of claim 1, wherein said mixing the raw iron powders with the at least one surface modifier and binder compound is carried out in mixers and/or granulators.

6. The method of claim 1, wherein said hydrophilic granules are dried in a temperature range of about 50 C. to about 200 C.

7. The method of claim 1, wherein said inorganic and organic contaminants are arsenic, selenium, lead, chromium, cadmium, copper, mercury, uranium, chlorinated and nitro organic compounds.

8. The method of claim 1, further comprising the step of: regenerating the porous aggregate with an oxidant or an acid for reuse.

9. A method for producing porous granular composite iron for removal of inorganic and organic contaminants from liquid streams, the method comprising the steps of: mixing iron powder and at least one other metal and/or adsorbent powder with at least one surface modifier and binder compound to induce a formation of hydrophilic granules; drying the hydrophilic granules to form a porous aggregate, wherein the porous aggregate has a particle size in a range of about 0.15 mm to about 30 mm and a surface area larger than 0.5 m.sup.2/g; passing a contaminated liquid through a bed of the porous aggregate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates filtration results of an arsenate solution using porous and non-porous granular Fe, initial As(V) concentration in water=10 mg/L, initial pH=7.0, empty bed contact time (EBCT)=2 hours.

(2) FIG. 2 illustrates filtration results of a selenate solution using porous granular Fe, initial Se(VI) concentration=10 mg/L, initial pH=6.8, EBCT=2 hours.

(3) FIG. 3 illustrates filtration results of a 1,3,5-trinitroperhydro-1,3,5-triazine (C.sub.3H.sub.6N.sub.6O.sub.6, RDX) solution using porous granular Fe, initial RDX concentration=35 mg/L, initial pH=5, EBCT=2 hour.

(4) FIG. 4 illustrates filtration results of a DNAN solution using porous granular Fe and regenerated Fe, initial DNAN concentration=10 mg/L, initial pH=7.3, EBCT=1 hour.

(5) FIG. 5 illustrates filtration results of wastewater using porous granular FeAC, initial NQ=508 mg/L, DNAN=72 mg/L, RDX=273 mg/L, initial pH=2.65, EBCT=3 hours.

(6) FIG. 6 illustrates filtration results of a chromate solution using porous granular FeCu, Cr(VI) concentration=10 mg/L, pH=3.5, EBCT=2.5 hours.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The preferred embodiments of the present invention will now be described with reference to the drawings. Identical elements in the various figures are identified with the same reference numerals.

(8) Reference will now be made in detail to each embodiment of the present invention. Such embodiments are provided by way of explanation of the present invention, which is not intended to be limited thereto. In fact, those of ordinary skill in the art may appreciate upon reading the present specification and viewing the present drawings that various modifications and variations can be made thereto.

(9) The present invention and its embodiments comprise of methods for using iron powder or mixture of iron and other metal and adsorbent powders and surface modifier and binder to produce porous granular iron products having high permeability, hydrophilicity, reactivity and capacity for treatment of inorganic and organic contaminants in liquid and gas. The surface modifier and binder could be selected from the group of compounds consisting of polyvinyl alcohol, povidone, polyvinyl pyrrolidone, and polyvinyl acetate etc. The granular products are used in a filter, reactor, in situ permeable reactive barrier for treatment of inorganic and organic contaminants in water, solid, and gas.

(10) In the following examples, hydrophilic and porous granular iron and composite of iron and other materials were prepared. The agglomerated materials were packed into filters for treatment of inorganic and organic compounds in water. The experimental results demonstrated that the hydrophilic and porous particles were much more effective than non-porous iron particles, and that after the media were exhausted, they could be regenerated for reuse repeatedly.

Example 1

(11) Iron (Fe) powder was mixed with a polyvinyl alcohol, the aggregated iron was dried at 110 C. The dried aggregates were sieved to obtain porous granular iron in a range of about 0.42 to about 1.19 mm. Table 1, below, shows the characteristics of the porous granular iron of the present invention and commercial non-porous iron particles. The aggregated porous iron product has much low bulk density and much large specific surface area than the commercial non-porous iron particles.

(12) TABLE-US-00001 TABLE 1 Characteristics of the porous granular Fe and commercial non-porous iron particles Surface area Particle size Bulk Density Fe products (m.sup.2/g) (mm) (g/mL) Porous granular Fe 3.7 0.42-1.19 1.0-1.2 Non-porous Fe particles <0.5 0.282-0.50 4.3

(13) The porous granular iron particles were packed in a filter. Water containing 10 mg/L of arsenate (As(V)) was pumped through the filter at an empty bed contact time of 2 hours. For comparison purpose, another filtration test was conducted using a filter packed with the non-porous iron particles under the same filtration conditions. FIG. 1 shows that As(V) was reduced from 10 mg/L in the water to less than 0.7 mg/L by the porous granular iron during 1848 hours of filtration. In contrast, the effluent As concentration from the non-porous iron filter increased rapidly to 3.9 mg/L during 384 hours of filtration.

Example 2

(14) A selenate solution containing 10 mg/L of Se(VI) was treated with a filter packed with the porous granular iron. The results in FIG. 2 indicate Se(VI) was reduced to less the 0.8 mg/L during 1704 hours of filtration.

Example 3

(15) A filter packed with the porous granular iron was used to treat water containing 35 mg/L of 1,3,5-trinitroperhydro-1,3,5-triazine (C.sub.3H.sub.6N.sub.6O.sub.6, RDX) at an empty bed contact time of 2 hours. FIG. 3 shows that RDX concentration was reduced to less than 0.05 mg/L by the filter during 210 days of filtration. The results demonstrated that the granular iron product could be used for effective treatment of the nitro organic compound for a long period of time. In addition, the iron particles did not cement together in the filter. Common iron particles would cement together in filters after several months of treatment of water due to formation of iron oxides, which would significantly reduce the reactivity and permeability of the packed iron.

Example 4

(16) The removal results of 2,4-dinitroanisole (DNAN), a nitro organic compound, by a porous granular iron filter were presented in FIG. 4. The original porous granular iron reduced DNAN concentration from 10 to less than 0.9 mg/L in the first 500 hours of filtration. The oxidant-regenerated and acid-regenerated iron filtered 700 and 350 hours of water, respectively before DNAN breakthrough occurred. The results indicated that the regenerated porous granular iron can be used for effective treatment of nitro organic compounds.

Example 5

(17) A porous granular FeAC product was used to treat a solution containing nitroimines (NQ), RDX, DNAN. The results in FIG. 5 indicate that the concentrations of the nitro organic compounds were reduced to less the 20 mg/L during 91 hours of filtration.

Example 6

(18) The porous granular FeCu product was used in a column filter for treatment of water containing 10 mg/L of Cr(VI). FIG. 6 shows that the total Cr(VI) concentration was reduced to less than 0.4 mg/L by the filter during 2270 hours of filtration treatment.

(19) Although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made only by way of illustration and that numerous changes in the details of construction and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention.