COMPOSITE MATERIAL AND METHOD FOR REMOVING POLLUTANT FROM POLUTED WATER

Abstract

A composite material, wherein the composite material contains aluminum alloys with at least one of alkaline-earth metals and transition metals, and are used for removing pollutants by dissolving to release divalent metal ions, trivalent aluminum ions and hydroxide ions, which contact with other divalent and trivalent metal cations and anions in the contaminated water, to perform an in situ self-assemble of two-dimensional Layered Double Hydroxides (LDH) precipitates; consists of 18-70 weight% of aluminum metal, 30-80% weight of a second type of metal, and 0-2 weight% of an auxiliary agent; has a particle size of 0.01-3 mm; and preferably forms a micro-nano Alloy@LDH composite material with a core-shell structure by pretreating with dilute HCl. The present invention is used for soil remediation or sewage purification, and is suitable for chemical removal and degradation of complex contaminants from an acidic to alkaline environment.

Claims

1. A composite material which is used for soil remediation or sewage purification, and is suitable for chemical removal and degradation of complex contaminants from an acidic to alkaline environment, wherein the composite material contains aluminum alloys with at least one of alkaline-earth metals and transition metals, which are used for removal of chemical pollutants by being dissolved to release divalent metal ions, trivalent aluminum ions and hydroxide ions, which contact with other divalent and trivalent metal cations and anions in the contaminated water, so as to perform an in situ self-assemble of two-dimensional Layered Double Hydroxides (LDH) precipitates; the composite material is composed of aluminum metal, a second type of metal, and an auxiliary agent; the auxiliary agent is silicon, silicon dioxide or stearate; the aluminum metal comprises 18-70 weight% of the composite material, the second type of metal comprises 30-80% weight of the composite material, and the auxiliary agent comprises 0-2 weight% of the composite material; a source of the aluminum metal is metallic aluminum, aluminum calcium alloy, aluminum magnesium alloy, aluminum iron alloy, aluminum zinc alloy, aluminum nickel alloy, aluminum manganese alloy, or aluminum silicon alloy; a source of the second type of metal is at least one of elemental calcium, elemental magnesium, elemental iron, elemental zinc, elemental nickel and elemental manganese, or an alloy composed of two or more elements of calcium, magnesium, iron, zinc, nickel, and manganese; and the composite material is with a particle size of 0.01-3 mm to remove contaminants at initial pH<7; pH=7 or pH<10.

2. The composite material of claim 1, wherein the second type metal is selected from alkaline earth metals and/or transition metals, the alkaline earth metal is selected from one or two of calcium and magnesium, and the transition metal is selected from one or more of iron, nickel, manganese, zinc.

3. The composite material of claim 1, wherein the composite material is prepared by placing the source of the aluminum metal, the source of the second type of metal and the auxiliary agent in a ball milling tank; and making the tank rotated at 3000-5000 rpm for 30-120 min after being vacuumed and filled with argon or nitrogen.

4. The composite material of claim 1, wherein the composite material is prepared by 1) putting the source of the aluminum metal and the source of the second type of metal into a sintering furnace, which is vacuumed and filled with argon or nitrogen for 2 to 4 times; 2) sintering a mixture of the source of the aluminum metal and the source of the second type of metal at a rate of 70 - 100° C./h to a sintering temperature 700 - 1500° C. and keeping sintering for 0.5 - 3 h; 3) cooling the sintering furnace to 200 - 400° C. at a rate of 100 - 140° C./h, and then cooling the sintering furnace naturally to a room temperature; 4) breaking the mixture sintered into powders with particle sizes of less than 3 mm; and 5) putting the powders and auxiliary agent into a ball milling tank, which is vacuumed and filled with argon or nitrogen; and making the same ball milled for 5-30 mins, so as to obtain the composite material.

5. The composite material of claim 1, wherein it is used to remove contaminants from the contaminated water or soil via a REDOX reaction between the contaminants and the composite material, in which metal components are dissolved to male divalent metal ions and trivalent aluminum ions released to be further in situ self-assembled, so as to form two-dimensional, layered hydroxides, which further remove those contaminants that are difficult or not removable by the REDOX reaction and degraded products and byproducts of primary contaminants through adsorption, co-precipitation, surface complexation, isomorphic substitution, intercalation and chemical catalytic degradation.

6. The composite material of claim 1, wherein the contaminants include, but not limited to, heavy metals, chlorinated organic solvents, organic dyes, pesticides, endocrine disruptors, pentavalent arsenic, and/or nitrate.

7. The composite material of claim 1, wherein the contaminants include, but not limited to, carbonate ions, bicarbonate ions, sulfate ions, or chloride ions.

8. The composite material of claim 1, wherein the contaminated water include, but not limited to, groundwater, industrial sewage, mine water or pit water, tailings water, or surface water.

9. The composite material of claim 5, wherein LDH or HT precipitates at a bottom of a static water body, or at a downstream bottom of a flowing water body.

10. The composite material of claim 1, wherein a molar ratio between divalent metal ions and trivalent metal ions is controlled at 1:4.

11. The composite material of claim 1, wherein the composite material is pretreated with dilute HC1, so as to form core-shell micro-nano structures by coating LDH nanofilm on a surface of alloy (Alloy@LDH) for achieving more efficient remediation of contaminated water and/or soil.

12. The composite material of claim 1, wherein it is used for soil remediation, having benefits of detoxifying heavy metals by immobilization, degrading organic pollutants chemically, improving soil pH buffer capacity, regulating soil microbial community, raising soil Mg and hydrogen fertility, soil porosity, air permeability and water retention, and improving nitrogen fixation by converting nitrate into ammonium, which is readily adsorbed on a surface of soil colloids to enter a lattice of clay minerals, and transform into guano stones.

13. The composite material of claim 1, wherein the composite material contains aluminum alloyed with alkali-earth and/or transition metals; the composite material reacts with micropollutants in contaminated water to chemically remove/degrade the pollutants, releasing divalent metal ions, trivalent aluminum ions and hydroxide ions in situ to self-assembly two-dimensional, layered hydroxides (LDH), and forming precipitates with other contaminants of divalent and trivalent metal cations, anions and organics present in a contaminated water, so as to remove both the primary and secondary contaminants and purify the contaminated water.

14. The composite material of claim 1, wherein the composite material is in a particle size of 0.01-3 mm, and consists of 18-70 weight % of aluminum, 30-80% weight of alloying metals and 0-2 weight % of an auxiliary agent.

15. The composite material of claim 1, wherein the composite material is pretreated using dilute HCl to form a micro-nano core-shell structure of Alloy@LDH for improving remediation efficiency.

16. The composite material of claim 1, wherein the composite materials is used for cleaning wastewater from acidic to alkaline pH conditions, and/or remedying soil from acidic to alkaline pH conditions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 are a SEM image of composite material sample 1 prepared in Embodiment 1 and a SEM image of a product obtained after reaction of composite material sample 1, in which FIG. 1A is the SEM image of composite material sample 1 in accordance with an example of the invention.

[0045] FIG. 1B is the SEM image of product obtained after reaction of composite material sample 1 in accordance with an example of the invention.

[0046] FIG. 2 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 1 in accordance with an example of the invention.

[0047] FIG. 3 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 2 in accordance with an example of the invention.

[0048] FIG. 4 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 3 in accordance with an example of the invention.

[0049] FIG. 5 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 5 in accordance with an example of the invention.

[0050] FIG. 6 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 6 in accordance with an example of the invention.

[0051] FIG. 7 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 7 in accordance with an example of the invention.

[0052] FIG. 8 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 8 in accordance with an example of the invention.

[0053] FIG. 9 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 9 in accordance with an example of the invention.

[0054] FIG. 10 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 10 in accordance with an example of the invention.

[0055] FIG. 11 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 11 in accordance with an example of the invention.

[0056] FIG. 12 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 12 in accordance with an example of the invention.

[0057] FIG. 13 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 13 in accordance with an example of the invention.

[0058] FIG. 14 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 14 in accordance with an example of the invention.

[0059] FIG. 15 is the XRD pattern of the reaction products obtained after the reaction of composite material sample 15 in accordance with an example of the invention.

[0060] FIG. 16A is SEM micrographs of Al—Mg alloy and Al—Mg@LDH.

[0061] FIG. 16B is SEM-mapping of Al—Mg alloy and Al—Mg@LDH.

[0062] FIG. 16C is XRD of Al—Mg alloy and Al—Mg@LDH.

[0063] FIG. 16D is FT-IR of Al—Mg alloy and Al—Mg@LDH.

[0064] FIG. 17A shows a chemical reduction of nitrate by Al—Mg@LDH (0.5 g Al—Mg@LDH in 50 mL, the alloy is coated with LDH using pH 1 HCl at room temperature for 6 hours). Initial pH 6.04; temperature 25±0.5° C.

[0065] FIG. 17B shows a chemical reduction of nitrate by Al—Mg alloy (0.5 g Al—Mg alloy in 50 mL). Initial pH 6.04; temperature 25±0.5° C.

[0066] FIG. 18A makes an illustration of Mg—Al alloy and in situ LDH for removing micropollutants.

[0067] FIG. 18B shows SEM image of Mg—Al alloy particle prior to the pollutant removal process.

[0068] FIG. 18C shows SEM image of Mg-A1 alloy particle after the pollutant removal process.

[0069] FIG. 19 is a set of rice cultivars photos after 3 days transplanting.

[0070] FIG. 20 is a set of rice cultivars photos after 50 days transplanting (upper panel) polluted and added with LDH, (lower panel) polluted and added with composite material.

[0071] FIG. 21 is a set of rice cultivars photos after 50 days transplanting (upper panel) polluted without remediation material, (lower panel) unpolluted soil.

DETAILED DESCRIPTION

[0072] The present invention is further explained in detail with the attached drawings and examples. It should be understood that the following examples are used only to illustrate the present invention and are not intended to limit the scope of the present invention in any way.

Example 1-5

[0073] Composite material samples 1-5 are prepared by the following methods in EXAMPLE 1-5:

[0074] To obtain the composite material, the aluminum source, the second type of metal source and the auxiliary agent are placed in the ball milling tank. After vacuumed and filled with argon or nitrogen, the tank was rotated at 3000-5000 rpm for 30-120 min.

[0075] The specific preparation conditions are shown in TABLE 1.

TABLE-US-00001 Preparing Conditions of Composite Material samples 1-5 Sample Preparing Condition Product Aluminum source The second metal source Auxiliary agent Rotating speed (rpm) Mlling time (min) Mass fraction of aluminum (%) Mass fraction of the second metal (%) Mass fraction of auxiliary agent (%) Size (mm) Composite material sample 1 Elemental aluminum Elemental magnesium None 3000 30 70 30 0 0.3 Composite material sample 2 Elemental aluminum Elemental zinc Stearic acid 4000 60 18 80 2 0.1 Composite material sample 3 Elemental aluminum Magnesium nickel alloy Stearic acid 4000 60 20 79.9 0.1 0.1 Composite material sample 4 Elemental aluminum Iron zinc alloy Silicon 4000 60 20 79.9 0.1 0.1 Composite material sample 5 Elemental aluminum Calcium magnesium nickel alloy Silicon dioxide 5000 120 40 58 2 0.0 1

Example 6-15

[0076] Composite material samples 6-15 are prepared by the following methods in EXAMPLE 6-15. [0077] (1) Aluminum source and the second metal are put into the sintering furnace, which is vacuumed and filled with argon or nitrogen for 2 to 4 times; [0078] (2) Sintering is carried out at a rate of 70 - 100° C./h to 700 - 1500° C. and kept for 0.5 - 3h; [0079] (3) A sintering furnace is cooled to 200-400° C. at a rate of 100-140° C./h, then naturally cooled to room temperature; [0080] (4) The particle is broken to less than 3 mm; [0081] (5) Put the broken particles in a ball milling tank. The tank filled is vacuumed and filled with argon or nitrogen. The broken particle is ball milled for 5-30 mins to obtain the composite material.

[0082] The specific preparation conditions are shown in TABLE 2.

TABLE-US-00002 Preparing Conditions of Composite Material Samples 6-15 Sample Preparing Condition Product Aluminum source The second metal source Auxiliary agent Calcinating temperature (.sup.0C) Calcinating time (h) Mlling time (min) Mass fraction of aluminum (%) Mass fraction of the second metal (%) Mass fraction of auxiliary agent (%) Size (mm) Composite material sample 6 Aluminum magnesium alloy Elemental Calcium and Elemental iron Silicon 700 0.5 5 18 80 2 0.3 Composite material sample 7 Aluminum magnesium alloy Calcium magnesium alloy Silicon dioxide 700 0.5 10 60 39.99 0.01 0.1 Composite material sample 8 Aluminum magnesium alloy Magnesium nickel alloy Stearic acid 1000 1 15 40 59.9 0.1 0.0 1 Composite material sample 9 Aluminum magnesium alloy Iron zinc alloy None 1000 1 25 70 30 0 0.0 1 Composite material sample 10 Aluminum magnesium alloy Calcium magnesium nickel alloy Silicon dioxide 1000 2 30 21 78 1 0.0 1 Composite material sample 11 Aluminum iron alloy Elemental Calcium and Elemental magnesium Silicon 1500 2 5 18 78 2 0.1 Composite material sample 12 Aluminum iron alloy Calcium magnesium alloy Silicon dioxide 1500 3 10 40 59.99 0.01 0.1 Composite material sample 13 Aluminum iron alloy Magnesium nickel alloy Stearic acid 1500 3 15 40 58 2 0.0 1 Composite material sample 14 Aluminum iron alloy Iron zinc alloy None 1500 3 25 70 30 0 0.3 Composite material sample 15 Aluminum iron alloy Calcium magnesium nickel alloy Silicon dioxide 1500 3 30 21 78 1 0.0 1

Example 16

[0083] ZVI, Mg—Al LDH and composite material samples 1-5 obtained from EXAMPLE 1-5 with 1 g for each material, were added to the 100 mL of groundwater solution A. After mixed, the groundwater solution A is adjusted to pH 1.5 by HCl, and reacted for 9 h under 15° C. After the reaction, solid and liquid are separated. Seven group solid and seven group groundwater solution A are collected, respectively.

[0084] The groundwater solution A before the reaction was prepared from real groundwater and reagents. The contaminants in the groundwater solution A before the reaction includes Cr(VI), As(V), Cd.sup.2+, mercury, nitrate, 2,4, 6-trichlorophenol, methyl blue, bisphenol S and glyphosate. The concentration of contaminants in the groundwater solution A before and after reaction are shown in TABLE 3. [Among the contaminants, arsenic is a non-metallic element, which usually exists in the form of oxygen-containing anion (AsO.sub.4.sup.3-) in water. It has the feature of heavy metals, so it is included in the scope of heavy metals in some tables.]

TABLE-US-00003 Concentration of Contaminants in Groundwater Solution after Reaction in EXAMPLE 16 Contaminants Heavy Metals Nitrate (mg/L) 2,4,6 trichlorophenol (mg/L) Methyl blue (mg/L) Bisphenol S (mg/L) Glyphosate (mg/L) Cd.sup.2+ (mg/L) As(V) (mg/L) Cr(VI) (mg/L) Hg (mg/L) Solution A before reaction 20.05 20.33 19.87 5.03 24.93 19.88 20.11 20.36 24.55 ZVI 4.86 <0.02 0.50 <0.02 15.40 13.72 <0.04 8.78 <0.2 Mg-Al LDH 19.76 14.44 17.86 3.77 24.55 19.55 6.66 15.66 9.38 Composite material sample 1 <0.02 <0.02 <0.04 <0.02 <0.05 2.24 <0.04 3.42 <0.2 Composite material sample 2 <0.02 <0.02 <0.04 <0.02 <0.05 1.54 <0.04 1.60 <0.2 Composite material sample 3 <0.02 <0.02 <0.04 <0.02 <0.05 1.33 <0.04 1.60 <0.2 Composite material sample 4 <0.02 <0.02 <0.04 <0.02 <0.05 2.23 <0.04 2.08 <0.2 Composite material sample 5 <0.02 <0.02 <0.04 <0.02 <0.05 0.64 <0.04 0.38 <0.2

[0085] The SEM images of composite material sample 1 before the reaction and the reaction products obtained after the reaction are shown in FIG. 1A and FIG. 1B, respectively. It can be seen from FIG. 1 that the particle size of composite material sample 1 before the reaction is 0.02 - 2 mm, and the surface is flat and smooth, while the reaction products obtained after the reaction are typical platelet-like of LDH in shape.

[0086] By comparing the data in TABLE 3, the groundwater solution A including Cd.sup.2+, Cr(VI), As(V), mercury, nitrate nitrogen, 2,4,6-trichlorophenol, methyl blue, bisphenol S and glyphosate is treated with ZVI in 15° C. and initial pH 1.5. Among the contaminants, As(V), mercury, methyl blue and glyphosate are removed efficiently, but nitrate and chlorinated organic solvent (2,4,6-trichlorophenol) which is difficult to degrade are removed inefficiently, especially for nitrate. However, LDH only has effect on methyl blue and glyphosate removal in water, but it has almost no effect on organic solvents (2,4, 6-trichlorophenol), endocrine disruptors (bisphenol S), heavy metals [Cd.sup.2+, Cr(VI), As(V), mercury] or nitrate. In comparison, composite material samples 1-5 prepared by the invention have good removal effects on heavy metals [Cd.sup.2+, Cr(VI), As(V), mercury], nitrate, methyl blue, bisphenol S, glyphosate removal in groundwater, especially for heavy metals and nitrate. The removal rate of nitrate, which is difficult to remove by both ZVI and LDH, is close to 100% by composite samples 1-5 in 15° C. at initial pH 1.5 after 9 h reaction.

Example 17

[0087] Take 1 g of composite material samples 6-10 obtained from EXAMPLE 6-10 and mix them into 100 mL groundwater solution B, and adjust the pH of mixed groundwater solution B to 6 by HCl. The reaction is carried out in 30° C. for 9 h. After the reaction, solid and liquid is separated, and five groups of solid after reaction are collected. five group solid and five group groundwater solution B are collected, respectively.

[0088] The groundwater solution B before the reaction was prepared from real groundwater and reagents. The contaminants in the groundwater solution B before the reaction includes Cu.sup.2+, Cd.sup.2+, Ni.sup.2+, Zn.sup.2+, As(V), Cr(VI), mercury, nitrate nitrogen, 2,4,6-trichlorophenol, methyl blue, bisphenol S and glyphosate. The concentration of contaminants in the groundwater solution B before and after reaction are shown in TABLE 4. [Among the contaminants, arsenic is a non-metallic element, which usually exists in the form of oxygen-containing anion (AsO.sub.4.sup.3-) in water. It has the feature of heavy metals, so it is included in the scope of heavy metals in some tables.]

TABLE-US-00004 Concentration of contaminants in groundwater solution before and after reaction in EXAMPLE 17 Contaminants Heavy metals Nitrate (mg/L) 2,4,6 Trichlorophenol (mg/L) Methyl blue (mg/L) Bisphenol S (mg/L) Glyphosate (mg/L) Cu.sup.2+ (mg/L) Cd.sup.2+ (mg/L) Ni.sup.2+ (mg/L) Zn.sup.2+ (mg/L) As(V) (mg/L) Cr(VI) (mg/L) Hg (mg/L) Solution B before reaction 20.35 21. 93 19.07 23.03 21.33 17.87 4.53 25.93 18.88 19.13 21.32 25.55 Composite material sample 6 <0.04 <0. 02 <0.02 <0.02 <0.02 1.04 <0.02 18.40 8.24 <0.04 4.42 <0.2 Composite material sample 7 <0.04 <0. 02 <0.02 <0.02 <0.02 3.99 <0.02 15.23 7.54 <0.04 4.47 <0.2 Composite material sample 8 <0.04 <0. 02 <0.02 <0.02 <0.02 0.84 <0.02 10.05 2.24 <0.04 2.42 <0.2 Composite material sample 9 <0.04 <0. 02 <0.02 <0.02 <0.02 5.89 <0.02 12.77 2.54 <0.04 2.60 <0.2 Composite material sample 10 <0.04 <0. 02 <0.02 <0.02 <0.02 1.02 <0.02 8.05 1.64 <0.04 1.38 <0.2

Example 18

[0089] Take 1 g of composite material samples 11-15 obtained from EXAMPLE 11-15, and mix them into 100 mL groundwater solution C, and adjust the pH of mixed groundwater solution C to 10 by NaOH. The reaction is carried out in 45° C. for 9 h. After the reaction, solid and liquid is separated, and five groups of solid after reaction are collected, five group solid and five group groundwater solution B are collected, respectively.

[0090] The groundwater solution C before the reaction was prepared from real groundwater and reagents. The contaminants in the groundwater solution C before the reaction includes Cr(VI), As(V), mercury, nitrate, 2,4,6-trichlorophenol, methyl blue, bisphenol S and glyphosate. The concentration of contaminants in the groundwater solution B before and after reaction are shown in TABLE 4. Because heavy metal cations form precipitation under alkaline conditions, the contaminants in water before reaction do not include heavy metal cations. [Among the contaminants, arsenic is a non-metallic element, which usually exists in the form of oxygen-containing anion (AsO.sub.4.sup.3-) in water. It has the feature of heavy metals, so it is included in the scope of heavy metals (similar to lead) in some tables.]

TABLE-US-00005 Concentration of Contaminants in Groundwater Solution before and after Reaction in EXAMPLE 18 Contaminants Heavy metals Nitrate (mg/L) 2,4,6-Trichlorophenol (mg/L) Methylblue (mg/L) Bisphenol S (mg/L) Glyphosate (mg/L) As(V) (mg/L) Cr(VI) (mg/L) Solution C before reaction 10.99 9.78 25.03 10.04 10.09 11.33 10.28 Composite material sample 11 <0.02 4.03 22.05 6.84 <0.04 7.41 <0.2 Composite material sample 12 <0.02 5.91 22.53 6.94 <0.04 7.46 <0.2 Composite material sample 13 <0.02 3.02 20.85 5.24 <0.04 5.42 <0.2 Composite material sample 14 <0.02 6.87 22.97 6.98 <0.04 8.00 <0.2 Composite material sample 15 <0.02 3.05 17.05 5.64 <0.04 5.38 <0.2

[0091] As demonstrated in TABLES 3, 4 and 5, no matter elemental aluminum or aluminum calcium, aluminum magnesium, aluminum iron, aluminum, aluminum zinc, aluminum nickel, aluminum manganese, aluminum silicon alloy are the aluminum source; no matter elemental calcium, magnesium, iron, zinc, nickel, manganese, or alloy composed two or three from calcium, magnesium, iron, zinc, nickel, manganese are the second metal source; no matter composite material samples 1-5 prepared by the first method or composite material samples 6-15 prepared by the second method have a good removal effect on organic dyes (methyl blue), heavy metals [Cu.sup.2+, Cd.sup.2+, Zn.sup.2+, Ni.sup.2+, Cr(VI), As(V)], chlorinated organic solvents (2,4,6-trichlorophenol), endocrine disruptors (bisphenol S), nitrate and pesticide residues (glyphosate) in groundwater, and have a wide range of applications, especially for the nitrate which is difficult to remove by ZVI in existing technology.

[0092] Furthermore, based on the data in TABLES 3, 4 and 5, no matter under the acidic with initial pH 1.5 and low temperature of 15° C., or under the nearly neutral condition with initial pH 6 and temperature of 30° C., or under the alkaline with initial pH 10 and high temperature of 45° C., the composite material sample 1-15 prepared by the invention have the removal effect on organic dyes (methyl blue), heavy metals [Cu.sup.2+, Cd.sup.2+, Zn.sup.2+, Ni.sup.2+, Cr(VI), As(V)], chlorinated organic solvents (2,4,6-trichlorophenol), endocrine disruptors (bisphenol S), nitrate and pesticide residues (glyphosate) in groundwater. The suitable pH range is wide. The remediation process is mild, that is, the composite material slowly dissolves all kinds of ions during reaction. Compared with parts of the existing technology carried out under alkaline conditions, this material avoids the direct dumping of alkali into the actual water body, high alkali situation in local water body and harm to aquatic ecosystem. In addition, based on the data in TABLES 3, 4 and 5, with the increase of pH, removal efficiency of chlorinated organic solvents (2,4,6-trichlorophenol) and nitrate by composite materials decline slightly. Especially, nitrate can be removed by composite material samples prepared by the invention at initial pH 10, but the removal effect is not good. Thus, the invention is especially suitable for highly acidic contaminated water bodies. For highly acidic contaminated water bodies, not only a variety of contaminants are removed, but also the pH value of treated water bodies is stable at 8 - 9 without additional alkali, which meets water quality standards. However, the conventional water treatment process to remediate acidic wastewater usually requires additional alkali to neutralize the acid in the water, and the control requirement of the alkali amount is extremely demanding. The pH value can easily exceed the pH value of the water standard under inaccurate control.

[0093] The reaction products from composite materials 1-15 after pollutants removal are characterized by XRD and the results are shown in FIG. 2 - FIG. 15. The characteristic peaks of LDH indicate that LDH is generated from composite materials 1-15 after the removal process and this is in agreement with the SEM results of FIG. 1. In another words, a REDOX reaction has occurred when the composite materials are exposed to the contaminated water; the reaction releases divalent metal ions, trivalent aluminum ions and hydroxide ions, which, together with other divalent and trivalent metal cations and anions present in the contaminated water, self-assembly in situ to form the precipitates of two-dimensional layered double hydroxides (LDH), which further adsorbs and catalyzes degradation of organic contaminants in water.

[0094] On the other hand, both composites prepared by the two methods produce LDH after reacting with contaminated water, which is caused by the combination of ions dissolved from reaction of the alloy with contaminated water, and anions in the water, as mentioned previously. When the aluminum content in the material is high, the product includes aluminum hydroxide, which is due to the high concentration of trivalent aluminum ions and the low concentration of divalent metal ions in the solution are not meet the optimal conditions for LDH preparation (molar ratio of divalent metal ions to trivalent metal ions between 1:4). Some XRD (FIGS. 4, 6-8, 11-13, 15) patterns show unreacted alloy phases, such as Al.sub.12Mg.sub.17, which resulted from the short reaction time and incomplete reaction.

Further Invention

[0095] CN102583659 discloses an acid-base dual-purpose Fe—Al—C microelectrolytic filler, which is prepared by mixing iron, aluminum and graphite powders in a mass ratio (2-6):(2-6):1. Graphite powers are not one of the components used in the present invention and the mass ratio of iron powder, aluminum powder and graphite powder of CN102583659 is obviously different from those of aluminum, second type metal and the auxiliary agent in the present invention. Fe is the core metal of the components and Al is the second metal in CN102583659 while Al is the core metal and the auxiliary agent is not essential. The technical core concept of the present invention is that the metal components provide electrons for chemical degradation of pollutants and the released divalent and trivalent metal ions self-assembly in situ into Layered Double Hydroxide (LDH). LDH is a general term for Hydrotalcite (HT) and hydrotalcite-like Compounds (HTLCs) and may be transformed into a series of supramolecular materials by intercalation of many other inorganic and organic compounds.

[0096] In another example of the invention, prior to use, the composite alloy materials are pretreated by dilute HC1 to coat a thin film of LDH on the surface of the alloy particles achieving micro-nano composite with core-shell structures Alloy@LDH. The as-prepared core-shell materials present more efficient remediation.

[0097] In a further example according to the invention, composite material composed of an aluminum source and/or a second type of metal source and LDH.

[0098] In a further example according to the invention, composite material composed of an aluminum source and/or a second type of metal source, hydrotalcite and auxiliary agent.

[0099] Preferably, as the composite material with porous surface structure of the invention, there is of 20 .Math.m-2 mm of particle size and 3-50 m.sup.2/g of a specific surface area.

[0100] In examples for soil remediation of the invention, achieved beneficial technical effects include that: [0101] 1) nitrate is converted into ammonium (ammonium ion), which can be easily adsorbed on the surface of soil colloids, and can also enter a lattice of clay minerals to become fixed ammonium ions, or converted into guano stone to reduce a loss of ammonia and increase effect of nitrogen fixation; [0102] 2) increase soil magnesium fertility and beneficial microelement contents to improve soil pH buffer capacity; [0103] 3) regulate soil microbial community to promote soil biodiversity; [0104] 4) regulate soil porosity, air permeability, and water retention to promote plant growth; [0105] 5) for acid sewage, the invention improves a contaminants removal rate and efficiency with a slow release performance and durability; [0106] 6) ability to fix and remove heavy metals and other non-metallic contaminants (heavy metals, pesticides, herbicides, antibiotics, dyes, emerging organic pollutants and other complex contaminants) can be greatly improved.

[0107] The above advantages of the invention can be confirmed by the following experimental results.

[0108] The experimental equipment and measuring apparatus adopted in the invention include oscillator, batch reactor, a toxicity test leaching and measuring cylinder, a volumetric flask and an analytical balance.

[0109] The equipment for measuring concentration of contaminants before and after the experiment includes ICP-OES, ICP-MS, LC-MS, GC, HPLC, GC-MS and UV-Vis.

[0110] FIG. 2-FIG. 15 show XRD characterization of the reaction products of the composite materials invented in this application with contaminated water, indicating that all of the reaction products contain a certain amount of LDH, featured by the peaks at the diffraction angles 2θ of xx, xx and xx representing the crystal planes of (xxx), (xxx) and (xxx), respectively. For example, 11.6°, 23.4° and 34.9° representing the crystal planes of (003), (006) and (009), respectively.

[0111] The products are composites of the alloy, intermetallic compounds such as Al.sub.3Ni.sub.2, Al.sub.12Mg.sub.17, AlFe.sub.2, Al.sub.13Fe.sub.4 depending on the alloying metals with Al and the concentration of the alloying metals. The composites of intermetallic compounds and LDH catalyze the transformation of metal species (e.g., chemical reduction of heavy metal ions to zerovalent) and chemical degradation of organic pollutants.

TABLE-US-00006 The concentration in mg/L of the contaminants and final pH of the groundwater sample treated by composite material 6 in TABLE 2 at initial pH 1.5-6.5 and by ZVI at initial pH 1.5. Cd Cr (VI) Ni As Al Fe 4-Chlorophenol Bisphenol S Glyphosate pH after reaction Original groundwater 10 50 20 10 1.0 150 20 20 20 --- Initial pH 1.5 <0.01 <0.02 <0.05 <0.02 <0.1 <0.2 <0.5 <0.5 <0.5 8.3 Initial pH 3.0 <0.01 <0.02 <0.05 <0.02 <0.1 <0.2 <0.5 <0.5 <0.5 8.7 Initial pH 5.0 <0.01 <0.02 <0.05 <0.02 <0.1 <0.2 <0.5 <0.5 <0.5 8.5 Initial pH 6.5 <0.01 <0.02 <0.05 <0.02 <0.1 <0.2 <0.5 <0.5 <0.5 8.4 ZVI pH 1.5 2.3 <0.02 4.6 <0.02 <0.1 350 <0.5 <0.5 <0.5 4.2 Note: ZVI = zerovalent iron; the pH of the groundwater sample is adjusted to 1.5-6.5 and the sample is spiked with Cd, Cr(VI), Ni, As, 4-chlorophenol, bisphenol S and glyphosate in mixtures.

[0112] TABLE 6 demonstrate that the concentrations of 10-50 mg/L Cd, Cr(VI), Ni, As, 4-chlorophenol, bisphenol S and glyphosate spiked in a real groundwater are all reduced to < 0.1-0.5 mg/L by composite material 6, achieving removal efficiencies of >97.5-99.96% and the concentrations of Al and Fe are reduced to < 0.1 and < 0.2 mg/L from 1.0 and 150 mg/L, respectively; the final pH is between 8.3 and 8.7. By contrast, the ZVI treatment presents poor efficiencies for Cd (from 10 to 2.3 mg/L, i.e., 77% removal), Ni (from 20 to 4.6 mg/L, i.e., 77% removal), causes a secondary contamination by Fe (from 150 to 350 mg/L) and does not bring the pH to a required pH range of 6-9 to meet the guideline of groundwater. Clearly, the composite material invented in this application is superior to ZVI in water treatment and purification and this is attributed to the redox reactivity of the composite material and in situ generation of hybrid LDH.

TABLE-US-00007 The concentration in mg/L of the contaminants and final pH of the groundwater sample treated by composite material 8 in TABLE 2 at initial pH 7.5-11.5 and by ZVI at initial pH 7.5. Cr(VI) 4- Chlorophenol Bisphenol S Glyphosate pH after reaction Original groundwater 50 20 20 20 --- Initial pH 7.5 <0.05 <0.5 <0.5 <0.5 8.4 Initial pH 10.0 <0.05 <0.5 <0.5 <0.5 9.3 Initial pH 11.5 <0.05 <0.5 <0.5 <0.5 9.6 ZVI pH 7.5 30 18 19 16 8.5 Note: ZVI = zerovalent iron.

[0113] The demonstration experiment in TABLE 7 investigates the removal of Cr(VI), 4-chlorophenol, bisphenol S and glyphosate by composite material 8 at initial pH of 7.5-11.5 and by ZVI at pH 7.5. The results indicate that ZVI is almost not effective while the composite material invented in this application is highly efficient to remove the contaminants at alkaline pH conditions. TABLES 8, 9 and 10 present comparisons of the invented composite material with ZVI at pH 3 and reaction temperatures of 7-28° C., reaction times of 6-15 h and dosages of 0.5-20 g/L, respectively. In all cases, the invented composite materials outperform ZVI in the removal efficiency and secondary contamination. The excellent performance comes from the reactivity of the composite material and in situ LDH.

TABLE-US-00008 Concentration (mg/L) of contaminants and final pH of the groundwater sample treated by composite material 10 in TABLE 2 at the reaction temperature of 7-28° C. and pH 3.0 and by ZVI at 25° C. and pH 3.0. Cd Cr(VI) Ni As Al Fe 4- Chlorophenol Bisphenol S Glyphosate pH after reaction Original groundwater pH 3.0 10 50 20 10 1.0 15 0 20 20 20 --- Reaction temperature 7° C. < 0.01 < 0.02 < 0.05 < 0.02 < 0.1 < 0.2 <0.5 <0.5 <0.5 8.3 Reaction temperature 15° C. < 0.01 < 0.02 < 0.05 < 0.02 < 0.1 < 0.2 <0.5 <0.5 <0.5 8.7 Reaction temperature 22° C. < 0.01 < 0.02 < 0.05 < 0.02 < 0.1 < 0.2 <0.5 <0.5 <0.5 8.5 Reaction temperature 25° C. < 0.01 < 0.02 < 0.05 < 0.02 < 0.1 < 0.2 <0.5 <0.5 <0.5 8.4 Reaction temperature 28° C. < 0.01 < 0.02 < 0.05 < 0.02 < 0.1 < 0.2 <0.5 <0.5 <0.5 8.8 ZVI Reaction temperature 25° C. 3.1 < 0.02 4.3 < 0.02 <0. 1 19 0 <0.5 <0.5 <0.5 4.3 Note: ZVI = zerovalent iron

TABLE-US-00009 The concentration in mg/L of the contaminants and final pH of the groundwater sample treated by composite material 11 in TABLE 2 at pH 3.0 and in different reaction times of 6-15 h and by ZVI in 15 h. Cd Cr(VI) Ni As Al Fe 4- Chlorophenol Bisphenol S Glyphosate pH after reaction Original groundwa ter pH 3.0 10 50 20 10 1.0 15 0 20 20 20 --- Reaction time 6 h <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 8.1 Reaction time 9 h <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 8.6 Reaction time 12 h <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 8.7 Reaction time 15 h <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 8.9 ZVI Reaction time 15 h 3.9 <0.02 5.3 <0.0 2 <0. 1 21 0 <0.5 <0.5 <0.5 4.5 Note: ZVI = zerovalent iron

TABLE-US-00010 The concentration in mg/L of the contaminants and final pH of the groundwater sample treated by composite material 12 in TABLE 2 at pH 3.0 and in different dosages of 0.5 - 20 g/L and by ZVI of 20 g/L. Cd Cr(VI) Ni As Al Fe 4- Chlorophenol Bisphenol S Glyphosate pH after reaction Original groundwa ter 10 50 20 10 1.0 15 0 20 20 20 --- Loading 0.5 g/L <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 7.9 Loading 1 g/L <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 8.3 Loading 10 g/L <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 8.6 Loading 20 g/L <0.0 1 <0.02 <0.0 5 <0.0 2 <0. 1 <0. 2 <0.5 <0.5 <0.5 9.3 ZVI Loading 20 g/L 2.9 <0.02 4.4 <0.0 2 <0. 1 29 0 <0.5 <0.5 <0.5 4.2 Note: ZVI = zerovalent iron

The Inventive Concept of “Al-Mg Alloy in Situ LDH” Is Firstly Proposed in the Present Application

[0114] Groundwater remediation has been focusing on the development of nanocomposite materials by combining nZVI with AC or other carbon materials to take the advantages of chemical degradation and adsorption. For example, a Carbo-Iron®, being registered as a trademark in Germany and consisting of nZVI clusters on activated carbon colloids (ACC) has been developed. The composite material is especially designed for the in situ generation of reactive zones and contaminant source removal when applied in groundwater remediation processes. Although nZVI-AC composite materials avoid fast aggregation and agglomeration of nZVI, the reactivity of nZVI and the adsorption capacity of AC in the nZVI-AC nanocomposites are deteriorated. Furthermore, the complicated reparation procedures, high cost, limited lifespan and ecotoxicity of nanomaterials are major limitations for these types of composite materials in the field applications.

[0115] Both Mg and Al are active metals but they are not applicable in groundwater remediation mainly because Mg metal is such reactive that it reacts rapidly with water while the passivation of Al metal makes it inertness in the most cases of groundwater conditions. Mg and Al alloys have been widely and extensively applied in many fields but they have not been applied in environmental remediation yet. The present invention is to adjust the reactivities of Mg and Al by alloying (the principle is not new) to fit into water and groundwater remediation by physiochemical and redox reactions through the reactivities of Mg—Al alloys to chemically degrade the pollutants and the adsorption, ion-exchange, surface complexation, isomorphous substitution and intercalation of in situ layered double hydroxides (LDH) to remove the primary and secondary contaminants from water (this principle is NEW). Particular Al—Mg alloys are fabricated such that the alloys provide the electrons for the chemical reduction and/or the degradation of pollutants while released Mg.sup.2+, Al.sup.3+ and OH.sup.- ions react to generate in situ LDH precipitates, incorporating other divalent and trivalent metals and oxyanions pollutants and further adsorbing the micropollutants.

Pretreatment to Coat Α Thin Film of LDH on Α Surface of Alloys

[0116] A thin film/layer of LDH is coated on the surface of the alloy particles to fabricate core/shell structures of composite material Al—Mg@LDH (FIG. 16A, FIG. 16B, FIG. 16C, and FIG. 16D) by pretreating the alloy particles with dilute HC1 pH 1-2. The chemical conversion/transformation of pollutants is significantly facilitated by the LDH pre-coated alloys. For example, the rate of nitrate chemical reduction in 10 h is improved by 3 folds using Al—Mg@LDH (FIG. 17A, FIG. 17B).

Merits of the Invention

[0117] Al and Mg are amphoteric metals such that they are active in acidic and alkaline pH conditions, i.e., they readily provide electrons to pollutants in acidic and alkaline environments. In general, the formation of LDH is a slow process, which requires a timeframe of hours and days depending on the reaction conditions (temperature, metal ions concentration and ratio and aqueous pH). By contrast, iron oxides and ferric hydroxide precipitation occurs instantly on the surface of ZVI and nZVI upon the release of Fe.sup.2+ at pH above 3.5 and this is the root cause for the passivation of ZVI and nZVI. As such, the surface of Al—Mg alloys is in a continuing renewal via in situ assembly of LDH, a typical molecular formular of which is M.sub.6Al.sub.2(OH).sub.16CO.sub.3.Math.4H.sub.2O where M is divalent metal ions, which are the reaction product of the alloy with water and pollutants, and are present in the original water. LDH is highly capable of removing a wide variety of micropollutants (metals, inorganic and organics) by adsorption, ion-exchange, surface complexation, isomorphous substitution and intercalation and chemical catalytic degradation. As such, those pollutants which are not removable by the redox reaction with Al—Mg alloys and the secondary pollutants can be both removed by the in situ LDH (FIG. 18A, FIG. 18B, and FIG. 18C). Consequently, the performance of water remediation is significantly improved by a synergistic effect of Al—Mg alloy and in situ LDH in terms of the pollutant removal efficiency, capability and capacity. In summary, microscale Al—Mg alloy and Al—Mg@LDH particles outperform nanoscale ZVI (nZVI) in water remediation by [0118] 1) significantly improving the rheology, mobility and dispersity of the water-remediation material slurry; [0119] 2) enabling effective and efficient removal of complex chemical mixtures and a wide variety of pollutants from a wide range of pH environment from acidic to alkaline pH; [0120] 3) eliminating secondary contamination and being environmentally benign as LDH is a natural clay.

[0121] The super-performance of Al—Mg alloys and in situ LDH is further demonstrated by remediating soils contaminated with 2000 mg/kg Ni.sup.2+ and 200 mg/kg Bisphenol S. The rice cultivars die in the polluted soils without remediation and added with commercially available LDH at a dosage of 1000 mg/kg soil. By contrast, the rice cultivars are alive and growing well in the unpolluted soils and polluted soils with composite material at the dosage of 1000 mg/kg soil (FIG. 19, FIG. 20 and FIG. 21).