CN103342410B - Water treatment method for removing arsenic by strengthening zero-valent iron - Google Patents

Abstract

The invention relates to a technology for removing and controlling arsenic which has very high toxicity in water, and discloses a water treatment method for removing arsenic by strengthening zero-valent iron, which can be used for groundwater repair, drinking water treatment, industrial arsenic-containing wastewater treatment, sewage deep treatment and integrated small-scale water treatment systems. The water treatment method specifically comprises the following steps of: adding persulfate and zero-valent iron into water containing arsenic, wherein the persulfate is added in a molar ratio of the persulfate to arsenic of (5:1)-(100:1), and the molar ratio of the zero-valent iron to the persulfate in the water is (1:1)-(10:1); and when the mixed solution is fully mixed, filtering or depositing to finish the removal of arsenic. The water treatment method is very simple to operate, easy to popularize and apply and safe to use, and can be used for ensuring the water quality safety.

Description

A water treatment method for strengthening zero-valent iron to remove arsenic

technical field

The present invention relates to the removal and control technology of highly toxic arsenic in water, and more specifically, relates to a method that can be used for groundwater remediation, drinking water treatment, industrial arsenic-containing wastewater treatment, sewage advanced treatment, and the strengthening of integrated small water treatment systems Water treatment method for zero-valent iron removal of arsenic.

Background technique

Arsenic and arsenic compounds are typical "three causes" substances. Long-term drinking of high-arsenic water can cause blackfoot, neuralgia, blood vessel damage and increase the incidence of heart disease. In Xinjiang, Shanxi, Inner Mongolia, Jilin, Ningxia, Qinghai and more than a dozen provinces and autonomous regions in my country, arsenic poisoning in drinking water has been found, and the pollution situation is very serious. Among them, the arsenic pollution in groundwater is particularly serious, and there are also different degrees of arsenic pollution in surface water. . In natural water bodies, arsenic mainly exists in two forms, As(III) and As(V), and the toxicity of As(III) is 60 times higher than that of As(V). my country's "Drinking Water Sanitation Standards" promulgated in 2006 stipulates that the limit concentration of arsenic is 10 μg/L, but according to the monitoring results of the Environmental Health Monitoring Institute of the Chinese Academy of Preventive Medicine, the concentration of arsenic in drinking water in my country exceeds this limit. The exposed population exceeds 15% of the investigated population. Therefore, the development of efficient and economical arsenic removal technology is an urgent problem to be solved in the field of water treatment.

The commonly used processes for removing arsenic in water can be divided into coagulation precipitation, ion exchange, reverse osmosis and adsorption. The arsenic removal method by coagulation precipitation is simple and easy to implement, and it can also remove As(III) and As(V) in water at the same time when it cooperates with an oxidant. A large amount of waste residue containing arsenic causes secondary pollution to the environment. Ion exchange is usually inefficient for arsenic removal because the concentration of other ions competing with arsenic is usually much higher than the arsenic concentration. The reverse osmosis process is effective in removing arsenic, but the process is very expensive and requires pretreatment. The adsorption method has the advantages of high treatment efficiency and small adsorption interference when treating water with low arsenic content, and the adsorbent can be regenerated and reused without causing secondary pollution to the environment. The disadvantage is that the action time is long and the treatment cost High, and the treatment effect on As(III) is not ideal.

Zero-valent iron is a good-performance and cheap arsenic-removing adsorbent, which has been widely used in groundwater remediation abroad. The adsorption capacity of zero-valent iron for As(V) is strong, but the removal effect for As(III) is average. At the same time, zero-valent iron has reducing ability, and can reduce As(V) to As(III) under anoxic conditions, which is not conducive to the removal of arsenic. Therefore, the oxidation of As(III) to As(V) is a key factor for effective arsenic removal.

Utilizing the advanced oxidation process to oxidize As(III) to As(V) is an effective way to improve the effect of zero-valent iron on arsenic removal. At the same time, the free radicals generated in the advanced oxidation process can quickly oxidize the surface of zero-valent iron into new ecological iron oxides, which have higher arsenic adsorption capacity than zero-valent iron.

In summary, it is very necessary to develop a water treatment technology that can effectively, economically and safely enhance the removal of arsenic by zero-valent iron. This technology can not only be used for groundwater remediation and drinking water treatment, but also for industrial arsenic-containing wastewater treatment, advanced sewage treatment, and integrated small water treatment systems.

Contents of the invention

In order to overcome the deficiencies in the prior art, the present invention proposes a water treatment method that strengthens the removal of arsenic by zero-valent iron. The method of the present invention can efficiently remove arsenic in water, wherein arsenic includes As(III), As(V) and organic arsenic , reaching the arsenic standard stipulated in the "Drinking Water Hygienic Standard", which is less than 10 μg/L.

In order to achieve the above object, the technical solution of the present invention is:

A water treatment method for strengthening the removal of arsenic by zero-valent iron, adding persulfate and zero-valent iron to the water containing arsenic, and the dosage of persulfate is 5:1~100:1 according to the molar ratio of persulfate to arsenic Dosing, the molar ratio of zero-valent iron to persulfate in water is 1:1~10:1, and the arsenic removal is completed after the mixture is fully mixed and filtered or precipitated.

Furthermore, the persulfate is any one or more of potassium/sodium/ammonium/calcium/magnesium/ammonium persulfate and potassium/sodium/ammonium/calcium/magnesium/ammonium monopersulfate.

In order to strengthen the removal effect of arsenic, a persulfate synergistic agent is added in arsenic-containing water, and the persulfate synergistic agent includes one or more of chloride/nitric acid/ferrous sulfate and chloride/nitric acid/ferric sulfate The dosage of the persulfate synergistic agent is 0.1:1 to 1:1 according to the molar ratio of the persulfate dosage.

The principle of the present invention is that by adding persulfate and its synergistic agents to strengthen the removal of arsenic by zero-valent iron, zero-valent iron can catalyze persulfate to produce strongly oxidative sulfate radicals (SO ₄ ^·– ), whose redox potential It is 2.5–3.1 V, higher than hydroxyl radical (OH·) (1.9–2.0 V) under neutral or alkaline conditions, and close to OH· (2.4–2.7 V) under acidic conditions. SO ₄ ^·– can efficiently and quickly oxidize As(III) in water to As(V). At the same time, the surface of zero-valent iron is oxidized by persulfate and SO ₄ ^·– to new ecological iron oxide, which can adsorb As more efficiently (V). The addition of ferric ions and ferrous ions in the synergistic agent of persulfate can promote faster decomposition of persulfate and generate more SO ₄ ^·– , thus making the degradation of As(III) faster. The invention can completely remove arsenic in water, and the efficiency of arsenic removal by adsorption of zero-valent iron is 50-100% higher than that of the existing zero-valent iron. The sulfate radical oxidizes arsenic to produce SO ₄ ^2- , which has little effect on water quality.

As(III) + SO ₄ ^·– → As(IV) + SO ₄ ^2–

As(IV) + SO ₄ ^·– → As(V) + SO ₄ ^2–

As(IV) + O ₂ + H ⁺ → As(V) + HO ₂ /O ₂ ^–

Furthermore, the zero-valent iron is: powdered zero-valent iron, zero-valent iron filter column or zero-valent iron permeable wall. Zero-valent iron can be commercially available zero-valent iron, nano-scale zero-valent iron or iron waste from processing plants, such as: filings, chips, shavings and iron powder, etc.; mixing reaction methods include tube mixer mixing, stirring paddle stirring , hydraulic stirring, etc.

Further, the arsenic-containing water is one or more of groundwater, drinking water, industrial arsenic-containing wastewater, sewage or integrated small water. The invention can not only be used in the restoration of rural and urban groundwater, the removal of arsenic in drinking water, but also in the removal of arsenic in sewage and industrial waste water. According to different water bodies, different reactor configurations and chemical ratios can be designed according to water quality requirements and design specifications to achieve the purpose of quickly removing arsenic in water.

Further, the arsenic content in the arsenic-containing water is: 0-1 g/L.

Furthermore, the dosing method of the persulfate and the synergistic agent of persulfate is solid powder dosing or solution form dosing.

Further, any pH range of the arsenic-containing water pH>2, if the pH is too small, the zero-valent iron will be dissolved, which is not suitable for processing with zero-valent iron. The present invention has a good degrading effect on the arsenic in any water body under the condition of pH>2. In practical application, the dosage of the medicament can be adjusted according to different water quality characteristics to achieve the fastest removal of arsenic.

Compared with the prior art, the beneficial effect of the present invention is that the operation of the present invention is very simple and easy to popularize and apply; it is safe to use and can be used to ensure water quality safety.

Description of drawings

FIG. 1 is a graph showing the removal effect of As(III) in Example 3 of the present invention.

Fig. 2 is a graph showing the removal effect of As(V) in Example 3 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Specific implementation mode one

This embodiment "a water treatment method for strengthening zero-valent iron to remove arsenic" is carried out according to the following method: add persulfate and zero-valent iron to the water containing arsenic, so that the molar ratio of zero-valent iron and persulfate in the water is 1:1~10:1, the molar ratio of persulfate to arsenic is 5:1~100:1, then the mixed solution is stirred and reacted at a speed of 50~300 rpm for 5-60 min, and the As is completed by filtration. remove.

The water containing arsenic in this embodiment refers to groundwater or surface water containing one or more of As(III), As(IV) and organic arsenic. Persulfates are potassium persulfate (sodium, ammonium, calcium, magnesium), potassium monopersulfate (sodium, ammonium, calcium, magnesium). Zero-valent iron can be commercially available zero-valent iron, nanometer zero-valent iron or iron waste from processing plants, such as filings, chips, shavings and iron powder.

Specific implementation mode two

The difference between this embodiment and specific embodiment one is that in addition to adding persulfate, the synergistic agent of persulfate is added at the same time, and the synergistic agent of persulfate is (chlorination, nitric acid, sulfuric acid) ferrous/iron one or several. Others are the same as the first embodiment.

In this embodiment, the molar equivalent ratio of the dosage of the persulfate synergistic agent to the dosage of the persulfate is 0.1:1˜1:1.

Specific implementation mode three

The specific embodiment one "a water treatment method for strengthening zero-valent iron to remove arsenic" is carried out according to the following method: add persulfate to the water containing arsenic, and fully mix, so that the molar ratio of persulfate to arsenic is 5 :1~100:1, and then pass the mixed solution through a filter column with zero-valent iron as the main component, and after filtration, the enhanced removal of As is completed.

The water containing arsenic in this embodiment refers to groundwater or surface water containing one or more of As(III), As(IV) and organic arsenic. Persulfates are potassium persulfate (sodium, ammonium, calcium, magnesium), potassium monopersulfate (sodium, ammonium, calcium, magnesium). Zero-valent iron can be commercially available zero-valent iron, iron waste from processing plants, such as filings, chips, shavings, and iron powder.

Figure 1 is a diagram of the removal effect of As(III) in this specific embodiment. The water used is laboratory water, and As(III) is added to the pure water to make the concentration 0.8 mg/L (10 μM), and NaHCO ₃ , HCl and NaOH to adjust the pH value to neutral, then add 100 μM sodium persulfate to mix evenly, and then filter through a zero-valent iron filter column; run another set of control experiments with similar conditions, except that no sodium persulfate is added. The left bar graph shows the removal rate of arsenic by zero-valent iron alone, and the right bar graph shows the removal rate of arsenic by persulfate-enhanced zero-valent iron.

Figure 2 is a diagram of the removal effect of As(V) in this embodiment. The water used is laboratory water, and As(V) is added to the pure water to make the concentration 0.8 mg/L (10 μM ), and NaHCO ₃ , HCl and NaOH were used to adjust the pH value to be neutral, and then mixed with or without adding 100 μM potassium persulfate sodium, and then filtered through a zero-valent iron filter column; another set of control experiments was run with similar conditions, except that no oversulfate was added. sodium sulfate. The left bar graph shows the removal rate of arsenic by zero-valent iron, and the right bar graph shows the removal rate of arsenic by persulfate-enhanced zero-valent iron.

Specific implementation mode four

The difference between this embodiment and specific embodiment three is that in addition to adding persulfate, the synergistic agent of persulfate is added simultaneously: one or more of (chlorination, nitric acid, sulfuric acid) ferrous/iron, so that The synergistic agent of persulfate, persulfate and arsenic are uniformly mixed and reacted for 2-10 minutes, and then flow through the zero-valent iron filter column. Others are the same as the specific implementation.

In this embodiment, the molar equivalent ratio of the dosage of the persulfate synergistic agent to the dosage of the persulfate is 0.1:1˜1:1.

Specific implementation mode five

This embodiment "a water treatment method for strengthening the removal of arsenic by zero-valent iron" is carried out according to the following method: inject persulfate solution upstream of the in-situ infiltration wall of groundwater with zero-valent iron as the main component, so that the persulfate solution Evenly mixed with arsenic-containing groundwater, when the arsenic-containing and persulfate-containing groundwater flows through the in-situ infiltration wall, the enhanced removal of arsenic is completed. In this embodiment, the molar ratio of persulfate to arsenic is 5:1˜100:1.

The water containing arsenic in this embodiment refers to groundwater containing one or more of As(III), As(IV) and organic arsenic. Persulfates are potassium persulfate (sodium, ammonium, calcium, magnesium), potassium monopersulfate (sodium, ammonium, calcium, magnesium). Zero-valent iron can be commercially available zero-valent iron, iron waste from processing plants, such as filings, chips, shavings, and iron powder.

Specific implementation method six

The difference between this embodiment and the fifth embodiment is that in the upstream of the zero-valent iron in-situ infiltration wall, in addition to adding persulfate, the synergistic agent of persulfate is added simultaneously: (chlorination, nitric acid, sulfuric acid) ferrous/ One or several kinds of iron, make the synergistic agent of persulfate, persulfate and arsenic in groundwater uniformly mix and react for 2~10min, and then flow through the in-situ infiltration wall. Others are the same as the third embodiment.

In this embodiment, the molar equivalent ratio of the dosage of the persulfate synergistic agent to the dosage of the persulfate is 0.1:1˜1:1.

Specific implementation mode seven

This embodiment "a water treatment method for strengthening zero-valent iron to remove arsenic" is carried out as follows: an active reaction area is established in groundwater polluted by arsenic, and zero-valent iron and persulfate are added to the active reaction area to make the water The molar ratio of zero-valent iron to persulfate is 1:1~10:1, the molar ratio of persulfate to arsenic is 5:1~100:1, and the mixing reaction is 5-60 min. After precipitation, the removal of arsenic is completed . Persulfates are potassium persulfate (sodium, ammonium, calcium, magnesium), potassium monopersulfate (sodium, ammonium, calcium, magnesium). The zero-valent iron can use nanometer zero-valent iron, commercially available zero-valent iron, or iron waste from processing plants, such as filings, chips, shavings, and iron powder.

Embodiment 8

The difference between this embodiment and embodiment seven is that in addition to adding persulfate, the synergistic agent of persulfate is added simultaneously: one or more of (chlorination, nitric acid, sulfuric acid) ferrous/iron, so that persulfate The synergistic agent of salt, persulfate, and zero-valent iron react with arsenic in groundwater for 5-60 minutes, and the removal of arsenic is completed after precipitation.

In this embodiment, the molar equivalent ratio of the dosage of the persulfate synergistic agent to the dosage of the persulfate is 0.1:1˜1:1.

The embodiments of the present invention described above are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (7)

1. A water treatment method for strengthening zero-valent iron to remove arsenic is characterized in that, adding persulfate and zero-valent iron to the water containing arsenic, the dosage of persulfate is 5 by its mol ratio with arsenic : 1~100:1 dosing, the molar ratio of zero-valent iron to persulfate in water is 1:1~10:1, and the arsenic removal is completed after the mixed solution is fully mixed and filtered or precipitated; It also includes adding persulfate synergistic agents to the arsenic-containing water, and the persulfate synergistic agents include one or more of chloride/nitric acid/ferrous sulfate and chloride/nitric acid/ferric sulfate; The dosage of sulfate synergistic agent is 0.1:1~1:1 according to the molar ratio of the dosage of sulfate to the dosage of persulfate. 2. the water treatment method of strengthening zero-valent iron to remove arsenic according to claim 1, is characterized in that, described persulfate is potassium persulfate/sodium/ammonium/calcium/magnesium and potassium monopersulfate/sodium/ammonium Any one or more of calcium/magnesium. 3. The water treatment method for strengthening zero-valent iron to remove arsenic according to claim 2, characterized in that said zero-valent iron is: powdered zero-valent iron, zero-valent iron filter column or zero-valent iron permeable wall. 4. The water treatment method for strengthening zero-valent iron to remove arsenic according to claim 3, wherein the arsenic-containing water is one or more of groundwater, drinking water, industrial arsenic-containing wastewater, sewage or integrated small water Various. 5. The water treatment method for strengthening zero-valent iron removal of arsenic according to claim 4, characterized in that the content of arsenic in the arsenic-containing water is: 0-1 g/L, excluding 0. 6. The water treatment method for strengthening zero-valent iron to remove arsenic according to claim 2, characterized in that, the addition method of the synergistic agent of persulfate and persulfate is solid powder or solution form. . 7. the water treatment method of strengthening zero-valent iron to remove arsenic according to claim 6, is characterized in that, the pH of described arsenic-containing water is any pH range greater than 2.