阅读说明：本技术 一种硅藻土制备硅酸铁钠用于光还原Cr(VI)的方法 (Method for preparing sodium ferric silicate from diatomite for photo-reduction of Cr (VI) ) 是由 王金淑 孙领民 吴俊书 刘竞超 杜玉成 于 2020-06-18 设计创作，主要内容包括：一种硅藻土制备硅酸铁钠用于光还原Cr(VI)的方法,属于重金属离子废水处理技术及非金属矿物利用领域；该方法包括如下步骤：(1)硅藻土预处理,(2)原料均匀混合,(3)水热反应；具体方法是将硅藻土分散于氢氧化钠水溶液中分散均匀,浴锅反应,洗净干燥；在聚四氟乙烯内衬中首先加入预处理的硅藻土和氢氧化钠水溶液不断搅拌并超声,最后,逐滴加入Fe(Cl<Sub>3</Sub>)<Sub>3</Sub>水溶液,然后水热反应。粉末合成后经蒸馏水乙醇洗净干燥即可。本发明提供了束状结构的硅酸铁钠光催化剂的制备,不仅具有结构稳定、价格低廉、可循环回收等特点,具有优异的光还原六价铬性能,对60mg/L的重铬酸根还原率可达80％,实现了良好的经济和环境价值。(A method for preparing sodium ferric silicate by diatomite for photo-reduction of Cr (VI), belonging to the fields of heavy metal ion wastewater treatment technology and nonmetallic mineral utilization; the method comprises the following steps: (1) pretreating diatomite, (2) uniformly mixing raw materials, and (3) carrying out hydrothermal reaction; the concrete method is that the diatomite is dispersed in the sodium hydroxide water solution to be evenly dispersed, reacted in a bath kettle, cleaned and dried; firstly, adding pretreated diatomite and sodium hydroxide aqueous solution into polytetrafluoroethylene lining, and continuously stirringStirring and sonicating, and finally, dropwise adding Fe (Cl) 3 ) 3 Aqueous solution, and then hydrothermal reaction. The powder is synthesized and then washed and dried by distilled water and ethanol. The invention provides the preparation of the bundle-structure sodium iron silicate photocatalyst, which has the characteristics of stable structure, low price, recycling and the like, has excellent performance of photo-reducing hexavalent chromium, has a reduction rate of 60mg/L dichromate of 80 percent, and realizes good economic and environmental values.)

1. The method for preparing the sodium ferric silicate by using the diatomite is characterized by comprising the following steps:

(1) pretreating diatomite: before the diatomite participates in the reaction, pretreatment is needed to remove a surface passivation layer and activate the reaction activity; dispersing 6g of diatomite in a sodium hydroxide aqueous solution, and performing ultrasonic treatment to uniformly disperse the diatomite; then, placing the mixed solution in a water bath kettle at 90 ℃ for heat preservation for at least 2h, finally, washing with distilled water, and placing in a drying oven for drying for later use;

(2) uniformly mixing the raw materials: firstly adding pretreated diatomite into a polytetrafluoroethylene lining, then adding a sodium hydroxide aqueous solution, continuously stirring and carrying out ultrasonic treatment for 2 minutes, and then stirring for at least 20 minutes; finally, dropwise addition of Fe (Cl)₃)₃Continuously stirring the aqueous solution for at least 20min to obtain a uniformly mixed solution;

(3) hydrothermal reaction: putting the polytetrafluoroethylene lining into a reaction kettle, heating to 160-200 ℃ along with a furnace, and preserving heat for 20-30 h; after the powder is synthesized, the powder is washed by distilled water and ethanol and is placed in a drying oven for drying, and then the sodium ferric silicate is obtained.

2. The method for preparing sodium ferric silicate by using diatomite according to claim 1, wherein 300mL of 0.15-0.3 mol/L aqueous sodium hydroxide solution is used for every 6g of diatomite in the step (1).

3. The method for preparing sodium ferric silicate by using diatomite as claimed in claim 1, wherein the step (2) comprises using 8mL of aqueous sodium hydroxide solution with concentration of 0.125-0.2 mol/L and 5mL of Fe (Cl) with concentration of 0.03mol/L for every 0.2g of the pretreated diatomite₃)₃An aqueous solution.

4. The method for preparing sodium ferric silicate by using diatomite as claimed in claim 1, wherein the temperature of the step (3) is raised to 180 ℃ and kept for 24 h.

5. Sodium iron silicate obtainable by a process according to any one of claims 1 to 4.

6. Use of sodium iron silicate prepared according to the process of any one of claims 1 to 4 as a photocatalyst for the photoreduction of cr (vi) under visible light conditions.

7. Use according to claim 6, in particular by: adding photocatalyst into Cr₂O₇ ^2-And (3) in the solution, standing the suspension liquid for 30min under a dark condition to achieve adsorption balance, then adding oxalic acid, and carrying out light catalytic reduction under a visible light condition.

Technical Field

The invention belongs to the field of heavy metal ion wastewater treatment technology and nonmetallic mineral utilization, and relates to a method for preparing sodium ferric silicate from diatomite for photoreduction of Cr (VI).

Background

Heavy metal pollution has been one of the major challenges in sewage treatment in recent years, and heavy metal ions pose a persistent threat to the food chain due to their non-biodegradability. At present, the treatment methods of heavy metal polluted wastewater are more than ten, including membrane separation, electrochemical flocculation, ion exchange, adsorption, photocatalysis technology and the like. In contrast, for chromium heavy metal sewage, a photocatalytic reduction technology is widely adopted, and the principle is to utilize the light absorption and photocatalytic performance of a photocatalyst to accelerate the electron transfer between variable valence metal ions in the reaction and promote the oxidation reduction reaction of inorganic matters and organic matters in the sewage. Chromium in the water body exists in the form of acid radical anions, and is difficult to remove by methods such as adsorption, chemical precipitation and the like. Moreover, the toxicity of chromium is very strong, and the safety threshold value in water is only 0.01mg/L, so that the toxicity degradation is very important in the treatment process of chromium-containing heavy metal sewage. The toxicity of the trivalent chromium is far lower than that of the hexavalent chromium, and the highly toxic hexavalent chromium is reduced into the trivalent chromium, so that the significance of chromium-containing wastewater treatment is realized.

Diatomite is a natural porous mineral, mainly consists of silicon dioxide, and becomes an ideal silicon source for preparing silicate materials due to the advantages of no toxicity, low cost and rich reserves. This also allows silicate photocatalysts to have good structural stability and lower cost compared to other photocatalytic materials. Sodium iron silicate, commonly referred to as neon, is a chain silicate that is an emerging photocatalyst and has little been studied for its potential use in catalyzing the oxidation-reduction of pollutants in wastewater.

In the method, kieselguhr is used as a silicon source, a surfactant is not required to be introduced, and a one-step hydrothermal method is adopted to prepare the NaFeSi with the beam-shaped structure assembled by nano sheets₂O₆And further adding NaFeSi₂O₆As a photocatalyst in the visible (420 nm) range<λ<800nm), the performance of the hexavalent chromium is explored, and factors influencing the photoreduction activity are investigated.

Disclosure of Invention

The invention aims to provide a method for preparing sodium ferric silicate from diatomite for photo-reduction of Cr (VI). the method adopts a one-step hydrothermal method to uniformly mix raw materials of diatomite and ferric chloride, and simultaneously controls the relative content of components; then under the conditions of high temperature and high pressure, the bundle-shaped sodium iron silicate photocatalytic material is obtained, and the photocatalyst prepared by the method has excellent photoreduction performance.

A method for preparing sodium ferric silicate by diatomite comprises the following steps:

(1) pretreating diatomite: before the diatomite participates in the reaction, pretreatment is needed to remove a surface passivation layer and activate the reaction activity; dispersing 6g of diatomite in a sodium hydroxide aqueous solution, and performing ultrasonic treatment to uniformly disperse the diatomite; then, placing the mixed solution in a water bath kettle at 90 ℃ for heat preservation for at least 2h, finally, washing with distilled water, and placing in a drying oven for drying for later use;

preferably, every 6g of diatomite corresponds to 300mL of 0.15-0.3 mol/L sodium hydroxide aqueous solution;

(2) uniformly mixing the raw materials: firstly adding pretreated diatomite into a polytetrafluoroethylene lining, then adding a sodium hydroxide aqueous solution, continuously stirring and carrying out ultrasonic treatment for 2 minutes, and then stirring for at least 20 minutes; finally, dropwise addition of Fe (Cl)₃)₃Continuously stirring the aqueous solution for at least 20min to obtain a uniformly mixed solution;

preferably, the amount of the pretreated diatomaceous earth is 8mL or 5mL of a 0.03mol/L Fe (Cl) aqueous solution of sodium hydroxide at a concentration of 0.125 to 0.2mol/L per 0.2g of pretreated diatomaceous earth₃)₃An aqueous solution.

(3) Hydrothermal reaction: putting the polytetrafluoroethylene lining into a reaction kettle, heating to 160-200 ℃ along with a furnace (preferably 180 ℃), and preserving heat for 20-30h (such as 24 h); after the powder is synthesized, the powder is washed by distilled water and ethanol and is placed in a drying oven for drying, and then the sodium ferric silicate is obtained.

The sodium ferric silicate obtained by the invention is used as a photocatalyst, is further used for photo-reduction of Cr (VI), and can be reduced under the condition of visible light. The specific method comprises the following steps: adding the photocatalyst of the invention into Cr₂O₇ ^2-And (3) in the solution, standing the suspension liquid for 30min under a dark condition to achieve adsorption balance, then adding oxalic acid, and carrying out light catalytic reduction under a visible light condition.

The invention takes the diatomite as a silicon source, and the provided bundle-structure sodium iron silicate photocatalyst has the characteristics of stable structure, low price, recycling and the like, and shows excellent performance of photo-reducing hexavalent chromium, the reduction rate of 60mg/L dichromate can reach 80%, and good economic and environmental values are realized.

Drawings

FIG. 1 is an XRD pattern of the photocatalyst sodium iron silicate prepared in example 1;

FIG. 2 is N of the photocatalyst sodium iron silicate prepared in example 1₂Adsorption-desorption isotherms and pore size distributions;

FIG. 3 is an SEM photograph of the photocatalyst sodium iron silicate prepared in example 1;

FIG. 4 is a graph of the reduction efficiency of the photocatalyst sodium iron silicate prepared in example 1 for different concentrations of dichromate solution;

FIG. 5 is a XPS-Fe2p plot of sodium iron silicate before and after photocatalysis in example 1;

FIG. 6 is a graph showing the band gap and VB-XPS of the photocatalyst sodium iron silicate prepared in example 1.

Detailed Description

The present invention will be described in further detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.