CN-121990709-A - Method for removing oxalic acid and salt thereof in wastewater by using hydrogen peroxide

Abstract

The invention discloses a method for removing oxalic acid and salts thereof in wastewater by using hydrogen peroxide. The method comprises the steps of pretreating wastewater containing oxalic acid and salt thereof, adjusting the pH value to 3.5-4.0, adding hydrogen peroxide into the adjusted wastewater, uniformly stirring to obtain mixed wastewater, and sending the mixed wastewater into an activated carbon reaction column in a pulse water inlet mode to remove oxalic acid and salt thereof in the water. Compared with the prior art, the method has the advantages of simple process, no secondary pollution and great improvement of the efficiency and environmental friendliness of wastewater treatment.

Inventors

• ZHANG SHIXIN
• LIN JINWEI
• LIU GUOQING
• SHEN QING
• WANG QIAN
• Ma Gaoheng
• MA QIANBO

Assignees

• 浙江海拓环境技术有限公司

Dates

Publication Date

20260508

Application Date

20260112

Claims (10)

1. 1. A method for removing oxalic acid and salts thereof from wastewater by using hydrogen peroxide, which is characterized by comprising the following steps: (1) After pretreatment of wastewater containing oxalic acid and salts thereof, regulating the pH value to 3.5-4.0; (2) Adding hydrogen peroxide into the adjusted wastewater, and uniformly stirring to obtain mixed wastewater; (3) And (3) sending the mixed wastewater into an activated carbon reaction column in a pulse water inlet mode, and removing oxalic acid and salts thereof in the water.
2. 2. The method according to claim 1, wherein the pretreatment of the wastewater in step (1) comprises removal of suspended matters, and preferably, the suspended matters are removed by ultrafiltration.
3. 3. The method of claim 1, wherein the mass fraction of hydrogen peroxide in the step (2) is 30%, and the mass concentration ratio of the added amount of hydrogen peroxide to oxalic acid and salt thereof (calculated by sodium oxalate) is 1:1.9-2.1.
4. 4. The method according to any one of claim 1, wherein the activated carbon reaction column in step (3) is filled with activated carbon particles, the diameter of the activated carbon particles is 2-4 mm, and the iodine value is 800-1200 mg/g.
5. 5. The method according to claim 1, wherein the aspect ratio of the activated carbon reaction column is controlled to be (10-15): 1.
6. 6. The method of claim 1, wherein the feed water from the activated carbon reaction column is pumped into the upper end of the activated carbon reaction column by pumping and then through the activated carbon by a combination of concurrent flow and gravity flow.
7. 7. The method according to claim 1, wherein in the single pulse cycle period of the pulse type water inflow, the average residence time t 1 of the water sample in the activated carbon reaction column after water inflow is controlled to be 5-10 s.
8. 8. The method of claim 6, wherein the single pulse of the pulse type has a period of t 2 and t 2 =2·t 1 , and the number of pulse periods is n, and the range of n is 15-20.
9. 9. The method of claim 4, wherein the bed fill volume V 1 of activated carbon is calculated by the following formula: T=n·t 1 M=Q·C m 1 =M/(v·T) V 1 =m 1 /ρ Wherein T is the total residence time of the reaction column, T 1 is the residence time of the single pulse reaction column, s is the pulse cycle times, M is the mass (calculated by sodium oxalate) of oxalic acid and salt thereof in waste liquid, Q is the circulating water treatment amount, L is the concentration of sodium oxalate in water, mg/L is the mass of granular activated carbon, g is the oxidation removal rate of oxalic acid and salt thereof (calculated by sodium oxalate), mg (sodium oxalate)/g activated carbon s is the value range of 0.02-0.022, V 1 is the filling volume of an activated carbon bed, cm 3 is the true bulk density of granular activated carbon, and ρ is the g/cm 3 .
10. 10. The method according to any one of claims 1 to 9, wherein the concentration of oxalic acid and salts thereof in the wastewater is controlled to be 550mg/L or less (calculated as sodium oxalate).

Description

Method for removing oxalic acid and salt thereof in wastewater by using hydrogen peroxide Technical Field The invention relates to the technical field of industrial wastewater treatment, in particular to a method for removing oxalic acid and salts thereof from wastewater by using hydrogen peroxide. Background Oxalic acid (chemical name oxalic acid, molecular formula H 2C2O4) is a common saturated dicarboxylic acid and is widely applied to a plurality of industries such as chemical industry, pharmacy, fine chemical industry, daily chemicals, printing and dyeing, manufacturing of lithium battery anode materials and the like. Oxalic acid has strong acidity, reducibility and complexation, can form a soluble complex with metals, and is often used for extracting rare earth elements. Oxalic acid and salts thereof (e.g., sodium oxalate) are also widely found in industrial wastewater. At present, the treatment methods of oxalic acid and salt thereof in water mainly comprise an electrochemical method, a chemical oxidation method, an adsorption method, a biochemical method, a precipitation recovery method and the like. However, each of these existing methods has certain limitations. For example, precipitation and adsorption processes may produce hazardous waste, whereas electrolytic and ozone catalytic oxidation processes generally require expensive equipment investment, biochemical processes have high demands on salt content, heavy metals and pH in water quality, and furthermore, ozone catalytic oxidation processes have limited treatment effects and require the use of catalysts. In certain industrial wastewater treatments, oxalic acid residues can cause fouling of the membrane system, affecting the normal treatment process. For example, in a wastewater recycling project of an enterprise, oxalic acid residues, and oxalic acid radicals and calcium ions form supersaturated solutions after wastewater enters an RO system, so that scaling problems are caused. Traditional oxalic acid treatment methods such as oxidation and adsorption are not completely effective in removing oxalic acid, but introduce new impurities, which affect subsequent treatments. Patent document CN 118929718A discloses a method for removing oxalate from a sodium aluminate solution, comprising mixing an oxalate remover with a solvent having a set temperature to obtain a mixed solution having a set concentration, adding the mixed solution into a sodium aluminate solution to cause precipitation reaction between the oxalate remover and oxalate in the sodium aluminate solution, and then performing solid-liquid separation to obtain a refined sodium aluminate solution. The oxalate remover comprises one or more of barium hydroxide, barium chloride and calcium chloride. Then, the above method has a drawback that the oxalic acid is difficult to remove by the first oxalate remover and the impurity ions such as barium and calcium are easily introduced. Disclosure of Invention In order to overcome the defects in the prior art, the invention provides a method for removing oxalic acid and salts thereof from wastewater by using hydrogen peroxide. By the method, oxalic acid and salts thereof in industrial wastewater can be removed. The method effectively solves the obvious defects that oxalic acid and salt thereof are difficult to remove thoroughly, the investment cost of the treatment process is high, new impurity ions are introduced in the treatment process, and the like. The invention provides a method for removing oxalic acid and salt thereof in wastewater by using hydrogen peroxide, which adopts the following technical scheme steps: (1) After pretreatment of wastewater containing oxalic acid and salts thereof, regulating the pH value to 3.5-4.0; (2) Adding hydrogen peroxide into the adjusted wastewater, and uniformly stirring to obtain mixed wastewater; (3) And (3) sending the mixed wastewater into an activated carbon reaction column in a pulse water inlet mode, and removing oxalic acid and salts thereof in the water. In an alternative embodiment, the wastewater pretreatment removes suspended solids by Ultrafiltration (UF) to remove solid impurities from the wastewater with high efficiency and provide cleaner wastewater for subsequent oxidation reactions. In an alternative embodiment, the mass fraction of the hydrogen peroxide is 30%, the mass ratio of the hydrogen peroxide to the sodium oxalate is 1:1.9-2.1, preferably 1:2, and the ratio ensures the oxidation reaction efficiency of the hydrogen peroxide and avoids excessive use of the hydrogen peroxide. In an alternative embodiment, the particle size of the granular activated carbon (columnar) is 2-4 mm, preferably 4mm, and the iodine value is 800-1200 mg/g, preferably 1000mg/g, so that sufficient surface area and catalytic reaction capability can be provided, and the removal efficiency of oxalic acid and salts thereof can be improved. In an alternative embodiment, the height-to-diameter ratio (height of the acti