CN-122010318-A - Composition and method for removing hardness of acidic wastewater

Abstract

The invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a composition and a method for removing hardness of acidic wastewater, wherein the composition comprises 100 parts of oxalic acid, 1-10 parts of disodium hydrogen phosphate, 0.5-5 parts of sodium fluosilicate and 0.1-0.3 part of a surfactant in parts by weight, the mass ratio of the activated filter residue to the composite medicament is 0.2-0.5:1, and the activated filter residue is prepared by activating the filter residue after solid-liquid separation. The method realizes synchronous deep removal of calcium and magnesium ions through the synergistic effect of oxalic acid, disodium hydrogen phosphate and sodium fluosilicate, and simultaneously further improves the precipitation efficiency and the solid-liquid separation performance through recycling of activated filter residues, and improves the overall hardness removal rate to more than 90%.

Inventors

• PAN YUXI
• ZHANG JUNFENG
• WANG LEI
• WANG YUAN
• ZHANG GUINAN
• SHAN MINGLEI
• ZHANG FENG
• JIANG XINGWEI
• YUAN YANXIA

Assignees

• 山东恒邦冶炼股份有限公司

Dates

Publication Date

20260512

Application Date

20260415

Claims (10)

1. 1. The composition for removing the hardness of the acidic wastewater is characterized by comprising a composite medicament and activated filter residues, wherein the mass ratio of the activated filter residues to the composite medicament is 0.2-0.5:1; The composite medicament comprises, by mass, 100 parts of oxalic acid, 1-10 parts of disodium hydrogen phosphate, 0.5-5 parts of sodium fluosilicate and 0.1-0.3 part of a surfactant.
2. 2. The composition for removing hardness of acidic wastewater according to claim 1, wherein the surfactant is fatty alcohol polyoxyethylene ether.
3. 3. The composition for removing hardness from acidic wastewater according to claim 1, wherein the activated filter residue is prepared by the following method: A1, drying filter residues, putting the filter residues into a high-energy ball mill, adding potassium citrate, and performing ball milling treatment; A2, dispersing the ball-milled powder into a carboxymethylation reagent solution for carboxymethylation reaction, and filtering, washing and drying after the reaction is finished.
4. 4. The composition for removing the hardness of the acidic wastewater according to claim 3, wherein in the step A1, the adding amount of the potassium citrate is 1% -5% of the mass of the filter residue, the ball milling speed is 30-38 r/min, the ball milling time is 4-6 h, and the ball-material ratio is 5-10:1.
5. 5. The composition for removing hardness of acidic wastewater according to claim 3, wherein in the step A2, the carboxymethylation reagent solution is an ethanol solution of sodium chloroacetate, wherein the mass fraction of sodium chloroacetate is 10% -20%, the pH is adjusted to 10-11 by sodium hydroxide, the reaction temperature is 50 ℃ -70 ℃, the reaction time is 2-3 h, and the drying temperature is 50 ℃ -70 ℃.
6. 6. A composition for removing hardness from acidic wastewater according to claim 3, characterized in that the main component of the filter residue is calcium oxalate.
7. 7. A method for removing hardness of acidic wastewater, characterized in that the composition for removing hardness of acidic wastewater according to any one of claims 1 to 6 is used.
8. 8. The method for removing hardness from acidic wastewater according to claim 7, comprising the steps of: S1, adding the composition into acid wastewater to be treated, and stirring for reaction; S2, performing solid-liquid separation after the reaction is finished to obtain softened dilute acid and filter residues containing hardness precipitation; The addition amount of the composition is 1.2-1.5:1 based on the molar ratio of oxalic acid to the sum of calcium and magnesium ions in the acidic wastewater to be treated; and (2) part of the filter residue obtained in the step (S2) is used for preparing activated filter residue in the composition, and the rest is returned to the copper pyrometallurgy system for ore blending.
9. 9. The method for removing hardness of acidic wastewater according to claim 8, wherein the acidic wastewater to be treated is smelting dilute acid wastewater generated in a hydrometallurgical process and subjected to copper and arsenic removal by vulcanization, wherein the acidic wastewater to be treated has a Ca 2+ concentration of 100-500 Mg/L, a Mg 2+ concentration of 50-300 Mg/L and a pH of 0.3-1.5.
10. 10. The method for removing hardness of acidic wastewater according to claim 9, wherein in the step S1, the stirring reaction is performed in two stages, wherein the first stage stirring reaction is performed at a rotation speed of 200-300 r/min for 20-30 min, and the second stage stirring reaction is performed at a rotation speed of 30-60 r/min for 30-40 min.

Description

Composition and method for removing hardness of acidic wastewater Technical Field The invention relates to a composition and a method for removing hardness of acid wastewater, belonging to the technical field of industrial wastewater treatment. Background In industrial processes such as hydrometallurgy, metal surface treatment and mining, a large amount of strongly acidic wastewater is often generated, the pH value of the wastewater is usually lower than 2.0, and the wastewater contains high-concentration hardness ions such as calcium ions (Ca 2+) and magnesium ions (Mg 2+) and is accompanied by sulfate radicals, fluoride ions, silicate and other heavy metal ions. If the waste water is directly recycled or enters a membrane treatment system (such as reverse osmosis and electrodialysis), calcium ions and magnesium ions in the waste water are very easy to combine with sulfate radicals, fluoride ions, silicate radicals and the like to form hard scale bodies such as calcium sulfate, calcium fluoride, magnesium silicate and the like. These deposits can severely clog the piping, filter materials, and membrane modules, reduce heat transfer efficiency, and even cause system downtime for cleaning, severely affecting production continuity and economy. At present, chemical precipitation method is widely adopted in industry to remove hardness, namely, alkaline agents such as lime, sodium carbonate or sodium hydroxide are added to raise the pH value of wastewater to 10-11, so that calcium ions are precipitated in the form of calcium carbonate and magnesium ions are precipitated in the form of magnesium hydroxide. However, this method has significant drawbacks in that, first, a large amount of alkaline agent is consumed to neutralize the strongly acidic wastewater to strong alkalinity, the cost is high, and the original acidic state of the wastewater is completely destroyed. If the treated effluent is required to be reused in an acid process link, acid is required to be added again for pH adjustment, so that acid consumption and operation complexity are increased, and treatment cost is further increased. Secondly, most of calcium carbonate and magnesium hydroxide generated by the method are amorphous flocculent sludge with high water content, the sedimentation and dehydration performances are poor, and the sludge disposal cost is high. In addition, during the coprecipitation process, these flocs easily adsorb or encapsulate valuable metal ions (such as copper, nickel, cobalt, etc.) in the wastewater, resulting in resource loss. The process of raising the pH also results in the formation of hydroxide precipitates of other heavy metal ions (e.g., iron, aluminum, zinc, manganese), resulting in ineffective consumption of alkaline agents and the potential for secondary pollution problems. In recent years, in order to overcome the defects of the alkaline precipitation method, a process attempt of directly using oxalic acid to remove hardness under acidic conditions has been presented. The method can form calcium oxalate precipitate by utilizing oxalic acid and calcium ions without regulating pH value theoretically. The practice shows that the process has obvious limitations that on one hand, the generated calcium oxalate crystals have small granularity, the complete separation is difficult to realize through conventional filtration, and the residual hardness of the effluent is still higher, on the other hand, when magnesium ions exist in the wastewater under the acidic condition, oxalic acid can form a soluble magnesium oxalate complex with the wastewater, so that not only can magnesium be effectively precipitated and removed, but also the precipitation effect of oxalic acid on calcium ions can be interfered, and the overall hardness removal rate is lower, and is generally difficult to stably reach more than 50%, and the strict industrial recycling or emission standard can not be met. Aiming at the problems, the prior art tries to improve the hardness removal effect by a compound medicament mode, and realizes the synchronous removal of calcium and magnesium to a certain extent. However, the method still faces the problems of low sediment separation efficiency, difficult direct recycling of filter residues and the like in practical application. Especially, calcium oxalate crystals formed in the precipitation process are still mainly in the form of fine needles, the filtering performance is required to be further improved, and the generation of a large amount of filter residues increases the disposal cost, so that the recycling of resources is not facilitated. Therefore, in the prior art, no matter the traditional alkaline precipitation method or the emerging acidic oxalic acid precipitation method or the composite medicament method, the high-efficiency and selective removal of calcium and magnesium hardness ions can not be realized on the premise of maintaining the acidic environment of a wastewater system, and the problem of d