CN109133296B

CN109133296B - Application of N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea in nickel wastewater treatment

Info

Publication number: CN109133296B
Application number: CN201810734079.9A
Authority: CN
Inventors: 庞海霞; 熊纳纳; 史娟; 姜敏; 葛红光; 刘存芳; 田光辉
Original assignee: Shaanxi University of Technology
Current assignee: Shaanxi University of Technology
Priority date: 2018-07-06
Filing date: 2018-07-06
Publication date: 2023-08-15
Anticipated expiration: 2038-07-06
Also published as: CN109133296A

Abstract

The invention discloses an application of N, N-diethyl-N '-m-fluoro substituted benzoyl thiourea in nickel wastewater treatment, wherein the treatment effect of N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea on nickel ions in wastewater is utilized, and the content of residual nickel ions is determined by utilizing a flame atomic absorption method. The result shows that in the simulated wastewater containing 500mg/L Ni (II), in the presence of the flocculating agent polyaluminium chloride and polyacrylamide, the acyl thiourea can completely precipitate Ni (II) ions within the pH range of 7-8, and the residual nickel content is far lower than the national emission standard. The invention has the advantages that: the nickel ions can be completely precipitated under the condition of approaching to neutrality, and the treated waste liquid can be directly discharged without regulating the pH value; the generated acyl thiourea Ni (II) complex precipitate can release nickel ions and thiourea precipitate again through filtration and acidification, thus realizing enrichment of Ni (II) and recovery of precipitant rapidly, the recovery rate of precipitant reaches 72.1%, and the wastewater treatment cost is reduced.

Description

Application of N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea in nickel wastewater treatment

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to application of N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea in nickel wastewater treatment.

Background

The toxicity of heavy metal ions has the characteristics of long-term accumulation and difficult degradation and destruction, and can only be concentrated and enriched through the change of valence states and compound types. Ni (Ni) ²⁺ Is one of common heavy metal pollutants and is currentlyThe reported nickel wastewater treatment methods mainly comprise a chemical precipitation method, an ion exchange method, an oxidation method, an electrolysis method and the like. Conventional hydroxide precipitation: the pH value of the treated wastewater is high, the wastewater can be discharged only by adding acid for neutralization, and for weak amphoteric metals such as Ni, the pH value is higher, and precipitates can be redissolved, so that the pH value is controlled very strictly, and the residual concentration of nickel in the water treated by the method can be less than 1mg/L; sulfide precipitation: because the solubility of sulfide is smaller than that of hydroxide, the treatment effect is better than that of hydroxide neutralization precipitation method, and the metal recovery is convenient, but the vulcanizing agent has high price, the treatment cost is higher, sulfide precipitation particles are smaller, colloid is easy to form, the precipitation is difficult, and hydrogen sulfide gas is easy to generate in the treatment process, so that secondary pollution is caused; ion exchange method: the method can remove metal cations and anions in the wastewater, and has low concentration of residual nickel ions after wastewater treatment and good treatment effect, but the cost of the ion exchange resin is higher, and acid, alkali or salt is needed when the resin is regenerated, so that the operation cost is higher, and the regenerated liquid needs further treatment; ferrite method: the improved ferrite method has the advantages of good removal rate, short sediment settling time, good treatment effect and lower cost, but the addition amount of ferrous sulfate and sodium hydroxide is larger, the content of sodium sulfate in effluent is more, the process is complex, the energy consumption is higher, the operation cost is higher, and the method is not suitable for treating a large amount of wastewater; the electrolytic method has higher treatment efficiency and is convenient for control and management, but the equipment has serious loss, high power consumption and unsatisfactory and stable wastewater treatment effect, so the electrolytic method cannot be widely applied.

Disclosure of Invention

The invention aims to provide a novel method for treating nickel wastewater by using N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea.

The invention relates to an application of N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea in nickel wastewater treatment, which comprises the following specific treatment modes: after N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea is completely dissolved by NaOH aqueous solution, adding the solution into nickel wastewater, stirring for 20-40 min to fully react, adding flocculating agent polyaluminium chloride and polyacrylamide, and stirring for 20-40 min to fully react; and standing the reaction solution for 10-20 hours, filtering, directly discharging filtrate, re-dissociating filter residues into nickel ions and N, N-diethyl-N '-m-fluoro substituted benzoyl thiourea after the pH value of the filter residues is regulated to 1.5-2.5 by acid, recovering the dissociated nickel ions, and repeatedly using the dissociated N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea after filtering.

The structural formula of the N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea is shown as follows:

in the above treatment mode, the mass ratio of the nickel ions in the nickel wastewater to the added N, N-diethyl-N '-fluoro-substituted benzoyl thiourea is 1:7-15, preferably the mass ratio of the nickel ions in the nickel wastewater to the added N, N-diethyl-N' -m-fluoro-substituted benzoyl thiourea is 1:9-12.

In the above treatment mode, the ratio of the mass of nickel ions in the nickel wastewater to the total mass of the added polyaluminum chloride and polyacrylamide is preferably 1:1×10 ^-5 ～3×10 ^-5 Wherein the mass ratio of the polyaluminum chloride to the polyacrylamide is 1:0.5-2.

In the above treatment mode, the acid is hydrochloric acid.

The invention takes N, N-diethyl-N '-m-fluoro substituted benzoyl thiourea as a precipitator, utilizes the strong coordination of the acyl thiourea to decomplex nickel ions in the wastewater, can completely precipitate the nickel ions under neutral conditions, and can achieve enrichment of the nickel ions and recovery of the N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea after acid is added to the generated precipitate, thereby establishing a novel method for treating the nickel-containing wastewater, which has the advantages of simple operation, relatively low cost and better pollution discharge effect.

Compared with other nickel wastewater treatment methods, the method has the following advantages:

1. the nickel ion removal effect is remarkable, and the nickel ion concentration in the treated wastewater is below 0.01mg/L and is far lower than 1mg/L of the national nickel emission standard;

2. the pH value of the filtrate after removing nickel ions is between 7 and 8, and the filtrate can be directly discharged, so that the complex procedure of post-treatment is avoided;

3. after the filter residue is treated by acid, nickel ions can be released, nickel ions are convenient to recycle, and meanwhile, the dissociated N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea is difficult to dissolve in water under an acidic condition to precipitate and separate out and can be recycled, so that the wastewater treatment cost is greatly reduced.

Drawings

FIG. 1 is a standard graph of absorbance as a function of nickel ion concentration.

Detailed Description

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

Example 1

1. Drawing a standard curve

Preparing 1000 mug/mL of Ni standard solution into a series of standard solutions with concentration gradients by using deionized water, sequentially testing the different concentration standard solutions by using a TAS-990 atomic absorption spectrophotometer, recording test data, and drawing a standard curve of absorbance changing along with nickel ion concentration, wherein the results are shown in Table 1 and figure 1.

TABLE 1 Nickel ion Standard concentration

2. Nickel ion removal effect detection

After 8.8706g of N, N-diethyl-N' -m-fluoro-substituted benzoyl thiourea crystals were completely dissolved in 1mol/LNaOH aqueous solution, they were transferred to a 100mL volumetric flask for constant volume to obtain thiourea ligand solution. Taking 7 clean 250mL conical flasks, sequentially numbering 1, 2, 3, 4, 5, 6 and 7, respectively adding 100mL nickel wastewater with nickel ion concentration of 500mg/L according to the table 2, sequentially adding 3, 4, 5, 6, 7, 8 and 9mL thiourea ligand solution according to the marks by a pipette, supplementing less than 9mL thiourea ligand solution with distilled water, vibrating the conical flask for 30min to fully carry out the reaction, then respectively adding 0.5mL polyaluminum chloride aqueous solution with 1mg/L and 0.5mL polyacrylamide aqueous solution with 1mg/L, and vibrating for 30min to fully react. Subsequently, the reaction solution was allowed to stand for 10 hours, and then was sequentially filtered, and the filter residue and the filtrate were respectively stored in the corresponding numbers, and the filtrate was subjected to a nickel ion removal effect measurement, the measurement results being shown in Table 3.

TABLE 2 wastewater composition and precipitant usage

TABLE 3 residual Nickel ion content in waste liquid

As shown in the experimental measurement results of Table 3, the precipitation effect of nickel ions is good when the mass ratio of N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea to nickel ions is about 7:1-14:1, and the concentration of residual nickel ions in the filtrate is the lowest when the ratio is 10.6:1. This is mainly because N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea forms a complex with nickel ions, and when the amount of thiourea derivative added is insufficient, the result of the complex is not good; however, when thiourea derivative is added in excess, the alkaline of the solution adversely affects the stability of the complex due to the increase in the amount of NaOH, so that the nickel ion content in the residual liquid starts to increase. Therefore, in the invention, the ratio of the mass of the N, N-diethyl-N '-m-fluoro substituted benzoyl thiourea to the mass of the nickel ion is 7-15:1, preferably 9-12:1, in the complexing process of the N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea and the nickel ion.

3. Determination of recovery of N, N-diethyl-N' -m-fluoro-substituted benzoylthiourea

And 6mol/L hydrochloric acid is sequentially added into the filter residue obtained in the test 2, and when the pH value of the solution is lower than 2.5, the complex is basically completely dissociated, and dissociated nickel ions enter the solution and can be further concentrated to recover nickel. The N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea precipitant is re-precipitated and separated out because of being insoluble in water under the acidic condition, and the precipitant is filtered, dried and weighed to calculate the recovery rate of the precipitant:

recovery = (recovery of acylthiourea mass/addition of acylthiourea mass) ×100%

The results are shown in Table 4.

TABLE 4 recovery of acylthioureas

As can be seen from the recovery data of the acyl thiourea in Table 4, the recovery rate of the N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea in each group of experiments is ideal, the highest recovery rate can reach 76.6%, the lowest recovery rate also reaches 61.8%, the consumption of the precipitant is comprehensively considered, the removal effect is comprehensively considered, the acid and alkali properties of the treated waste liquid are better, and the 3, 4 and 5 groups of experiments are better, so that the recovery rate of the acyl thiourea precipitant is basically stable at about 70%, and the method can be used for well treating nickel-containing waste water, can realize good separation of nickel and the precipitant, and can greatly reduce the running cost.

4. Influence of acidity

Since N, N-diethyl-N' -fluoro-substituted benzoyl thiourea is readily soluble in alkali and has a relatively high pH, the pH of the mixed solution is relatively lowered by dilution of the solution after mixing with nickel wastewater and by changes in N-H protons on the thiourea groups during complexing with nickel, as shown in Table 3, and as can be seen from the data in Table 3: the dosage ratio of the acyl thiourea to the nickel ions is in the range of 7-14:1, the concentration of the residual nickel ions in the filtrate is far lower than the national discharge standard, the pH of the mixed solution is between 7.0 and 8.5, the peracid or the peracid is not ideal for the precipitation effect, the pH is too low, the complexation is incomplete, the pH is too high, and the stability of the complex is reduced, so that the optimal pH of the N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea precipitated nickel ions can be obtained, and the treatment solution in the range can be directly discharged without acidification.

Claims

1. A nickel wastewater treatment method is characterized in that: completely dissolving N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea in NaOH aqueous solution, adding the solution into nickel wastewater, stirring for 20-40 min, adding polyaluminium chloride and polyacrylamide, and stirring for 20-40 min; then standing the reaction solution for 10-20 hours, filtering, directly discharging filtrate, re-dissociating filter residues into nickel ions and N, N-diethyl-N '-m-fluoro substituted benzoyl thiourea after the pH value of the filter residues is regulated to 1.5-2.5 by acid, recovering the dissociated nickel ions, and precipitating and separating out the dissociated N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea after the filter residues are filtered for repeated use;

the structural formula of the N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea is as follows:

the mass ratio of nickel ions in the nickel wastewater to the added N, N-diethyl-N' -m-fluoro substituted benzoyl thiourea is 1:9-12.

2. The nickel wastewater treatment method according to claim 1, wherein: the ratio of the mass of nickel ions in the nickel wastewater to the total mass of the added polyaluminum chloride and polyacrylamide is 1:1 multiplied by 10 ^-5 ～3×10 ^-5 。

3. The nickel wastewater treatment method according to claim 1, wherein: the mass ratio of the polyaluminum chloride to the polyacrylamide is 1:0.5-2.

4. The nickel wastewater treatment method according to claim 1, wherein: the acid is hydrochloric acid.