Ceramic electroplating wastewater treatment and metal recovery process

Abstract

The invention relates to a ceramic electroplating wastewater treatment and metal recovery process which is characterized by comprising the following steps: collecting ceramic electroplating wastewater in a classified manner; carrying out pretreatment on the ceramic electroplating wastewater, and carrying out split-flow treatment on the pretreated ceramic electroplating wastewater according to categories; merging the pretreated cyanide-containing wastewater and the pretreated chromium-containing wastewater into the general electroplating wastewater to form comprehensive wastewater, and carrying out flocculent precipitation treatment; carrying out adsorption and reverse osmosis treatment to obtain purified water reaching the standard; the metal-containing sludge is subjected to acid leaching treatment, and metal elementary substances are recycled through an electrolytic method after dissolution. Through classified collection and multi-stage pretreatment technologies, ceramic suspended solids are accurately separated, and cyanogen-containing and chromium-containing wastewater is treated in a differentiated manner; a split-flow combined reaction system is innovatively adopted, and a composite biological adsorption filler and an acid leaching-electrolysis coupling process are combined, so that the problem of synergistic removal of multi-element pollutants is solved, and targeted recovery of heavy metals is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of electroplating wastewater treatment, and in particular relates to a ceramic electroplating wastewater treatment and metal recovery process. Background Art

[0002] With the rapid development of the ceramic electroplating industry, the wastewater generated in its production process contains heavy metals (such as chromium, nickel, copper), cyanide, high-concentration ceramic suspended solids and organic additives and other complex pollutants. It has the characteristics of complex composition, high toxicity and difficulty in degradation. If it is discharged directly without effective treatment, it will cause irreversible harm to water bodies, soil and human health. According to statistics, the concentration of heavy metals in ceramic electroplating wastewater can reach hundreds of ppm, and the concentration of cyanide is as high as 50-200mg / L. The traditional treatment process mostly adopts "extensive" neutralization precipitation or chemical oxidation method, which has problems such as imprecise classification treatment, excessive dosage of reagents, and extensive control of reaction conditions. For example, when cyanide-containing wastewater and chromium-containing wastewater are mixed, hexavalent chromium is easy to form complexes with cyanide, resulting in reduced efficiency of redox reaction and difficulty in meeting the standards for residual pollutants; the conventional flocculation process has a retention rate of less than 30% for nano-ceramic particles, and heavy metal sludge is not effectively separated from different metal components, and direct landfill or incineration is easy to cause secondary pollution and waste of resources. In the existing technology, although the adsorption method can deeply remove low-concentration pollutants, the selective adsorption capacity of single materials such as activated carbon for multiple heavy metals is limited, and the regeneration cost is high; and the membrane separation technology is easily affected by the clogging of ceramic particles, and the life of the reverse osmosis membrane is greatly shortened. In addition, the metal recovery process generally relies on acid leaching electrolysis of mixed sludge after chemical precipitation, but the efficiency of traditional sulfuric acid leaching is low, and the current density of the electrolysis process is >300A / m 2 , and the recovery path is not optimized according to the characteristics of different metals, resulting in serious loss of precious metals such as nickel and copper. In view of the above technical bottlenecks, the industry urgently needs an integrated process with accurate classification, synergistic efficiency, resource utilization and pollution reduction and carbon reduction. The present invention systematically solves the problems of incomplete pollutant removal, low metal recovery rate and high operating cost through technologies such as graded pretreatment, diversion directional reaction, composite biosorption and acid leaching-electrolysis coupling, providing an innovative solution for the efficient treatment and resource recycling of ceramic electroplating wastewater.

[0003] Invention patent content

[0004] The patent of this invention provides a ceramic electroplating wastewater treatment and metal recovery process.

[0005] The innovation of the patent of this invention lies in the precise separation of ceramic suspended solids and the differentiated treatment of cyanide-containing and chromium-containing wastewater through classified collection and multi-stage pretreatment technology; the innovative use of a split-merge reaction system, combined with a composite biological adsorption filler and an acid leaching-electrolysis coupling process, overcomes the problem of synergistic removal of multiple pollutants and achieves targeted recovery of heavy metals. Among them, key technologies such as two-stage oxidation of cyanide-containing wastewater, potential-controlled reduction of chromium-containing wastewater, activated carbon-hydroxyapatite-loaded biofilm adsorption, and low-energy electrolysis of titanium-based electrodes significantly improve treatment efficiency and resource utilization.

[0006] In order to achieve the purpose of the above invention patent, the technical solution of the invention patent is: a ceramic electroplating wastewater treatment and metal recovery process, characterized in that it includes the following steps: S1: classifying and collecting ceramic electroplating wastewater, the ceramic electroplating wastewater includes general electroplating wastewater, cyanide-containing electroplating wastewater, chromium-containing electroplating wastewater and ceramic suspended matter;

[0007] S2: pre-treating the ceramic electroplating wastewater, including removing the ceramic suspended matter by grid filtration and cyclone separation in sequence;

[0008] S3: The pretreated ceramic electroplating wastewater is diverted and treated by category: S31, sodium hydroxide and calcium hydroxide are added to the general electroplating wastewater to adjust the pH to 7.5-8.0, polyaluminium chloride and polyacrylamide are added for flocculation, and solid-liquid separation is performed after precipitation to obtain a first upper clear liquid and metal-containing sludge; S32, the cyanide-containing electroplating wastewater is adjusted to a pH of 10.5-11.0, sodium hypochlorite is added twice to oxidize cyanide, and pretreated cyanide-containing wastewater is obtained after neutralization; S33, sulfuric acid and sodium sulfite are added to the chromium-containing electroplating wastewater to reduce hexavalent chromium to trivalent chromium, and the pH is adjusted to 7.5-8.5 and then precipitated to obtain pretreated chromium-containing wastewater;

[0009] S4: merging the pretreated cyanide-containing wastewater and the pretreated chromium-containing wastewater into the general electroplating wastewater to form comprehensive wastewater, and repeating step S31 to perform flocculation and sedimentation treatment;

[0010] S5: sequentially subjecting the first supernatant and the second supernatant treated in S4 to adsorption and reverse osmosis treatment to obtain qualified purified water;

[0011] S6: subjecting the metal-containing sludge to acid leaching, dissolving it, and recovering the metal element by electrolysis.

[0012] Furthermore, the centrifugal force of the cyclone separation in step S2 is 2000-4000 g, and ceramic particles with a particle size greater than 10 μm are separated.

[0013] Furthermore, in the step S31, the dosage of polyaluminium chloride is 1‰ to 5‰ of the volume of the wastewater, and the dosage of polyacrylamide is 0.1‰ of the volume of the wastewater.

[0014] Furthermore, in step S32, the mass ratio of the first addition of sodium hypochlorite is 3.5 to 4.5 times that of the cyanide ion, the mass ratio of the second addition is 10 to 15 times, and the stirring time for each time is 15 to 30 minutes.

[0015] Furthermore, in step S33, the dosage of sodium sulfite is controlled to control the redox potential to be 200-300 mV, and the reaction time is 20-40 min.

[0016] Furthermore, in the adsorption treatment in step S5, a composite filler of activated carbon and hydroxyapatite is used, and a sulfate-reducing bacteria biofilm is loaded on the surface of the filler.

[0017] Furthermore, in step S6, the acid leaching treatment uses a sulfuric acid solution with a concentration of 1 to 3 mol / L, and the current density during electrolysis is 100 to 200 A / m 2 .

[0018] Furthermore, the electrolysis method uses titanium-based coated electrodes, and the metal recovery rate after electrolysis is not less than 95%.

[0019] Beneficial effects:

[0020] 1. In view of the differences in the characteristics of cyanide-containing and chromium-containing wastewater, phased oxidation (sodium hypochlorite is added twice) and potential-controlled reduction (precise addition of sodium sulfite) are adopted to avoid interference from complex formation, ensuring that the cyanide oxidation rate is greater than 99% and the hexavalent chromium reduction rate is greater than 98%. After the diversion treatment, the flocculation is combined to reduce the excessive addition of reagents, the heavy metal enrichment of the sludge is increased by 40%, and the heavy metal concentration of the effluent is stably lower than 0.1mg / L, which is better than the national emission standard.

[0021] 2. Activated carbon and hydroxyapatite composite fillers are combined with sulfate-reducing bacteria biofilm to form a physicochemical-biological synergistic adsorption system. Hydroxyapatite fixes heavy metals through ion exchange, activated carbon adsorbs organic pollutants, and biofilm degrades residual cyanide and complexes, with the comprehensive removal rate increased to 99.5%. This design extends the life of the reverse osmosis membrane by more than 30%, reduces the risk of membrane clogging, and reduces operation and maintenance costs.

[0022] 3. Use 1-3 mol / L sulfuric acid gradient acid leaching sludge, combined with titanium-based coating electrodes (current density 100-200A / m 2 ) electrolysis, to achieve targeted precipitation of metals such as nickel and copper, with a recovery rate of ≥95%, compared with traditional acid leaching (efficiency <80%) and high-voltage electrolysis (energy consumption reduced by 50%). Sludge reduction reaches 70%, avoiding secondary landfill pollution, and metal resource recycling can reduce the cost of electroplating raw materials by more than 25%.

[0023] 4. Through the full chain design of graded pretreatment-diversion reaction-deep adsorption-electrolytic recovery, the reagent consumption is reduced by 30%, the water resource reuse rate exceeds 90%, and the carbon emission intensity is reduced by 40%. The system adapts to the fluctuating water quality of ceramic electroplating wastewater, and the cost of treating a ton of water is reduced by 20% compared with traditional processes, which has both environmental benefits and industrial promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0026] Example: Ceramic electroplating plant with a daily processing capacity of 200m 3 Wastewater (including general electroplating wastewater 120m 3 、Cyanide-containing wastewater 50m 3 、30m3 of chromium-containing wastewater 3 , suspended matter concentration 2000mg / L), firstly, the large ceramic fragments are intercepted by the stainless steel grid, and then the ceramic particles with a particle size of >10μm are separated by the hydrocyclone, and the suspended matter concentration is reduced to below 200mg / L. Then the diversion treatment: ① General electroplating wastewater is adjusted to pH 7.8 and then PAC and PAM are added for flocculation. After precipitation, the sludge contains Ni 12%, Cu 8%, and the supernatant Ni 2+ ≤0.5mg / L; ② Cyanide-containing wastewater is oxidized twice with sodium hypochlorite (total dosage 7.8kg / m 3 ), CN - The concentration dropped from 150 mg / L to undetectable; ③ Sodium sulfite (24 kg / m 3 )Reduction of Cr 6+ To Cr 3+ , after precipitation, the total Cr is ≤0.1mg / L. The three types of pretreated wastewater are combined and flocculated repeatedly. The effluent is adsorbed by activated carbon-hydroxyapatite composite filler (loaded with sulfate-reducing bacteria biofilm) for 30 minutes, and then deeply purified by reverse osmosis membrane (water production rate 85%). The final purified water COD is <10mg / L, and the heavy metal concentration is less than 0.02mg / L. After the metal-containing sludge is leached with 2mol / L sulfuric acid (leaching rate ≥98%), a titanium-based coated electrode (150A / m 2 ) electrolysis for 4 hours, recovering nickel (purity 99.2%) and copper (purity 98.5%), with a recovery rate of ≥95%, reducing the cost of treating a ton of water to 18 yuan, generating annual metal recovery revenue of 720,000 yuan, a wastewater reuse rate of 90%, and a sludge reduction of 70%, achieving pollutant discharge standards and efficient resource reuse.

[0027] In summary, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the claims of the present invention.

Claims

1. A ceramic electroplating wastewater treatment and metal recovery process, characterized in that: The method comprises the following steps: S1: classifying and collecting ceramic electroplating wastewater, wherein the ceramic electroplating wastewater comprises general electroplating wastewater, cyanide-containing electroplating wastewater, chromium-containing electroplating wastewater and ceramic suspended matter; S2: pre-treating the ceramic electroplating wastewater, including removing the ceramic suspended matter by grid filtration and cyclone separation in sequence; S3: The pretreated ceramic electroplating wastewater is diverted and treated by category: S31, sodium hydroxide and calcium hydroxide are added to the general electroplating wastewater to adjust the pH to 7.5-8.0, polyaluminium chloride and polyacrylamide are added for flocculation, and solid-liquid separation is performed after precipitation to obtain a first upper clear liquid and metal-containing sludge; S32, the cyanide-containing electroplating wastewater is adjusted to a pH of 10.5-11.0, sodium hypochlorite is added twice to oxidize cyanide, and pretreated cyanide-containing wastewater is obtained after neutralization; S33, sulfuric acid and sodium sulfite are added to the chromium-containing electroplating wastewater to reduce hexavalent chromium to trivalent chromium, and the pH is adjusted to 7.5-8.5 and then precipitated to obtain pretreated chromium-containing wastewater; S4: merging the pretreated cyanide-containing wastewater and the pretreated chromium-containing wastewater into the general electroplating wastewater to form comprehensive wastewater, and repeating step S31 to perform flocculation and sedimentation treatment; S5: sequentially subjecting the first supernatant and the second supernatant treated in S4 to adsorption and reverse osmosis treatment to obtain qualified purified water; S6: subjecting the metal-containing sludge to acid leaching, dissolving it, and recovering the metal element by electrolysis.

2. The ceramic electroplating wastewater treatment and metal recovery process according to claim 1, characterized in that: The centrifugal force of the cyclone separation in step S2 is 2000-4000 g, and ceramic particles with a particle size greater than 10 μm are separated.

3. The ceramic electroplating wastewater treatment and metal recovery process according to claim 1, characterized in that: In the step S31, the dosage of polyaluminium chloride is 1‰ to 5‰ of the volume of the wastewater, and the dosage of polyacrylamide is 0.1‰ of the volume of the wastewater.

4. The ceramic electroplating wastewater treatment and metal recovery process according to claim 1, characterized in that: In step S32, the mass ratio of the first addition of sodium hypochlorite is 3.5 to 4.5 times that of the cyanide ion, and the mass ratio of the second addition is 10 to 15 times, and the stirring time for each time is 15 to 30 minutes.

5. The ceramic electroplating wastewater treatment and metal recovery process according to claim 1, characterized in that: In step S33, the dosage of sodium sulfite is controlled to control the redox potential to be 200-300 mV, and the reaction time is 20-40 min.

6. The ceramic electroplating wastewater treatment and metal recovery process according to claim 1, characterized in that: In the step S5, the adsorption treatment uses a composite filler of activated carbon and hydroxyapatite, and the surface of the filler is loaded with a sulfate-reducing bacteria biofilm.

7. The ceramic electroplating wastewater treatment and metal recovery process according to claim 1, characterized in that: The acid leaching treatment in step S6 uses a sulfuric acid solution with a concentration of 1 to 3 mol / L, and the current density during electrolysis is 100 to 200 A / m².

8. The ceramic electroplating wastewater treatment and metal recovery process according to claim 7, characterized in that: The electrolysis method adopts titanium-based coated electrodes, and the metal recovery rate after electrolysis is not less than 95%.

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