TWI658007B - Method of synthesizing granular basic nickel oxide from nickel-contained wastewater by using fluidized-bed crystallization technology - Google Patents

Abstract

The invention relates to a method for synthesizing basic nickel oxide crystals by fluidized bed crystallization technology. In addition to the efficient removal of nickel ions in water, this method can reduce the use of chemicals. Furthermore, this method does not require the use of a heterogeneous support in a fluidized bed reaction tank. The water quality conditions were adjusted including pH, cross-section load, hydraulic retention time, etc., and the fluidized bed homogeneous crystallization system was used to recover the crystalline particles of the nickel salt to remove nickel ions in the wastewater. The treatment efficiency and purity of the crystalline particles obtained by this method are high, and the utilization potential is high.

Description

Method for synthesizing basic nickel oxide crystals from nickel-containing wastewater by fluidized bed crystallization technology

The invention relates to a method for synthesizing and recovering basic nickel oxide crystals from nickel-containing wastewater, in particular to a method for synthesizing basic nickel oxide crystals from nickel-containing wastewater by a fluidized bed crystallization technology.

Nickel is widely used in human life today. In industrial applications, nickel has the ability to alloy with other metals. The nickel-containing alloy produced can increase the physical strength, corrosion resistance, and temperature resistance of the overall metal. Nickel is widely used in the production of stainless steel, non-ferrous metal alloys, super alloys and other industries. In addition, nickel also has a large use ratio in the electroplating industry and the battery industry. In the battery field, basic nickel oxide (NiOOH) can be used The positive electrode material of nickel-zinc alkaline batteries also has applications of nickel-metal hydride batteries and new-generation rechargeable nickel-zinc batteries in secondary batteries.

It is known in the literature that in the nickel mine drainage system, tableware plating and metal processing industry, the concentration of nickel in the wastewater discharged by the industry reaches 130 ppm. In addition, there is even a pickling process in the electroplating industry. 2-900 ppm nickel-containing wastewater is generated and is currently the main known source of pollution. The most common method in conventional nickel removal technology is chemical coagulation, which uses a precipitating agent to adjust the appropriate pH value by adding an alkali solution, reacts with nickel ions to form a solid precipitation solution, and cooperates with the addition of a polymer flocculant to co-exist. Precipitation mechanism to achieve the purpose of removing nickel. Although chemical coagulation sedimentation has simple operation and good nickel removal effect, a large amount of chemicals need to be added in the nickel removal process. The solid waste produced by it has a high moisture content (that is, nickel sludge with high moisture content), which has an impact on the environment. The low purity of the solid causes the trouble and harm of the subsequent solid-liquid separation and recovery.

In recent years, fluidized bed crystallization technology for nickel removal has begun to receive attention, and is gradually applied in sewage plants. A conventional "fluidized bed crystallization technology" processing device includes a fluidized bed reaction tank having a support body therein. The waste water to be treated flows upward from the bottom of the reaction tank, so that the support body reaches a certain upstream speed and is fluidized, and the reaction tank is connected to the medicine inlet for feeding the medicine, so that the pollutants in the wastewater are in the support body of the reaction tank. It is crystallized to remove anions or metal ions in the wastewater and recover reusable metal particles. However, the conventional "fluidized bed crystallization technology" needs to add a support (such as silica sand, brick powder, etc.) in the reaction tank for crystallization, resulting in heterogeneous support components in the metal crystal, and the purity of the crystal is not good. Negatively impact the value of reuse.

Nickel is widely used in various industries and has certain product raw material requirements. If nickel can be removed from wastewater, it can also be recovered as nickel salts of commercial value, and it can also achieve the sustainable use of resources. value.

For this reason, the main object of the present invention is to provide a method for synthesizing basic nickel oxide crystals from nickel-containing wastewater by a fluidized bed crystallization technology. The method has the advantages of high efficiency, low cost, no sludge, and the like. Nickel oxide crystals have high purity and can be used in the battery material industry.

According to an embodiment of the present invention, the method for synthesizing basic nickel oxide crystals from nickel-containing wastewater by using fluidized bed crystallization technology includes: providing a fluidized bed reaction tank, the reaction tank has a lower section and an upper section, and the lower section is provided with There is a solution inlet and a medicament inlet. The upper section is provided with a water outlet. There is a return line between the lower section and the upper section. There is no heterogeneous support in the reaction tank. The nickel-containing solution and the medicament are individually introduced into the solution. The inlet and the inlet of the medicament are introduced into the reaction tank for mixing, wherein the medicament contains an oxidant that can oxidize divalent nickel salts or nickel hydroxide in an alkaline solution to produce trivalent nickel basic nickel oxide (NiOOH) products; The nickel-containing solution mixed with the agent flows from the lower section of the reaction tank to the upper section of the reaction tank; and the nickel-containing solution mixed with the agent is returned to the lower section through the return pipe for circulation, so that the nickel ions in the nickel-containing solution and agent to produce a basic reaction of nickel oxide particles, wherein the effluent water pH (pH _e) controlled between 7-10, and the nickel-containing solution sectional load (L) to control a 3.5kg m ^-2 h ^-1 between.

In a preferred embodiment, the oxidant is sodium hypochlorite (NaClO), and the initial molar ratio of free chlorine to nickel in the oxidant is controlled between 0.5 and 2.1. The medicament further contains a carbonic acid solution as a stabilizer. The carbonic acid solution is a sodium carbonate solution, and the molar ratio of the sodium carbonate solution to the nickel-containing solution is controlled to be between 0.5 and 1.5.

In a preferred embodiment, the hydraulic retention time is controlled between 15 and 50 minutes to obtain a high nickel ion removal rate and crystallization ratio.

In a preferred embodiment, before the nickel-containing solution mixed with the agent is operated under reflux, the nickel-containing solution and the agent are mixed in the reaction tank to produce basic nickel oxide crystal particles as a support, and control The particle bed height is between 0.25-0.75 times the tube length in the lower section of the reaction tank to obtain a high nickel ion removal rate and crystallization ratio.

In one embodiment, the system control between the hydraulic retention time 16.4min to 40.9min, and the reaction pH (pH _e) is controlled between 9 to 10 the preferred embodiment.

Other objects, advantages and features of the present invention will be understood from the following detailed description of the preferred embodiments and with reference to the accompanying drawings.

The invention is to propose a method for synthesizing basic nickel oxide crystals from nickel-containing wastewater by using a fluidized bed crystallization technology. The method is to remove and recover nickel in a nickel-containing solution (such as nickel-containing wastewater), which can reduce chemical The use of pharmaceuticals, and without adding heterogeneous support, synthesizes high-purity, low-water-content basic nickel oxide crystal particles in the system to recover heavy metal elements in wastewater, and thereby improves the recovered nickel salt crystals. Added value of particles. Furthermore, the method of the present invention can treat wastewater with a nickel content in the range of 100-2000 ppm, and effectively remove the nickel content to an average concentration of less than 10 ppm. Therefore, the method can be applied to the treatment of wastewater containing heavy metals generated in the process of electroplating industry. Or other groundwater treatment of nickel-containing metals to solve pollution problems.

Referring to FIG. 1, the method of the present invention first provides a fluidized bed reaction tank 10 having a tubular lower section 12 and a tubular upper section 14. The lower section 12 is provided with a solution inlet 16 and a medicament inlet 18, the upper section 14 is provided with a water outlet 20, and a return pipe 22 is provided between the lower section 12 and the upper section 14. In the present embodiment, the bottom of the lower section 12 of the reaction tank 10 is conical, which helps to distribute the backflow flow force uniformly. An acid-base value (pH) detector 24 is set at the water outlet 20 to monitor the pH of the outlet, and water samples are collected for water quality analysis. Next, the nickel-containing solution (for example, nickel-containing wastewater) 30 and the medicine 32 are individually introduced into the lower stage 12 of the reaction tank 10 from the solution inlet 16 and the medicine inlet 18 by the two pumps 26 and 28, respectively. Next, the nickel-containing solution 30 mixed with the agent 32 is flowed from the lower section 12 to the upper section 14, and then the nickel-containing solution 30 of the mixed agent 32 is returned to the lower section 12 via the return line 22 to be circulated, so that the nickel-containing solution 30 The nickel ion reacts with the pharmaceutical agent 32 in a granulating reaction. The medicament 32 includes an oxidant and a stabilizer. In this embodiment, sodium hypochlorite (NaClO), which is relatively inexpensive, is used as an oxidant, and a carbonate solution (such as sodium carbonate) is used as a stabilizer and a buffer solution to synthesize a battery material that can be provided. Homogeneous particles of basic nickel oxide (NiOOH) that are widely used in industry.

According to the method of the present invention, the pH value of the effluent water (pH _e ), the initial molar ratio of free chlorine to nickel in the oxidant (Cl _free / Ni), the cross-sectional load (L _Ni ) of the nickel-containing solution, and the reactor The hydraulic retention time (HRT) of treating nickel-containing wastewater will affect the nickel ion removal rate (nickel removal efficiency) and the granulation rate (crystallization ratio) after the particles are stabilized in the nickel-containing solution 30, respectively. Furthermore, the nickel-containing solution 30 and the agent can be introduced into the reaction tank 10 and mixed under operating or non-operating reflux conditions to produce basic nickel oxide particles as a support, so as to provide sufficient surface area for the growth of new crystals. The crystalline particles are attached to generate new particles again to avoid the formation of gelatinous precipitates containing a large amount of water. The particle bed height of the support (the height of the particles deposited in the reaction tank, H) should be controlled between 12 tubes in the lower section of the reaction tank Between 0.25-0.75 times. In this embodiment, the 12 tubes in the lower section of the reaction tank are about 80 cm long, and the particle bed height is preferably between 30 cm and 65 cm.

According to the test results, in the system for synthesizing basic nickel carbonate, the pH value (pH _e ) should be controlled between 7 and 10, and the cross-sectional load (L) of the nickel-containing solution should be controlled between 1 and 3.5 kg m ^-2 Between h ^-1 , the hydraulic retention time should be controlled between 15 and 50 min, and the initial molar ratio of free chlorine [Ni] to nickel in the oxidant (Cl _free / Ni) can be controlled between 0.5 and 2.1.

Referring to FIG. 2 (a), it is shown that in a system for synthesizing basic nickel oxide, the initial nickel concentration (C _{Ni, in} ) operating in a nickel-containing solution is 1070 ± 30 ppm, and the initial mole of free chlorine in the oxidant to nickel is molar. The ratio (Cl _free / Ni) is 1.0 ± 0.1, the feed molar ratio (C _CO3 / C _Ni ) of the sodium carbonate (stabilizer) solution to the nickel-containing solution is 1.05 ± 0.05, and the hydraulic retention time (HRT) is 16.4 Under the conditions of min, feed upstream speed (U) of 42.9m / hr and particle bed height (H) of 50cm, the change of pH value (pH _e ) to the crystallization ratio (CR%) and nickel removal efficiency (TR%) )Impact. It has been found through experiments that when pH _e gradually increases from 7.19 to 9.22, CR and TR in the system will gradually increase. This reason can be understood from the dissolution curve in Figure 2 (b). When pH _e rises, the degree of supersaturation in the system It also increases at the same time, thus resulting in the improvement of CR and TR. At pH _e of 9.22, the system has a maximum CR value of 97.9% and a TR value of 99.6%. After filtration, the soluble nickel concentration is C _{Ni, s} is 2.31 ppm, and the residual chlorine concentration C _{Cl, residual} is 0.14 ppm. When the pH _e range is 9.22 to 10.29, it can be seen from Figure 2 (b) that the degree of oversaturation in the system also continues to increase. However, under the condition of too much saturation, the crystallization behavior will begin to change to Initial nucleation occurs, so when the pH _e value is higher, the system will produce more sludge to cause the aqueous solution at the outflow port to become cloudy, so the CR value will gradually decrease. In the TR part, under this high supersaturation pH _e range, the system supersaturation only slightly increases the TR, and its values are all above 99%.

Referring to FIG. 3, it is shown that in a system for synthesizing basic nickel oxide, an initial nickel concentration (C _{Ni, in} ) operating in a nickel-containing solution is 1075 ± 15 ppm, and an initial molar ratio of free chlorine to nickel in the oxidant ( Cl _free / Ni) is 0.9 ± 0.05, the molar ratio of the feed of sodium carbonate solution to the nickel-containing solution (C _CO3 / C _Ni ) is 0.94 ± 0.02, the pH value (pH _e ) is 9.3 ± 0.2, the feed Effects of different hydraulic retention times (HRT) on crystallization ratio (CR%) and nickel removal efficiency (TR%) under conditions of upflow speed (U) of 42.9 m / hr and particle bed height (H) of 50 cm . It is found through experiments that when the HRT time is increased to the range of 16.4 min to 40.9 min, the cross-section load in this range is 2.6 kg m ^-1 hr ^-1 to 1 kg m ^-1 hr ^-1 . Small oversaturation, so the CR value rises to a stable 97-98.5% in this interval. When the HRT is 16.4 min, the system starts to have a high CR value (> 97%). Considering the maximum amount of wastewater that can be treated by this technology per unit time, the optimal operating condition is set at HRT of 16.4 min.

Referring to FIG. 4, it is shown that in a system for synthesizing basic nickel oxide, the initial molar ratio of free chlorine to nickel (Cl _free / Ni) operating in the oxidant is 1.0 ± 0.1. The feed molar ratio (C _CO3 / C _Ni ) is 1.0 ± 0.05, the pH value (pH _e ) is 9.3 ± 0.2, the hydraulic retention time (HRT) is 16.4 min, and the feed upstream speed (U) is 42.9 m / Under the conditions of hr and particle bed height (H) of 50 cm, the effect of the cross-sectional load (L) of nickel-containing solutions of different sizes on the crystallization ratio (CR%) and the nickel removal efficiency (TR%). It was found through experiments that when the different nickel feed concentrations were changed between 634-1459 ppm and the cross-sectional load was in the range of 1.5-3.5 kg m ^-2 h ^-1 , the system was controlled to a suitable supersaturation, so It can effectively recover nickel ions in synthetic wastewater in the form of homogeneous particles. Its CR is as high as 96-97%, TR is greater than 99%, and only about 2-3% of sludge is generated. When the cross-section load increased from 3.5 kg m ^-2 h ^-1 to 5.0 kg m ^-2 h ^-1 , corresponding to the nickel feed concentration of 1459 ppm to 2096 ppm, the CR value of the system began to follow the cross section due to the increase of the system's supersaturation. The load increases and decreases, but at a feed nickel concentration of up to 2096 ppm, its CR still reaches 88% and TR is 99.5%, indicating that this technology can effectively treat and recover high-concentration nickel-containing wastewater. Further, referring to FIG. 5, which shows the nickel concentration in the feed changed and changing conditions of nickel feed flow rate the cross-sectional change in load, when the range of the cross-section of the load 1 kg m ^-2 h ^-1 to 3.5 kg m ^-2 h ^- When it is between ¹ , the CR values of the two are similar to each other, either by changing the nickel feed concentration or changing the nickel feed flow rate. However, when the cross-section load is 3.5 kg m ^-2 h ^-1 to 5 kg In the range of m ^-2 h ^-1 , the distance between the two CR curves will gradually increase with the increase of the cross-sectional load. Changing the cross-sectional load with different feed flow rates has a higher CR value (crystal recovery rate). On the other hand, adjusting the cross-section load in two ways does not affect the size of the TR value, both of which are greater than 99%.

Referring to FIG. 6, in a system for synthesizing basic nickel oxide, an initial nickel concentration (C _{Ni, in} ) operating in a nickel-containing solution is 1065 ± 25 ppm, and an initial molar ratio of free chlorine to nickel in the oxidant ( Cl _free / Ni) is 0.9 ± 0.04, the molar ratio of the feed of sodium carbonate solution to nickel-containing solution (C _CO3 / C _Ni ) is 0.94 ± 0.02, the pH value (pH _e ) is 9.3 ± 0.2, hydraulic retention Effects of different particle bed heights (H) on crystallization ratio (CR%) and nickel removal efficiency (TR%) under the conditions of time (HRT) of 16.4 min and feed upstream speed (U) of 42.9 m / hr. It was found through experiments that when the bed height (H) is less than 30 cm, the system does not have a sufficient amount of effective crystal growth surface area, so excess nickel ions remain in the solution, which makes the system too much saturated and generates a large amount of Sludge, therefore, reduces the proportion of nickel ions into homogeneous particles, resulting in a reduction in crystallization rate. When the bed height is greater than 30 cm, the system can reach a stable CR value at this time, indicating that there is a sufficient amount of crystal growth surface area in the system for crystal recovery.

From the experimental results in the figure above, it can be seen that in the system for synthesizing basic nickel oxide, it can be found that free chlorine is almost completely consumed, and under the optimal operating conditions (pH _e = 9.2, Cl _free / Ni = 1, CO ₃ / Ni = 1, HRT = 16.4 min, U = 42.9 m / hr), can reach a CR of 98% and a TR of 99.6%, the nickel concentration in the effluent water is reduced to 2.31 ppm, and the residual chlorine concentration is 0.14 ppm. Under the condition that the feed flow rate of nickel is 30 ml / min, when the cross-sectional load is controlled within 3.5 kg m ^-2 hr ^-1 , the CR value is 96%-98%, indicating that the basic nickel oxide has excellent Ability to crystallize particles. Furthermore, in terms of product identification of synthetic particles, SEM analysis shows that the inside and outside of basic nickel oxide particles are homogeneous crystals with distinct crystal structures, and XRD, FTIR, EDS, TGA and other analysis can confirm that The main component of black homogeneous particles produced by sodium hypochlorite as oxidant is NiOOH · x Ni (OH) ₂ with crystal water. In addition, the analysis result of basic nickel oxide particles is that the molar ratio of Ni: O: C is about 1: 2.12: 0.49. It can be inferred that the proportion of carbon in the composition of basic nickel oxide particles is very small, indicating that during the synthesis process When carbonic acid is used as a buffer solution and a stabilizer of sodium hypochlorite, during the precipitation of NiOOH, the proportion of basic nickel carbonate is inferred to be very small, which will not affect the NiOOH · xNi (OH) _{2 in the} basic nickel oxide particles of FBHC. Of purity. In addition, the Ni: O mole ratio in the particle analysis is about 1: 2.12, which is in accordance with the NiOOH and Ni (OH) ₂ chemical formula. The ratio of Ni to O is 1: 2, indicating that NiOOH and Ni (OH) _{2 are} A high ratio is present in the basic nickel oxide particles.

According to the method of the present invention, the nickel-containing wastewater can be treated to achieve high-efficiency removal of nickel ions in the water to meet the standard of draining water, and the basic nickel oxide crystals can be recovered and reused effectively. Furthermore, the method of the present invention adopts a homogeneous nucleation crystallization technology, which does not need to add a heterogeneous support in a fluidized bed reaction tank first, resulting in a high purity of the obtained crystals, which is beneficial for subsequent processing applications. Therefore, the method of the present invention can not only replace chemical coagulation to achieve an excellent treatment effect, but also avoid the defects of traditional chemical or biological methods, and achieve the purpose of product resource utilization, and has the advantages of high efficiency, low cost, no sludge, etc. .

In the foregoing description, the present invention has been described only with reference to specific embodiments, and various changes or modifications can be made according to the features of the present invention. Therefore, obvious replacements and modifications that can be made by those skilled in the art will still be included in the scope of patents claimed by the present invention.

10‧‧‧ reaction tank

12‧‧‧ lower paragraph

14‧‧‧upper

16‧‧‧ solution inlet

18‧‧‧ medicine inlet

20‧‧‧ Outlet

22‧‧‧ return line

24‧‧‧ pH detector

26‧‧‧Pu

28‧‧‧Pu

30‧‧‧ Nickel-containing solution

32‧‧‧ Elixir

FIG. 1 is a schematic diagram of a fluidized bed reaction tank according to an embodiment of the present invention.

Figure 2 (a) shows the relationship between the pH value (CR _e ) and the nickel removal efficiency (TR%) of different acid-base values (pH _e ) in a fluidized bed granulated basic nickel oxide system. Illustration.

FIG. 2 (b) is a graph showing the dissolution profile of basic nickel oxide under different pH values (pH _e ) under the operating conditions of FIG. 2 (a).

FIG. 3 is a graph showing the relationship between different hydraulic retention time (HRT) on the crystallization ratio (CR%) and the nickel removal efficiency (TR%) in a fluidized bed granulated synthetic nickel oxide system.

FIG. 4 is a graph showing the relationship between the cross-sectional load (L) of different nickel-containing solutions on the crystallization ratio (CR%) and the nickel removal efficiency (TR%) in a system for fluidized bed granular synthesis of basic nickel oxide.

FIG. 5 shows different cross-sectional loads of nickel-containing solutions under conditions where the cross-sectional load is changed by changing the feed nickel concentration and changing the nickel feed flow rate in a fluidized bed granulated synthetic nickel oxide system. L) Effect of crystallization ratio (CR%) and nickel removal efficiency (TR%).

FIG. 6 is a graph showing the relationship between different particle bed heights (H) on the crystallization ratio (CR%) and the nickel removal efficiency (TR%) in a fluidized bed granulated synthetic nickel oxide system.

Claims (8)

A method for synthesizing basic nickel oxide crystals from nickel-containing wastewater by fluidized bed crystallization technology, comprising: providing a fluidized bed reaction tank having a lower section and an upper section, the lower section being provided with a solution inlet and a A medicine inlet, the upper section is provided with a water outlet, a return line is provided between the lower section and the upper section, and the reaction tank does not have a heterogeneous carrier; the nickel-containing solution and the agent are individually separated from the solution inlet and the The medicament inlet is introduced into the fluidized bed reaction tank for mixing, wherein the medicament includes an oxidant that can oxidize divalent nickel salts or nickel hydroxide in an alkaline solution to produce trivalent nickel basic nickel oxide (NiOOH) products; The nickel-containing solution mixed with the agent flows from the lower section of the reaction tank to the upper section of the reaction tank; and the nickel-containing solution mixed with the agent is returned to the lower section through the return pipe to circulate, so that the nickel in the nickel-containing solution is circulated. the reaction with an agent to produce a basic ion nickel oxide particles, wherein the effluent water pH (pH _e) controlled between 7-10, and the nickel-containing solution sectional load (L) to control a 3.5kg m ^-2 h Between ^-1 . The method according to item 1 of the patent application scope, wherein the agent further comprises a carbonic acid solution as a stabilizer. The method according to item 2 of the scope of the patent application, wherein the carbonic acid solution is a sodium carbonate solution, and the feed molar ratio of the sodium carbonate solution to the nickel-containing solution is controlled between 0.5 and 1.5. The method according to item 1 of the patent application range, wherein the oxidant is sodium hypochlorite (NaClO), and the initial molar ratio of free chlorine to nickel in the oxidant is controlled between 0.5 and 2.1. The method according to item 1 of the patent application range, wherein the hydraulic retention time is controlled between 15 and 50 minutes. The method according to item 5 of the scope of patent application, wherein the hydraulic retention time is controlled between 16.4 minutes and 40.9 minutes. The application method of claim 1 patentable scope clause, wherein the pH of the reaction (pH _e) is controlled between 9-10. The method according to item 1 of the scope of patent application, wherein a nickel-containing solution and a medicament are first mixed in the reaction tank to produce nickel oxide crystal particles as a support, and the bed height of the particles is controlled to a length of the lower tube of the reaction tank. Between 0.25-0.75 times.