CN115316594A - Method for removing cadmium from rice - Google Patents
Method for removing cadmium from rice Download PDFInfo
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- CN115316594A CN115316594A CN202210084368.5A CN202210084368A CN115316594A CN 115316594 A CN115316594 A CN 115316594A CN 202210084368 A CN202210084368 A CN 202210084368A CN 115316594 A CN115316594 A CN 115316594A
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- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 title claims abstract description 236
- 229910052793 cadmium Inorganic materials 0.000 title claims abstract description 234
- 235000007164 Oryza sativa Nutrition 0.000 title claims abstract description 141
- 235000009566 rice Nutrition 0.000 title claims abstract description 141
- 238000000034 method Methods 0.000 title claims abstract description 27
- 240000007594 Oryza sativa Species 0.000 title 1
- 241000209094 Oryza Species 0.000 claims abstract description 140
- 238000003756 stirring Methods 0.000 claims abstract description 68
- 239000002253 acid Substances 0.000 claims abstract description 59
- 239000000725 suspension Substances 0.000 claims abstract description 57
- 235000013312 flour Nutrition 0.000 claims abstract description 53
- 239000002002 slurry Substances 0.000 claims abstract description 44
- 238000002386 leaching Methods 0.000 claims abstract description 34
- 238000000926 separation method Methods 0.000 claims abstract description 27
- 238000011282 treatment Methods 0.000 claims abstract description 25
- 239000000843 powder Substances 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 238000001556 precipitation Methods 0.000 claims description 23
- 239000000706 filtrate Substances 0.000 claims description 16
- 239000003795 chemical substances by application Substances 0.000 claims description 15
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical group [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 12
- 239000000084 colloidal system Substances 0.000 claims description 11
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 10
- 238000001914 filtration Methods 0.000 claims description 9
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 8
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical group [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 8
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 6
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 6
- 239000008394 flocculating agent Substances 0.000 claims description 5
- HYHCSLBZRBJJCH-UHFFFAOYSA-M sodium hydrosulfide Chemical compound [Na+].[SH-] HYHCSLBZRBJJCH-UHFFFAOYSA-M 0.000 claims description 5
- 238000005189 flocculation Methods 0.000 claims description 4
- 230000016615 flocculation Effects 0.000 claims description 4
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 4
- 230000001376 precipitating effect Effects 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 abstract description 91
- 102000004169 proteins and genes Human genes 0.000 abstract description 8
- 108090000623 proteins and genes Proteins 0.000 abstract description 8
- 239000012736 aqueous medium Substances 0.000 abstract description 4
- 238000000227 grinding Methods 0.000 abstract description 2
- 239000002245 particle Substances 0.000 description 20
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 18
- 239000012065 filter cake Substances 0.000 description 13
- 238000000855 fermentation Methods 0.000 description 11
- 230000004151 fermentation Effects 0.000 description 11
- 239000004310 lactic acid Substances 0.000 description 9
- 235000014655 lactic acid Nutrition 0.000 description 9
- 239000000047 product Substances 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 239000007788 liquid Substances 0.000 description 8
- 229920002401 polyacrylamide Polymers 0.000 description 8
- 238000005086 pumping Methods 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 5
- 239000000872 buffer Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000003472 neutralizing effect Effects 0.000 description 4
- WUPHOULIZUERAE-UHFFFAOYSA-N 3-(oxolan-2-yl)propanoic acid Chemical compound OC(=O)CCC1CCCO1 WUPHOULIZUERAE-UHFFFAOYSA-N 0.000 description 3
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 3
- 235000013305 food Nutrition 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 239000006228 supernatant Substances 0.000 description 3
- 229910000011 cadmium carbonate Inorganic materials 0.000 description 2
- GKDXQAKPHKQZSC-UHFFFAOYSA-L cadmium(2+);carbonate Chemical compound [Cd+2].[O-]C([O-])=O GKDXQAKPHKQZSC-UHFFFAOYSA-L 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 235000020195 rice milk Nutrition 0.000 description 2
- 230000009469 supplementation Effects 0.000 description 2
- 206010006002 Bone pain Diseases 0.000 description 1
- 241000186660 Lactobacillus Species 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- WLZRMCYVCSSEQC-UHFFFAOYSA-N cadmium(2+) Chemical compound [Cd+2] WLZRMCYVCSSEQC-UHFFFAOYSA-N 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 238000005352 clarification Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000010903 husk Substances 0.000 description 1
- 229940039696 lactobacillus Drugs 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- IHYNKGRWCDKNEG-UHFFFAOYSA-N n-(4-bromophenyl)-2,6-dihydroxybenzamide Chemical compound OC1=CC=CC(O)=C1C(=O)NC1=CC=C(Br)C=C1 IHYNKGRWCDKNEG-UHFFFAOYSA-N 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- 239000002689 soil Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- -1 sulfur ion Chemical class 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
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Classifications
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- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L7/00—Cereal-derived products; Malt products; Preparation or treatment thereof
- A23L7/10—Cereal-derived products
- A23L7/198—Dry unshaped finely divided cereal products, not provided for in groups A23L7/117 - A23L7/196 and A23L29/00, e.g. meal, flour, powder, dried cereal creams or extracts
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L5/00—Preparation or treatment of foods or foodstuffs, in general; Food or foodstuffs obtained thereby; Materials therefor
- A23L5/20—Removal of unwanted matter, e.g. deodorisation or detoxification
- A23L5/27—Removal of unwanted matter, e.g. deodorisation or detoxification by chemical treatment, by adsorption or by absorption
- A23L5/276—Treatment with inorganic compounds
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Health & Medical Sciences (AREA)
- Nutrition Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Polymers & Plastics (AREA)
- Processing Of Solid Wastes (AREA)
Abstract
The invention discloses a method for removing cadmium from rice, which comprises the following steps: crushing and grinding the cadmium rice to obtain powdery cadmium rice; mixing the cadmium rice in powder form with water to obtain a suspension slurry; adding the suspension slurry and an acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution to obtain a cadmium-removed rice flour suspension; conveying the rice flour suspension to a separation container to separate cadmium-removed rice flour from the first cadmium-containing solution. The stable suspendability and the fluidity of rice protein in an aqueous medium are realized by adopting the powdery cadmium rice, so that the leaching cadmium removal treatment time is obviously shortened, the reaction efficiency in the stirring barrel is improved by adding the suspension slurry into the stirring barrel, and the working space for leaching cadmium removal is obviously shortened. In addition, the suspension slurry and the acid solution are stirred by the stirring barrel, so that the cadmium removal efficiency can be improved, and the method can be applied to rice cadmium removal in a large scale.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a method for removing cadmium from rice.
Background
Two thirds of the population in China takes rice as staple food, so the safety relation of the rice is important. According to the national soil survey in 2014, the cadmium-polluted rice field in China exceeds 28 million hectares (420 million mu), and the overproof rate reaches 7 percent. As the rice itself is easy to absorb and accumulate cadmium in the environment, cadmium metal in the rice is easy to exceed the standard (GB/T1354-2018 rice, 0.2 mg/kg). People eating cadmium rice for a long time can cause pain (namely bone pain). The prior published literature reports that cadmium is removed by acid leaching. The prior art mainly adopts intermittent leaching reaction, the efficiency of leaching and cadmium removal is remarkably low, and the large-scale and continuous rice cadmium removal is not facilitated.
Disclosure of Invention
Therefore, a rice cadmium removal method is needed to be provided to solve the technical problems that the rice cadmium removal efficiency is remarkably low and the large-scale and continuous rice cadmium removal is not facilitated in the prior art.
The invention provides a method for removing cadmium from rice, which comprises the following steps:
the cadmium rice is crushed and ground to obtain powder cadmium rice;
mixing the cadmium rice in powder form with water to obtain a suspension slurry;
adding the suspension slurry and an acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution to obtain a cadmium-removed rice flour suspension;
and conveying the rice flour suspension into a separation container to separate the cadmium-removed rice flour from the first cadmium-containing solution.
Further, the agitator sets up to a plurality ofly, it is a plurality of the agitator communicates in proper order, suspension thick liquids and acid solution are in a plurality of stir in the agitator in proper order to obtain the rice flour suspension that takes off the cadmium.
Further, the pH value of the suspension slurry and the acid solution in the stirring barrel is 0.5-2.
Further, the step of transferring the rice flour suspension to a separation vessel to separate the cadmium-depleted rice flour from the first cadmium-containing solution further comprises:
and adding an acid solution into the first cadmium-containing solution, and performing acid leaching treatment on the first cadmium-containing solution to obtain a second cadmium-containing solution, wherein the cadmium concentration of the second cadmium-containing solution is more than 1mg/L.
Further, adding an acid solution into the first cadmium-containing solution, and performing acid leaching treatment on the cadmium-containing solution to obtain a second cadmium-containing solution, wherein the step of increasing the cadmium concentration of the second cadmium-containing solution to be more than 1mg/L further comprises the following steps:
and adding the powdery cadmium rice into the second cadmium-containing solution to ensure that the pH value of the second cadmium-containing solution is more than 3 to obtain a third cadmium-containing solution.
Further, the step of adding the powdered cadmium rice into the second cadmium-containing solution to make the pH value of the second cadmium-containing solution greater than 3 to obtain a third cadmium-containing solution further comprises:
and adding a first precipitation cadmium removing agent into the third cadmium-containing solution to enable the pH value of the third cadmium-containing solution to be 8-10, and carrying out precipitation cadmium removing treatment on the third cadmium-containing solution to precipitate cadmium-containing colloid.
Further, the first precipitation cadmium removing agent is sodium bicarbonate or sodium carbonate.
Further, the step of adding the cadmium rice in powder form to the second cadmium-containing solution to make the pH of the second cadmium-containing solution greater than 3 to obtain a third cadmium-containing solution further comprises:
and adding a second precipitation cadmium removing agent into the third cadmium-containing solution, and performing precipitation cadmium removing treatment on the third cadmium-containing solution to precipitate cadmium-containing colloid.
Further, the second precipitation cadmium removing agent is sodium sulfide or sodium hydrogen sulfide.
Further, the rice cadmium removing method further comprises the following steps:
precipitating the cadmium-containing colloid from the third cadmium-containing solution subjected to cadmium removal treatment, and adding a flocculating agent for flocculation treatment to obtain a fourth cadmium-containing solution;
and filtering the fourth cadmium-containing solution, and adding the filtrate into the stirring barrel.
The invention provides a method for removing cadmium from rice. The stable suspensibility and the fluidity of rice protein in an aqueous medium are realized by adopting the powdery cadmium rice, so that the leaching and cadmium removing treatment time is obviously shortened, the reaction efficiency in the stirring barrel is improved by adding the suspension slurry into the stirring barrel, and the working space for leaching and cadmium removing is obviously reduced. In addition, the suspension slurry and the acid solution are stirred by the stirring barrel, so that the cadmium removal efficiency can be improved, and the method can be applied to rice cadmium removal in a large-scale and continuous manner.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a flow chart of a rice cadmium removal method according to an embodiment of the present invention;
FIG. 2 is a schematic structural view of a first reaction tank, a second reaction tank and a third reaction tank in an embodiment of the present invention;
FIG. 3 shows Cd concentration from 1mg/L in the embodiment of the present invention 2+ Adding baking soda or soda to the solution to precipitate a basic thermodynamic equilibrium diagram for cadmium removal;
FIG. 4 shows Cd concentration from 1mg/L in the embodiment of the present invention 2+ Adding sodium sulfide or sodium bisulfide into the solution to precipitate the basic thermodynamic equilibrium diagram for removing cadmium.
The main components are as follows:
100. a first reaction tank; 110 a first stirring zone; 200. a second reaction tank; 210. a second stirring zone; 300. a third reaction tank; 310. a third stirring zone; 400. and a flow guide pipe.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments of the present invention, are within the scope of protection of the present invention.
It should be noted that all directional indicators (such as upper, lower, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In addition, "and/or" in the whole text includes three schemes, taking a and/or B as an example, including a technical scheme, and a technical scheme that a and B meet simultaneously; in addition, technical solutions between the embodiments may be combined with each other, but must be based on the realization of the technical solutions by a person skilled in the art, and when the technical solutions are contradictory to each other or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
In some embodiments, as shown in fig. 1, a method for cadmium removal from rice comprises the steps of:
s100, crushing and grinding the cadmium rice to obtain powdery cadmium rice.
S200, mixing the powdered cadmium rice with water to obtain suspension slurry.
S300, adding the suspension slurry and the acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution to obtain the cadmium-removed rice flour suspension.
S400, conveying the rice flour suspension to a separation container to separate cadmium-removed rice flour from the first cadmium-containing solution.
The stable suspendability and the fluidity of rice protein in an aqueous medium are realized by adopting the powdery cadmium rice, so that the leaching cadmium removal treatment time is obviously shortened, the reaction efficiency in the stirring barrel is improved by adding the suspension slurry into the stirring barrel, and the working space for leaching cadmium removal is obviously shortened. In addition, the suspension slurry and the acid solution are stirred by the stirring barrel, so that the cadmium removal efficiency can be improved, and the method can be applied to rice cadmium removal in a large scale.
In particular, the acid solution is food grade hydrochloric acid, preferably lactic acid. The lactic acid can be the ready-made lactic acid purchased, or the lactic acid generated during the fermentation of lactobacillus, and the cadmium-removed rice flour can not be polluted after the cadmium-removed rice is subjected to acid leaching treatment by food-grade hydrochloric acid, so that the rice flour can be eaten at ease.
More specifically, the rice polluted by cadmium is crushed into rice bran, rice husks and broken rice by a threshing crusher, the broken rice is ground into powder, the powder cadmium rice is placed in a stirring barrel, and the mass ratio of the powder cadmium rice to water is 1: 1-5, and adjusting the mixture into uniform suspension slurry. The powdery cadmium rice is beneficial to fully suspending, flowing and rapidly leaching cadmium in an aqueous medium.
Furthermore, a plurality of stirring barrels are arranged and are sequentially communicated, and the suspension slurry and the acid solution are sequentially stirred in the stirring barrels to obtain the cadmium-removed rice flour suspension. Furthermore, the pH value of the suspension slurry and the acid solution in the stirring barrel is 0.5-2.
Specifically, the plurality of stirring barrels can be arranged into a multi-stage fully-mixed flow kettle type reactor, so that the suspension slurry and the acid solution are naturally leached in a cascade mode in the plurality of stirring barrels, and the cadmium removal efficiency is improved. More specifically, the plurality of agitation tanks respectively have a first reaction tank 100, a second reaction tank 200, and a third reaction tank 300, and the first reaction tank 100, the second reaction tank 200, and the third reaction tank 300 are sequentially communicated through a draft tube 400. In actual practice, the number of reaction tanks can be increased or decreased according to the requirements of specific situations. Specifically, the material of the first reaction tank 100, the second reaction tank 200, and the third reaction tank 300 may be, but is not limited to, plastic, stainless steel, cement, wood, and the like. More specifically, the first reaction tank 100, the second reaction tank 200, and the third reaction tank 300 may be square tanks or circular tanks. The suspension slurry is conveyed to the first reaction tank 100 in a pumping or elevated tank mode, the first reaction tank 100 is a leaching reaction tank, a first stirring area 110 is arranged at the bottom of the first reaction tank 100, and the suspension slurry is stirred by the first stirring area 110. An automatic acid adding device is provided in the first reaction tank 100 so that the pH of the suspension slurry is 0.5 to 2. The holding time of the suspension slurry and the acid solution in the first reaction tank 100 is 5-30 min, and then the suspension slurry and the acid solution naturally overflow into the second reaction tank 200 through the draft tube 400.
The second reaction tank 200 is a tank for continuously leaching the long-time stay, a second stirring area 210 is arranged at the bottom of the second reaction tank 200, the second stirring area 210 is used for stirring the suspension slurry and the acid solution flowing into the second reaction tank 200 from the first reaction tank 100, the holding time of the suspension slurry and the acid solution in the second reaction tank 200 is 10-60 min, and then the suspension slurry and the acid solution naturally overflow to the third reaction tank 300 through the draft tube 400.
The third reaction tank 300 is a clarification and separation tank, a third stirring area 310 is arranged at the bottom of the third reaction tank 300, the third stirring area 310 is used for stirring the suspension slurry and the acid solution flowing into the third reaction tank 300 from the second reaction tank 200, and the holding time of the suspension slurry and the acid solution in the third reaction tank 300 is 30-120 min. Cadmium can be removed quickly and efficiently by stirring the first reaction tank 100, the second reaction tank 200 and the third reaction tank 300, so that the rice flour suspension without cadmium can be obtained. In addition, the first reaction tank 100, the second reaction tank 200 and the third reaction tank 300 are connected in a stepped cascade manner, so that natural overflow of leached rice milk at each stage is realized, and the leached rice milk is conveyed to a stirring area of the next reaction tank through the guide pipe 400, so that the rice flour particles can be fully subjected to cadmium removal within the accommodating time of the rice flour particles in each stage of reaction tank to reach the standard.
Further, S400 conveys the rice flour suspension to a separation vessel to separate the cadmium-depleted rice flour from the first cadmium-containing solution. Specifically, the volume of the separation vessel is 5 to 10 times the total volume of the first reaction tank 100, the second reaction tank 200, and the third reaction tank 300. The reaction container is divided into 2-4 relatively isolated areas by a partition board, and an inclined plate sedimentation area is constructed to avoid turbulent fluctuation caused by cadmium-removed rice flour suspension, so that rice flour particles can be naturally settled, precipitated, concentrated and accumulated at the bottom of the separation container, the cadmium-removed rice flour is separated from the first cadmium-containing solution, the cadmium-removed rice flour is extracted by a diaphragm pump at regular time and enters a centrifuge or a plate-and-frame filter press for dehydration, and a rice flour filter cake is obtained. And (3) conveying the rice flour filter cake to a fermentation tank for fermentation treatment after the rice flour filter cake is washed, and producing a rice flour product.
In some embodiments, the step of S400 transferring the rice flour suspension to a separation vessel to separate the cadmium-depleted rice flour from the first cadmium-containing solution further comprises:
s500, adding an acid solution into the first cadmium-containing solution, and performing acid leaching treatment on the first cadmium-containing solution to obtain a second cadmium-containing solution, wherein the cadmium concentration of the second cadmium-containing solution is more than 1mg/L.
Specifically, after the separation of the cadmium-removed rice flour and the first cadmium-containing solution is completed, the first cadmium-containing solution and washing water for washing filter cakes are pumped into a buffer tank, and the first cadmium-containing solution and the washing water are used for the acid leaching cadmium-removing process again after acid preparation. And after repeated acid leaching treatment, obtaining a second cadmium-containing solution, and pumping the second cadmium-containing solution into a neutralization precipitation tank after the cadmium concentration of the second cadmium-containing solution is more than 1mg/L.
More specifically, step S500 of adding an acid solution to the first cadmium-containing solution, and performing acid leaching treatment on the cadmium-containing solution to obtain a second cadmium-containing solution, where a cadmium concentration of the second cadmium-containing solution is greater than 1mg/L further includes:
s600, adding powdered cadmium rice into the second cadmium-containing solution to enable the pH value of the second cadmium-containing solution to be larger than 3 to obtain a third cadmium-containing solution, centrifuging or filter-pressing the third cadmium-containing solution, and returning rice flour particles to the stirring barrel. The powdery cadmium rice has the effect of pre-neutralizing, can save the introduction amount of an alkaline reagent, a precipitation cadmium removing agent and sodium ions, remarkably improve the utilization efficiency of the precipitation cadmium removing agent, and reduce the consumption of the alkaline reagent and the precipitation cadmium removing agent, thereby saving the production cost.
Further, the step S600 of adding powdered cadmium rice into the second cadmium-containing solution to make the pH of the second cadmium-containing solution greater than 3 to obtain a third cadmium-containing solution further comprises:
s700, adding a first precipitation cadmium removing agent into the third cadmium-containing solution to enable the pH value of the third cadmium-containing solution to be 8-10, and carrying out precipitation cadmium removing treatment on the third cadmium-containing solution to precipitate cadmium-containing colloid. Specifically, the first precipitation cadmium removing agent is sodium hydrogen carbonate or sodium carbonate.
Further, S600, adding powdered cadmium rice into the second cadmium-containing solution to make the pH of the second cadmium-containing solution greater than 3, and obtaining a third cadmium-containing solution further includes:
s800, adding a second precipitation cadmium removing agent into the third cadmium-containing solution, and performing precipitation cadmium removing treatment on the third cadmium-containing solution to precipitate cadmium-containing colloid. More specifically, the second precipitation cadmium removing agent is sodium sulfide or sodium hydrogen sulfide. Sodium sulfide or sodium hydrogen sulfide with 1-2 times of stoichiometric ratio is directly added into the third cadmium-containing solution.
Furthermore, the rice cadmium removing method further comprises the following steps:
s910, precipitating and cadmium-removing the third cadmium-containing solution to obtain cadmium-containing colloid, and adding a flocculating agent to perform flocculation treatment to obtain a fourth cadmium-containing solution;
s920, filtering the fourth cadmium-containing solution, and adding the filtrate into a stirring barrel.
Specifically, a flocculating agent is added for flocculation treatment, and a cadmium carbonate primary product or a cadmium sulfide primary product is obtained through recovery. And the precipitated cadmium-containing colloid is recovered by adopting a flocculating agent so as to avoid secondary pollution caused by the cadmium-containing colloid. In addition, the fourth cadmium-containing solution is a leaching solution after multiple acid leaching treatments and precipitation, and due to the high accumulated concentration of soluble protein, the protein can be decomposed by adopting a fermentation method to obtain a lactic acid solution, and the lactic acid solution is clarified and then continuously returned to the acid leaching process.
More specifically, the flocculant is a food grade PAM (polyacrylamide) flocculant.
From 1mg/L Cd, as shown in FIG. 3 2+ Adding baking soda or soda to the solution to precipitate the basic thermodynamic equilibrium diagram for removing cadmium.
From 1mg/L Cd, as shown in FIG. 4 2+ Adding sodium sulfide or sodium hydrogen sulfide into the solution to precipitate a basic thermodynamic equilibrium diagram for cadmium removal, wherein the total cadmium ion concentration is =1mg/L, and the total sulfur ion concentration is =0.0001mol/L.
The technical solution of the present invention is specifically described by the following examples.
Example 1
Taking out the rice contaminated by cadmium metal, shelling, crushing, sorting to obtain crushed rice with a particle size of about 1mm, further crushing into powder particles with a particle size of less than 0.5mm, and confirming the cadmium content of the powder particles. Placing 1000kg powdered cadmium rice into a stirring barrel, adding 2000L water, pumping to a first stirring region at the bottom of a first reaction tank with working space of 1m at a speed of 50L/min 3 And food-grade hydrochloric acid is prepared to adjust the pH value to about 1. The suspension slurry and the acid solution in the first reaction tank naturally overflow and are introduced into a second stirring area of a second reaction tank through a guide pipe, and the working space of the second reaction tank is 2m 3 . The suspension slurry and the acid solution of the feed liquid of the second reaction tank naturally overflow and are introduced into a third stirring area of a third reaction tank through a guide pipe, and the working space of the third reaction tank is 3m 3 . And the suspended slurry and the acid solution in the third reaction tank naturally overflow and are introduced into the separation container through the guide pipe. The working space of the separation vessel was 30m 3 The separation vessel was equipped with an inclined plate 2m wide and 8m long. The inclined plate is arranged at the position 0.5 meter below the transfusion port of the separation container. The horizontal inclination angle of the inclined plate is 65 degrees. And pumping the rice flour particles deposited at the bottom of the separation container by a diaphragm pump every 2 hours, centrifugally separating the rice flour particles, washing adhered residual liquid by spraying water, and then sending the rice flour particles to a fermentation tank for preparing rice flour products for sale.
And mixing the settled supernatant and the centrifugal filtrate, conveying to a buffer tank, adding acid until the pH value is 1, and adding into the first reaction tank for continuous leaching. And pumping the solution after leaching for 10 times into a special stirring tank, adding a new batch of powdery cadmium rice, stirring and neutralizing to enable the pH value to be 5, filtering, returning the rice flour filter cake to the first reaction tank for further leaching, and adding sodium bicarbonate and sodium carbonate into the filtrate in a mass ratio of 10:1, adjusting the pH value of the solution to 8.5, continuously stirring for 20 minutes, adding 0.01 percent of food-grade PAM (polyacrylamide) flocculant, continuously stirring for 1 minute, filtering and washing a filter cake, wherein the filter cake is a primary product containing cadmium carbonate and can be directly sold in the market. The filtrate is returned to the first reaction tank for continuous use, and can enter a special fermentation tank after being recycled for 30 times, the rice protein in the filtrate is fermented and decomposed, and the clear liquid is returned to the first reaction tank for continuous acid supplementation for leaching.
Example 2
Taking out the rice contaminated by cadmium metal, removing shell, crushing, sorting to obtain crushed rice with particle size of about 1mm, further pulverizing into powder particles below 0.5mm, and determining cadmium content. 1000kg of powdered cadmium rice was placed in a stirring tank, 2000 liters of water was added, and pumped to a first stirring zone at the bottom of the first reaction tank at a speed of 50 liters/min. The working space of the first reaction tank is 1m 3 And food-grade hydrochloric acid is prepared to adjust the pH value to about 1. And the suspended slurry and the acid solution in the first reaction tank naturally overflow to the second reaction tank. The working space of the second reaction tank is 2m 3 . And the suspension slurry and the acid solution in the second reaction tank naturally overflow to the third reaction tank. The working space of the third reaction tank is 3m 3 . And naturally overflowing the suspended slurry and the acid solution in the third reaction tank to a separation container. The working space of the separation vessel was 30m 3 . The separation vessel was equipped with an inclined plate having a width of 2m and a length of 8m. The inclined plate is arranged at the position 0.5 meter below the transfusion port of the separation container. The horizontal inclination angle of the inclined plate is 65 degrees. The rice flour particles deposited at the bottom of the separation container are pumped out by a diaphragm pump every 2 hours, the rice flour particles are separated centrifugally, adhered residual liquid is washed by water spraying, and then the rice flour particles are sent to a fermentation tank to prepare rice flour products for sale.
And mixing the settled supernatant and the centrifugal filtrate, conveying the mixture to a buffer tank, adding acid until the pH value is 1, and adding the mixture into a first reaction tank for continuous leaching. And pumping the solution after leaching for 10 times into a special stirring tank, adding a new batch of powdery cadmium rice, stirring and neutralizing to enable the pH value to be 2.5, then filtering, returning the rice flour filter cake to the first reaction tank to be continuously leached, adding sodium sulfide with the stoichiometric ratio coefficient of 1.2 of the precipitation of the total content of cadmium into the filtrate, continuously stirring for 20 minutes, adding 0.005% of food-grade PAM (polyacrylamide) flocculant, continuously stirring for 1 minute, filtering and washing the filter cake, wherein the filter cake is a primary product containing cadmium sulfide and can be directly sold in the market. The filtrate is returned to the first reaction tank for continuous use, and can enter a special fermentation tank after being recycled for 30 times, the rice protein in the filtrate is fermented and decomposed, and the clear liquid is returned to the first reaction tank for continuous acid supplementation for leaching.
Example 3
Taking out the rice contaminated by cadmium metal, removing shell, crushing, sorting to obtain crushed rice with particle size of about 1mm, further crushing into powder of less than 0.5mm, and determining cadmium content. 1000kg of powdered cadmium rice was put into a stirring tank, 2000 liters of water was added, and pumped to a first stirring zone at the bottom of the first reaction tank at a speed of 50 liters/min. The working space of the first reaction tank is 1m 3 And food-grade lactic acid is prepared to adjust the pH value to about 1. And the suspended slurry and the acid solution in the first reaction tank naturally overflow to a second stirring area of the second reaction tank. The working space of the second reaction tank is 2m 3 . And the suspension slurry and the acid solution in the second reaction tank naturally overflow to a third stirring area of a third reaction tank. The working space of the third reaction tank is 3m 3 . And the suspended slurry and the acid solution of the third reaction tank naturally overflow into the separation container. The working space of the separation vessel was 30m 3 . The separation vessel was equipped with an inclined plate having a width of 2m and a length of 8m. The inclined plate is arranged at the position 0.5 meter below the transfusion port of the separation container. The horizontal inclination angle of the swash plate is 75 °. The rice flour particles deposited at the bottom of the separation container are pumped out by a diaphragm pump every 2 hours, the rice flour particles are separated centrifugally, adhered residual liquid is washed by water spraying, and then the rice flour particles are sent to a fermentation tank to prepare rice flour products for sale.
Mixing the settled supernatant and the centrifugal filtrate, delivering the mixture to a buffer tank, preparing lactic acid to pH 1, and adding the mixture into a first reaction tank for continuous leaching. And pumping the solution after leaching for 10 times into a special stirring tank, adding a new batch of powdery cadmium rice, stirring and neutralizing to enable the pH value to be 2.5, then filtering, returning the rice flour filter cake to the first reaction tank to be continuously leached, adding sodium sulfide with the stoichiometric ratio coefficient of 1.2 of the precipitation of the total content of cadmium into the filtrate, continuously stirring for 20 minutes, adding 0.01% of food-grade PAM (polyacrylamide) flocculant, continuously stirring for 1 minute, filtering and washing the filter cake, wherein the filter cake is a primary product containing cadmium sulfide and can be directly sold in the market. The filtrate is returned to the first reaction tank for continuous use, and after being recycled for 30 times, the filtrate can enter a special fermentation tank for fermentation and decomposition of rice protein in the filtrate, and the acidic clear liquid is returned to the first reaction tank for continuous supplement of lactic acid for leaching.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Specifically, the cadmium removal effect of each example is shown in table 1.
TABLE 1
| Item | Example 1 | Example 2 | Example 3 |
| Cadmium content of rice before treatment | 0.86mg/kg | 1.02mg/kg | 0.94mg/kg |
| Cadmium content of treated rice | 0.09mg/kg | 0.15mg/kg | 0.11mg/kg |
| Rate of cadmium removal | 89.53％ | 85.29％ | 88.30％ |
Claims (10)
1. The method for removing cadmium from rice is characterized by comprising the following steps:
the cadmium rice is crushed and ground to obtain powder cadmium rice;
mixing the cadmium rice in powder form with water to obtain a suspension slurry;
adding the suspension slurry and an acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution to obtain a cadmium-removed rice flour suspension;
conveying the rice flour suspension to a separation container to separate cadmium-removed rice flour from the first cadmium-containing solution.
2. The rice cadmium removing method according to claim 1, wherein a plurality of stirring barrels are arranged, the stirring barrels are sequentially communicated, and the suspension slurry and the acid solution are sequentially stirred in the stirring barrels to obtain the cadmium-removed rice flour suspension.
3. The rice cadmium removal method of claim 1, wherein the pH value of the suspension slurry and the acid solution in the stirring barrel is 0.5-2.
4. The rice cadmium removal process of claim 1 wherein the step of transferring the rice flour suspension to a separation vessel to separate the cadmium removed rice flour from the first cadmium containing solution further comprises:
and adding an acid solution into the first cadmium-containing solution, and performing acid leaching treatment on the first cadmium-containing solution to obtain a second cadmium-containing solution, wherein the cadmium concentration of the second cadmium-containing solution is more than 1mg/L.
5. The rice cadmium removing method of claim 4, wherein the step of adding an acid solution to the first cadmium-containing solution to perform acid leaching on the cadmium-containing solution to obtain a second cadmium-containing solution, wherein the cadmium concentration of the second cadmium-containing solution is greater than 1mg/L further comprises:
and adding the powdery cadmium rice into the second cadmium-containing solution to ensure that the pH value of the second cadmium-containing solution is more than 3 to obtain a third cadmium-containing solution.
6. The method for cadmium removal from rice as claimed in claim 5, wherein said step of adding said cadmium rice in powder form to said second cadmium containing solution to provide said second cadmium containing solution with a pH greater than 3 to provide a third cadmium containing solution further comprises:
and adding a first precipitation cadmium removing agent into the third cadmium-containing solution to enable the pH value of the third cadmium-containing solution to be 8-10, and carrying out precipitation cadmium removing treatment on the third cadmium-containing solution to precipitate cadmium-containing colloid.
7. The rice cadmium removal method of claim 6, wherein the first precipitated cadmium removal agent is sodium bicarbonate or sodium carbonate.
8. The method for cadmium removal from rice as claimed in claim 5, wherein said step of adding said cadmium rice in powder form to said second cadmium containing solution to provide said second cadmium containing solution with a pH greater than 3 to provide a third cadmium containing solution further comprises:
and adding a second precipitation cadmium removing agent into the third cadmium-containing solution, and performing precipitation cadmium removing treatment on the third cadmium-containing solution to precipitate cadmium-containing colloid.
9. The rice cadmium removal method of claim 8, wherein the second precipitated cadmium removal agent is sodium sulfide or sodium hydrogen sulfide.
10. The rice cadmium removal method of claim 6 or 8, further comprising the steps of:
precipitating the cadmium-containing colloid from the third cadmium-containing solution subjected to cadmium removal treatment, and adding a flocculating agent for flocculation treatment to obtain a fourth cadmium-containing solution;
and filtering the fourth cadmium-containing solution, and adding the filtrate into the stirring barrel.
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