CN115316594B - Rice cadmium removing method - Google Patents
Rice cadmium removing method Download PDFInfo
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- CN115316594B CN115316594B CN202210084368.5A CN202210084368A CN115316594B CN 115316594 B CN115316594 B CN 115316594B CN 202210084368 A CN202210084368 A CN 202210084368A CN 115316594 B CN115316594 B CN 115316594B
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- cadmium
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- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 title claims abstract description 212
- 229910052793 cadmium Inorganic materials 0.000 title claims abstract description 208
- 235000007164 Oryza sativa Nutrition 0.000 title claims abstract description 129
- 235000009566 rice Nutrition 0.000 title claims abstract description 129
- 238000000034 method Methods 0.000 title claims abstract description 23
- 240000007594 Oryza sativa Species 0.000 title 1
- 241000209094 Oryza Species 0.000 claims abstract description 128
- 238000006243 chemical reaction Methods 0.000 claims abstract description 107
- 238000003756 stirring Methods 0.000 claims abstract description 75
- 239000002253 acid Substances 0.000 claims abstract description 60
- 239000000725 suspension Substances 0.000 claims abstract description 55
- 239000002002 slurry Substances 0.000 claims abstract description 48
- 235000013312 flour Nutrition 0.000 claims abstract description 47
- 238000002386 leaching Methods 0.000 claims abstract description 33
- 238000000926 separation method Methods 0.000 claims abstract description 27
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000000843 powder Substances 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 238000000227 grinding Methods 0.000 claims abstract description 5
- 238000001556 precipitation Methods 0.000 claims description 28
- 239000003795 chemical substances by application Substances 0.000 claims description 15
- 239000002245 particle Substances 0.000 claims description 15
- 239000000706 filtrate Substances 0.000 claims description 14
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical group [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 claims description 12
- 238000001914 filtration Methods 0.000 claims description 11
- 239000000084 colloidal system Substances 0.000 claims description 10
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 10
- HYHCSLBZRBJJCH-UHFFFAOYSA-M sodium hydrosulfide Chemical compound [Na+].[SH-] HYHCSLBZRBJJCH-UHFFFAOYSA-M 0.000 claims description 8
- 229910000030 sodium bicarbonate Inorganic materials 0.000 claims description 6
- 235000017557 sodium bicarbonate Nutrition 0.000 claims description 6
- 229910052979 sodium sulfide Inorganic materials 0.000 claims description 6
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical group [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 claims description 6
- 239000008394 flocculating agent Substances 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
- 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 3
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 description 16
- 239000012065 filter cake Substances 0.000 description 13
- 238000000855 fermentation Methods 0.000 description 10
- 230000004151 fermentation Effects 0.000 description 10
- 239000000047 product Substances 0.000 description 9
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 8
- 239000004310 lactic acid Substances 0.000 description 8
- 235000014655 lactic acid Nutrition 0.000 description 8
- 229920002401 polyacrylamide Polymers 0.000 description 8
- 239000007788 liquid Substances 0.000 description 7
- 238000005406 washing Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000005086 pumping Methods 0.000 description 5
- 239000000872 buffer Substances 0.000 description 4
- 235000013305 food Nutrition 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
- 238000013019 agitation Methods 0.000 description 3
- 229910052980 cadmium sulfide Inorganic materials 0.000 description 3
- 230000003472 neutralizing effect Effects 0.000 description 3
- 238000010298 pulverizing process 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
- 238000005352 clarification Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000006386 neutralization reaction Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000001502 supplementing effect 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
- 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
- 230000008094 contradictory effect Effects 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
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 229940039696 lactobacillus Drugs 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002609 medium Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling 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
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- 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
Landscapes
- 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 cadmium rice to obtain powdery cadmium rice; mixing the cadmium rice in powder form with water to obtain suspension slurry; adding the suspension slurry and the acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution to obtain a cadmium-removed rice flour suspension; the rice flour suspension is delivered to a separation vessel to separate the cadmium-depleted rice flour from the first cadmium-containing solution. The powdered cadmium rice is adopted to realize the stable suspensibility and fluidity of rice protein in an aqueous medium so as to obviously shorten the leaching cadmium-removing treatment time, and the suspension slurry is added into a stirring barrel to improve the reaction efficiency in the stirring barrel and obviously reduce the working space of leaching cadmium-removing. In addition, the suspension slurry and the acid solution are stirred by the stirring barrel, so that the cadmium removing efficiency can be improved, and the method can be applied to rice cadmium removing 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 main food, so that the safety relationship of rice is important. According to 2014 national soil investigation, the cadmium pollution paddy field in China exceeds 28 ten thousand hectares (420 ten thousand acres), and the exceeding rate reaches 7 percent. Since rice itself is extremely absorbable and accumulated in the environment, it is easy to cause the exceeding of cadmium metal in rice (GB/T1354-2018 rice, 0.2 mg/kg). The long-term consumption of cadmium rice can cause pain (namely bone pain). The technology reported in the prior published literature is mostly cadmium removal by acid leaching. The prior art mainly adopts intermittent leaching reaction, the efficiency of leaching cadmium removal is obviously lower, and the method is unfavorable for large-scale and continuous implementation of rice cadmium removal.
Disclosure of Invention
Based on the above, it is necessary to provide a method for removing cadmium from rice, so as to solve the technical problems that the efficiency of removing cadmium from rice in the prior art is obviously low, and the method is not beneficial to large-scale and continuous implementation of the cadmium removal from rice.
The invention provides a method for removing cadmium from rice, which comprises the following steps:
crushing and grinding cadmium rice to obtain powdery cadmium rice;
mixing the cadmium rice in powder form with water to obtain suspension slurry;
adding the suspension slurry and the acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution to obtain a cadmium-removed rice flour suspension;
the rice flour suspension is delivered to a separation vessel to separate the cadmium-depleted rice flour from the first cadmium-containing solution.
Further, the stirring barrels are arranged in a plurality, the stirring barrels are sequentially communicated, and the suspension slurry and the acid solution are sequentially stirred in the stirring barrels so as to obtain cadmium-removed rice flour suspension.
Further, the pH value of the suspended slurry and the acid solution in the stirring barrel is 0.5-2.
Further, the step of delivering the rice flour suspension to a separation vessel to separate the cadmium-depleted rice flour from the first cadmium-containing solution further comprises:
adding an acid solution into the first cadmium-containing solution, and carrying out 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, the step of 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 cadmium concentration of the second cadmium-containing solution is greater than 1mg/L, further comprises:
adding the powdery cadmium rice into the second cadmium-containing solution to enable the pH value of the second cadmium-containing solution to be more than 3, so as to obtain a third cadmium-containing solution.
Further, the step of adding the cadmium rice in powder form to the second cadmium-containing solution so that the pH value of the second cadmium-containing solution is greater than 3, and obtaining a third cadmium-containing solution further comprises:
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 so that the pH value of the second cadmium-containing solution is greater than 3, and obtaining 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 method for cadmium removal of rice further comprises the following steps:
the third cadmium-containing solution subjected to precipitation and cadmium removal treatment is subjected to flocculation treatment by adding a flocculating agent after cadmium-containing colloid is precipitated, so as 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, which comprises the steps of crushing and grinding cadmium rice to obtain powdery cadmium rice, and mixing the powdery cadmium rice with water to obtain suspension slurry. The powdered cadmium rice is adopted to realize the stable suspensibility and fluidity of rice protein in an aqueous medium so as to obviously shorten the leaching cadmium-removing treatment time, and the suspension slurry is added into a stirring barrel to improve the reaction efficiency in the stirring barrel and obviously reduce the working space of leaching cadmium-removing. In addition, the suspension slurry and the acid solution are stirred by the stirring barrel, so that the cadmium removing efficiency can be improved, and the method can be applied to the cadmium removing of rice 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 that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to the structures shown in these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method for cadmium removal from rice in accordance with an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a first reaction tank, a second reaction tank and a third reaction tank according to an embodiment of the present invention;
FIG. 3 shows the Cd concentration of 1mg/L in the examples 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 the Cd concentration of 1mg/L in the examples of the present invention 2+ Basic thermodynamic equilibrium diagram of cadmium removal by adding sodium sulfide or sodium hydrogen sulfide precipitate into the solution.
The main components are as follows:
100. a first reaction tank; 110 a first agitation zone; 200. a second reaction tank; 210. a second agitation area; 300. a third reaction tank; 310. a third agitation area; 400. and a flow guiding pipe.
The achievement of the objects, functional features and advantages of the present invention will be further described with reference to the accompanying drawings, in conjunction with the embodiments.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that all directional indicators (such as up, down, left, right, front, and rear … …) in the embodiments of the present invention are merely used to explain the relative positional relationship, movement, etc. between the components in a particular posture (as shown in the drawings), and if the particular posture is changed, the directional indicator is changed accordingly.
Furthermore, the description of "first," "second," etc. in this disclosure is for descriptive purposes only and is not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In addition, "and/or" throughout this document includes three schemes, taking a and/or B as an example, including a technical scheme, a technical scheme B, and a technical scheme that both a and B satisfy; in addition, the technical solutions of the embodiments may be combined with each other, but it is necessary to base that the technical solutions can be realized by those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent and not within the scope of protection claimed in the present invention.
As shown in fig. 1, in some embodiments, a method of cadmium removing rice comprises the steps of:
s100, crushing and grinding the cadmium rice to obtain powdery cadmium rice.
S200, mixing powdered cadmium rice and water to obtain suspension slurry.
And 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 into a separation container to separate the cadmium-removed rice flour from the first cadmium-containing solution.
The powdered cadmium rice is adopted to realize the stable suspensibility and fluidity of rice protein in an aqueous medium so as to obviously shorten the leaching cadmium-removing treatment time, and the suspension slurry is added into a stirring barrel to improve the reaction efficiency in the stirring barrel and obviously reduce the working space of leaching cadmium-removing. In addition, the suspension slurry and the acid solution are stirred by the stirring barrel, so that the cadmium removing efficiency can be improved, and the method can be applied to rice cadmium removing in a large scale.
Specifically, the acid solution is food grade hydrochloric acid, preferably lactic acid. The lactic acid can be purchased ready-made lactic acid or lactic acid generated during lactobacillus fermentation, and the cadmium-free rice flour can not be polluted after the cadmium-free rice flour is subjected to acid leaching treatment by food-grade hydrochloric acid, so that the rice flour can be eaten with ease.
More specifically, the rice polluted by cadmium is crushed into rice bran, chaff 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 regulating to obtain uniform suspension slurry. The powdered cadmium rice is favorable for fully suspending, flowing and rapidly leaching the cadmium in the water medium.
Further, the stirring barrels are arranged in a plurality, the stirring barrels are communicated in sequence, and the suspension slurry and the acid solution are stirred in the stirring barrels in sequence to obtain the cadmium-removed rice flour suspension. Further, the pH value of the suspended slurry and the acid solution in the stirring barrel is 0.5-2.
Specifically, the plurality of stirring tanks can be arranged into a multi-stage full mixed flow kettle type reactor, so that the suspension slurry and the acid solution are naturally leached in cascade in the plurality of stirring tanks, and the cadmium removal efficiency is improved. More specifically, the plurality of stirring 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 flow guide pipe 400. In actual operation, the number of reaction tanks can be increased or decreased according to the requirements of specific situations. Specifically, the materials of the first reaction tank 100, the second reaction tank 200, and the third reaction tank 300 may be, but not limited to, plastic, stainless steel, cement, wood, etc. More specifically, the first, second and third reaction tanks 100, 200 and 300 may be square or round tanks. The suspension slurry is conveyed to the first reaction tank 100 by means of pumping or an overhead tank, 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 first stirring area 110 stirs the suspension slurry. 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 to 30 minutes, 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 continuous leaching long-time residence tank, the bottom of the second reaction tank 200 is provided with a second stirring zone 210, the second stirring zone 210 stirs 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 flow guide pipe 400.
The third reaction tank 300 is a clarification separation tank, a third stirring area 310 is arranged at the bottom of the third reaction tank 300, and the third stirring area 310 stirs 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. By stirring the first reaction tank 100, the second reaction tank 200 and the third reaction tank 300, cadmium can be rapidly and efficiently removed to obtain a cadmium-removed rice flour suspension. 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 pulp at each level is realized, and the leached rice pulp is conveyed to a stirring area of the next reaction tank through the flow guide pipe 400, so that the rice flour particles can be fully cadmium-removed and reach the standard in the holding time of the rice flour particles in each level of reaction tanks.
Further, S400 delivers 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 vessel is divided into 2-4 relatively isolated areas by a baffle plate, and an inclined plate sedimentation area is constructed to avoid turbulence fluctuation caused by the cadmium-removed rice flour suspension, so that rice flour particles can be naturally settled, precipitated, concentrated and piled at the bottom of the separation vessel conveniently, the cadmium-removed rice flour is separated from the first cadmium-containing solution, the cadmium-removed rice flour is pumped 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. After the rice flour filter cake is washed in advance, the rice flour filter cake is conveyed to a fermentation tank for fermentation treatment to produce rice flour products.
In some embodiments, the step of S400 delivering 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 carrying out 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 washing water of the first cadmium-containing solution and the washing filter cake is pumped into a buffer tank, and the washing water is used for acid leaching and cadmium-removing working procedure after acid matching. 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, S500 adds acid solution into the first cadmium-containing solution, carries out acid leaching treatment on the cadmium-containing solution to obtain a second cadmium-containing solution, and the step of the second cadmium-containing solution with cadmium concentration larger than 1mg/L further comprises:
s600, adding powdery cadmium rice into the second cadmium-containing solution to enable the pH value of the second cadmium-containing solution to be larger than 3, obtaining a third cadmium-containing solution, centrifuging or press-filtering the third cadmium-containing solution, and returning rice flour particles into the stirring barrel. The powdery cadmium rice has the effect of pre-neutralization, can save the introduction amount of alkaline reagent, precipitation cadmium removing agent and sodium ions, remarkably improves the utilization efficiency of the precipitation cadmium removing agent, reduces the consumption of the alkaline reagent and the precipitation cadmium removing agent, and saves the production cost.
Further, the step S600 of adding powdered cadmium rice to the second cadmium-containing solution to make the pH value of the second cadmium-containing solution greater than 3, and the step of obtaining the 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 performing 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, the step S600 of adding powdered cadmium rice to the second cadmium-containing solution to make the pH value of the second cadmium-containing solution greater than 3, and the step of obtaining the third cadmium-containing solution further comprises:
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. Directly adding 1-2 times of stoichiometric ratio of sodium sulfide or sodium hydrogen sulfide into the third cadmium-containing solution.
Further, the method for removing cadmium from rice further comprises the following steps:
s910, precipitating the third cadmium-containing solution subjected to cadmium removal treatment to precipitate cadmium-containing colloid, and then 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 then a cadmium carbonate primary product or a cadmium sulfide primary product is obtained after recovery. And recycling the precipitated cadmium-containing colloid 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 leaching solution after multiple rounds of acid leaching treatment and precipitation, and because the accumulated concentration of soluble proteins is high, a fermentation method can be adopted to decompose proteins to obtain lactic acid solution, and after clarification, the acid leaching process is continued.
More specifically, the flocculant is a food grade PAM (polyacrylamide) flocculant.
As shown in FIG. 3, cd is added from 1mg/L 2+ Basic thermodynamic equilibrium diagram of cadmium removal by adding baking soda or soda precipitation to the solution.
As shown in FIG. 4, cd from 1mg/L 2+ The solution is added with a basic thermodynamic equilibrium diagram of cadmium removal by precipitation of sodium sulfide or sodium hydrogen sulfide, and the total cadmium ion concentration is=1 mg/L and the total sulfur ion concentration is=0.0001 mol/L.
The technical scheme of the invention is specifically described by the following examples.
Example 1
Taking out rice contaminated by cadmium metal, removing shell, crushing, sorting to obtain crushed rice with particle size of about 1mm, further pulverizing into powder particles with particle size of less than 0.5mm, and confirming cadmium content. 1000kg of powdered cadmium rice was placed in a stirring tank, 2000 liters of water was added and pumped at a rate of 50 liters/min to a first stirring zone at the bottom of a first reaction tank having a working space of 1m 3 And food-grade hydrochloric acid is prepared to adjust the pH value to about 1. The suspended slurry and the acid solution of the first reaction tank naturally overflow and are introduced into a second stirring area of the second reaction tank through the flow guide pipe, and the working space of the second reaction tank is 2m 3 . The suspension slurry of the feed liquid in the second reaction tank and the acid solution naturally overflow and are introduced into a third stirring area of a third reaction tank through a flow guide pipe, and the working space of the third reaction tank is 3m 3 . The suspended slurry and the acid solution in the third reaction tank material naturally overflow and are introduced into the separation container through the flow guide pipe. The working space of the separation vessel was 30m 3 The separation vessel was equipped with a sloping plate with a width of 2m and a length of 8m. The inclined plate is arranged at the lower 0.5m position of the transfusion port of the separation container. The inclined plate has a horizontal inclination angle of 65 deg.. The rice flour particles deposited at the bottom of the separation container are pumped out by a diaphragm pump every 2 hours, centrifugally separated out, sprayed with water to wash the residual liquid which is adhered, and then sent to a fermentation tank to prepare rice flour products for sale.
Mixing the settled supernatant and the centrifugal filtrate, conveying to a buffer tank, adding acid to form pH of 1, and continuously leaching in a first reaction tank. Pumping the solution after leaching for 10 times into a stirring tank, adding a new batch of powdered cadmium rice, stirring and neutralizing to reach the pH value of 5, filtering, returning the rice flour filter cake to the first reaction tank for continuous leaching, and adding sodium bicarbonate and sodium carbonate in a mass ratio of 10:1, regulating the pH value of the solution to 8.5, continuously stirring for 20 minutes, adding 0.01% of food-grade PAM (polyacrylamide) flocculant, continuously stirring for 1 minute, and 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 after being recycled for 30 times, the filtrate can enter a special fermentation tank for fermenting and decomposing rice protein therein, and the clear liquid is returned to the first reaction tank for continuous acid supplementing for leaching.
Example 2
Taking out rice contaminated by cadmium metal, removing shell, crushing, sorting to obtain crushed rice with particle size of about 1mm, further pulverizing into powder particles with particle size of less than 0.5mm, and confirming cadmium content. 1000kg of powdered cadmium rice was placed in a stirring tank, 2000 liters of water was added and pumped at a rate of 50 liters/min to a first stirring zone at the bottom of the first reaction tank. 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. The suspended slurry and the acid solution of the first reaction tank naturally overflow to the second reaction tank. The working space of the second reaction tank is 2m 3 . The suspended slurry and the acid solution of the second reaction tank naturally overflow to the third reaction tank. The working space of the third reaction tank is 3m 3 . The suspended slurry and the acid solution of the third reaction tank naturally overflow to the separation vessel. The working space of the separation vessel was 30m 3 . The separation vessel was equipped with a sloping plate with a width of 2m and a length of 8m. The inclined plate is arranged at the lower 0.5m position of the transfusion port of the separation container. The inclined plate has a horizontal inclination angle of 65 deg.. The rice flour particles deposited at the bottom of the separation container are pumped out by a diaphragm pump every 2 hours, centrifugally separated out, sprayed with water to wash the residual liquid which is adhered, and then sent to a fermentation tank to prepare rice flour products for sale.
Mixing the settled supernatant and the centrifugal filtrate, conveying to a buffer tank, adding acid to form pH of 1, and adding the mixture into a first reaction tank for continuous leaching. Pumping the leached solution for 10 times into a special stirring tank, adding a new batch of powdered cadmium rice, stirring and neutralizing to enable the pH value to be 2.5, filtering, returning the rice flour filter cake to the first reaction tank to prepare for continuous leaching, adding sodium hydrogen sulfide with the same cadmium total content precipitation stoichiometric ratio coefficient of 1.2 into the filtrate, continuously stirring for 20 minutes, adding a food-grade PAM (polyacrylamide) flocculant with the concentration of 0.005%, 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 on 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 fermenting and decomposing rice protein therein, and the clear liquid is returned to the first reaction tank for continuous acid supplementing for leaching.
Example 3
Taking out rice contaminated by cadmium metal, removing shell, crushing, sorting to obtain crushed rice with particle size of about 1mm, further pulverizing into powder with cadmium content of less than 0.5mm, and confirming cadmium content. 1000kg of powdered cadmium rice was placed in a stirring tank, 2000 liters of water was added and pumped at a rate of 50 liters/min to a first stirring zone at the bottom of the first reaction tank. 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. The suspended slurry and the acid solution of the first reaction tank naturally overflow into the second stirring zone of the second reaction tank. The working space of the second reaction tank is 2m 3 . The suspended slurry and the acid solution in the second reaction tank naturally overflow to the third stirring zone of the third reaction tank. The working space of the third reaction tank is 3m 3 . The suspension slurry and the acid solution of the third reaction tank naturally overflow into the separation vessel. The working space of the separation vessel was 30m 3 . The separation vessel was equipped with a sloping plate having a width of 2m and a length of 8m. The inclined plate is arranged at the lower 0.5m position of the transfusion port of the separation container. The inclined plate has a horizontal inclination angle of 75 degrees. The rice flour particles deposited at the bottom of the separation container are pumped out by a diaphragm pump every 2 hours, centrifugally separated out, sprayed with water to wash the residual liquid which is adhered, and then sent to a fermentation tank to prepare rice flour products for sale.
Mixing the settled supernatant and the centrifugal filtrate, delivering to a buffer tank, adding lactic acid to the pH value of 1, and adding the mixture into a first reaction tank for continuous leaching. Pumping the leached solution for 10 times into a special stirring tank, adding a new batch of powdered cadmium rice, stirring and neutralizing to enable the pH value to be 2.5, filtering, returning the rice flour filter cake to the first reaction tank to prepare for continuous leaching, adding sodium hydrogen sulfide with the same cadmium total content precipitation stoichiometric ratio coefficient of 1.2 into the filtrate, continuously stirring for 20 minutes, adding a food grade PAM (polyacrylamide) flocculant with the concentration of 0.01%, 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 on 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 fermenting and decomposing rice protein therein, and the acidic clear liquid is returned to the first reaction tank for continuous replenishment of lactic acid for leaching.
The foregoing description is only of the preferred embodiments of the present invention and is not intended to limit the scope of the invention, and all equivalent structural changes made by the description of the present invention and the accompanying drawings or direct/indirect application in other related technical fields are included in the scope of the invention.
Specifically, the cadmium removal effect of each example is shown in table 1.
TABLE 1
| Project | 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 |
| Cadmium removal rate | 89.53％ | 85.29％ | 88.30％ |
Claims (4)
1. A method for cadmium removal of rice, which is characterized by comprising the following steps:
crushing and grinding cadmium rice to obtain powdery cadmium rice;
mixing the cadmium rice in powder form with water to obtain suspension slurry;
adding the suspension slurry and the acid solution into a stirring barrel, and stirring the suspension slurry and the acid solution, wherein the pH value of the suspension slurry and the acid solution in the stirring barrel is 0.5-2, so as to obtain a cadmium-removed rice flour suspension;
delivering the rice flour suspension to a separation vessel to separate cadmium-free rice flour from a first cadmium-containing solution;
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;
adding a new batch of 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, centrifuging or press-filtering the third cadmium-containing solution, and returning rice flour particles into a stirring barrel;
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; the first precipitation cadmium removing agent is sodium bicarbonate or sodium carbonate;
the stirring barrels are sequentially communicated, the suspension slurry and the acid solution are sequentially stirred in the stirring barrels to obtain cadmium-removed rice flour suspension, the stirring barrels are respectively provided with a first reaction tank, a second reaction tank, a third reaction tank and a guide pipe, the first reaction tank, the second reaction tank and the third reaction tank are sequentially communicated through the guide pipe, and the first reaction tank, the second reaction tank and the third reaction tank are connected in a stepped cascade mode;
the automatic acid adding device is arranged in the first reaction tank, the second reaction tank is a residence tank, a second stirring area is arranged at the bottom of the second reaction tank and used for stirring suspension slurry and acid solution flowing into the second reaction tank from the first reaction tank, the third reaction tank is a separation tank, a third stirring area is arranged at the bottom of the third reaction tank and used for stirring suspension slurry and acid solution flowing into the third reaction tank from the second reaction tank.
2. The method for cadmium removal from rice according to claim 1,
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.
3. The method of cadmium removing rice of claim 2 wherein said second precipitated cadmium removing agent is sodium sulfide or sodium hydrogen sulfide.
4. The method for cadmium removal from rice according to claim 2 further comprising the steps of:
adding a flocculating agent into the third cadmium-containing solution subjected to the precipitation cadmium removal treatment 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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