Leaching kinetics of cadmium from rice grain by dilute hydrochloric acid

doi:10.21203/rs.3.rs-1890647/v1

PDF

Research Article

Leaching kinetics of cadmium from rice grain by dilute hydrochloric acid

https://doi.org/10.21203/rs.3.rs-1890647/v1

This work is licensed under a CC BY 4.0 License

Version 1

posted 29 Jul, 2022

You are reading this latest preprint version

Cadmium-contaminated rice grain was treated by leaching in dilute hydrochloric acid under different conditions, and it was confirmed that cadmium could be effectively extracted to safe standard level of below 0.2mg/kg accompanying with dissolution loss of rice protein at 5 ~ 15% mass. Both the extraction of cadmium and the rice dissolution loss were strongly pH-dependent process. The cadmium leaching kinetic equation was investigated based on the typical core-shrinking model, with apparent activated energy at 16.67KJ/mol suggesting that the intraparticle diffusion of cadmium ion or proton inside of rice grain was the limited step controlling the whole leaching process. Grain size and pH were found the main parameters to affect cadmium extraction efficiency, and pH 1–2 was recommended for rice grain leaching. The acidic solution could be repeatedly used for cadmium extraction by adding an aliquot of HCl before each leaching operation, favorable for the enormous reduction of water consumption.

Rice grain

cadmium

leaching kinetics model

HCl

protein dissolution loss

Rice was the most widely consumed cereal grain on earth and was one of the staple foods for over half of the world’s population (Hu et al. 2016; Jallad 2015). Therefore, food security was very important to human life and health (Wang et al. 2018).

It had been reported that due to the rapid development of modern industry, the uncontrolled discharge of various pollutants, the indiscriminate application and abuse of chemical fertilizers and pesticides had led to the pollution of water and soil, which made the rice harvested in many countries containing excessive heavy metals such as cadmium, lead and arsenic. For example, in the 1960s, in the Jinzu river basin (Japan), where Itai-itai disease was endemic due to high Cd intake, and rice consumption accounted for 30–40% of the total Cd intake (Ikeda et al. 2004; Qin et al. 2020). In Pakistan, the average metal concentration of cadmium in grains (mg/kg) fluctuated between 2.70 and 9.80 (Tariq et al. 2021). The average Cd concentration in paddy soils of industrial cities in South Korea was 1.98 mg/kg (Cho et al. 2019), in addition, the content of cadmium in rice planted on contaminated soil was 0.1-0.98mg/kg (Ji et al. 2017). Arsenic concentration in Australian rice is 0.29-0.44mg/kg (Rahman et al. 2014). The average arsenic content of American rice is 0.26mg/kg (Shraim 2017; Jorhem et al. 2008). So the toxic metals contaminated rice was not an isolating phenomena, but occurred in many countries in the global world. In Asian countries, rice was a food staple used for daily consumption and provided over 70% of the energy derived from daily food intake (Phuong et al. 1999). Especially in China, paddy rice acted as the staple food of at least two-thirds of China’s population, and also was under the threat of toxic metals contamination due to its preference to accumulate heavy metals than other terrestrial-based foods (Carey et al. 2010; Khan et al. 2014; Huang et al. 2017). The rice produced in some southern provinces also contained cadmium exceeding the safe standard, especially in Hunan province, where the average cadmium content of rice in the whole region reached 0.24mg/kg (Williams et al. 2009; Wang et al. 2018; Zhang et al. 2020; Lei et al. 2015; Ma et al. 2017; Li et al. 2018). Therefore, this was a serious global challenge for the whole mankind.

For the sake of human health and safety, we must take effective measures to solve this problem. Common solutions had been taken including soil treatment, such as in-situ passivation (Gao et al. 2019; Fan et al. 2020; Sun et al. 2016), chemical leaching (Xiao et al. 2019; Feng et al. 2020), page fertilizer barrier method (Liu et al. 2009), phytoremediation (Rizwan et al. 2018; Tauqeer et al. 2016), microbial remediation (Peng et al. 2018; Jitendra et al. 2017). Although great progress had been made in past decades, there was still a lack of an economic, ecofriendly and feasible method to be popularized and applied in a large area. Another practical solution was to remove cadmium from rice grains. There were many reports, such as reduce the content of cadmium in rice grains by physical, chemical and biological methods, including hydrochloric acid and organic acid leaching, surfactant, microbial fermentation and ultrasonic high pressure assisted extraction of cadmium (Feng et al. 2021; Feng et al. 2018; Wu et al. 2016; Meng et al. 2018; Zhai et al. 2018; Luo et al. 2021a, b). Among above methods, extracting of cadmium from rice grain by acidic lixiviants had been confirmed to be quite effective, but no one had ever carried out the quantitative study on the kinetic mechanism of cadmium leaching process, which was not conducive to the popularization and application of this method.

Hence, in present study we would like to explore the leaching kinetics of cadmium from rice grain, and hoped to give a quantitative description of the leaching process, which would help to understand the kinetic characteristics of the cadmium extraction process. So we planned to firstly carry out systematic experimental research on the cadmium extraction process from the rice grain to learn its basic leaching behavior, and then establish the leaching kinetic model for further exploration on the leaching mechanism, so as to provide theoretical guidance for the design and optimization of cadmium removal in the acid leaching process of rice grain.

2.1 Materials and chemicals

Cadmium-containing rice samples were obtained from a local town of Hunan Province, was used as raw material for leaching experiments. Analytical grade hydrochloric acid (HCl) and nitric acid (HNO₃) were purchased from Sinopharm Chemical Reagent Co., Ltd. The deionized water was prepared by a reverse osmosis membrane machine in our lab.

2.2 Experimental details

A 0.5L beaker was used as the leaching vessel and placed in a temperature-controlled water bath. One hundred gram of rice was put in above beaker, and then dilute hydrochloric acid solution was poured into the beaker at a solid-liquid mass ratio of 1:3 typically. Then started by stirring the leaching solution with a mechanical stirrer for 4h. Five milliliter of leaching solution was sampled periodically from the beaker for measuring the cadmium concentration by ICP-MS analysis.

In order to measure the content of total cadmium and residual cadmium in rice grains after leaching, the rice samples were crushed and sieved to below 60 mesh. Accurately weighed 1g of rice flour sample, was put into a 50mL beaker with 20mL 1.5moL/L hydrochloric acid solution, and kept stirring with magnetic force for 8h. After above leaching, the suspension was poured into a 50mL volumetric flask and filled with deionized water to a constant volume, centrifuged and filtered, for measuring the cadmium concentration in the filtrated solution.

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine cadmium in leaching solution samples. The solution for measurement was diluted to the concentration range of the standard solution, within 0-20ug/L, and acidified by adding a quantitative volume of nitric acid to prevent the possible hydrolysis of cadmium to ensure the accuracy of the analysis results. The extraction efficiency of Cd from the rice grain during the leaching process (L) and rice grain dissolution loss ratio (D) was calculated as follows:

L%=C/C₀×100 (1)

D%=(M₀-M)/M₀×100 (2)

where C₀ and C were the cadmium contents in the untreated rice and leached rice, ug/L, respectively. M₀ and M were the grain mass in the untreated and treated rice, g, respectively.

2.3 Characterization

The instruments used for rice grain leaching experiments were listed as follows, including pH meter for laboratory (pHSJ-3F, Shanghai Jingke Co., Ltd, China), electronic balance (AUY220, Shimadzu, Japan), digital display electric agitator (JJ-1A, Jintan ronghua Instrument Manufacturing Co., Ltd, China), drying oven (DHG-9030A, Shanghai Yiheng Scientific Instrument Co., Ltd, China), digital magnetic stirrer with heating (RH D S025, IKA, Germany), high speed centrifuge (HC-3018, Anhui USTC Zonkia Scientific Instruments Co., Ltd, China), SEM (EVO 18, ZEISS, Germany) and ICP-MS (iCAP-RQ, Thermo Scientific, USA).

3.1 SEM

It could be seen that in the SEM photos shown in Fig. 1 that the rice grain had a quite compact and undulating surface for the whole one, while if made a closeup observation it could be found that the inner surface of the rice grain was quite different from the outer one, as illustrated in the rupture place on the rice grain crust in Fig. 1a, there were many small cells filled with a great number of tiny spherical rice protein particles. This photo disclosed the inner structure of rice grain for the first time, and it might give us more inspiration and learning about the leaching behavior about the common rice consumed in our daily lunch. After leaching,it could be f, und that the plane section of the rice grain would be left with the wound by the acid leaching, which suggested that some part of the rice grain would be lost by dissolution in the acidic solution. Certainly, it was anticipated in this study that only the cadmium was extracted from the rice grain but not the dissolution loss of rice protein, while this fact told us that it was not possible to realize this aim. There must be a critical point for balance of the cadmium removal efficiency and the dissolution loss of the rice grain.

3.2 Effect of acid concentration

It could be found that the extraction efficiency of cadmium from the rice grain was a strongly pH-dependent process, as shown in Fig. 2a, at pH 1, the cadmium extraction percentage (%) increased monotonously to reach around 70% after 4h leaching for the whole grain. At pH 2, the corresponding extraction percentage would decrease to 60%. It was confirmed that at pH 6 there was almost no extraction for cadmium, which could be concluded that the common water washing in our everyday cooking had not any removal efficiency and was not able to remove cadmium from the rice grain. By calculation, it could be found that after leaching at pH 1 ~ 2 for about 4h, the residual cadmium content in the whole rice grain could decrease below 0.2mg/kg, meeting the food quality standard of China. It was also found that during the cadmium extraction process, the rice protein would dissolve into the aqueous solution with 7–8% mass loss at pH 1–2, as demonstrated in Fig. 3a, and only about 1% mass loss occurred at pH 6. Hence, it could be seen that solution pH would affect the cadmium extraction efficiency and dissolution loss of the rice grain in the leaching process, or it could be concluded that the extraction of cadmium from rice grain and the rice dissolution process were both the strongly pH-dependent process.

3.3 Effect of solid/liquid ratio

As shown in Fig. 2b and Fig. 3b, at the S/L ratio of 1/3 ~ 1/4 g/ml, the cadmium extraction efficiency and dissolution loss of rice grain both increased simultaneously to 70–80% and 8.5% mass, which appeared that at higher S/L ratio, these two index did not vary again. While at the lower S/L ratio, they reached 45% cadmium removal and 4% mass dissolution loss respectively. It could be understanded that the more acidic lixiviant was provided for leaching, the more cadmium would be extracted according to the. Therefore, S/L at 1/3 g/ml was recommended for practical leaching.

3.4 Effect of temperature

Figure 2c and Fig. 3c indicated that temperature would promote the cadmium removal and rice protein dissolution loss, and it could be found that the Cd% removal and rice dissolution loss would reach 70%, 77%, 85%, and 8%, 9.5%, 10% at 298K, 308K and 318K respectively. It was clear that temperature would lead to the faster diffusion of protons through the rice grain, intensifying the leaching kinetic rate coefficient. Considering the comprehensive effect, the leaching of rice grain at room temperature was recommended for following cadmium extraction experiments.

3.5 Effect of stirring rate

Figure 2d and Fig. 3d showed that stirring rate had positive promotion effect on the cadmium extraction and dissolution loss of the rice grain during the leaching process. While the effect was not so large as that of pH or S/L ratio, meant the suitable stirring rate could be set at 350 rpm for rice grain leaching.

3.6 Effect of size of rice grain

Figure 2e and Fig. 3e suggested that the long axis grain size had remarkable promotion of the cadmium extraction and dissolution rate, which had much more effect on the leaching results. Obviously, it could be understood clearly that the smaller grain size would shorten the diffusion distance of proton or cadmium ions, and also exhibited larger specific surface area for exposure to the acidic solution. Though the crack of the rice grain would promote the leaching efficiency, while the rice dissolution loss would also increase correspondingly as shown in the Fig. 3e. By overall evaluation, the rice grain with a half size appeared better for cadmium extraction with the low dissolution loss.

To better learn the cadmium extraction efficiency in the acidic solutions, the related leaching results of the rice grain in the acids were collected and listed in Table 1, and it could be found that the acidic leaching was quite effective to extract cadmium from the rice grain, though the acids used for leaching was quite different, suggesting that the dominant component for cadmium extraction was protons, but not the ligands. As compared in Table 1, the pH as well as other conditions set in present study was suitable for cadmium extraction effectively.

Table 1

Comparison of cadmium extraction efficiency in acids in open reported literature.
No.	Initial Cd content (mg/kg)	Leaching conditions	Extraction efficiency (%)	Residual Cd content(optimal) (mg/kg)	Reference
1	0.27 ~ 0.92	Hydrochloric acid, 0.06M-0.18M	45 ~ 85	0.14	Feng et al., 2021
2	0.22 ~ 0.96	Citric acid, 0.02-0.08M	80 ~ 94	0.06	Wu et al., 2016
3	0.26	Acetic acid, pH = 3, ultrasound assisted extraction	66 ~ 93	0.02	Luo et al., 2021a
4	0.18 ~ 0.26	Acetic acid, pH = 5.5, high-pressure extraction	43 ~ 82	0.05	Luo et al., 2021b
5	1.02	Hydrochloric acid, pH = 1–2	60 ~ 92	0.08	This study

3.7 Reusability of leaching solution

Figure 2f showed that the same batch of HCl solution was repeatedly used for rice leaching, but adjusting pH to 1 by adding an aliquot of acid before next leaching operation, and it could be seen that the cadmium concentration in the acid solution increased monotonously at the average rate of around 80% for each leaching. Obviously, each leaching would increase the dissoluble protein concentration in the acidic solution as well as the viscosity of the solution, but it appeared no negative effect on the extraction efficiency of cadmium from the rice grain, further confirmed that the protons were the principal component for extraction of cadmium. Obviously, the effectiveness of reusability of the acidic solution would help to save the lixiviant and reduce the water consumption in the practical leaching process enormously, leading to the design of effective, ecofriendly and economical technology for cadmium extraction from rice grain.

3.8 Leaching kinetic model

Based on aforementioned results under different leaching conditions, it could de deduced that the cadmium extraction process from rice grain might occur according to the following reaction:

Rice-Cd + 2H⁺ = Rice-2H⁺ + Cd²⁺_(aq) (3)

Cd²⁺_(aq) + Cl⁻ = CdCl⁺_(aq) (4)

By thermodynamic calculation of the Cd (II)-Cl⁻-H²O solution system on the basis of the equilibrium reactions, as shown in Fig. 4b, it could be found that at pH 1–2, the cadmium existed in the dominant species of Cd²⁺ and CdCl⁺ in the aqueous solution, and they both played the exchange role with protons during the leaching process.

Above study suggested that the extraction of cadmium was actually a cation exchange process, as shown in reaction (3) and (4), and the diffusion rate of cadmium or proton in the solution bulk, liquid film locating in the interface of the grain-solution, and intraparticle of rice grain might become the limiting or bottleneck step for the whole leaching process. On the basis of the traditional leaching models for mineral ores in hydrometallurgical process (Li 2002), the related study was carried out to evaluate the leaching process by a quantitative way so that the leaching mechanism and fundamental characteristic parameters could be explored for better understanding the leaching process.

Fig. 5a and Fig. 5b showed the fitting plots based on the above leaching experimental results as shown in Fig. 2c, and the positive correlation of diffusion rate of cadmium vs 1/R² in Fig. 5c, it confirmed that the intraparticle diffusion model could describe the cadmium extraction rate better. So on the basis of above results, the apparent activated energy value of the cadmium extraction process could be estimated to be 16.67 KJ/mol,as shown Fig., d, which suggested that the leaching process was controlled by the diffusion of cadmium or protons in the rice grain part. Hence it could be concluded that the most effective means to promote the cadmium extraction process was by crack rice grain into smaller size, for more convenient diffusion of protons inwards the grain and more specific surface area for exposure to the acidic solution.

Dilute HCl was used to extract cadmium from the rice, and the effect of pH, temperature, rice size, stirring intensity, solid/liquid ratio and grain size was investigated systematically. It was found the cadmium could be effectively extracted by HCl at pH 1–2, and higher the HCl concentration and smaller grain size would promote the leaching rate significantly. While the dissolution loss of the rice protein was mainly affected by grain size and stirring rate. The leaching kinetic model was established to determine the apparent activated energy of the leaching process to be 16.67KJ/mol, suggesting the cadmium extraction from the rice grain was actually controlled by the intraparticle diffusion step of cadmium or protons inside the rice grain.

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Availability of data and materials

Not applicable

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

CRediT authorship contribution statement

Liu Feng: Methodology, Validation, Data Curation, Writing - Original Draft, Writing - Review & Editing. Huang Kai: Conceptualization, Methodology, Writing - Original Draft, Writing - Review & Editing, Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The authors want to show their sincere thanks to Mr. He for his help in ICP/MS analysis

Carey AM, Scheckel KG, Lombi E, Newville M, Choi Y, Norton GJ, et al (2010) Grain unloading of arsenic species in rice. Plant Physiology 152(1): 309–319. http://doi.org/10.1104/pp.109.146126.
Cho IG, Park MK, Cho HK, Jeon JW, Lee SE, Choi SD (2019) Characteristics of metal contamination in paddy soils from three industrial cities in South Korea. Environmental Geochemistry and Health 41: 1895–1907. https://doi.org/10.1007/s10653-019-00246-1.
Feng W, Wang T, Dong T, Xu P, Zhang T, Luo X, et al (2018) Removal of cadmium from rice proteins by soaking with hydrochloric acid or ethylene diamine tetraacetic disodium solutions. Journal of Cereal Science 85: 35–40. https://doi.org/10.1016/j.jcs.2018.11.008.
Feng W, Zhang S, Zhong Q, Wang G, Pan X, Xu X, et al (2020) Soil washing remediation of heavy metal from contaminated soil with EDTMP and PAA: Properties, optimization, and risk assessment. Journal of Hazardous Materials 381: 120997. http://dpoi.org/10.1016/j.jhazmat.2019.120997.
Fan J, Cai C, Chi H, Reid BJ, Coulon F, Zhang Y, Hou Y (2020) Remediation of cadmium and lead polluted soil using thiol-modified biochar. Journal of Hazardous Materials 388: 122037. http://doi.org/10.1016/j.jhazmat.2020.122037.
Feng W, Fan D, Li K, Wang T, Zhang H, Zhou X, et al (2021) Removal of cadmium from rice grains by acid soaking and quality evaluation of decontaminated rice. Food Chemistry 371: 131099. https://doi.org/10.1016/j.foodchem.2021.131099.
Gao X, Peng Y, Zhou Y, Adeel M, Chen Q (2019) Effects of magnesium ferrite biochar on the cadmium passivation in acidic soil and bioavailability for packoi (Brassica chinensis L.). Journal of Environmental Management 251: 109610. https://doi.org/10.1016/j.jenvman.2019.109610.
Hu Y, Cheng H, Tao S (2016) The Challenges and Solutions for Cadmium-contaminated Rice in China: A Critical Review. Environment international 92–93: 515–532. https://doi.org/10.1016/j.envint.2016.04.042.
Huang B, Xin J, Dai H, Zhou W (2017) Effects of interaction between cadmium (Cd) and selenium (Se) on grain yield and cd and se accumulation in a hybrid rice (Oryza sativa) system. Journal of Agricultural & Food Chemistry 65(43): 9537–9546. https://doi.org/10.1021/acs.jafc.7b03316.
Ikeda M, Ezaki T, Tsukahara T, Moriguchi J (2004) Dietary cadmium intake in polluted and non-polluted areas in Japan in the past and in the present. International Archives of Occupational & Environmental Health 77(4): 227–234. https://doi.org/10.1007/s00420-003-0499-5.
Jorhem L, Astrand C, Sundstroem B, Baxter M, Stokes P, Lewis J, Petersson Grawe K (2008) Elements in rice from the Swedish market: 1. cadmium, lead and arsenic (total and inorganic). Food Additives & Contaminants 25(3): 284–292. https://doi.org/10.1080/02652030701474219.
Jallad KN (2015) Heavy metal exposure from ingesting rice and its related potential hazardous health risks to humans. Environmental Science and Pollution Research 22(20): 15449–15458. https://doi.org/10.1007/s11356-015-4753-7.
Jitendra M, Rachna S, Arora NK (2017) Alleviation of heavy metal stress in plants and remediation of soil by rhizosphere microorganisms. Front Microbiol 8: 1706. https://doi.org/10.3389/fmicb.2017.01706.
Ji CK, Nejad ZD, Jung MC (2017) Arsenic and heavy metals in paddy soil and polished rice contaminated by mining activities in Korea. Catena 148: 92–100. https://doi.org/10.1016/j.catena.2016.01.005.
Khan S, Reid BJ, Li G, Zhu YG (2014) Application of biochar to soil reduces cancer risk via rice consumption: a case study in Miaoqian village, longyan, China. Environment International 68: 154–161. http://doi.org/10.1016/j.envint.2014.03.017.
Li H G (2002) Hydrometallurgy (1th ed). Leaching (Chap. 2).
Liu C, Li F, Luo C, Liu X, Wang S, Liu T, Li X (2009) Foliar application of two silica sols reduced cadmium accumulation in rice grains. Journal of Hazardous Materials 161(2–3): 1466–1472. https://doi.org/10.1016/j.jhazmat.2008.04.116.
Lei M, Tie BQ, Song ZG, Liao BH, Lepo GE, Huang YZ (2015) Heavy metal pollution and potential health risk assessment of white rice around mine areas in Hunan province, China. Food Security 7: 45–54. https://doi.org/10.1007/s12571-014-0414-9.
Li Y, Fang F, Wu M, Kuang Y, Wu H (2018) Heavy metal contamination and health risk assessment in soil-rice system near Xinqiao mine in Tongling city, Anhui province, China. Human and ecological risk assessment 24(3–4): 743–753. https://doi.org/10.1080/10807039.2017.1398631.
Luo Z, Duan H, Yang H, Zhang W, Ramaswamy H, Chao W (2021a) Ultrasound assisted extraction of cadmium for decontamination of rice and its influence on structure/texture of cooked rice. Journal of Cereal Science 97: 103142. https://doi.org/10.1016/j.jcs.2020.103142.
Luo Z, Duan H, Yang Y, Zhang W, Ramaswamy H, Bai W, Wang C (2021b) High pressure assisted extraction for cadmium decontamination of long rice grain. Food Control 125: 107987. https://doi.org/10.1016/j.foodcont.2021.107987.
Ma L, Wang L, Tang J, Yang Z (2017) Arsenic speciation and heavy metal distribution in polished rice grown in Guangdong province, southern China. Food Chemistry 233: 110–116. https://doi.org/10.1016/j.foodchem.2017.04.097.
Meng Q, Peng B, Shen C (2018) Synthesis of F127/PAA hydrogels for removal of heavy metal ions from organic wastewater. Colloids and Surfaces B: Biointerfaces 167: 176–182. https://doi.org/10.1016/j.colsurfb.2018.04.024.
Phuong TD, Chuong PV, Khiem DT, Kokot S (1999) Elemental content of Vietnamese rice. Part 1. sampling, analysis and comparison with previous studies. The Analyst 124: 553–560. http://doi.org/10.1039/a808796b.
Peng W, Li X, Song J, Jiang W, Liu Y, Fan W (2018). Bioremediation of cadmium- and zinc-contaminated soil using Rhodobacter sphaeroides. Chemosphere 197: 33–41. https://doi.org/10.1016/j.chemosphere.2018.01.017.
Qin S, Liu H, Nie Z, Rengel Z, Gao W, Li C, Zhao p (2020) Toxicity of cadmium and its competition with mineral nutrients for uptake by plants: a review. Pedosphere 30(2): 168–180. http://doi.org/10.1016/s1002-0160(20)60002-9.
Rahman MA, Rahman MM, Reichman SM, Lim RP, Naidu R (2014) Arsenic speciation in Australian-grown and imported rice on sale in Australia: implications for human health risk. Journal of Agricultural and Food Chemistry 62(25): 6016–24. http://doi.org/10.1021/jf501077w.
Rizwan M, Ali S, Rehman M, Rinklebe J, Tsang D, Bashir A, et al (2018) Cadmium phytoremediation potential of brassica crop species: a review. Science of the Total Environment 631–632: 1175–1191. https://doi.org/10.1016/j.scitotenv.2018.03.104.
Sun Y, Sun G, Xu Y, Liu W, Liang X, Wang L (2016) Evaluation of the effectiveness of sepiolite, bentonite, and phosphate amendments on the stabilization remediation of cadmium-contaminated soils. Journal of Environmental Management 166: 204–210. https://doi.org/10.1016/j.jenvman.2015.10.017.
Shraim AM (2017) Rice is a potential dietary source of not only arsenic but also other toxic elements like lead and chromium. Arabian Journal of Chemistry 10: S3434-S3443. https://doi.org/10.1016/j.arabjc.2014.02.004.
Tauqeer HM, Ali S, Rizwan M, Ali Q, Saeed R, Iftikhar U, et al (2016) Phytoremediation of heavy metals by alternanthera bettzickiana: growth and physiological response. Ecotoxicology & Environmental Safety 126: 138–146. https://doi.org/10.1016/j.ecoenv.2015.12.031.
Tariq F, Wang X, Saleem MH, Khan ZI, Ali S (2021) Risk assessment of heavy metals in basmati rice: implications for public health. Sustainability 13(15): 1–13. https://doi.org/10.3390/su13158513.
Williams PN, Lei M, Sun G, Huang Q, Ying LU, Deacon C, et al (2009) Occurrence and partitioning of cadmium, arsenic and lead in mine impacted paddy rice: Hunan, China. Environmental Science and Technology 43(3): 637–642. https://doi.org/10.1021/es802412r.
Wu Y, He R, Wang Z, Yuan J, Xing C, Wang L, Ju X (2016) A safe, efficient and simple technique for the removal of cadmium from brown rice flour with citric acid and analyzed by inductively coupled plasma mass spectrometry. Analytical Methods 8(33): 6313–6322. https://doi.org/10.1039/C6AY01650B.
Wang L, Ma L, Yang Z (2018) Spatial variation and risk assessment of heavy metals in paddy rice from Hunan province, southern China. International Journal of Environmental Science & Technology 15: 1561–1572. https://doi.org/10.1007/s13762-017-1504-y.
Xiao R, Ali A, Wang P, Li R, Tian X, Zhang Z (2019) Comparison of the feasibility of different washing solutions for combined soil washing and phytoremediation for the detoxification of cadmium (Cd) and zinc (Zn) in contaminated soil. Chemosphere 230: 510–518. http://doi.org/10.1016/j.chemosphere.2019.05.121.
Zhai Q, Guo Y, Tang X, Tian F, Zhao J, Zhang H, Chen W (2018) Removal of cadmium from rice by lactobacillus plantarum fermentation. Food Control 96: 357–364. https://doi.org/10.1016/j.foodcont.2018.09.029.
Zhang Z, Zhang N, Li H, Lu Y, Yang Z (2020) Potential health risk assessment for inhabitants posed by heavy metals in rice in Zijiang river basin, Hunan province, China. Environmental Science and Pollution Research 27(19): 24013–24024. http://doi.org/10.1007/s11356-020-08568-9.

No competing interests reported.

PDF

Version 1

posted 29 Jul, 2022

You are reading this latest preprint version

Leaching kinetics of cadmium from rice grain by dilute hydrochloric acid

Status:

Version 1

Abstract

Figures

1 Introduction

2 Experimental

2.1 Materials and chemicals

2.2 Experimental details

2.3 Characterization

3 Results And Discussion

3.1 SEM

3.2 Effect of acid concentration

3.3 Effect of solid/liquid ratio

3.4 Effect of temperature

3.5 Effect of stirring rate

3.6 Effect of size of rice grain

3.7 Reusability of leaching solution

3.8 Leaching kinetic model

4 Conclusion

Declarations

References

Competing Interests

Status:

Version 1