Feasibility of a counter-current extraction procedure for the removal of heavy metals from contaminated soils

Heavy metals (HMs) toxicity represents a global problem depending on the soil environment’s geochemical forms. Biochar addition safely reduces HMs mobile forms, thus, reducing their toxicity to plants. While several studies have shown that biochar could significantly stabilize HMs in contaminated soils, the study of the relationship of soil properties to potential mechanisms still needs further clarification; hence the importance of assessing a naturally contaminated soil amended, in this case with Paulownia biochar (PB) and Bamboo biochar (BB) to fractionate Pb, Cd, Zn, and Cu using short sequential fractionation plans. The relationship of soil pH and organic matter and its effect on the redistribution of these metals were estimated. The results indicated that the acid-soluble metals decreased while the fraction bound to organic matter increased compared to untreated pots. The increase in the organic matter metal-bound was mostly at the expense of the decrease in the acid extractable and Fe/Mn bound ones. The highest application of PB increased the organically bound fraction of Pb, Cd, Zn, and Cu (62, 61, 34, and 61%, respectively), while the BB increased them (61, 49, 42, and 22%, respectively) over the control. Meanwhile, Fe/Mn oxides bound represents the large portion associated with zinc and copper. Concerning soil organic matter (SOM) and soil pH, as potential tools to reduce the risk of the target metals, a significant positive correlation was observed with acid-soluble extractable metal, while a negative correlation was obtained with organic matter-bound metal. The principal component analysis (PCA) shows that the total variance represents 89.7% for the TCPL-extractable and HMs forms and their relation to pH and SOM, which confirms the positive effect of the pH and SOM under PB and BB treatments on reducing the risk of the studied metals. The mobility and bioavailability of these metals and their geochemical forms widely varied according to pH, soil organic matter, biochar types, and application rates. As an environmentally friendly and economical material, biochar emphasizes its importance as a tool that makes the soil more suitable for safe cultivation in the short term and its long-term sustainability. This study proves that it reduces the mobility of HMs, their environmental risks and contributes to food safety. It also confirms that performing more controlled experiments, such as a pot, is a disciplined and effective way to assess the suitability of different types of biochar as soil modifications to restore HMs contaminated soil via controlling the mobilization of these minerals.

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Enhanced Electrokinetic Remediation for the Removal of Heavy Metals from Contaminated Soils

Applied Sciences ◽

10.3390/app11041799 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1799

Author(s):

Claudio Cameselle ◽

Susana Gouveia ◽

Adrian Cabo

Keyword(s):

Heavy Metals ◽

Citric Acid ◽

Organic Acids ◽

Contaminated Soils ◽

Electrokinetic Remediation ◽

Deionized Water ◽

Soil Specimen ◽

Removal Of Heavy Metals ◽

Ph Conditions ◽

Neutral Metal

The electrokinetic remediation of an agricultural soil contaminated with heavy metals was studied using organic acids as facilitating agents. The unenhanced electrokinetic treatment using deionized water as processing fluid did not show any significant mobilization and removal of heavy metals due to the low solubilization of metals and precipitation at high pH conditions close to the cathode. EDTA and citric acid 0.1 M were used as facilitating agents to favor the dissolution and transportation of metals. The organic acids were added to the catholyte and penetrated into the soil specimen by electromigration. EDTA formed negatively charged complexes. Citric acid formed neutral metal complexes in the soil pH conditions (pH = 2–4). Citric acid was much more effective in the dissolution and transportation out of the soil specimen of complexed metals. In order to enhance the removal of metals, the concentration of citric acid was increased up to 0.5 M, resulting in the removal of 78.7% of Cd, 78.6% of Co, 72.5% of Cu, 73.3% of Zn, 11.8% of Cr and 9.8% of Pb.

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Selection and test of effective chelators for removal of heavy metals from contaminated soils

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

10.1016/s0148-9062(97)87333-0 ◽

1996 ◽

Vol 33 (8) ◽

pp. A347

Keyword(s):

Heavy Metals ◽

Contaminated Soils ◽

Removal Of Heavy Metals

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Effect of Soil Washing Solutions on Simultaneous Removal of Heavy Metals and Arsenic from Contaminated Soil

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17093133 ◽

2020 ◽

Vol 17 (9) ◽

pp. 3133 ◽

Cited By ~ 1

Author(s):

Kanghee Cho ◽

Eunji Myung ◽

Hyunsoo Kim ◽

Cheonyoung Park ◽

Nagchoul Choi ◽

...

Keyword(s):

Heavy Metals ◽

Sulfuric Acid ◽

Phosphoric Acid ◽

Contaminated Soil ◽

Contaminated Soils ◽

Soil Washing ◽

Metal Extraction ◽

Simultaneous Removal ◽

Removal Of Heavy Metals ◽

Removal Efficiencies

In this study, we investigated the feasibility of using a solution of sulfuric acid and phosphoric acid as an extraction method for soil-washing to remove Cu, Pb, Zn, and As from contaminated soil. We treated various soil particles, including seven fraction sizes, using sulfuric acid. In addition, to improve Cu, Pb, Zn, and As removal efficiencies, washing agents were compared through batch experiments. The results showed that each agent behaved differently when reacting with heavy metals (Cu, Pb, and Zn) and As. Sulfuric acid was more effective in extracting heavy metals than in extracting As. However, phosphoric acid was not effective in extracting heavy metals. Compared with each inorganic acid, As removal from soil by washing agents increased in the order of sulfuric acid (35.81%) < phosphoric acid (62.96%). Therefore, an enhanced mixture solution using sulfuric acid and phosphoric acid to simultaneously remove heavy metals and As from contaminated soils was investigated. Sulfuric acid at 0.6 M was adopted to combine with 0.6 M phosphoric acid to obtain the mixture solution (1:1) that was used to determine the effect for the simultaneous removal of both heavy metals and As from the contaminated soil. The removal efficiencies of As, Cu, Pb, and Zn were 70.5%, 79.6%, 80.1%, and 71.2%, respectively. The combination of sulfuric acid with phosphoric acid increased the overall As and heavy metal extraction efficiencies from the contaminated soil samples. With the combined effect of dissolving oxides and ion exchange under combined washings, the removal efficiencies of heavy metals and As were higher than those of single washings.

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Performance of Tailing Contaminated Soils Solidified by Phosphate-Based Binder

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.858.104 ◽

2016 ◽

Vol 858 ◽

pp. 104-110 ◽

Cited By ~ 1

Author(s):

Hao Liang Wu ◽

Yan Jun Du ◽

Yu You Yang ◽

M.L. Wei

Keyword(s):

Heavy Metals ◽

Contaminated Soils ◽

Extraction Procedure ◽

Mining Area ◽

Strength Properties ◽

Curing Time ◽

X Ray Diffraction ◽

Electron Microscopic ◽

Unconfined Compression Test ◽

Binder Type

This paper presents a study on soils, from the Baoshan mining site, contaminated with heavy metals and stabilized by using a new phosphate-based binder. Unconfined compression test, sequential extraction procedure, X-ray diffraction and scanning electron microscopic procedures are carried out. This study aims to explore the effects of binder type, binder content and curing time of solidified contaminated soils on leaching and strength properties of the soils contaminated with heavy metals in the mining area. The results showed that as the curing time is increased from 0 d to 28 d, the new phosphate-based binder stabilized contaminated soil underwent several changes: 1) improved the strength and 2) decreased the exchangeable Zn and Pb and increased the residual contents.

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Evaluation of Acid Leaching on the Removal of Heavy Metals and Soil Fertility in Contaminated Soil

Journal of Chemistry ◽

10.1155/2018/5036581 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

Chen-Yao Chu ◽

Tzu-Hsing Ko

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Seed Germination ◽

Soil Fertility ◽

Sequential Extraction ◽

Contaminated Soil ◽

Contaminated Soils ◽

Germination Rate ◽

Extraction Procedure ◽

Acid Leaching

Heavy metal-contaminated soils were leached with various acid reagents, and a series of treatments was assessed to understand soil fertility after acid leaching. Aqua regia digestion and a five-step sequential extraction procedure were applied to determine heavy metal distribution. The average total concentrations of Zn, Cd, Cu, and Pb for contaminated soil were 1334, 25, 263, and 525 mg·kg−1 based on the ICP/AES quantitative analysis. Other than Pb extracted by H2SO4, over 50% removal efficiency of other heavy metals was achieved. A five-step sequential extraction revealed that the bound-to-carbonate and bound-to-Fe-Mn oxides were the major forms of the heavy metals in the soil. The addition of organic manure considerably promoted soil fertility and increased soil pH after acid leaching. Seed germination experiments demonstrated that after acid leaching, the soil distinctly inhibited plant growth and the addition of manure enhanced seed germination rate from 35% to 84%. Furthermore, the procedure of soil turnover after acid leaching and manure addition greatly increased seed germination rate by 61% and shortened the initial germination time. Seed germination in untreated soil was superior to that in acid-leached soil, illustrating that the phytotoxic effect of acid leaching is more serious than that of heavy metals.

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Chemical and Biological Leaching Methods to Remove Heavy Metals from Sewage Sludge: A Review

JOURNAL OF ADVANCES IN CHEMISTRY ◽

10.24297/jac.v4i3.948 ◽

2008 ◽

Vol 4 (3) ◽

pp. 509-517

Author(s):

Lugard N. Ukiwe ◽

Allinor J.I ◽

Ejele A.E ◽

Anyadiegwu C.I.C ◽

Ibeneme S.I

Keyword(s):

Heavy Metals ◽

Sewage Sludge ◽

Thiobacillus Ferrooxidans ◽

Extraction Procedure ◽

Metal Extraction ◽

High Yield ◽

Chemical Leaching ◽

Solids Concentration ◽

Acid Consumption ◽

Removal Of Heavy Metals

The removal of heavy metals (HMs) in sewage sludge (SS) is important since sludge is often disposed or applied on farmland to enhance soil fertility. The present study reviewed two conceptual approaches (chemical and biological leaching) of removing HMs present in SS. In the chemical leaching method, traditional acid treatment together with novel methods such as aeration, complexation and sequential extraction procedure have been reviewed extensively. Certain factors influence the removal of HMs in SS. These factors include; pH, leaching agent, redox potential, and contact time. Nitric acid (HNO3), hydrochloric acid (HCl), sulphuric acid (H2SO4), phosphoric acid (H3PO4), ethylenediamine tetraacetic acid (EDTA), as well as Thiobacillus thiooxidans and Thiobacillus ferrooxidans are the most widely studied leaching agents and substrates involved in the chemical and bioleaching processes. However, the bioleaching process has been proposed as a safe, efficient, economical, environmental friendly method to remove HMs in SS due to its simplicity, high yield of metal extraction, low acid consumption, and low sludge solids concentration. Nevertheless, the present review has noted that most researchers are of the opinion that more studies are needed in the bioleaching method in order to enhance its commercial attraction.

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