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Heavy Metals Remediation of Soil and Water

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A special issue of International Journal of Environmental Research and Public Health (ISSN 1660-4601). This special issue belongs to the section "Environmental Science and Engineering".

Deadline for manuscript submissions: closed (30 April 2023) | Viewed by 30704

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Special Issue Editor

Prof. Dr. Yuping Qiu

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Guest Editor

State Key Laboratory of Pollution Control and Resource Reuse, Department of Environmental Sciences, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, China
Interests: soil environmental chemistry; interface process; adsorption mechanism; transport in porous media; immobilization of heavy metals; chemical degradation; biochar application; microplastics

Special Issue Information

Dear Colleagues,

We are organizing a Special Issue on heavy metals remediation of soil and water in the International Journal of Environmental Research and Public Health. The venue is a peer-reviewed, scientific journal that publishes research papers, communications, and review articles in the interdisciplinary area of soil sciences, water sciences and environmental sciences. For detailed information about the journal, we refer you to https://0-www-mdpi-com.brum.beds.ac.uk/journal/ijerph.

The enthusiasm for remediation of heavy metal pollution in soil and water has never faded since the occurrence of a series of public health incidents of heavy metal poisoning (e.g., Minamata disease). Numerous remediation methods (physical, chemical, biological methods, etc.), materials and engineering equipment have been developed and applied for remediation of heavy-metal-contaminated soil and water. Nevertheless, some new technologies are still being explored, such as the simultaneous remediation of multiple heavy metals, the long-term effectiveness of remediation, the low-cost remediation method. In the future, green, sustainable and high-efficiency heavy metals remediation strategies will be important aspects to develop.

Based on the above, we organized this Special Issue to provide a scientifically inspiring discussion platform for colleagues to jointly promote the development of soil and water heavy metals remediation. This Special Issue is focused on the latest scientific research progress and technical solutions for heavy metals remediation of soil and water. We welcome the submission of manuscripts related to case studies of remediation (farmland, industrial site, surface water, groundwater), simultaneous remediation of soil (water) polluted by multiple heavy metals, remediation mechanisms, novel engineering materials and technologies for remediation, bioremediation (hyperaccumulator, microbial remediation, etc.), physicochemical remediation (soil washing, electrochemical adsorption, sedimentation, flocculation, etc.), amendment of biochar for cultivated land, etc.

Prof. Dr. Yuping Qiu
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Environmental Research and Public Health is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (14 papers)

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Research

15 pages, 2658 KiB

Open AccessArticle

Effect of Humus on the Solidification and Stabilization of Heavy Metal Contaminated River Sediment

by Huimin Gao, Hong Tao, Yang Yang, Qingyang Che, Qinyi Tang and Yong Gu

Int. J. Environ. Res. Public Health 2023, 20(6), 4882; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph20064882 - 10 Mar 2023

Cited by 5 | Viewed by 1369

Abstract

To better reutilize heavy metal contaminated river sediment containing organic matter, the sediments in a river located in Chongming District, Shanghai were collected and Portland cement was used as a curing agent along with commercial organic matter to conduct the solidification/stabilization experiment. The unconfined compressive strength and heavy metal leaching concentrations of solidified blocks with different water content, organic matter content, and cement content were tested and analyzed to determine the optimal ratio. The effects of fulvic acid (FA), humic acid (HA), and an HA/FA ratio on the solidification and stabilization, as well as the speciation of heavy metals in sediment before and after solidification and stabilization, were studied. The results showed that when the organic content of the sediment is 6.16%, the water content is 65% and the cement content is greater than 38%, so the curing effect proves to be satisfactory. Fulvic acid has a stronger inhibiting effect on cement hydration than humic acid, and its consumption in the curing process is more significant. The addition of humic acid contributes to the stabilization of heavy metals, while the increase in fulvic acid greatly weakens the stability of heavy metals. The exchangeable state of heavy metals in the sediment has been reduced to varying degrees after solidification and stabilization. The research results can provide a basis for the reclamation and utilization of heavy metal contaminated river sediment with organic matter. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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16 pages, 6199 KiB

Open AccessArticle

Potential Mechanism of Long-Term Immobilization of Pb/Cd by Layered Double Hydroxide Doped Chicken-Manure Biochar

by Xiaoxian Zhang, Tingran Liu, Jichen Zhang and Ling Zhu

Int. J. Environ. Res. Public Health 2023, 20(1), 867; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph20010867 - 03 Jan 2023

Cited by 2 | Viewed by 1459

Abstract

Layered double hydroxide (LDH)-doped chicken-manure biochar (CMB) with long-term stability was synthesized to immobilize Pb/Cd. MgAl-Cl-LDH-doped CMB (MHs) showed prominent long-term oxidation resistance and the least biodegradation sensitivity. Efficient Pb/Cd adsorption was observed on MHs, and the maximum adsorption capacities of Pb(II)/Cd(II) reached 1.95 mmol/g and 0.65 mmol/g, respectively. Precipitation and isomorphous substitution were identified as the key adsorption mechanisms, which formed highly stable Pb/Cd species (PbAl-CO₃-LDH, Pb₃(OH)₂CO₃, CdAl-Cl-LDH and CdCO₃). Pb(II) and Cd(II) precipitated with CO₃²⁻ in MHs; meanwhile, Mg(II) and Ca(II) in LDH layers were substituted by Pb(II) and Cd(II) respectively. Therefore, MHs had the potential for long-term stability of Pb/Cd. Moreover, complexation and electrostatic adsorption also contributed to the Pb/Cd immobilization to a certain extent. When 5% MHs (w/w) was applied to Pb/Cd contaminated smelting site soils, the soil pH increased from 5.9 to 7.3. After applying MHs for 25 d, the content of bioavailable Pb(II) and Cd(II) decreased by 98.8% and 85.2%, respectively, and the content of soluble Pb and Cd dropped by 99.5% and 96.7%. This study paves the way for designing a novel LDH doped CMB as efficient Pb/Cd immobilizers for smelting site soils. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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12 pages, 3619 KiB

Open AccessArticle

Hydrogen Peroxide Activated by Biochar-Supported Sulfidated Nano Zerovalent Iron for Removal of Sulfamethazine: Response Surface Method Approach

by Tiao Zhang, Cui Hu, Qian Li, Chuxin Chen, Jianhui Hu, Xiaoyu Xiao, Mi Li, Xiaoming Zou and Liangliang Huang

Int. J. Environ. Res. Public Health 2022, 19(16), 9923; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19169923 - 11 Aug 2022

Cited by 2 | Viewed by 1556

Abstract

Biochar (BC)-supported sulfide-modified nanoscale zerovalent iron (S-nZVI/BC) was prepared using the liquid-phase reduction method for the application of the removal of sulfamethazine (SMZ) from water. The reaction conditions were optimized by the Box–Behnken response surface method (RSM). A model was constructed based on the influence factors of the removal rate, i.e., the carbon-to-iron ratio (C/Fe), iron-sulfur ratio (Fe/S), pH, and hydrogen peroxide (H₂O₂) concentration, and the influence of each factor on the removal efficiency was investigated. The optimal removal process parameters were determined based on theoretical and experimental results. The results showed that the removal efficiency was significantly affected by the C/Fe ratio and pH (p < 0.0001) but relatively weakly affected by the Fe/S ratio (p = 0.0973) and H₂O₂ concentration (p = 0.022). The optimal removal process parameters were as follows: 0.1 mol/L H₂O₂, a pH of 3.18, a C/Fe ratio of 0.411, and a Fe/S ratio of 59.75. The removal rate of SMZ by S-nZVI/BC was 100% under these conditions. Therefore, it is feasible to use the Box–Behnken RSM to optimize the removal of emerging pollutants in water bodies by S-nZVI/BC. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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10 pages, 3416 KiB

Open AccessArticle

Improved Electron Efficiency of Zero-Valent Iron towards Cr(VI) Reduction after Sequestering in Al₂O₃ Microspheres

by Chuan Wang, Sha Wang, Cheng Song, Hong Liu and Jingxin Yang

Int. J. Environ. Res. Public Health 2022, 19(14), 8367; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19148367 - 08 Jul 2022

Cited by 1 | Viewed by 1282

Abstract

Zero-valent iron (ZVI) is widely used for groundwater remediation, but suffers from high electron consumption because of its free contact with non-target substrates such as O₂. Here, ZVI-ALOX particles were prepared via in situ NaBH₄ aqueous-phase reduction of ferrous ions (Fe²⁺) preabsorbed into Al₂O₃ microspheres. The electron efficiency (EE) and long-term performance of the material were improved by sequestering ZVI in the interspace of the Al₂O₃ microspheres (ZVI-ALOX). During long-term (350 days) continuous flow, Cr(VI) was removed to below the detection limit for over 23 days. Based on the high reactivity of ZVI towards Cr(VI), the EE of ZVI-ALOX was evaluated by measuring its Cr(VI) removal efficiency at neutral pH and comparing it with that of ZVI. The results showed that the EE of ZVI-ALOX during long-term continuous flow could reach 39.1%, which was much higher than that of ZVI (8.68%). The long-term continuous flow results also demonstrated that treatment of the influent solution achieved higher EE values than in the batch mode, where the presence of dissolved oxygen reduced EE values. At lower pollutant concentrations, the sequestering of ZVI was beneficial to its performance and long-term utility. In addition, measurement of the acute toxicity of treated column effluent using the indicator organism Photobacterium phosphoreum T₃ showed that ZVI-ALOX could reduce the toxicity of 5 mg/L Cr(VI) solution by ~70% in 350 d. The results from this study provide a basis for the development of permeable reactive barriers for groundwater remediation based on sequestered ZVI. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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17 pages, 5372 KiB

Open AccessArticle

Assessment of Trace Metals Contamination, Species Distribution and Mobility in River Sediments Using EDTA Extraction

by Małgorzata Wojtkowska and Jan Bogacki

Int. J. Environ. Res. Public Health 2022, 19(12), 6978; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19126978 - 07 Jun 2022

Cited by 4 | Viewed by 1482

Abstract

The impact of the ethylenediaminetetraacetic acid (EDTA) on speciation image of selected trace metals (Zn, Cd, Cu, Pb) in bottom sediments was determined. The influence on the effectiveness of metal removal of extraction multiplicity, type of metal, extraction time and concentration of EDTA were analyzed. With the increase of extraction multiplicity, the concentration of EDTA and contact time, the efficiency of trace metals leaching increased. The speciation analysis revealed that EDTA not only leached metals from bioavailable fractions, but also caused the transition of the metals between the fractions. The biggest amounts of bioavailable forms were found for Cd, less for Zn. The amount of bioavailable fraction was the lowest for Cu and Pb. The two first-order kinetic models fitted well the kinetics of metals extraction with EDTA, allowing the metals fractionation into “labile” (Q₁), “moderately labile” (Q₂) and “not extractable” fractions (Q₃). Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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16 pages, 3776 KiB

Open AccessArticle

Effects of Pyrolysis Temperature and Chemical Modification on the Adsorption of Cd and As(V) by Biochar Derived from Pteris vittata

by Kazuki Sugawara, Kouhei Ichio, Yumiko Ichikawa, Hitoshi Ogawa and Seiichi Suzuki

Int. J. Environ. Res. Public Health 2022, 19(9), 5226; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19095226 - 25 Apr 2022

Cited by 6 | Viewed by 1963

Abstract

Phytoremediation can be applied successfully to solve the serious worldwide issue of arsenic (As) and cadmium (Cd) pollution. However, the treatment of biomass containing toxic elements after remediation is a challenge. In this study, we investigated the effective use of biomass resources by converting the As hyperaccumulator P. vittata into biochar to adsorb toxic elements. Plant biomass containing As was calcined at 600, 800, and 1200 °C, and its surface structure and adsorption performances for As(V) and Cd were evaluated. Pyrolysis at 1200 °C increased the specific surface area of the biochar, but it did not significantly affect its adsorption capacity for toxic elements. The calcined biochar had very high adsorption capacities of 90% and 95% for As(V) and Cd, respectively, adsorbing 6000 mmol/g-biochar for As(V) and 4000 mmol/g-biochar for Cd. The As(V) adsorption rate was improved by FeCl₃ treatment. However, the adsorption capacity for Cd was not significantly affected by the NaOH treatment. In conclusion, it was found that after phytoremediation using P. vittata biomass, it can be effectively used as an environmental purification material by conversion to biochar. Furthermore, chemical modification with FeCl₃ improves the biochar’s adsorption performance. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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19 pages, 6917 KiB

Open AccessArticle

Ecological Risk Assessment of Trace Metal in Pacific Sector of Arctic Ocean and Bering Strait Surface Sediments

by Juan Wang, William A. Gough, Jing Yan and Zhibo Lu

Int. J. Environ. Res. Public Health 2022, 19(8), 4454; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19084454 - 07 Apr 2022

Cited by 8 | Viewed by 1738

Abstract

The arctic region is a remote area with relatively few anthropogenic inputs, but there is increasing concern over toxic trace metal contamination in the Arctic Ocean. In this study, distribution characteristics of eight trace metals in the surface sediment of the Pacific Sector of the Arctic Ocean and Bering Strait are analyzed. The geochemical baseline value of each metal element is explored using the relative cumulative frequency curve method; the enrichment factor (EF), geo-accumulation index (I_geo) and potential ecological risk index (RI) are applied to assess the ecological risk level of the trace metals. According to the results, Cu, As and Hg had a little more content variation, and their contents in some areas were significantly higher than the previous reports. EF values show an obvious enrichment of element As, followed by Cr element with the moderate enrichment; the enrichment of the other six elements are not related to human activity. The I_geo value shows a moderately contaminated to heavily contaminated level of As and a moderately contaminated level of Cr. According to the potential ecological risk indexes in each site, most sites are at a low ecological risk level except five sites with RI/baseline values exceeding 150 which are at a moderate ecological risk level. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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15 pages, 4180 KiB

Open AccessArticle

Insight into the Adsorption Behaviors of Antimony onto Soils Using Multidisciplinary Characterization

by Zi-Qi Mu, Da-Mao Xu and Rong-Bing Fu

Int. J. Environ. Res. Public Health 2022, 19(7), 4254; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19074254 - 02 Apr 2022

Cited by 5 | Viewed by 1707

Abstract

Antimony (Sb) pollution in soils is an important environmental problem, and it is imperative to investigate the migration and transformation behavior of Sb in soils. The adsorption behaviors and interaction mechanisms of Sb in soils were studied using integrated characterization techniques and the batch equilibrium method. The results indicated that the adsorption kinetics and isotherms of Sb onto soils were well fitted by the first-order kinetic, Langmuir, and Freundlich models, respectively, while the maximum adsorbed amounts of Sb (III) in soil 1 and soil 2 were 1314.46 mg/kg and 1359.25 mg/kg, respectively, and those of Sb (V) in soil 1 and soil 2 were 415.65 mg/kg and 535.97 mg/kg, respectively. In addition, pH ranging from 4 to 10 had little effect on the adsorption behavior of Sb. Moreover, it was found that Sb was mainly present in the residue fractions, indicating that Sb had high geochemical stability in soils. SEM analysis indicated that the distribution positions of Sb were highly coincident with Ca, which was mainly due to the existence of calcium oxides, such as calcium carbonate and calcium hydroxide, that affected Sb adsorption, and further resulted in Sb and Ca bearing co-precipitation. XPS analysis revealed the valence state transformation of Sb (III) and Sb (V), suggesting that Fe/Mn oxides and reactive oxygen species (ROS) served as oxidant or reductant to promote the occurrence of the Sb redox reaction. Sb was mobile and leachable in soils and posed a significant threat to surface soils, organisms, and groundwater. This work provides a fundamental understanding of Sb adsorption onto soils, as well as a theoretical guide for studies on the adsorption and migration behavior of Sb in soils. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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19 pages, 23730 KiB

Open AccessArticle

S-Fertilizer (Elemental Sulfur) Improves the Phytoextraction of Cadmium through Solanum nigrum L.

by Aishah Alatawi, Xiukang Wang, Arosha Maqbool, Muhammad Hamzah Saleem, Kamal Usman, Muhammad Rizwan, Tahira Yasmeen, Muhammad Saleem Arif, Shamaila Noreen, Afzal Hussain and Shafaqat Ali

Int. J. Environ. Res. Public Health 2022, 19(3), 1655; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19031655 - 31 Jan 2022

Cited by 15 | Viewed by 2565

Abstract

Soil contamination with toxic heavy metals [such as cadmium (Cd)] is becoming a serious global problem due to the rapid development of the social economy. This study was carried out to assess the beneficial role of two different kinds of (S)-fertilizer in the phytoremediation of Cd contaminated soil through Solanum nigrum L. Gypsum (Gyp) and Elemental sulfur (ES) was applied alone and in combination with different ratios (0, 100:0, 0:100, 50:50 mg kg⁻¹) accompanied by different Cd levels (0, 25, 50 mg kg⁻¹). After seventy days of sowing, plants were harvested for determination of growth, physiological characteristics, oxidants and antioxidants, along with Cd uptake from different parts of the plant. Cd toxicity significantly inhibited growth, physiology and plant defence systems, and also increased Cd uptake in the roots and shoots of Solanum nigrum L. The application of Gyp 100 mg kg⁻¹ boosted plant growth and physiology along with oxidants and antioxidants activity as compared to ES 100 mg kg⁻¹ alone, and combine application of GYP+ES 50 + 50 mg kg⁻¹. The application of ES 100 mg kg⁻¹ showed an effective approach to decreasing Cd uptake as compared to Gyp 100 mg kg⁻¹. Overall results showed that the combined application of GYP+ES 50 + 50 mg kg⁻¹ significantly enhanced the phytoremediation potential of S. nigrum in Cd contaminated soil. Thus, it is highly recommended to apply the combined application of GYP+ES for phytoremediation of Cd contaminated soil. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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14 pages, 4646 KiB

Open AccessArticle

Remediation of Toxic Heavy Metal Contaminated Soil by Combining a Washing Ejector Based on Hydrodynamic Cavitation and Soil Washing Process

by Hyunsoo Kim, Kanghee Cho, Oyunbileg Purev, Nagchoul Choi and Jaewon Lee

Int. J. Environ. Res. Public Health 2022, 19(2), 786; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph19020786 - 11 Jan 2022

Cited by 8 | Viewed by 2079

Abstract

Based on the features of hydrodynamic cavitation, in this study, we developed a washing ejector that utilizes a high-pressure water jet. The cavitating flow was utilized to remove fine particles from contaminated soil. The volume of the contaminants and total metal concentration could be correlated to the fine-particle distribution in the contaminated soil. These particles can combine with a variety of pollutants. In this study, physical separation and soil washing as a two-step soil remediation strategy were performed to remediate contaminated soils from the smelter. A washing ejector was employed for physical separation, whereas phosphoric acid was used as the washing agent. The particles containing toxic heavy metals were composed of metal phase encapsulated in phyllosilicates, and metal phase weakly bound to phyllosilicate surfaces. The washing ejector involves the removal of fine particles bound to coarse particles and the dispersion of soil aggregates. From these results we determined that physical separation using a washing ejector was effective for the treatment of contaminated soil. Phosphoric acid (H₃PO₄) was effective in extracting arsenic from contaminated soil in which arsenic was associated with amorphous iron oxides. Thus, the obtained results can provide useful information and technical support for field soil washing for the remediation of soil contaminated by toxic heavy metals through emissions from the mining and ore processing industries. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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8 pages, 1288 KiB

Open AccessArticle

Assessment of Copper and Heavy Metals in Family-Run Vineyard Soils and Wines of Campania Region, South Italy

by Valentina Roviello, Ugo Caruso, Giovanni Dal Poggetto and Daniele Naviglio

Int. J. Environ. Res. Public Health 2021, 18(16), 8465; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18168465 - 11 Aug 2021

Cited by 5 | Viewed by 2071

Abstract

Copper-based phytosanitary treatments are widely employed in viticulture for combating the fungal diseases of European grape (Vitis vinifera L.). Herein we evaluated copper accumulation in the soil of a 50-year-old still productive vineyard in South Italy in comparison with samples taken from a ‘control’ area in which grapevines had never been cultivated, as well from an abandoned vineyard, now planted with cereals and forage crops, both close to the main area under investigation. Even though the heavy metal contents detected were not of concern for soils nor for wine, Cu accumulates in the soil in amounts significantly higher than the (grapevine free) control and remains at detectable concentrations also in abandoned vineyards where spraying activities had ceased about 20 years before this study. Despite the long Cu residence times in soil, the wine produced with grapes of the same vineyard showed Cu levels low enough to be safely used for human consumption, probably due to mechanisms of metal precipitation occurring during wine maturation, which are typically accompanied by sedimentation processes in artisanal production. However, this should not diminish the urgency of decreasing the copper usage as antifungal remedy in viticulture to prevent copper contamination of the agricultural soils. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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20 pages, 8262 KiB

Open AccessArticle

Pristine and Magnetic Kenaf Fiber Biochar for Cd²⁺ Adsorption from Aqueous Solution

by Anwar Ameen Hezam Saeed, Noorfidza Yub Harun, Suriati Sufian, Muhammad Roil Bilad, Zaki Yamani Zakaria, Ahmad Hussaini Jagaba, Aiban Abdulhakim Saeed Ghaleb and Haetham G. Mohammed

Int. J. Environ. Res. Public Health 2021, 18(15), 7949; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18157949 - 27 Jul 2021

Cited by 41 | Viewed by 3018

Abstract

Development of strategies for removing heavy metals from aquatic environments is in high demand. Cadmium is one of the most dangerous metals in the environment, even under extremely low quantities. In this study, kenaf and magnetic biochar composite were prepared for the adsorption of Cd²⁺. The synthesized biochar was characterized using (a vibrating-sample magnetometer VSM), Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The adsorption batch study was carried out to investigate the influence of pH, kinetics, isotherm, and thermodynamics on Cd²⁺ adsorption. The characterization results demonstrated that the biochar contained iron particles that help in improving the textural properties (i.e., surface area and pore volume), increasing the number of oxygen-containing groups, and forming inner-sphere complexes with oxygen-containing groups. The adsorption study results show that optimum adsorption was achieved under pH 5–6. An increase in initial ion concentration and solution temperature resulted in increased adsorption capacity. Surface modification of biochar using iron oxide for imposing magnetic property allowed for easy separation by external magnet and regeneration. The magnetic biochar composite also showed a higher affinity to Cd²⁺ than the pristine biochar. The adsorption data fit well with the pseudo-second-order and the Langmuir isotherm, with the maximum adsorption capacity of 47.90 mg/g. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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18 pages, 7227 KiB

Open AccessArticle

Remediation of Cd-Contaminated Soil by Modified Nanoscale Zero-Valent Iron: Role of Plant Root Exudates and Inner Mechanisms

by Danlian Huang, Yunhe Yang, Rui Deng, Xiaomin Gong, Wei Zhou, Sha Chen, Bo Li and Guangfu Wang

Int. J. Environ. Res. Public Health 2021, 18(11), 5887; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18115887 - 30 May 2021

Cited by 11 | Viewed by 2944

Abstract

In this study, the role of exogenous root exudates and microorganisms was investigated in the application of modified nanoscale zero-valent iron (nZVI) for the remediation of cadmium (Cd)-contaminated soil. In this experiment, citric acid (CA) was used to simulate root exudates, which were then added to water and soil to simulate the pore water and rhizosphere environment. In detail, the experiment in water demonstrated that low concentration of CA facilitated Cd removal by nZVI, while the high concentration achieved the opposite. Among them, CA can promote the adsorption of Cd not only by direct complexation with heavy metal ions, but also by indirect effect to promote the production of iron hydroxyl oxides which has excellent heavy metal adsorption properties. Additionally, the H⁺ dissociated from CA posed a great influence on Cd removal. The situation in soil was similar to that in water, where low concentrations of CA contributed to the immobilization of Cd by nZVI, while high concentrations promoted the desorption of Cd and the generation of CA–Cd complexes which facilitated the uptake of Cd by plants. As the reaction progressed, the soil pH and cation exchange capacity (CEC) increased, while organic matter (OM) decreased. Meanwhile, the soil microbial community structure and diversity were investigated by high-throughput sequencing after incubation with CA and nZVI. It was found that a high concentration of CA was not conducive to the growth of microorganisms, while CMC had the effect of alleviating the biological toxicity of nZVI. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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24 pages, 1497 KiB

Open AccessArticle

Biochar Mediated-Alleviation of Chromium Stress and Growth Improvement of Different Maize Cultivars in Tannery Polluted Soils

by Muhammad Asaad Bashir, Xiukang Wang, Muhammad Naveed, Adnan Mustafa, Sobia Ashraf, Tayyaba Samreen, Sajid Mahmood Nadeem and Moazzam Jamil

Int. J. Environ. Res. Public Health 2021, 18(9), 4461; https://0-doi-org.brum.beds.ac.uk/10.3390/ijerph18094461 - 22 Apr 2021

Cited by 35 | Viewed by 3647

Abstract

Soil pollution with heavy metal is a serious problem across the globe and is on the rise due to the current intensification of chemical industry. The leather industry is one of them, discharging chromium (Cr) in huge quantities during the process of leather tanning and polluting the nearby land and water resources, resulting in deterioration of plant growth. In this study, the effects of biochar application at the rate of 3% were studied on four maize cultivars, namely NK-8441, P-1543, NK-8711, and FH-985, grown in two different tannery polluted Kasur (K) and Sialkot (S) soils. Maize plants were harvested at vegetative growth and results showed that Cr toxicity adversely not only affected their growth, physiology, and biochemistry, but also accumulated in their tissues. However, the level of Cr toxicity, accumulation, and its influence on maize cultivars varied greatly in both soils. In this pot experiment, biochar application played a crucial role in lessening the Cr toxicity level, resulting in significant increase in plant height, biomass (fresh and dry), leaf area, chlorophyll pigments, photosynthesis, and relative water content (RWC) over treatment set as a control. However, applied biochar significantly decreased the electrolyte leakage (EL), antioxidant enzymes, lipid peroxidation, proline content, soluble sugars, and available fraction of Cr in soil as well as Cr (VI and III) concentration in root and shoot tissues of maize plant. In addition to this, maize cultivar differences were also found in relation to their tolerance to Cr toxicity and cultivar P-1543 performed better over other cultivars in both soils. In conclusion, biochar application in tannery polluted soils could be an efficient ecofriendly approach to reduce the Cr toxicity and to promote plant health and growth. Full article

(This article belongs to the Special Issue Heavy Metals Remediation of Soil and Water)

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