Mechanism Of Heavy Metal Removal Research Articles

A multifunctional coconut shell biochar modified by titanium dioxide for heavy metal removal in water/soil and tetracycline degradation

Heavy metals and tetracycline pollute the environment and endanger human health. This work prepared a multifunctional coconut shell biochar (Ti-XBC) through NaHCO3 activation and TiO2 modification. The modified coconut shell biochar was characterized by various methods. Ti-4BC exhibited excellent removal performance for heavy metals. The maximum adsorption capacity of Ti-4BC on Cd2+, Pb2+, Cr3+, and Cr6+ reached 104.2, 136.8, 101.2, 112.4 mg/g in water. The adsorption of Ti-4BC for four metal ions had a competitive effect in the binary metal system. It also reduced the mobility of four heavy metal ions in soil. Density functional theory (DFT) calculations were employed to explain the mechanism of heavy metal removal. Additionally, the degradation performance and mechanism of Ti-4BC towards tetracycline were investigated. The results indicated that the maximum degradation rate was 99.4%. Overall, this work developed a multifunctional material capable of both removing heavy metals and degrading antibiotics, addressing the issue of single-function in biochar. This provided a novel approach for tackling complex and diverse environmental pollution scenarios.

New insights into sustainable in-situ fixation of heavy metals in disturbed seafloor sediments

To address the issues of plume formation and heavy metal ion release during deep-sea mining operations, this study employed multi-sourced mineral composite roasting materials (MMCCM) of varying sizes. An in-situ capping technique was applied within a simulated system to immobilize heavy metals in contaminated sediments. The results demonstrated that capping with MMCCM of different sizes significantly suppressed the upward migration of Cu, Co, and Ni from sediments into the overlying seawater following disturbance. Ion diffusion was identified as a key mechanism driving heavy metal migration. By calculating the release rates of heavy metals during both the disturbed and undisturbed phases, it was found that the application of MMCCM induced a negative diffusion of heavy metals, indicating that the MMCCM-sediment layer functioned as a "sink" for heavy metals. FTIR and XPS analysis showed that the primary mechanisms for heavy metal removal by MMCCM were electrostatic attraction and complexation-precipitation. Additionally, capping with MMCCM facilitated the transition of heavy metals from labile to stable forms within the sediments. Through comprehensive evaluation, the long-term effectiveness of the fixed effects was demonstrated as follows: large MMCCM (L@MCM) > medium MMCCM (M@MCM) > small MMCCM (S@MCM) > powder MMCCM (P @ MCM). Finally, we proposed future research directions and introduced the DQSE framework for the sustainable application of MMCCM. Based on the above findings, this study provides new insights and research references for the in-situ immobilization of heavy metals and plume reduction during future deep-sea mining processes.

Stenotrophomonas pavanii MY01 induces phosphate precipitation of Cu(II) and Zn(II) by degrading glyphosate: performance, pathway and possible genes involved.

Microbial bioremediation is an advanced technique for removing herbicides and heavy metals from agricultural soil. In this study, the strain Stenotrophomonas pavanii MY01 was used for its ability to degrade glyphosate, a phosphorus-containing organic compound, producing PO4 3- as a byproduct. PO4 3- is known to form stable precipitates with heavy metals, indicating that strain MY01 could potentially remove heavy metals by degrading glyphosate. Therefore, the present experiment induced phosphate precipitation from Cu(II) (Hereinafter referred to as Cu2+) and Zn(II) (Hereinafter referred to as Zn2+) by degrading glyphosate with strain MY01. Meanwhile, the whole genome of strain MY01 was mined for its glyphosate degradation mechanism and its heavy metal removal mechanism. The results of the study showed that the strain degraded glyphosate best at 34°C, pH = 7.7, and an inoculum of 0.7%, reaching 72.98% within 3d. The highest removal of Cu2+ and Zn2+ in the test was 75.95 and 68.54%, respectively. A comparison of strain MY01's genome with glyphosate degradation genes showed that protein sequences GE000474 and GE002603 had strong similarity to glyphosate oxidoreductase and C-P lyase. This suggests that these sequences may be key to the strain's ability to degrade glyphosate. The GE001435 sequence appears to be related to the phosphate pathway, which could enable phosphate excretion into the environment, where it forms stable coordination complexes with heavy metals.

Exploring the synergistic interplay of sulfur metabolism and electron transfer in Cr(VI) and Cd(II) removal by Clostridium thiosulfatireducens: Genomic and mechanistic insights

In this study, a sulfate-reducing bacterium, Clostridium thiosulfatireducens (CT) was reported and the performance and removal mechanism of Cr(VI) and Cd(II) removal were investigated. It is noteworthy that the dsrAB gene is absent in this strain, but the strain is capable of producing sulfide. The conversion rate of Cr(VI) by CT was 84.24 % at a concentration of 25 mg/L, and the conversion rate of Cd(II) was 94.19 % at a concentration of 28 mg/L. The complete genome is 6,106,624 bp and the genome consisted of a single chromosome. The GC content of the chromosomes was 29.65 %. The mechanism of heavy metal removal by CT bacteria mainly includes biosorption, electron transfer and redox, with reduction combined with S2− precipitation as the main pathway. The product characterization results showed that the formation of mainly ionic crystals and precipitates (CdS, Cd(OH)2, Cr(OH)3, Cr2O3) after adsorption. Genome-wide techniques have shown that the clearance of Cr(VI) and Cd(II) by CT is largely dependent on sulfate transport, sulfur metabolism, and energy metabolism to some extent. In addition, genes related to ATP binding, electron carrier activity, transporter protein genes, and DNA repair are also important factors to improve the heavy metal resistance and transformation ability of CT strains. Both the Fe–S cycle and the ROS-resistant system can enhance the electron transfer activity and thus slow down the damage of heavy metals to microorganisms. This study fills the gap in the understanding of the basic properties and heavy metal transformation mechanism of CT.

Bio-sorbents: A Novel Technology to Mitigate Heavy Metal Pollution

The health of living beings is seriously threatened by the toxicity and bioaccumulation tendency of heavy metals in the environment. Heavy metals cannot be broken down by chemical or biological processes, unlike organic pollutants. They can therefore only be changed into less dangerous species. Heavy metal pollution of the environment has gone above the advised level and is harmful to all life forms. The process of using microorganisms to absorb, precipitate, oxidize, and reduce heavy metals in soil is known as "microbial remediation." The term "bio-sorption" refers to "the ability of biological materials to accumulate heavy metals from waste water through metabolically mediated or physico-chemical pathway of uptake." It has been demonstrated that fungi, yeast, algae, and bacteria are potential metal-biosorbents. To adequately address the major issues involved, a sustainable method must be devised to choose the best bio-sorbent, operating conditions, and effective mechanism of heavy metal removal in industrial effluent.

Remediation of Heavy Metals in Polluted Water by Immobilized Algae: Current Applications and Future Perspectives

The progression of urban industrialization releases large quantities of heavy metals into water, resulting in the severe heavy metal contamination of the aquatic environment. Traditional methods for removing heavy metals from wastewater generally have varying removal efficiencies, whereas algae adsorption technology is a cost-effective and sustainable bioremediation technique. A green technology that immobilizes algae through a carrier to improve biosorbent’s stability and adsorption performance is immobilization technology. The purpose of this review is to study the optimization strategy of the immobilization of algae for the bioremediation of heavy metals and to comprehensively analyze immobilized algae technology in terms of sustainability. The analysis of the mechanism of heavy metal removal by immobilized algae and the parameters affecting the efficiency of the biosorbent, as well as the approach based on life cycle assessment and economic analysis, allowed the identification of the optimization of the adsorption performance of immobilized algae. This provides a theoretical basis for the practical application of algal bioremediation.

Removal of various aqueous heavy metals by polyethylene glycol modified MgAl-LDH: Adsorption mechanisms and vital role of precipitation

The adsorption mechanisms of layered double hydroxides (LDHs) for aqueous heavy metals have been studied extensively, but few prior quantitative investigations of each mechanism were conducted. In this work, we prepared polyethylene glycol modified MgAl-LDH with molecular weight of 200 and 4000 (LDH-200 and LDH-4000) to investigate the adsorption mechanisms for Cu(II), Pb(II), and Cd(II) qualitatively and quantitatively. The interaction mechanisms were conducted by a number of characterization methods and quantitatively analyzed by a series of extraction procedures. The results indicated that the leading mechanisms of LDH-200 and LDH-4000 for Cu(II), Pb(II), and Cd(II) were precipitation with contributions of 44.20%-72.12%. The percentages of complexation, isomorphous substitution, and electrostatic attraction to the total adsorption amounts were 12.43%-37.89%, 6.35%-18.81%, and < 3.5%, respectively. For MgAl-LDH, the precipitation and complexation mechanisms accounted for 28.68%-52.71% and 18.12%-66.13%. After polyethylene glycol modification, the contributions of precipitation increased and the complexation decreased. The material characterizations and quantitative analyses of adsorption mechanisms provide theoretical guidance and foundation to further understand the interfacial sorption process, which is conducive to a deeper understanding of the removal mechanism of heavy metals.

Two recyclable and complementary adsorbents of coal-based and bio-based humic acids: High efficient adsorption and immobilization remediation for Pb(II) contaminated water and soil

Humic acid can effectively bind heavy metals and is a promising remediation agent for heavy metals-contaminated water and soil. Many successful applications of humic acid have been reported, but rarely studied the specific process and mechanism of heavy metal removal by humic acids from water and soil, especially the simultaneous application of coal-based and bio-based humic acids. In this work, two kinds of coal-based and bio-based humic acid materials (CHA and BHA) from weathered coal and rice husk were industrially produced and studied their Pb(II) adsorption and immobilization characteristics and mechanisms in water and soil. The batch adsorption experiments obtained the Pb(II) adsorption by CHA and BHA both were spontaneous and endothermic monolayer chemisorption and controlled by three rate-limiting steps (bulk, film, and pore) in the adsorption process. CHA and BHA had highly efficient Pb(II) adsorption capacities, obtained their maximum adsorption capacity was 201 and 188 mg g−1, respectively. In addition to the two main adsorption mechanisms of ion exchange and surface complexation, electrostatic interaction, precipitation reaction, and π-π interaction were also involved. Soil culture experiments showed that CHA and BHA both exhibited a highly efficient immobilization effect on Pb(II)-contaminated soil, and CHA and BHA had a better synergistic promotion effect. Compared with the CK soil, the content of DTPA-Pb(II) decreased by 10.2–13.2% and the content of RES-Pb(II) increased by 14–22% in soils treated with different humic acids. Ion exchange, complexation, precipitation, and electrostatic attraction promote the transformation of unstable Pb(II) to stable Pb(II), which was of great significance for the immobilization of Pb(II) in soil. Overall, CHA and BHA have the potential to be used as green, efficient, and promising adsorbents to remove and immobilize Pb(II) from wastewater and soil.

Sodium humate based double network hydrogel for Cu and Pb removal

Sodium humate (SH) is one of the derivatives humic substances, which can be utilized for heavy metal removal from water due to its containing plenty of functional groups. In this study, a double network hydrogel SH/polyacrylamide (SH/PAM) was synthesized by a simple free-radical polymerization and used for Cu2+ and Pb2+ removal from water. The adsorption process can be well described by Langmuir-Freundlich model, indicating that both physical and chemical adsorption were involved. X-ray photoelectron spectroscopy (XPS) characterization demonstrated that complexation was the main mechanism for the adsorption. Two-dimensional correlation analysis of FTIR (2D-FTIR-COS) results showed that the variation order of functional groups during Cu2+ and Pb2+ adsorption in the following order: COOH ≈ –CO > –OH > C–O and –COOH ≈ C–O > –CO > –OH, respectively. According to the density functional theory (DFT) calculation results, the O atom of SH in the COO− was the main adsorption site. Meanwhile, the adsorption energy of Pb2+ was more negative than that of Cu2+ and the orbital hybridization between O atom of SH and Pb2+ was denser than that of Cu2+, which suggested that SH/PAM had a stronger combining capacity for Pb2+ than Cu2+. Therefore, the adsorption capacity for Pb2+ was larger than Cu2+. Moreover, the removal efficiencies are 30.2% for Al, 98.79% for Cu, 99.0% for Fe, 17.2% for Mn, 93.4% for Pb, and 62.4% for Zn in actual acid mine drainage using 6 g L−1 adsorbent. Collectively, this study not only provided a new adsorbent for heavy metal removal but also explicated the mechanism of heavy metal removal by SH from molecule and electron perspective, which is helpful for the application of SH in the environmental field.

Ferrate(VI) Synthesis Using Fe(OH)&lt;sub&gt;3&lt;/sub&gt; from Waste Iron Electrolysis and Its Application for the Removal of Metal Ions and Anions in Water

Ferrate(VI) salt is an effective oxidant and coagulant for water treatment and removal of metal ions. This study demonstrates a new approach to processing metal ions and anions in water by Fe(VI) through Fe(III) obtained from the electrolysis of waste iron transformer. The electrolysis was successfully carried out in the Na2SO4 electrolyte using waste iron and zinc plates as anode and cathode, respectively. Fe(III) electrolysis results through the characterization of FTIR and XRD indicate compliance with Fe(OH)3 standards. Synthesis of ferrate was carried out by adding Fe(III) from electrolysis with NaOCl in alkaline conditions. The formed ferrate solution shows a purple color with a typical maximum wavelength of 505 nm. Furthermore, the ferrate obtained is used to remove metal ions (Fe(III), Cu(II), Zn(II), Mg(II), Pb(II)) and anions (sulfate, nitrate, and carbonate) in water with pH variations. Ferrate treatment filtrate was analyzed using AAS for metal ions, while sulfate, nitrate, and carbonate anions used UV-Vis spectrophotometry, turbidimetry, and titration methods. The results showed that ferrate effectively eliminates metal ions and anions in water with optimum pH 6. The mechanism of heavy metal removal by ferrate(VI) can be explained by ionic bonding and adsorption.

Insight into the mechanism of heavy metal removal from water by monodisperse ZIF-8 fine particles

Water pollution due to toxic heavy metals discharged by chemical industries and abandoned mines is one of the most serious environmental and public problems. Therefore, the purification of heavy metal-contaminated water has become a major topic in water treatment. Among the metal–organic frameworks used to this aim, zeolitic imidazolate framework 8 (ZIF-8) is particularly promising as a purifying agent for water treatment. Although several reports have dealt with the purification of heavy metal-contaminated water using ZIF-8, the removal mechanism remains controversial. In this study, monodisperse ZIF-8 fine particles were used for the removal of Pb2+ and Cu2+ ions, and the removal mechanisms were investigated. Accordingly, an adsorption mechanism is suggested for the Pb2+ removal, whereas the Cu2+ removal occurs through an ion-exchange phenomenon.

Cleanup of arsenic, cadmium, and lead in the soil from a smelting site using N,N-bis(carboxymethyl)-L-glutamic acid combined with ascorbic acid: A lab-scale experiment

Chemical washing has been carried out to remediate soil contaminated with heavy metals. In this study, the appropriate washing conditions for N,N-bis(carboxymethyl)-L-glutamic acid (GLDA) combined with ascorbic acid were determined to remove As, Cd, and Pb in the soil from the smelting site. The mechanism of heavy metal removal by the washing agent was also clarified. The results showed that heavy metals in the soil from the smelting site can be effectively removed. The removal percentages of As, Cd, and Pb in the soil from the smelting site were found to be 34.49%, 63.26%, and 62.93%, respectively, under optimal conditions (GLDA and ascorbic acid concentration ratio of 5:20, pH of 3, washing for 60 min, and the liquid-to-solid ratio of 10). GLDA combined with ascorbic acid efficiently removes As, Cd, and Pb from the soil through synergistic proton obstruction, chelation, and reduction. GLDA can chelate with iron and aluminum oxides while directly chelate with Cd and Pb. Ascorbic acid can reduce both Fe(III) to Fe(II) and As(III) to As0. The dissolution of As was promoted by indirectly preempting the binding sites of iron and aluminum in the soil while those of Cd and Pb were improved by directly interrupting the binding sites. This study suggested that GLDA combined with ascorbic acid is an effective cleanup technology to remove As, Cd, and Pb simultaneously from contaminated smelting site soils.

Sequential Abatement of FeII and CrVI Water Pollution by Use of Walnut Shell-Based Adsorbents

In this study walnut shells, an inexpensive and readily available waste, were used as carbonaceous precursor for preparation of an innovative adsorbent (walnut-shell powder (WSP)) which was successfully tested for the removal of FeII from synthetic acid mine drainage (AMD). Then, the exhausted iron-contaminated adsorbent (WSP-FeII) was recovered and treated with sodium borohydride for the reduction of adsorbed FeII to Fe0. The resulting material (WSP-Fe0) was subsequently tested for the removal of CrVI from aqueous solutions. Treatability batch experiments were employed for both FeII and CrVI-contaminated solutions, and the influence of some important experimental parameters was studied. In addition, the experimental data was interpreted by applying three kinetic models and the mechanism of heavy metal removal was discussed. The overall data presented in this study indicated that fresh WSP and WSP-Fe0 can be considered as promising materials for the removal of FeII and CrVI, respectively. Furthermore, the present work clearly showed that water treatment residuals may be converted in upgraded materials, which can be successfully applied in subsequent water treatment processes. This is an example of sustainable and environmentally-friendly solution that may reduce the adverse effects associated with wastes and delay expensive disposal methods such as landfilling or incineration.

Influence mechanism of heavy metal removal under microcurrent action

Heavy metal pollution is widespread in the environment. Microbial fuel cell (MFC) technology is effective for heavy metal removal; however, the simultaneous variations of multiple parameters in an MFC make it difficult to fully elucidate the mechanism of heavy metal removal under microcurrent conditions. In this study, we used a potentiostat to control the fixed potential in a simulated MFC system. The effects of pH, potential, and heavy metal concentration on current, heavy metal removal rate, product type, and product morphology were studied through orthogonal testing. The mechanism and significance of each parameter in terms of copper reduction removal were analyzed using tests of between-subjects effects and correlation analysis. We found that: (1) potential did not affect the type of electron acceptor, and substances with high redox potentials preferentially received electrons; (2) copper concentration significantly affected the reduction rate and product particle size of copper by controlling the flux of electroactive substances transferred to the electrode surface; (3) the combined effects of higher pH and copper concentration limited the reduction of copper; (4) current was the most important factor controlling copper reduction, as current strength significantly affected the copper reduction rate and mechanism; and (5) pH and copper concentration significantly affected the current level by altering the ionic strength of the solution.

Adsorption mechanisms for heavy metal removal using low cost adsorbents: A review

A review of adsorption mechanisms for heavy metal removal using low cost adsorpthas been carried out in this article. Some metal ion sequestration techniques used over the years have some demerits, ranging from generation of sludge to high operational cost. Adsorption process using low cost adsorbents has been found cost effective and environmentally nuisance-free. In this review, various low cost adsorbents for heavy metal sequestration have been studied. The application of some adsorption models such as single and multi-component isotherms, adsorption thermodynamics, and kinetics as well as the effect of process parameters on heavy metal sequestration using low cost adsorbents has also been reviewed so as to better understand the adsorption process. From the literature reviewed, the percentage removal of chromium, copper and zinc was favoured by an increase in contact time, temperature, initial concentration, adsorbent dosage as well as a decrease in pH.

Removal of Zn(II), Mn(II) and Cu(II) by adsorption onto banana stalk biochar: adsorption process and mechanisms.

Low-cost banana stalk (Musa nana Lour.) biochar was prepared using oxygen-limited pyrolysis (at 500 °C and used), to remove heavy metal ions (including Zn(II), Mn(II) and Cu(II)) from aqueous solution. Adsorption experiments showed that the initial solution pH affected the ability of the biochar to adsorb heavy metal ions in single- and polymetal systems. Compared to Mn(II) and Zn(II), the biochar exhibited highly selective Cu(II) adsorption. The adsorption kinetics of all three metal ions followed the pseudo-second-order kinetic equation. The isotherm data demonstrated the Langmuir model fit for Zn(II), Mn(II) and Cu(II). The results showed that the chemical adsorption of single molecules was the main heavy metal removal mechanism. The maximum adsorption capacities (mg·g-1) were ranked as Cu(II) (134.88) > Mn(II) (109.10) > Zn(II) (108.10)) by the single-metal adsorption isotherms at 298 K. Moreover, characterization analysis was performed using Fourier transform infrared spectroscopy, the Brunauer-Emmett-Teller method, scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results revealed that ion exchange was likely crucial in Mn(II) and Zn(II) removal, while C-O, O-H and C = O possibly were key to Cu(II) removal by complexing or other reactions.

Insights to the transport of heavy metals from an industrial effluent through functionalized bentonite incorporated mixed matrix membrane: Process modeling and analysis of the interplay of various parameters

Ethylene diamine tetraacetic acid (EDTA) was immobilized on bentonite clay particles by single step synthesis process and the prepared functionalized bentonite (FB) particles were incorporated in polysulfone membrane. The FB particles made the membrane surface negative (zeta potential of M-2 membrane having 2 wt% FB was –22 mV at pH 7) facilitating adsorption of heavy metals. They imparted hydrophilic properties to the mixed matrix membrane (MMM) indicated by the reduction of contact angle which in turn reduced membrane fouling. M-2 membrane exhibited the highest permeability 7.4 × 10-11 m/Pa.s and metal ion removal in the range of 92–98 % for Ni (II), Cu (II), Zn (II) and Pb (II). Among the heavy metals studied, lead showed the maximum retention. FT-IR study precisely indicated the presence of chemical interaction among FB particles and polymer matrix thus, restricting the leaching of additives from the membranes. The mechanism of heavy metal removal by MMM was identified as adsorption promoted by ion-exchange. The MMM exhibited about 98% lead rejection and breakthrough time of 9 h for a battery effluent. A first principle-based modified convection-adsorption model was utilized to predict both the permeate flux and concentration profiles for a long term filtration experiment. The same model was used to generate a performance curve for scaling up of a real industrial wastewater to identify the suitable operating conditions and the membrane area. An in-depth analysis of the parameter space was carried out to establish the inter-relation between various parameters, like, membrane resistance and membrane-solute interaction variables (adsorption capacity, adsorption kinetic constant and adsorption resistance parameter). This analysis would be helpful in making a MMM with desirable properties for an optimal performance.

Advances in heavy metal removal by sulfate-reducing bacteria.

Industrial development has led to generation of large volumes of wastewater containing heavy metals, which need to be removed before the wastewater is released into the environment. Chemical and electrochemical methods are traditionally applied to treat this type of wastewater. These conventional methods have several shortcomings, such as secondary pollution and cost. Bioprocesses are gradually gaining popularity because of their high selectivities, low costs, and reduced environmental pollution. Removal of heavy metals by sulfate-reducing bacteria (SRB) is an economical and effective alternative to conventional methods. The limitations of and advances in SRB activity have not been comprehensively reviewed. In this paper, recent advances from laboratory studies in heavy metal removal by SRB were reported. Firstly, the mechanism of heavy metal removal by SRB is introduced. Then, the factors affecting microbial activity and metal removal efficiency are elucidated and discussed in detail. In addition, recent advances in selection of an electron donor, enhancement of SRB activity, and improvement of SRB tolerance to heavy metals are reviewed. Furthermore, key points for future studies of the SRB process are proposed.

Intimate communication between Comamonas aquatica and Fusarium solani in remediation of heavy metal-polluted environments.

Worldwide, humanity is facing a major environmental crisis with the disposal of heavy metal contaminated waste. The current study describes, for the first time, the interactions between gram-negative Comamonas aquatica and filamentous fungus Fusarium solani in removing heavy metal toxicity as an eco-friendly system. When combined, C. aquatica and F. solani grew well in a co-culture setup without showing any antagonistic indications. Monoculture versus co-culture setups were used to determine the metal tolerance concentration (MTC). Based on the metal tolerance concentration (MTC) values, cells of C. aquatica were able to tolerate 4, 5, 6, and 7mM of Cr, Zn, Cu, and Ni, respectively. Moreover, C. aquatica withstood up to 6mM of Pb. Although F. solani exhibited sensitivity to high concentrations of heavy metals in monoculture, the MTC of F. solani increased considerably in a co-culture setup. The results presented here revealed that F. solani facilitated the dispersion of C. aquatica and heightened bioavailability, whereas C. aquatica reduced the toxicity of heavy metals and promoted the growth of F. solani. Transmission electron microscopy (TEM) displayed different mechanisms for heavy metal removal by C. aquatica. Biosorption was evident for Cr and Pb, while transformation was recorded for Ni and Zn. Also, C. aquatica was able to reduce and accumulate Cu in cells.

The removal of Cu, Ni, and Zn in industrial soil by washing with EDTA-organic acids

In order to improve the heavy metal removal ability of traditional single washing agents and explore the removal mechanism of heavy metals. Then, the washing reagents that mixed by low-molecular weight organic acids (citric acid, oxalic acid, and tartaric acid) and artificial chelating compound ethylenediaminetetraacetic acid disodium (EDTA) were selected. Furthermore, the effect of soil washing parameters, the variation of leaching toxicity, mobility, stability and speciation of heavy metals were also considered. The results of soil washing experiments showed that mixing an equal volume of 0.05 M EDTA and 0.2 M organic acids (citric acid, oxalic acid, and tartaric acid) could remove more than about 80% heavy metals from soil under the optimal conditions. In addition, the soil leaching toxicity was decreased and the stability of remaining heavy metals was increased, indicating that EDTA-organic acid washing reagents could effectively reduce the ecological risk of contaminated soil. EDTA had a stronger chelating ability with heavy metals than the organic acids, and the organic acids could not only chelate heavy metals but also decrease the pH of the mixture for promoting the desorption of heavy metals. Thus, mixing EDTA and organic acids was advisable method to improve soil washing technology.