Removal Of Toxic Metals Research Articles

Sequential Bioleaching of Pyritic Tailings and Ferric Leaching of Nonferrous Slags as a Method for Metal Recovery from Mining and Metallurgical Wastes

In this work, we proposed a method for biohydrometallurgical processing of mining (old pyritic flotation tailings) and metallurgical (slag) wastes to recover gold and other nonferrous metals. Since this processing allows the removal of toxic metals or at least decreases their content in the solids, this approach may reduce the negative environmental impacts of such waste. The proposed process was based on pyritic tailings’ bioleaching to recover metals and produce leach liquor containing a strong oxidizing agent (ferric sulfate) to dissolve nonferrous metal from slag. This approach also allows us to increase concentrations of nonferrous metals in the pregnant leach solution after pyritic waste bioleaching to allow efficient extraction. The old pyritic tailings were previously leached with 0.25% sulfuric acid for 10 min to remove soluble metal sulfates. As a result, 36% of copper and 35% of zinc were extracted. After 12 days of bioleaching with a microbial consortium containing Leptospirillum spp., Sulfobacillus spp., Ferroplasma spp., and Acidithiobacillus spp. at 35 °C, the total recovery of metals from pyritic tailings reached 68% for copper and 77% for zinc; and subsequent cyanidation allowed 92% recovery of gold. Ferric leaching of two types of slag at 70 °C with the leachate obtained during bioleaching of the tailings and containing 15 g/L of Fe3+ allowed 88.9 and 43.4% recovery of copper and zinc, respectively, from copper slag within 150 min. Meanwhile, 91.5% of copper, 84.1% of nickel, and 70.2% of cobalt were extracted from copper–nickel slag within 120 min under the same conditions.

Fabrication of calcite based biocomposites for catalytic removal of heavy metals from electroplating industrial effluent

Treatment of wastewater for heavy metal removal is gaining much attention due to increase in pollution and insufficiency of water. Wastewater treatment processes is important in preventing heavy metal pollution of the receiving waters when discharged particularly from industrial effluents including electroplating industries. In this article, a novel actinobacterium Zhihengliuella sp. ISTPL4, along with different biomaterials synthesized were studied comprehensively for the removal of toxic heavy metals including Cr, Cd, Mn, Ni, Pb, Zn and Fe. Among these heavy metals, Cr(VI) being more lethal than other metal ions and present in a very high concentration of ⁓1000 mg/l in effluent of electroplating industry, pose serious health issues when enters the body. Cr(VI) reduction by the strain ISTPL4 when studied in the reactor, showed 20 % reduction of Cr(VI) to Cr(III) at an initial concentration of 1100 mg/L, along with >90 % removal of other heavy metals. The whole genome analysis of the strain showed the presence of heavy metals resistant genes and transporters, corroborating the above results. The bacterium’s adsorption capacity was then compared with synthesized biomaterials viz. only biochar, biochar with reductase enzyme, and calcined biochar with reductase enzyme. Synthesized biomaterials in the packed columns provided excellent adsorption capacity for all the heavy metals within 10–15​ min of run time and reusability potential of 5 cycles. Calcined biochar with reductase enzyme showed maximum adsorption of Cr. Langmuir isotherm and Lineweaver Burk plot best explained their adsorption mechanism and strong affinity towards heavy metals. FTIR and SEM-EDX analysis confirmed the involvement of carboxyl, hydroxyl, and amino groups in heavy metal ions’ biosorption. Furthermore, MTT assay in HepG2 showed greatest cell viability at the concentration where maximum reduction of Cr(VI) to Cr(III) occurred. We propose this current technology, which provides an excellent biosorbent in the form of calcined biocomposite with bacterial reductase enzyme for heavy metals reduction and remediation and also implementation of this technique would have great significance in wastewater treatment of metal contaminated sites.

Synthesis of iron-based magnetic nanocomposites and applications in adsorption processes for water treatment: a review

Rising worldwide concern about the quantity and quality of water available to living beings calls for efficient technologies of water treatment. Nanomaterials are promising adsorbents to remove contamination from aqueous solution, and magnetic nanomaterials based on iron have attracted attention because magnetic materials are easy to separate. Here, we review iron magnetic nanomaterials applied for water and wastewater treatment, with focus on toxic elements, pharmaceuticals and pesticides. Major advances are: coprecipitation is the most used method for synthesis of iron magnetic nanoparticles, followed by solvothermal and hydrothermal methods. Magnetite is the most common magnetic nanoparticles applied as magnetic adsorbent. In general, magnetic nanocomposites are superparamagnetic, and the highest magnetization is sought for core–shell structures, reaching 65 emu/g. Most reports focus on removal of toxic metals. Adsorption is explained by the Langmuir isothermal model, kinetic patterns being correlated with pseudo-second-order equations. Overall, iron-based magnetic nanocomposites display promising performances for pollutant removal, yet few investigations report the toxic impacts of magnetic nanoparticles on the environment.

A functionalized nanocomposite adsorbent for the sequential removal of radioactive iodine and cobalt ions in aqueous media

The need for efficient remediation of the radioactive waste caused by undesirable nuclear accidents and overspending of radionuclides has gained worldwide attention, with extensive recent efforts made to protect the environment from radioactive contamination. Although various treatment processes for the removal of radionuclides and the purification of liquid waste have been reported, the development of a better decontamination method is still necessary for obtaining enhanced desalination performances. Herein, we report a dual-functional composite adsorbent composed of a cellulose acetate membrane as a solid support, gold nanoparticles (AuNPs), and a metal chelating agent which can potentially be used to efficiently remove radioactive iodine and cobalt. In the desalination experiments, the sorption membrane was able to remove cobalt ions rapidly in water. Isotherm data shows that approximately 180 Co2+ atoms were captured per AuNP. Next, the same material was used for the adsorption of iodide anions. Within a few minutes, more than 99% of radioactive iodine was removed even in the presence of other ion species. These findings clearly demonstrate that the desalination method presented in here provides a useful approach for the sequential removal of toxic metal and halogen species in aqueous media.

Biosorption and removal of toxic heavy metals by metal tolerating bacteria for bioremediation of metal contamination: A comprehensive review

Heavy metal pollution caused due to the industrialization has been considered as a significant public health hazard, and these heavy metals exhibit various types of toxicological manifestations. Conventional remediation methods are expensive and also yield toxic by-products, which negatively affect the environment. Hence, a green technology employing various biological agents, predominantly bacteria, algae, yeasts, and fungi, has received more attention for heavy metal removal and recovery because of their high removal efficiency, low cost, and availability. However, bacterial biosorption is the safest treatment method for the toxic pollutants that are not readily biodegradable such as heavy metals. Metal biosorption by bacteria has received significant attention due to a safe, productive, and feasible technology for the heavy metal-containing wastewater treatment. These metal tolerating bacteria can bind the cationic toxic heavy metals with the negatively charged bacterial structures and live or dead biomass components. Due to the large surface area to volume ratio, these bacterial biomasses efficiently act as the biosorbent for metal bioremediation under multimetal conditions. This review summarizes the biosorption potentials of bacterial biomass towards different metal ions, cell wall constituent, biofilm, extracellular polymeric substances (EPS) in metal binding, and the effect of various environmental parameters influencing the metal removal. Suitable mathematical models of biosorption and their application have been discussed to understand and interpret the adsorption process. Furthermore, different desorbing agents and their utilization in heavy metals recovery and regeneration of biosorbent have been summarized.

Removal of toxic heavy metals, phenolic compounds and textile dyes from industrial waste water using phosphonium based ionic liquids

This article focused on a comprehensive result of the development of three phosphonium based room temperature ionic liquids (RTILs) of same cation, trihexyltetradecylphosphonium ([PC6C6C6C14]), with different organic or inorganic anions viz. [Cl-] chloride dicyanamide [-N(CN)2−] and bis (trifluoromethyl sulfonyl) amide [-NTf2−] in extraction processes of toxic textile dyes as rhodamine B, methylene blue, methyl orange, malachite green, alizarin red S and congo red dyes from their aqueous solution, harmful heavy metals include As, Cr, Cd, Cu, Zn, Pb and Hg from their standard solutions AS(NO3)3, Cr(NO3)3, Cd(NO3)2, Hg(NO3)2, Pb(NO3)2, Zn(NO3)2 & Cu(NO3)2 respectively and phenolic compounds from rice and cashew industrial waste water. In technological front, ILs revealed a potential ability for the removal of dyes, heavy metals and phenolic compounds owing to their hydrophobic nature on investigating via liquid –liquid extraction method. The effect of contact time, solution pH and initial concentration of dyes were investigated and the result show that adsorption of dyes increases with increasing contact time and gets maximum decolourisation at acidic pH and pH 7. The extraction process of heavy metals with the ILs were investigated and were assessed using the techniques UV–Visible spectroscopy and ICP-MS (Inductive Coupled Plasma Mass Spectroscopy). The three ILs showed best extraction efficiency (approx. 100%) for all heavy metals and the dyes using proposed methodology. UV–Visible Spectroscopy quantification method was employed to analyse extracted phenolic compounds. Screening results of phenolic compounds have shown that [PC6C6C6C14][Cl] IL exhibited the capacity intake of 100% efficiency from rice and cashew industrial waste water. The ILs were characterized with thermogravimetry (TGA) and from which, the samples showed a good thermal stability up to 573 K to project them as promising one for high temperature needs in various technological fronts. Toxicity risks of the three ILs and the textile dyes used were examined by in silico OSIRIS software calculations and the ILs were found to be non-toxic.

A new local adsorbent for the removal of toxic metals from industrial wastewater

The ability of light expanded clay aggregate from Shat al-Khora in the city of Basrah to remove heavy metal ions Cr(VI), Zn(II), Cu(II) and Fe(III) from industrial wastewater in the State Company of Petrochemical industries was studied in a batch mode adsorption process. The effects of process variables including: pH, adsorbent dose, contact time, adsorbent particle size and temperature were investigated. The results showed that the maximum removal percentage of Cr(VI), Zn(II), Cu(II) and Fe(III) ions was achieved at a pH values of 2 and 5 for Cr(VI) and Zn(II) ) respectively and at 4.5 for both Cu(II) and Fe(III). The experimental data were fitted using Langmuir and Freundlich adsorption isotherm models. The results indicated that the adsorption of Cr(VI), Zn(II) and Cu(II) matched with Langgmuir model while for Fe(III) it fitted Freundlich model. Five kinetic reaction models were tested for fitting the experimental data, the results analysis showed successful fitting with the 1st and the 2nd pseudo models for all the heavy metal ions investigated.

Conventional and Current Methods of Toxic Metals Removal from Water Using g-C3N4-Based Materials

The concentration of toxic metal ions in wastewater continues to increase as a result of the increasing number of industries, and the discharge of their heavy metal-containing wastes directly into water bodies without proper treatment. These heavy metals are highly toxic and difficult to degrade, which makes the treatment and re-use of the wastewater to be very challenging. Several methods have been explored for their removal from water in order to improve on water availability. However, these conventional methods cannot transform the heavy metal ions to a less toxic species, instead they are transferred from one phase to another, which may lead to secondary pollution. In this review, the conventional techniques that have been explored for the removal of heavy metal ions were examined and their merits and demerits were highlighted. Recent advancement involving the use of composites containing graphitic carbon nitride photocatalysts were discussed as viable alternative for the conventional methods. The mechanism of photocatalytic removal of heavy metal ions and methods of synthesizing the g-C3N4 composites were discussed. Furthermore, the chemistry of heavy metal ion transformation, their toxicity and routes of exposure were studied. Finally, the problems associated with the fabrication of the composites were critically examined.

Removal of toxic metals using a novel PHA resin-fixed bed column performance study

The performance and efficiency of a fixed bed column loaded with a three-dimensionally crosslinked polyhydroxamic acid resin is studied with glass column. Experiments were carried out with synthetic metal solutions containing Cu(II), Sr(II), Gd(III) individually and with mixed solution containing Cu(II), Sr(II), Gd(III) and U(VI) to establish the efficiency of the fixed bed resin for a mixed solution. The “S” shaped break through curve was generated and percentage saturation of the bed was estimated. The percentage saturation at 10% breakthrough volume was found to be 68.3% for Cu(II) and Sr(II) 71.3% and 65.6% for Gd(III).

;Valorisation of banana peels by hydrothermal carbonisation: Potential use of the hydrochar and liquid by-product for water purification and energy conversion

Banana peels were used as feedstock to produce a carbon dense hydrochar for the removal of toxic metals from wastewater. Compared to the biomass feedstock (41.3% mass C), the banana peel hydrochar possesses higher carbon (54–72% mass C) and lower ash contents. The carbonised banana peels treated between 150 and 300 °C (1−2h) demonstrated an excellent ability to remove Cd2+ (5–100 mg L−1), achieving 99% removal, in comparison with 75% for the raw peel. The liquid by-product generated in the carbonisation process was tested as feedstock in microbial electrochemical devices, showing significant reduction in the chemical oxygen demand levels (initially 10–25 103 mg L−1), associated with the production of electrical outputs; 81–85% reduction with microbial communities from compost, and 53–85% with anaerobic sludge. The results demonstrate the complete utilization of waste from mass cultivation of banana, providing a full-cycle solution for the pollution associated to this important crop.

Sulfamic acid functionalized slag for effective removal of organic dye and toxic metal from the aqueous samples

Surface functionalization of blast furnace slag with sulfamic acid (a zwitterion) was performed for the removal of Cr 3+ and methylene blue dye (MB) from water samples. The slag functionalization process was optimized using Response Surface Methodology Design. Statistical analysis of the parameters that include the sulfamic acid amount (A), reaction time (B), and temperature (C) revealed that (A) increase had a negative effect on the adsorption of both pollutants by the zwitterion slag, whereas (B) and (C) increase presented a positive impact. At the optimum condition of 2 g sulfamic acid amount, 50 min reaction time and 37 °C temperature, the prepared slag showed a removal efficiency of more than 90% for both Cr 3+ and MB. Surface characterization by SEM/EDS, FTIR, XPS and surface area analyser, showed an improvement in surface properties and the incorporation of zwitterionic NH 2 + and S O groups of sulfamic acid. Adsorption isotherm and kinetic studies conducted with the zwitterion slag showed the adsorption process was suited to Freundlich isotherm model and pseudo-second-order kinetic model. The thermodynamic study conducted revealed the spontaneity of the process based on the calculated negative Δ G (Gibb’s free energy) values. The prepared zwitterion slag offered easy regeneration with dilute HCl solution and showed a considerable removal (Cr 3+ : 65% and MB: 80%) for both pollutants even after 3 cycles of usage.

Sorption of Cd(II) and Pb(II) ions by Nanolimestone from underground water samples from Tehama region of Saudi Arabia

Powdered Nano limestone (NLS) has been investigated as an un-expensive adsorbent for heavy toxic metals removal from aqueous solutions as cadmium and lead. Batch experiments were carried out, The favorable pH for maximum metals adsorption was at 6.8 for both. The surface area increased in case of NLS up to 6.2 m2/g. The adsorption capacity calculated by Langmuir equation was 75.1 mg/g for Cd(II) and 68.4 for Pb(II) ions at pH 6.8. The adsorption capacity increased with temperature and the kinetics followed a First-order rate equation for both. The enthalpy change (ΔH0) was 25.4 Jmol−1 for Cd(II) and 20.8 Jmol−1 for Pb(II), while entropy change (ΔS0) was 41.6 JK-1mol-1 for Cd(II) and 38.7 JK-1mol-1 Pb(II), which indicate that adsorption process was endothermic and spontaneous in nature. About 25 collected samples of groundwater were tested and found to be contaminated with cadmium and lead elements with different rates, with using NLS as adsorbent able to remove both metals from the samples. All of the results suggested that the NLS is excellent nano-adsorbents for cadmium and lead contaminated water samples.

Bio-sorption of toxic metals from industrial wastewater by algae strains Spirulina platensis and Chlorella vulgaris: Application of isotherm, kinetic models and process optimization

The present study evaluates the effect of an acidic treatment on the improvement of the percentage removal of toxic metal (%TMrem) from wastewater by algae strains (Spirulina platensis (SP) and Chlorella vulgar (CV)) under different adsorbent dosages (0.2–2.5 g), a pH of (4–8) and contact time (5–100 min). The acidic treatment (Ac-T) altered the functional groups on the surface of algae promoting more electronegative groups and improved the %TMrem of Al, Ni and Cu. Treated SP removed up to 95.0 ± 0.3% (Std. Dev = 0.24), 87.0 ± 0.2% (Std. Dev = 0.34)%, and 63.0 ± 0.3% (Std. Dev = 0.14) of Al, Ni, and Cu at the optimum pH of 5.5, 6.0, and, 7.0 and an adsorbent dosage of = 2.5 ± 0.1 g/L (Std. Dev = 0.14) g/L, respectively. Lower %TMrem of 87.0% ± 0.2 (Std. Dev = 0.09), 79.1 ± 0.4% (Std. Dev = 0.08), and 80.0 ± 0.2% (Std. Dev = 0.04) were achieved with treated CV, respectively. The optimum operational conditions for maximum %TMrem were determined at (Calgae = 4.8 ± 0.2 gMNPs.L−1, Ct = 88 ± 1, and pH = 6) using the response surface methodology (RSM). The adsorption of TMs on algae is endothermic, spontaneous, and follows Langmuir and second-order kinetics. Zeta potential measurements indicated that the adsorption mechanism between the toxic metal (TM) and algal strains is controlled by electrostatic interaction. As such, bio-sorption is a sustainable and efficient technology for the removal of TM from wastewater.

Investigation on Cadmium Ions Removal from Water by a Nanomagnetite Based Biochar Derived from Eleocharis Dulcis

Poor separation of powdered biochar from the liquid phase during toxic heavy metals adsorption poses serious environmental and human health challenges. The current study therefore investigated the removal of toxic heavy metal i.e., cadmium using a magnetically modified biochar derived from Eleocharis dulcis to combine its easy separation from liquid phase with enhanced adsorption capacity obtained from Eleocharis dulcis biochar. The synthesized adsorbent was characterized by using various characterization techniques and its performance for cadmium adsorption was studied at varying parameters of time, temperature, pH and concentration. Both equilibrium and kinetic studies were performed at 30, 35, 40 and 45 °C. The equilibrium data was subjected to Langmuir equation and the thermodynamic parameters like ∆S°, ∆H° and ∆G° were calculated. The kinetic data fitted well to pseudo second order equation and the activation energy was calculated by using Arrhenius equation. The adsorption capacity of cadmium was found to be higher on the surface of magnetite biochar derived from Eleocharis dulcis as compared to many of the reported adsorbents proving it to be an effective adsorbent to remove cadmium from aqueous solutions.

Toxic heavy metal removal from sulfide ores using potassium permanganate: Process development and waste management

A monolithic new attitude utilizing Aspen Plus software and Taguchi method has been applied to evaluate a novel configuration for removal of toxic heavy metals during sulfide ores recovery using potassium permanganate (KMnO4). In this new configuration, KMnO4 has been produced by sludge recovery of cobalt purification step containing manganese (IV) oxide (MnO2). Also, in this suggested configuration, the required sulfuric acid (H2SO4) solvent has been provided by recovery of sulfur compounds released during leaching process of sulfide ores. The optimum condition obtained by Taguchi experimental design has been used as initial data for the simulation and sensitivity analysis of process via Aspen Plus software. A systematic study of the design and operating condition has been made for key performance metrics such as removal of toxic heavy metal from sulfide ores, recovery of KMnO4 from sludge containing MnO2 and conversion of released sulfide gases to H2SO4 at the different operating condition such as H2SO4 concentration of 60–90 g/L, operating temperature of 60–150 °C, agitation rate of 100–400 rpm, reaction time of 0.5–2 h, solid to liquid ratio of 1:1–1:4, particle size of 10–500 μm, additive amount of 10–40 wt% and oxygen pressure of 0.5–2 MPa. The optimum condition for removal of toxic heavy metal have been found to be H2SO4 concentration of 70 g/L, temperature of 90 °C, agitation rate of 200 rpm, reaction time of 1.5 h, particle size of 500 μm, solid to liquid ratio of 1:2, additive amount of 40 wt% and oxygen pressure of 1.5 MPa. According to simulation results, the maximum conversion of released sulfide gases to H2SO4, recovery of KMnO4 and toxic heavy metals removal during designed process at optimized condition are 98%, 91% and 99%, respectively.

Pyrogenic carbon for decontamination of low-level radioactive effluents: Simultaneous separation of 137Cs and 60Co

Radiocesium (137Cs) and radiocobalt (60Co) represent main dose-significant radionuclides in low-level radioactive liquid effluents released from commercial nuclear power plants (NPPs). Although pyrogenic carbon-based adsorbents (biochars, BC) have been studied for toxic metal removal, the reports of their use in the adsorption of radionuclides are rare. This article focuses on the competitive removal of Cs+ and Co2+ ions from radioactive solutions to waste biomass derived biochar and the multi-component isotherms. BC exhibited a good affinity to both Cs and Co, and in single-component systems the maximal adsorption capacity Qmaxexp reached 97.4 ± 5.0 (Cs+) and 74.5 ± 0.4 μmol g−1 (Co2+). 3D adsorption surfaces obtained by Sheindorf-Rebuhn-Steintuch (SRS) and extended Freundlich models indicate that the sorption of Cs+ ions from the Cs–Co binary system is significantly affected by Co2+ ions and during the adsorption competitive and interaction effects between Cs+ and Co2+ ions occur. Moreover, mono- and divalent cations present in the solution acted as competing ions, decreasing the Kd values. SEM-EDX maps, FTIR and XPS spectra confirmed that both biochar mineral and carbon fraction participated in Cs and Co immobilization. Beside interactions of Cs+ and Co2+ ions with O-containing moieties on the biochar surface (chemisorption), mineral components and porosity of BC (physisorption) were involved in both Cs and Co removal. Finally, the adsorption loading and fast kinetics for both Cs and Co indicate suitability of biochar to decontaminate low-level radioactive effluents contaminated by 137Cs and 60Co.

Removal of Heavy Metal Ion Using Polymer-Functionalized Activated Carbon: Aspects of Environmental Economic and Chemistry Education

Numerous countries have shown signs of environmental pollution to prioritize economic growth and benefits, leading to seriously contaminated waters. This work indicated the method to synthesize a green material, which could remove contaminants to protect the natural environment. The porosity and functionality effects of amine-functionalized activated carbon (AFAC) enhanced the removal of toxic heavy metals (THMs) in aqueous solution. The raw activated carbon (RAC) was thermally modified with ultrahigh pure nitrogen (UHPN) at 500°C and 1000°C and then amine-functionalized with coupling agent of aminopropyltriethoxysilane (APS). They were denoted as AFAC-5 and AFAC-10, respectively. The data showed an enhanced metal adsorption capacity of the AFACs, because the modification produced more desired porosity and increased amine functional groups. AFAC-10, modified at a higher temperature, showed much higher THM adsorption capacity than AFAC-5, modified at a lower temperature, and RAC. The adsorption capacity decreased in the following order: Ni > Cd > Zn, which was in good agreement with the increasing electronegativity and ionic potential and the decreasing atomic radius. The maximum THM adsorption capacity of AFAC-10 for Ni, Cd, and Zn was 242.5, 226.9, and 204.3 mg/g, respectively.

Efficient conversion of bicarbonate (HCO3−) to acetate and simultaneous heavy metal Cr(VI) removal in photo-assisted microbial electrosynthesis systems combining WO3/MoO3/g-C3N4 heterojunctions and Serratia marcescens electrotroph

The removal of the hazardous heavy metal Cr(VI) in water and the simultaneous production of acetate from the reduction of inorganic carbon (HCO3−) is demonstrated in a photo-assisted microbial electrosynthesis (MES) system incorporating WO3/MoO3/g-C3N4 Z-scheme heterojunctions and Serratia marcescens Q1 electrotroph cathode. The rates of acetate production (6.1 ± 0.3 mg/L/h) and Cr(VI) removal (4.5 ± 0.1 mg/L/h) recorded at a circuital current of 2.8 ± 0.1 A/m2 were 2.4-fold (acetate production), 1.7-time (Cr(VI) removal) and 1.6-fold (circuital current) of those in the controls recorded in the absence of WO3/MoO3/g-C3N4, and 1.6-fold (acetate production) and 1.8-time (circuital current) of those in the absence of both Cr(VI) and WO3/MoO3/g-C3N4. Photogenerated WO3/MoO3/g-C3N4 conduction bands electrons favored both direct or indirect (via S. marcescens) reductions of Cr(VI) and H+, with the latter producing H2 which was further metabolized by S. marcescens with HCO3− to yield acetate. The higher circuital current drawn under photoirradiation conditions refilled the photo-generated valence band holes in the semiconductor and provided the driving force for the reduction reactions. This study provides an alternative and feasible approach for achieving complete removal of toxic heavy metal from water and industrial waters with simultaneous conversion of inorganic carbon to key block chemicals.

Removal of lead and other toxic metals in heavily contaminated soil using biodegradable chelators: GLDA, citric acid and ascorbic acid

In this study, we investigated the level of contamination of agricultural soil near an old recycling lead smelter in Vietnam and proposed an effective treatment for the remediation of the soil. The analysis of soil samples using an ICP-MS method revealed that the soil in the area was heavily contaminated by heavy metals, especially lead (Pb) with concentrations in surface soil of >3000 μg g−1. High concentrations of metals, including Pb, copper (Cu) and zinc (Zn), were found in whole soil profile. The FE-EPMA and Laser-Raman spectrometer results suggested that iron minerals and carbon materials in the soil are the important hosts of the toxic metals. Subsequently, a series of washing experiment were performed on the soil using biodegradable chelators, including N, N-dicarboxymethyl glutamic acid tetrasodium salt (GLDA), ascorbic acid and citric acid. The results showed that the mixture of GLDA-ascorbic (100 mM: 100 mM) can be considered as a potential candidate for Pb and Zn removal, which removes approximately 90% of Pb and 70% of Zn. Meanwhile, a mixture of GLDA-citric would be preferred for Cu removal based on its greater extraction efficiency compared to other mixtures.

Application of a dealginated seaweed derivative for the simultaneous metal ions removal from real and synthetic effluents

In this study, the alginate extraction residue (RES) from Sargassum filipendula was employed as biosorbent for the simultaneous removal of Cr3+, Ni2+ and Zn2+ from ternary synthetic solutions and for the decontamination of industrial (leather industry) and urban real effluents that were collected from different areas of Strasbourg (France). For this purpose, biosorption experiments in batch mode, multimetals equilibrium isotherms fitting and biosorbent characterization were carried out. In synthetic effluents, RES exhibited a greater affinity for Cr3+ ions, while a still unknown affinity for Al3+ and Pb2+ was verified for real conditions, reaching up to 80 % removal in some cases. At equilibrium, the higher sorption capacities were found at 50 °C as 0.864, 0.302 and 0.347 mmol/g for Cr3+, Zn2+ and Ni2+, respectively. Regarding the equilibrium models fitting, just the Extended Langmuir equation was able to describe the experimental data, showing an increase in qmax as the temperature rose, besides a decay in KL,1, KL,2 and KL,3 at the higher temperatures that indicates a weakening of adsorbent-adsorbate interactions. The characterization analyzes revealed a complex biosorption with a depth participation of carboxylic and hydroxyl groups was revealed by the characterization analyses, whereas the ion exchange mechanism played a really important role. The cation exchange capacity of RES was quantified as 34.12 mg/gRES with main exchangeable position of Ca2+ and Na+ ions. Based on these results, RES could be used as a novel and efficient biosorbent for toxic metals removal even from quite diluted real effluents, contributing to its valorization.