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Microbiologically induced calcite precipitation (MICP), as a newly developing bioremediation technology, could redeem heavy metal contamination in diverse scenarios. In this study, MICP bacterium Sporosarcina ureilytica ML-2 was employed to suppress the pollution of Pb, Cd and Zn in municipal sludge nutrient soil. After MICP remediation, the exchangeable Cd and Zn in sludge nutrient soil were correspondingly reduced by 31.02 % and 6.09 %, while the carbonate-bound Pb, Cd and Zn as well as the residual fractions were increased by 16.12 %, 6.63 %, 13.09 % and 6.10 %, 45.70 %, 3.86 %, respectively. In addition, the extractable Pb, Cd and Zn either by diethylenetriaminepentaacetic acid (DTPA) or toxicity characteristic leaching procedure (TCLP) in sludge nutrient soil were significantly reduced. These results demonstrated that the bio-calcite generated via MICP helped to immobilize heavy metals. Furthermore, MICP treatment improved the abundance of functional microorganisms related to urea cycle, while reduced the overall abundance of metal resistance genes (MRGs) and antibiotic resistance genes (ARGs). This work confirmed the feasibility of MICP in remediation of heavy metal in sludge nutrient soil, which expanded the application field of MICP and provided a promising way for heavy metal pollution management. [Display omitted] • MICP tech could improve the stability of Pb, Cd and Zn in sludge nutrient soil. • The exchangeable Cd reduced by maximum 31.2 % contents after MICP remediated. • The carbonated and residual contents of Pb, Cd and Zn increased after remediated. • The extracted contents of DTPA & TCLP-Pb, Cd and Zn were reduced after remediated. • MICP improved the abundance of functional microbes and reduced resistance genes. [ABSTRACT FROM AUTHOR]

Understanding the main drivers that affect the spread of antibiotic resistance genes (ARGs) during the composting process is important for the removal of ARGs. In this study, three levels of tylosin (25, 50, and 75 mg kg –1 on a dry weight basis) were added to swine manure plus a control, which was composted with cotton stalks. Each treatment was repeated in triplicate and the ARG profiles were determined with different levels of tylosin. The top 35 genera and ARGs profiles were clustered together based on the composting time. Combined composting parameters (temperature, pH, NH 4 + -N, NO 3 -N, and moisture content) accounted for 78.4% of the total variation in the changes in the potential host bacteria. In addition, the selected five composting parameters and six phyla (including 25 potential host bacterial genera) explained 46.9% and 30.7% of the variation in the ARG profiles according to redundancy analysis, respectively. The variations in ARGs during the composting process were mainly affected by the dynamics of potential host bacteria rather than integrons and the selective pressure due to bio-Cu and bio-Zn. [ABSTRACT FROM AUTHOR]

Abstract: Ten batches (75kg each) of garden soil with >50% of silt and clay and average 1935mgkg−1 Pb, 800mgkg−1 Zn, 10mgkg−1 Cd and 120mgkg−1 As were remediated in a pilot-scale chemical extraction plant. Washing with 60mmol ethylenediaminetetraacetic acid (EDTA) per kg of soil on average removed 79, 38, 70, and 80% of Pb, Zn, Cd and As, respectively, and significantly reduced the leachability, phyto-accessibility and oral-availability of residual toxic metals, as assessed using deionised water, toxicity characteristic leaching procedure (TCLP), diethylenetriamine pentaacetic acid extraction (DTPA) and physiologically based extraction test (PBET) tests. The used soil washing solution was treated before discharge using an electrochemical advanced oxidation process with graphite anode: EDTA was removed by degradation and toxic metals were electro-precipitated onto a stainless steel cathode. The novelty of the remediation technique is separation of the soil from the washing solution and soil rinsing (removal of mobilized contaminants) carried out in the same process step. Another novelty is the reuse of the soil rinsing solution from the previous batch for cleansing the soil sand, soil rinsing and for preparation of the washing solution in subsequent batches. The cost of energy and material expenses and disposal of waste products amounted to approximately 75€ton−1 of soil. [Copyright &y& Elsevier]

Abstract: This paper introduces a sequential eluent injection (SEI) technique combined with an on-line preconcentration/separation system for a fast and sensitive FAAS determination of trace amounts of Cr(III) and Cr(VI) species. The method is based on the simultaneous retention of Cr(III) and Cr(VI) on a single mini-column packed with a chloromethylated polystyrene functionalized with N,N-bis(naphthylideneimino)diethylenetriamine (PS-NAPdien) at pH 6.7. The retained chromium species was eluted by sequential injection of HCl for desorption of Cr(III), and NH3 and NH4NO3 buffer solutions for desorption of Cr(VI). All the chemical and flow injection variables were optimized for the quantitative preconcentration and speciation of Cr(III) and Cr(VI). Under the optimum conditions, the calibration graph obtained is linear over the concentration range of 2.0–60.0μgL−1 for Cr(III), and 8.0–180.0μgL−1 for Cr(VI). The preconcentration factors for Cr(III) and Cr(VI) were 70 and 30, respectively. The 3σ detection limits were 0.6μgL−1 and 2.5μgL−1 for Cr(III) and Cr(VI), respectively. The relative standard deviations were 2.55% and 0.8%, respectively, for 6 replicate determinations of Cr(III) and Cr(VI) at the 40.0μgL−1 level. The proposed method was applied for determination of Cr(III) and Cr(VI) in different water samples with satisfactory results. [Copyright &y& Elsevier]

Abstract: The melamine-diethylenetriaminepentaacetic acid/polyvinylidene fluoride (MA–DTPA/PVDF) chelating membrane bearing polyaminecarboxylate groups was prepared for the removal of Ni(II) from wastewater effluents. The membrane was characterized by SEM, 13C NMR and FTIR techniques. Quantitative adsorption experiments were performed in view of pH, contact time, temperature, the presence of Ca(II) and lactic acid as the controlling parameters. Adsorption kinetics and equilibrium were examined regarding the single Ni(II) system, binary Ni(II) and Ca(II) system and nickel–lactic acid complexes system. The desorption efficiency was also evaluated, and the adsorption mechanism was suggested based on experimental data. The results show that the sorption kinetics fit well to Lagergren second-order equation and the isotherms can be well described by Langmuir model. At 298K, the second-order rate constant is calculated to be 4.171, 11.39, 6.203cm2/(mgmin) and the equilibrium uptake is 0.0264, 0.0211 and 0.0216mg/cm2 in the aforementioned three systems. The distribution coefficient of Ni(II) slowly decreases from 4.27 to 2.72, and the separation factor (f Ni(II)/Ca(II)) increases from 3.10 to 8.46 when the initial Ca(II) concentration varies from 20 to 200mg/L. This reveals the chelating membrane shows more affinity for Ni(II) than Ca(II) ions. In the studied range of lactic acid concentration, Ni(II) uptake decreases with the maximum ratio of 10%. Chemical bonding (chelation) dominates in the adsorption process, and the negative ΔG° and ΔH° indicate the spontaneous and exothermic nature of adsorption. [Copyright &y& Elsevier]

Abstract: The adsorption of Co(II) by diethylenetriaminepentaacetic acid (DTPA)-modified silica gel and chitosan in the presence of EDTA and other interfering species was studied. Co(II) removal ranged from 93% to 96% from the solutions where Co(II) was totally chelated by EDTA. The amount of oxalate or Fe(II) did not affect the adsorption of Co(II) in the case of DTPA-chitosan. However, increasing the amount of oxalate enhanced the adsorption performance of DTPA-silica gel, probably due to the formation of new active sites on the silica gel surface. DTPA-chitosan was also effective in simulated decontamination solutions. For DTPA-silica gel, the rate of adsorption of free Co(II) was controlled by pore diffusion, but the rate of adsorption of Co(II)EDTA was controlled by the surface chelation reaction, which was attributed to the inhibited diffusion of Co(II)EDTA inside the silica gel mesopores. However, the macroporous structure of DTPA-chitosan enabled pore diffusion of both Co(II) and Co(II)EDTA. The equilibrium isotherms of DTPA-silica gel were best described by a BiLangmuir model, in which there are two different adsorption sites on the silica gel surface assigned to different speciations of DTPA. For DTPA-chitosan, the data fit best with a Sips model, which indicates system heterogeneity. Finally, measurements with capillary electrophoresis showed an increase in dissolved EDTA during adsorption, demonstrating the ability of DTPA-modified adsorbents to release Co(II) from its EDTA chelate. This promising result can provide a basis for applying the studied materials to the treatment of water effluents containing Co(II) chelated by EDTA by a simple one-step adsorption process. [Copyright &y& Elsevier]

Abstract: In this study, the removal of Co(II) and Ni(II) ions from contaminated water was investigated using silica gel materials functionalized with both ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA). The modified adsorbents were characterized using elemental analysis, surface area and pore size analysis, and zeta potential analysis. The adsorption and regeneration studies were conducted in batch mode. The optimum conditions for the removal of both metals at an initial concentration of 10mg/L were 2g/L of dose, pH 3, 50rpm of agitation speed and 4h of contact time. The removal of Co(II) and Ni(II) by EDTA- and/or DTPA-modified silica gels was substantially higher than that by their unmodified form. The maximum Co(II) and Ni(II) uptakes by the EDTA-modified silica gel were 20.0 and 21.6mg/g, comparable to their adsorption capacities by DTPA-modified silica gel (Co(II): 16.1mg/g; Ni(II): 16.7mg/g). At the same concentration of 10mg/L, the removal of both metals by the modified adsorbents ranged from 96% to 99%. The two-site Langmuir model was representative to simulate adsorption isotherms. The kinetics of Co(II) and Ni(II) adsorption by modified silica gels followed pseudo-second-order. [Copyright &y& Elsevier]

Efforts have been made in this study to stabilize the sewage sludge mixed with sugarcane trash in four different proportions: 20% (T1); 40% (T2); 60% (T3) and 80% (T4), under laboratory conditions using epigeic earthworm (Oligochaeta) Eisenia fetida. The composting potential of worm was also evaluated in 100% sewage sludge treatment (T5). The changes in chemical properties of substrate was measured at the end. The vermicomposted material showed decrease in organic C (4.8–12.7%) and exchangeable K (3.2–15.3%) content, whereas increase in total N (5.9–25.1%) and available P (1.2–10.9%), exchangeable Ca (2.3–10.9%) and exchangeable Mg (4.5–14.0%) contents. Vermicomposting process caused considerable reduction in concentration of diethylene-triaminepentaacetic acid (DTPA) extractable metals: Cu (4.98–30.5%), Fe (5.08–12.64%), Mn (3.31–18.0%), Zn (2.52–15.90%) and Pb (2.38–20.0%). E. fetida showed the better growth performances in first three treatments (T1–T3) possibly due to higher content of organic matter (supplied by bulking agent, i.e. sugarcane trash). The earthworm mortality was higher in vermibeds those contained more sludge proportions. Study revealed that vermicomposting might be an efficient technology to convert negligible municipal sewage sludge into value-added products. The feasibility of earthworms to mitigate the metal toxicity and to enhance the nutrient profile might be useful to convert noxious sludge into useful products, at low-input basis. [Copyright &y& Elsevier]

Abstract: Medical waste (MW) ashes from different types of MW incinerators were examined to detect the characteristics and environmental impact of rare earth elements (REEs). The results showed that total REE contents in the ash samples ranged from 10.2 to 78.9mg/kg. REEs in bottom ash were apparently higher than those in fly ash. Average REE contents in the ashes followed the sequence of Ce>La>Nd>Y>Gd>Pr>Sm>Dy>Er>Yb>Ho>Eu>Tb>Lu>Tm. Some of the elements, such as Sm, Dy, Ho, Er, Yb in the ash samples were in normal or nearly normal distribution, but Y, La, Ce, Pr, Nd, Eu, Gd, Tb, Tm, Lu were not normally distributed, indicating some of the ash samples were enriched with these elements. Crust-normalized REE patterns indicated that two types of the MW ashes were obviously enriched with Gd and La. Sequential extraction results showed that REEs in the ash mainly presented as residual fraction, while exchangeable and carbonate fractions were relatively low. DTPA- and EDTA-extraction tests indicated that REEs in the MW ashes were generally in low bioavailability. [Copyright &y& Elsevier]

Abstract: A fast, simple, sensitive and economical method for Cr(VI) extraction and determination in solid samples was developed and evaluated. The presented protocol for Cr(VI) determination in solid samples allows for simultaneous extraction and determination of Cr(VI) in one step. The procedure is based on a quantitative extraction method in which the complexing properties of diethylenetriaminepentaacetic acid (DTPA) were exploited to extract total Cr(VI) (soluble and insoluble forms) from the solid sample. A catalytic adsorptive stripping voltammetric technique is employed for direct determination of Cr(VI) in the extract. The effects of analytical parameters such as temperature, pH, composition and concentration of the supporting electrolyte (which simultaneously plays the role of extractant), extraction and accumulation time were investigated. The accuracy of the proposed procedure was tested by analyzing certified reference materials CRM 013 Paint Chips and CRM 019 Ash. The results obtained were compared with the results obtained using two other reference extraction procedures. The effects of potentially interfering ions which generally accompany Cr(VI) in natural samples on the Cr(VI) determination, with special notice to Cr(III) interference, are reported. [Copyright &y& Elsevier]

Abstract: Present study is focused on the decontamination and/or revegetation of fly ash dykes through naturally growing plants, namely Calotropis procera, Cassia tora, Chenopodium album, Sida cardifolia, Blumea lacera. The results of sequential extraction study showed that maximum amount of metals (Na, K, Fe, Mn, Cr, Pb, Ni, Cd) were associated with residual and Fe–Mn fractions. Diethylenetriamine penta acetic acid (DTPA)–triethanolamine (TEA) extraction assessed the bioavailability of the metals. The total metal accumulation in tested plants was found in the order; C. album > S. cardifolia > C. tora > C. procera > B. lacera. The maximum bioconcentration factor (BCF) was recorded in S. cardifolia for the metals (Na, Fe, Zn, Cd), in C. procera for the metals (Mn, Cu, Ni, Cr) and in C. album for the metals (Co, Pb). However, the translocation factor (TF) of most of the metals was found more in S. cardifolia followed by C. album than other plants. Among all the plants, C. album have shown high BCF and low TF values for toxic metals (Pb, Cd) and suitable for phytostabilization of these metals. Principal component analysis was used to predict translocation behavior of the metals in different parts of the plants which was found similar for the metals (Cu, Zn, Mn, Cr). All examined plants are suitable for revegetation (naturally grows on fly ash dykes) and S. cardifolia and C. album may be used for decontamination purposes. [Copyright &y& Elsevier]

Leachability and mobilility of metals were evaluated in sludge obtained from electroplating industry, using toxicity characteristic leaching procedure (TCLP) and diethylene triamine penta aceticacid test (DTPA). Sequential leaching procedure was used to determine the chemical fractionation of metals. Further, removal of metals from sludge using various chelators (EDTA, citric acid, siderophore) was evaluated. The leaching test indicated that nickel in the sludge sample exceeded 5ppm concentration. This categorized the sludge, as a toxic waste. The mobility of the metals in the sludge was in the following order: Ni, Fe, Zn, Cr, Pb. Metals were found to be associated with various fractions of sludge. The metal concentration in the sludge was very high as compared to normal abundance and thus not within the range to be used as a fertilizer. The low removal of metals from the sludge by various chelators may be due to overloading of metals and use of aged sludge rather than artificially contaminated one for the study. The results of this study bring forth the prospect of the use of siderophores for bioremediation, because it is biodegradable and ecofriendly. This can be achieved with further optimization of the method, exploration of more potent siderophores and by inclusion of metal bound sludge fraction specific treatments. [Copyright &y& Elsevier]

This study compares the effect of synthetic aminopolycarboxylic acids ethylenediamine tetraacetate (EDTA) and diethylenetriamine pentaacetate (DTPA) with natural low-molecular-weight organic acids (LMWOAs) oxalic acid and citric acid as chelators for enhancing phytoextraction of Cr and Ni by Brassica juncea on serpentine-mine tailings. Chelator treatments were applied at doses of 0.05 and 0.10mmolkg−1 dry soils after seedlings were grown in pots for 56 days. Experimental results indicate that EDTA and DTPA were the most efficient chelators of increasing the levels of Cr and Ni in the soil solutions over time. Additionally, the reduction of plant shoot biomass caused by the two synthetic chelators exceeds that caused by the LMWOAs. The total uptake (mass removal from soil) of metals by plants was enhanced via the chelators. Experimental results supported the use of B. juncea for Cr and Ni phytoremediation: B. juncea improved the removal of Cr and Ni from serpentine-mine tailings. However, low plant biomass did not assist phytoextraction by using EDTA and DTPA, both of which carry environmental risk. Therefore, adding LMWOAs during phytoremediation can provide an environmentally compatible alternative, which may decrease the use of synthetic chelators. [Copyright &y& Elsevier]

In this work the re-fixation of mobilized copper (Cu) that was released from a deactivated pilot Cu ore dressing plant in the tropical rain forest at Southeastern Amazon (Carajás) was studied. Samples of top soils, decay leaf litter deposited on soils, roots and leaves of standing biomass were taken for the determination of Cu concentration in order to evaluate the distribution of it between different environmental compartments. In the sampling points near to the now extinct plant, total Cu concentrations in the soil reached an average value of 2140μgg−1 above the natural level of about 40μgg−1, being that bioavailable Cu estimated by DTPA method varied from 1. 9 to 20. 7% of this total. From the data was possible to calculate that the soil compartment is able to hold around 10kgCu/m2 of ground. Roots of the standing biomass in that area hold around 17gCu/m2, while the Cu content in leaves showed to be largely independent of the Cu level in the soil. Copper in the leaves was estimated as around 1g/m2 of ground area. In turn, the decay leaf litter deposited on soil can hold about 1. 6gCu/m2. The terrestrial system surrounding the abandoned pilot plant demonstrated great buffer capacity to retain mobile Cu released by anthropogenic activities in the area. [Copyright &y& Elsevier]

Abstract: A pot experiment was carried out to study the potential of the plant of Brassica juncea for the phytoextraction of metal from fly ash amended soil and to study correlation between different pool of metals (total, DTPA, CaCl2 and NH4NO3) and metal accumulated in the plant in order to assess better extractant for plant available metals. The results of total metal analysis in the soil revealed the presence of Cr, which was found below detection limit (BDL) in the plants. The fly ash (FA) amendments and soil samples were extracted with different extractants and the level of metal vary from one extractant to another. The regression analysis between total and extractable metals showed better regression for all the tested metals except Mn (R 2 =0.001) in DTPA extraction. Correlation coefficient between metal accumulation by the plant tissues and different pool of metals showed better correlation with DTPA in case of Fe, Zn and Ni, whereas, Cu was significantly correlated with NH4NO3 and other metals (Pb, Mn) with CaCl2. The soil analysis results revealed that the mobility and plant availability of metals (Fe, Mn, Zn, Ni) within the profiles of amended soils was influenced by the change in pH, however, Pb and Cu was not affected. The metal accumulation in total plant tissues was found in the order of Fe>Ni>Zn>Mn>Cu>Pb and its translocation was found more in upper part. The plants grown on soil amended with 25%FA have shown significant increase in plant biomass, shoot and plant height, whereas, no significant effect was observed in root length. The cluster analysis showed 10%FA behave differently on the basis of physico-chemical properties and metal behavior. Thus, it may be concluded that B. juncea can be used for phytoextraction of metals, especially Ni in fly ash amendment soil. [Copyright &y& Elsevier]