Biodegradable Chelating Agent Research Articles

Extraction of heavy metals from copper tailings by ryegrass (Lolium perenne L.) with the assistance of degradable chelating agents

Heavy metal contamination is an urgent ecological governance problem in mining areas. In order to seek for a green and environmentally friendly reagent with better plant restoration effect to solve the problem of low efficiency in plant restoration in heavy metal pollution soil. In this study, we evaluated the effects of three biodegradable chelating agents, namely citric acid (CA), fulvic acid (FA) and polyaspartic acid (PASP), on the physicochemical properties of copper tailings, growth of ryegrass (Lolium perenne L.) and heavy metal accumulation therein. The results showed that the chelating agent application improved the physicochemical properties of copper tailings, increased the biomass of ryegrass and enriched more Cu and Cd in copper tailings. In the control group, the main existing forms of Cu and Cd were oxidizable state, followed by residual, weak acid soluble and reducible states. After the CA, FA or PASP application, Cu and Cd were converted from the residual and oxidizable states to the reducible and weak acid soluble states, whose bioavailability in copper tailings were thus enhanced. Besides, the chelating agent incorporation improved the Cu and Cd extraction efficiencies of ryegrass from copper tailings, as manifested by increased root and stem contents of Cu and Cd by 30.29–103.42%, 11.43–74.29%, 2.98–110.98% and 11.11–111.11%, respectively, in comparison with the control group. In the presence of multiple heavy metals, CA, FA or PASP showed selectivity regarding the ryegrass extraction of heavy metals from copper tailings. PCA analysis revealed that the CA-4 and PASP-7 treatment had great remediation potentials against Cu and Cd in copper tailings, respectively, as manifested by increases in Cu and Cd contents in ryegrass by 90.98% and 74.29% compared to the CK group.

Removal of heavy metals from Industrial brownfields by Hydrolysate from waste chicken feathers in intention of circular Bioeconomy

Contamination of soils with heavy metals is a problem which has a significant negative impact not only on the environment but also on the presence and quantity of soil bacteria; the basis of healthy soil. Currently, new types of biodegradable chelating agents which could effectively wash heavy metals from soils and would replace the used EDTA-based agents are being sought and tested. However, it would be advantageous to use waste materials in accordance with the circular bioeconomy. Therefore, the hydrolysate prepared by the thermal pressure hydrolysis of waste chicken feather initiated by malic acid containing amino acids was tested as a new ecological and cheap chelating agent for the removal of heavy metals from industrial soil. The efficiency of the heavy metal extraction during twenty-four hours was at least the same and usually higher than the EDTA-based agents, especially for Cr, Ni and mainly for As, which could not be washed out by EDTA even with extended contact times of several days. Simultaneously, it was found that the hydrolysate revealed a significant biostimulating effect on soil bacteria, whose amount increased by several orders within five days. Simultaneously, the increased number of bacteria produced biosurfactants which significantly participated in the washing out of heavy metals, thereby increasing the efficiency of the hydrolysate.

The effect of chelating agents on the Zn-phytoextraction potential of hemp and soil microbial activity

BackgroundHemp (Cannabis sativa) is a crop with a wide range of uses, from the production of fiber and seeds to the secondary metabolites for medicinal purposes. In addition, it is characterized by high biomass yield and the ability to accumulate heavy metals, which makes this plant convenient for phytoremediation purposes. In this study, the effect of applying exogenous biodegradable chelating agents, citric acid (CA) and nitrilotriacetic acid (NTA), to zinc-contaminated soil on zinc (Zn) uptake by two industrial hemp varieties ‘Felina 32’ and ‘Monoica’ was studied. The effect of CA and NTA on available Zn in soils was investigated using an ‘in pot’ experiment under controlled conditions. The effect of both tested compounds on soil microbial activity was simultaneously evaluated.ResultsAfter the application of NTA at a concentration of 5 mmol L−1, a > threefold increased accumulation of Zn in the above-ground parts was recorded in the ‘Felina 32’ variety. In the ‘Monoica’ variety, the levels of Zn in the above-ground parts were increased > twofold. NTA affected the soil microbiome negatively, causing decreased enzyme activity (in ‘Monoica’ planted soil) and induced respiration (in ‘Monoica’ and especially in ‘Felina 32’ planted soil). On the other hand, CA application did not lead to significantly increased Zn levels in any of the studied hemp varieties. Together with CA’s negative effects on some soil enzymes, CA enhanced urease activity, dehydrogenase and several respiration types for the ‘Felina 32’ variety and exerted less detrimental effect on the soil microbiome. No toxic effects from increased Zn uptake and accumulation in experimental plants were detected, accounting for the unchanged physiological stress markers (levels of photosynthetic pigments and proline in leaves, chlorophyll fluorescence parameters) and selected growth traits of the above-ground organs and root system.ConclusionsFrom the studied varieties, ‘Felina 32’ seems to be more suitable for Zn-phytoextraction because of its higher tolerance to increased Zn levels, higher biomass production and Zn accumulation capacity. Our results indicate the potential of using the ‘Felina 32’ variety in NTA-assisted Zn phytoextraction from contaminated soils.Graphical

Multipurpose Iron-Chelating Ligands Inspired by Bioavailable Molecules.

Because of their capacity to bind metals, metal chelators are primarily employed for therapeutic purposes, but they can also find applications as colorimetric reagents and cleaning solutions as well as in soil remediation, electroplating, waste treatment, and so on. For instance, iron-chelation therapy, which is used to treat iron-overload disorders, involves removing excess iron from the blood through the use of particular molecules, like deferoxamine, that have the ability to chelate the metal. The creation of bioinspired and biodegradable chelating agents is a crucial objective that draws inspiration from natural products. In this context, starting from bioavailable molecules such as maltol and pyrogallol, new molecules have been synthetized and characterized by potentiometry, infrared spectroscopy and cyclic voltammetry. Finally, the ability of these to bind iron has been investigated, and the stability constants of ferric complexes are measured using spectrophotometry. These compounds offer intriguing scaffolds for an innovative class of versatile, multipurpose chelating agents.

Degree of complexation of microelement ions by biodegradable IDHA chelator in water and simulated fertilization environment

Abstract The degree of complexation of microelement ions by the biodegradable chelating agent - IDHA was examined in the work. The tests were carried out in water and in a simulated fertilizer environment. In order to compare the obtained results, tests were also carried out for the commonly used EDTA. The performed analyzes allow to determine the influence of the presence of compounds containing macroelements on the degree of binding of microelement ions by the biodegradable IDHA and EDTA chelators. The obtained results make it possible to determine the optimal conditions for the chelation of cations by IDHA, which in the future may be used in the production of micronutrient fertilizers on a large scale.

Novel Biodegradable Chelating Agents for Micronutrient Fertilization.

Serious concerns about the negative impact of ethylenediaminetetraacetic acid (EDTA) on the environment resulted in severe restrictions imposed on this compound in many countries. One of the main concerns is related to the use of EDTA in agriculture as a chelator in microelement fertilizers: being introduced directly into the sawing fields, it penetrates into groundwater, with no chance to be captured/recycled. Respectively, there is an active search for environmentally friendly, biodegradable alternatives for this chelator. In this study, we proposed a biodegradable chelating agent, 2-((1,2-dicarboxyethyl)amino)pentanedioic acid (IGSA). It was synthesized in accordance with the principles of "green chemistry" from readily available nonhazardous precursors using water as a solvent; in addition, the method yields literally no waste. The synthesized chelator in the form of the crude reaction mixture was further used for preparing a multicomponent micronutrient fertilizer (B, Zn, Fe, Cu, Mn, and Mo). The fertilizer was shown to be highly biodegradable (72% in 28 days), while the EDTA-based product degraded only by 13%. The plant growing efficiency was tested on lettuce in the greenhouse experiments. The results were compared against the known commercial fertilizers based on EDTA and iminodisuccinic acid (IDS). The newly developed IGSA-based fertilizer significantly outperformed the EDTA-based fertilizer in lettuce biomass (1.4 and 1.6 times for root and foliar application, respectively). The total mineral uptake was almost two times higher (1.9 and 1.8 times for root and foliar treatments, respectively) compared to the EDTA-based complex and even slightly higher (1.2 and 1.1 times, respectively) compared to the IDS-based complex. Our work opens the doors for the industrial scale production and application of this fully "green", inexpensive microelement fertilizer that has the potential to replace the EDTA-based products.

Quantitative probing of reactive oxygen species and their selective degradation on contaminants in peroxymonosulfate-based process enhanced by picolinic acid

The processes of Fe(III) activated peroxymonosulfate (PMS) in degrading contaminants have been extensively studied. Herein, a biodegradable chelating agent, picolinic acid (PICA), was introduced to the PMS/Fe(III) process to improve the reaction efficiency. The emphases of this study were placed on the quantification of steady-state concentrations of reactive oxygen species (ROS). Experiments presented that five types of ROS, including Fe(IV), SO4•−, HO•, 1O2 and O2•− coexisted in this system. Four typical probe compounds were used to quantify the steady-state concentration of ROS under different variables. The steady-state concentration of Fe(IV) ([Fe(IV)]ss) was 3–5 orders of magnitude higher than that of other ROS, followed by 1O2 and SO4•−, whereas HO• had the lowest concentration. The reaction between PMS and PICA was first explored in our study and results showed that 1O2 and O2•− would form in this reaction. Owing to the hybrid oxidation by multiple ROS, this system showed high oxidation capacity, and could effectively degrade a variety of pollutants. The contributions of ROS to the alleviation of pollutants varied depending on their concentrations and specific reactivity of substrates. Generally, organic contaminants with phenol structures were prone to react with Fe(IV). Overall, this study compared the steady-state concentrations of different ROS and revealed the intrinsic ROS formation mechanisms.

Chemically Catalyzed Phytoextraction for Sustainable Cleanup of Soil Lead Contamination in a Community Garden in Jersey City, New Jersey

Soil lead (Pb) contamination in Pb paint-contaminated homes is a serious health risk in urban areas. Phytoextraction is a green and sustainable technology for soil Pb remediation, but its efficiency depends on the geochemical partitioning of Pb in soil. Following successful laboratory, greenhouse, and panel experiments, a field study was conducted to demonstrate the effectiveness of a chemically catalyzed phytoextraction model for Pb removal. A biodegradable chelating agent, ethylenediaminedisuccinic acid (EDDS) was applied during Pb phytoextraction by vetiver grass (Chrysopogon zizanioides) in a Pb-contaminated community garden in Jersey City, New Jersey. Results showed that soil Pb concentration was reduced from 1144 to 359 mg/kg in 3 years, despite ongoing Pb input to the field plots from a nearby construction site. EDDS was effective in converting non-plant-available forms of Pb (i.e., carbonate-bound, oxide-bound, and organic-bound forms) to plant-available forms (i.e., water-soluble and exchangeable forms). With EDDS application, vetiver roots accumulated 532, 231, and 401 mg/kg of Pb in Years 1, 2, and 3, respectively, which were higher than the values obtained without EDDS applications (228, 154, and 214 mg/kg). This field study demonstrated the effectiveness of a chemically catalyzed phytoextraction model for Pb removal from urban soils.

Insight into the subcellular mechanism of maximizing Cd accumulation in hyperaccumulator Solanum nigrum L. under the action of biodegradable chelating agent

Under the promotion of biodegradable chelating agents, hyperaccumulators can accumulate large amounts of heavy metals. However, in practical application, excessive accumulation of heavy metals will lead to the reduction of biomass, resulting in the reduction of heavy metal accumulation efficiency. Therefore, here we seek to investigate the dynamic process of vacuolar compartmentalization regulated by biological chelators, to provide guidance for improving the accumulation efficiency of heavy metals and alleviating the reduction of biomass. In this study, subcellular isolation was used to study the changes of enzyme activities, total cadmium (Cd), Cd2+, glutathione and reactive oxygen species (ROS) contents in protoplasts and vacuoles of leaf cells of Solanum nigrum L. The results indicate that vacuolar compartmentalization is a dynamic regulation process of continuous glutathione consumption. Under the promotion of biodegradable chelating agent N, N-bis glutamic acid (GLDA), more glutathione was induced and preferentially entered the vacuole to chelate and store Cd. Moreover, for large amounts of Cd accumulation, the insufficient supply of glutathione (GSH) preferentially maintains vacuolar homeostasis and causes redox damage outside the vacuole. These results showed that insufficient glutathione production led to the reduction of biomass. Therefore, in the practical application of GLDA, the consumption inside and outside the vacuole can be met by controlling the production of glutathione, so as to increase the efficiency of heavy metal accumulation.

Direct analysis of biodegradable chelating agents based on liquid chromatography/electrospray ionization mass spectrometry using a metal-free hydrophilic interaction liquid chromatographic column.

Recently, biodegradable aminopolycarboxylic acid chelating agents have attracted attention as an alternative to environmentally persistent chelating agents such as ethylenediamine-N,N,N',N'-tetraacetic acid. However, the detection of chelating agents requires complexation with metals or derivatization by esterification reagents, and their direct detection using the currently available analytical methods still represents a challenge. Herein, we describe a direct analytical method for the biodegradable chelating agents ethylenediamine-N,N'-disuccinic acid, 3-hydroxy-2,2'-iminodisuccinic acid, methylglycine-N,N'-diacetic acid, and N,N-bis(carboxymethyl)-L-glutamic acid, via ultra-performance liquid chromatography/electrospray ionization quadrupole/time-of-flight mass spectrometry. Satisfactory retention and separation with a good peak shape were successfully achieved using a metal-free hydrophilic interaction liquid chromatographic column. The calibration curves showed good linearity in the range of 1.0-50μM with correlation coefficients greater than 0.9988. The detection limits ranged from 0.04 to 0.12μM. Furthermore, the developed method could be applied to the quantitative analysis of the four chelating agents in biodegradation and photodegradation experiments at the laboratory level. The proposed method, which offers the advantages of quickness, sensitivity, and requiring no complicated pretreatment steps, is expected to contribute significantly to the practical analysis of chelating agents in environmental water samples.

Remediation of Heavy Metal Contaminated Farmland Soil by Biodegradable Chelating Agent GLDA

Chemical leaching is one of the effective methods to remove heavy metals from soil. The effects of biodegradable chelating GLDA (N, N-bis(carboxymethyl)-l-glutamic acid tetrasodium salt) on contaminated farmland soil in four different places (collected from Shangba Village, Shaoguan city (SB); Huaqiao Village, Zhuzhou (HQ); Shaoguan Tielong (TL); and Liantang Village, Lechang (LT), respectively) were studied by the method of leaching. To explore the synergistic effect between GLDA and citric acid, the leaching conditions were also explored. The results showed that the leaching efficiency of heavy metal Pb in soil was improved by adjusting the GLDA solution to reach acidity by adding citric acid. The leaching efficiency of Pb after mixing GLDA and citric acid was higher than the sum of their respective leaching abilities. After leaching with 10 mmol/L of the GLDA solution with a pH of 10.86 for 120 min, the total Pb and the Pb available in the soil decreased significantly. It is known that citric acid has a significant effect on improving the leaching rate of GLDA on soil, and this method can also be applied to other heavy metals, such as Cd. This study provides a low-ecological-risk method for the remediation of heavy metal-contaminated soils.

Chelating Agents in Assisting Phytoremediation of Uranium-Contaminated Soils: A Review

Massive stockpiles of uranium (U) mine tailings have resulted in soil contamination with U. Plants for soil remediation have low extraction efficiency of U. Chelating agents can mobilize U in soils and, hence, enhance phytoextraction of U from the soil. However, the rapid mobilization rate of soil U by chelating agents in a short period than plant uptake rate could increase the risk of groundwater contamination with soluble U leaching down the soil profile. This review summarizes recent progresses in synthesis and application of chelating agents for assisting phytoremediation of U-contaminated soils. In detail, the interactions between chelating agents and U ions are initially elucidated. Subsequently, the mechanisms of phytoextraction and effectiveness of different chelating agents for phytoremediation of U-contaminated soils are given. Moreover, the potential risks associated with chelating agents are discussed. Finally, the synthesis and application of slow-release chelating agents for slowing down metal mobilization in soils are presented. The application of slow-release chelating agents for enhancing phytoextraction of soil U is still scarce. Hence, we propose the preparation of slow-release biodegradable chelating agents, which can control the release speed of chelating agent into the soil in order to match the mobilization rate of soil U with plant uptake rate, while diminishing the risk of residual chelating agent leaching to groundwater.

Phytoremediation of cadmium-contaminated soils by Solanum nigrum L. enhanced with biodegradable chelating agents.

The application of biodegradable chelating agents to enhance phytoremediation is a low-cost and promising method to improve the remediation efficiency of heavy metal-contaminated soil. The effects of N, N-bis glutamic acid (GLDA) on the growth and heavy metal absorption of Solanum nigrum were studied by pot experiment. The addition of chelate on the 20th day after sowing can improve the bioavailability of cadmium (Cd) in the soil. The results showed that the addition of chelating agents effectively improved the migration rate of the target heavy metal Cd in the soil, and significantly increased the accumulation of heavy metal in the roots, stems, and leaves of plants. The results showed that compared with the control group, the chelating agent could increase the extraction rate of total Cd by 28.65-68.74%. The application of GLDA significantly increased the accumulation of Cd (20mgkg-1 and 40mgkg-1), reaching 24.28-40.30 and 25.71-33.16μg of pot-1 DW, respectively. At the same time, GLDA increased Cd stress by decreasing plant biomass, inhibiting photosynthetic pigment synthesis and increasing MDA levels. These results indicated that GLDA could improve the absorption of Cd by S. nigrum, which provided a new idea for its practical application in the remediation of Cd-contaminated soil.

Soil washing of arsenic from mixed contaminated abandoned mine soils and fate of arsenic after washing

Arsenic contamination in abandoned soils is a global concern which warrants an effective method of remediation. In this study, two organic acids and one biodegradable chelating agent were used to treat arsenic (As) contaminated abandoned mine soils. The concentration of As was 19,100 and 75,350 (mg/kg) for Webbs Consols (WC) and Mole River (MR) samples, respectively. X-ray diffraction and scanning electron microscopy confirmed that tooeleite, arsenopyrite, scorodite and quartz were the major minerals in these soils. A major portion of the As was composed of amorphous and crystalline oxides of Fe and Al determined by sequential extraction. Among the three washing reagents (oxalic acid, citric acid and EDDS) oxalic acid showed the best performance for extracting As. Based on the batch experiment, 0.5 M oxalic acid and 3 h of washing was the most efficient treatment to extract As and other trace elements. Extraction of As, Fe, and Pb was 70, 55, and 48% respectively for WC, while 68, 45 and 63% respectively for MR soil. Oxalic acid extracted 75 and 83% of As and Fe, respectively from tooeleite. Leachability and bioaccessibility of As and Fe in the treated soil was reduced due to washing. However, bioaccessibility and leachability of Pb in soil and Fe and As in tooeleite increased in washed samples. Though the leachability and bioaccessibility of As and Fe in soil was reduced in the treated soil, As still exceeded the USEPA criteria (5 mg/L) which is needed to successfully remediate soil by washing. Soil washing and subsequent solidification/stabilization could be an alternative option to remediate extremely contaminated abandoned mine soil.

MICROWAVE ENHANCED CHROMIUM EXTRACTION FROM SEWAGE SLUDGE AND SOIL-SLUDGE MIXTURES USING BIODEGRADABLE CHELANTS

Microwave enhanced chromium extraction from sewage sludge and soil-sludge mixtures was carried out using ethylenediaminetetraacetic acid (EDTA) and more biodegradable chelating agents: methyleneglycinediacetic acid (MGDA), S, S’-ethylenediaminedisuccinic acid (EDDS) and S-carboxyl-L-cysteine (SCLC). Raising the temperature using microwave energy had particularly strong effect on Cr extraction efficiency with MGDA from all the investigated biosolids. The higher was the temperature, the larger amount of metal was extracted – maximum removal efficiency with MGDA at 150oC was 38 times higher than that at 20oC. The effect of microwave-assisted extraction duration was also significant – extraction effectiveness increased by 40-60 % at 150oC while increasing duration from 15 min up to 60 min, depending upon the type of biosolid tested. MW-enhanced chromium extraction efficiency from sludge mixture with clay soil was in all cases significantly lower than that from the raw sludge samples as well as sludge mixture with sandy soil. Extraction study showed that such readily degradable agents as EDDS and MGDA can be successfully used to wash biosolids in the presence of chromium contamination instead of persistent EDTA when microwave energy is applied, while SCLC was less efficient. According to the complexation efficiency, the investigated chelants can be ranked in the following order: EDTA≈MGDA>EDDS>SCLC, while the overall chromium removal capacity of MGDA was better than that of EDDS.

Sustainable extraction of hazardous metals from crystal glass waste using biodegradable chelating agents

Extraction of hazardous metals from dumped crystal glass waste was investigated for site decontamination and resource recovery. Mechanically activated glass waste was leached with biodegradable chelating agents of ethylenediamine-N,N′-disuccinic acid (EDDS) and nitrilotriacetic acid (NTA), where the concentration and reaction time were determined by using Box–Wilson experimental design. Hazardous metals of lead (Pb), arsenic (As), antimony (Sb) and cadmium (Cd) with concentrations higher than regulatory limits were extracted wherein the extraction yield was found to vary Pb > Sb > As > Cd. Extraction was influenced more by type and concentration of chelator rather than by reaction time. A maximum of 64% of Pb could be extracted by EDDS while 42% using NTA. It is found that increase of chelator concentrations from 0.05 M to 1 M did not show improved metal extraction and the extraction improved with reaction time until 13 h. This study provides sustainable alternative for treating hazardous glass waste by mechanical activation followed by extraction using biodegradable chelator, instead of acid leaching.Graphical abstract

Impact of EDDS Dosage on Lead Phytoextraction in Contaminated Urban Residential Soils

Lead (Pb) contamination in soils of residential properties due to peeling and chipping of Pb-based paint can cause human health problems. Phytoextraction is a green technology that has the potential to remediate soil Pb. The efficiency of phytoextraction is dependent on the geochemical forms of Pb in soil. A biodegradable chelating agent, ethylenediaminedisuccinic acid (EDDS), was previously shown to enhance Pb removal by facilitating phytoextraction. In this study, EDDS was tested at various concentrations for its potential in mobilizing Pb in urban residential soils in Jersey City, New Jersey, and San Antonio, Texas. Results show that the concentrations of plant-available forms of Pb increased with the increasing dosage of EDDS from 2 to 30 mmol/L. The addition of EDDS at 30 mmol/L resulted in the conversion of up to 61.2% and 68.9% of the total Pb to plant-available forms in Jersey City and San Antonio soils, respectively. Further analysis showed that, after EDDS application, carbonate-bound Pb, oxide-bound Pb, organic-bound Pb, and residual silicate-bound Pb were transformed to plant-available forms. Higher doses of EDDS performed better than lower doses in transforming soil Pb forms, especially for the oxide-bound Pb. Strong correlations between Pb concentrations measured on-site using a portable X-ray Fluorescence Analyzer (p-XRF) and those obtained in the laboratory using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) confirmed that p-XRF is a reliable rapid, convenient technology to measure Pb levels in situ.

Combined Use of Reducing Agents and Biodegradable Chelating Agent for Iron Rust Removal.

Since many of the current chemicals used to remove iron rust are hazardous to the environment and human health, the combined use of a reducing agent and a biodegradable chelating agent has been suggested as an environmental friendly and highly safe alternative. In the present work, the compatibility of the newly devised cleaning test with a model iron rust stain was confirmed by X-ray diffraction and scanning electron microscopy. Additionally, the cleaning efficiency of the method was evaluated by X-ray fluorescence. The cleaning mechanism and the synergistic effect of the reducing agent and the chelating agent was investigated using the phenanthroline absorption measurement method, and the results revealed that the reduced iron ions were dissolved by the chelating agent. The cleaning test proved that tetrasodium 3-hydroxy-2,2'-iminodisuccinate (HIDS) is a promising biodegradable chelating agent as an alternative to ethylenediaminetetraacetic acid (EDTA) for removing iron rust. It was also confirmed that the type of reducing agent used determines the pH at which detergency is enhanced. The detergency of the combination of the reducing agent and the biodegradable chelating agent was equal to or higher than the detergency of the acid agent, and thus, it was concluded that the proposed method has a great potential for commercial use.

The influence of chelating agents on clays in geothermal reservoir formations: Implications to reservoir acid stimulation

Acid stimulation to enhance the permeability of geological reservoirs is the oldest technique still in use. Acid stimulation sometimes fails due to either poor stability of the acid or due to an undesirable influence on clay minerals in the reservoir formation. Among others, clay minerals in a reservoir formation govern the permeability of the reservoir. The interaction is investigated of biodegradable chelating agents (BCA1, BCA2 and BCA3) and clay minerals kaolinite-natural (KN) and montmorillonite-K10 (MM) in a hydrothermal reactor in which the conditions of a geothermal reservoir are simulated under a CO2 environment with temperature of 230 οC and pressure of 85 bars. The porisimetry, ATR-FTIR and infrared reflectance spectroscopy show changes on surface properties and structure of MM and KN which in turn suggest chemical interaction to take place. However, XRD results show insignificant changes on structure of MM and KN. The ICP-OES, pH, conductivity and salinity results show the chemical interactions (dissolution reactions) to take place on both KN and MM and therefore strongly support the results of the earlier techniques. The results show that BCA1 and BCA3 cause greater dissolution with lower precipitation as compared to BCA2 and no-BCA. Further, the R -values from multiple linear regression show that pH and BCAs’ function groups have strong influence on the normalized concentration of dissolved ions though the p-values are insignificant. The coefficient values show that the BCAs’ functional groups have more influence than pH. BCA1 and BCA 3 would therefore be useful acids for reservoir stimulation in improving permeability especially in geothermal reservoir formations which contain clay minerals.

NTA-assisted mineral element and lead transportation in Eremochloa ophiuroides (Munro) Hack.

Lead (Pb) is one of the most toxic and harmful pollutants to the environment and human health. Centipedegrass (Eremochloa ophiuroides (Munro) Hack.), an excellent ground cover plant for urban plant communities, exhibits the outstanding lead tolerance and accumulation. Nitrilotriacetic acid (NTA) is an environmentally friendly chelating agent that strengthens phytoremediation. This study explored the effects of different NTA concentrations on the absorption and transportation of mineral elements and Pb in centipedegrass. Following exposure to Pb (500μM) for 7days in hydroponic nutrient solution, NTA increased root Mg, K, and Ca concentrations and shoot Fe, Cu, and Mg concentrations and significantly enhanced the translocation factors of mineral elements to the shoot. Although NTA notably decreased root Pb absorption and accumulation, it significantly enhanced Pb translocation factors, and the Pb TF value was the highest in the 2.0mM NTA treatment. Furthermore, the shoot translocation of Pb and mineral elements was synergistic. NTA can support mineral element homeostasis and improve Pb translocation efficiency in centipedegrass. Regarding root radial transport, NTA (2.0mM) significantly promoted Pb transport by the symplastic pathway under the treatments with low-temperature and metabolic inhibitors. Meanwhile, NTA increased apoplastic Pb transport at medium and high Pb concentrations (200-800μM). NTA also enhanced the Pb radial transport efficiency in roots and thus assisted Pb translocation. The results of this study elucidate the effects of NTA on the absorption and transportation of mineral elements and Pb in plants and provide a theoretical basis for the practical application of the biodegradable chelating agent NTA in soil Pb remediation.