Ethylenediaminetriacetic Acid Research Articles

Selective adsorption of Copper (II) ions in mixed solution by Fe3O4-MnO2-EDTA magnetic nanoparticles

To combine the properties of Cu2+ selective adsorption and magnetic separation of adsorbents from mixture, Fe3O4-MnO2 was modified with TMS-EDTA (N-(trimethoxysilylpropyl) ethylenediamine triacetic acid) to obtain Fe3O4-MnO2-EDTA. The as-synthesized materials were characterized and selective adsorption properties of Cu2+ were investigated under different conditions. Experimental results showed that Fe3O4-MnO2-EDTA exhibited high Cu2+ selective adsorption performance in both binary and ternary metal species systems. The selective adsorption mechanism was illuminated through the analysis of FTIR, XPS and Cu2+/Cd2+ binary kinetics experiments, in which a complexation replacement procedure could be found. Moreover, the Cu2+-adsorbed TMS-EDTA segments would generate steric hindrance to restrain Cd2+ from approaching Fe3O4-MnO2-EDTA particles. Cd2+, initially adsorbed by Fe3O4-MnO2-EDTA, finally would be replaced by other free Cu2+ and released back to the solution. Compared with Fe3O4-MnO2, the Fe3O4-MnO2-EDTA magnetic nanoparticles successfully combined the advantages of fast magnetic separation with high Cu2+ selectivity.

Evaluating the adsorptivity of organo-functionalized silica nanoparticles towards heavy metals: Quantitative comparison and mechanistic insight

Organo-functionalized SiO2 nanoparticles are regarded as promising adsorbents for capture of heavy metals. However, actual adsorptivity of a specific functional group onto SiO2 surface is unclear, thus extending a debate on which type of organic group possesses a better affinity toward heavy metals. Herein, surface functionalization of SiO2 with different groups (i.e., -EDTA (ethylenediamine triacetic acid), -COOH, -SO3H, -SH and -NH2) were achieved by a facile silylating reaction. Batch experiments indicated that adsorption capacity of SiO2 was remarkably improved by surface functionalization. Quantitative analysis manifested that one mole of EDTA grafted onto SiO2 surface can adsorb 1.51 mol of Pb(II) ions, which was 7.7, 17.1, 28.4 and 50.2-fold larger than those of COOH-, SO3H-, SH- and NH2-functionalized SiO2, respectively. This is first time to evaluate adsorptivity of functionalized SiO2 on the basis of per effective functional group, which may repair deficiency of conventional assessment method that calculated on the basis of per unit mass. Further, adsorption mechanism of these functionalized SiO2 were identified and uncovered by experimental and theoretical studies. This work not only develops an efficient adsorbent for heavy metal remediation but also provides a valuable insight for evaluation and design of novel SiO2-based materials.

Assessing Soil Degradation in Relation to Metal Pollution – A Multivariate Approach

ABSTRACTSoil degradation due to elevated levels of metals is considered as a potent threat to soil quality and human health. Present investigation was carried out to develop a protocol for assessing degree of soil degradation in relation to metal accumulation due to long-term use of waste water and municipal solid-waste. For this purpose, surface soil samples having a long-history of receiving industrial-effluents, sewage, polluted river-water and municipal solid-waste were collected. Computation of conventional metal accumulation indices indicated metal-specific differential soil pollution at different sites. Multivariate analysis considering important physicochemical properties and ethylenediamine triacetic acid (EDTA)-extractable metal content of soil revealed more comprehensive status of soil-degradation due to metal accumulation. Results indicated that soils irrigated with cycle-factory effluent (soil quality index, SQI 0.42) were the most degraded and soils irrigated with polluted river-water (SQI 0.94) were the least degraded due to metal pollution. Hierarchical clustering suggests that quality of tube-well, river and sewage-effluent irrigated soils are almost similar, which differs significantly from other soils receiving industrial-effluents and solid-waste.

Single precursor-based luminescent nitrogen-doped carbon dots and their application for iron (III) sensing

Iron III (Fe3+) sensing is of great importance for monitoring its levels in different environmental and biological systems since its levels are tightly associated with many environmental concerns and serious diseases. Compared to the ordinary Fe3+ detection methods involving the sophisticated and expensive instruments, the use of fluorescent materials with short response time and low cost attracts much attention. Amongst a variety of fluorescent materials, a nitrogen-doped carbon dot (N-CD) is emerging as promising luminescent materials for biosensing due to their superior photoluminescent properties, good water solubility, and biocompatibility. Herein, N-CD prepared via a green and cost-effective one-pot hydrothermal method using a new single precursor N-(2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA) as both the carbon and nitrogen sources is reported. The blue fluorescent emission of N-CDs is quenched by the addition of Fe3+, and the quenching intensity is concentration dependent in the wide range (0.76–400 μM) with a detection limit of 0.16 μM. The quantum yield for the as prepared N-CDs is 14.17%. The N-CDs also show a high selectivity for Fe3+ chelation amongst a range of biological metal ions. The fluorescent quenching is attributed to the formation of the coordinate covalent bonds between the Fe3+ and N-CDs, and the mechanism is proved to be a static type on the basis of the photoluminescence lifetime and the temperature-dependent fluorescent intensity change. Our eco-friendly and simple strategy will benefit the application of CDs in various fields.

Application of NOBIAS Chelate-PA 1 Resin to the Determination of Zirconium, Niobium, Hafnium, and Tantalum in Seawater.

Zirconium, niobium, hafnium, and tantalum are dissolved in seawater as hydroxide complexes at a concentration as low as 0.01 - 370 pmol kg-1 and are expected to be potential tracers for water masses in the ocean. Herein, we report a new analytical method for the multielemental determination of the four elements on the basis of column extraction, using a NOBIAS Chelate-PA 1 resin that contains ethylenediaminetriacetic acid groups. The elements were collected on the resin from seawater that had been added with 3.8 mM HF at pH 6.0, and were eluted with 5 M HF. After the evaporation of 5 M HF, the elements were dissolved in 0.5 M HNO3-6 mM H2SO4-1 mM HF and were determined by a high resolution ICP-MS, using a calibration curve method. We optimized the procedure to achieve quantitative recoveries and low backgrounds for the elements, although the complex formation between the metal ions and NOBIAS Chelate-PA 1 was decelerated by the seawater matrix. The method was tested by investigating the seawater samples of reference material and those collected from the depths at a station in the western North Pacific Ocean.

Highly efficient extraction of rare earth elements and others ions from green phosphoric acid medium using TMSEDTA@GO@Fe3O4 core-shell

Tunisian industries process enormous quantity of green phosphoric acid. The latter contains significant amounts of rare earth elements. This work highlights the extraction of numerous rare earth elements from concentrated green phosphoric acid solutions based on core-shell graphene oxide@Fe3O4 (GO@Fe3O4) nanoparticles, prepared by a simple and cost-effective method, and functionalized by N-(trimethoxysilylpropyl) ethylenediamine triacetic acid (TMSEDTA). The as-synthetized and functionalized cor-shell materials were fully characterized through several techniques to assess their morphology, size and crystallinity. Raman spectroscopy, FTIR and X-ray Photoelectron Spectroscopy were used to identify their chemical composition, while Inductively Coupled Plasma Optical Emission Spectrometry was used to determine the concentration of rare earth elements before and after the extraction process. TMSEDTA@GO@Fe3O4 particles exhibited a high efficiency to uptake the rare earth elements present in the concentrated phosphoric acid medium. In addition, thanks to the ferromagnetic properties of the particles and to the corrosion-resistant graphene oxide layer, the earth metal uptake procedure, by a magnet, from concentrated phosphoric acid is very simple. These promising results which are based on a straightforward process might be beneficial to industrial phosphoric acid manufacturers for extracting rare earths from concentrated acid.

New detection of flinders island spotted fever (due to Rickettsia honei infection) in new south wales: A case of fulminant septic shock and multi-organ failure

We report a case of a new location and severe infection for Rickettsia honei. A 76-year-old man, five days after returning from a camping trip to Grafton and Coffs Harbour, presented to the emergency department with two-day history of widespread rash, fever, rigors, confusion and decreasing mobility with rapid deterioration. He eventually progressed into multi-organ failure requiring dialysis, vasopressor support and intubation. On day 2, rickettsial infection was suspected. Therefore, a blood ethylene diamine triacetic acid (EDTA) tube for rickettsial polymerase chain reaction (PCR) and serology (microimmunofluorescence assay) were sent to the Australian Rickettsial Reference Laboratory. He was started on oral doxycycline 100 mg BD via nasogastric tube but did not improve. On day 4, his treatment was escalated to intravenous azithromycin 500 mg daily and intravenous doxycycline 100 mg BD (Special Access Scheme Category A) given non-improvement and doubtful absorption of oral doxycycline considering high vasopressor support. He rapidly improved 48 hours later with reducing organ support, extubated and subsequently discharged from ICU on Day 8. Subsequently, his serology and PCR suggested Spotted Fever Group Rickettsia. Further amplification of the citrate synthase and outer membrane protein A genes confirmed Rickettsia honei infection, which had not been detected in New South Wales previously.

Regioselective conversions of H4pdta (1,2-propanediaminetetraacetic acid) and H4eed3a to their triacetates on peroxotitanates.

1,2-Propanediaminetetraacetic acid (H4pdta = C11H18O8N2) is degraded selectively to 1-methyl-1,2-propanediaminetriacetic acid (H3pd3a = C9H16O6N2) with a yield of 75% at room temperature, while N-(2-hydroxyethyl) ethylenediaminetriacetic acid (H4eed3a = C10H18O7N2) is converted with difficulty to ethylenediaminetriacetic acid (H3ed3a = C8H14O6N2) on peroxotitanates(iv), showing the influence of the uncoordinated leaving group. Various species in the reaction sequence are isolated and fully characterized, including (NH4)[Ti(O2)(Hpdta)]·H2O (1), (NH4)3[Ti(O2)(pdta)H(pdta)(O2)Ti]·7H2O (2), (NH4)[Ti(O2)(pd3a)]·H2O (3) and (NH4)[Ti(O2)(Heed3a)]·H2O (5). Peroxo dimer 2 forms a strong intramolecular hydrogen bond [2.451(3) Å] as an intermediate in the peroxo Ti-pdta system, which results in the absence of a fully deprotonated species of peroxo pdta titanate. A catalytic reaction of the peroxo titanate (NH4)3[Ti(O2)(pdta)H(pdta)(O2)Ti]·7H2O (2) for the conversion of pyridine to pyridine N-oxide shows 94% conversion at 80 °C.

In situ crosslinking of poly(vinyl alcohol)/graphene oxide Nano-composite hydrogel: intercalation structure and adsorption mechanism for advanced Pb(II) removal

Based on the industrialized graphene oxide (GO) product, poly(vinyl alcohol) (PVA)/GO nano-composite hydrogels were prepared through in situ crosslinking by incorporation of N-[(trimethoxysilyl)propyl] ethylenediamine-triacetic acid sodium (CSA) as a compatibilizer. Introduction of CSA led to more efficient grafting of PVA molecules onto GO surface with increasing average layer thickness through covalent and hydrogen bonding interaction, while GO was exfoliated and uniformly distributed in PVA matrix. Addition of appropriate content of GO can improve the storage modulus and the effective crosslinking density (υe) of the composite hydrogel, and the network structure with GO as crosslinking point formed, resulting in the remarkable increase of the hydraulic impact resistance, mechanical strength and toughness of the hydrogel. Pb2+ adsorption capacity of the hydrogel increased with GO content, while the adsorption belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model, indicating the homogeneous nature of monolayer chemical adsorption of Pb2+. A relatively good reusability of the composite hydrogel beads for Pb2+ removal can be achieved.

Colorimetric chemosensor for Fe2+ and Fe3+ based on a ternary mixture of an anionic dye, a cationic polyelectrolyte, and a metal chelator in aqueous solution

A new colorimetric chemosensor based on a simple ternary mixture of an anionic dye, pyrogallol red (PR), a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC), and a metal chelator, N-(2-hydroxyethyl) ethylenediaminetriacetic acid (HEDTA) for the colorimetric detection of Fe2+ and Fe3+ has been developed in an aqueous solution buffered at pH 5. Upon addition of Fe2+ or Fe3+ to the mixture, the absorption spectra showed a bathochromic shift; correspondingly, the solution color changed from red to blue, whereas other metal ions basically resulted in insignificant spectral and color changes. From the competitive experiments, no obvious interferences for the colorimetric detection of Fe2+ and Fe3+ were observed in the presence other metal ions. The results indicated that the mixture could be used as a potential Fe2+ and Fe3+ colorimetric and naked eye chemosensor in aqueous media. This research demonstrates that the ternary ensemble consisted of an organic dye, an oppositely charged polyelectrolyte, and a metal chelator is a versatile and convenient tool for the facile preparation of a novel chemosensor system.

Ethylenediaminetriacetic Acid-Functionalized Activated Carbon for the Adsorption of Rare Earths from Aqueous Solutions

A novel and low-cost ethylenediaminetriacetic acid-functionalized activated carbon (EDTA-AC) was synthesized by anchoring N-[(3-trimethoxysilyl)propyl]ethylenediaminetriacetic acid (TMS-EDTA) to oxidized activated carbon (AC). Material characterization was done by FTIR and Raman spectroscopy, TGA, N2 physisorption, SEM and the Boehm titration method, the latter being used to determine the amount and type of oxygen functional groups present in carbon samples. EDTA-AC was tested for the adsorption and separation of rare-earth ions from aqueous solutions, in order to evaluate the feasibility of using this material for the recovery of rare earths from industrial wastewater, tailings and electronic waste, like batteries, magnets and lamp phosphors. The maximum adsorption capacity of EDTA-AC was derived for Nd(III) by constructing an adsorption isotherm and fitting the data to the Langmuir adsorption model. A kinetic and thermodynamic study were performed by varying the contact time and the temperature and plot...

A fractionation approach applying chelating magnetic nanoparticles to characterize pericardial fluid's proteome

Owing to their close proximity, pericardial fluid (PF)’s proteome may mirror the pathophysiological status of the heart. Despite this diagnosis potential, the knowledge of PF's proteome is scarce. Large amounts of albumin hamper the characterization of the least abundant proteins in PF. Aiming to expand PF's proteome and to validate the technique for future applications, we have fractionated and characterized the PF, using N-(trimethoxysilylpropyl)ethylenediamine triacetic acid (EDTA)-functionalized magnetic nanoparticles (NPs@EDTA) followed by a GeLC-MS/MS approach. Similarly to an albumin-depletion kit, NPs@EDTA-based fractionation was efficient in removing albumin. Both methods displayed comparable inter-individual variability, but NPs@EDTA outperformed the former with regard to the protein dynamic range as well as to the monitoring of biological processes. Overall, 565 proteins were identified, of which 297 (>50%) have never been assigned to PF. Moreover, owing to this method's good proteome reproducibility, affordability, rapid automation and high binding ability of NP@EDTA, it bears a great potential towards future clinical application.

Interactions between different acids and bauxitic-based ceramic proppants used in gravel-packed and fractured wells

Proppants are widely used in hydraulic fracturing operations. They consist of solid particles with specific strengths and are used to keep the fractures open to enhance well production. They can be natural sand or artificial ceramic materials. Most ceramic proppants are alumina-based, using kaolin and bauxitic clays as the raw materials. The acid resistance of the fracturing proppant is an essential property. Acids are sometimes needed to clean the fracture by removing scale and clays that reduce the fracture conductivity.In this study, several experiments were conducted using a see-through cell, and an aging cell with 10 wt% HCl, mud acids (6.0 wt% HCl, 1.0 wt% HF and 12.0 wt% HCl, 3.0 wt% HF), i.e., (6:1 and 12:3), and formic (HCOOH), trisodium salt of N-(hydroxyethyl)-ethylenediaminetriacetic acid (Na3-HEDTA) and HF mixtures up to 350 °F. The effects of varying acid system, temperature, soaking time, static and dynamic conditions were examined. The supernatant of solubility tests was analyzed with Fluorine Nuclear Magnetic Resonance (19F NMR) to identify the reaction products. Key elements concentrations were measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). A Zeiss Axiophot microscope was used to acquire images for the proppant particles to study particle shape and effect of acid solubility. Proppants were then analyzed by X-ray fluorescence (XRF) and X-ray diffraction (XRD). The proppant was sieved before and after the experiments. The residual solids were dried and analyzed using a scanning electron microscope (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) capabilities. Effects of acid dissolution on mechanical performance of the proppants were also tested using an automated load frame.The results show that bauxite has a minimal solubility of 0.5 wt% in 10.0 wt% HCl. The proppant is readily soluble in different mud acids, 56.0 wt% dissolved in some cases. The amount dissolved increases with temperature, soaking time, acid concentration, and dynamic conditions. The fines generated and the changes in grain size distribution are detrimental to the proppant conductivity. 19F NMR showed aluminum fluoride complexes with different mud acids due to the high Al/F affinity. XRF showed that the solubility of the proppant occurs mainly in mullite and maghemite due to their high reactivity. Crush resistance test shows a direct relationship between solubility and mechanical strength of bauxite. Assessing solubility effects will help to better design acid treatments without jeopardizing the integrity of the proppant.

Influence of complexing agent on the removal of Pb(II) from aqueous solutions by modified mesoporous SiO2

In this study, SiO2-EDTA was prepared by silanization reaction between N-(trimethoxysilylpropyl) ethylenediamine triacetic acid, trisodium salt (EDTA-silane) and hydroxyl groups for enhanced removal of Pb(II), Pb(II)-Cit (the clathrate generated by Pb(II) and trisodium citrate dehydrate(Cit)) and Pb(II)-EDTA(20%) from aqueous solutions. SiO2-EDTA composites were characterized using SEM, TEM, EDX-mapping, FTIR, XPS and TGA analyses. The influence of solution pH, initial concentration, contact time and co-existing interferents were also studied. Results demonstrated that the composite successfully adsorbed 147.52, 107.65 and 124.18 mg g−1 of Pb(II), Pb(II)-Cit, and Pb(II)-EDTA (20%), respectively with the initial Pb(II) concentration of 100 mg L−1. Kinetics study revealed that the adsorption rate was significantly high at the beginning and then reached to equilibrium within 1.0 h. Moreover, Pb(II) adsorption capacities were found to considerably affected by co-existing cations and not inhibited by natural organic matter (NOM). Characterization analyses confirmed that EDTA was successfully assembled on SiO2 which had been used as a supporting matrix due to its huge specific surface area. Findings from this study suggested that the present composite could be considered as a promising adsorbent for large scale treatment of wastewater containing elevated Pb(II) concentration.

Onsite chelate resin solid-phase extraction of rare earth elements in natural water samples: its implication for studying past redox changes by inorganic geochemistry

Rare earth element (REE) patterns in natural water and geological samples provide information on previous changes in environmental conditions, such as redox changes and material cycles; however, quantitative analysis of REEs in these samples is complicated by the relatively low contents of REEs in such samples as well as mass interference from 135Ba16O and 137Ba16O in inductively coupled plasma mass spectrometry (ICP-MS) analyses. In this study, onsite solid-phase extraction and preconcentration methods for REEs using an iminobisacetic acid–ethylenediaminetriacetic acid chelate resin (Nobias Chelate PA1, Hitachi High-Tech Fielding) were adopted for the analyses. Standard reference materials (SPS-SW1 artificial surface water) and natural ground water and spring water samples were used to evaluate the methods. Using the chelate resin, background levels of REEs were found to be less than 0.3 ng L−1 and recovery rates (REEs, 1 ng L−1) were 97.9–106.7% for the artificial surface water. Ba contents were lower than the detection limit after extraction. Additionally, duplicate analyses were performed to check the reproducibility of the onsite extraction. The REE patterns in the natural water samples were in good agreement with those obtained using a previous method (the interference calibration method without solid-phase extraction). Therefore, onsite solid-phase extraction using the chelate resin was demonstrated to be a rapid and simple preparation technique for REE analyses.

Mixing chelating agents with seawater for acid stimulation treatments in carbonate reservoirs

Chelating agents are used to remove formation damage created by the drilling fluid filter cake in oil and gas wells. They were also used to remove the precipitation of scales around the perforation tunnels, inside tubing, and in surface facilities. Recently, chelating agents were introduced as stand-alone stimulation fluids to stimulate carbonate and sandstone reservoirs. Many studies were conducted on chelating agents and confirmed their ability to remove the damage and create wormholes in carbonate cores. Most of the previous studies focused on the effect of mixing chelating agents with fresh water in matrix stimulation. The stimulation process in offshore wells requires lots of fresh water and this will add more cost to the stimulation treatment due to the transportation requirements.In this study, the effect of mixing chelating agent with seawater on the matrix stimulation was investigated. The matrix simulation treatments were conducted at different conditions of temperature, chelating agent concentration, and injection rate. The optimum injection rate and concentration of the chelating agent were determined using coreflooding experiments. New optimization process was introduced based on the volume and time requirements to execute the acid stimulation job. The effect of chelating agent concentration on the interfacial tension was also investigated. The optimum injection rate was determined for the 20wt% hydroxy ethylene diamine tri acetic acid (HEDTA) chelating agent for different core lengths and this was compared to the estimated optimum injection rate.The results of this study confirmed the existence of an optimum injection rate at different temperatures. Also it proposed an optimum chelating agent's concentration that gave an economic stimulation treatment. The comparison between matrix stimulation using chelating agent prepared by deionized water and that prepared using seawater concluded that seawater can be used instead of fresh water in matrix stimulation. The new proposed method that depends on the volume and time can be used effectively to determine the volume and time of the stimulation treatment. We found good match between the optimum injection rate determined in the laboratory and the estimated one.

Evaluation of using HEDTA chelating agent to clean up long horizontal heterogeneous sandstone wells without divergent

The removal of the calcium carbonate water-based filter cake and the associated formation damage after drilling is a very difficult task, especially in horizontal and extended reach wells. The horizontal section length could be 20,000 ft or more with different permeability distributions, which makes the damage caused by the drilling fluid vary from one section to another. The filter cake removal in heterogeneous long horizontal lateral needs diverters to distribute the cleanup fluid through the entire section. In this paper, a smart fluid (HEDTA of 20 wt% and pH 4, hydroxyethyl ethylenediamine triacetic acid trisodium salt) was evaluated to remove the damage caused by calcium carbonate weighted drilling fluid for the horizontal and extended reach wells without adding gelling agents. This fluid will react with the calcium carbonate in the filter cake and the calcium carbonate in the formation to produce high viscosity fluid that will divert the fresh flow through the less permeable sections in the horizontal well. Parallel coreflooding experiments were used to confirm the diversion ability of this chemical through two sandstone cores with different permeability. The results obtained showed that the viscosity of the stimulation fluid increased at least 3 times after the treatment of the sandstone cores and the parallel coreflooding showed good ability of diversion for the fluid. The experimental results were used to describe the process of diversion using this fluid mathematically. HEDTA chelating agent showed good ability to remove the damage caused by drilling fluid from different sandstone cores with different permeabilities.

커피찌꺼기에 흡착된 은 이온의 탈착 및 재생 특성

질산, ethylene diamine triacetic acid (EDTA) 그리고 nitrilo triacetic acid (NTA)을 이용하여 폐기물인 커피찌꺼기에 흡착된 은 이온에 대한 탈착 특성을 조사하였다. 1.0 M의 질산용액을 이용하였을 때 가장 높은 97.8 %의 탈착율을 얻을 수 있었다. 또한, S/L 비가 1.0 이하일 경우, 커피찌꺼기에 흡착된 은 이온은 약 98~100 % 탈착되어졌으며 약 60분의 시간 내에 대부분의 탈착이 일어났다. 게다가 2번의 반복된 흡착 및 탈착 공정을 거친 후의 재사용된 커피찌꺼기의 은 이온에 대한 흡착능은 약 43.9 mg/g으로서 재사용전의 커피찌꺼기의 흡착능인 45.9 mg/g에 비해서 약 4.4%의 감소율을 보였다. This experiment was conducted to test desorption and recycling characteristics for silver ion adsorbed into waste coffee grounds by using various desorbing agents such as nitric acid, ethylene diamine triacetic acid (EDTA) and nitrilo triacetic acid (NTA). It is appeared that the highest desorption efficiency for silver ions was obtained as about 97.8 % by 1.0 M of nitric acid solution. Also, in the case of less than 1.0 of the ratio of solid and liquid (S/L) (g/L), silver ions adsorbed onto coffee grounds was desorbed as about 98~100 %, and most of desorption process was completed within 60min. In addition, adsorption capacity of reused waste coffee grounds for silver ions was highly maintained as about 43.9 mg/g until the <TEX>$2^{nd}$</TEX> cycle, as compared with the adsorption capacity with 45.9 mg/g of the adsorption capacity for virgin waste coffee grounds.

Chelating-Template-Assisted in Situ Encapsulation of Zinc Ferrite Inside Silica Mesopores for Enhanced Gas-Sensing Characteristics.

A facile in situ approach has been designed to synthesize zinc ferrite/mesoporous silica guest-host composites. Chelating surfactant, N-hexadecyl ethylenediamine triacetic acid, was employed as structure-directing agent to fabricate mesoporous silica skeleton and simultaneously as complexing agent to incorporate stoichiometric amounts of zinc and iron ions into silica cavities. On this basis, spinel zinc ferrite nanoparticles with grain sizes less than 3 nm were encapsulated in mesoporous channels after calcination. The silica mesostructure, meanwhile, displayed a successive transformation from hexagonal p6mm through bicontinuous cubic Ia3̅d to lamellar phase with increasing the dopant concentration in the initial template solution. In comparison with zinc ferrite nanopowder prepared without silica host, the composite with bicontinuous architecture exhibited higher sensitivity, lower detection limit, lower optimum working temperature, quicker response, and shorter recovery time in sensing performance toward hydrogen sulfide. The significant improvements are from the high surface-to-volume ratio of the guest oxides and the three-dimensional porous structure of the composite. We believe the encapsulation route presented here may pave the way for directly introducing complex metal oxide into mesoporous silica matrix with tailorable mesophases for applications in sensing or other fields.

Using Synthetic Chelating Agents to Decrease Phosphorus Binding in Soils

Most acid soils have a high capacity to bind phosphorus (P) strongly on iron (Fe) and aluminum (Al) hydroxides, resulting in low P fertilizer use efficiency. Organic chelating agents form strong bonds with metals in soil and may reduce P binding with Fe and Al and increase fertilizer P use efficiency. Ethylenediamine tetraacetic acid (EDTA), hydroxyethyl ethylenediamine triacetic acid (HEEDTA), gluconic acid, and citric acid were tested to determine their influence on water-soluble P (WSP), Mehlich-1 P, and Mehlich-3 P in a loam and sand fertilized with P and incubated for 49 days. Soil P sorption capacity (PSC) was estimated from an oxalate extraction of Fe and Al, and chelates were applied at rates of 90% of the PSC. EDTA and HEEDTA were also applied at 0, 30, 60, 90, 120, and 150% PSC to produce a rate response curve for WSP in a second soil incubation. The EDTA, HEEDTA, and citric acid significantly (P < 0.05) reduced P sorption in the loam and sand when measured by WSP. In soils without P fertilizer added, EDTA and HEEDTA resulted in a significant increase in WSP concentrations, as well as increased concentrations of Mehlich-1 P and Mehlich-3 P. With increasing chelation rates of EDTA and HEEDTA, there was a linear increase in WSP for both soils, indicating higher rates were most effective at decreasing P sorption. The application of chelating agents, with and without P fertilizer, could potentially increase plant availability of P, therefore reducing P fertilizer.