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Titanium dioxide nanoparticles (NPs) have become widely used and studied in industry, cosmetics, and water treatment; however, due to their surface charge and composition, uncoated nanoparticles often aggregate and settle in a solution. This leads to loss of function and suspension, abandoning the NPs' properties that make them ideal for many applications. Loss of NP suspension can also complicate analysis of solutions containing nanoparticles. Therefore, titanium dioxide nanoparticles are good candidates for surface coatings that enable hydrophilic interactions and improved suspension. Many coating processes require complex synthesis methods and begin with titanium dioxide precursors rather than with already synthesized nanoparticles. The method presented herein examines additive processes that may increase suspension capabilities and inhibit loss of function through aggregation of large nanoparticles (50 ± 25 nm). Nineteen chelating organic compounds were tested via a 1, 2, or 3 equivalent additions to pristine, unmodified TiO2 nanoparticles in solution. Furthermore, ligands that showed the best chelating behavior were diluted and the pH was modified to understand pH dependent behavior. Dynamic light scattering and electrophoretic light scattering were used in the study of the chemical behavior of the modified TiO2 nanoparticles. Results show that nanoparticles interacting with dimethylethanolamine, dimercaptosuccinic acid, sodium citrate, dimethylglyoxime, and oxalic acid showed improved ζ-potential at a pH of 5. Physico-chemical processes are discussed in the understanding of these results.

Previous studies have shown that ZnO nanoparticles (NPs) affect corn germination and root growth. However, there is a lack of information about the effects of these NPs at different temperatures. In this study, corn seedlings were exposed to ZnO NPs (24 ± 3 nm) at 0–1600 mg L − 1 and ionic Zn 0–250 mg L − 1 for 15 days. Germination, root elongation, Zn uptake and oxidation state, enzyme activity and protein expression were analyzed. At 20 and 25 °C, 400 mg ZnO NPs L − 1 significantly reduced the germination (40 and 53% respectively), while no effect of Zn 2 + was observed. Temperature and Zn concentration affected root growth. At 20 °C, ZnO at 50, 400, and 1600 mg L − 1 reduced root growth by 18, 47, and 26% respectively. At 25 °C, 100 and 800 mg L − 1 increased root growth by 22 and 27%, while at 30 °C, 100 mg L − 1 reduced root growth by 42%. At 30 °C, 0.1 mg L − 1 of Zn 2 + increased the growth by 50%. Zn accumulation in seedlings was significant only at 1600 mg L − 1 ZnO and 250 mg L − 1 Zn 2 + . Ascorbate peroxidase activity increased by 24 and 57% under exposure to ZnO at 400 and 1600 mg L − 1 at 25 °C. At any temperature the XAS analyses showed presence on NPs in roots. Exposure to ZnO NPs did not show changes in protein expression; however, a protein band with molecular weight of 85 kDa decreased its expression at 30 °C, while a protein of 75 kDa increased its expression at 30 °C. This study suggests that temperature may alter the way the ZnO NPs interact with plants.

Vanadium is included in the USEPA Contaminant Candidate List (CCL). Protonated chitosan flakes (PCF) were shown to effectively remove vanadium(III, IV, and V) oxyanions from aqueous solutions at high yields. It was also proven that the adsorption capacity of vanadium increases when using PCF instead of chitosan beads (CB). A 99–100% removal of vanadium oxyanions was achieved during the first 2 h of contact when using 5 g/L PCF adsorbent and the initial vanadium concentration of 0.500 mg/L, while CB only removed 4–18%. Adsorption experiments were performed by varying contact time, pH of the aqueous solution and adsorbent suspension solution, and analyzing the effect of common anions. Vanadium(III, IV and V) adsorption is favored in the Langmuir's model. These species of vanadium were removed efficiently without the need of pretreatment process, even when common anions were added, such as chloride, carbonate, sulfate and phosphate. The proposed mechanism for the removal of vanadium, when adding PCF, is by the process of electrostatic attraction.

Selenium (Se) is naturally occurring in the environment and is an essential nutrient in mammals. However, environmental Se can be increased to toxic levels through different industrial practices. The potential adsorption of the Se oxoanions, selenite and selenate, from aqueous solutions onto nanosynthesized MnFe 2 O 4 was investigated using batch techniques and DRC-ICP-MS spectroscopy. The nanomaterial (NM) was laboratory synthesized through slow titration of a mixture of Fe 2+ and Mn 2+ ions. X-ray diffraction and Scherrer's equation were used to determine the phase of the material and crystallite size, respectively. The effects of pH, reaction time, competitive anions, and the adsorption capacity of the synthesized NM to bind selenite and selenate were investigated. The Langmuir isotherm was used to determine the binding capacity of the NM. Results showed that the phase of the nanomaterial was similar to Jacobsite with a size of 27.5 nm. Results also showed that the sorption of either 100 ppb of selenite or selenate was pH independent in the pH range 2 to 6 and occurred within 5 min of contact time. The introduction of Cl − and NO 3 − anions individually added to solution had no significant effect on the sorption of either selenite or selenate. However, it was found that the addition of SO 4 2 − had a competitive effect only on the sorption of selenate, first seen at 10 ppm and more pronounced at 100 ppm of SO 4 2 − . In the presence of 100 ppm of PO 4 3 − , the adsorption of selenate decreased to 87% while selenite sorption decreased to 20%. From the Langmuir isotherm equation it was determined that the nano-Jacobsite had a selenite and selenate binding capacity of 6573.76 and 769.23 mg Se/kg of NM, respectively.

The potential of the Fe 3 O 4 , Mn 3 O 4 , and MnFe 2 O 4 nanophases for the removal of arsenic(III) and (V) from aqueous solutions was investigated using the batch technique. The structure and grain size of the nanoadsorbents were characterized using XRD and Secherrer's equation. The Fe 3 O 4 , Mn 3 O 4 , and MnFe 2 O 4 had the crystal structure of magnetite, hausmannite, and Jacobsite, while the grain sizes were 28, 25, and 12 nm, respectively. It was found that the sorption determined using 100 ppb of either As(III) or (V) was pH independent from pH 2 through pH 6. However, at pH below 3 the nanomaterials released high concentrations of iron and manganese into solution. The amount of both As(III) and (V) per gram of adsorbent was found to increase with increasing concentration of As in solution. The XRD analysis showed no decrease in the average grain size of the nanoadsorbents reacted with 1000 ppm of either As(III) or (V) or a combination of 500 ppm of each As species. Finally Fe 3 O 4 , Mn 3 O 4 , and MnFe 2 O 4 showed binding capacities (µg/g) of 32.2, 8.9, and 718 for As(III) and 1575, 212 and 2125 for As(V), respectively.

At present, there is a great interest in studying new sorbent materials for the removal of arsenic from aqueous solutions because of its high toxicity and adverse effects on human health. In previous research, sorghum biomass was found to be an efficient and economic sorbent for the removal of arsenic from aqueous solutions. In this investigation, the effects of CaCl2, MgCl 2, FeSO4, MgSO4, Fe(NO3) 3, and humic substances (peat moss, humin and humic acids) on arsenic binding to sorghum biomass were evaluated. Among these compounds, only iron salts were found to positively increase the sorption of arsenic to sorghum biomass. In addition, the sorption equilibrium was reached faster when the reaction mixture contained iron salts. However, an overall reduction of 21% of arsenic sorption to sorghum biomass was observed in the presence of MgSO 4. This interference may be due to the presence of sulfate ions, instead of the hard cations, that could be in competition with As for the same interaction sites or ligands. Peat moss, humins and humic acid, extracted from sphagnum peat moss, significantly decreased the arsenic sorption to sorghum biomass.

Previous studies have shown that hop biomass is capable of adsorbing significant amounts of Au(III) from aqueous solutions. Hop biomass was chemically modified to determine the contributions that the different functional groups on the biomass have on the binding and reduction of Au(III). Previously, performed batch studies showed that Au(III) binding is fast, occurring within the first 5 min of contact and in a pH dependent manner. However, esterified hop biomass behaved in a pH independent manner and the binding was found not to change with changing pH. However, the hydrolyzed biomass had a similar Au(III) binding to the native hops biomass, showing a pH dependent binding trend. X-ray absorption spectroscopy (XAS) analysis, XANES (X-ray absorption near edge structure), and EXAFS (extended X-ray absorption fine structure) were used to determine the oxidation state, coordination environment, and the average radii of the gold nanoparticles bound to the hops biomass. The XAS data confirmed the presence of Au(0) in both the native and chemically modified hop biomasses. XANES fittings show that the Au(III) was reduced to Au(0) by approximately 81%, 70%, and 83% on the native, esterified, and hydrolyzed hop biomass, respectively. In addition, the calculation of the particle radius was also in agreement with the results of previously performed transmission electron microscopy studies. The average particle could only be calculated for the native and esterified hops biomass, which showed average particle radii of 17.3 A and 9.2 A, respectively.

In this research, the phorbol ester, phorbol 12-myristate 13-acetate (PMA), was used to assess the effect of protein kinase C (PKC) activation on the specific activity of ecto-5′-nucleotidase (eNT) in human lymphocytes. PMA mimics the effects of diacylglycerol, a natural compound released by the hydrolysis of the glycosilphosphatidilinositol (GPI) moiety, in activating PKC. In order to evaluate the activity of eNT in living lymphocytes, a micro-assay method was established with a low detection limit for inorganic phosphate (Pi) of 0.94 nmol Pi assay−1. The dephosphorylation of Adenosine monophosphate (AMP) by functional lymphocytes was evaluated and the contribution of the eNT activity was calculated by its inhibition with the specific eNT inhibitor α,β-methylene ADP (MADP) and the use of the broad spectrum phosphatases inhibitor (but not eNT), levamisole. Under the conditions tested, we obtained an AMPase value of 8.05±4.4 nmol Pi million cells−1 h−1. The addition of MADP to the incubation media decreased the AMPase activity to 2.43±0.9 nmol Pi million cells−1 h−1 (p

Studies were performed to determine the effect of pH on chromium (Cr) binding by native, esterified, and hydrolyzed saltbush (Atriplex canescens) biomass. In addition, X-ray absorption spectroscopy studies were performed to determine the oxidation state of Cr atoms bound to the biomass. The amounts of Cr adsorbed by saltbush biomass were determined by inductively coupled plasma–optical emission spectroscopy (ICP–OES). For Cr(III), the results showed that the percentages bound by native stems, leaves, and flowers at pH 4.0 were 98%, 97%, and 91%, respectively. On the other hand, the Cr(VI) binding by the three tissues of the native and hydrolyzed saltbush biomass decreased as pH increased. At pH 2.0 the stems, leaves, and flowers of native biomass bound 31%, 49%, and 46%, of Cr(VI), respectively. The results of the XAS experiments showed that Cr(VI) was reduced in some extend to Cr(III) by saltbush biomass at both pH 2.0 and pH 5.0. The XANES analysis of the Cr(III) reaction with the saltbush biomass parts showed an octahedral arrangement of oxygen atoms around the central Cr(III) atom. The EXAFS studies of saltbush plant samples confirmed these results.

Results of using a field spectrophotometer and its appropriate protocols as a surrogate method for an oilfield produced water treatment process is presented. Methylene chloride extractions of the produced water before and after treatment maintained a yellow color pigment that was directly proportional to the hydrocarbon concentration. From this, an absorption spectrum and standard curve were developed. A resultant linear plot of the standard curve indicated that there is an excellent correlation (r2=0.9847) between the varying concentrations and the associated absorbance values at a wavelength of 400 nm. Total n-alkane concentration comparisons between the laboratory GC/MS analysis and the spectrophotometry analysis generated data of similar accuracy and precision at concentrations ranging from 1 to 137 mg/l (alpha=0.05). Linear comparisons between GC/MS and spectrophotometric coefficients were near unity, with the constant being near zero, with a correlation coefficient (r2) of 0.99. Based on this study, spectrophotometry is a complimentary method to GC/MS for determining total n-alkane concentrations in oilfield produced water samples.

Utilizando detectores de carbon activado y electrets, se midieron concentraciones en 12 ubicaciones diferentes de Mexico, en casas particulares a traves del Estado de Chihuahua. Ademas de estas mediciones a corto plazo tambien se llevaron a cabo mediciones a largo plazo alrededor de las ciudades de Chihuahua y Aldama utilizando el detector LR-115 II, y para comparar, fueron colocados detectores LR-115 II entre Ciudad Juarez (Mexico) y El Paso (Texas). Se obtuvieron valores promedio significativos en Aldama y Parral de 225 y 173 Becquerel por metro cubico (Bq m-3), respectivamente. Mas del 30% de las casas en las que se tomaron muestra en Aldama, Cuauhtemoc, Parral y Chihuahua tuvieron concentraciones de radon mayores a los 148 Bq m-3.

It is common for samples to be cooled to near liquid He temperature (4 K) during measurement of their X-ray absorption spectra (XAS). This procedure is believed to improve spectrum quality either by minimizing radiation damage, or by decreasing thermal motions of atoms. The actual benefits realized by cooling are rarely assessed, since that would require duplicate measurements at multiple temperatures, followed by duplicate data analyses. With a cryostat installed, it is difficult to measure room temperature or hotter spectra, which often requires removing the cryostat from the beam path. Here we investigate the effect of cooling and show that it is not globally useful in X-ray absorption spectroscopy. Photolysis does not occur, or its consequences are not controlled by cooling. Secondary photochemical damage is delayed and is remote from the absorption site. Thermal motions do not usually contribute significantly to disorder and consequent damping of EXAFS, either because vibrational amplitudes are small, or because static disorder and structural complexity affect EXAFS in the same way but more profoundly. The low probability of photochemical effects on XAS is in contrast to the situation with crystallography of biological specimens, where photochemical damage anywhere in the sample degrades the data set regardless of proximity to atoms of one specific element. Thermal disorder becomes important in certain types of samples and when the Debye–Waller factor is itself used as a tool. In most cases, it is more efficient to first measure room temperature spectra, and then repeat measurement using a cryostat of only those spectra where the objectives of the analysis justify an attempt to gain more information.

Traditional treatment methods used to clean-up heavy metal contamination of soils and waters are cost intensive whereas more cost effective methods need to be developed. The use of plant materials to remediate heavy contamination has been studied for the past two decades. This technique has shown much promise for many of the common heavy metal contaminants, but few studies have focused on the lanthanide series elements. By investigating the binding and interactions of the lanthanide elements to alfalfa biomass, a more complete understanding of the binding mechanisms and the interactions of heavy metals with biomaterials can be obtained. Different chemical functional groups on the alfalfa biomass, carboxyl, amino, sulfur, and ester groups, were modified to investigate the binding mechanisms of erbium(III) and holmium(III). Batch experiments were performed with native and chemically modified alfalfa biomass suggesting that the carboxyl groups play a major role in the binding of erbium(III) and holmium(III) to the alfalfa biomass. In addition, X-ray absorption spectroscopy (XAS) studies corroborated the data obtained from the batch experiments.

Previous studies have shown that alfalfa biomass possesses the potential to be a biosorbent for chromium(III) removal from contaminated and industrial wastewaters. However, the mechanism through which chromium(III) binds to alfalfa biomass has not been identified. Therefore, studies were conducted to determine how modification of chemical groups present on the alfalfa biomass affect the chromium(III) binding. Batch pH profile studies were performed on esterified, hydrolyzed and unmodified alfalfa biomasses. A comparison study with ion exchange resins containing carboxyl, thiol, amino, sulfonic, and phosphate groups were also performed. These studies showed that chromium(III) binds predominantly to the alfalfa biomass through carboxyl ligands and follows a binding trend similar to that of the carboxyl resin. In addition, Fourier transform infrared spectroscopy (FTIR) studies were conducted in order to better understand how the chemical modification affects the alfalfa biomass and the mechanism(s) by which chromium(III) binds to alfalfa. From these experiments, it was determined that chromium(III) may be coordinating with carboxyl ligands present on the surface of the alfalfa biomass through a bridging bidentate complex. X-Ray absorption spectroscopy (XAS) studies were also performed, which corroborate with batch modification and ion exchange resin comparison studies, further indicating carboxyl involvement in chromium(III) binding by inactivated alfalfa biomass.

Previous experiments showed that inactivated alfalfa biomass is proficient in the recovery of gold(III) from aqueous solutions. Gold(III) binding to alfalfa biomass is rapid, pH independent, and increases with temperature. Also, X-ray absorption spectroscopy studies showed that alfalfa was able to reduce gold(III) to gold(0), producing nano-particles. This current study was performed to gain a better understanding of the interaction between gold(III) and the alfalfa biomass. Through chloride ion release studies, it was found that three moles of Cl− were released per mole of gold adsorbed. Chemical modification of the alfalfa biomass indicated that both amino and carboxyl functional groups on the alfalfa biomass are involved in the reduction process. Finally, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy studies suggested that gold(III)is initially reduced to gold(I) and is eventually reduced to gold(0); in addition, the X-ray spectroscopic studies indicated that binding may be occurring through a nitrogen or oxygen ligand.

Traditional methods currently employed to remediate heavy metal contaminated waters prove to be cost prohibitive. Therefore, more cost-effective methods of remediating heavy metals from contaminated waters need to be developed. The use of plant materials as metal adsorbents may be a possible solution. Previously performed experiments have shown that alfalfa shoot biomass can bind an appreciable amount of heavy metal ions, even from multi-contaminate containing solutions. Although the alfalfa biomass has shown to be very effective at removing heavy metal ions from aqueous solution, more research is needed to understand the metal binding mechanism. Carboxyl groups were chemically modified in order to determine their contribution to the metal binding process. Batch experiments were performed with the modified biomass and suggest that carboxyl groups play a significant role in the binding of lead(II). In addition, X-ray absorption spectroscopic analysis (XANES and EXAFS) corroborate these results. These studies are important for determining the ligands that may be involved in the binding of lead ions to alfalfa biomass, thus aiding in our understanding of the mechanisms involved in the removal and recovery of metal ions from contaminated waters through phytofiltration.

In this study, isolated cell wall material and lyophilized whole cells of the cyanobacterium Anabaena flos-aquae (ATCC 22664) were examined for their ability to bind Cu ions. Experiments were performed to gain insight on the chemical groups that may be involved in the binding of Cu ions. We have taken advantage of physical/chemical tools, which allowed us to identify these groups at the atomic level. Atomic absorption spectroscopy was utilized to determine the Cu ion binding capacity of the two biomaterials as a function of pH. Both biomaterials showed a substantial amount of Cu ion binding at pH 5 (26.8 mg/g of biomass for the whole cell group and 90.4 mg/g for the cell wall group). X-Ray absorption spectroscopy was used to determine the speciation of Cu ions bound by cell wall and whole cell materials as well as to elucidate which functional groups were involved in binding of the Cu ions. X-Ray absorption near-edge spectra showed that the majority of the Cu was bound in both biomaterials as Cu(II) and also suggested that Cu(II) ions are binding to oxygen ligands in an environment resembling that of Cu(II) acetate monohydrate.

Due to the increasing concentrations of heavy metals in potable water and industrial wastewater governmental agencies have created stricter regulations for the treatment of metal contaminated waste. However, current technologies are both expensive and time consuming to use for water and waste treatment. As an alternative to the current technologies, phytofiltration has been proposed, but to make phytofiltration effective the process must be further studied to better understand the metal–biomass chemical interactions. This current study on the use of hops biomass to remove heavy metal ions from aqueous solutions uses X-ray absorption spectroscopy (XAS) to investigate the binding mechanism of heavy metals to hops biomass. The XAS studies showed that copper(II), zinc(II) and chromium(III) remained in the same oxidation state as when they were reacted with the hops biomass. However, the reaction of chromium(VI) with the hops biomass resulted in the reduction of chromium(VI) to chromium(III). Analysis of the XAS spectra showed that copper(II) bound to the hops biomass with a molecular geometry of copper(II) acetate; zinc(II) bound to the hops biomass with a molecular geometry of zinc(II) gluconate; and chromium(VI) bound to the biomass with the geometry of chromium(III) acetate. In addition, the XAS studies showed that the nearest neighboring atom of all the bound metal ions was an oxygen atom.

Contamination caused by heavy metals as well as their toxic effects on the environment and mankind is well known. However, it has been observed that some native plants have survived within areas polluted with heavy metals. This has been the case with the woody subshrub Solanum elaeagnifolium. It is possible to take advantage of this singular feature by using its inactivated tissues as a biofiltration system. In this work we characterized the mechanism of the binding between the biomass tissues with heavy metals by using chemical modification techniques. These techniques included chemical esterification and hydrolyzation of carboxylic groups and methyl esters, respectively. These studies have shown an overall decrease in metal binding for the esterified biomass, and an overall increase in metal binding for the hydrolyzed biomass as compared with the unmodified biomass. These experiments were performed with Cu(II), Pb(II), Cr(III), Zn(II) and Ni(II). In addition, experiments conducted with modified biomass at different pH conditions were done in order to corroborate the biomass modification results. Also, we used X-ray absorption spectroscopy techniques (XANES and EXAFS) to elucidate the mechanism(s) of metal ion binding.

Europium(III) is a common product found in nuclear wastes. Recent investigations into the use of europium compounds as cancer therapy treatments have proven promising. In this study, europium(III) nitrate binding studies were performed using unmodified and esterified alfalfa biomass. Batch experiments included pH profile studies and X-ray absorption spectroscopy (XAS) inspection to determine the functional groups responsible for the binding of europium(III) nitrate on alfalfa. Results from the pH profile study showed that approximately 80% of the europium(III) nitrate bound to the native alfalfa biomass while the esterified biomass showed approximately 40% binding at pH 5. XAS consists of two complementary components: X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). The XAS experiments were performed using the europium LIII edge which had an energy of 6.977 KeV. The XANES spectra showed that there were some changes in the characteristics of the europium(III) nitrate when bound to the modified and unmodified alfalfa biomass. No change in the europium(III) oxidation state was observed after europium(III) binding to the alfalfa biomass. EXAFS spectra showed that europium(III) nitrate binds to the alfalfa biomass via a nitrogen or oxygen ligand with bond lengths ranging from 2.44 to 2.49 A. However, chemical esterification experiments show that oxygen may be the primary ligand for coordination. The coordination numbers for all samples and compounds tested were approximately 9.

Current technologies used to extract heavy metals from the environment have proven to be expensive and have adverse health effects. Thus there is a need to develop techniques to extract metal ions from the environment in an inexpensive manner while reducing any potential adverse health effects. Because of this need to develop new technologies to extract metals from the environment, research has turned to novel methods such as phytofiltration, phytoextraction and bioaccumulation of metals. Alfalfa biomass has proven to be a plant that has the ability to adsorb heavy metals from solution in appreciable amounts. However, the majority of these studies have only investigated the adsorption of high concentrations of metal ions. Nevertheless, few studies have been performed at trace levels. Batch experiments were performed on the alfalfa biomass to investigate the sorption of trace levels of copper (100 ppb) from solution. The metal analyses were performed using a graphite furnace atomic absorption spectroscopy (GFAAS) with Zeeman background correction. Additional batch experiments were performed to characterize the optimal binding pH and time exposure required for copper(II) adsorption by alfalfa biomass. The optimum binding pH was found to be around pH 5.0, with 95% binding of the copper(II) from solution. Also, a maximum binding was found to occur within the first 5 min of contact which remained constant for 1 h. In addition, batch interference studies were performed which showed little binding interference with varying concentrations of calcium, magnesium and sodium ions (as high as 1000 ppm). The results of these experiments at trace copper(II) levels were very similar to those performed at higher copper(II) levels. This may indicate that similar functional groups (e.g. carboxyl groups) are involved in copper binding by the alfalfa biomass at low and high copper concentrations. The information gained in this study allowed us to determine the efficiency of alfalfa biomass to bind copper ions at trace concentrations.