Ammonium Oxalate Research Articles

Disaggregation of Nanosized Powders

Disaggregation of nanosized powders synthesized in liquid media is an urgent task of modern industry. On the example of nanoboehmite suspensions obtained by hydrothermal treatment of various precursors, there have been proposed new methods of disaggregation by introducing ammonium citrate or oxalate or microcrystalline cellulose into the suspension or by bubbling CO2 through it. Subsequent heat treatment of the modified boehmite powder gives a γ-Al2O3 nanopowder, and its technical characteristics are reported.

Utilization of coffee pulp waste for rapid recovery of pectin and polyphenols for sustainable material recycle

Coffee pulp is one of the major underutilized byproduct of coffee processing in farm level. Disposal of this agro-industrial waste has become one of the most challenging tasks for coffee planters. However, most of the efforts are towards the management of coffee pulp as an effluent, and not-on re-use. The problem is compounded due to the large volumes produced in diluted forms, which makes it expensive to reuse. The preliminary proximate analysis of coffee pulp indicated it to be rich in pectin and polyphenols. The efficacy of various chemicals like ethanol, sulfuric acid, hydrochloric acid, nitric acid, ammonium oxalate and metal salts for effective precipitation of pectin from coffee pulp was evaluated. HPLC characterization of the extracted and concentrated polyphenols fractions was analyzed. The maximum extraction of pectin was achieved by using metal salts and ethanol with 6.0% and 6.7% on wet weight basis respectively. The equivalent weight of extracted pectin (1180.5 mg/g) was found to be higher than that of commercial pectin (724.8 mg/g). The methoxyl content of the commercial pectin and crude pectin were 9.3 and 5.6% respectively. Gallic, vanillin, catechin, ethyl catechol, coumaric, Caffeic, and ferulic acid were the major polyphenols as quantified by the HPLC. The polyphenol fraction showed a good antioxidant activity with phosphomolybdate, FRAP, DPPH, and ABTS radicals respectively. The sustainable utilization of coffee pulp as a source of pectin and polyphenols with good antioxidant activities could help to solve the problem of waste generated in coffee processing in farm level.

Comparison of physicochemical properties and economic gain from three‐stage and two‐stage sequential valorization of mango peels

AbstractThree‐stage sequential extraction of anthocyanins, polyphenols, and pectin has the potential to enhance the product's functional properties and the economic value of mango (Mangifera indica L.) peels beyond the two‐stage processes (anthocyanin‐pectin and polyphenol‐pectin). A three‐stage process was developed by incorporating a polyphenol extraction stage in a sequential process where anthocyanins and pectin were co‐extracts. Anthocyanins were extracted first (80% ethanol (EC)/2% acetic acid/25 °C/1 h), generating a residue from which polyphenols were extracted (65–85% EC/20–80 min/70 °C), based on a full factorial statistical experiment. Pectin was subsequently extracted from the second‐stage residues (0.25% ammonium oxalate / oxalic acid / 85 °C / 1 h). The economic benefits (net present value (NPV), payback period (PBP), product minimum selling price (PMSP) of the three‐stage sequential process (anthocyanin, polyphenol, and pectin) and the two‐stage processes (anthocyanin‐pectin and polyphenol‐pectin) were evaluated over a plant life of 25 years. Polyphenols and pectin from the three‐stage process had >65% higher antioxidant capacity and up to 10.4% higher purity, respectively, when compared with those from the two‐stage processes. There is also more economic gain from the three‐stage process (NPV −$4 31 285, PBP −3 years, PMSP < $10/kg) than the anthocyanin‐pectin process (NPV −$3 76 917, PBP −3.22 years, PMSP < $10/kg) and the polyphenol‐pectin process (NPV −$235 599, PBP −4.29 years, PMSP < $30/kg). Thus, three‐stage sequential extraction is an economic process, which enables the recovery of three value‐added food ingredients with improved functional properties from mango peels.© 2020 Society of Chemical Industry and John Wiley & Sons, Ltd

Online Sequential Fractionation Analysis of Arsenic Adsorbed onto Ferrihydrite by ICP-MS.

Fractionation information on arsenic (As) in complex samples, particularly solid samples, is of immense interest. Herein, selective extraction of various As species adsorbed onto ferrihydrite as the model substrate was online-adapted to inductively coupled plasma-mass spectrometry (ICP-MS) for sensitive detection. The As-adsorbed ferrihydrite sample was loaded into a homemade online sequential elution device using two commercially available micropipette tips, and then, each fraction of As including nonspecifically adsorbed, specifically adsorbed, iron oxide bonded, and residual species was successively extracted for ICP-MS detection, with H2O, NH4NO3, NH4H2PO4, ammonium oxalate, and HF as the eluents, respectively. While no water-soluble As was detected, the fraction of As bonded to iron oxide was detected as the dominant species (>80%), and the specifically adsorbed As and residual As also accounted for a substantial amount (10%). The method had a detection limit of 0.008 μg/kg for As(III) and 0.013 μg/kg for As(V), with merits such as extremely low sample consumption, high throughput, and minimized experimental manipulation, presenting an alternative strategy for sensitive fractionation analysis of As adsorbed onto solid substrates (e.g., iron oxides, etc.).

Adsorption/Desorption Patterns of Selenium for Acid and Alkaline Soils of Xerothermic Environments

Selenium adsorption/desorption behavior was examined for eight Greek top soils with different properties, aiming to describe the geochemistry of the elements in the selected soils in terms of bioavailability and contamination risk by leaching. Four soils were acid and four alkaline, and metal oxides content greatly differed between the two groups of soils. The concentrations of Se(IV) used for the performed adsorption batch experiments ranged from 1 to 50 mg/L, while the soil to solution ratio was 1 g/0.03 L. Acid soils adsorbed significantly higher amounts of the added Se(IV) than alkaline soils. Freundlich and Langmuir equations adequately described the adsorption of Se(IV) in the studied soils, and the parameters of both isotherms significantly correlated with soil properties. In particular, both KF and qm values significantly positively correlated with ammonium oxalate extractable Fe and with dithionite extractable Al and Mn, suggesting that amorphous Fe oxides and Al and Mn oxides greatly affect exogenous Se(IV) adsorption in the eight soils. These two parameters were also significantly negatively correlated with soil electrical conductivity (EC) values, indicating that increased soluble salts concentration suppresses Se(IV) adsorption. No significant relation between adsorbed Se(IV) and soil organic content was recorded. A weak salt (0.25 M KCl) was used at the same soil to solution ratio to extract the amount of the adsorbed Se(IV) that is easily exchangeable and thus highly available in the soil ecosystem. A much higher Se(IV) desorption from alkaline soils was observed, pointing to the stronger retention of added Se(IV) by the acid soils. This result implies that in acid soils surface complexes on metal oxides may have been formed restricting Se desorption.

Comparing measures for determination of phosphorus saturation as a method to estimate dissolved P in soil solution

In response to concerns over the translocation of P from soils to P-sensitive water bodies, there is high demand for developing simple indicators for evaluating a soil’s risk of releasing P into solution. Many studies have shown that the degree of soil phosphorus saturation (DPS), calculated as the ratio of soil P concentration to soil P sorption capacity (PSC), is good predictor of a soil’s risk of releasing P in solution. In this study we compared four different DPS indices in how well they predicted dissolved P following extraction with either a 0.01 M CaCl2 (PCaCl2) solution or deionized water (PW). The first two indices were calculated from the ratio of extractable P to extractable Al and Fe using either acid ammonium oxalate (AlOX + FeOX) or ammonium lactate solutions (AlAL + FeAL). The second two DPS indices were calculated from the ratio of either Olsen-extractable P or AL-extractable P with sorption capacity estimated from the single point P sorption index (PSI). On a subset of 11 soils, we compared the different methods for estimating PSC with fitted Langmuir sorption maximum (Smax) using data from complete sorption isotherms. Both (AlOX + FeOX) and PSI were well correlated with Smax and hence regarded as good estimates for P sorption capacity. Conversely, (AlAL + FeAL) was not significantly correlated with Smax. P saturation calculated from PSI together with PAL or POls predicted PCaCl2 and PW best, whereas P saturation calculated from ammonium oxalate predicted PCaCl2 and PW the least. We did not find notable improvements in the regression models when we added a second explanatory variable (clay content, pH or total carbon) to the models. Our results show that multiple measures of P saturation provide similar predictions of a soiĺs potential for releasing dissolved P into soil solution. This provides flexibility in how P saturation indices are calculated to identify leaching prone hotspots.

Assessing the Reactive Surface Area of Soils and the Association of Soil Organic Carbon with Natural Oxide Nanoparticles Using Ferrihydrite as Proxy.

Assessment of the surface reactivity of natural metal-(hydr)oxide nanoparticles is necessary for predicting ion adsorption phenomena in soils using surface complexation modeling. Here, we describe how the equilibrium concentrations of PO4, obtained with 0.5 M NaHCO3 extractions at different solution-to-soil ratios, can be interpreted with a state-of-the-art ion adsorption model for ferrihydrite to assess the reactive surface area (RSA) of agricultural top soils. Simultaneously, the method reveals the fraction of reversibly adsorbed soil PO4 (R-PO4). The applied ion-probing methodology shows that ferrihydrite is a better proxy than goethite for consistently assessing RSA and R-PO4. The R-PO4 pool agrees well with ammonium oxalate (AO)-extractable phosphorus, but only if measured as orthophosphate. The RSA varied between ∼2 and 20 m2/g soil. The corresponding specific surface area (SSA) of the natural metal-(hydr)oxide fraction is ∼350–1400 m2/g, illustrating that this property is highly variable and cannot be represented by a single value based on the AO-extractable oxide content. The soil organic carbon (SOC) content of our top soils increases linearly not only with the increase in RSA but remarkably also with the increase in mean particle size (1.5–5 nm). To explain these observations, we present a structural model for organo-mineral associations based on the coordination of SOC particles to metal-(hydr)oxide cores.

Weirs Control Phosphorus Transfer in Agricultural Watersheds

Sediments may act as a source or sink of ions from water, especially phosphorus (P). After the erosion process, the challenge is to retain suspended sediments inside the watershed area. We hypothesize that weir structures may mitigate P transfer from agricultural soils to aquatic systems. To test this, the present work aimed to evaluate P chemical fractions present in bottom sediments retained in the water reservoir of weirs built in two intensive agricultural watersheds and we discuss the sink/source behavior of these sediments. Samples of bottom sediments were collected from 12 reservoirs of weirs in two smalls Brazilian watersheds. Chemical P fractionation including adsorption and desorption kinetics was performed. Total P varied from 398 to 958 mg kg−1. The easily and potentially desorbed phosphorus were correlated with the clay content and the concentrations of Fe, Mn, and Al, extracted by ammonium oxalate and dithionite-citrate-bicarbonate solutions, which are the carriers of highly reactive functional groups with phosphate. Bottom sediments have high maximum adsorption capacity under unrestricted phosphorus supply condition, while under natural condition (low anthropogenic pressure), the sediments were not saturated and therefore low desorption occurred. Only 1.34% and 7.75% of total P was in readily and potentially bioavailable P forms. The bottom sediments accumulated in reservoirs from anthropogenic areas acted as P source to water, while those from preserved areas (natural pasture or riparian forest) acted as sink of P from water. The storage of water and sediment contaminated with P in reservoir of weirs may be an efficient and temporary practice to mitigate the transfer of P to watercourses.

Sediment detachment in piping‐prone soils: Cohesion sources and potential weakening mechanisms

AbstractSoil piping is a widespread land degradation process that may lead to gully formation. However, the processes involved in sediment detachment from soil pipe walls have not been well studied, although their recognition is a crucial step to protect soils from piping erosion. This study aims to recognize the factors affecting cohesion and to identify the mechanisms which are likely to be responsible for the disintegration of soil. The study has been conducted in mid‐altitude mountains under a temperate climate (the Bieszczady Mountains, the Carpathians, SE Poland). The research was based on the detailed field and laboratory analyses of morphology, and the physical and chemical properties of soil profiles with and without soil pipes. Moreover, experiments with flooding the undisturbed soil samples using different solutions (deionized water, ammonium oxalate, dithionate citrate, 35% hydrochloric acid and 30% hydrogen peroxide) were conducted in order to check the role of air slaking, the removal of soil organic carbon (SOC), and Fe and Al oxides on sediment detachment. The obtained results have confirmed that soil pipes develop in quite cohesive soils (silt loams), which allow the formation and maintenance of pipes with a diameter up to 30 cm. Soil cohesion, and thus susceptibility to piping, are impacted by the content of major oxides, soil particle size distribution, biological activity and porosity. The tested soils affected by piping erosion have a lower content of Al2O3 and Fe2O3, and free Fe (Fe(DCB)), lower clay content, higher biological activity (more roots and animal burrows), higher porosity, and more and larger pores than the profile without soil pipes. The experiments have indicated that especially SOC along with Fe and Al oxides are an important cohesion source in the study area. This suggests that the removal of SOC, and Fe and Al oxides may weaken and disintegrate aggregates in soil pipes. Further study of soil leaching and tensile strength will broaden understanding of which chemical processes control where pipes will develop in other cohesive piping‐prone soils. © 2020 John Wiley & Sons, Ltd.

Soil Physicochemical Properties and Geochemical Indices: Diagnostic Tools for Evaluating Pedogenesis in Tephra-Derived Soils along the Cameroon Volcanic Line

Physical and geochemical properties of six soils developed on tephra from Mts. Kupe and Manengouba were studied in order to assess the degree of weathering of the tephric parent materials. Physico-chemical properties were determined following standard procedures. Total elemental contents and selective extracted contents of Al and Fe by acid ammonium oxalate, dithionite-citrate-bicarbonate (DCB) and pyrophosphate were determined using inductively coupled plasma optical emission spectroscopy (ICP-OES) after being brought into solution. Parent rocks were chemically classified as hawaiite, tephricfoidite, and basanites, while soils were classified as Andosols and Cambisols. Both the soils and parent rocks have high concentrations in SiO2, Al2O3, and Fe2O3. Texture and the evaluated related weathering indices correlate with horizon development and are important in capturing the differences between the two Reference Soil Groups. Mobility of major elements showed erratic trends in conformity with the stratigraphic breaks indicating variability of parent materials with depth. Enrichment and depletion of major elements to a certain degree explains the ongoing andosolization process in the Andosols. Physical and geochemical data can both be used concomitantly for assessment of weathering trends in these soils. Total reserve in bases (TRB) is very high in the Andosols indicating the presence of large quantities of weatherable minerals and thus the high potential of these soils for agricultural production.

Enhanced lipase production from organic solvent tolerant Pseudomonas aeruginosa UKHL1 and its application in oily waste-water treatment

Abstract Lipase, as a handy hydrolytic enzyme, is gaining importance in environmental management like oil and fat-containing wastewater treatment. In this study, we have focused on cost-effective production of lipase by Pseudomonas aeruginosa UKHL1 and its applicability in oily wastewater treatment. Plackett-Burman randomized factorial design with 20 experiments recognized ammonium oxalate, peptone, yeast extract, coconut oil, NaCl, and CaCl2 as significant factors among the screened 13 factors by one factor at a time approach (OFAT). Further fine-tuning of three most significant media components (ammonium oxalate (0.01% w/v), peptone (0.246% w/v) and coconut oil (0.1% v/v)) was done by Central Composite Design experiment of Response Surface Method with 20 runs. Lipase production by P. aeruginosa UKHL1 was improved 9.4 and 3.91-fold after 24 h and 36 h, respectively under optimized conditions. Strain in this study also showed good tolerance to iso-octane and n-hexadecane solvents having higher log_P value. P. aeruginosa UKHL1 strain degraded 37% oil after 72 h in an experimental setup under laboratory condition.

Study of organic-matter intercalated vermiculitic phases in the hydromorphic red earth sediments

Al-hydroxy intercalated vermiculitic phases have been widely observed in pedogenic environment, but soil organic intercalations have rarely been reported. In the present study, mixed-layer illite–vermiculite (I/V) with organic matter (OM) intercalation under hydromorphic conditions in the Xuancheng red earth sediments was investigated in order to better understand the interlayer components occurring in mixed-layered clay minerals and the formation of this unusual OM interlayered mixed-layer clay species. Selective extraction of organic fillings by ammonium ethylene diamine tetraacetic acid (EDTA) and acid ammonium oxalate (NH4OX) showed that the components associated with organic complexes in the interlayer space of the 2:1 clays are mainly Fe- and A1-(oxy)hydroxides, which block substantial swelling after ethylene glycol solvation and complete collapse after heating. The OM interlayer filling contains CH3(CH2), CO, COO-, and NH functional groups and are resistant to H2O2 extraction although the binding intensity to the interlayer surface may change. Upon heating to ~300 °C the OM filling escapes from the interlayer space which causes the collapse of the 2:1 clay species. Alteration of primary illite during pedogenesis causes release of K and intercalation of hydrated cations in the interlayer space, and also leaching of Al and Fe. There is accumulation of exchangeable cations and Al and Fe oligomers in the interlayer region, which affects the behavior of I/V clays on glycolation and heating. Hydromorphic conditions favor the transformation of organic polymers into small size organic acids, and thus, favor the intercalation of interlayer OM filling into the 2:1 clays. Pedogenesis processes involves both the weathering of clay minerals and the decomposition of OM, leading to formation of interlayer clay-organic complexes in a hydromorphic soil.

Rheological characterization of RG-I chicory root pectin extracted by hot alkali and chelators

This work aimed to extract gelatinous chicory root pectin (CRP) and evaluated the rheological behavior of the dispersions and gels. CRP was extracted by citric acid (CEP), alkaline (AEP), ammonium oxalate (OEP) and sodium citrate (SEP). The yield, molecular weight (Mw) and the degree of esterification (DE) of pectin samples varied from 8.8 to 14.8% (w/w), 204 to 336 k Da and 4.0 to 47.4%, respectively. AFM studies showed self-organize on mica of CEP, revealing a random coil conformation due to the interaction of multiple branching, whereas, AEP exhibited long linear filamentous structures. The flow behavior study verified the pseudoplastic character of CEP and SEP at 25 °C, while OEP and AEP belonged to dilatant fluid, besides, a closed hysteresis loop was observed when the CEP concentration increased to 1.5%. OEP gel was thermo insensitive and stiff, AEP gel presented most sensitive to calcium ion but more brittle, and SEP was observed a weak syneresis in spite of the poor gelation property. The texture analysis indicated OEP gel had a superior firmness and chewiness. These findings demonstrated that CRP may be attractive as a thickener or gelling agent to modulate textures of sugar-free and calcium content food.

Na+-induced gelation of a low-methoxyl pectin extracted from Premna microphylla Turcz

In this paper, Na+-induced gelation of a low-methoxyl pectin extracted from Premna microphylla Turcz were studied by rheological analysis, texture test, microstructure observation, thermodynamics study and gelling forces analysis. The results showed that Na+ could induce the gelation of ammonium oxalate extraction pectin from Premna microphylla Turcz (AOP) at room temperature. Besides, The Na+ concentration had a significant effect on the generation of AOP gel. There was an optimal Na+ concentration (0.6 M) for AOP to form a gel with the highest solid-like properties, water holding capacity (WHC) and crystallinity. With the further increase of Na+ concentration from 0.6 M to 0.7 M, the gel properties of the pectin gel would be weakened. Gelling forces analysis revealed that Na+-induced gelation of AOP was mainly caused by electrostatic shielding and hydrogen bonds. When sufficient content of Na+ was added to AOP, the electrostatic shielding effect of Na+ would reduce the expansion degree of AOP chains and make the pectin molecules get close to each other. Subsequently, hydrogen bonds in and between the pectin chains would be formed, thus building up the gel. The results of this study can provide references and methods for the mechanism study of monovalent cation-induced gelation of pectin.

Diethyl Oxalate-based Microgrouts in Calcium Carbonate Systems: Formulation and Application Parameters

ABSTRACT During field development of a microgrout for the stabilization of painted lime plasters detached from a limestone substrate, diethyl oxalate-based formulations out-performed microgrouts based on nanolime, colloidal silica and ammonium oxalate, creating more cohesive and homogenous set materials, with better working properties. However, unlike ammonium oxalate, diethyl oxalate is relatively new to the field of conservation, and therefore requires extensive testing to understand its properties and the products of its reaction in calcium carbonate systems before it can be used in conservation treatments. The current study builds on previous testing, to compare the effect of variations in the formulation of diethyl oxalate-based microgrouts bulked with limestone powder, including the effect of application to dry and damp limestone substrates to understand its reaction mechanism, products and performance.

Influence of Pinus pinaster age on aluminium fractions in acidic soils

The influence of plantation age on the chemical properties of acidic soils was studied in 16 plots in adult <em>Pinus pinaster</em> stands established in Galicia (NW Spain). The Al fractions in the soil solid phase and the total Al in soil solution were determined in the upper soil layer (0-20 cm) and the lower soil layer (20-40 cm) in each plot. The pH, total C and N, exchangeable Ca, Mg, Na, K, and Al and Al saturation (% Al) were determined in the solid fraction. Aluminium was extracted from the solid phase with the following solutions: ammonium oxalate (Al<sub>o</sub>), sodium pyrophosphate (Al<sub>p</sub>), copper chloride (Al<sub>cu</sub>) and ammonium chloride (Al<sub>NH4</sub>). The total Al in the liquid phase was also determined. All soil chemical parameters, except total N, C/N ratio and % Al, were significantly influenced by soil depth. The mean pH was lower in the upper than in the lower layer (4.57 vs. 4.97), but the opposite was observed for the organic C (77.2 vs. 50.4 g kg<sup>-1</sup>), the effective cation exchange capacity (eCEC) (9.43 vs. 6.25 cmol<sub>(+)</sub> kg<sup>-1</sup>), P (8.95 vs. 4.65 mg kg<sup>-1</sup>) and the exchangeable cations. Organic matter, total N and eCEC were significantly and positively correlated with plantation age (r = 0.69 in the upper layer and r = 0.82 in the lower layer, p < 0.01; r = 0.62, p < 0.05 in the upper layer and r = 0.78, p < 0.01 in the lower layer; r = 0.77, p < 0.01 in the upper layer and r = 0.85, p < 0.0001 in the lower layer, respectively), and pH<sub>KCl</sub> was negatively correlated with plantation age (r = -0.55 in the upper soil layer and r = -0.61 in the lower soil layer, p < 0.05). The concentrations of the different Al forms in all soils decreased in the order Al<sub>p </sub>> Al<sub>o </sub>> Al<sub>cu </sub>> Al<sub>NH4</sub>. Highly stable organo-aluminium complexes (Al<sub>p-cu</sub>) predominated over moderate and low stability complexes (Al<sub>cu</sub>) in all soil plots. The highly stable organo-Al complexes were significantly more abundant in the lower layer, whereas the opposite was observed for the exchangeable Al and the total Al in soil solution. The concentrations of all Al forms (except Al<sub>p-cu</sub>) were significantly and positively correlated with plantation age (Al<sub>o</sub> r = 0.50, p < 0.05 for the upper layer and r = 0.67, p < 0.01 for the lower layer; Al<sub>p</sub> r = 0.64, p < 0.01 for the lower layer; Al<sub>cu </sub>r = 0.84 for the upper layer and r = 0.83 for the lower layer, p < 0.0001; Al<sub>cu-NH4</sub> r = 0.65 for the upper layer and r = 0.78 for the lower layer, p < 0.01; Al<sub>NH4</sub> r = 0.76, p < 0.01 for the upper layer and r = 0.84, p < 0.0001 for the lower layer; total Al in soil solution r = 0.61 for the upper layer and r = 0.60 for the lower layer, p < 0.05). Stepwise linear regression analysis showed that plantation age, pH and total C explained between 67% and 93% of the variance in the Al forms. In all regression models, plantation age was a significant predictor variable for the different Al fractions, except total soluble Al, which is an important variable to consider in the study of chemical properties in forest soils.

Electroplating and Physicochemical Properties of Zinc–Nickel Alloy Coatings from Ammonium Oxalate Electrolytes

Electroplating of zinc−nickel alloy coatings (3–16 at % Ni) on Type 17G1S-U steel from ammonium oxalate baths is studied. The effects that the ratio of alloy components has on the coating’s corrosion resistance and structure and the electroplating kinetic parameters are revealed. Applying zinc–nickel alloy coatings leads to a nearly sevenfold decrease in the corrosion rate compared to zinc-only coatings. The microhardness of high-alloy nickel coatings increases by a factor of 1.8 compared to their low-alloy zinc–nickel counterparts.

Application of MoS2/reduced graphene oxide for photocatalytic degradation of rhodamine B in water environment

In this study, MoS2 was composited with RGO (the reduced form of graphene oxide) for enhancing the photocatalytic degradation of RhB in aqueous solution by applying visible light irradiation. A new approach to synthesize graphene was applied by reduction of graphene oxide using ascorbic acid. Factors affecting the photocatalytic degradation including pH, initial rhodamine B concentration, light source intensity and quencher existence were investigated. The results showed that MoS2/RGO composite exhibited better photocatalytic activity in the degradation of RhB (with a conversion of 80 %) compared to pure MoS2 (with a conversion of 30.8 %) under visible light irradiation. The higher photocatalytic performance of MoS2/RGO was found in slight acidic environment. Among the tested free radical killers, ammonium oxalate revealed the most significant effect on the photocatalytic degradation of RhB.This research also indicated that MoS2/RGO composite can be considered as a potential catalyst for the degradation of persistent organic dyes in wastewater.

The Use of a Sequential Extraction Technique to Characterize Soil Trace Evidence Recovered from a Spade in a Murder Case in Brazil.

Soil trace evidence can be useful in criminal investigations. A homicide which had occurred in South Brazil been concluded through the courts with a guilty conviction. A spade with soil traces adhering to it was seized from the confessed killer's house, it having been established that it had been used to bury parts of the victim's body. In the context of this confession, it provided an opportunity to test a protocol of analysis and verify the potential of discriminate soil sample analysis in such case works. This allowed us to test the practice of sequential analysis which had been developed for forensic case works in Brazil, with three sequential extractions: (i) 0.2mol/L pH 3.0 ammonium oxalate; (ii) dithionite-citrate-bicarbonate; and (iii) 0.5mol/L NaOH. It was possible to predict the sequence of events related to the homicide by using the sequential extraction technique and to conclude that: (i) the A horizon soil from the burial location of the torso was found to be very similar to the soil samples which had been recovered from the spade, which was able to be established despite there only being a small amount of soil adhering to the spade; (ii) the location where the legs were buried contributed a low amount of soil adhering to the spade. Therefore, it is suggested that, where possible, sequential extractions should be prioritized from a questioned sample to best provide information about the likely sequence of contact places and this test likely scenarios and criminal events.

Predicting the modifying effect of soils on arsenic phytotoxicity and phytoaccumulation using soil properties or soil extraction methods

Soils have the ability to modify contaminant bioavailability and toxicity. Prediction the modifying effect of soil on arsenic phytoaccumulation and phytoavailability using either soil property data or soil chemical extraction data in risk assessment of contaminated soil is highly desirable. In this study, plant bioassays important to ecological receptors, were conducted with 20 soils with a wide range in chemical and physical soil properties to determine the relationships between As measured by soil chemical extraction (soil pore water, Bray-1, sodium phosphate solution, hydroxylamine hydrochloride, and acid ammonium oxalate) or soil physico/chemical properties on arsenic phytotoxicity and phytoaccumulation. Soil pore water As and Bray-1 extracted As were significantly (P < 0.01) correlated with lettuce tissue As and those extractants and sodium phosphate were correlated with ryegrass tissue As. Hydroxylamine and acid ammonium oxalate extractions did not correlate with plant bioassay endpoints. Simple regression results showed that lettuce tissue relative dry matter growth (RDMG) was inversely related to tissue As concentration (r2 = 0.85, P < 0.01), with no significant relationship for ryegrass. Soil clay exhibited strong adsorption for As and significantly reduce tissue As for lettuce and ryegrass. In addition to clay content, reactive aluminum oxide (AlOx), reactive Fe oxide (FeOx) and eCEC was inversely related to ryegrass tissue As. Multiple regression equation was strongly predictive (r2 = 0.83) for ryegrass tissue As (log transformed) using soil AlOx, organic matter, pH, and eCEC as variables. Soil properties can greatly reduce contaminant phytoavailability, plant exposure and risk, which should be considered when assessing contaminant exposure and site-specific risk in As-contaminated soils.