Adsorption of propisochlor on soils and soil components equation for multi-step isotherms

Zirconium-Based Metal-Organic Framework Mixed-Matrix Membranes as Analytical Devices for the Trace Analysis of Complex Cosmetic Samples in the Assessment of Their Personal Care Product Content

A device comprising a zirconium-based metal-organic framework (MOF) mixed-matrix membrane (MMM) framed in a plastic holder has been used to monitor the content of personal care products (PCPs) in cosmetic samples. Seven different devices containing the porous frameworks UiO-66, UiO-66-COOH, UiO-67, DUT-52, DUT-67, MOF-801, and MOF-808 in polyvinylidene fluoride (PVDF) membranes were studied. Optimized membranes reach high adsorption capacities of PCPs, up to 12.5 mg·g^-1 benzophenone in a 3.0 mg·L^-1 sample. The MMM adsorption kinetics, uptake measurements, and isotherm studies were carried out with aqueous standard solutions of PCPs to ensure complete characterization of the performance. The studies demonstrate the high applicability and selectivity of the composites prepared, highlighting the performance of PVDF/DUT-52 MMM that poses uptakes up to 78% for those PCPs with higher affinity while observing detection limits for the entire method down to 0.03 μg·L^-1. The PVDF/DUT-52 device allowed the detection of parabens and benzophenones in the samples, with PCPs found at concentrations of 1.9-24 mg·L^-1.

Highly efficient porous carbons for the removal of W(VI) oxyanion from wastewaters

Pyrolysis chars derived from rice wastes were chemically activated and used in W(VI) oxyanion adsorption assays in synthetic and mining wastewaters. For comparison purposes, a commercial activated carbon (CAC) was also used. Different experimental conditions were tested in the adsorption assays: solid/liquid ratio (S/L), initial pH, contact time, and initial W concentration. The porous carbon P2C+KOH presented the overall best performance in both media, due to its high surface area (2610 m² g^-1), mesopore volume (1.14 cm³ g^-1), and neutral pH_pzc (6.92). In the synthetic wastewater, the highest uptake capacity of P2C+KOH (854 mg g^-1) was found in the assays with an S/L 0.1 g L^-1, an initial pH 2, and an initial W concentration of 150 mg L^-1, for 24 h. This value was almost 8 times higher than the one obtained for CAC (113 mg g^-1). In the mining wastewater, P2C+KOH showed an even higher uptake capacity (1561 mg g^-1) in the assay with the same experimental conditions, which was almost 3 times higher than for CAC (561 mg g^-1). These results suggest that P2C+KOH seems to be an efficient alternative to CAC in the W(VI) adsorption from liquid effluents.

BSMV as a Biotemplate for Palladium Nanomaterial Synthesis

The vast unexplored virus biodiversity makes the application of virus templates to nanomaterial synthesis especially promising. Here, a new biotemplate, Barley stripe mosaic virus (BSMV) was successfully used to synthesize organic-metal nanorods of similarly high quality to those produced with Tobacco mosaic virus (TMV). The mineralization behavior was characterized in terms of the reduction and adsorption of precursor and nanocrystal formation processes. The BSMV surface-mediated reduction of Pd⁽²⁺⁾ proceeded via first-order kinetics in both Pd⁽²⁺⁾ and BSMV. The adsorption equilibrium relationship of PdCl₃H₂O^- on the BSMV surface was described by a multistep Langmuir isotherm suggesting alternative adsorbate-adsorbent interactions when compared to those on TMV. It was deduced that the first local isotherm is governed by electrostatically driven adsorption, which is then followed by sorption driven by covalent affinity of metal precursor molecules for amino acid residues. Furthermore, the total adsorption capacity of palladium species on BSMV is more than double of that on TMV. Finally, study of the BSMV-Pd particles by combining USAXS and SAXS enabled the characterization of all length scales in the synthesized nanomaterials. Results confirm the presence of core-shell cylindrical particles with 1-2 nm grains. The nanorods were uniform and monodisperse, with controllable diameters and therefore, of similar quality to those synthesized with TMV. Overall, BSMV has been confirmed as a viable alternate biotemplate with unique biomineralization behavior. With these results, the biotemplate toolbox has been expanded for the synthesis of new materials and comparative study of biomineralization processes.

Study of sorption of two sulfonylurea type of herbicides and their additives on soils and soil components

The sorption of two sulfonylurea type herbicides (chlorsulfuron: (1-(2-chlorophenylsulfonyl)-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea; tribenuron methyl: (methyl-2-[N-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)-3-(methyl-ureido)-sulfonyl]-benzoate) was studied on sand and chernozem soil adsorbents. Experimental results for solutions prepared from the pure ingredients were compared to those prepared from the appropriate formulated commercial products. At small concentrations, the extent of adsorption of the active ingredient was higher than from the formulation containing solutions. Environmental fate and effects of the forming agents are less investigated because they rarely have concentration limits recommended by authorities. In addition to the adsorption of active ingredients, therefore, the sorption behavior of a widely used additive Supragil WP (sodium diisopropyl naphthalene sulphonate) was also studied. This dispersant is an anionic forming agent applied in a lot of pesticide formulations. Using three different soils (sand, brown forest, chernozem) as adsorbents two-step isotherms were obtained. The role of the soil organic matter (OM) was significant in the adsorption mechanism because the adsorbed amounts of the dispersant correlated with the specific surface area as well as with the total organic carbon (TOC) content of the soils. The sorption behavior indicates the operation of hydrophobic interaction mechanism between the soil OM and the dispersant. These results are supported by our further sorption experiments on clays, too. Zeta potential measurements seem to be promising for the interpretation of multi-step isotherms. The application of this technique proved that higher concentrations of the anionic forming agent assisted the peptization of soil organic matter (SOM) resulting in stable colloidal solution dominated by negative charges. Since the pesticides investigated are also anionic at the studied pH (7 and 8.3) the dissolved organics lead to the enhancement of the mobility of both the sulfonylureas and dispersant.

The effect of alginite on the decomposition of the herbicide propisochlor

The catalytic effect of an oil shale rock "alginite" was studied under laboratory conditions on the decomposition of herbicide propisochlor. The breakdown process was followed in four parallel experiments: buffered solution (pH = 7), in buffer solutions containing alginite or bentonite (a common rock) and also in the solution obtained from the extraction of the alginite (alginite/buffer = 1/10). In the aqueous phase, the decomposition of the herbicide was followed by using HPLC-UV and the metabolites of degradation were identified by GC-MS techniques. For the phenomenological description of the experimental decay curves two parallel reactions with first-order kinetics were taken into account. During the time of experiments, no significant decomposition was observed either in the pure buffer solution or in the presence of bentonite. When, however, alginite was added to the system the degradation of propisochlor was accelerated dramatically: after 5 days, its concentration dropped below 50 % of the initial value. The identified degradation products indicate both reductive as well as oxidative biological mechanisms operating under anoxic conditions. It was proved earlier that the sulfenic and sulfinic acid ester derivatives of the propisochlor appeared in the metabolic pathways of animals and plants but they were not detected yet in the degradation process occurring in the soil environment. Among the degradation products a dehydrochlorinated derivative is a new metabolite identified in our experiments. Our results corroborate the algae-related origin of the alginite rock and forecast its application as a soil ameliorating agent.

Mathematical evaluation of activated carbon adsorption for surfactant recovery in a soil washing process

The performances of various soil washing processes, including surfactant recovery by selective adsorption, were evaluated using a mathematical model for partitioning a target compound and surfactant in water/sorbent system. Phenanthrene was selected as a representative hazardous organic compound and Triton X-100 as a surfactant. Two activated carbons that differed in size (Darco 20-40 mesh and >100 mesh sizes) were used in adsorption experiments. The adsorption isotherms of the chemicals were used in model simulations for various washing scenarios. The optimal process conditions were suggested to minimize the dosage of activated carbon and surfactant and the number of washings. We estimated that the requirement of surfactant could be reduced to 33% of surfactant requirements (from 265 to 86.6g) with a reuse step using 9.1g activated carbon (>100 mesh) to achieve 90% removal of phenanthrene (initially 100mg kg-soil(-1)) with a water/soil ratio of 10.

Competitive sorption behavior of copper(II) and herbicide propisochlor on humic acids

The competitive sorption behavior of Cu2+ and propisochlor on humic acids (HA) was investigated using a batch method. The sorption equilibrium time of propisochlor on HA was 12 h when its initial concentration was 4 or 10 mg L(-1). The results showed that the Langmuir model can best describe the sorption behavior of propisochlor on HA. The added Cu2+ reduced the solid-phase concentration of propisochlor on HA, and the Langmuir model can also describe the sorption behavior of propisochlor on HA when the Cu2+ concentration is 100 and 200 mg L(-1). The sorption of propisochlor on HA did not remarkably affect the sorption of Cu2+ on HA when the concentration of propisochlor was below 20 mg L(-1). Cu2+ may compete with propisochlor for the sorption sites of HA, such as carboxylic and phenolic groups. It can be concluded that Cu2+ fast adsorbed to the HA matrix, altered its physical and chemical properties, and thus decreased the solid-phase concentrations of propisochlor on HA. In natural water, Cu2+ may promote the release of propisochlor from HA, and thus affect its transport, transformation, and fate in the environment.

Effect of pH and the role of organic matter in the adsorption of isoproturon on soils

Equilibrium measurements were carried out with the herbicide isoproturon on natural adsorbents (brown forest-, chernozem-, sandy soils and quartz) in different buffered media (pH 5, 7, 8 phosphate buffer). Adsorption isotherms were fitted by a multi-step adsorption equation providing numerical information used in the environmental propagation models and risk assessment works. In the adsorption of the slightly polar isoproturon the dissolved organic matter of the soil and the pH play an important role. At molecular level, results are interpreted by taking into consideration the hydrophobic interaction and the formation of hydrogen bonds between the surface and the solute. The observed adsorption behavior indicates that the organic matter content of the soils and its soluble fulvic acid, alkaline soluble humic acid and insoluble humin fractions were considerable different. The chernozem soil containing the highest amount of insoluble organic fraction proved to be a very efficient adsorbent. The brown forest and the sandy soils exhibit rather similar adsorbent properties but at pH 7 the latter containing more fulvic acid adsorbs less isoproturon due to the enhanced solubility of the soil organic matter. In alkaline conditions the negatively charged solute and the surface repel each other and the hydrophobic interactions are also weaker than in neutral media.