Removal of sulfonamide antibiotics from water: Evidence of adsorption into an organophilic zeolite Y by its structural modifications.

Sulfonamide antibiotics are persistent pollutants of aquatic bodies, known to induce high levels of bacterial resistance. We investigated the adsorption of sulfadiazine, sulfamethazine, and sulfachloropyridazine sulfonamides into a highly dealuminated faujasite zeolite (Y) with cage window sizes comparable to sulfonamide dimensions. At maximal solubility the antibiotics were almost completely (>90%) and quickly (t<1min) removed from the water by zeolite. The maximal amount of sulfonamides adsorbed was 18-26% DW of dry zeolite weight, as evidenced by thermogravimetric analyses and accounted for about one antibiotic molecule per zeolitic cage. The presence of this organic inside the cage was revealed by unit cell parameter variations and structural deformations obtained by X-ray structure analyses carried out using the Rietveld method on exhausted zeolite. The most evident deformation effects were the lowering of the Fd-3m real symmetry in the parent zeolite to Fd-3 and the remarkable deformations which occurred in the 12-membered ring cage window after sulfadiazine or sulfachloropyridazine adsorption. After sulfamethazine adsorption, zeolite deformation caused a lowering in symmetry up to the monoclinic P2/m space group. The effective and irreversible adsorption of sulfonamides into organophylic Y zeolite makes this cheap and environmentally friendly material a suitable candidate for removing sulfonamides from water.

Sulfonamide antibiotics embedded in high silica zeolite Y: a combined experimental and theoretical study of host-guest and guest-guest interactions.

A combined experimental and computational study of the interactions of three sulfonamides--sulfadiazine, sulfamethazine, and sulfachloropyridazine--embedded into the cages of high silica zeolite Y is here proposed. For all host-guest systems, the close vicinity of aromatic rings with zeolite framework was evidenced by multidimensional and multinuclear ((1)H, (13)C, (29)Si) SS-NMR measurements. Host-guest and guest-guest interactions were also elucidated by in situ FTIR spectroscopy and confirmed by ab initio computational modeling. Single molecules of sulfamethazine and sulfachloropyridazine were stabilized inside the zeolite cage by the vicinity of methyl and amino groups, respectively. Sulfadiazine is present in both monomeric and dimeric forms. Multiple weak H-bonds and van der Waals type interactions between organic molecules and zeolite are responsible for the irreversible extraction from water of all the examined sulfa drugs.

The influence of aluminium availability on phosphate uptake in Phaseolus vulgaris L. and Phaseolus lunatus L.

Aluminium toxicity is one of the major limiting factors of crop productivity on acid soils. High levels of available aluminium in soil may induce phosphorus deficiency in plants. This study investigates the influence of Aluminium (Al) on the phosphate (P(i)) uptake of two Phaseolus species, Phaseolus vulgaris L. var. Red Kidney and Phaseolus lunatus L. The two bean species were treated first with solutions of Al at different concentrations (0, 25, 50 and 100microM, pH 4.50) and second with solutions of P(i) (150microM) at pH 4.50. The higher the Al concentration the higher the Al concentration sorbed but P. vulgaris L var. Red Kidney adsorbed significantly more Al than P. lunatus L. Both species released organic acids: P. vulgaris L var. Red Kidney released fumaric acid and P. lunatus L. fumaric and oxalic acids which could have hindered further Al uptake. The two bean species showed a sigmoid P(i) uptake trend but with two different mechanisms. P. vulgaris L var. Red Kidney showed a starting point of 3h whereas P. lunatus L. adsorbed P(i) immediately within the first minutes. In addition, P. vulgaris L var. Red Kidney presented significantly higher P(i) uptake (higher uptake rate 'k' and higher maximum adsorption 'a' of the kinetic uptake model). The Al treatments did not significantly influence P(i) uptake. Results suggest that P. lunatus L. might adopt an external Al detoxification mechanism by the release of oxalic acid. P. vulgaris L var. Red Kidney on the other hand seemed to adopt an internal detoxification mechanism even if the Al sorbed is poorly translocated into the shoots. More detailed studies will be necessary to better define Al tolerance and/or resistance of Phaseolus spp.

Hydrolysis and adsorption of cyhalofop-butyl and cyhalofop-acid on soil colloids.

A study was undertaken to investigate the stability of cyhalofop-butyl (2 R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]butylpropanoate (CyB), an aryloxyphenoxy-propionic herbicide, at different pH values. The hydrolysis of CyB was faster in nonsterile than in sterile water. In sterile medium, CyB degraded only to (2 R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoic acid (CyA), whereas in nonsterile water, also the metabolites (2 R)-2-[4-(4-carbamoyl-2-fluorophenoxy)phenoxy]propanoic acid (CyAA) and (2 R)-2-[4-(4-carboxyl-2-fluorophenoxy)phenoxy]propanoic acid (CyD) were detected. The adsorption of CyB onto clays, iron oxide, and dissolved organic matter (DOM), using a batch equilibrium method, was also studied. A lipophilic bond is responsible for CyB adsorption on DOM. CyB was adsorbed on Fe(III)- and Ca-clays through hydrogen bonding between the carbonyl oxygen and water surrounding the exchangeable cations. In the interlayer of K-clay, CyB was hydrolyzed to CyA, which remained adsorbed therein as a monomer. The acid CyA was adsorbed only by the Fe-oxide through complexation. The CyA-Fe-oxide complex was stable and did not undergo degradation.

Effect of undesalted dissolved organic matter from composts on persistence, adsorption, and mobility of cyhalofop herbicide in soils.

The effect of undesalted dissolved organic matter (DOM) extracted from composts on the degradation, adsorption, and mobility of cyhalofop herbicide in soils was studied. A paddy-field sediment poor in organic matter (OM), an OM-rich forest soil, and DOM from agroindustrial or municipal waste compost were used. DOM increased the cyhalofop-acid but not the cyhalofop-butyl solubility in water. The degradation of cyhalofop-butyl in the sediment was slow, giving cyhalofop-acid as the only metabolite, whereas in forest soil, the process was faster, and three byproducts were detected. Soil pretreatment with DOM did not modify the degradation pattern but only reduced the adsorption of cyhalofop-butyl by soil, whereas it increased the adsorption of cyhalofop-acid. Among the cationic components of DOM solutions, the potassium ion seems to be related to the increased adsorption of the cyhalofop-acid in both OM-poor and OM-rich soils, yielding reversible complexes with the former and favoring hydrophobic interactions with the latter.