Insights of competitive adsorption on activated carbon of binary caffeine and diclofenac solutions.

A commercial activated carbon (AC), obtained from peanut shells, was characterized and tested as adsorbent for the removal of the pharmaceutical products caffeine (CF) and diclofenac (DIC), which were used as model emerging contaminants. Nitrogen adsorption, XRD, SEM, FT-IR spectroscopy, and chemical analyses were typical of ACs, and Boehm titrations, calculations of surface sites distributions and zeta potential measurements indicated that reactions of deprotonable oxygenated groups at the AC surface lead to an isoelectric point of 3.2. A theoretical equation derived from the Langmuir isotherm is proposed to explain the adsorption percentage or adsorbed fraction (fads) as a function of the adsorbent dose (D, adsorbent "concentration"). Good fittings of the fads vs. D curves and the normal adsorption isotherms were obtained with the same Langmuir parameters. An important and practical application of this new equation is to permit a straightforward calculation of the solid dose needed to achieve a required adsorption percentage. With the aim of describing the adsorption processes of CF and DIC and their competition for surface sites under an ample range of concentrations, the adsorption of the emerging contaminants was investigated in single adsorbate experiments and with binary mixtures, and the competitive Langmuir model was applied. CF adsorption was high and independent of pH, whereas DIC adsorption was high between pH 4 and 6 and showed a continuous decrease from pH 6 to 10.5. The use of the competitive Langmuir isotherm for binary mixtures indicated that there was no pure competition between CF and DIC for surface sites. Instead, there was influenced competition, meaning that the presence of one substance at the surface modified the adsorption parameters of the other, either through lateral interaction forces or by changing the molecular orientation at the surface. In both cases, one substance favored the adsorption of the other, compared to pure competition.

Synthesis and in vitro testing of thermoresponsive polymer-grafted core-shell magnetic mesoporous silica nanoparticles for efficient controlled and targeted drug delivery.

In this work, thermoresponsive polymer grafted magnetic mesoporous silica nanoparticles were prepared, fully characterized and tested as controlled drug delivery systems. For this purpose, iron oxide nanoparticles coated with mesoporous silica shell were grafted with poly(N-isopropylacrylamide-co-3-(methacryloxypropyl)trimethoxysilane) (PNIPAM-co-MPS). The grafting and polymerization on the as-prepared nanoparticles were performed in one-step procedure. Using this methodology, the polymer was successfully grafted mainly onto the silica surface, leaving the mesopores empty for the drug loading. The prepared hybrid nanoparticles (MMSNP-PNIPAM-co-MPS) showed high magnetization saturation (19.5 emu g-1) and high specific surface area (505 m2 g-1) and pore volume (0.29 cm3 g-1). Ibuprofen was used as a model drug to test the performance of the hybrid particles as thermosensitive drug delivery systems. For this, in vitro drug delivery tests were conducted below (25 °C) and above (40 °C) the lower critical solution temperature (LCST) of the polymer (PNIPAM-co-MPS). Considerable difference (80%) in the ibuprofen release at these two temperatures and a fast and complete release of the drug at 40 °C was observed. These results suggest that the thermoresponsive copolymer acts as a gatekeeper for the temperature-controlled release of the drug loaded inside the mesopores. Therefore, MMSNP-PNIPAM-co-MPS are promising magnetic and thermoresponsive nanocarriers for targeted delivery of therapeutic substances.

An integrated approach for assessing the migration behavior of chlorpyrifos and carbaryl in the unsaturated soil zone.

Chlorpyrifos (O, O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate) and carbaryl (1-naphthyl methylcarbamate) are often applied concurrently as insecticides in food production. The aim of this study was to research their migration behavior in a real environment. We researched the leaching of both pesticides by setting up field lysimeters on a farm with the typical soil used in fruit production today. In order to analyze the variables involved in this process, we performed complementary adsorption studies, we performed complementary adsorption studies using batches and undisturbed soil laboratory columns for both compounds. The results for pesticide transport through the lysimeters showed that less than 1% of chlorpyrifos was recovered in the leachates, while almost 17% was recovered for carbaryl. Having completed the experiment in undisturbed laboratory columns, soil analysis showed that chlorpyrifos mainly remained in the first 5 cm, while carbaryl moved down to the lower sections. These results can be explained in view of the sorption coefficient values (KD) obtained in horizons A and B for chlorpyrifos (393 and 184 L kg-1) and carbaryl (3.1 and 4.2 L kg-1), respectively. By integrating the results obtained in the different approaches, we were able to characterize the percolation modes of these pesticides in the soil matrix, thus contributing to the sustainable use of resources.

From biowaste to magnet-responsive materials for water remediation from polycyclic aromatic hydrocarbons.

Composted urban biowaste-derived substances (BBS-GC) are used as carbon sources for the preparation of carbon-coated magnet-sensitive nanoparticles obtained via co-precipitation method and the subsequent thermal treatment at 550 °C under nitrogen atmosphere. A multitechnique approach has been applied to investigate the morphology, magnetic properties, phase composition, thermal stability of the obtained magnet-sensitive materials. In particular, pyrolysis-induced modifications affecting the BBS-GC/carbon shell were highlighted. The adsorption capacity of such bio-derivative magnetic materials for the removal of hydrophobic contaminants such as polycyclic aromatic hydrocarbons was evaluated in order to verify their potential application in wastewater remediation process. The promising results suggest their use as a new generation of magnet-responsive easily-recoverable adsorbents for water purification treatments.