Adriano G. Fisch

Selective silica‐based sorbent materials synthesized by molecular imprinting for adsorption of pharmaceuticals in aqueous matrices

The presence of pharmaceuticals in aqueous environmental matrices often requires efficient and selective preconcentration procedures. Thus, silicas (SILs) were synthesized by a molecular imprinting technique using an acid-catalyzed sol-gel process and the following drugs as templates: fluoxetine, gentamicin, lidocaine, morphine, nifedipine, paracetamol, and tetracycline. The materials were subjected to sorbent extraction assisted by ultrasonic treatment to remove the drugs and the consequent formation of molecular imprinted cavities. The surface area of the resulting materials ranged from 290 to 960 m(2)/g. Adsorption tests were performed with the molecular imprinting phases. In terms of the potential selectivity, the SILs were subjected to the adsorption of drugs from samples such as potable and surface water. The adsorption capacity remained in the range between 55 and 65% for both matrices, while for the nonimprinted SIL it remained between 15 and 20%.

Peat, Rice Husk and Rice Husk Carbon as Low-Cost Adsorbents for Metals from Acidic Aqueous Solutions

We assessed the abilities of rice husk (RH), rice husk carbon (RHC), and peat to adsorb Cr, Fe, Mn, Ni, Zn, and Pb from aqueous solutions compared with commercial activated carbon (AC). The sorbent capacities were evaluated by percolation of aqueous solutions containing these six metals through adsorbent columns. Metal concentration was monitored by total reflection X-ray fluorescence (TXRF). Initial metal concentrations added to the columns were between 25 and 50 mg L−1, while those in the treated effluent ranged from 0.004 to 0.96 mg L−1. The adsorption capacities of the sorbents for these metals were examined by non-linear Langmuir and Freundlich models. The maximum adsorptive capacities expressed as individual metal (q m ) sums were 67.7, 86.9, 80, and 44.6 mg g−1 for AC, RHC, peat, and RH, respectively. The resulting isotherm parameters were used to compare the performance of the sorbents and to determine the ΔG values. After percolation through the adsorbent columns, the ecotoxicity of the eluates were determined with the probe Daphnia magna. Effluents from the rice husk sorbent column exhibited the lowest toxicity. Supplemental materials are available for this article. Go to the publishers online edition of Separation Science & Technology to view the supplemental file.

Catalisadores metalocênicos suportados para a produção de poliolefinas: revisão das estratégias de imobilização

The inadequacy of strategies used for the heterogeneization of metallocene catalysts is pointed out as one of the main causes of the lack of industrial employability of such polymerization catalysts. The main problems are the necessity of large quantity of MAO (cocatalyst) and the inability to control molecular mass distribution of the polymers. Based on this background, the main strategies for the heterogeneization of metallocenes are here reviewed. The advantages and disadvantages of each strategy are presented and discussed on theoretical and practical perspective. Considering the results reported on the different researches, outcomes of heterogeneization strategies are pointed out.

Alargamento da distribuição de massa molar de polímeros sintetizados com catalisadores metalocênicos dual-site

The main topics related to the use of dual-site catalysts in the production of polymers with broad molecular weight distribution are reviewed. The polymerization using dual-site catalysts is more economical and allows to produce a higher quality product than other processes, such as polymer blend and multistage reactors. However, the formulation of these catalysts is quite complicated since the same catalyst must produce distinct polymer grades. In addition, the release of patents concerning the combination of metallocenes and new technologies for polymerization shows that polymerization processes using dual-site catalysts are of current industrial interest.

Evaluation of lead desorption from cement matrices

Desorption of lead immobilized into cement and concrete matrices was evaluated in the pH range between 4 and 8 within a period of 2 h to 15 days. Lead-desorbed content in aqueous milieu was monitored by Graphite Furnace Atomic Absorption Spectroscopy, while matrices were directly analyzed by X-ray photoelectronic spectroscopy or Rutherford Backscattering spectrometry. For low pH, higher Pb desorption was observed, about 5–7 times higher than that measured in the case of concrete matrices. The inclusion of polyvinyl alcohol as a matrix modifier was evaluated through a factorial design. Polymer inclusion yielded a reduction in Pb desorption, but its effect cannot be justified in terms of the ability of this polymer to chelate the metal. The resulting modified matrices did not present toxicity to Daphnia magna.