ADSORPTION,KINETICS, AND EQUILIBRIUM STUDIES ON REMOVAL OF 4,4-DDT FROM AQUEOUS SOLUTIONS USING LOW-COST ADSORBENTS

The removal of a chlorinated pesticide (4,4-DDT) from aqueous solutions by a batch adsorption technique using different low-cost adsorbents was investigated. Two adsorbents, wood sawdust (A) and cork wastes (B), were used to determine adsorption efficiency. The influence of the adsorbent particle size and the organic matter of water (humic acids) on the removal process was studied. The obtained results were compared to those obtained with a commercial powdered activated carbon (PAC, F400, Chemviron) (C). Kinetic studies were performed to understand the mechanistic steps of the adsorption process. The rate of the adsorption kinetics of 4,4-DDT on the low-cost adsorbents was found best fitted with a pseudo-second-order kinetic model. This is in contrast to the rate of the adsorption kinetics of the PAC F400, which was best fitted with the Lagergren model. The application of the Morris-Weber equation showed that the adsorption process of 4,4-DDT on these adsorbents was complex. Both the adsorption on the surface and the intraparticle diffusion were the rate-controlling mechanisms. Langmuir and Freundlich adsorption isotherms were applicable to the adsorption process and their constants were evaluated. The adsorption capacity (q_m) calculated from the Langmuir isotherm (69.44 mg·g^?1, 19.08 mg·g^?1, and 163.90 mg·g^?1, respectively, for A, B, and C) showed that the process is highly particle size dependent, that the organic matter influenced the adsorption process negatively, and that wood sawdust is the most effective adsorbent for the removal of 4,4-DDT from aqueous solutions. The adsorbents studied exhibited a possible application in water decontamination, as well as in treatment of industrial and agricultural waste waters.     

Olive mill wastewater degradation by Fenton oxidation with zero-valent iron and hydrogen peroxide

The degradation of olive mill wastewater (OMW) with hydroxyl radicals generated from zero-valent iron and hydrogen peroxide has been investigated by means of chemical oxygen demand (COD) and phenolic compounds analyses. The effects of the H2O2 dose, the pH and the organic matter concentration have been studied. The optimal experimental conditions were found to have continuous presence of iron metal, acid pH (2.0-4.0), and relatively concentrated hydrogen peroxide (9.5M). Coloration of OMW disappeared and phenolic compound decreased to 50% of initial concentration after 3h reaction time. The application of zero-valent Fe/H2O2 procedure permitted high removal efficiencies of pollutants from olive mill wastewater. The results show that zero-valent Fe/H2O2 could be considered as an effective alternative solution for the treatment of OMW or may be combined with a classical biological process to achieve high quality of effluent water.     

Determination of chlorinated pesticides in water by SPME/GC

Solid-phase microextraction (SPME) followed by gas chromatography (GC) coupled with an electron capture detector has been applied for the analysis of chlorinated pesticides in water. Molecule adsorption on 100 microm polydimethylsiloxane (PDMS) fibers was activated by immersion of the whole fiber-sample system in an ultrasonic bath. The good reproducibility, low detection limits and wide linear ranges obtained encourage the use of this technique in water control.     

Nanoparticles of alkylglyceryl dextran and poly(ethyl cyanoacrylate) for applications in drug delivery: Preparation and characterization

Toward the development of drug carriers that are capable of crossing biological membranes, controlled emulsion polymerization has been utilized to produce nanoparticulate carriers from the combination of poly(alkyl cyanoacrylate) and alkylglyceryl dextran to a molecular structure designed to combine the nonimmunogenic and stabilizing properties of dextran with the demonstrated permeation enhancing ability of alkylglycerols. To this aim, a systematic series of alkylglyceryl dextrans have been synthesized and functionalized with ethyl or butyl cyanoacrylates to form stable polymeric nanocarriers (100–500?nm). Results of investigations into their capability to act as controlled-release devices and their cytotoxicity against bEnd3 cells are reported.