ABSTRACT
PURPOSE: Pollution of surface water and groundwater by bulky molecules such as pesticides has been recognized as a major problem in many countries due to their persistence in aquatic environment and potential adverse health effects. The main purpose of this study is the development of a capable adsorbent to remove these bulky molecules from wastewater such as the pesticide Mesosulfuron-Methyl (MM) by reducing the diffusion path, to overcome the problems of diffusional limitations on microporous adsorbents. METHODS: The adsorption of mesosulfuron-methyl (MM) from aqueous solution is curried out using treated acid HY zeolite. Batch sorption equilibrium and kinetic experiments are conducted to evaluate the efficiency of these materials. Parent zeolites and their derivatives have been characterized by nitrogen adsorption-desorption, pyridine chemisorption followed by infrared spectroscopy and X-ray fluorescence. RESULTS: The acid treatment leads to an increase in the specific surface from 691 to 853 m2 g- 1 for HY(30) and from 631 to 806 m2 g- 1 for the HY(16.6) zeolites. It also leads to a reduction in Lewis acidity from 74 to 25 µmol g- 1 and from 135 to 31 µmol g- 1 for HY(30) and HY(16.6) zeolites respectively, and increases the adsorbent-adsorbate interaction. The adsorption capacity increased from 83 to 99 % after acid treatment. The equilibrium adsorption time is decreased from 15 h to 10 min for the HY(30)_A and from 20 h to 20 min for the HY(16.6)_A for an initial concentration of 20 mg L- 1. The adsorption capacity depends on the pH solution, and the neutral form of the MM is more easily adsorbed into zeolite than the dissociated form via the framework bridged oxygen atoms. For all the samples, the pseudo-second-order kinetic model fits very well with the experimental data. In the case of the modified zeolites, the approaching equilibrium factor R w decreases from 0.08183 to 0.00008 when the Lewis acid sites decrease; indicating that the equilibrium is reached more quickly. S-shape adsorption isotherms indicates that cooperative adsorption phenomena. Nevertheless, the shape of acid treated zeolites evolves to an L type indicating a significant enhancement of the adsorbent - adsorbate interactions inducing better adsorption efficiency. CONCLUSIONS: Mesosulfuron-methyl adsorption has been successfully enhanced after acid treatments of zeolites HY.
ABSTRACT
The lipophilic composition of Allium triquetrum L. bulbs, flowers and leaves was studied for the first time by GC-MS. Sixty compounds were firstly identified in A. triquetrum L. Fatty acids represented the major lipophilic family among the studied extracts, with (9Z,12Z,15Z)-octadeca-9,12,15-trienoic and (9Z,12Z)-octadeca-9,12-dienoic acids being the major constituents of this family. A long chain aliphatic ketone, namely hentriacontan-16-one, was mainly found in flowers and leaves. Flowers and leaves were also found to be rich in long chain aliphatic alkanes and alcohols, respectively. Sterols, monoglycerides, aromatic compounds and long chain aliphatic aldehydes were found in lower amounts. The antibacterial activity of A. triquetrum bulb, flower and leaf extracts against methicillin-resistant Staphylococcus aureus (MRSA) growth was in vitro assessed. Bulb and flower extracts showed significant MRSA growth inhibition. Overall, these valuable findings can contribute to the valorization of A. triquetrum L. as a source of value-added phytochemicals, specifically as antibacterial agents and for nutraceutical applications.
