جستجوی مقالات مرتبط با کلیدواژه « Langmuir isotherm » در نشریات گروه « محیط زیست »

Growth in population has caused a corresponding increase in agricultural production which consequently led to an increase in agricultural wastes or byproducts. This is sometimes difficult to manage and may pose a menace to the society if not properly disposed. Hence, this research investigated the efficacy of utilizing agricultural byproduct (melon husk) in removing Pb2+ and Cd2+ from wastewaters so as to prevent their deleterious impact on ecosystem and public health. This was achieved by treating tannery effluents with melon husks modified with H3PO4, NaOH and CH4N2O. Results showed that, the Freundlich and Langmuir adsorption capacities on the modified melon husks ranged from 0.1403 – 1.551 mg/g and 0.1499 – 0.6013 mg/g, respectively. Also, the R2 values for Pseudo 1st and 2nd order rate constants ranged from 0.0272 – 0.2391 and 0.9112 – 0.9958, respectively. Hence, it was concluded that the modified melon husks followed Freundlich isotherm model as well as Pseudo-2nd order kinetics and could be effectively used to remove Pb2+ and Cd2+ from wastewater.

Contamination of water resources by pesticide toxins is considered as one of environmental issues which is because of plant pest diversity and subsequently use of various toxicants. In previous decades all over the world, the usage of organophosphorus toxins in order to preservation of agriculture products expanded. In Gilan province (Iran) there are numerous agriculture lands and gardens which are sprayed intermittently and since drinking water of the region residents is rather supplied by underground waters, then penetration of toxicants into the wells is possible. For this reason pesticide toxicants use could be a treat for drinking water supplying resources of this state. In the paper, samples of water from ten wells were collected and for measuring the quantities of toxicants, experiments were carried out during 4 seasons of year. Toxicant residues in samples were analyzed according to Gas Chromatography–Electron Capture Detector (GC-ECD) method. Due to phosphorous toxicant analyze results; it is revealed that in some cases precipitation amount has a great effect on toxicant concentration inside well water because of leaching higher layers. Also it is indicated that clay presence in soil due to toxicant holding and rain or flood occurrence cause to decrease and increase toxicant leak into the underground water respectively. Finally in order to Hinosan toxicant removal from water resources, active carbon has been utilized. The results indicated that adsorption by active carbon was of Langmuir type and this adsorbent effective cause to eliminate Hinosan toxin from water resources.

The present study was carried out to investigate three different adsorbents; dry cells of the bacterium Exiguobacterium sp. 27, polyaniline and a mixture of both in different ratios for removal of Ni(II) from aqueous solution. The results showed that the adsorption of Ni(II) using dry cells of Exiguobacterium sp. 27 was very fast and the equilibrium time was 15 min, while the equilibrium time for polyaniline was 120 min. Finally, for a mixture of dry cells of Exiguobacterium sp. 27 and polyaniline, the equilibrium time was 40 min. Adsorption isotherm and kinetics were studied. The reaction of Exiguobacterium sp. 27 when exposed to Ni(II) solution was found to be pseudo-second order reaction and the reaction obeyed the Langmuir equation. Whereas, the reaction of polyaniline with Ni(II) solution was pseudo-second order reaction and the reaction obeyed Freundlich equation. The experimental studies showed that mixture of Exiguobacterium sp. 27 and PANI had better metal uptake than both Exiguobacterium sp. 27 and PANI individually. This work provided an evidence for the possible application of nanoparticles of bacterial cells and/or polyaniline for Ni(II) biosorption from solution for a safe and clean environment.

An organophilic clay-based adsorbent was prepared by incorporating a cationic surfactant,hexadecyltrimethylammonium (HDTMA) at different levels of CEC in Tunisian smectite-illite clay. The presence of the HDTMA surfactant enhanced the adsorption ability of the clays toward plyphenolic compounds from aqueous systems. Adsorption experiments were carried out using a batch equilibration technique to investigate the removal of tannin by the surfactant modified clay. Adsorbent characterizations were investigated using X-ray diffraction, infrared spectroscopy, surface area analysis, and potentiometric titration. The effects of pH, contact time and initial solute concentration on the adsorption of tannin onto modified clay were investigated. The adsorption process was much dependent on the pH and was found to follow pseudosecond- order kinetics. The optimum pH value was at pH ranging from 4.5 to 6. The maximum removal efficiency of tannin from aqueous solution was 91%. The adsorption isotherms were measured and correlated to Langmuir isotherms. From the results it can be concluded that the surfactant-modified clay could be a good adsorbent for treating tannin-contaminated waters.