Porosity on External Surface of H-Clinoptilolite Sorption of CCI4 and n-C6H14

CCl4 （carbon tetrachloride） and n-C6H14 （n-hexane） sorption studies have been carried out on natural and dealuminated clinoptilolite-type zeolites. External surface area of the materials has been assessed using the αs-plots method. The high resolution αs-plots show that the isotherms are divided into four parts corresponding to adsorption in ultramicropores, intersections, supermicropores and external surface area, respectively. The mineralogies of natural zeolites are determined by X-ray analysis. N： low-pressure hysteresis loops, displayed by some substrata, are related to the micropore structure and to the ion-exchange treatment at which the natural precursors were subjected. The adsorption behavior of these substrata was examined in the range of relative pressures between 10^-5-1. Natural samples were used as reference materials to carry out the sorption analyses of the dealuminated samples. The effect of narrow micropore constrictions on the adsorption behavior of clinoptilolites was explored. The occurrence of a low-pressure hysteresis loop on the sorption isotherm of a modified sample is associated to the strong adsorption of the adsorbate molecules at the entrance of the necked-shape micropores, which interfere with the diffusion of the adsorbate molecules inside the porous structure.

Experiment and Modeling of Low Coverage Uptake of N2 and 02 on H-Clinoptilolite Zeolite from Tehuacan, Puebla, Mexico

Adsorption isotherms of N2 and 02 on dealuminated clinoptilolite zeolites were measured by the inverse gas chromatography method at zero-coverage. This type of microporous solids such as natural （CLINA） and dealuminated clinoptilolite zeolites （CLIDA1-CLIDA5） were conditioned by means of acid treatment of the natural zeolitic precursor （CLINA） with HCI at different concentration. Adsorption of selected gases （N2 and 02） on clinoptilolite zeolites were studied in the temperature range from 398 K to 498 K. The Langmuir adsorption model was found to approximately fit the gases adsorption data, within the selected temperature range. The uptake amount of these gases by the diverse adsorbents was temperature dependent. Additionally, the energies of interaction between of these gases with clinoptilolite microporous walls were realized from the evaluation of the isosteric heats of adsorption （qst）. These isosteric heats were found to obey in the following decreasing order： qst （N2）： CLIDA1 〉 CLIDA3 〉 CLIDA2 〉 CLIDA4 〉 CLIDA5 〉 CLINA; while qst （02）： CLIDA3 〉 CLIDA2 〉 CL1DA1 〉 CLIDA5 〉 CLIDA4 〉 CLINA.

Influence of Inorganic Salts during the Photooxidative Process of Nitrobenzene

Into the photooxidation process, several factors such as pH, time of irradiation, dose of UV light, lamp power, contaminant concentration, turbidity of the solution and the presence of salts can interfere with the photodegradation of pollutants. This research aims to evaluate the influence of salts： NaCl, MgCl2, CaCI2, BaC12, CuCl2, Na2SO4, MgSO4, MnSO4, FeSO4, CuSO4, Na3PO4, K2CrO4 and K2Cr207 in concentrations of 0.0005 M, 0.005 M and 0.05 M during photodegradation of aqueous solution of 59.5 mg/L of nitrobenzene at a pH of 2.5. It was observed that the presence of salts such as CuCI2, CuSO4, FeSO4, K2CrO4 and K2Cr207 interfere negatively in the system UV/H202 applied for degradation of nitrobenzene; possibly by oxidation of Fe2＋ to Fe3＋ and Cu＋ to Cu2＋ in the Cr case, due to the difficulty of transforming the Cr6＋ to Cr3＋ or because these solutions have color and act as radiation absorbing filter.