Adsorption of heavy metals in mine wastewater by Mongolian natural zeolite

AbstractIn the first, Mongolian natural zeolites, whose base components were clinoptilolite, mordenite, and chabazite, were characterized in terms of element content, cation exchange capacity, and the like. Since the molar ratios of aluminum relative to silicon contained in Mongolian natural zeolites used in this study were lower than those of pure zeolites, the natural zeolite samples contained substantial amounts of impurities. The cation exchange capacity of the natural zeolite sample relatively increased with increasing aluminum content in the zeolite sample. Secondly, the batch equilibrium adsorptions of heavy metals, i.e., copper, zinc, and manganese, from model aqueous wastewater by Mongolian natural zeolites were carried. The natural zeolites could adsorb and remove the heavy metals in the aqueous solutions. The precipitation of metal hydroxide affected the results of adsorption in some cases. The saturated adsorbed amounts of the heavy metals estimated by Langmuir equation were almost same with one another, increased with solution pH and with cation exchange capacity of the natural zeolite

Effect of Modification of Mongolian Natural Zeolites on Adsorption of Chromium from Aqueous Solution

Removal of chromium (Cr (III) ) as well as hexavalent chromium (Cr (VI) ) from tannery wastewater at same time by adsorption using Mongolian natural zeolite was studied in terms of the characteristics, modification, and chromium adsorption performance of the zeolite. The cation exchange capacity of the zeolite ranged from 37×10−3 to 144×10−3 eq·g−1. From the results of phase identification and elemental analysis of the zeolite after modification run, the zeolite was not decomposed and was modified successfully. The zeolites modified by Ba2+, Cu2+, and HDTMA-Br could adsorb Cr (III) as well as the unmodified one could. The higher pH gave the higher adsorption ability, similarly to the adsorption of Cr (VI). Consequently, this adsorption method with Mongolian natural zeolite was proposed to remove Cr (III) together with Cr (VI) from tannery wastewater at same time.DOI: http://dx.doi.org/10.5564/pmas.v0i4.49Proceedings of the Mongolian Academy of Sciences 2009 No 4 pp.71-7

Numerical prediction of cavitation and pressure fluctuation around marine propeller

The applicability of numerical prediction method for cavitation around marine propeller was studied. A commercial CFD code was applied for computation of 10 different propellers. The computed cavitation patterns and pressure fluctuations were compared with model test. As the result, it s shown that this method can be used for the prediction of the behavior of sheet cavitation and the pressure fluctuation of the 1st order of blade frequency component.http://deepblue.lib.umich.edu/bitstream/2027.42/84315/1/CAV2009-final141.pd

Uptake Rate of Ammonia-nitrogen With Sterile Ulva sp. for Water Quality Control of Intensive ShrimpCulture Ponds in Developing Countries

Ammonia-nitrogen uptake by seaweed was modeled based on the concept of ammonia-nitrogen permeation through cell membrane, and the derived model of uptake rate was experimentally verified. In this study, sterile Ulva sp. was employed as seaweed to treat model culture solution, and the distribution equilibrium of the ammonia-nitrogen between the culture solution and cell inside was measured to obtain the equilibrium. For this measurement, the seaweed was pretreated before the uptake runs to inhibit the assimilation by methionine sulfoximine for removal of the assimilation effects on the uptake rate. The parameters of the distribution equilibrium and permeation rate of ammonia-nitrogen were measured. The pretreated seaweed could uptake ammonia-nitrogen and the ammonia-nitrogen permeated through the cell membrane from the culture solution into the cell according to the concentration gradient. The seaweed saturated with ammonia-nitrogen was immersed in the culture solution without ammonia-nitrogen and it could excrete ammonia-nitrogen once taken in. In both cases of the uptake and excretion, the systems attained equilibrium after around 6 hours. The ammonia-nitrogen concentration in the cell increased with the concentration in the culture solution at equilibrium. The flux of ammonia-nitrogen was almost proportional to the concentration difference, defined as that between the ammonia-nitrogen concentration in the cell and the hypothetical concentration of ammonia-nitrogen in the cell which is in equilibrium with the culture solution. The overall permeation coefficient was measured as 9.1 · 10–3 m h–1 for both cases of uptake and excretion, and this relationship was valid when the concentration difference was large enough relative to the flux

Effects of Sterile Ulva sp. Growth Rate on Water Quality Control of Intensive Shrimp Culture Pond in Developing Countries

To control the water quality in the intensive shrimp mariculture pond by uptaking the total ammonia-nitrogen with sterile Ulva sp., the growth rate of sterile Ulva sp. was experimentally measured and the influence of the rate on the water quality control evaluated. The specific growth rate constant of the seaweed increased with the total ammonia-nitrogen concentration, photosynthetic photon flux density and operating temperature. Then the dynamics of ammonia-nitrogen in the modeled culture pond for the intensive shrimp farming in the tropical region were numerically simulated, in which the seaweed was used to uptake ammonia-nitrogen. The seaweed could uptake ammonia-nitrogen effectively during daytime mainly due to the high intensity of sun light, and the total ammonia-nitrogen concentration in the shrimp pond could be kept very low. The required seaweed density to control the total ammonia-nitrogen concentration less than the recommended maximum concentration of 1.0 ⋅ 10–3 kg N m–3 was estimated to be reasonable

Phase transitions of an intrinsic curvature model on dynamically triangulated spherical surfaces with point boundaries

An intrinsic curvature model is investigated using the canonical Monte Carlo simulations on dynamically triangulated spherical surfaces of size upto N=4842 with two fixed-vertices separated by the distance 2L. We found a first-order transition at finite curvature coefficient \alpha, and moreover that the order of the transition remains unchanged even when L is enlarged such that the surfaces become sufficiently oblong. This is in sharp contrast to the known results of the same model on tethered surfaces, where the transition weakens to a second-order one as L is increased. The phase transition of the model in this paper separates the smooth phase from the crumpled phase. The surfaces become string-like between two point-boundaries in the crumpled phase. On the contrary, we can see a spherical lump on the oblong surfaces in the smooth phase. The string tension was calculated and was found to have a jump at the transition point. The value of \sigma is independent of L in the smooth phase, while it increases with increasing L in the crumpled phase. This behavior of \sigma is consistent with the observed scaling relation \sigma \sim (2L/N)^\nu, where \nu\simeq 0 in the smooth phase, and \nu=0.93\pm 0.14 in the crumpled phase. We should note that a possibility of a continuous transition is not completely eliminated.Comment: 15 pages with 10 figure

Isotropic photonic band gap and anisotropic structures in transmission spectra of two-dimensional 5-fold and 8-fold symmetric quasiperiodic photonic crystals

We measured and calculated transmission spectra of two-dimensional quasiperiodic photonic crystals (PCs) based on a 5-fold (Penrose) or 8-fold (octagonal) symmetric quasiperiodic pattern. The photonic crystal consisted of dielectric cylindrical rods in air placed normal to the basal plane on vertices of tiles composing the quasiperiodic pattern. An isotropic photonic band gap (PBG) appeared in the TM mode, where electric fields were parallel to the rods, even when the real part of a dielectric constant of the rod was as small as 2.4. An isotropic PBG-like dip was seen in tiny Penrose and octagonal PCs with only 6 and 9 rods, respectively. These results indicate that local multiple light scattering within the tiny PC plays an important role in the PBG formation. Besides the isotropic PBG, we found dips depending on the incident angle of the light. This is the first report of anisotropic structures clearly observed in transmission spectra of quasiperiodic PCs. Based on rod-number and rod-arrangement dependence, it is thought that the shapes and positions of the anisotropic dips are determined by global multiple light scattering covering the whole system. In contrast to the isotropic PBG due to local light scattering, we could not find any PBGs due to global light scattering even though we studied transmission spectra of a huge Penrose PC with 466 rods.Comment: One tex file for manuscript and 12 PNG files for figures consisting of Fig.1a-d, 2,3, ...