Sorption of Uranium (VI) From Aqueous Solution Using Nanomagnetite Particles; Singly and Coated With Humic Acid

Magnetite nanoparticles (Fe3O4) and humic acid coated magnetite nanoparticles (Fe3O4/HA) were investigated for the removal of U(VI) from aqueous solution. Batch sorption experiments were studied as a function contact time, adsorbent mass, U(VI) concentration and pH. The sorption kinetic data follow the pseudo-second order while the isotherms are found to obey Langmuir model with maximum capacity (Qmax) of 230, 196 mg/g for Fe3O4 and Fe3O4/HA, respectively. The study reveals that humic acid decreases the sorption capacity due to the formation of a polyanionic organic coating and thus altering the surface properties of the particles and reduces the magnetite aggregation and stabilizes the magnetite suspension.

An application research for near-surface repository of strontium-90 sorption kinetic model on mudrocks

In this study,90Sr was used as the test radionuclide to characterize the sorption kinetics and effects of initial 90Sr activity and remaining 90Sr in solid concentration were simulated for a near-surface repository. The study focused on the sorption characteristics of radionuclides in unsaturated groundwater environment (or vadose zone) is the important information for investigating the near-surface disposal of intermediate and low-level radioactive waste (ILLW). Moreover, the 90Sr sorption experiments reached equilibrium within 56 h, which fit to the first order sorption kinetic model, and the remaining 90Sr in mudrock samples showed obvious sorption equilibrium hysteresis, which fit to the second order sorption kinetic model. Before reaching the maximum sorption capacity, the sorption rate constant increases with 90Sr increasing; the distribution coefficient (Kd) of 56 h decreases with the remaining 90Sr decreasing. In addition, it showed that the slow sorption process dominated before the sorption reaches equilibrium. In fact, a reliable safety assessment methodology for on-going near-surface repository required a lot of the radionuclides parameters with local environment including the radionuclides sorption/desorption rate constant and maximum sorption capacity.

Role of surfactant-induced Marangoni stresses in drop-interface coalescence

We study the effect of surfactants on the dynamics of a drop-interface coalescence using full three-dimensional direct numerical simulations. We employ a hybrid interface-tracking/level-set method, which takes into account Marangoni stresses that arise from surface-tension gradients, interfacial and bulk diffusion and sorption kinetic effects. We validate our predictions against the experimental data of Blanchette and Bigioni (Nat. Phys., vol. 2, issue 4, 2006, pp. 254–257) and perform a parametric study that demonstrates the delicate interplay between the flow fields and those associated with the surfactant bulk and interfacial concentrations. The results of this work unravel the crucial role of the Marangoni stresses in the flow physics of coalescence, with particular attention paid to their influence on the neck reopening dynamics in terms of stagnation-point inhibition, and near-neck vorticity generation. We demonstrate that surfactant-laden cases feature a rigidifying effect on the interface compared with the surfactant-free case, a mechanism that underpins the observed surfactant-induced phenomena.

PHOSPHORUS SORPTION KINETIC ON ACID UPLAND SMECTITIC SOIL AMENDED WITH CALCIUM CARBONATE AND CALCIUM SILICATE

Acid upland smectitic soil is identified by high amount of exchangeable Al due to the weathering of aluminum (Al) octahedral layer by H+ saturation and by very low phosphorus (P) status. Calcium carbonate (CaCO3) and calcium silicate (CaSiO3) were commonly used to decrease exchangeable Al and increase soil pH. Laboratory experiments were conducted with clayey smectitic Typic Paleudults from Gajrug region, West Java. The CaCO3 and CaSiO3 were added at rates to replace 0, 1.5 or 3 times of exchangeable Al. After one month of incubation, P sorption kinetic experiments were conducted. The changes in some chemical properties after one month incubation showed that both CaCO3 and CaSiO3 increased the soil pH, exchangeable Ca, and base saturation but did not increase the cation exchange capacity. The results of the experiment showed that both CaCO3 and CaSiO3 decreased the rate constant value of first order kinetic equation (k) and the P sorbed maximum (a) at given amount of added P compared to Control.The CaCO3 was better than CaSiO3 in decreasing k values and on the contrary for a values. The decrease in P maximum sorption and the rate constant of the soil amended with CaSiO3 and CaCO3 due to occupation of P sorption sites by silicates and hydroxyl ions. The CaCO3with the rate to replace 1.5 x exchangeable Al was recommended to decrease the rate constant of P sorption. However, the CaSiO3 at the rate to replace 3 x exchangeable Al was recommended to decrease the maximum P sorption.

Sorption and Desorption of Remazol Yellow by a Fe-Zeolitic Tuff

The adsorption of remazol yellow from aqueous solution was evaluated using a Fe-zeolitic tuff. The adsorbent was characterized by scanning electron microscopy, IR spectroscopy and X-Ray diffraction. Sorption kinetic and isotherms were determined and the adsorption behavior was analyzed. Kinetic pseudo-second order and Langmuir-Freundlich models were successfully applied to the experimental results, indicating chemisorption on a heterogeneous material. The regeneration of the material was best accomplished by using a H2O2 solution. The sorption capacity of the Fe-zeolitic tuff increased when the saturated samples were treated with a H2O2 or FeCl3 solution.