Dependence Of Removal Rate Research Articles

Investigating natural attenuation of pharmaceuticals through unsaturated column tests

The growing consumption of pharmaceuticals together with their incomplete removal in wastewater treatment plants (WWTPs) implies the occurrence of these compounds in natural water resources. To investigate the natural attenuation of selected pharmaceuticals (caffeine, acetaminophen, sulfamethoxazole, naproxen and carbamazepine) during vadose zone infiltration, unsaturated column (L 26.67 cm, Ø 7.62 cm) experiments, filled with a sandy-loamy soil, were performed using two input concentrations (100 and 1000 μg L−1). The software Hydrus 1D was used to simulate experimental data. Caffeine and acetaminophen were never detected at the column outlet indicating a low environmental concern. On the other hand, attenuation of the detected pharmaceuticals could be reproduced by a combination of retardation and removal approaches. Carbamazepine is among the selected contaminants the most persistent. A dependence of removal rates on input concentrations was detected for sulfamethoxazole (μw from 2.78 d−1 to 1.16 d−1) and naproxen (μw from 1.16 d−1 to 0.63 d−1) attributed mainly to decreased metabolism of microorganisms when a higher input concentration is applied. Two transformation products (TPs) (N4-Acetylsulfamethoxazole and epoxycarbamazepine) derived from sulfamethoxazole and carbamazepine transformation, respectively, were detected during the experiment with the highest input concentration.

Effect of Pad Surface Roughness on SiO2 Removal Rate in Chemical Mechanical Polishing with Ceria Slurry

The effect of pad surface roughness on SiO2 removal rate was investigated using four different slurries containing ceria (CeO2) powders of different crystallite sizes and mean particle sizes. A clear maximum was observed in the dependence of removal rate on pad surface roughness. The four ceria slurries showed a peak in blanket wafer removal rate against pad surface roughness Ra. The peak moved toward larger Ra values with decreasing ceria crystallite size. The removal rate was strongly influenced not only by pad surface roughness but also by the crystallite size of ceria in the slurry.

Lattice Boltzmann Simulation on Molten Carbonate Fuel Cell Performance

Based on a model of a porous electrode, we make a detailed numerical simulation on molten carbonate fuel cell (MCFC) performance by using the lattice Boltzmann method (LBM). We apply Brinkman-Forchheimer-extended Darcy equations (generalized momentum equation) together with a reaction-diffusion equation with several reasonable assumptions and, to simulate more realistic physical conditions, we consider a curved boundary lying between the nodes of equal lattice space. As an attempt to assess the validity and efficiency of our model, two benchmark problems are investigated, including (i) the calculation of the dependence of generated current density on averaged gas velocity and the comparison between the result obtained by the LBM and by some other analytical solutions; (ii) the comparison between the result by the LBM calculation and the one by measuring experimentally the current density of test series in an overall range of concentration. An excellent agreement is found between the results from the LBM calculation and those from the experiment. In addition, the dependence of removal rate on current density, the contributions of concentration and concentration on cell performance, and the relations of cell voltage and power density with current density (load) are also studied.

Cu-CMP for dual damascene technology: Prestonian vs. non-prestonian regimes of Cu removal

Dual damascene Cu (Cu2D) is increasingly becoming the process of choice for IC technology. The Cu2D manufacturing sequence includes multiple use of CMP for both dielectric planarization and for shaping Cu interconnects, thereby making CMP an enabling operation. The performance of Cu-CMP has been observed to be slurry-dependent; while slurries typically exhibit the expected Prestonian behavior, i.e., a linear dependence of removal rate on pressure and speed, some slurries exhibit deviation from this linear behavior, especially at higher pressures. Such slurries are usually referred to as pressure-sensitive slurries. This paper analyzes a general scheme for Cu removal mechanism and explores the possible reasons behind the non-Prestonian anomaly.

Re‐examination of Pressure and Speed Dependences of Removal Rate during Chemical‐Mechanical Polishing Processes

A new removal rate model which is a modification to the Preston equation is developed to re‐account the dependence of removal rate on the down force (pressure) and rotation speed during the chemical‐mechanical polishing (CMP) process. The removal rate is first expressed as a linear function of both normal and shear stresses. The analogy of the CMP removal process to traveling indenters is considered and the stresses acting upon the abrasive particles (indenters) are formulated using previous models based on principles of elasticity and fluid mechanics. An expression is then derived which predicts the (pressure)5/6 and (speed)1/2 dependences of the removal rate. Experimental results with thermal oxides are consistent with the predictions.

Groundwater Cleanup byin-situSparging. IV. Removal of Dense Nonaqueous Phase Liquid by Sparging Pipes

Abstract Mathematical models for describing the removal of dense nonaqueous phase liquid (DNAPL) droplets dispersed in a contaminated aquifer by air sparging are described. The sparging configurations considered are 1) a single air pipe discharging at the bottom of the aquifer and 2) a single horizontal slotted pipe discharging at the bottom of the aquifer. Diffusion transport of VOC is assumed to take place from spherical DNAPL droplets through a thick stagnant water layer in a porous medium to the moving aqueous phase. The dependence of removal rates on model parameters is explored.