Characterization and performance of nanofiltration membranes

The availability of clean water has become a critical problems facing the society due to pollution by human activities. Most regions in the world have high demands for clean water. Supplies for freshwater are under pressure. Water reuse is a potential solution for clean water scarcity. A pressure-driven membrane process such as nanofiltration has become the main component of advanced water reuse and desalination systems. High rejection and water permeability of solutes are the major characteristics that make nanofiltration membranes economically feasible for water purification. Recent advances include the prediction of membrane performances under different operating conditions. Here, we review the characterization of nanofiltration membranes by methods such as scanning electron microscopy, thermal gravimetric analysis, attenuated total reflection Fourier transform infrared spectroscopy, and atomic force microscopy. Advances show that the solute rejection and permeation performance of nanofiltration membranes are controlled by the composition of the casting solution of the active layer, cross-linking agent concentration, preparation method, and operating conditions. The solute rejection depends strongly on the solute type, which includes charge valency, diffusion coefficient, and hydration energy. We also review the analysis of the surface roughness, the nodule size, and the pore size of nanofiltration membranes. We also present a new concept for membrane characterization by quantitative analysis of phase images to elucidate the macro-molecular packing at the membrane surface

Simulation and control of nanoparticle size distribution in a high temperature reactor

This work focuses on the modeling, simulation and control of particle size distribution (PSD) during nanoparticle growth with the simultaneous chemical reaction, nucleation, condensation, coagulation and convective transport in a high temperature reactor. Firstly, a model known as population balance model was derived. This model describes the formation of particles via nucleation and growth. Mass and energy balances in the reactor were presented in order to study the effect of particle size distribution for each reaction mechanisms on the reactor dynamics, as well as the evolution of the concentrations of species and temperature of the continuous phase. The models were simulated to see whether the reduced population balance can be used to control the particle size distribution in the high temperature reactor. The simulation results from the above model demonstrated that the reduced population balance can be effectively used to control the PSD. The proposed method “which is the application of reduced population balance model” shows that there is some dependence of the average particle diameter on the wall temperature and the model can thus be used as a basis to synthesize a feedback controller where the manipulated variable is the wall temperature of the reactor and the control variable is the average particle diameter at the outlet of the reactor. The infl uence of disturbances on the average particle diameter was investigated and controlled to its new desired set point which is 1400nm using the proportional-integral-derivative controllers (PID controllers). The proposed model was used to control nanoparticle size distribution at the outlet of the reactor

Porous and fractal analysis on the permeability of nanofiltration membranes for the removal of metal ions

Porous and fractal analysis on the permeability of nanofiltration membranes was investigated for the removal of metal ions. The permeability of a porous membranes used in wastewater treatment is strongly depended on its local geometry and connectivity, the size distribution of the pores available for flow. Fouling studies with two different membranes at three different pHs were carried out with manganese and magnesium. It was shown that the tighter membrane was less rougher and less fouled compared with the rougher membrane. NF90-2450 showed the highest degree of fouling. The X-ray diffraction showed that NF90-2540 consist of a pronounced diamond at the angle of 45 �C which was responsible for porosity. The threshold images were obtained from the scanning electron microscopy images with the use of Image J software confirmed that NF90-2540 has higher percentage porosity when compared with the percentage porosity of NF1540-3. An evaluation of the relationships between porosity and permeability for the fractal analysis by a box counting was done. The evaluation also confirmed that the lower fractal dimension corresponds to a lower value of porosity. The higher the pH, the lower the fractal dimension of the used membranes due to the blockage of pores. A higher value of fractal dimension of the used membrane at a lower pH corresponds to a lower rejection of the metal ions

The properties and the effect of operating parameters on nickel plating (review)

The energy required in an electroplating process and the material costs are important considerations in product manufacturing. The most important plating criteria, however, are quality and the uniformity of the deposited metals. The nickel plating process is used extensively for decorative, engineering, and electroforming purposes. Because of the appearance and other properties of the electrodeposited material, nickel deposition can be varied, over a wide range, by controlling the composition and the operating parameters of the plating solution. Decorative applications account for about 80% of the nickel consumed in plating; 20% is consumed for engineering and electroforming purposes. Autocatalytic (electroless) nickel plating processes are commercially important but are outside the scope of this review. In this review, the basic facts of nickel electroplating processes, thickness test and methods, are discussed. The properties of nickel and the different effects of the operating parameters on nickel plating, together with the simulation and design tools, are also reviewed. Simulation tools can help to obtain better plating results. Non-destructive techniques to evaluate the coatings on a microstructural and the technical evaluation with TEM, SEM, XRD and other techniques were also reviewed

Control of Nanoparticle Growth in High Temperature Reactor: Application of Reduced Population Balance Model

Aerosol processes often are modeled using the population balance equation (PBE). This article presents a study on the simulation of particle size distribution during nanoparticle growth with simultaneous chemical reaction, nucleation, condensation and coagulation. The method used to reduce the population balance model is the method of moments. Under the assumption of lognormal aerosol size distribution, the method of moments was employed to reduce the original model into a set of first-order ODE’s (ordinary differential equations) that accurately reproduce important dynamics of aerosol process. The objective of this study is to investigate if we can use the reduced population balance model for the control of nanoparticle size distribution. The numerical result shows there is a dependence of the average particle diameter on the wall temperatures and the model can thus be used as a basis to synthesize a feedback controller where manipulated variable is the wall temperature of the reactor and the control variable the aerosol size distribution at the outlet of the reactor

Control of Nanoparticle Growth in High Temperature Reactor: Application of Reduced Population Balance Model

Aerosol processes often are modeled using the population balance equation (PBE). This article presents a study on the simulation of particle size distribution during nanoparticle growth with simultaneous chemical reaction, nucleation, condensation and coagulation. The method used to reduce the population balance model is the method of moments. Under the assumption of lognormal aerosol size distribution, the method of moments was employed to reduce the original model into a set of first-order ODE’s (ordinary differential equations) that accurately reproduce important dynamics of aerosol process. The objective of this study is to investigate if we can use the reduced population balance model for the control of nanoparticle size distribution. The numerical result shows there is a dependence of the average particle diameter on the wall temperatures and the model can thus be used as a basis to synthesize a feedback controller where manipulated variable is the wall temperature of the reactor and the control variable the aerosol size distribution at the outlet of the reactor

Numerical Simulation for Nanoparticle Growth in Flame Reactor and Control of Nanoparticles

We review the models and numerical methods used in flame reactor for the modeling and simulation of nanoparticle. And we also review the control of nanoparticle size distribution, some nonlinear control strategies were looked into. A general model in which nanoparticles form in gas phase and grow through chemical reaction, nucleation, condensation and coagulation is discussed. Particles dispersed in a fluid move randomly, due to Brownian motion, and, along their trajectories, they collide with each other. The model is formulated in terms of a detailed population balance which describes how aerosol size distribution evolves with time. For this population balance models a number of different numerical approaches exist. We reviewed sectional, finite element and Monte Carlo methods, method of moment

Fractal Geometry and Porosity

A fractal is an object or a structure that is self‐similar in all length scales. Fractal geometry is an excellent mathematical tool used in the study of irregular geometric objects. The concept of the fractal dimension, D, as a measure of complexity is defined. The concept of fractal geometry is closely linked to scale invariance, and it provides a framework for the analysis of natural phenomena in various scientific and engineering domains. The relevance of the power law scaling relationships is discussed. Fractal characteristics of porous media and the characteristic method of the porous media are also discussed. Different methods of analysis on the permeability of porous media are discussed in this chapter