Water-soluble conjugated polyelectrolyte with pendant glycocluster: Synthesis and its interaction with heparin

A novel fluorescent conjugated polyelectrolyte with pendant glucosamine hydrochloride clusters was prepared through Cu(I)-catalyzed azide/alkyne “click” ligation and Suzuki coupling polymerization. Compared with monosugar-functionalized conjugated polymer, the water-solubility and fluorescence quantum yield of the glycocluster-containing polymer (P-3) were significantly improved. As a glucosamine-containing cationic fluorescent polyelectrolyte, the water-soluble fluorescent polymer can interact with heparin through electrostatic bindings, which induce great fluorescence quenching of P-3 due to the polymer aggregation. Furthermore, upon treatment of the P-3-heparin ensemble with protamine, the fluorescence emission of P-3 recovered since the protamine possesses a competitively strong binding affinity to the heparin and thus results in the release of the fluorescent glycopolymer P-3 from the P-3-heparin ensemble.     

Water-soluble functional polymers in conjunction with membranes to remove pollutant ions from aqueous solutions

Water-soluble functional polymers have attracted a lot of attention due to their potential applications in different research fields. In environmental sciences, they can be used to remove pollutants. Since properly modified polymer materials can be used to avoid the growth of bacteria, fungi, and algae, they also attract interest from diverse biomedical fields.This review places special emphasis on the study of water-soluble polymers that contain one or more amine, amide, carboxylic acid, hydroxyl, phosphonic acid, quaternary ammonium salts, and sulfonic acid groups at the backbone or side chain and their ability to remove ion pollutants from aqueous solutions. In additional, this review differentiates between different experimental procedures, including the liquid-phase polymer based retention (LPR) technique that combines the use of water-soluble polymers and ultrafiltration membranes, as well as arsenic removal by combining LPR and electrocatalytical oxidation (EO) techniques. EO and LPR can also be coupled off-line to remove arsenic inorganic species from aqueous solutions. A variety of studies show that the functional groups on the polymer and the solution pH have a marked effect on ion removal.     

Microfluidic modeling and simulation of flow in membrane microreactors

We study the development of a mathematical model that describes isothermal microfluidic steady flow in a membrane microreactor, i.e., a silicon microreactor that houses a permeable membrane in one wall. The model employs the Navier-Stokes equation with appropriate boundary conditions for fluid permeation through the membrane and velocity slip at the walls to account for high Knudsen number. The model equations are solved analytically using finite Fourier transforms. The model solution is used to evaluate the effect of fluid permeation through the membrane and the Knudsen number on the velocity profile and pressure drop. For the simplified cases of no permeation and/or no slip, the derived solution is in excellent agreement with published experimental and theoretical results available in the literature. The utility of the model is illustrated by applying the results to a membrane microseparator used to separate hydrogen from the other effluents in a microreformer.     

Reduced-order modeling of flow and concentration polarization in membrane systems with permeation

Modeling of concentration polarization (CP) is important to ensure a successful membrane system design. Although computational fluid dynamics (CFD) remains a common approach to study CP, it usually requires a long computational time to investigate a short simulated time in membrane systems. In this work, we proposed a reduced-order model to predict CP in membrane systems with permeation. We modify Berman's velocity profile and incorporated it to the reduced-order model of the mass-transfer equation. The proposed model shows excellent agreement with CFD results, while offering a reduction of two orders of magnitude in computational time. We also validate the model with published experimental data and demonstrate that the model can predict permeate flux in close proximity under various operating conditions. The proposed model offers an attractive alternative to solving the full Navier–Stokes and mass-transfer equations, and opens the possibility to further investigate various approaches to reduce concentration polarization.     

Mathematical modeling and numerical simulation of ammonia removal from wastewaters using membrane contactors

This study investigates simulation of ammonia transport through membrane contactors. The system studied involves feed solution of NH₃, a dilute solution of sulfuric acid as solvent and a membrane contactor. The model considers coupling between equations of motion and convection-diffusion. Finite element method was applied for numerical calculations. The effect of different parameters on the removal of ammonia was investigated. The simulation results revealed that increasing feed velocity decreases ammonia removal in the contactor. The modeling findings also showed that the developed model is capable to evaluate the effective parameters which involve in the ammonia removal by means of contactors.     

Mathematical modeling and simulation studies of scale-down fermentation systems

In this study, a scale-down approach has been used for the simulation of the imperfect mixing on the growth processes by considering several configurations of continuous stirred tank reactor (CSTR, aerated) and plug flow tubular reactor (PFTR, not aerated). The steady-state concentrations of biomass and enzyme in a continuous culture were calculated as a function of dilution rate using modified Monod growth kinetics. A mathematical model for each combination of two bioreactors was developed to account for growth, substrate utilization (oxygen and glucose) and enzyme synthesis and decay. The model was then used to investigate biomass production and enzyme expression in relation to the volumetric fraction U_f = V_PFTR /(V_CSTR + V_PFTR ) and the recirculation ratio R = f_r/(f + f_r) of the fermentation system. These two mixing parameters were found to be significant factors in the biomass and enzyme production from the fermentation system. This model was also compared with some of the existing models.     

Effect of shear and washing on metal retention in ferric flocs

Flocculative wastewater residues present a serious threat to the environment and a costly disposal problem to industry. The composition of the sludges makes them a particularly intractable problem due to the need for either recovery or permanent isolation of the bound contaminant. The primary interest of this work was to determine the effect of conditioning processes such as shear and washing on the retention of heavy metal contaminants (nickel, cadmium, copper, zinc) within ferric flocs. Shear was found to produce an increase in the leach‐out of certain heavy metals, including cadmium and nickel. Copper and nickel were unaffected by the application of shear. The extent of contaminant leaching, due to shear, increased with increasing contaminant to floc ratio. Repeated washing of the floc readily removed sodium ions, however, contaminant metal ions reformed an equilibrium with the washwater and the floc with every washing. © 2002 Society of Chemical Industry     

Solubility parameter estimation and phase inversion modeling of bentonite-doped polymeric membrane systems

Effects of bentonite concentration on morphology and permeation characteristics of bentonite-doped polysulfone membranes were investigated. Solubility sphere for bentonite was constructed to estimate its solubility parameter. Thermodynamic modeling of phase inversion of this system was carried out using Flory–Huggins theory. The trade-off between thermodynamic and kinetic parameters was used to predict the membrane morphology for bentonite concentration varying from 0 to 5 wt %. The porosity of bentonite-doped membranes decreased up to 3 wt % that increased thereafter. Morphological analysis showed dense cross section with finger-like macrovoids at 3 wt % beyond which it changed to honeycomb structure with large circular voids. Permeability of 3 wt % membrane was the lowest (5.6 × 10⁻¹² m/Pa s) with 95% bovine serum albumin rejection. Contact angle of the membranes decreased from 83 to 66° with bentonite addition making the membrane more hydrophilic. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48450.     

A modeling framework for design of nonlinear renewable energy systems through integrated simulation modeling and metaheuristic optimization: Applications to biorefineries

This study presents the development and implementation of a novel framework for optimal design of new and emerging renewable energy production systems by considering an iterative strategy which integrates the Net Present Value optimization along with detailed mechanistic modeling, simulation, and process optimization which yields optimal capacity plan, and operating conditions for the process. Due to the non-linear nature of process conversion mechanisms, metaheuristic algorithms are implemented in the framework to optimize operating conditions of process. Further, to apply complex kinetics in the process, we have made a linkage between process simulator (Aspen Plus) and Matlab. To demonstrate the effectiveness of the proposed methodology, a hypothetical case study of a lignocellulosic biorefinery is utilized. The proposed framework results reveal a deviation in optimal process yields and production capacities from initial literature estimates. These results indicate the importance of developing a multi-layered framework to optimally design a renewable energy production system.     

Respirometric method for kinetic modeling of ammonium-oxidizing and nitrite-oxidizing bacteria in a membrane bioreactor

A respirometric method for the kinetic modeling of ammonium-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was implemented in two membrane bioreactor (MBR_A and MBR_B) systems. These biological systems worked at mixed liquor suspended solids concentration of about 6.6 g L⁻¹. MBR_A worked at 6 hr of hydraulic retention time (HRT) and 20.7°C, while the operational conditions for MBR_B were 9.5 hr of HRT and 14.7°C. Experimental data were fitted to the kinetic model with R² values of .9320 and .9250 for MBR_A and MBR_B, respectively. Both systems showed similar performances regarding organic matter and nitrogen removal. However, MBR_B showed highest rates of carbon source degradation and net heterotrophic bacteria growth, and MBR_A had highest rates of nitrogen source degradation and net autotrophic bacteria growth. This last system was characterized by values for Y_AOB, Y_NOB, μ_m,AOB and μ_m,NOB of 1.1749 mgVSS mgN⁻¹, 0.6473 mgVSS mgN⁻¹, 0.3664 hr⁻¹ and 0.1823 hr⁻¹, respectively.     

Modeling and process simulation of hollow fiber membrane reactor systems for propane dehydrogenation

We report a detailed modeling analysis of membrane reactor systems for propane dehydrogenation (PDH), by integrating a two‐dimensional (2‐D) nonisothermal model of a packed bed membrane reactor (PBMR) with ASPEN process simulations for the overall PDH plant including downstream separations processes. PBMRs based on ceramic hollow fiber membranes—with catalyst placement on the shell side—are found to be a viable route, whereas conventional tubular membranes are prohibitively expensive. The overall impact of the PBMR on the PDH plant (e.g., required dimensions, catalyst amount, overall energy use in reaction and downstream separation) is determined. Large savings in overall energy use and catalyst amounts can be achieved with an appropriate configuration of PBMR stages and optimal sweep/feed ratio. Overall, this work determines a viable design of a membrane reactor‐based PDH plant and shows the potential for miniaturized hollow‐fiber membrane reactors to achieve substantial savings. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4519–4531, 2017     

甲基异丙基甲酮-苯酚-对苯二酚-水的液液相平衡数据测定、模型关联及萃取过程模拟

液液相平衡测定为溶剂萃取及回收的准确模拟、设计和过程开发提供基础数据。以甲基异丙基甲酮为萃取剂,在处理高浓煤化工含酚废水的三元液液相平衡萃取基础上,选定其中典型单元酚苯酚和多元酚对苯二酚为代表物,测定甲基异丙基甲酮-苯酚-对苯二酚-水在常压40℃下的液液相平衡数据。采用NRTL和UNIQUAC活度系数模型对实验数据进行热力学关联,回归得到该四元体系的二元交互作用参数。结果表明该模型可以很好地关联实验数据,两种模型的相对均方根偏差分别小于0.190%和0.266%。进一步将得到的二元交互参数导入流程模拟系统,对萃取单元模块进行计算。当萃取温度40℃、萃取级数5级、相比1：7.72时,甲基异丙基甲酮能将总酚12700 mg×L^-1,多元酚4250 mg×L^-1的含酚废水的酚浓度分别降低至300 mg×L^-1和299 mg×L^-1以下。     

Flow modeling and simulation for vacuum assisted resin transfer molding process with the equivalent permeability method

Vacuum assisted resin transfer molding (VARTM) offers numerous advantages over traditional resin transfer molding, such as lower tooling costs, shorter mold filling time and better scalability for large structures. In the VARTM process, complete filling of the mold with adequate wet-out of the fibrous preform has a critical impact on the process efficiency and product quality. Simulation is a powerful tool for understanding the resin flow in the VARTM process. However, conventional three-dimensional Control Volume/Finite Element Method (CV/FEM) based simulation models often require extensive computations, and their application to process modeling of large part fabrication is limited. This paper introduces a new approach to model the flow in the VARTM process based on the concept of equivalent permeability to significantly reduce computation time for VARTM flow simulation of large parts. The equivalent permeability model of high permeable medium (HPM) proposed in the study can significantly increase convergence efficiency of simulation by properly adjusting the aspect ratio of HPM elements. The equivalent permeability model of flow channel can simplify the computational model of the CV/FEM simulation for VARTM processes. This new modeling technique was validated by the results from conventional 3D computational methods and experiments. The model was further validated with a case study of an automobile hood component fabrication. The flow simulation results of the equivalent permeability models were in agreement with those from experiments. The results indicate that the computational time required by this new approach was greatly reduced compared to that by the conventional 3D CV/FEM simulation model, while maintaining the accuracy, of filling time and flow pattern. This approach makes the flow simulation of large VARTM parts with 3D CV/FEM method computationally feasible and may help broaden the application base of the process simulation. Polym. Compos. 25:146–164, 2004. © 2004 Society of Plastics Engineers.     

Removal of metal ions by water‐soluble polymacromonomers in conjunction with ultrafiltration membrane

The macromonomer polyethylene glycol methylether methacrylate was homo‐ and copolymerized with 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid under three feed monomer ratios. The initiator used was ammonium peroxydisulfate (0.2 mol %). All the polymers were completely soluble in water. The copolymer composition was determined by elemental analysis. The metal ion interaction capability of the three polymers was investigated through the liquid‐phase polymer‐based retention (LPR) technique at different values of pH and filtration factor Z. The highest metal ion retention ability was observed at pH 5.0. The homopolymer showed a high selectivity for Ni(II) ions at pH 3.0. The copolymers (PEGMEM)_1.51‐co‐(APSA)_1.00 and (PEGMEM)_1.00‐co‐(APSA)_1.95 showed a high selectivity for Cr(III) ions at pH 3.0. The maximum retention capacity, in general, was similar for the homo‐ and copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2955–2960, 2004     

超细TiO_2粉体洗涤过程中膜污染和再生方法研究

针对陶瓷膜洗涤超细TiO2粉体中Cl-的过程,确定了适合的跨膜压差和膜表面流速,并采用阻力系列模型分析膜污染机理,确定有效的膜再生方法。此过程渗透通量随跨膜压差和膜表面流速的增长而增长,但是增长幅度减缓。合适的跨膜压差和膜表面流速分别为0.10—0.15 MPa和2.0 m/s;主要的膜污染来自粉体在膜表面的沉积;单一的化学和物理清洗方法无法达到理想的清洗效果,采用纯水浸泡、超声波清洗和质量分数0.5%的HCl清洗可使纯水通量恢复至新膜的72%以上,且多次的清洗效果稳定。     

Supercritical fluid flow in porous media: modeling and simulation

The present work aims the modeling and simulation of supercritical fluid flow through porous media. This type of flow appears in several situations of interest in applied science and engineering, as the supercritical flow in porous materials employed in chromatography, supercritical extraction and petroleum reservoirs. The fluid is constituted of one pure substance, the flow is monophasic, highly compressible and isothermal. The porous media is isotropic, possibly heterogeneous, with rectangular format and the flow is two-dimensional. The heterogeneities of porous media are modeled by a simple power law, which describes the relationship between permeability and porosity. The modeling of the hydrodynamic phenomena incorporates the Darcy's law and the equation of mass conservation. Appropriated correlations are used to model, in a realistic form, the density and the viscosity of the fluid. A conservative finite-difference scheme is used in the discretization of the differential equations. The nonlinearity is treated by Newton method, together with the conjugate gradient method. The results of the simulation for pressure and mobility of supercritical and liquid propane flowing through porous media are presented, analyzed and graphically depicted.     

Mechanical modeling and simulation of aerogels: A review

Aerogels are solids with exceptional characteristics, such as ultra-low density, high surface area, high porosity, high adsorption and low-thermal conductivity. Due to these characteristics, aerogels are emerging to be a popular material among the scientific community, since their discovery in 1931. However, their applicability has remained questionable due to the poor mechanical characteristics, such as brittleness and low tensile strength. In the last three decades, due to the rapid development in the computational resources and numerical methods, a deeper understanding of physical behavior and properties of these materials have been extensively investigated. In this work, an effort is made to critically analyze and categorize the computational models and simulation results available for silica, carbon, carbon nanotubes, graphene, and cellulose aerogels. This work focused on a better understanding of how these materials were computationally modeled and simulated over the time-period and at different length-scales, wherein primary approaches, such as molecular dynamics (MD), coarse-grained, micromechanical multiscale and continuum mechanics modeling, were discussed. It also strives to give an insight into the areas where further computational studies are required, which could lead to numerous other application fields. The systematic review provides a mechanistic basis for reliable applications of aerogels.     

Differential retention of carbon, nitrogen and phosphorus in grassland soil profiles with long-term manure application

Liquid hog manure (LHM) is a valuable source of nutrients for farm production. Long-term experimental plots that had received LHM applications of 0, 50, and 100 m³ ha^?1 annually for 20 years were analyzed for total soil C, N and P storage. Applications increased total soil N and P by 1,200 kg N ha^?1 and 850 kg P ha^?1 at 100 m^?3 LHM year^?1, compared to the control treatment. However, C storage did not increase with LHM rates and was lower in the 50 m³ ha^?1 LHM treatment (86 Mg C ha^?1) than in the 0 or 100 m³ ha^?1 treatments (100 Mg C ha^?1). In addition to the limited quantities and high decomposability of the C supplied by LHM, it is hypothesized that LHM stimulated the mineralization of both native soil C and fresh root-derived material. This priming effect was particularly apparent in deeper soil horizons where the decomposability of native C may be limited by the supply of fresh C. This study indicates that while LHM can be a significant source of crop nutrients, it has limited capacity for maintaining or increasing soil C.