Performance of a membrane adsorber for trace impurity removal in biotechnology manufacturing

Membrane adsorbers provide an attractive alternative to traditional bead-based chromatography columns used to remove trace impurities in downstream applications. A linearly scalable novel membrane adsorber family designed for the efficient removal of trace impurities from biotherapeutics, are capable of reproducibly achieving greater than 4 log removal of mammalian viruses, 3 log removal of endotoxin and DNA, and greater than 1 log removal of host cell protein. Single use, disposable membrane adsorbers eliminate the need for costly and time consuming column packing and cleaning validation associated with bead-based chromatography systems, and minimize the required number and volume of buffers. A membrane adsorber step reduces process time, floor space, buffer usage, labor cost, and improves manufacturing flexibility. This "process compression" effect is commonly associated with reducing the number of processing steps. The rigid microporous structure of the membrane layers allows for high process flux operation and uniform bed consistency at all processing scales.     

Formation of Optimal Working Space in Adsorbers with Fixed and Moving Adsorbent Beds

The possibility of improving the adsorbent efficiency by means of transverse, longitudinal sectioning of adsorption apparatus is substantiated. Results of an experimental and calculation study of sectioned apparatus are presented. A number of designs of sectioned adsorbers with the optimal working space were developed.     

Fire hazard evaluation of activated carbons

Journal of Thermal Analysis and Calorimetry - Activated carbons are widely used in the iodine adsorbers in nuclear plants, but little information about their combustibility is available for fire...     

Removal of heavy metals by using adsorption on alumina or chitosan

The removal of heavy metals from wastewater by using activated alumina or chitosan as adsorbers was evaluated. Cd(II) and Cr(III) were employed as models of the behaviour of divalent and trivalent metal ions. The adsorption of Cd(II) and Cr(III) onto the adsorbers evaluated was studied as a function of pH, time, amount of adsorber, concentration of metal ions and sample volume. A 0.4-g portion of activated alumina can retain 0.6 mg Cr(III) and 0.2 mg Cd(II) from 20 mL sample adjusted at pH 4 and stirred for 30 min. It is therefore possible to totally decontaminate 500 mL of a waste containing 5 mg L(-1) Cd(II) and Cr(III) with 10 g alumina. On the other hand, 0.4 g chitosan can totally decontaminate 20 mL of a pH 5 solution containing up to 50 mg L(-1) Cd(II) and Cr(III). A 99.2+/-0.1% retention of Cd(II) and 83+/-1% retention of Cr(III) was obtained from 500 mL of a laboratory waste. The aforementioned strategies were applied for the minimization of analytical chemistry teaching laboratories and atomic spectrometry laboratory wastes. On comparing both adsorbers it can be concluded that chitosan is more preferable than alumina due to the reduced price of chitosan and the absence of side-pollution effects.     

Computer-aided process design of affinity membrane adsorbers: a case study on antibodies capturing

Design of affinity membrane adsorbers for the purification of biomolecules requires a consideration of loading, washing, and elution. Modelling and simulation of membrane adsorbers in literature is, however, strongly focused on the loading step. Therefore, in this work, a complete process model which takes all the different steps into account was developed. Breakthrough experiments in which human IgG was captured onto and eluted from Sartobind Protein A downscale modules were used for model validation and for estimation of the required model parameters. The experimentally observed breakthrough curves were independent of the applied flow rate and from these results linear correlations between lumped kinetic parameters and linear velocity were determined. During elution, desorption was best described by an irreversible reaction of first order in H⁺ concentration. Applicability of the developed model to computer-aided design was illustrated through a process analysis study in which the influence of the amount of loaded protein per cycle on the process yield and productivity was investigated.     

Membrane chromatography: Protein purification from E. coli lysate using newly designed and commercial anion-exchange stationary phases

This contribution describes the purification of anthrax protective antigen (PA) protein from Escherichia coli lysate using bind-and-elute chromatography with newly designed weak anion-exchange membranes. Protein separation performance of the new AEX membrane adsorber was compared with the commercial Sartobind^® D membrane adsorber and HiTrap™ DEAE FF resin column under preparative scale conditions. Dynamic protein binding capacities of all three stationary phases were determined using breakthrough curve analysis. The AEX membrane showed higher binding capacities than the Sartobind^® D membrane at equivalent volumetric throughput and higher capacities than the HiTrap™ DEAE FF resin column at 15 times higher volumetric throughput. Anion-exchange chromatography was performed using all three stationary phases to purify PA protein. Quantitative SDS-PAGE analysis of effluent fractions showed that the purity of PA protein was higher for membrane adsorbers than the HiTrap™ DEAE FF resin column and was the same for the new AEX membrane and Sartobind^® D membrane adsorbers. The effects of E. coli lysate load volume and volumetric flow rate on PA protein separation resolution using the membrane adsorbers were minor, and the peak elution profile remained un-changed even under conditions where >75% of the total protein dynamic binding capacity of the membranes had been utilized. PA protein peak resolution was higher using pH-gradient elution than with ionic strength gradient elution. Overall, the results clearly demonstrate that membrane chromatography is a high-capacity, high-throughput, high-resolution separation technique, and that resolution in membrane chromatography can be higher than resin column chromatography under preparative conditions and at much higher volumetric throughput.     

Enzyme capturing and concentration with mixed matrix membrane adsorbers

This study reports the use of membrane adsorbers for lysozyme (LZ) capturing and concentration: the membrane adsorbers are prepared by incorporation of ion exchange resins into an EVAL porous matrix. The mixed matrix membrane (MMM) adsorber possesses an open and interconnected porous structure with a large ion exchange surface available for enzyme adsorption. The adsorptive membrane features both a high static as well as a high dynamic LZ adsorption capacity. The measured LZ adsorption isotherm is of the Langmuir type, with a maximum adsorption capacity of 147 mg LZ/ml membrane. Dynamic LZ adsorption capacity at a flux of 25 l/h/m² was 63 mg LZ/ml membrane, which is significantly higher than the equivalent commercial membrane Sartobind C. Since the kinetics of desorption processes are faster than the kinetics of adsorption processes, the performance can be improved by exerting the desorption processes at higher fluxes than the adsorption processes. The MMM can be reused in multiple adsorption/desorption cycles maintaining the high binding capacity performance. Fluorescence spectra of the LZ after adsorption and elution were similar to native LZ. This is confirmed by activity tests showing that the activity of LZ was maintained after an adsorption and desorption cycle.     

The role of salts derived from benzilic acid and quinolines in the adsorption of some actinides Part I: Characterization of the adsorbers

The salt of the 8-hydroxyquinoline and benzilic (diphenylglycolic) acid was prepared and incorporated into active charcoal in order to have an adsorber able to concentrate actinides dispersed in natural waters before quantitative or radiochemical analysis. The formation and the characterization of this adsorber, (adsorber B), was compared with another system containing benzilic salt of the substituted quinoline, 2-methyl, 8-hydroxyquinoline, (adsorber R). The adsorption ability of the adsorbers B and R was compared with a third product (adsorber G), prepared by incorporating benzilic acid with d-glucosamine into the charcoal. In this case, d-glucosamine gives a better stability to the system, as otherwise the benzilic acid could partially be dissolved into the water system at equilibrium, during the adsorption experiments. The dissociation acid constants of all the considered components were measured, in order to have some information on the adsorption mechanism. The compound formed during the adsorption on the prepared adsorbers with uranium, thorium, and samarium were separately analyzed and identified by means of IR and NMR. The role of the components in the adsorption was evidenced. This revised version was published online in July 2006 with corrections to the Cover Date.     

The role of salts derived from benzilic acid and quinolines in the adsorption of some actinides

The adsorption conditions of uranium, neptunium, thorium, europium on the adsorbers containing the benzylate salts of the 8-hydroxyquinoline (adsorber B), and of 2-methyl- 8-hydroxyquinoline (adsorber R), were prepared, supported onto charcoal and compared with an adsorber, containing the benzylic acid, (G), stabilized with d-glucoseamine, and adsorbed onto charcoal as well. Thorium, protoactinium, and europium are adsorbed nearly completely from aqueous solutions at a large pH range, even in low acid medium, whereas uranium and neptunium are completely adsorbed only from basic solutions of pH 9. The actinides are preferentially adsorbed with respect to other ions, which are present in natural waters, such as calcium or magnesium. This feature make the analysis of most actinides in natural waters easily to be performed without changing the pH of the original system. The uranium (neptunium) analysis indeed may be accomplished after adjusting the original pH to a fairly basic value (about to 9). The adsorption experiments from real samples showed that the analysis of the actinides dispersed in natural water systems may be successfully performed after previous concentration on the adsorbers prepare. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sampling and analysis of flue gases from a plasma incinerator

A system is described for monitoring flue gases from a plasma incinerator for polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins and polychlorinated dibenzofurans. The system is composed of three basic units: sampler/preconcentrator, gas chromatograph and mass-selective detector. The sampler operates by solid sorbent trapping and thermal desorption. The use of two adsorbers allows sampling at a high flow rate (～1 1 min^?1) and subsequent capillary gas chromatographic analysis without the need for cold traps. A sample trapped on the first adsorber is thermally desorbed and transferred by a carrier stream of 40 cm³ min^?1 to a second smaller adsorber and retrapped. It is then thermally desorbed and injected into the capillary column by a carrier gas at an appropriate flow rate. A sequential valve-minder activates the electric actuators of the two six-port valves used in the design and also controls the power required for heating the adsorbers. Operation of the sampler is automated and is initiated by a single push-button switch. In simulation, the system allowed the separation of the major compounds of interest from possible interferences in <15 min and afforded unambiguous identification of the hazardous compounds and their quantification. For a sample volume of 20 1, the minimum detectable concentration of PCBs is 25–50 ng m^?3.     

Some noble metals and copper content of italian meteorites as determined by destructive neutron activation analysis

Copper, iridium, platinum and gold content was determined in 15 italian chondritic meteorites by destructive neutron activation analysis. The chemical procedure involves few steps: sample dissolution, group separation of noble metals on inorganic adsorbers and gamma-ray spectrometry. Element content and atomic abundances (Si=10⁶ atoms) are presented and discussed. Precision and accuracy of the analytical method are given as well. Copper, platinum and gold content is within the reported ranges for ordinary chondrites, whereas the iridium content is located on the low side of reported values.     

Determination of some noble metals and copper by destructive neutron activation analysis of different matrices

Neutron activation analysis of palladium, iridium, platinum, gold, silver and copper in different matrices was carried out by using inorganic adsorbers such as molybdenum dibromide, zinc ferrocyanide and cadmium metal for their radiochemical separation. The matrices chosen to show the versatility of the method were: high-purity copper and nickel metals, NBS standard reference material SRM 1571 (Orchard leaves), Pultusk meteorite and the U. S. Geological Survey standard rock W-1. The method elaborated is very simple as it involves only a few steps and it has been shown to be accurate and capable of yielding reliable results.     

The determination of vanadium in sea and surface waters

A simple and sensitive method for the determination of vanadium in sea and surface water is presented. The method is based on preconcentration of vanadium on active charcoal at a pH 3.6±0.2, followed by instrumental neutron activation analysis of the charcoal adsorbers and measurement of⁵²V (T=3.71 m). The limit of the determination, which is set by the blank value of the charcoal, is 0.01 μg V·1⁻¹. Data are given for Dutch sea and surface water.     

Adsorption and conversion of various hydrocarbons on monolithic hydrocarbon adsorber

Adsorption and conversion of various hydrocarbons on monolithic hydrocarbon adsorbers were studied using a new experimental model, temperature-programmed adsorption (TPA). In this study, methyl alcohol, acetone, acetaldehyde, 2,2,4-trimethylpentane, n-octane, and toluene were chosen as model hydrocarbons for cold start of a vehicle. The effect of the hydrocarbon components and oxygen concentration on the TPA curve was investigated. Depending on the presence of O(2), the adsorbed and desorbed amounts of the hydrocarbons were decreased, while the conversion efficiency of the hydrocarbons was increased. In the case of hydrocarbons containing oxygen, the thermal decomposition appeared to be in the order methanol, acetaldehyde, and acetone.     

Detailed analysis of membrane adsorber pore structure and protein binding by advanced microscopy

Commercial Sartobind^® porous cation exchanger membranes, based on stabilized regenerated cellulose and with sulfonic acid (S) or carboxylic acid groups (C), were analysed with respect to their pore structure in dry, slightly swollen and wet state by three microscopic methods, conventional scanning electron microscopy (SEM), environmental SEM (ESEM), and confocal laser scanning microscopy (CLSM). The dehydration behaviour of the membranes was in situ observed at varied vapour pressure in the chamber of the ESEM, indicating some deformations of the macropore structure (largest pore diameters up to 20 μm) and significant changes in dimension and mobility of smaller cellulose fibers within these macropores, both as function of water content of the membrane. The binding of mono-Cy5-labelled lysozyme inside fluoresceine-labelled and unlabelled Sartobind^® membranes was monitored by CLSM. The characteristic fluorescence intensity distributions in areas of (146 μm × 146 μm) indicated that protein binding takes place predominately in a layer which is anchored to a fine cellulose fiber network and, to a lower degree, directly to thick cellulose fibers. Due to the limited thickness of this binding layer, a significant fraction of the macropores remained free of protein. Protein binding as function of concentration and incubation times was also monitored by CLSM and discussed related to the binding isotherms for the membrane Sartobind^® S and C. Further, a flow-through cell for the in situ monitoring with CLSM of protein binding during the binding step was built, and the results obtained for binding of lysozyme in membranes Sartobind^® S indicate this experiment can give very important information on the dynamic behaviour of porous membrane adsorbers during separation: the lateral microscopic resolution in the x, y plane enables the identification of different breakthrough times as function of the location (pore structure), and this information can help to explain possible reasons for axial dispersion (in z-direction) observed in breakthrough analyses of the same separation in a chromatography system. The combination of advanced microscopy with detailed investigations of static and dynamic protein binding will provide a better understanding of the coupling between mass transfer and reversible binding in membrane adsorbers onto separation performance, and it will provide valuable guide-lines for the development of improved membrane adsorbers.     

Effect of pH on Adsorption of Cephalosporin C by A Nonionic Polymeric Sorbent

Adsorption of cephalosporin C in a column charged with a nonionic polymeric sorbent, SP850, was studied at various pH values to assess the effect of pH on the dynamic behavior in column adsorbers. Since cephalosporin C is amphoteric, the fractions of each ionic form were calculated from the pK values at a given solution pH. Single-species isotherm parameters for each ionic form were simultaneously extracted from all sets of adsorption equilibrium data measured at several pH values. The mutual interaction between different ionic forms on SP850 was described by a competitive adsorption, namely the ideal adsorbed solution theory (IAST). This treatment made it possible to simulate the dynamic behavior of cephalosporin C at low pH values properly by a dynamic model which was incorporated with the mutual competitive adsorption.     

Production of molded activated carbon from carbon black and petroleum pitch by alkaline activation

Method for obtaining molded activated carbon on the basis of carbon black, petroleum pitch, and potassium hydroxide is suggested. The method consists in mixing of these components in the presence of a solvent, molding, and subsequent carbonization at temperatures of 600–1000°C, followed by washing. The resulting samples have a specific surface area of up to 700 m² g^–1, total pore volume of 0.6–1.5 cm³ g^–1, and crushing strength of 1–4 MPa. This material can find industrial use in purification of technological gases and fluids in fixed-bed adsorbers.     

Mathematical Modeling of Multicomponent Nonisothermal Adsorption in Sorbent Particles Under Pressure Swing Conditions

A detailed model for nonisothermal sorption of multicomponent mixtures in a single sorbent particle (monodisperse or bidisperse with negligible intracrystalline mass transport limitations) under pressure swing conditions is developed in this study. The dusty-gas model is used to describe the coupling of the molar fluxes, the temperature, the partial pressures and the partial pressure gradients of the components in the pore space of the particle. The variations of the temperature are described by an energy equation in which both convective and conductive modes of heat transport are accounted for. No limitations are imposed on the number of the components in the mixture and on the type of the adsorption isotherm. The model is applied in the investigation of the industrially important air-zeolite 5A system. Two cases with respect to the surrounding gas phase are examined: infinite environment, which is representative for single particle experiments, and finite environment, which is representative for the situation in packed bed adsorbers. It is found that in an infinite environment the external and internal temperature gradients are equally important while in a finite environment the external heat transport limitations are negligible. It is concluded that in modeling the nonisothermal operation of adsorption processes occurring in packed beds it is not necessary to allow for the temperature differences between the gas phase and the surface of the adsorbing particles. Furthermore, if the temperature gradients within the particles can be neglected, only a single temperature equation is needed to describe the energy transport in the bed.