Adsorption and desorption of mixtures of organic vapors on beaded activated carbon

In this study, adsorption and desorption of mixtures of organic compounds commonly emitted from automotive painting operations were experimentally studied. A mixture of two alkanes and a mixture of eight organic compounds were adsorbed onto beaded activated carbon (BAC) and then thermally desorbed under nitrogen. Following both adsorption and regeneration, samples of the BAC were chemically extracted. Gas chromatography-mass spectrometry (GC-MS) was used to quantify the compounds in the adsorption and desorption gas streams and in the BAC extracts. In general, for both adsorbate mixtures, competitive adsorption resulted in displacing low boiling point compounds by high boiling point compounds during adsorption. In addition to boiling point, adsorbate structure and functionality affected adsorption dynamics. High boiling point compounds such as n-decane and 2,2-dimethylpropylbenzene were not completely desorbed after three hours regeneration at 288 °C indicating that these two compounds contributed to heel accumulation on the BAC. Additional compounds not present in the mixtures were detected in the extract of regenerated BAC possibly due to decomposition or other reactions during regeneration. Closure analysis based on breakthrough curves, solvent extraction of BAC and mass balance on the reactor provided consistent results of the amount of adsorbates on the BAC after adsorption and/or regeneration.     

Trichloroethylene adsorption by fibrous and granular activated carbons: aqueous phase, gas phase, and water vapor adsorption studies

The important adsorption components involved in the removal of trichloroethylene (TCE) by fibrous and granular activated carbons from aqueous solutions were systematically examined. Namely, adsorption of TCE itself (i.e., TCE vapor isotherms), water molecules (i.e., water vapor isotherms), and TCE in water (i.e., TCE aqueous phase isotherms) were studied, side-by-side, using 20 well-characterized surface-modified activated carbons. The results showed that TCE molecular size and geometry, activated carbon surface hydrophilicity, pore volume, and pore size distribution in micropores control adsorption of TCE at relatively dilute aqueous solutions. TCE adsorption increased as the carbon surface hydrophilicity decreased and the pore volume in micropores of less than 10 A, especially in the 5-8 A range, increased. TCE molecules appeared to access deep regions of carbon micropores due to their flat geometry. The results indicated that characteristics of both adsorbate (i.e., the molecular structure, size, and geometry) and activated carbon (surface hydrophilicity, pore volume, and pore size distribution of micropores) control adsorption of synthetic organic compounds from water and wastewaters. The important micropore size region for a target compound adsorption depends on its size and geometry.     

柚子皮生物活性炭的制备及对有机染料和气态甲醛的吸附研究

本文以柚子皮为原料,ZnCl₂为活化剂和阻燃剂,通过高温热解法制备柚子皮生物活性炭(Biomass ActivatedCarbon,BAC),并研究其对有机染料和甲醛的吸附性能。结果表明,在炭化温度为500℃、ZnCl₂溶液浓度为20 g/L、浸渍比为3:1、浸渍时间为24 h、炭化时间为45 min时得到的BAC,其表面孔状结构明显,表面含有丰富的C=O、O-H和C-O含氧活性官能团。测得其比表面积为983.27 m²/g,总孔容为0.56 cm3/g,平均孔径2.26 nm。同时,BAC对染料的吸附属准二级动力学吸附,吸附量分别为75.81、96.19、64.06 mg/g。在此基础上,用1.0 g BAC吸附实际染料废水中染料,吸附率可达90%以上。将BAC应用于甲醛的吸附中,其对甲醛的吸附量为6.0~9.5 μg/g。     

Control of electrothermal heating during regeneration of activated carbon fiber cloth

Electrothermal swing adsorption (ESA) of organic gases generated by industrial processes can reduce atmospheric emissions and allow for reuse of recovered product. Desorption energy efficiency can be improved through control of adsorbent heating, allowing for cost-effective separation and concentration of these gases for reuse. ESA experiments with an air stream containing 2000 ppm(v) isobutane and activated carbon fiber cloth (ACFC) were performed to evaluate regeneration energy consumption. Control logic based on temperature feedback achieved select temperature and power profiles during regeneration cycles while maintaining the ACFC's mean regeneration temperature (200 °C). Energy requirements for regeneration were independent of differences in temperature/power oscillations (1186-1237 kJ/mol of isobutane). ACFC was also heated to a ramped set-point, and the average absolute error between the actual and set-point temperatures was small (0.73%), demonstrating stable control as set-point temperatures vary, which is necessary for practical applications (e.g., higher temperatures for higher boiling point gases). Additional logic that increased the maximum power application at lower ACFC temperatures resulted in a 36% decrease in energy consumption. Implementing such control logic improves energy efficiency for separating and concentrating organic gases for post-desorption liquefaction of the organic gas for reuse.     

Impact of surface heterogeneity on mercury uptake by carbonaceous sorbents under UHV and atmospheric pressure

Chemical and morphological heterogeneities of carbon sorbents play important roles in gas-phase adsorption. However, the specific chemical complexes and topological structures of carbon that favor or impede elemental mercury uptake are not well understood and are the subject of this study. Temperature programmed desorption (TPD) with a model carbonaceous material (highly oriented pyrolytic graphite, HOPG) under ultrahigh vacuum (UHV) conditions and fixed bed adsorption by activated carbon (BPL) at atmospheric pressure were combined to investigate the effects of chemical and morphological heterogeneities on mercury adsorption by carbonaceous surfaces. TPD results show that mercury adsorption at 100 K onto HOPG surfaces with and without chemical functional groups and topological heterogeneity created by plasma oxidation occurs through physisorption. The removal of chemical functionalities from the HOPG surface enhances mercury physisorption. Plasma-oxidation of HOPG provides additional surface area for mercury adsorption. However, the pits created by plasma oxidation are more than 10 nm in diameter and do not simulate microporosity that predominates in activated carbons. Mercury adsorption by activated carbon at atmospheric pressure occurs through two distinct mechanisms. Physisorption governs mercury adsorption at lower temperatures (i.e., below 348 K), while chemisorption predominates at high adsorption temperatures (i.e., above 348 K). Presence of water on activated carbon surface enhances mercury uptake by both physisorption and chemisorption. Oxygen containing functional groups reduce mercury uptake by physisorption by blocking access to the micropores. No significant impact of oxygen functionalities was observed in the chemisorption regime. The key findings of this study open the possibility to apply scientific information obtained from the studies with simple surfaces such as HOPG under ideal conditions (UHV) to industrial sorbents under realistic process conditions.     

Examination of hydrophobic contaminant adsorption in mineral micropores with grand canonical Monte Carlo simulations

A molecular level understanding of the interactions between hydrophobic organic contaminants (HOCs) and sediments is needed in order to assess contaminant fate in the environment. Grand canonical Monte Carlo simulations were performed to investigate water and trichloroethylene (TCE) adsorption in slit micropores confined by charged and uncharged silica surfaces. Gas-phase single-sorbate simulations with water or TCE were performed as well as mixture simulations of bulk water containing TCE at 1% of its saturation concentration. Gas-phase isosteric heats for water adsorption in the uncharged pores ranged from -40 to -52 kJ/mol, and the densities of the adsorbed water phases were always less than that for bulk water. Gas-phase isosteric heats for water adsorption in the charged pores ranged from -79 to -170 kJ/mol, and the densities of the adsorbed water phases were close to that for bulk water. The isosteric heats and water densities indicated that the uncharged pores were mildly hydrophobic, and the charged pores were very hydrophilic. In mixture simulations of adsorption from solution, the presence of water promoted TCE adsorption in uncharged pores with widths between 14 and 20 A. The isosteric heats for TCE adsorption from solution ranged from -14 to -27 kJ/mol in the uncharged pores and from -9.3 to -50 kJ/mol in the charged pores. Strong attractions to the pore surfaces were significantly diminished after adsorption of the first two monolayers of either adsorbate. Aqueous-phase TCE at a concentration equal to 1% of its saturation concentration was able to completely displace adsorbed water in uncharged pores. Even in highly hydrophilic pores, TCE at this concentration was able to displace up to 50% of the adsorbed water. Apparent differential enthalpies of adsorption determined from the temperature dependence of TCE adsorption isotherms underestimated the magnitude of the true isosteric heats of adsorption by up to 30 kJ/mol. This shows that HOC adsorption enthalpies determined from the temperature dependence of their adsorption isotherms underestimate the true strength of HOC-adsorbent interactions.     

Activated carbon fiber cloth electrothermal swing adsorption system

Capture and recovery of hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) from gas streams using physical adsorption onto activated carbon fiber cloth (ACFC) is demonstrated on the bench-scale. This system is regenerated electrothermally, by passing an electric current directly through the ACFC. The adsorbate desorbs from the ACFC, rapidly condenses on the inside walls of the adsorber, and then drains from the adsorber as a pure liquid. Rapid electrothermal desorption exhibits such unique characteristics as extremely low purge gas flow rate, rapid rate of ACFC heating, rapid mass transfer kinetics inherent to ACFC, and in-vessel condensation. An existing system was scaled up 500%, and the new system was modeled using material and energy balances. Adsorption isotherms using methyl ethyl ketone (MEK) and ACFC were obtained while electricity passed through the ACFC and at temperatures above MEK's boiling point. These isotherms agreed within 7% to Dubinin-Radushkevich modeled isotherms that were extrapolated from independently determined gravimetric measurements obtained at lower temperatures. Energy and material balances for the electrothermal desorption of organic vapors and ACFC agree to within 7% of experimentally measured values. These results allow the modeling of electrothermal desorption of organic vapors from gas streams with in-vessel condensation to optimize operating conditions of the system during regeneration of the adsorbent.     

Gravimetric analysis of the adsorption and desorption of CO2 on amine-functionalized mesoporous silica mounted on a microcantilever array

The kinetics of CO(2) adsorption and desorption over amine-functionalized mesoporous silica were investigated using silicon microcantilever arrays. Three types of mesoporous silica with different pore sizes were synthesized and functionalized with a variety of amine molecules. After depositing the silica sorbents onto the free end of each cantilever in an array, mass changes due to the adsorption and desorption of CO(2) were determined in situ with picogram sensitivity by measuring variations in the cantilever frequencies. The adsorption and desorption kinetics were found to be diffusion-controlled, and the kinetics were accelerated by increasing the temperature and pore size. The activation energies for adsorption and desorption of CO(2) were determined from Arrhenius plots.     

Modeling maximum adsorption capacities of soot and soot-like materials for PAHs and PCBs

Recent studies have shown that not partitioning but adsorption is the main mechanism for sorption of hydrophobic organic compounds to soot and soot-like materials. For compounds that adsorb by van derWaals forces only, variation in soot-water distribution coefficients will result from differences in these forces for adsorption, as well as the maximum number of accessible sites. This maximum number of accessible sites may a priori be expected to vary due to differences in both sorbent characteristics and sorbate dimensions. In this modeling study, variation in maximum adsorption capacities is explained from sorbent and sorbate properties. Maximum adsorption capacities were calculated using (a) literature values for soot-water distribution coefficients for polycyclic aromatic hydrocarbons and polychlorobiphenyls on 10 different soot and soot-like materials and (b) Langmuir affinities for adsorption at a carbonaceous surface estimated using a recently reported method. The variation in maximum adsorption capacities could be explained by the variation in sorbent specific surface area, sorbent organic carbon content, and the sorbent-sorbate contact area. Furthermore, increasing sorbate thickness was related to a decrease in maximum adsorption capacities, which points to adsorption in micropores. Maximum adsorption capacities decreased by 1-2 orders of magnitude as the contact area increased by 50%. This points to adsorption sites being hardly larger than sorbates.     

CO2 adsorption on carbon models of organic constituents of gas shale and coal

Imperfections of the organic matrix in coal and gas shales are modeled using defective and defect-free graphene surfaces to represent the structural heterogeneity and related chemical nature of these complex systems. Based upon previous experimental investigations that have validated the stability and existence of defect sites in graphene, plane-wave electronic density functional theory (DFT) calculations have been performed to investigate the mechanisms of CO(2) adsorption. The interactions of CO(2) with different surfaces have been compared, and the physisorption energy of CO(2) on the defective graphene adsorption site with one carbon atom missing (monovacancy) is approximately 4 times as strong as that on a perfect defect-free graphene surface, specifically, with a physisorption energy of ～210 meV on the monovacancy site compared to ～50 meV on a perfect graphene surface. The energy associated with the chemisorption of CO(2) on the monovacancy site is substantially stronger at ～1.72 eV. Bader charge, density of states, and vibrational frequency estimations were also carried out and the results indicate that the CO(2) molecule binds to the surface becoming more stable upon physisorption onto the monovacancy site followed by the original C═O bonds weakening upon CO(2) chemisorption onto the vacancy site.     

Effects of powdered activated carbon pore size distribution on the competitive adsorption of aqueous atrazine and natural organic matter

The pore size distribution (PSD) of adsorbents has been found to be an important factor that affects adsorption capacity for organic compounds; consequently, it should influence competitive adsorption in multisolute systems. This research was conducted to show howthe PSD of activated carbon affects the competition between natural organic matter (NOM) and the trace organic contaminant atrazine, with a primary emphasis on quantifying the pore blocking mechanism of NOM competition. Isotherm tests were performed for both atrazine and NOM from a groundwater on five powdered activated carbons (PACs) with widely different PSDs. The capacity for NOM correlated best with the surface area of pores in the diameter range of 15-50 A, although some NOM also adsorbed in the smaller pores as evidenced by a reduction in capacity for atrazine when NOM was present. Kinetic tests for atrazine on PACs with various levels of preadsorbed NOM showed that the magnitude of the pore blockage effect by NOM was lower for PACs with higher surface area of pores with diameter in the range of 15-50 A. Therefore increasing pores in the size range where NOM adsorb can reduce the extent of the pore blockage competitive effect on the target compound atrazine. The effect of PSD was further studied with a flow-through PAC-membrane hybrid watertreatment system, in which experimental results successfully verified model simulations by the COMPSORB model.     

Assessing sequestration of selected polycyclic aromatic hydrocarbons by use of adsorption modeling and temperature-programmed desorption

Sequestration of phenanthrene and pyrene was investigated in two soils--a sandy soil designated SBS and a silt-loam designated LHS--by combining long-term batch sorption studies with thermal desorption and pyrolysis of amended soil samples. The Polanyi-based adsorption volume and the adsorbed solute mass increased with aging for both soils, thus demonstrating the mechanism for observed sequestration. Despite rigorous thermal analysis, 30-62% (SBS sand) and 8-30% (LHS silt-loam) of phenanthrene could not be recovered after 30-270 days of sorption, with the increase in desorption resistance showing greater significance in SBS sand. For both soils, these values were 20-65% of adsorbed phenanthrene mass. Activation energies estimated from the temperature-programmed desorption (TPD) of sorbed phenanthrene at < or = 375 degrees C were 51-53 kJ/mol, consistent with values derived for desorption of organic compounds from humic materials. The activated first-order model fitting of observed TPD data supports the conclusion that the desorption-resistant fraction of phenanthrene has become sequestered onto condensed organic domains and requires temperatures exceeding 600 degrees C to be released. The work demonstrates the use of thermal analysis in complementing the Polanyi-based adsorption modeling approach for assessing the mechanistic basis for sequestration of organic contaminants in soils.     

Microwave-swing adsorption to capture and recover vapors from air streams with activated carbon fiber cloth

Adsorption with regeneration is a desirable means to control the emissions of organic vapors such as hazardous air pollutants (HAPs) and volatile organic compounds (VOCs) from air streams as it allows for capture, recovery, and reuse of those VOCs/HAPS. Integration of activated-carbon fiber-cloth (ACFC) adsorbent with microwave regeneration provides promise as a new adsorption/ regeneration technology. This research investigates the feasibility of using microwaves to regenerate ACFC as part of a process for capture and recovery of organic vapors from gas streams. A bench-scale fixed-bed microwave-swing adsorption (MSA) system was built and tested for adsorption of water vapor, methyl ethyl ketone (MEK), and tetrachloroethylene (PERC) from an airstream and then recovery of those vapors with microwave regeneration. The electromagnetic heating behavior of dry and vapor-saturated ACFC was also characterized. The MSA system successfully adsorbed organic vapors from the airstreams, allowed for rapid regeneration of the ACFC cartridge, and recovered the water and organic vapors as liquids.     

Measurement and modeling of single- and multi-component adsorption equilibria of VOC on high-silica zeolites

From pure and binary gas adsorption equilibria measurements carried out using a volumetric method for three volatile organic compounds (methyl ethyl ketone, toluene (TOL), and 1,4-dioxane) on two high-silica zeolites, desaluminated faujasite Y (Fau Y) and ZSM-5 (Sil Z), co-adsorption was investigated and modeled. Apart from steric exclusion taking place with TOL-containing mixtures on Sil Z, micropore filling was similar to distillation since the component with the lower volatility adsorbed preferentially. At low coverage, chemisorption on specific sites happened in favor of polar or major compound, whereas at saturation the adsorbent was selective for the minor compound. Second, a quantitative prediction of binary equilibria was performed using the ideal adsorbed solution theory (IAST), examining the influence of pure component adsorption fitting model. The efficiency of correlations when extending AST to real mixture behavior was satisfactory in most cases. For engineering purposes, Fau Y is to be considered as a high-adsorption capacity adsorbent, whose selectivity can be described qualitatively by the distillation analogy and predicted quantitatively with the IAST in case of quasi-ideal mixtures.     

Cadmium adsorption on aluminum oxide in the presence of polyacrylic acid

Adsorption of metals from aqueous solution onto oxide and other surfaces is known to affect trace metal transport in many natural and engineered systems. It is therefore important to understand whether dissolved metal inputs will be easily bound to particles or will be strongly complexed in solution and transported with the water phase. The effect of poly(acrylic acid) (PAA), representing a model compound for natural organic matter, on the adsorption of Cd(II) onto gamma-Al2O3 was determined using batch adsorption experiments over a pH range from 4 to 10. Initially, interactions among the individual components were evaluated. Cadmium adsorption onto alumina showed a typical S-shaped metal adsorption curve. PAA adsorption onto gamma-Al2O3 decreased with increase in pH. The affinity of PAA for Cd2+ increased strongly with pH. In ternary systems, the presence of PAA resulted in an enhancement of Cd(II) adsorption below pH 6, apparently due to ternary surface complex formation. Above pH 6, a decrease in cadmium adsorption onto gamma-Al2O3 was observed resulting from an increase in the concentration of soluble Cd-PAA complexes. Overall, results indicate that the presence of natural organic matter could have a significant impact on the distribution and mobility of cadmium in the environment. Simple surface complexation modeling was insufficient to describe behavior in the ternary systems due to the complexity of the PAA polymer.     

Experimental and molecular mechanics and ab initio investigation of activated adsorption and desorption of trichloroethylene in mineral micropores

This research investigated activated adsorption of a hydrophobic organic contaminant(HOC) in mineral micropores using experimental and molecular modeling techniques. Adsorption of trichloroethylene (TCE) on a silica gel adsorbent was measured using a frontal analysis chromatography technique at atmospheric and elevated fluid pressures. Increasing the fluid pressure yielded increased TCE uptake that was not released upon lowering the pressure back to atmospheric conditions. This showed that the increase in pressure was able to rapidly induce the formation of a desorption-resistant fraction that previous investigations have shown requires months to develop at atmospheric pressure. Grand Canonical Monte Carlo (GCMC) modeling was then used to elucidate the nature of water and TCE behavior within silica micropores. The GCMC modeling showed that molecular scale packing restrictions resulted in pore fluid densities that ranged from 0.28 to 0.78 of those in the bulk solution. The modeling also showed that TCE was able to displace water from hydrophilic mineral pores due to molecular scale packing restrictions. Exothermic isosteric heats for TCE adsorption up to -27 kJ/mol were observed and were greatest in pores of 7 and 8 A. This indicated that TCE adsorption was energetically most favorable in pores that were minimally large enough to accommodate a TCE molecule. The pressure-induced uptake appeared to result primarily from an increase in the packing density in the smallest pores. Ab initio calculations showed that small distortions of a TCE molecule from its low energy conformation require high activation energies. Results from this study indicate that activated adsorption requiring bond angle distortions in the adsorbate may be responsible forthe slow attainment of adsorptive equilibrium of HOCs on microporous solids. Likewise, activated desorption from molecular-sized adsorption sites may contribute to the slow release of HOCs from aquifer sediments.     

Mechanistic characterization of adsorption and slow desorption of phenanthrene aged in soils

Long-term adsorption of phenanthrene to soils was characterized in a silt-loam (LHS), a sandy soil (SBS), and a podzolized soil (CNS) by use of the Polanyi-Manes model, a Langmuir-type model, and a black carbon-water distribution coefficient (K(BC)) at a relative aqueous concentration (C(e)/S(w)) of 0.002-0.32. Aqueous desorption kinetic tests and temperature-programmed desorption (TPD) were also used to evaluate phenanthrene diffusivities and desorption activation energies. Adsorption contribution in soils was 48-70% after 30 days and 64-95% after 270 days. Significant increases in adsorption capacity with aging suggest that accessibility of phenanthrene to fractions of SBS soil matrix was controlled by sorptive diffusion at narrow meso- and micropore constrictions. Similar trends were not significant for LHS silt-loam or CNS podzol. Analysis of TPD profiles reveal desorption activation energies of 35-53 kJ/mol and diffusivities of 1.6 x 10(-7-)9.7 x 10(-8) cm2/s. TPD tests also indicate that the fraction of phenanthrene mass not diffusing from soils was located within micropores and narrow width mesopores with a corresponding volume of 1.83 x 10(-5-)6.37 x 10(-5) cm3/g. These values were consistent with the modeled adsorption contributions, thus demonstrating the need for such complimentary analytical approach in the risk assessment of organic contaminants.     

钆金属有机框架的制备及用于吸附辛硫磷的研究

金属有机框架材料(MOFs)是一种由金属离子和有机配体通过配位作用,组装成新型的多孔晶体材料。本试验以GdCl_3·6H_2O和H_3BTC为原料制备钆金属有机框架(Gd-MOF),并考察其对辛硫磷农药的吸附性能。结果表明,Gd-MOF能有效地吸附水中的辛硫磷农药,吸附量为33.5mg/g;当Gd-MOF加入量为40～80mg时,辛硫磷的吸附率最高可达90%;且在pH 3～7范围内对辛硫磷有一定的吸附力。推测Gd-MOF对辛硫磷的吸附可能是其孔径结构和Gd~(3+)对辛硫磷分子间磷氧键有络合作用。Gd-MOF再生试验结果表明:Gd-MOF有良好的循环使用性能,可作为一种新型的去除水中辛硫磷农药的复合材料。     

Effect of natural organic substances on the surface and adsorptive properties of environmental black carbon (char): attenuation of surface activity by humic and fulvic acids

Black carbon (BC) plays a potentially important role in the availability of pollutants in soils and sediments. Recent evidence points to the possible attenuation of the high surface activity of raw BC by natural substances. We studied the effects of soil humic (HA) and fulvic (FA) acids on the surface properties and affinity for organic compounds of synthesized wood charcoal. Char powder suspended in a solution of HA or FA was loaded with organic matter via adsorption, evaporation of the water, or coflocculation with Al3+. These treatments were chosen to simulate initial and more advanced stages of environmental exposure. Coevaporation dramatically reduced the N2 Brunauer-Emmett-Teller total surface area of the char, but only moderately the CO2 cumulative surface area up to 1.4 nm. Organic compound adsorption was suppressed in proportion to molecular size, benzene < naphthalene < phenanthrene and 1,2,4-trichlorobenzene < phenanthrene, for humics in the adsorbed and coflocculated states, respectively. Humic substances also increased the linearity of the isotherms. The model we propose assumes that humic substances are restricted to the external surface where they act as pore blocking agents or competitive adsorbates, depending on the temperature and adsorbate size. Nitrogen is blocked from the internal pore space due to stiffness at 77 K of humic strands extending into pore throats, giving an artificially low surface area. Together with previous results, this finding indicates that N2 may not detect BC microporosity in geosorbents. At higher temperatures (CO2, 273 K; organics, 293 K), humic strands are more flexible, allowing access to interior pores. The counterintuitive molecular size dependence of adsorption suppression by humics is due to a molecular sieving effect in pores in which the adsorption space available to the organic compound is more and more restricted to external sites.     

Competitive effects of natural organic matter: parametrization and verification of the three-component adsorption model COMPSORB

Natural organic matter (NOM) hinders adsorption of trace organic compounds on powdered activated carbon (PAC) via two dominant mechanisms: direct site competition and pore blockage. COMPSORB, a three-component model that incorporates these two competitive mechanisms, was developed in a previous study to describe the removal of trace contaminants in continuous-flow hybrid PAC adsorption/membrane filtration systems. Synthetic solutions containing two model compounds as surrogates for NOM were used in the original study to elucidate competitive effects and to verify the model. In the present study, a quantitative method to characterize the components of NOM that are responsible for competitive adsorption effects in natural water was developed to extend the application of COMPSORB to natural water systems. Using batch adsorption data, NOM was differentiated into two fictive fractions, representing the strongly competing and pore blocking components, and each was treated as a single compound. The equilibrium and kinetic parameters for these fictive compounds were calculated using simplified adsorption models. This parametrization procedure was carried out on two different natural waters, and the model was verified with experimental data obtained for atrazine removal from natural water in a PAC/membrane system. The model predicted the system performance reasonably well and highlighted the importance of considering both direct site competition and pore blockage effects of NOM in modeling these systems.