Freundlich Sorption Isotherm Research Articles

Adsorption of heavy metals by a sorbent based on pine bark

Sorption properties of the pine bark treated with a 5% urea solution have been studied with respect to heavy metals Cu(II), Ni(II), Zn(II), and Pb(II). The bark subjected to treatment has higher sorption properties and retains several times as many metals as the untreated bark. Parameters of the Langmuir and Freundlich sorption isotherms were obtained. The possible mechanisms of the bark interaction with urea and reasons for an enhanced metal adsorption on the bark treated with urea solution have been also discussed.

Synthesis, characterization and sorption behavior of zirconium(IV) antimonotungstate: An inorganic ion exchanger

Present investigation deals with the hydrothermal synthesis and characterization of a new heteropolyacid salt; zirconium(IV) antimonotungstate. Three different analogues of inorganic cation exchanger zirconium(IV) antimonotungstate have been prepared by mixing potassium pyroantimonate and sodium tungstate into aqueous solution of zirconium oxychloride in the ratio of 2:1:1. The molar concentration of these three metal ions and synthesis conditions such as, refluxing temperature and time have been varied. Emphasis has been made on the sorption characteristics of inorganic ion exchangers for Fe(III) and Hg(II) metal removal from aqueous waste. Good thermal and chemical stabilities have also been observed for exchangers. Investigations have been made on the distribution coefficient ( K d) values for various metal ions. Distribution constants obtained for Fe(III) sorption on ZrSbW-III have been used in order to calculate the thermodynamic parameters like Gibb's free energy, change in enthalpy and entropy. This synthesized ZrSbW-III, three component system ion exchanger is proved to be a good sorbent for Fe(III) but shows less sorption for Hg(II). On the basis of sorption data, the Langmuir and Freundlich sorption isotherm models have also been confirmed. The separation factor ( R L) revealed the favorable nature of the sorption process of metal ions sorption onto ZrSbW-III.

Modeling of transport of radionuclides in beds of crushed crystalline rocks under equilibrium non-linear sorption isotherm conditions

Abstract A simple method for fitting the values of the experimental breakthrough curves in the form of pulse response obtained in dynamic flow column experiments is presented. It is based on the equation obtained by the analytical solution of a 1-D advection-dispersion equation (ADE) under defined conditions (equilibrium dynamics, linear sorption isotherm, constant bed height, pulse input), where the concentration (or activity) dependence on the number of pore volumes is expressed explicitly. It is shown that the method can be used in the case of validity of a non-linear Freundlich sorption isotherm if the experimental data are fitted by means of a Newton-Raphson multidimensional non-linear regression procedure in which the regression function consists of the above mentioned ADE equation and of the equation for a retardation coefficient including the first derivative of the Freundlich equation. Values of four parameters, namely, Freundlich equation parameters (nF, kF), Peclet number (Pe) and integration constant (k int) are sought in the course of the regression procedure. Applicability of the method is demonstrated in the evaluation of breakthrough curves of the 137Cs and 85Sr obtained by dynamic flow column experiments in beds of five different types of crushed crystalline rocks, where synthetic groundwater spiked with both radionuclides is used.

High Carbon Fly Ash as a Sorbent for the Treatment of Petroleum Contaminated Residues

Abstract The potential of using a high carbon fly ash (HCFA), an industrial byproduct, as a sorbent for hydrocarbons, in the treatment of petroleum-related liquid wastes, or as a pretreatment or addition in cement-based stabilization/solidification of petroleum-related solid wastes was assessed. An HCFA sample, whose physicochemical and leaching properties were studied in detail, was used as a test case. Batch sorption experiments were then conducted to determine the sorption capacity of HCFA using deionized water spiked with two groups of hydrocarbons typical of petroleum wastes: aliphatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs). Fourier transform infrared (FTIR) microspectroscopy was conducted to study the spatial distribution and association of hydrocarbons on the sorbent. Results indicate that HCFA has a high sorption capacity for the two groups of hydrocarbons. Data obtained fit the linear and Freundlich sorption isotherm models. FTIR microspectroscopy results showed that the hydroca...

Factors influencing plutonium sorption in shale media

Summary. The extent and factors influencing sorption of plutonium (Pu) in shale media have been studied in batchtype experiments. The equilibrium time and isotherm of Pu sorption have been firstly determined. The effect of shale grain size, aqueous pH, water/solid ratio, co-existing ions (cations and anions) and temperature were studied as the factors likely to influence Pu sorption. The experimental variables included the following: grain sizes in five ranges, 0.12 to 0.15 mm, 0.15 to 0. 18 mm, 0.18 to 0 .25 mm, 0.25 to 0.38 mm, and 0.38 to 0.83 mm; solution pH values of 4, 6, 8, and 10; water/solid ratios of 10 : 0.25, 10 : 0.5, 10 : 0.75, and 10 : 1; temperatures of 20 ◦ C, 40 ◦ C, and 60 ◦ C); and selected coexisting conventional cations including Na + ,F e + ,A l 3+ ,C a 2+ , and K + and anions including SO4 2− ,C O 3 2− ,N O 3 − ,a nd Cl − in each case in solutions of the same total ionic strength. The experimental results demonstrate that the equilibrium time of Pu sorption is 9 d, that the sorption behavior of Pu in the solution is well described by the Freundlich sorption isotherm (Cs = kC N ), and that Pu is strongly sorbed on shale media. The extent of Pu sorption increased with decreasing grain size, apparently in response to the increase in specific surface area and total pore volume. The results also show that Pu sorption increases with increasing solution pH and with increasing water/solid ratio. The influence of co-existing anions on Pu sorption was much stronger, under the same conditions, than that of the cations; this was attributed to Pu complexation in solution, i.e., the complexing apparently weakened the sorption of Pu on shale particles in the solution. Finally, the influence of varying temperature on Pu sorption is found to be less important than that of other factors, but should never be ignored.

EQUILIBRIUM AND KINETIC MODELING OF Zn (II) SORPTION FROM AQUEOUS SOLUTIONS BY SPHAGNUM MOSS PEAT

Equilibrium and kinetics of sorption of Zn (II) ions from aqueous solutions of pH 5 on indigene (Romanian) peat moss were investigated in batch system. The experimental equilibrium sorption data at three temperatures were analysed by Freundlich, Langmuir, Tempkin and Dubinin-Radushkevich sorption isotherm models. Results indicate the following order in to fit the isotherm equations: Langmuir > Tempkin > Dubinin-Radushkevich > Freundlich. The equilibrium sorption capacity determined from Langmuir equation was found to be 12.56 mg/g at 30 o C. The computed thermodynamic parameters indicate the spontaneous and endothermic nature of the sorption process. The FTIR spectra confirm the ion exchange mechanism of the sorption. Different kinetic models were tested in order to identify a suitable kinetic equation; the experimental kinetic data were best correlated by pseudo-second order equation.

Immobilization of oxime derivative on silica gel for the preparation of new adsorbent

A new silica gel compound modified 4,4′-oxy-bis(chlorophenylglyoxime) (CPGO) was synthesized and characterized by infrared spectroscopy, elemental analysis and thermogravimetric analysis. The sorption capacity of such a matrix towards Co(II), Ni(II) and Cu(II) from aqueous solutions was studied. The optimum pH values for the separation of these divalent cations on the sorbent were 5.0, 6.0 and 6.0 for Cu, Co and Ni, respectively. The process of metal separation was followed by batch method, and fitted to a Langmuir and Freundlich sorption isotherms. The maximum sorption capacities (0.055, 0.042, and 0.034 mmol g −1) were found from the Langmuir equation and the enthalpies of binding were 44.96, 71.63, and 68.14 kJ mol −1 for Cu, Co and Ni, respectively. The other thermodynamic parameters calculated from the adsorption results were used to explain the mechanism of the adsorption. For example, the Gibbs free energies of binding agree with the spontaneity of the proposed reaction between cations and basic centers.

Evaluation of Organoclays for Use in Landfill Liners

Organoclay obtained from two constituents' coco-dimethyl benzyl ammonium chloride, and bentonite was used in this study to prepare five admixtures, by varying the amount of organoclay, natural soil, and bentonite. Laboratory ex- periments were conducted on these admixtures with the objective of identification and assessment of their potential for use in landfill liners. The admixtures had the organoclay ranging from 10 to 25%, and bentonite in the range of 0 to 20%. The admixtures prepared were evaluated by conducting laboratory sorption tests and permeability tests for the determina- tion of retardation coefficient, and hydraulic conductivity. Permeability tests were conducted using consolidation per- meameter. Total Organic Carbon (TOC) was determined using TOC Analyzer. Admixture with higher percentage of or- ganoclay exhibits higher organic sorption capacity. Retardation coefficient of the admixtures was determined by curve fit- ting the experimental data of sorption tests to fit to Freundlich (nonlinear) sorption isotherm. One-dimensional transport simulations were performed to evaluate completely the effectiveness of these materials for use as landfill liner and to de- velop design charts for determining required liner thickness.

Homogenization of the transport behavior of nonlinearly adsorbing pollutants in physically and chemically heterogeneous aquifers

This paper addresses the question of how spatial variability in the hydraulic and chemical properties of groundwater systems affects the transport and sorption behavior of pollutants at the field scale. In this paper, we limit our investigations on pollutants that adsorb according to an equilibrium controlled nonlinear Freundlich sorption isotherm. The new contribution of this paper is take into account not only spatially variable Freundlich distribution coefficients K S but spatially variable Freundlich nonlinearity parameters p as well. Using a homogenization theory approach, we shortly review the impact of spatially variable hydraulic properties on the transport and extend the theory to spatially variable chemical properties. We show that spatially variable Freundlich exponents cause a very different field scale transport and sorption behavior than spatial variations in the distribution coefficients only since in the first case field scale Freundlich parameters and field scale dispersion coefficients become concentration dependent. In particular, field scale retardation is much larger than small-scale retardation.

The Study of Sorption of Toxic Basic Dyes from Aqueous Solutions on H2O 2 Treated Recycled Wool-based Nonwoven Material and Related Toxicity Analysis

The aim of this study was to investigate the potential use of recycled wool-based nonwoven material for removal of basic dyes C.I. Basic Yellow 28 and C.I. Basic Red 46 from aqueous solutions. To improve the sorption properties, the recycled wool-based nonwoven material was treated with hydrogen peroxide. The sorption capacity, the sorption kinetics, and the influence of initial dye concentration and pH on the sorption were studied. The acute toxicity of dyes was evaluated using a ToxAlert® 100 biological test, which is based on inhibition of the bioluminescence of Vibrio fischeri . The percent of inhibition ( %I) before and after the sorption, 50 % effective concentration ( EC50) and toxicity units ( TU) were determined. The results indicated that recycled wool-based nonwoven material can be used as an efficient sorbent for removal of investigated basic dyes. Hydrogen peroxide treatment considerably improved the sorption properties of the material for both dyes. The sorption kinetics of dyes on the hydrogen peroxide treated material obeyed pseudo-second order kinetic model. The Freundlich sorption isotherm was found to represent well the experimental sorption data. The increase of initial dye concentration and pH positively affected the sorption of basic dyes. An ion exchange mechanism of dye sorption was confirmed by desorption studies. The toxicity decreased after the sorption of both dyes.

Bioavailability and detoxification of cationics: I. Algal toxicity of alkyltrimethyl ammonium salts in the presence of suspended sediment and humic acid

We investigated the role of sorption in reducing bioavailability and consequently the measured toxicity of monoalkyl trimethyl ammonium salts (MAQ) under environmental conditions. The observed toxicity of MAQ in the presence of various types of sorbents was tested on algae. Decreased toxicity was found in the presence of all particulate sorbents tested, i.e. montmorillonite, silica, different sediments and for dissolved humic acid. Silica had a minor effect on the observed toxicity, whereas the clay mineral montmorillonite detoxified very effectively. The detoxification by several real-world sediments being mixtures of sand and clay was in-between silica and montmorillonite. Humic acid detoxified most effectively on weight basis. Polynomial relationships (‘QSARs’) were established for algal toxicity of MAQ in the presence of montmorillonite, silica and humic acid with carbon chain length as descriptor. Freundlich sorption isotherms for MAQ C16 for a clay sediment, montmorillonite, silica and for algae confirmed their relative detoxification in toxicity tests. Humic acid significantly reduced bioavailability and observed toxicity of quaternary ammonium salts. Sorption of positively charged amines to suspended sediment is effectively controlled by its silt/clay fraction, not by the organic fraction. Purchased defined quality montmorillonite can serve as model sorbent in standard tests mimicking the clay fraction of natural suspended matter. It enables to study the effect of bioavailability on toxicity in a standardised way. The QSARs developed for ecotoxicity of MAQ in the presence of suspended matter and humic acid enable quantitative incorporation of bioavailability in effect assessment. This increases realism in risk assessments of these fatty amine derivatives.

Synthesis and characterization of an analogue of heulandite: Sorption applications for thorium(IV), europium(III), samarium(II) and iron(III) recovery from aqueous waste

The synthesis of needle/fibrous particles of analogue of heulandite with particle diameter of 0.08 μm, length 4–8 μm and high specific surface area (478 m 2 g −1) with cation exchange capacity (3.27 mequiv g −1) have been achieved. The heulandite needles were obtained by using inorganic salts as a source for silicon and aluminum in the hydrothermal synthesis of the material. Alkalinity of the medium played an important role in the formation of heulandite fibers, as it affects the nucleation rate of zeolite synthesis. The analogue of heulandite was characterized using spectroscopic, thermal analysis, scanning and adsorption techniques. After mechanical grinding of crystals of heulandite, obtained powder was used for the study of radionuclide recovery from aqueous waste. The adsorption experiments were carried out under batch process with, pH of medium, amount of sorbent, time of contact between sorbate and sorbent, metal ion concentration and temperature as the variables. The adsorption was strongly dependent on pH of the medium and the uptake of all the metal ions increased from pH 1.0 to 9.0 and the maximum sorption was noticed in the pH range of 5.0–7.0. The optimum condition for these metal ions (Th(IV), Eu(III), Sm(II), and Fe(III)) sorption on self synthesized analogue of heulandite was; 0.001 N metal ion concentration, equilibration time of 4 h, 100 mg sorbent dose and 313–323 K temperature. This sorption process is fit to both Langmuir and Freundlich sorption isotherm. Thermodynamic studies predict the endothermic and spontaneous nature of the same.

Biosorption of bivalent metal ions from aqueous solution by an agricultural waste: Kinetics, thermodynamics and environmental effects

The ability of Neem oil cake (NOC), a bio-waste material to remove Cu(II) and Cd(II) ions from aqueous solution was investigated. The influence of pH, sorbent dose, concentration, temperature, and contact time on the sorption of Cu(II) and Cd(II) on NOC has been studied by batch process. The sorption was found to be maximum in acidic medium and increases with increase in initial concentration. Percent deviation ( P) and regression coefficient ( r 2) for Langmuir and Freundlich sorption isotherms shows better fitting of the models. Thermodynamics parameters indicate that the process is endothermic and spontaneous. Activation energies for Cu(II) and Cd(II) were calculated from Dubinin–Redushkevich (D–R) isotherms are high 8.3–8.7 and 7.17–11.4 kJ mol −1 showing that chemisorption is involved. The sorption kinetics was found to follow pseudo-second-order model.

Sorption and leaching of 14C-glyphosate in agricultural soils

Glyphosate (N-(phosphonomethyl)glycine) is one of the most widely used herbicides in the world to control weeds in agricultural and urban areas. Its increasing use requires special attention to its transfer from terrestrial to aquatic environments. However, knowledge on the leaching of glyphosate and its metabolite aminomethylphosphonic acid (AMPA) is scarce. Here we aimed to assess the dynamic interactions between glyphosate sorption and leaching; and to identify the main factors that influence the two processes in three undisturbed agricultural soils using microlysimeters under outdoor conditions. We studied the sorption, desorption and leaching of 14C-labelled glyphosate on three soils using batch experiments in the laboratory and lysimeters under natural conditions for 11 months. The laboratory results showed that glyphosate was strongly adsorbed, yielding empirical constants of Freundlich sorption isotherms (Kf) of 16.6 for the clay loam soil, 33.6 for the silt clay loam soil and 34.5 for the sandy loam soil, with nf close to 1 in all three cases. Glyphosate was also weakly desorbed, i.e. 5 to 24% (w) of initially sorbed glyphosate. Sorption and desorption were only pH-dependent. The outdoor results showed that nearly 70% of the initial glyphosate was present in the soil in a non-extractable form at the beginning of the experiment. Conversely, only less than 20% of the initial glyphosate is present in the soil in a non-extractable form after 11 months. These findings suggest that the non-extractable residues become available and take part in biodegradation and leaching. The amounts of 14C-glyphosate derivatives leached were less than 0.28% of the initially applied glyphosate. HPLC analyses showed that the AMPA metabolite generally represented up to 100% of the residues present in the leachates. The results of leaching were highly influenced by the hydrodynamic properties and the biodegradation capacities of the soils. Although glyphosate residues were found in low concentrations in the leachates for almost a year, the contamination of groundwater does not seem to be a concern, regardless of the soil type, if the herbicide is used in accordance with good agricultural practice.

Sorption and desorption characteristics of the dye tracer, Brilliant Blue FCF, in sandy and clay soils

Abstract Dye tracers are widely used for tracing and visualising hydrological flow paths in soils. Despite evidence of non-conservative behaviour (i.e. sorption) in recent years, Brilliant Blue FCF continues to be used extensively for dye tracing in soil. However, previous studies have not considered hysteresis in the sorption mechanism. The objectives of this study were (1) to test the hypothesis that sorption of Brilliant Blue FCF on soils with widely contrasting textures could be described with a single sorption isotherm based solely on sorption by the clay fraction and (2) to determine whether desorption hysteresis is likely to confound the estimation of retardation factor in modelling dye transit through soil. We measured the sorption and desorption of Brilliant Blue on four soils of contrasting texture, ranging from a light sand to a heavy clay, and resolved a single Freundlich sorption isotherm for the clay fraction in all soils. An attempt to include silt and humus fractions as additional adsorbents with independent Freundlich parameters was unsuccessful. The sorption of Brilliant Blue FCF on the four soils studied was not fully reversible; there was apparent sorption–desorption hysteresis in all cases. Therefore, even though the sorption strength of Brilliant Blue in soils might be less than that of other dye tracers, it is possible that the visualised flow pathways may not accurately reflect those of water in soil. From this we suggest that Brilliant Blue may not be well suited for all forms of dye tracing in clay soils and it is therefore crucial that the specific environmental conditions, soil type, dye concentration and objectives of the study are considered each time when choosing the appropriate dye tracer.

Synthesis and application of an analogue of mesolite for the removal of uranium(VI), thorium(IV), and europium(III) from aqueous waste

This work has been carried to investigate the sorption behavior of self synthesized analogue of mesolite, with respect to U(VI), Th(IV), and Eu(III), in order to consider its application for nuclear waste water treatment. The sorption experiments were performed under batch process with metal ion concentration, amount of mesolite, pH, time and temperature as variables. This paper also presents the experimental results concerning monolayer and multilayer sorption isotherm of metal ion on self synthesized mesolite analogue. The experimental results fit well in the Langmuir and Freundlich sorption isotherm models. These isotherms were found to be linear over the entire concentration range at different temperature studied with extremely high correlation coefficient values. The thermodynamic parameters: the enthalpy change, entropy change, and Gibbs free energy change for sorption process are in the range 10–35 kJ mol −1, 41–58 J mol −1 K −1, and −2 to −5 kJ mol −1, respectively. Desorption studies of metal ions have been carried out with a view to find out whether the metal ion sorbed by the exchanger is retained in the matrix for a sufficiently long period or it leached out from the matrix. Thus, the results reveal that the metal ions remain in the matrix of the sorbent for a longer period as no desorption of metal ions is observed with ground water. These studies present the suitability of mesolite for the removal of these selected radionuclides from aqueous waste. Apart from these studies, this paper also gives a detail description of mesolite synthesis and characterization.

Poly(methylmethacrylate) grafted chitosan: An efficient adsorbent for anionic azo dyes

Present study reports on peroxydisulfate/ascorbic acid initiated synthesis of Chitosan-graft-poly(methylmethacrylate) (Ch-g-PMMA) and its characterization by FTIR, XRD and 13C NMR. The copolymer remained water insoluble even under highly acidic conditions and was evaluated to be an efficient adsorbent for the three anionic azo dyes (Procion Yellow MX, Remazol Brilliant Violet and Reactive Blue H5G) over a wide pH range of 4–10 being most at pH 7. The adsorbent was also found efficient in decolorizing the textile industry wastewater and was much more efficient than the parent chitosan. Equilibrium sorption experiments were carried out at different pH and initial dye concentration values. The experimental equilibrium data for each adsorbent-dye system were successfully fitted to the Langmuir and Freundlich sorption isotherms. Based on Langmuir model Q max for yellow, violet and blue dyes was 250, 357 and 178, respectively. Thermodynamic parameters of the adsorption processes such as Δ G°, Δ H°, and Δ S° were calculated. The negative values of free energy reflected the spontaneous nature of adsorption. The adsorption kinetic data of all the three dyes could be well represented by pseudo-second-order model with the correlation coefficients ( R 2) being 0.9922, 0.9997 and 0.9862, for direct yellow, reactive violet and blue dye, respectively with rate constants 0.91 × 10 −4, 1.82 × 10 −4 and 1.05 × 10 −4 g mg −1 min −1, respectively. At pH 7, parent chitosan also showed pseudo-second-order kinetics. The temperature dependence of dye uptake and the pseudo-second-order kinetics of the adsorption indicated that chemisorption is the rate-limiting step that controls the process.

Factors Affecting on the Sorption/Desorption of Eu (III) using Activated Carbon

The sorption and desorption of Eu (III) on H‐APC activated carbon using a batch technique has been studied as a function of carbon type, shaking time, initial pH solution, temperature, particle size of carbon, and concentration of the adsorbent and the adsorbate. The influence of different anions and cations on adsorption has been examined. The experimental data have been analyzed by Langmuir, Freundlich, and Temkin sorption isotherm models and the adsorption data for Eu (III) onto activated carbon were better correlated to the Temkin isotherm and the maximum absorption capacities obtained was 46.5 mg g−1. Anions of phosphate, carbonate, oxalate, and acetate were found to increase the adsorption of Eu (III), whereas nitrate, chloride and all studied cations, potassium, sodium, calcium, magnesium, and aluminum have a negative effect on the adsorption capacity. More than 99% europium adsorbed on H‐APC eluted with 0.5 M HCl solution. The activated carbon prepared from apricot stone using 70% H3PO4 could be considered as an adsorbent that has a commercial potential for Eu (III) treatment.

Column studies on transport of deicing additive benzotriazole in a sandy aquifer and a zerovalent iron barrier

Benzotriazole (BTA), a chemical with wide industrial applications, is a typical additive in deicer/anti-icer used at airport. To achieve a better understanding of the transport behaviour and environmental fate of BTA, laboratory column studies have been performed on subsoil samples from Oslo Airport, Gardermoen. To explore possibilities for aquifer remediation, BTA behaviour was also studied in a column of granular zerovalent iron (Fe 0). The subsoil column study demonstrates a very limited retardation of BTA. Consecutive loadings of BTA of the subsoil column showed no change of the break-through curve (BTC) and complete desorption was observed. The sorption behaviour of BTA to metallic iron (Fe 0) was rather complex. Considerable retardation was observed in the Fe 0 column and repeated BTA loading resulted in an earlier break-through. Between 20% and 50% of the input concentration was retained permanently in the iron (Fe 0) column. The BTA sorption to metallic iron was found to be enhanced by chloride which lowered the break-through concentration (i.e the C/ C 0 plateau). The fraction of BTA remaining in the iron column was found to vary with the flow rate, indicating a time dependant multilayer sorption mechanism. The steady increase in the amount of adsorbed BTA to the iron column during loading corresponds to a rather strong bonding of 4–15 BTA layers to the iron surface. A very slow desorption of BTA was observed; even after flushing with 753 pore volumes of BTA free water, 7.5% of the BTA remained in the column. A geochemical model was developed based on PHREEQC-2 to simulate the sorption and transport of BTA in the tested materials. The BTA sorption was modelled with Freundlich sorption isotherms, as earlier determined in batch experiments. A slight adjustment of the Freundlich parameters was required to fit the observed column break-through. However, our model was not able to simulate the long-term retainment of BTA in the granular iron columns. The simulations confirm the high mobility of BTA in groundwater aquifers and suggest that zerovalent iron could be used to retain a BTA plume, although oxidation of the sorbent might reduce the long-term performance of such a remediation scheme and slow desorption has been observed.

A model describing the effect of enzymatic degradation on drug release from collagen minirods

A drug delivery system, named minirod, containing insoluble non-cross-linked collagen was prepared to investigate the release of model drug compounds. To characterise the complete drug release process properly, a mathematical model was developed. Previously, a mathematical model describing water penetration, matrix swelling and drug release by diffusion from dense collagen matrices has been introduced and tested. However, enzymatic matrix degradation influences the drug release as well. Based on experimental data, a model was developed which describes drug release by collagenolytic matrix degradation based on enzyme diffusion, adsorption and cleavage. Data for swelling, collagen degradation and FITC dextran release from insoluble equine collagen type I minirods were collected. Sorption studies demonstrated a tight sorption of collagenase on collagen surfaces that follows a Freundlich sorption isotherm and results in a degradation constant of 3.8 × 10 −5 mol/l for the minirods. The diffusion coefficients of FITC dextran 20 and 70 (3 × 10 −3 and 2.4 × 10 −3 cm 2/h) in water were analyzed by fluorescence correlation spectroscopy (FCS). Using these data, the mathematical model was verified by two-dimensional simulations. The numerical results agreed well with the measurements.