Removal Of Cephalexin Research Articles

Photocatalytic degradation of cephalexin by ZnO nanowires under simulated sunlight: Kinetics, influencing factors, and mechanisms

Increasing concentrations of anthropogenic antibiotics and their metabolites in aqueous environments has caused growing concerns over the proliferation of antibiotic resistance and potential adverse impacts to agro-environmental quality and human health. Photocatalysis using novel engineered nanomaterials such as ZnO nanowires may be promising for removing antibiotics from waters. However, much remains to be learned about efficiency and mechanism for photocatalytic degradation of antibiotics by ZnO nanowires. This study systematically investigated photodegradation of cephalexin using ZnO nanowires under simulated sunlight. The degradation efficiency of cephalexin was substantially increased in the presence of ZnO nanowires especially at circumneutral and alkaline condition (solution pH of 7.2–9.2). The photodegradation followed the first-order kinetics with degradation rate constants (k) ranging between 1.19 × 10−1 and 2.52 × 10−1 min−1 at 20–80 mg L−1 ZnO nanowires. Radical trapping experiments demonstrated that hydroxyl radicals (OH) and superoxide radicals (O2−) predominantly contributed to the removal of cephalexin. With the addition of HCO3− (1–5 mM) or Suwannee River natural organic matter (SRNOM, 2–10 mg L−1), the k values were substantially decreased by a factor of 1.8–70 to 1.69 × 10−3–6.67 × 10−2 min−1, probably due to screening effect of HCO3− or SRNOM sorbed on ZnO nanowires and scavenging of free radicals by free HCO3− or SRNOM in solution. Combining product identification by mass spectrometry and molecular computation, cephalexin photodegradation pathways were identified, including hydroxylation, demethylation, decarboxylation, and dealkylation. Overall, the novel ZnO nanowires have the potential to be used for removing antibiotics from contaminated waters.

Removalof Cephalexin From Aqueous Solutions Using Magnesium Oxide/Granular Activated Carbon Hybrid Photocatalytic Process

In the present study, magnesium oxide/granular activated carbon (MgO/GAC) composite as a catalyst was synthesized using the sol-gel method and its catalytic potential was investigated in the presence of ultraviolet (UV) irradiation for the removal of cephalexin (CLX) in a batch mode reactor. Then, the characterization of the MgO/GAC composite was determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Next, the effect of operational parameters was evaluated, including the pH of the solution (3-11), the dosage of composite (1-6 g/L), initial CLX concentration (20-100 mg/L), and contact time (10-60 minutes). The maximum CLX degradation with an initial concentration of 20 mg/L was as high as 98% at pH=3, 4 g/L of MgO/GAC composite with UV irradiation within 60-minute contact time. In addition, the removal process of CLX could be described by the pseudofirst-order kinetic. Further, the chemical oxygen demand (COD) and total organic carbon (TOC) removal rate were 78% and, 62.3% in optimum conditions, respectively. The results indicated that the UV/MgO/GAC hybrid photocatalytic process can be considered as an efficient alternative for treating the wastewater containing CLX.

Comparative study on the degradation of cephalexin by four electrochemical advanced oxidation processes: Evolution of oxidation intermediates and antimicrobial activity

The degradation of the β-lactam antibiotic cephalexin (CEX) was carried out by the following electrochemical advanced oxidation processes (EAOPs): anodic oxidation (AO), Fered-Fenton (EF-Fered), photoassisted anodic oxidation (PAO), and photoassisted Fered-Fenton (PEF-Fered). All experiments were done in a flow reactor incorporating a boron-doped diamond anode, at a low current density; for the PAO and PEF-Fered processes, the solution was irradiated with UVA light. The initial removal of CEX was attained by all EAOPs, but it was much faster by the Fenton-based processes, which thus presented higher initial rates of TOC removal. However, the coupling of the electrolytic and UVA photolytic processes enhanced the mineralization process; as a consequence, significantly greater TOC removals were attained by the PEF-Fered and PAO processes. From the initial oxidation intermediates detected by LC-MS/MS for the PEF-Fered and AO processes, it could be concluded that addition reactions involving the electrophilic HO∙ radicals occurred preferentially in the β-lactam ring; however, due to the higher availability of HO∙ radicals, the Fenton-based process led to a faster rupture of that ring. Thus, the antibacterial activity of the treated CEX solution against Escherichia coli was completely terminated within less than 1 h of treatment by the PEF-Fered process, compared to 8 h by the AO process. The PEF-Fered and PAO processes yielded enhanced degradation performances despite mere use of UVA light.

Removal of cephalexin from artificial wastewater by mesoporous silica materials using Box-Behnken response surface methodology

Removal of cephalexin from artificial wastewater by mesoporous silica materials using Box-Behnken response surface methodology

Photocatalysis assisted by activated-carbon-impregnated magnetite composite for removal of cephalexin from aqueous solution

The simultaneous presence of antibiotics and bacteria in aqueous media has been recognized as an environmental threat, due to the enhancement of antibiotic resistance of bacteria. We synthesized an activated carbon impregnated magnetite composite (PAC/Fe3O4) and used it for removal of cephalexin (CEX) from aqueous solution via UV system. A series of batch experiments was carried out under various experimental conditions such as pH of solution (3–11), contact time (0–120 min), catalyst dosages (0.1–2 g/L) and initial CEX concentrations (10, 25, 50 and 100 mg/L). Some common isotherm models were used for study of CEX adsorption and finding the best model. In addition, kinetic studies of CEX photocatalytic removal were performed by fitting the experimental data on first-order and second-order models. Results of comparative studies showed that UV+PAC/Fe3O4 and UV+TiO2 systems, compared to UV/Fe3O4, naked Fe3O4, PAC/Fe3O4 and UV only, had more capability of removing CEX from aqueous solution, indicating PAC/Fe3O4 is effectively catalyzed by UV light. Furthermore, increasing catalyst dosages and decreasing initial CEX concentrations led to the enhancing photocatalytic removal of CEX from solution. The obtained results of kinetic studies also represent that among the studied models, second-order model with significant coefficient of correlation (R2) had higher ability than first-order model to fit the data of CEX removal. Finally, the findings of reusability tests, showed that the applied catalyst would be applicable for CEX removal, even after five consecutive cycles.

Pilot-scale single-step reactor combining photocatalysis and photo-Fenton aiming at faster removal of Cephalexin

Abstract A solar pilot-scale cascade reactor system with novel Fe TiO2 composite beads possessing unusual characteristics of in-situ dual effect i.e. coupling of photocatalysis and photo-Fenton has been investigated in once-through mode. The cascade arrangement of packed-bed reactors maintained sufficient turbulence in the system besides eliminating the implications of film-diffusion resistance. The synergistic effect (10%) of in-situ dual process over individual processes has significantly reduced the treatment time of a recalcitrant antibiotic, Cephalexin (CEX). The reaction performance of the once-through cascade reactor system (comprising of six packed-bed reactors in series) incorporating in-situ dual effect at optimized conditions i.e. H2O2: 600 mgL−1, flow rate: 50 mLmin-1, with a space time (Ʈ) of 12 min approached to that of plug-flow reactor (PFR). The mineralization of CEX was evaluated through reduction in COD (70%) and TOC (63%) along with generation of anions and evolution of CO2. The treated solution of CEX was completely non-toxic as confirmed through Kirby-Bauer test and bio-assay analysis based on toxicity factor. In addition to this, Fe TiO2 composite beads depicted an excellent recyclability efficiency (>70 recycles) even under continuous flow conditions as confirmed through SEM/EDS, DRS, XRD, XPS and TGA analysis. The overall cost of treatment process was evaluated in detail to visualize the practical feasibility of the presented high performance reactor system.

Application of ZnO and TiO2 nanoparticles coated onto montmorillonite in the presence of H2O2 for efficient removal of cephalexin from aqueous solutions

This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO2 (TiO2/GLM) in the presence of H2O2. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔG o and ΔH o revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO2/GLM, respectively. Temkin constant (B T ) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.

Photocatalytic Removal of Cephalexin by UV/ZnO Process from Aqueous Solutions

Background and Objectives: Conventional wastewater treatment plants are not able to remove effective drugs, such as antibiotics, so eliminating remaining antibiotics from the environment is important. The purpose of this study was to evaluate the efficacy of UV / ZnO photocatalytic process in removing antibiotic cephalexin from aqueous solutions. Materials and Methods: This is an experimental-applied study that was performed on a batch scale in a laboratory scale. The variables studied in this study included the initial pH of the solution (11, 9, 7, 5, 3), the dose of nanoparticles (1, 75/0, 0.5, 0.25, 0.1, 0.05 grams per liter), Reaction time (60-50-40-30-20-15-55 minutes) and initial concentration of pollutant (100, 50, 25, 10 mg / l) were investigated. Measurement of cephalexin in samples was performed using HPLC apparatus. Results: The results showed that by decreasing pH and reducing the initial concentration of cephalexin and increasing contact time, process efficiency increased. But with increasing nanoparticle dosages up to 0.1 grams per liter, the process efficiency increases and more than this amount is reduced. Conclusion: The results of this study showed that the use of UV / ZnO photocatalytic process in removing humic acid from aqueous solutions can be used as an effective method for cephalexin from aqueous solutions.

Bioremediation of Cephalexin with non-living Chlorella sp., biomass after lipid extraction

In this work, the removal of the Cephalexin by Chlorella sp., nonliving modified by extraction of lipids was evaluated. First, the microalga was grown to completing 20 days and later, the biomass of crop was centrifuged and the extraction of lipids was performed. Two adsorption experiments were performed: (1) with nonliving Chlorella sp. (control), and (2) the obtained biomass after lipid extraction. The high antibiotic removal, 71.19% and 82.77% (control), were obtained at the lowest initial concentration. The contact time between the biosorbent and the antibiotic was 2 h. The adsorption isotherm follows the Freundlich model and the obtained maximum absorption capacity was 63.29 mg of antibiotic/g of biosorbent for lipid-extracted biomass, while the control follows best to the Langmuir model with 129.87 mg/g in maximum absorption capacity. In summary, this biosorbent provides a potential alternative in the removal of Cephalexin.

Assessment of integrated binary process by coupling photocatalysis and photo-Fenton for the removal of cephalexin from aqueous solution

A novel concept of integrated process by coupling photocatalysis and photo-Fenton especially in fixed mode has been presented in the current study for the removal of recalcitrant pharmaceuticals like cephalexin (CEX) from aqueous solution in reduced treatment time. Waste materials like foundry sand (FS) was used as a substitute for iron along with TiO2. The parametric optimization was carried out in slurry mode using Box–Behnken design model (BBD) and response surface methodology. For fixed-bed studies, support materials of varying shapes (hollow circular disk, rectangular slabs, spherical beads) were prepared using clay in conjunction with FS for TiO2 immobilization. Different supports were compared on the basis of degradation efficiency, exposed surface area of catalyst as well as their recyclability capacity for the degradation of CEX. Iron was leaching by default from the supports during the degradation process which contributed simultaneously to photo-Fenton process along with photocatalysis. Spherical beads with 0.0265 m2 exposed surface area of catalyst and better recyclability efficiency (10 cycles) yielded best degradation efficiency (80%) of CEX after 240 min of treatment time. The presence of iron along with TiO2 on the surface of beads was confirmed through TGA, SEM/EDS, XRD, DRS and FTIR. The mineralization of CEX was validated through quantification of nitrite, nitrate and sulfate ions along with reduction in COD. A tentative pathway for the degradation of CEX was also proposed based on the identification of intermediates through GC–MS analysis.

Effects of Cu and CuO on the preparation of activated carbon from waste circuit boards by H3PO4 activation

In order to study the effects of Cu and CuO on the activated carbon synthesized from waste circuit boards, we choose non-metal part without metal as the precursor, H3PO4 as the activating agent, Cu and CuO were added in the preparation process respectively. One was only activated by H3PO4, one was activated by H3PO4 and Cu powder, and another was activated by H3PO4 and CuO powder, which were named AC, AC/Cu and AC/CuO, respectively. Thermo-gravimetric analysis detected that the introduction of Cu and CuO powder into the activation process accelerated the decomposition of organic matter in the precursor. The BET surface area followed an order of AC/CuO>AC/Cu>AC. Compared with AC, the graphitization degree of AC/Cu and AC/CuO decreased, the amorphous carbon content increased, implying the introduction of Cu and CuO powder changed the activation reaction process. For these three adsorbents, the Langmuir model was better to describe the equilibrium data with a higher R2 value. The maximal adsorption capacity followed an order of AC/CuO>AC/Cu>AC. Besides, the adsorptions of cephalexin (CEX) on these three adsorbents were dependent on pH values. The adsorption-regeneration cycle experiment showed they were stable for CEX removal. The characterization and adsorption experiment proved the introduction of Cu and CuO could improve the properties of activated carbon. The results of cost analysis suggested these three adsorbents were practical for producing activated carbons.

Green synthesis of nano-zero-valent iron from Nettle and Thyme leaf extracts and their application for the removal of cephalexin antibiotic from aqueous solutions

ABSTRACTIn this study, the removal of cephalexin (CEX) antibiotic from aqueous solution was examined using a novel green adsorbent without employing any toxic chemicals or capping agents. Nettle and Thyme extracts were used to synthesize novel nano-zero-valent iron (NNZVI and TNZVI) for the adsorption of CEX. The nature and morphology of synthesized adsorbent were characterized by Transmission electron microscopy, scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscopy spectroscopy. Batch experiments were performed to study the influence of various experimental parameters such as contact time, initial concentration of the CEX, solution pH and adsorbent dosage. The adsorption isotherms of CEX by NNZVI and TNZVI were found to fit well with Freundlich and Langmuir models, respectively. The maximum adsorption capacity of CEX onto NNZVI and TNZVI were observed as 1667 and 1428 mg/g, respectively, based on the Langmuir model. The adsorption trend followed the pseudo-first-order kinetics model and equilibrium could be established in about two hours for both adsorbents. The developed nanoparticles in this study have considerable potential for the removal of CEX and could be considered as a promising adsorbent for the removal of other antibiotics also from aqueous solutions.

Modified biochar supported Ag/Fe nanoparticles used for removal of cephalexin in solution: Characterization, kinetics and mechanisms

The environmental risks caused by residual antibiotics have attracted great attention. In this study, a new method was performed using modified biochar supported Ag/Fe nanoparticles (Ag/Fe/MB) to remove cephalexin (CLX) in aqueous solution. More than 86% of CLX was removed by Ag/Fe/MB in 90min under the simultaneous action of adsorption and reduction (dose: 1.5g/L, CLX initial concentration: 20mg/L, pH: 6.15). Notably, the adsorption was more prevalent than the reduction during the removal of CLX. The results of scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) of Ag/Fe/MB confirmed the presence of Ag/Fe nanoparticles and a good distribution on the surface of support matrix. Removal of CLX was seriously dependent on adsorbate concentration and pH. The presence of citric acid (CA) strongly increased the removal of CLX, where the initial reaction rate was increased by 36.03 times. Degradation products of CLX, generated by removing functional groups from the structure of CLX, were analyzed by liquid chromatography–mass spectrometry (LC–MS) to investigate the degradation pathway.

Sonolytic and photocatalytic (sonophotocatalytic) removal of cephalexin from aqueous solution: process optimization using response surface methodology (RSM)

Extensive use of pharmaceutical drugs has resulted in widespread use of antibiotic remedies in the environment and consequently has made a strong public concern worldwide. Present study aimed at assessing the possible effects of combined ultrasound (sonolysis) and UV/ZnO and UV/WO3 photocatalytic processes on the removal of cephalexin from aqueous solutions. A pilot-scale Plexiglas reactor with working volume of 1 L was used in this study. A constant frequency of 40 Hz was used in ultrasound processes. Effects of various experimental parameters on sonophotocatalytic degradation were investigated. These included 200–400 mg/L of ZnO, 100–200 mg/L of WO3, contact time of 60–120 min and cephalexin concentration of 50–100 mg/L. Response surface methodology was applied in the experimental design. Results showed that sonolytic degradation was not significantly effective and the maximum degradation rate reached 19.3. The maximum photocatalytic removal of UV/ZnO and UV/WO3 reached 66.5 and 78.6, respectively. The effect of cephalexin concentration on the efficiency of processes was negative, but contact time and catalytic dosage had direct effects on the process. This was carried out under optimal conditions, including antibiotic concentration of 50 mg/L, contact time of 120 min, 400 mg/L of ZnO and 200 mg/L of WO3. The ratio of BOD5/COD was calculated 0.31 and it ranged from 0 to 0.24 using UV/WO3 and UV/ZnO, respectively. The models of cephalexin removal from photocatalytic processes were quadratic (R2 = 0.966–0.982). Results revealed that successful combination of sonolytic and photocatalytic (sonophotocatalytic) treatments can strongly remove cephalexin from aqueous solutions. © 2017 Desalination Publications. All rights reserved.

Kinetic study and modelling of cephalexin removal from aqueous solution by advanced oxidation processes through artificial neural networks

Kinetic study and modelling of cephalexin removal from aqueous solution by advanced oxidation processes through artificial neural networks

Potential of bacterial consortium for removal of cephalexin from aqueous solution

Antibiotics represent a global environmental problem due to their role in the increasing of antimicrobial resistance. Therefore, the removal of antibiotics from wastewater has received unrivalled attention in the recent years. Several technologies including the biodegradation process have been applied for this purpose. However, the potential of bacterial biomass in the biosorption of antibiotics has limited studies. The present study investigated cephalexin removal from aqueous solution by consortium bacterial cells (living and dead) which are tolerant for antibiotics. The factors including cephalexin, biomass, pH, temperature as well as presence of heavy metal ions were tested. The maximum biosorption efficiency was recorded at 0.4mgL−1 (94.73% vs. 92.98% for living and dead cells respectively), dead cells exhibited more efficiency compared to living cells at 5mgL−1 (82.36% vs. 46.66% respectively). Living cells are more effective at pH value between pH 4 and 6 (71.95–68.90%). The maximum removal of living cells was highest at 30°C (80.26%), while was at 25°C of dead cell biomass (63.81%). Remarkable percentage for cephalexin biosorption by living cells was recorded in the presence low concentrations of Ni2+ (0.21mgL−1, 40% vs. 30% of living and dead cells, respectively). Living cells exhibited 27.42% and 25% of the removal with Cu2+ (1mgL−1) and Pb2+ (0.4mgL−1) respectively. In conclusion the bacterial cells biomass has a potential to remove cephalexin with some negative effects of heavy metals which can be overcome by the removal of these metal ions first and then removal of antibiotics in a second cycle.

Removal of cephalexin from effluent by activated carbon prepared from alligator weed: Kinetics, isotherms, and thermodynamic analyses

Abstract Low-cost activated carbon was produced from alligator weed by phosphoric acid activation. The cost of production of alligator weed-activated carbon (AWAC) was CN¥ 2.1/kg and the content of activated carbon (AC) in AWAC was 35.33%. AWAC was used as an adsorbent to adsorb cephalexin (CEX) from aqueous solution. Scanning electron microscopy (SEM) analysis of AWAC revealed a highly porous structure with a rough surface. AWAC featured a high surface area of 736.3 m 2 /g and an average pore size of 4.05 nm, which were responsible for its excellent adsorption ability. The maximum CEX adsorption capacity of AWAC was ∼45 mg/g. The Langmuir isotherm ( R 2 = 0.9967) gave the best correlation with the experimental data at 308 K, indicating monolayer adsorption. The kinetic model data on AWAC fit well to the pseudo-second-order kinetic equation, which is considered as the rate-limiting factor. Fourier transform infrared spectroscopy analysis revealed the presence of phosphorus-containing groups and C–H, C–O, and C=C moieties on the surface of AWAC. Following adsorption, the intensity of the spectral peaks of AWAC decreased owing to coverage of the CEX species or reaction with the functional groups of CEX.

Aqueous phase adsorption of cephalexin by walnut shell-based activated carbon: A fixed-bed column study

The walnut shell was used as a low cost adsorbent to produce activated carbon (AC) for the removal of cephalexin (CFX) from aqueous solution. A fixed-bed column adsorption was carried out using the walnut shell AC. The effect of various parameters like bed height (1.5, 2 and 2.5cm), flow rate (4.5, 6 and 7.5mL/min) and initial CFX concentration (50, 100 and 150mg/L) on the breakthrough characteristics of the adsorption system was investigated at optimum pH 6.5. The highest bed capacity of 211.78mg/g was obtained using 100mg/L inlet drug concentration, 2cm bed height and 4.5mL/min flow rate. Three kinetic models, namely Adam’s–Bohart, Thomas and Yoon–Nelson were applied for analysis of experimental data. The Thomas and Yoon–Nelson models were appropriate for walnut shell AC column design under various conditions. The experimental adsorption capacity values were fitted to the Bangham and intra-particle diffusion models in order to propose adsorption mechanisms. The effect of temperature on the degradation of CFX was also studied.

Improvement of zeolite adsorption capacity for cephalexin by coating with magnetic Fe3O4 nanoparticles

The removal of cephalexin (CEX) from aqueous solution by natural zeolite (NZ) and magnetic Fe3O4 nanoparticles prepared and coated onto natural zeolite (CZ) was investigated. Magnetic Fe3O4 nanoparticles were synthesized by chemical precipitation of a Fe2+ and Fe3+ salts from aqueous solution by ammonia hydroxide solution. SEM images, XRD patterns, XRF spectroscopy, and FTIR spectroscopy were used to characterize the adsorbents. The maximum CEX removal efficiency was 28% and 93% for NZ and CZ, respectively, at optimized condition (pH7, an amount of adsorbent of 0.6g/L, a concentration of CEX of 40mg/L, contact time of 2h, and a temperature of 20°C). The isotherm adsorption of CEX onto both adsorbents was best fitted with Langmuir isotherm equation and the maximum adsorption capacity was 16.1 and 24.9mg/g for NZ and CZ, respectively. The kinetics followed is second order in nature and the intraparticle diffusion was the dominating mechanism. Thermodynamic parameters (∆G°>0 and ∆H°<0) showed the non-spontaneity and exothermic in nature of adsorption process. However, the results showed that the increasing of nitrate, carbonate, and hardness ions decreased the CEX removal efficiency by different trends but their effect can be ranked as nitrate<carbonate<hardness.

Adsorption of cephalexin from aqueous solution using natural zeolite and zeolite coated with manganese oxide nanoparticles

In the present study the adsorption of Cephalexin (CEX) from aqueous solution using natural zeolite (NZ) and zeolite coated with manganese oxide nanoparticles (CZ) were investigated as a function of pH, shaking time, initial CEX concentrations, adsorbent dose, and competitive ions. Scanning electron microscope (SEM) images, X-ray diffraction (XRD) patterns, X-ray fluorescence (XRF) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy were used to characterize the adsorbents. The maximum CEX removal efficiency was 28% and 89% for NZ and CZ, respectively, at pH7. The experimental isotherm data were analyzed by Freundlich, Langmuir, Redlich–Peterson, and Sips models. The results showed that Sips isotherm was the best model and the maximum adsorption capacity went from 16.1mg/g for the NZ to 24.5mg/g for the CZ, for 2g/L adsorbent dose. Comparison of these results with those obtained from previous literature suggested that CZ can be potentially used for CEX removal from aqueous solution. The kinetics of CEX adsorption with different initial concentrations were better fit by the pseudo-second-order model, with higher coefficient of determinations and more closely predicted uptake. Finally, the results showed that the intraparticle diffusion was the dominating mechanism.