Comparison of trace metal adsorption onto different solid materials and their chemical components in a natural aquatic environment

Solid materials such as suspended particulate matter (SPM), deposited sediment (DS) and natural surface coatings (NSC, composed of biofilms and associated minerals) are important sinks and potential sources of pollutants in natural aquatic environments. Although these materials can exist in the same water body, few studies have been conducted to compare their ability to adsorb trace metals. In this study, the adsorption of Pb, Cu and Cd by these solids, collected from an urban lake, was investigated. In addition, the metal adsorption properties of the main components of these solids, namely Mn and Fe oxides and organics, were also investigated using the method of selective extraction followed by metal adsorption. The solids that co-existed in water showed similarities and differences in their compositions. For each metal, adsorption to the solids occurred in the same order: NSC > SPM > DS. For Pb and Cd, Fe and Mn oxides and organics contributed to the adsorption by NSC and SPM, and the adsorption by DS was dominated by Fe oxides. For Cu, the organics were the main adsorptive phase. The specific adsorption capability of these components decreases in the following order: Mn oxides > Fe oxides > organics. Overall, the results presented herein indicate that different solids and their components played important roles in the adsorption of trace metals.     

Uranyl adsorption onto montmorillonite: Evaluation of binding sites and carbonate complexation

The fate and transport of uranium in contaminated soils and sediments may be affected by adsorption onto the surface of minerals such as montmorillonite. Extended X-ray absorption fine structure (EXAFS) spectroscopy has been used to investigate the adsorption of uranyl (UO₂²⁺) onto Wyoming montmorillonite. At low pH (∼4) and low ionic strength (10⁻³ M), uranyl has an EXAFS spectrum indistinguishable from the aqueous uranyl cation, indicating binding via cation exchange. At near-neutral pH (∼7) and high ionic strength (1 M), the equatorial oxygen shell of uranyl is split, indicating inner-sphere binding to edge sites. Linear-combination fitting of the spectra of samples reacted under conditions where both types of binding are possible reveals that cation exchange at low ionic strengths on SWy-2 may be more important than predicted by past surface complexation models of U(VI) adsorption on related montmorillonites. Analysis of the binding site on the edges of montmorillonite suggests that U(VI) sorbs preferentially to [Fe(O,OH)₆] octahedral sites over [Al(O,OH)₆] sites. When bound to edge sites, U(VI) occurs as uranyl-carbonato ternary surface complexes in systems equilibrated with atmospheric CO₂. Polymeric surface complexes were not observed under any of the conditions studied. Current surface complexation models of uranyl sorption on clay minerals may need to be reevaluated to account for the possible increased importance of cation exchange reactions at low ionic strengths, the presence of reactive octahedral iron surface sites, and the formation of uranyl-carbonato ternary surface complexes. Considering the adsorption mechanisms observed in this study, future studies of U(VI) transport in the environment should consider how uranium retardation will be affected by changes in key solution parameters, such as pH, ionic strength, exchangeable cation composition, and the presence or absence of CO₂.     

Experimental study on the competitive adsorption of metal ions onto minerals

The study on the competitive adsorption shows that the magnitude order of metal ions adsorbed onto oxide and silicate minerals in near-neutral solution with low ionic strength is in mole/nm² as follows: CaCO₃ > quarte > hydromuscovite > kaolinite > Ca-montmorillonite > goethite > gibbsite. These minerals can be divided into three groups according to their surface equilibrium constantsK _M of the adsorption reactions, which are the function of the dielectric constants ε of the absorbent minerals. The relationships between constantsK _M and mineral dielectric constants ε are described as follows: lgK _M ¹ = 7.813-26.15/ε lgK _M ² = 9.030-26.15/ε lgK _M ³ =11.63-26.15/ε for the adsorption reaction: >SO^- + Mⁿ⁺≥SOM^n-1)+ (n = 1, 2, 3) The first group of minerals include quartz, goethite, 1:1 phyllosilicates and other oxide minerals; the second: gibbsite, brucite and 2:1 phyllosilicates; the third: carbonate, sulphate and phosphorate minerals. The appearance reaction constants have a variation of magnitude ±0.5 for different metal ions with the same mineral. This project was financially supported by the National Natural Science Foundation of China (No. 49572091).     

Influence of operating conditions on the removal of Cu, Zn, Cd and Pb ions from wastewater by adsorption

Nile Rose Plant was used to study adsorption of several cations (Cu²+, Zn²+, Cd²+ and Pb²+) from wastewater within various experimental conditions. The dried leaves of Nile Rose Plant were used at different adsorbent/ metal ion ratios. The influence of pH, contact time, metal concentration, and adsorbent loading weight on the removal process was investigated. Batch adsorption studies were carried out at room temperature. The adsorption efficiencies were found to be pH dependent, increasing by increasing the pH in the range from 2.5 to 8.5 exept for Pb. The equilibrium time was attained within 60 to 90 min. and the maximum removal percentage was achieved at an adsorbent loading weight of 1.5 g/50 mL mixed ions solution. Isothermal studies showed that the data were best fitted to the Temkin isotherm model. The removal order was found to be Pb²⁺> Zn²⁺> Cu²⁺> Cd²⁺. The surface IR-characterization of Nile rose plant showed the presence of many functional groups capable of binding to the metal cations.     

The adsorption of polysaccharides onto mineral surfaces: an acid/base interaction

Natural polysaccharides such as starch, dextrin, guar gum, cellulose and their derivatives are promising non-toxic organic depressants. Although generally perceived as non-selective, these polymers have found use in commercial processes or have been tested in laboratories in practically all flotation systems involving every type of minerals. In this communication, the adsorption mechanisms of natural polysaccharides are reviewed, with the objective of promoting the wider applications of the polymers. While it seems generally accepted that natural polysaccharides interact with minerals via surface metal-hydroxylated species, an acid/base interaction model between the natural polysaccharides and mineral surfaces is proposed to explain many observed adsorption and flotation phenomena.     

Experimental study of the selective adsorption of heavy metals onto clay minerals

The interaction between minerals and heavy metals has been a hot object of study in environmental science,mineralogy and soil science,Through the selective adsorption experiment of Ca-montomorillonite,illite and kaolinite to Cu2 ,Pb^2 ,Zn^2 ,Cd^2 ,and Cr^3 ions at certain conditions,it could be concluded that Cr^3 is most effectively sorbed by all the three minerals.Also,it can be found that Pb^2 shows a strong affinity for illite and kaolinite while cu^2 for montmorillonite .Based on the adsorption experiment at varying pH of solution,it can be found that the amount of heavy etals sorbed by minerals increases with increasing pH of the solution.     

Competitive adsorption of metal cations onto two gram positive bacteria: testing the chemical equilibrium model

In order to test the ability of a surface complexation approach to account for metal-bacteria interactions in near surface fluid-rock systems, we have conducted experiments that measure the extent of adsorption in mixed metal, mixed bacteria systems. This study tests the surface complexation approach by comparing estimated extents of adsorption based on surface complexation modeling to those we observed in the experimental systems. The batch adsorption experiments involved Ca, Cd, Cu, and Pb adsorption onto the surfaces of 2 g positive bacteria: Bacillus subtilis and Bacillus licheniformis. Three types of experiments were performed: 1. Single metal (Ca, Cu, Pb) adsorption onto a mixture of B. licheniformis and B. subtilis; 2. mixed metal (Cd, Cu, and Pb; Ca and Cd) adsorption onto either B. subtilis or B. licheniformis; and 3. mixed or single metal adsorption onto B. subtilis and B. licheniformis. %Independent of the experimental results, and based on the site specific stability constants for Ca, Cd, Cu, and Pb interactions with the carboxyl and phosphate sites on B. licheniformis and B. subtilis determined by Fein et al. (1997), by Daughney et al. (1998) and in this study, we estimate the extent of adsorption that is expected in the above experimental systems.Competitive cation adsorption experiments in both single and double bacteria systems exhibit little adsorption at pH values less than 4. With increasing pH above 4.0, the extent of Ca, Cu, Pb and Cd adsorption also increases due to the increased deprotonation of bacterial surface functional groups. In all cases studied, the estimated adsorption behavior is in excellent agreement with the observations, with only slight differences that were within the uncertainties of the estimation and experimental procedures. Therefore, the results indicate that the use of chemical equilibrium modeling of aqueous metal adsorption onto bacterial surfaces yields accurate predictions of the distribution of metals in complex multicomponent systems.     

坡缕石对Zn^2＋的吸附性能及吸附工艺条件优化研究

从坡缕石粘土提纯人手，进行了坡缕石吸附Zn^2 的实验研究，结果表明坡缕石对水中Zn^2 的吸附性能主要受振荡速度、吸附时间、溶液pH值、吸附剂用量等因素影响，30℃时坡缕石对Zn^2 的等温吸附曲线同时符合Langmuir方程和BET方程。在本实验条件下，坡缕石对水中的Zn^2 (20mL，Zn^2 浓度均为50mg／L)的最佳吸附工艺条件为：振荡速度150r／min，吸附时间120min，吸附剂用量0．120g，溶液pH为6．2，此条件下去除率达到T95．5％。     

Effect of contact time,pH, and ionic strength on Cd(II) adsorption from aqueous solution onto bentonite from Gaomiaozi,China

Copper smelting and toxic emissions in Sarcheshmeh Copper Complex have resulted in soil pollution especially in the vicinity of the smelting plant. Calculated geoaccumulation index, contamination factor (C _f), and contamination degree (C _deg) indicate surface soil enrichment in potentially toxic metals (As, Cu, Pb, Zn, Mo, and Cd). The results also indicate that most contaminated areas are located in the prevailing wind directions (N and NE). However, continuous copper smelting can result in extensive pollution in the study area. This is especially alarming for adjacent townships. Since, the sampled sites are also used as grazing land, the soils are likely to become phytotoxic and provide a potential pathway for the toxic elements to enter the food chain. C _f based on distance and direction give more reasonable results; that is, the decrease of contamination degree with distance. This is in agreement with I _geo and also statistical analysis, which show a decreasing trend of metal loadings of soil with distance from the smelter. Statistical analysis reaffirms the polluting role of the smelting plant.     

温度对煤吸附甲烷的影响实验

为了研究温度对煤吸附甲烷的影响,实验测定了不同温度下煤对甲烷的吸附等温线,并对实验数据进行了拟合,同时对覆盖度与压力、温度、吸附量以及孔隙类型的关系进行了分析。结果表明:随着温度的增高,饱和吸附量和吸附速率明显降低,并且含气量与覆盖度呈正相关关系;同一压力下,随着温度升高,覆盖度降低;相对覆盖度概念可以解释高温覆盖度高而吸附量小于低温阶段的现象;结合孔隙度和液氮分析结果发现,随着温度的增高,小孔和微孔的吸附能力强于中孔和大孔;甲烷在煤上的等量吸附热随吸附量的增大而增大,但无规律可循,且由Clausius-Clapeyron方程预测出的等温吸附曲线与实测值有偏差,表明煤表面能量的不均匀性和表面离子的复杂性。     

Influence of hydroxybenzoic acids on the adsorption of Eu(III) onto α,γ-Al2O3 particles in mildly acidic conditions: A macroscopic and spectroscopic study

The influence of hydroxybenzoic acids (HAH_n), namely p-hydroxybenzoic acid (4-hydroxybenzoic acid, HPhbH) and protocatechuic acid (3,4-dihydroxybenzoic acid, HProtoH₂), on the adsorption of europium(III) onto α,γ-Al₂O₃ particles is studied as a function of acid concentration. After measuring the adsorption edge of the Eu(III)/α,γ-Al₂O₃ binary system, and using the previously studied binary component system Eu(III)/HAH_n—Moreau et al. (2015) Inorg. Chim. Acta 432, 81—, and HAH_n/α,γ-Al₂O₃—Moreau et al. (2013) Colloids Surf. A 435, 97—, it is evidenced that HPhbH does not enhance Eu(III) adsorption onto α,γ-Al₂O₃ in the Eu(III)/HPhbH/α,γ-Al₂O₃ ternary system. Conversely, HProtoH₂ enhances Eu(III) adsorption onto α,γ-Al₂O₃ in the Eu(III)/HProtoH₂/α,γ-Al₂O₃ ternary system. Adsorption of the acids are also found higher in the Eu(III)/acid/α,γ-Al₂O₃ ternary systems as compared with the corresponding binary systems assessing synergetic effects. For high HPhbH concentrations, a ternary surface species involving ≡AlOH surface sites, Eu(III), and PhbH^– is evidenced by time-resolved luminescence spectroscopy (TRLS). However, in the Eu(III)/HProtoH₂/α,γ-Al₂O₃ ternary system, chemical environment of Eu(III) is found to be very close to that in the Eu(III)/HProtoH₂ binary system. Ternary surface species could not be evidenced in the Eu(III)/HProtoH₂/α,γ-Al₂O₃ ternary system with TRLS because of the very short decay time of Eu(III) in the presence of protocatechuic acid.     

A study on the adsorption characteristics of cadmium and zinc onto acidic and alkaline soils

The adsorption of cadmium (Cd) and zinc (Zn) with similar chemical properties is examined onto three soil samples: one is alkaline and the others are acidic. The distribution coefficient (K _d) and the Freundlich constant (K _F) for Zn are slightly higher than those for Cd, implying that the adsorption affinity of Zn is a little greater and less mobile. However, Cd and Zn usually show comparable results in the kinetic, isotherm, and envelope experiments. The adsorption of the heavy metals is relatively rapid and the reaction is almost completed within 15 min. The kinetics for both Cd and Zn are very well explained by the parabolic diffusion model. The maximum adsorption of the heavy metals is obtained at high pH, high temperature, and low ionic strength. The adsorption capacity on the alkaline soil is more significantly affected by the temperature as compared to the acidic soil. It is found that the adsorption affinity of the two heavy metals is mainly affected by the soil properties, such as pH, pH_PZC, organic matter, and total carbon. It is also confirmed that the chemical properties of the heavy metals are important factors in their adsorption onto soil. The adsorption isotherms of Cd and Zn are well described in both Freundlich and Langmuir models at the usual pH (soil pH). Under acidic and alkaline pHs, however, only the Freundlich model describes the adsorption of both heavy metals satisfactorily.     

Effective parameters for the adsorption of chromium(III) onto iron oxide magnetic nanoparticle

Most of the industrial wastewaters comprise toxic, biologically non-biodegradable, and heavy metals which tend to accumulate in the biological organisms causing different diseases. There are some novel technologies and strategies to remove these pollutants. Using the magnetic nanoparticles which are cheap, recyclable, and reusable can be considered as an effective method for removing the pollutants as they do not require conservation or complicated equipments. Using this method, dangerous and rare heavy metals can be restored to the industry. In this study, magnetic nanoparticles with the size of 30 nm were prepared and used for the removal of chromium from synthetic wastewater polluted by chromium sulfate. For this purpose, removal of various concentrations of chromium(III) from wastewater was investigated. The best concentration was achieved in the removal efficiency of 99.1 %. The optimal values of pH, rotation speed of magnetic stirrer, time, temperature, and the amount of nanoparticles were determined according to the primary concentration (500 mg/L). The mechanism of chromium adsorption onto iron oxide (Fe₃O₄) magnetic nanoadsorbent was also investigated. The results showed both Freundlich and Longmuir isotherms to be the best fit for the chromium adsorption, with Freundlich isotherm being more suitable.     

气体吸附对煤层安全钻井液密度的影响

煤岩中割理极为发育,导致煤层非均质性极强,在煤层钻井过程中井壁极易垮塌,掩埋钻具,钻井过程中配置合理的钻井液用以保持井壁稳定具有重要的意义。现阶段主要是运用经典连续介质理论模型进行钻井过程中安全钻井液密度窗口预测,导致现场实际效果较差。实际煤层不仅割理发育并且大量CH₄以吸附态赋存于煤层中,将弱化煤岩力学强度,使原本就易失稳的井壁越加不稳定。因此,针对煤层为非连续介质的特殊性,基于非连续介质力学构建的离散元模型分析钻井过程中煤层井壁稳定性,并结合连续介质强度分析法在考虑气体吸附对煤岩力学强度弱化影响的情况下,用以确定煤层最佳防塌钻井液。最后,根据山西省宁武盆地的煤岩数据及现场钻井液资料,利用上述理论进行实例计算,指出研究区煤层防塌需保证钻井液密度大于1.009 g/cm³,并且需在钻井液中添加暂堵剂以提高其封堵能力。     

Effects of common groundwater ions on chromate removal by magnetite: importance of chromate adsorption

Background

Reductive precipitation of hexavalent chromium (Cr(VI)) with magnetite is a well-known Cr(VI) remediation method to improve water quality. The rapid (<a few hr) reduction of soluble Cr(VI) to insoluble Cr(III) species by Fe(II) in magnetite has been the primary focus of the Cr(VI) removal process in the past. However, the contribution of simultaneous Cr(VI) adsorption processes in aged magnetite has been largely ignored, leaving uncertainties in evaluating the application of in situ Cr remediation technologies for aqueous systems. In this study, effects of common groundwater ions (i.e., nitrate and sulfate) on Cr(VI) sorption to magnetite were investigated using batch geochemical experiments in conjunction with X-ray absorption spectroscopy.

Results

In both nitrate and sulfate electrolytes, batch sorption experiments showed that Cr(VI) sorption decreases with increasing pH from 4 to 8. In this pH range, Cr(VI) sorption decreased with increasing ionic strength of sulfate from 0.01 to 0.1 M whereas nitrate concentrations did not alter the Cr(VI) sorption behavior. This indicates the background electrolyte specific Cr(VI) sorption process in magnetite. Under the same ionic strength, Cr(VI) removal in sulfate containing solutions was greater than that in nitrate solutions. This is because the oxidation of Fe(II) by nitrate is more thermodynamically favorable than by sulfate, leaving less reduction capacity of magnetite to reduce Cr(VI) in the nitrate media. X-ray absorption spectroscopy analysis supports the macroscopic evidence that more than 75 % of total Cr on the magnetite surfaces was adsorbed Cr(VI) species after 48 h.

Conclusion

This experimental geochemical study showed that the adsorption process of Cr(VI) anions was as important as the reductive precipitation of Cr(III) in describing the removal of Cr(VI) by magnetite, and these interfacial adsorption processes could be impacted by common groundwater ions like sulfate and nitrate. The results of this study highlight new information about the large quantity of adsorbed Cr(VI) surface complexes at the magnetite-water interface. It has implications for predicting the long-term stability of Cr at the magnetite-water interface.

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Graphical abstract Effects of background anions (sulfate and nitrate) on the Cr(VI) surface coverage at the magnetite-waterinterface at pH 4 and 9

     

Effect of humic acid on the pH-dependent adsorption of terbium (III) onto geological materials

Mobilization of actinides by interaction with humic colloids in aquifers is essentially determined by the geochemical conditions. In this study, the pH dependence of the influence of humic acid on metal adsorption on a variety of geological solids (kaolinite, phyllite, diabase, granite, sand) was investigated for Tb(III) as an analogue of trivalent actinides, using ¹⁶⁰Tb as a radiotracer. Humic material was radiolabelled with ¹³¹I to allow experiments at low DOC concentrations, as encountered in subsurface systems in the far-field of a nuclear waste repository. For all solids, a changeover from mobilization to demobilization is observed on acidification. Except for phyllite, the reversal occurs at slightly acidic pH values, and is thus relevant in respect of risk assessments. A composite distribution model was employed to reproduce the changeover on the basis of the underlying constituent processes. For this purpose, humate complexation of Tb(III) and adsorption of humic acid as a function of pH were investigated as well. Although the ternary systems cannot be constructed quantitatively by combining the binary subsystems, the relevant interdependences are adequately described by the composite approach. For a more general discussion in view of the diversity of natural organic colloids, adsorption isotherms of various humic and fulvic acids on sand were compared.     

The effect of hydrothermal impregnation of Ni,Co, and Cu on HZSM-5 in the nitrogen oxide removal

The selective catalytic reduction (SCR) of nitrogen oxides on M/ZSM-5 (M = Cu, Ni, Co) catalysts was investigated. The catalysts were prepared using hydrothermal impregnation of the metal chlorides and nitrates on ZSM-5. The catalysts were characterized by nitrogen absorption/desorption, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible diffusion reflection spectroscopy (UV–Vis DRS), temperature-programmed reduction (TPR), N₂O chemisorption and ammonia temperature-programmed desorption. The performance tests for SCR of NO were carried out in a fixed-bed reactor from 250 to 400 °C. During the impregnation, part of the aluminum was eliminated from the zeolite framework due to the acidity of the metal salt solution and heating process as indicated by the reduction in the intensity of XRD peaks and variations in the positions of the FTIR vibrational bands. The Cu(Cl)/ZSM-5 catalyst exhibited NO conversions over 90% over the entire temperature range. The other catalysts showed comparable activities, but the catalysts prepared with chloride salt precursors demonstrated higher activity than those based on nitrate as the precursor. Moreover, the TPR reduction peaks of the metal ion in catalysts prepared with chloride precursor were lower, and their UV–Vis absorption bands revealed bathochromic transfers with higher intensities. Concurrent with these changes, the activity of the catalyst increased. The TPR profiles indicated that Cu and Ni both had an oxidation number of +2, whereas Co was present in the oxidation number of +2 and +3. The mass transfer limitation analysis showed that for particles in millimeter size range or larger significant intra-particle mass transfer limitation would be expected.     

Cd adsorption onto Pseudomonas putida in the presence and absence of extracellular polymeric substances

The role of bacterial extracellular polymeric substances (EPS) in metal adsorption was determined by studying Cd adsorption onto the gram-negative bacterial species Pseudomonas putida with and without enzymatic removal of EPS from the biomass material. A range of experimental approaches were used to characterize the Cd adsorption reactions, including bulk proton and Cd adsorption measurements, FTIR spectroscopy, and fluorescence microscopy. The proton-reactivities of the biomass samples with EPS are not significantly different from those obtained for EPS-free biomass. Similarly, the presence of EPS does not significantly affect the extent of Cd removal from solution by the biomass on a mass-normalized basis, based on bulk Cd adsorption measurements conducted as a function of pH, nor does it appear to strongly affect the Cd-binding groups as observed by FTIR. However, fluorescence microscopy indicates that Cd, although concentrated on cell walls, is also bound to some extent to EPS. Together, the results from this study suggest that the P. putida EPS can bind significant concentrations of Cd from solution, and that the nature and mass-normalized extent of the binding is similar to that of the cell wall. Therefore, the EPS-bearing systems do not exhibit enhanced mass-normalized removal of Cd from solution relative to the EPS-free systems. The presence of the EPS effectively increases the viability of cells exposed to aqueous Cd, likely due to sequestration of the Cd away from the cells due to Cd-EPS binding.     

Kinetics of lead adsorption by iron oxides formed under the influence of citrate

The presence of organic acids greatly affects the formation of Fe oxides and surface properties; however, the subsequent effect on the kinetics and mechanisms of Pb adsorption by the Fe oxides formed under the influence of organic acids remains obscure. The kinetics of Pb adsorption on the Fe oxides formed in the presence of citrate ligands at initial citrate/Fe(II) molar ratios (MRs) of 0, 0.001, 0.01, and 0.1 was studied at the initial Pb concentration of 8.33 μM and pH 5.0 at 278, 288, 298, and 313 K using macroscopic batch method. The results indicate that the Pb adsorption followed multiple first-order kinetics and the rate coefficient, activation energy, and pre-exponential factor in the Arrhenius equation of the adsorption varied greatly with the surface properties of the Fe oxides formed at various citrate/Fe(II) MRs. The alteration of surface properties of Fe oxides formed at the citrate/Fe(II) MR of 0.1 and the effect on the rate coefficient of the fast and slow reactions of Pb adsorption were especially significant. The rate-limiting step of Pb adsorption reactions on the Fe oxides was predominantly a diffusion process, except for the slow reaction of Pb adsorption on the Fe oxides formed at the initial citrate/Fe(II) MR of 0.1, where the rate-limiting process was evidently a chemical process, which may involve bond breaking between the coprecipitated citrate ligand and Fe oxide. The rate coefficients of Pb adsorption by the Fe oxides formed at various citrate/Fe(II) MRs cannot be explained by the activation energy alone. The pre-exponential factor plays an important role in influencing the rate coefficient of Pb adsorption by the Fe oxides. The role of organic acids such as citric acid in influencing the crystallization and the resultant alteration of surface properties of Fe oxides, and the impact on the dynamics of Pb in terrestrial and aquatic environments, thus merit close attention.     

Influence of the natural organic matter in the removal of caffeine from water by fixed-bed column adsorption

The removal of caffeine from tap water by F-400 granular activated carbon in fixed-bed adsorption experiments was carried out. Textural and chemical characterization of the adsorbent through N₂ adsorption–desorption isotherms, Fourier transform infrared spectrometry, isoelectric point determination and scanning electron microscopy studies was developed in studies previously reported. Caffeine breakthrough curves and total organic carbon profiles at different operation conditions (inlet concentration, volumetric flow rate and mass of adsorbent) were obtained. These experimental results showed a displacement of the natural organic matter from the active sites exerted by caffeine molecules due to their higher affinity to the surface carbon. This behavior led to an overshooting, a local outlet natural organic matter concentration higher than the feed quantity. A competitive effect seems to be observed in the removal of the target compound, decreasing the efficiency of the process. Axial dispersion coefficients and dimensionless numbers were estimated for the caffeine removal onto F-400 activated carbon. Therefore, the regeneration of the adsorbent by adsorption–desorption cycles was studied.