Fulvic Acid Sorption Research Articles

Sorption of Fulvic Acids onto Titanium Dioxide Nanoparticles Extracted from Commercial Sunscreens: ToF-SIMS and High-Dimensional Data Analysis

Titanium dioxide nanoparticles (n-TiO2) are common ingredients of sunscreens and are often released into surface waters during usage. Once released, the surface chemistry of n-TiO2 changes by interacting with dissolved organic matter (DOM). In previous studies, these interactions were investigated using model n-TiO2 and; therefore, do not account for the complex composition of the coating of n-TiO2 aged in sunscreens. Taking advantage of a mild extraction method to provide more realistic nanoparticles, we investigated the potentials of time of flight-secondary ion mass spectrometry (ToF-SIMS) combined with high-dimensional data analysis to characterize the sorption of fulvic acids, as a model for DOM, on titanium dioxide nanoparticles extracted from ten different commercial sunscreens (n-TiO2 ⸦ sunscreen). Clustering analysis confirmed the ability of ToF-SIMS to detect the sorption of fulvic acids. Moreover, a unique sorption pattern was recognized for each n-TiO2 ⸦ sunscreen, which implied different fractionation of fulvic acids based on the initial specifications of nanoparticles, e.g., size, coating, etc. Furthermore, random forest was used to extract the most important fragments for predicting the presence of fulvic acids on the surface of n-TiO2 ⸦ sunscreen. Finally, we evaluate the potential of ToF-SIMS for characterizing the sorption layer.

Sorption of Fulvic Acids and Their Compounds with Heavy Metal Ions on Clay Minerals

In real soils the interaction of humic substances with clay minerals often occurs with the participation of metal cations. The adsorption of fulvic acids (FA) solution and their solutions in the presence of heavy metal ions (Pb or Zn) on two clay minerals (kaolinite and bentonite) was investigated by measurement of the optical density changes in the of equilibrium solutions. The FA adsorption by bentonite at the concentrations 0.05–1 g/L proceeds according to the polymolecular mechanism and has a stepwise character. The adsorption of FA on kaolinite can be described by the mechanism of monomolecular adsorption. In three-component systems, including FA, trace element ions and a clay mineral, complex processes occur, including the formation of complexes and salts and their adsorption. The sorption of colored complexes of FA with Pb on the surface of kaolinite and bentonite increases with increasing metal concentrations (0.5–2 mmol/L). The interaction of the FA-Zn2+ compounds with bentonite is a more complicated process—adsorption takes place at the lowest concentration used only. Thus, binding of FA by clay minerals in the presence of metal cations is a complex phenomenon due to the chemical heterogeneity of FA, different properties of metals, characteristics of mineral surfaces and the variability of environmental conditions.

Molecular insights into the role of fulvic acid in cobalt sorption onto graphene oxide and reduced graphene oxide

The role of fulvic acid (FA) in the sorption of Co(II) onto reduced graphene oxide (RGO) and graphene oxide (GO) were investigated using batch equilibrium method and extended X-ray absorption fine structure (EXAFS). The results showed that FA could be adsorbed on both RGO and GO via different interaction mechanisms, and thus exert different roles in Co(II) sorption. The sorption of FA on RGO was mainly controlled by π–π interaction, and the adsorbed FA introduced negative charges and O-bearing functional groups on RGO, facilitating Co(II) sorption due to electrostatic attraction and complexation. Meanwhile, the sorption of FA on GO was mainly governed by polar interactions, and the adsorbed FA can not only introduce new sites for enhanced Co(II) sorption, but also shield the surface of GO and occupy parts of sorption sites, which decreased Co(II) sorption. So, FA had little role in Co(II) sorption onto GO. EXAFS results suggest that O-bearing functional groups of RGO and GO were the main sorption sites for Co(II). Compared to GO, a portion of Co(II) precipitate on RGO surfaces at pH 8.78 due to fewer O-bearing functional groups. The introduction of FA provides lots of sorption sites on RGO, which makes Co(II) be adsorbed on RGO as RGO-FA-Co ternary surface complexes. The results of this work indicated that both RGO and GO exhibited great potential in pollution control applications, even in mixed organic and inorganic pollutants.

The effect of MWCNT treatment by H2O2 and/or UV on fulvic acids sorption

The carbon nanotubes (CNT) present in the wastewater subjected to treatment will possess altered physico-chemical properties. The changed properties will result in the unknown behavior of CNT in the environment after disposal; and it is expected to differ from their pristine analogues. In the present paper the effect of sorption of dissolved organic matter with fulvic acids (FA) as representatives onto UV and/or H2O2 treated CNT was tested. Both kinetics and mechanism of sorption was estimated. The chemical adsorption was a rate limiting step and a pseudo-second order kinetics described the sorption of FA onto UV and/or H2O2 treated CNT. The treating increased affinity towards FA and treating by UV and H2O2 simultaneously possessed greater impact on k2 than UV and H2O2 separately. The greatest effect on CNT sorption capacity revealed H2O2. The sorption mechanism was described by Temkin (CNT-H2O2) and Dubinin-Radushkevich model. The increase in CNT surface disorder caused by UV and/or H2O2 treatment favored sorption of FA via π-π interactions (exfoliated surface and disordered CNT walls). FA sorption occurred between aromatic rings of FA and CNT and hydrogen bonds formed with the oxygen functional groups. The results indicate that UV and/or H2O2 treatment affected the sorption capacity and affinity of CNT towards FA.

Effect of mineral surface properties (alumina, kaolinite) on the sorptive fractionation mechanisms of soil fulvic acids: Molecular-scale ESI-MS studies

We addressed the effects of mineral surface properties (kaolinite versus Al-oxide) on the sorption-driven fractionation of a soil fulvic acid (FA) at acidic pH, mainly by means of ESI(−)-FTMS analysis of initial and supernatant solutions of FA sorption batch experiments. The MS data provided clear molecular-scale evidence of distinct mechanisms and molecular parameters controlling the FA fractionation upon its sorption on clay and oxide surfaces, respectively.Identification of sorbing and not-sorbing FA compounds in kaolinite-solution systems revealed a weak fractionation among members of CO2 series of aliphatics or not-condensed aromatics (NCAs) at pH 3.8, and almost no sorption of poorly-oxygenated polycyclic aromatic compounds (PACs) and NCAs. This first molecular-scale description of a FA fractionation in a clay-solution system suggests that H-bonding with low affinity sites (aluminol/silanol) on the basal planes of the clay particles is the main mechanism of sorption. Due to the predominance of such weak and poorly-selective mechanism, the sorption of aliphatic and NCA molecules bearing oxygenated functionalities was prevented at pH 5, due to dissolved Al competing successfully for their coordination.In contrast, a strong FA fractionation was observed onto alumina, with a preferential retention of PACs and highly-oxygenated aliphatics and NCAs. The major part of the poorly oxygenated aliphatics was left in solution. The sorption degree of NCAs and aliphatics was strongly correlated with molecular acidity. For PACs and poorly-oxygenated NCAs, the sorption was driven by reactions of surface ligand exchange (for the most oxygenated compounds) or by hydrophobic interactions (for the least oxygenated compounds).

The interactions of UV and/or H2O2 treated CNTOH and CNTCOOH with environmental fulvic acids

The fate of carbon nanotubes (CNT) in the environment will be governed by the presence of natural dissolved organic matter (DOM). Many studies indicate that CNT create stabilized suspensions in the presence of DOM. Easier transport in the environment may indicate their greater hazard. However these studies describe the interactions of DOM with as produced CNT. In the present studies the interactions of UV and/or H2O2 treated wastewater containing CNTOH or CNTCOOH with the naturally occurred fulvic acids (FA) were presented. FA sorption, both kinetics and mechanism, were described using batch regime. The sorption of FA followed a pseudo-second order kinetics and was described with the highest accuracy by Langmuir or Dubinin-Radushkevich model for CNTOHs and Langmuir, Temkin or Dubinin-Radushkevich - for CNTCOOHs. The mechanism of FA sorption onto CNTOHs was ascribed to π-π, heterogeneous and electrostatic interactions. The π-π and electrostatic interactions can the mostly defined FA adsorption onto CNTCOOHs. The parameters affecting FA sorption were combination of porosity and dispersity.

Sorption of Eu(III) on Th4(PO4)4P2O7: effects of pH, complexing anions and fulvic acid

The sorption of Eu(III) on Th4(PO4)4P2O7 was studied under ambient conditions using the batch technique. The effects of pH, the concentrations of Eu(III) on Th4(PO4)4P2O7 sorption were investigated. The sorption characteristics of sulfate, phosphate and fulvic acid (FA) on Th4(PO4)4P2O7 was explored in the presence Eu(III). The results indicated that sorption of Eu(III) on Th4(PO4)4P2O7 was strongly affected by pH and the concentrations of Eu(III). Eu(III) sorption onto Th4(PO4)4P2O7 was greatly enhanced in FA and phosphate media than in KNO3. The Langmuir, Freundlich and D–R model were used to simulate the sorption isotherms of Eu(III) at four different medium. FA sorption isotherm can be described by Langmuir model in presence and absence of Eu(III) in solution.

Molecular level description of the sorptive fractionation of a fulvic acid on aluminum oxide using electrospray ionization Fourier transform mass spectrometry.

We addressed here, by means of electrospray ionization mass spectrometry (ESI-MS) with ultrahigh resolution, the molecular level fractionation of a reference fulvic acid (SRFA) during its sorption at an alumina surface, taken as a model for surfaces of natural aluminum oxide hydrates. Examination of ESI-MS spectra of a native SRFA solution and of supernatants collected in sorption experiments at acidic pH showed that the ∼5700 compounds identified in the native solution were partitioned between the solution and alumina surface to quite varying degrees. Compounds showing the highest affinity for the surface were aromatic compounds with multiple oxygenated functionalities, polycyclic aromatic compounds depleted of hydrogen and carrying few oxygenated groups, and aliphatic compounds with very high O/C values, highlighting the fact that SRFA constituents were sorbed mainly via chemical sorption involving their oxygenated functionalities. We observed an inverse correlation between the degree of sorption of a molecule within a CH2 series and its number of CH2 groups and a positive correlation between the degree of sorption and the number of CO2 groups in a COO series, which was remarkable. These correlations provide evidence at the molecular scale that molecule acidity is the key parameter governing fulvic acid (FA) sorptive fractionation, and they are useful for predicting sorption of FA at a natural oxide surface.

Effects of Fulvic Acid on Uranium(VI) Sorption Kinetics

This study focuses on the effects of fulvic acid (FA) on uranium(VI) sorption kinetics to a silica sand. Using a tritium-labeled FA in batch experiments made it possible to investigate sorption rates over a wide range of environmentally relevant FA concentrations (0.37-23 mg L(-1) TOC). Equilibrium speciation calculations were coupled with an evaluation of U(VI) and FA sorption rates based on characteristic times. This allowed us to suggest plausible sorption mechanisms as a function of solution conditions (e.g., pH, U(VI)/FA/surface site ratios). Our results indicate that U(VI) sorption onto silica sand can be either slower or faster in the presence of FA compared to a ligand-free system. This suggests a shift in the underlying mechanisms of FA effects on U(VI) sorption, from competitive sorption to influences of U(VI)-FA complexes, in the same system. Changes in metal sorption rates depend on the relative concentrations of metals, organic ligands, and mineral surface sites. Hence, these results elucidate the sometimes conflicting information in the literature about the influence of organic matter on metal sorption rates. Furthermore, they provide guidance for the selection of appropriate sorption equilibration times for experiments that are designed to determine metal distribution coefficients (Kd values) under equilibrium conditions.

Removal of Cu(II) and Fulvic Acid by Graphene Oxide Nanosheets Decorated with Fe3O4 Nanoparticles

Graphene oxide/Fe(3)O(4) (GO/Fe(3)O(4)) composites were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The removal of Cu(II) and a natural organic macromolecule (fulvic acid (FA)) by GO/Fe(3)O(4) was investigated. The mutual effects of FA/Cu(II) on Cu(II) and FA sorption onto GO/Fe(3)O(4), as well as the effect of pH, ionic strength, FA/Cu(II) concentrations, and the addition sequences of FA/Cu(II) were examined. The results indicated that Cu(II) sorption on GO/Fe(3)O(4) were strongly dependent on pH and independent of ionic strength, indicating that the sorption was mainly dominated by inner-sphere surface complexation rather than outer-sphere surface complexation or ion exchange. The presence of FA leads to a strong increase in Cu(II) sorption at low pH and a decrease at high pH, whereas the presence of Cu(II) led to an increase in FA sorption. The adsorbed FA contributes to the modification of sorbent surface properties and partial complexation of Cu(II) with FA adsorbed. Different effects of FA/Cu(II) concentrations and addition sequences on Cu(II) and FA sorption were observed, indicating the difference in sorption mechanisms. After GO/Fe(3)O(4) adsorbed FA, the sorption capacity for Cu(II) was enhanced at pH 5.3, and the sorption capacity for FA was also enhanced after Cu(II) sorption on GO/Fe(3)O(4). These results are important for estimating and optimizing the removal of metal ions and organic substances by GO/Fe(3)O(4) composites.

Effect of fulvic acid on neodymium uptake by goethite

Experimental studies of the interaction of aqueous neodymium (Nd), Suwannee River fulvic acid (FA), and solid phase goethite were conducted. Results from blank systems (individual Nd and FA), binary systems (Nd–goethite, FA–goethite, and Nd–FA), and ternary systems (Nd–FA–goethite) at 0.1mol/kg and 25°C are reported.In the binary Nd–goethite system a classic sorption edge is observed, whereby virtually all Nd is removed from solution above the goethite point of zero charge (PZC). Similarly, the binary FA–goethite system exhibits strong FA sorption; However in this system near complete removal of FA from solution is observed below the goethite PZC. In the binary Nd–FA system, both aqueous Nd and FA feature a sharp decrease in concentration at ca. pH 9.Various experiments in the ternary system were conducted. For all concentrations, FA enhanced Nd sorption below the goethite PZC, attributed to the formation of a Type B ternary surface complex (mineral–ligand–metal ion). Notably, the 100ppm FA ternary system showed anomalously high dissolved Nd in solution above the PZC (i.e., Nd sorption suppression) and a concomitant increase in goethite dissolution (∼9ppm total Fe3+ observed above circa pH 9.5).Our results suggest that Nd–FA complexation plays a key role in Nd uptake by goethite, and that this process is largely governed by pH: Whereas at pHs below the goethite PZC, Nd–FA complexation facilitates Nd sorption, above the PZC, and particularly at elevated FA concentrations, the formation of aqueous Nd–FA complexes suppresses Nd removal. Moreover, under these conditions, goethite dissolution may also play a role in mitigating Nd uptake by goethite.

Effects of Solution Chemistry on the Adsorption of Ibuprofen and Triclosan onto Carbon Nanotubes

Single-walled carbon nanotubes (SWCNTs), multiwalled carbon nanotubes (MWCNTs), and oxidized MWCNTs (O-MWCNTs) were studied for the adsorption of ibuprofen (IBU) and triclosan (TCS) as representative types of pharmaceutical and personal care products (PPCPs) under different chemical solution conditions. A good fitting of sorption isotherms was obtained using a Polanyi-Manes model (PMM). IBU and TCS sorption was stronger for SWCNTs than for MWCNTs due to higher specific surface area. The high oxygen content of O-MWCNT further depressed PPCP sorption. The sorption capacity of PPCPs was found to be pH-dependent, and more adsorption was observed at pHs below their pK(a) values. Ionic strength was also found to substantially affect TCS adsorption, with higher adsorption capacity observed for TCS at lower ionic strength. In the presence of a reference aquatic fulvic acid (FA), sorption of IBU and TCS was reduced due to the competitive sorption of FA on carbon nanotubes (CNTs). Sorption isotherm results with SWCNTs, MWCNTs and O-MWCNTs confirmed that the surface chemistry of CNTs, the chemical properties of PPCPs, and aqueous solution chemistry (pH, ionic strength, fulvic acid) all play an important role in PPCP adsorption onto CNTs.

Surfactant-modified clinoptilolite-rich tuff to remove barium (Ba 2+) and fulvic acid from mono- and bi-component aqueous media

The kinetics of the removal of Ba 2+ and fulvic acid by a surfactant-modified Mexican clinoptilolite-rich tuff was investigated. The effect of fulvic acid in a bi-component aqueous medium (Ba 2+-fulvic acid) on the sorption of Ba 2+ was also considered, and an unmodified zeolitic material was included for comparison. The Ba 2+, fulvic acid and fulvic acid-Ba 2+ solutions were placed in contact with a Mexican clinoptilolite-rich tuff in a batch system. Atomic absorption and UV–Vis spectroscopy were used to measure the remaining aqueous barium and fulvic acid, respectively. The Ba 2+ and fulvic acid sorption kinetic experimental data were best fitted by a pseudo-second-order model. The amount of surfactant covering the surface of the zeolitic material and the fulvic acid influenced the sorption kinetics of Ba 2+ from aqueous media by sodium and surfactant-modified Mexican clinoptilolite-rich tuffs. The presence of Ba 2+ in the aqueous medium increased the sorption of fulvic acid by the sodium-modified zeolite from Oaxaca (NaZO), but the time to reach equilibrium was greater. The Ba 2+ was removed from aqueous media by ion exchange or complexation with fulvic acid, and fulvic acid was adsorbed by the surfactant-modified zeolites through a partitioning mechanism.

The role of sorption and bacteria in mercury partitioning and bioavailability in artificial sediments

This study compared the relative importance of three types of sorption (organic matter–particle, mercury–organic matter and mercury–particle) in controlling the overall mercury partitioning and bioavailability in sediments. We found that all three types of sorption were important for both inorganic mercury (Hg) and methylated mercury (MeHg). Mercury–particle sorption was more important than mercury–fulvic acid (FA) sorption in increasing the mercury concentrations with increasing aging. Bioavailability (quantified by gut juice extraction from sipunculans) was mainly controlled by mercury–particle sorption, while FA–particle and mercury–FA sorption were not as important, especially for MeHg. Bacterial activity also increased the partitioning of Hg or MeHg in the sediments and was further facilitated by the presence of organic matter. The bioavailability of Hg or MeHg from sediments was only slightly influenced by bacterial activity. This study highlights the importance of sorption from various sources (especially mercury–particle sorption) as well as bacteria in controlling the partitioning and bioavailability of Hg or MeHg in sediments.

Fulvic Acid Sorption on Muscovite Mica as a Function of pH and Time Using In Situ X-ray Reflectivity

Interfacial structures of the basal surface of muscovite mica in 100 mg kg (-1) Elliott Soil Fulvic Acid II solutions were investigated using in situ X-ray reflectivity. Molecular-scale variations in the thickness and internal structure of the fulvic acid (FA) film were observed and quantified as a function of pH (2-12) and reaction time (3-500 h at pH 3.7). At pH < or =6, the electron-density profile of the FA layer sorbed on the muscovite surface was composed of one near-surface peak followed by a broad peak that diminished in electron density with distance from the surface. The presence of the near-surface peak is attributed to condensation of FA molecules during sorption. The apparent thickness of the FA layer decreased from 12.3 to 7.2 to 6.4 A as pH increased from 2 to 3.7 to 6, respectively. At pH > or =8.5, a distinct interfacial structure was observed, consisting of sharper peaks similar to those previously observed for muscovite in the absence of FA. These peaks are most likely composed of smaller aqueous species, such as H 2O molecules, metal ion impurities from FA, and Na (+) from NaOH. The FA sorbed on the muscovite surface at pH 3.7 maintained a relatively constant thickness after 3 hours. However, the electron density of the near-surface FA peak increased by about 24% from 3 to 12 hours, and remained relatively constant from 12 to 500 hours. The electron density of the more distant part of the sorbed FA layer increased slightly after 12-50 hours of reaction but then decreased, and the broad peak flattened by 500 hours. Internal structural changes are possibly due to the slow sorption rate of FA molecules, or a fractionation effect, i.e., continuous subsitution of smaller FA molecules by larger FA molecules.

Adsorption characterizations of fulvic acid fractions onto kaolinite

Fulvic acids extracted from a typical rice-production region near Taihu Lake of China were fractionated into three fractions including F4.8, F7.0 and F11.0 (eluted by pH 4.8 buffer, pH 7.0 buffer and pH 11.0 buffer, respectively). Sorption of fulvic acid (FA) fractions onto kaolinite was studied by batch adsorption experiments, and characterizations of kaolinite before and after adsorption were investigated using scanning electron microscopy (SEM). Adsorption isotherms of kaolinite for three FA fractions fit well with the Langmuir adsorption model. The adsorption density of the three fractions was positively correlated with the ratio of the amount of the alkyl carbon to that of carboxyl and carbonyl carbon in FA fractions and followed an order of F11.0 > F7.0 > F4.8. Hydrophobic interaction was one of the control mechanisms for the sorption of FA fraction onto kaolinite. SEM images confirmed that compared to blank kaolinite samples, kaolinite samples coated by a FA fraction displayed an opener and more dispersed conformation resulting from the disruption of the floc structure in complex. Dispersion of kaolinite after adsorption was due to the repulsion between negatively charged FA-coated particles, which is closely related to the amount of FA fractions absorbed on kaolinite.

A New Method to Radiolabel Natural Organic Matter by Chemical Reduction with Tritiated Sodium Borohydride

In this paper, we describe a new method for labeling NOM with the radioisotope tritium (3H) using fulvic acid (FA) as the target NOM fraction. During labeling, FA ketone groups are chemically reduced with tritiated sodium borohydride (NaBH4), while the chemical functionality of the carboxyl and phenol groups is preserved. The labeling procedure was optimized in efficiency experiments that determined the excess concentration of tritiated NaBH4 required for optimum reduction conditions. The chemical characterization of the labeled FA product using FTIR and 1H NMR spectral analysis confirms the proposed reaction mechanism and rules out any significant amounts of impurities or undesirable side reactions. Results from size exclusion chromatography indicate thatthe tritium label is distributed uniformly over the whole molecular size range of FA and that it is stable over time and under various pH conditions. Potential differences in FA sorption behavior onto mineral surfaces due to labeling were excluded based on experimental data. This method produces NOM of high specific activity (e.g., 1.9 mCi mg(-1) FA); this permits the tracing of FA at a detection limit of 0.3 microg L(-1) FA.

Sequential injection analysis as a tool for on-line monitoring the sorption of fulvic acid onto modified vermiculite

This paper presents a sequential injection system associated with a tangential filtration unit and an ultraviolet detector for on-line monitoring of fulvic acid sorption onto two modified vermiculites. With the proposed approach it was possible to improve the temporal resolution in the investigation of the equilibrium time needed for the system sorbent-sorbate to reach the chemical equilibrium. Sorption onto a 10 g L-1 suspension of vermiculite material modified by intercalation of polyhydroxycations of Fe(III) was fast, reaching the equilibrium after 4 min of contact time, and resulting in sorption of 97.9 % of the initial 10 mg L-1 fulvic acid concentration. Sorption onto a 10 g L-1 suspension of an organic vermiculite which was modified by ion exchange with hexadecyltrimethylammonium bromide exhibited a fast initial rate of sorption, followed by desorption and re-adsorption processes, reaching the equilibrium after 30 min of contact time, with sorption of 98% of the initial 10 mg L-1 fulvic acid concentration.

Adsorption mechanism of fulvic acid onto freeze dried poly(hydroxo aluminum) intercalated bentonites

Two poly(hydroxo aluminum) intercalated Wyoming bentonites were prepared starting from two different aluminum pillaring solutions. The sorption mechanism of Laurentian fulvic acid (FA) onto these poly(hydroxo aluminum) intercalated bentonites was investigated at different pH values and at different ionic strengths (NaCl or CaCl2). Three mechanisms contribute to the FA adsorption, depending on the pH and the nature (NaCl or CaCl2) and ionic strength of the background electrolyte. In the presence of NaCl the FA sorption onto poly(hydroxo aluminum) intercalated bentonites can be mainly ascribed to ligand exchange between the amphoteric poly(hydroxo aluminum) hydroxyl groups and the deprotonated carboxylic groups of the FA. The FA adsorption due to ligand exchange reactions decreases with increasing pH. In presence of Ca2+ ions the FA adsorption is enhanced, compared to the presence of Na+, due to Ca2+ bridging between negatively charged groups on the FA molecules and the poly(hydroxo aluminum) intercalated bentonite. The FA adsorption due to Ca2+ bridging increases with increasing pH. A third mechanism is enhanced FA adsorption ascribed to FA-Ca-FA bridging and was detected from the FA adsorption in presence of Ca2+ at the zero point of charge of the poly(hydroxo aluminum) bentonite (pH 5).

Influence of the synthesis method of Al-hydroxy intercalated clays on their fulvic acid sorption capacity

The purpose of this study was to investigate the potential use of both Al-hydroxy intercalated clays and ‘pillared clays’ (calcinated Al-hydroxy intercalated clays) for the removal of fulvic acids (FA) from water. Different preparation procedures of the Al-hydroxy intercalated clays were tested and the products were characterised (XRD and N2 sorption) and tested for their FA sorption capacity. It was observed that the drying method (oven or freeze-drying) and the calcination step were the most important parameters influencing the FA sorption capacity of the Al-hydroxy intercalated clays. The noncalcined freeze-dried Al-hydroxy intercalated clays showed the largest sorption capacity for FA. Comparison with freeze-dried Wyoming bentonite and granular activated carbon showed that this freeze-dried Al-hydroxy intercalated clays are potential good sorbents for the removal of fulvic acids from water.