Adsorption Of Humic Acid Research Articles

Structure and Properties of Nanosized Composites Based on Fe3O4 and Humic Acids

Nanocrystalline composite materials based on magnetite Fe3O4 and humic acids (HA) were synthesized and characterized. Investigation of these materials by EPR, fluorescence spectroscopy, electron microscopy, and XRD analysis showed that the surface of magnetite nanoparticles was densely covered with HA molecules, the size of the Fe3O4 nucleus decreasing when the HA : Fe3O4 ratio increased. An EPR study showed that the structure of the ferromagnetic magnetite nanoparticles changed at increased HA contents. The IR and fluorescence spectroscopy data suggest active participation of carboxyl and hydroxyl groups of HA in the adsorption of HAs on the Fe3O4 surface. The main types of interaction of Fe3O4 with HA were considered, and a scheme of possible chemical reactions was proposed.

Mechanism of adsorption of humic acid by modified aged refuse.

In the present study, aged refuse (AR) was modified to be applied as an adsorbent to remove humic acid from water. The efficiency of humic acid removal by modified aged refuse (MAR) under different preparation conditions (calcination temperature, dose of aged refuse for calcination and holding time) was systematically investigated. Results showed that the optimum preparation conditions are calcination temperature = 700 °C, AR dose for calcination = 25 g, and holding time = 2.0 h. The characteristics of the modified aged refuse obtained under different calcination conditions were determined by Fourier transform infrared, X-ray diffraction and X-ray photoelectron spectroscopy analysis. In addition, the effects of modified aged refuse dose and initial solution pH on adsorption performance were studied. The removal of humic acid increased with higher doses of modified aged refuse, and weak alkaline (initial pH = 8.0) conditions were favorable for humic acid removal. A pseudo-second order model fitted the experimental data well. Moreover, the adsorption isotherms were well described by the Langmuir isotherm model, in which the monolayer surface loading was calculated to be approximately 37 mg g−1. During the adsorption process, the molecular weight, degree of condensation and aromaticity of humic acid were considerably decreased, according to 3D-EEM analysis. MAR as a new type of adsorbent thus provides a potential adsorption method for humic acid.

FeNi3@SiO2 magnetic nanocomposite as a highly efficient Fenton-like catalyst for humic acid adsorption and degradation in neutral environments

FeNi3@SiO2 magnetic nanocomposite as a highly efficient Fenton-like catalyst for humic acid adsorption and degradation in neutral environments

Effects of dissolved oxygen, pH, salinity and humic acid on the release of metal ions from PbS, CuS and ZnS during a simulated storm event

Metal sulfides serve as the sinks of toxic heavy metals in anoxic sediments. Once exposed to fluctuations in environmental conditions, dissolution of metal sulfides can occur and release toxic heavy metal ions into water column. In this study, we investigated the effects of dissolved oxygen (DO), pH, salinity and humic acid (HA) on the dissolution of CuS, PbS and ZnS using batch experiments with continuous aeration to simulate the re-suspension of these metal sulfides during a storm event. Experimental results indicated that oxidative dissolution of CuS, PbS and ZnS occurred in the presence of DO. The rate was the fastest for PbS, followed by CuS and ZnS. Soluble metal concentrations also increased with decreasing pH under oxic conditions. Compared to metal sulfides dissolution rates in freshwater without HA, the presence of saline conditions and HA generally accelerated the dissolution of CuS but inhibited the dissolution of PbS and ZnS. A higher saline or HA concentration, however, did not always lead to a stronger enhanced or inhibited dissolution rate, which could be a collective effect resulting from ligand-enhanced dissolution, complexation, and decreased oxygen and proton attacks due to HA adsorption on the metal sulfide surfaces.

Selective flotation separation of molybdenite and talc by humic substances

Humic acid (HA) has been studied as a potential selective depressant for molybdenite in the flotation separation of molybdenite and talc in this paper. In the single mineral flotation tests, HA has shown good depression ability to molybdenite over the entire pH range tested from pH 3–11, while the floatability of talc was only affected by HA under strong acidic condition (pH 3). In the mixed minerals flotation, HA can effectively depress the flotation of molybdenite while not affecting the flotation of talc under strong alkaline condition (pH 11). Contact angle measurements have proved that the hydrophobicity of both talc and molybdenite decreases after treatment by HA, however, the contact angles of treated talc are still higher than molybdenite. Equilibrium adsorption studies indicate that HA has a much higher adsorption density on molybdenite than on talc. The preferential adsorption of HA on molybdenite was further confirmed by diffusion reflectance infrared Fourier transform spectroscopy (DRIFTS) and atomic force microscopy (AFM) imaging. All of the experimental results suggest that humic acids can be employed as a selective depressant for molybdenite during the flotation separation of molybdenite and talc under alkaline conditions, and the higher adsorption density of HA on molybdenite over talc is the primary reason for the selective separation.

Preparation of Permanent Magnetic Resin Crosslinking by Diallyl Itaconate and Its Adsorptive and Anti-fouling Behaviors for Humic Acid Removal

In this research, a series of permanent magnetic anion exchange resins (MAERs) were prepared by polymerizing glycidyl methacrylate monomer and crosslinking diallyl itaconate (DAI) and divinylbenzene. The properties and performances of these novel MAERs were systematically characterized and evaluated for humic acid (HA) adsorption by batch experiments. With the increase of DAI content from 0 to 15%, the moisture of MAERs was elevated from 50.23% to 68.53%, along with the adsorption capacity increasing from 2.57 to 3.14 mmol g−1. As the concentrations of co-existing cation (Ca2+ and Mg2+) increased, the adsorption amounts of HA dropped drastically at first and increased a little at high cation concentrations. Although ion exchange was the primary mechanism for HA adsorption, other physical interactions and electrostatic attraction between HA molecules and newly formed oxonium group also played significant roles for HA adsorption. The MAERs could be efficiently regenerated by a mixture of NaCl/NaOH solution (10%/1%), and notably, the MAER-3 with the highest DAI content displayed unapparent loss of adsorption capacity during twenty-one successive adsorption-desorption cycles. These results suggested a novel resin adsorbent for its excellent performances on adsorption, regeneration, and sedimentation in water treatment for natural organic matter removal.

Microbial reduction of Ferrihydrite in the presence of reduced Graphene oxide materials: Alteration of Fe(III) reduction rate, biomineralization product and settling behavior

Although graphene-based materials have been shown to physicochemically interact with biotic or abiotic particles after entering into the environment, little is known about their impacts on biotransformation of inorganic colloids. Accordingly, the effects of different reduced graphene oxide (rGO) materials on ferrihydrite reduction were investigated by using Shewanella oneidensis MR-1 and lactate as Fe(III) reducer and electron donor, respectively. rGO at 0.5mgL−1 stimulated the transformation of ferrihydrite to magnetite, possibly by improving electron transfer. In contrast, higher concentrations of rGO (10–100mgL−1) hindered the exposure, accessibility and therefore reduction of ferrihydrite, resulting in the formation of a mixture of goethite and magnetite. The adsorption of soil humic acid by coexisting ferrihydrite and rGO resulted in further inhibition of Fe(III) reduction. On the other hand, the enhanced Fe(III) bioreduction by the less adsorbable aquatic humic acid or simpler flavin molecules was further improved by 0.5mgL−1 rGO but inhibited by 50mgL−1 rGO. Additionally, the settling stability of the rGO-mineral aggregates was altered during bioreduction, which could influence the transport and reactivity of iron mineral and the fate of associated rGO. This study improves our understanding of the impact and behavior of rGO in the environment.

Aqueous aggregation behavior of citric acid coated magnetite nanoparticles: Effects of pH, cations, anions, and humic acid

Improving the colloidal stability of magnetite nanoparticles (MNPs) is essential for their successful applications. In this study, the surface zeta potential and particle size evolutions of citric acid coated magnetite nanoparticles (CA-MNPs) were measured under varied aqueous conditions using dynamic light scattering (DLS). The effects of pH (5.0–9.0), ionic strength (IS), cations (Na+ and Ca2+), anions (phosphate, sulfate, and chloride) and humic acid on the aggregation behaviors of CA-MNPs were explored. Compared with bare MNPs, the stability of CA-MNPs were greatly improved over the typical pH range of natural aquatic environments (pH = 5.0–9.0), as the coated CA-MNPs were highly negatively charged over the pH range due to the low pKa1 value (3.13) of citrate acid. CA-MNPs were more stable in the presence of monovalent cation (Na+) compared with divalent cation (Ca2+), as Ca2+ could neutralize the surface charge of MNPs more significantly than Na+. In the presence of anions, the surface charges of CA-MNPs became more negative, and the stability of CA-MNPs followed the order: in phosphate > sulfate > chloride. The observed aggregation trend could be explained by the differences in the valences of the anions and their adsorption behaviors onto CA-MNPs, which altered the surface charges of CA-MNPs. The measured critical coagulation concentrations (CCC) values of CA-MNPs in these electrolyte solutions agreed well with Derjaguin–Landau–Verwey–Overbeek (DLVO) calculations. With the addition of Humic acid (HA), the aggregation of CA-MNPs was inhibited in all electrolyte solutions even with the critical coagulation concentrations. This is due to the adsorption of HA onto CA-MNPs, which enhanced the electrostatic and steric repulsive forces between CA-MNPs. Considering the good stability of CA-MNPs in solutions with varied pH and electrolyte compositions, as well as with the easy synthesis of CA-MNPs and their non-toxicity, this study suggested CA coating as a good strategy to increase the stability of MNPs.

Study on kinetics of adsorption of humic acid modified by ferric chloride on U(VI)

In order to reveal the adsorption mechanism of the ferric chloride modified humic acid on uranium, the influence of pH value and contact time of adsorption on uranium was studied through a series of batch experiments. Meanwhile, the adsorption kinetics was analyzed with pseudo-first order kinetic model and pseudo-second order kinetic model. The results show that adsorption is affected by the pH value of the solution and by contract time, and the best condition for adsorption on uranium is at pH=5 and the adsorption equilibrium time is about 80 min. Kinetics of HA-Fe adsorption on uranium accords with pseudo-second order kinetic model. The adsorption is mainly chemical adsorption, and complexes were produced by the reaction between uranium ions and the functional groups on the surface of HA-Fe, which can provide reference for further study of humic acid effecting on the migration of U(VI) in soil.

Dual-Pore Carbon Shells for Efficient Removal of Humic Acid from Water.

A template-mediated process for the preparation of mesoporous carbon shells with high surface area, dual-pore structure, and excellent performance in the adsorption of humic acid is reported. Their synthesis involves templating phenolic resin against wrinkled silica nanospheres, subsequent carbonization under Ar atmosphere, and final release of dual-pore mesoporous carbon shells by etching the silica templates. An additional silica layer was used to protect the phenolic resin from aggregation during carbonization, and its subsequent removal gives the carbon shells a hydrophilic surface, which significantly improves their dispersity in aqueous media. When used as adsorbents for humic acid removal, the as-prepared dual-pore mesoporous carbon shells show superior adsorption performance to activated carbon.

Adsorption of Humic Acid from Aqueous Solution on Different Modified Bentonites

The main objective of this work is the preparation and the characterization of a modified bentonites based adsorbents by intercalation with DMSO and DMF. Modified bentonites were analyzed using thermal analysis (TGA), infra-red analysis (FTIR) and X-ray diffraction. The X-ray results indicate that the geometry of the interlayer space was modified for all bentonites, and the interlayer distances observed are in the order of 1 to 1.41 nm. The adsorption ability and efficiency of different bentonites was tested for the removal of humic acid HA in aqueous solutions. In fact, batch adsorption experiments were carried out under different conditions including the adsorbent dose, the contact time, the initial humic acid concentration, the solution pH, in order to investigate their effects on the retention capacity of the modified bentonites. The maximum adsorption capacity of HA was found to be 16.97 mg/g, 14.65 mg/g, and 11.2 mg/g for DMF-bentonite, DMSO-bentonite and bentonite respectively. In conclusion Modified bentonites showed quite good capabilities in removing HA from aqueous solutions.

Enhanced removal of humic acid from aqueous solution by novel stabilized nano-amorphous calcium phosphate: Behaviors and mechanisms

Stabilized nano-amorphous calcium phosphate (nACP) was prepared using polyethylene glycol as stabilizer to obtain a nanosized amorphous adsorbent. The produced nACP was evaluated by using XRD, FTIR, SEM and X-ray photoelectron spectroscopy (XPS). The sedimentation test demonstrated that nACP exhibited better stability than crystallized hydroxyapatite. The adsorption efficiency of the nACP material for aqueous humic acid (HA) was evaluated from the point of view of medium pH, adsorption time, temperature, and ionic strength, as well as the presences of metal ions. The results of the study showed very good adsorption performance towards aqueous HA. The Sips modeling results revealed that the stabilized nACP adsorbent had a considerably high adsorption capacity (248.3mg/g) for HA at 298K. The adsorption data fitted well into pseudo-second order and Elovich kinetic models. XPS analyses indicated that HA retention on nACP material might be due to the surface complexation reaction between oxygen-containing group and calcium of HA and nACP, respectively. Moreover, the HA adsorption capacity of nACP could still keep more than 86% after four adsorption-desorption cycles. By taking into account all results it was concluded that the nACP adsorbent leveraged its stability in combination with its high uptake capacity to offer a great promise for HA adsorption from water.

Evaluation of natural organic matter adsorption on Fe-Al binary oxide: Comparison with single metal oxides

The adsorption characteristics of three types of standard natural organic matter (NOM) on iron-aluminum (Fe-Al) binary oxide (FAO) and heated aluminum oxide (HAO) under natural surface water condition were investigated using various adsorption isotherms and kinetic models. FAO was synthesized by Fe oxide and Al oxide, mixed using the sol-gel hydrothermal method, and aluminum sulfate was used to make HAO. The amount of adsorbed NOM was increased to 79.6 mg g−1 for humic acid (HA), 101.1 mg g−1 for sodium alginate (SA) in the FAO, but the maximum adsorption capacity of bovine serum albumin (BSA) (461.3 mg g−1) was identified on the HAO. The adsorption of HA, BSA, and SA dramatically increased (>70%) on FAO in 5 min and HA was significantly removed (90%) among the three NOM. Mutual interaction among the adsorbed NOM (BSA) occurred on the HAO surface during adsorption due to formation of monolayer by protein molecules at neutral pH. The pseudo second order clearly represented the adsorption kinetics for both adsorbents. The equilibrium isotherm data of FAO was better exhibited by the Langmuir isotherm model than by the Freundlich isotherm, but HAO was a slightly non-linear Langmuir type. Also, the free energy, enthalpy, and entropy of adsorption were determined from the thermodynamic experiments. Adsorption on FAO was spontaneous and an exothermic process. Fluorescence excitation-emission matrix (FEEM) spectra were used to elucidate the variation in organic components. The results obtained suggests that the significant changes in the surface property of the adsorbent (large surface area, increased crystalline intensity, and fine particle size) were effectively determined by the Fe-synthesized Al oxide mixed using the sol-gel hydrothermal method. The results also suggest that the changes enhanced the adsorption capacity, whereby three NOM were notably removed on FAO regardless of NOM characteristics (hydrophobic and hydrophilic).

Interaction of Humic Acid with Cu/Pb-Zn Tailings of Different Degrees of Weathering

Aggregation of tailings is instrumental for developing a physical environment permitting water infiltration, aeration, and root penetration. Previous research found that microaggregation of Cu-Pb-Zn tailings was stimulated by amendment of composted sugarcane residues. The present study aimed to identify organic functional groups in humic acids (HA) involved in the aggregation of Cu-Pb-Zn tailings, which were considered to be formed from long-term organic matter decomposition in the engineered tailing-soil. The adsorption of HA by the weathered (WT) and freshly deposited (FT) tailings was evaluated at a range of pH conditions in tailing-HA suspension. Humic acid adsorption decreased with increasing pH from 5.0 to 9.0. The FT was found to contain more oxy-(hydr)oxides, particularly poorly crystalline Fe and Al oxy-(hydr)oxides than the WT, which was one of the factors attributing to FT’s higher HA affinity. The Fourier transform infrared spectroscopy analysis of tailing particles before and after HA adsorption indicated that carboxylic and phenolic groups of HA preferentially interacted with tailing mineral particles, probably through ligand exchange, polyvalent cation bridge and electrostatic attraction. The pH-dependent HA adsorption indicated the potential role of functional groups of organic matters in microaggregation of Cu/Pb-Zn tailings. Moreover, the presence of abundant Al/Fe oxyhydroxides promoted organo-mineral interactions. The present findings will contribute toward developing field application to engineer functional Technosols from the tailings by selecting organic matter rich in functional groups.

Preparation and characterization of chitosan/purified attapulgite composite for sharp adsorption of humic acid from aqueous solution at low temperature

In the adsorption treatment of water polluted with humic acid (HA), it is equally important to recover clean water with inexpensive raw materials, mild treatment environments and excellent adsorption capacity. Herein, a composite structured CPA (chitosan-modified purified attapulgite) composed of uniform PA (purified attapulgite) nanorods modified by chitosan was successfully fabricated under acetic acid conditions. Benefiting from the mesoporous structure of the PA nanorods and the carboxyl groups of chitosan, the prepared hybrid CPA exhibited a quick response and excellent adsorption capacity towards HA. The effects of pH, adsorbent dose, adsorption time, initial HA concentration and temperature were systematically studied using PA-90 (PA with purity of 90%) and CPA, respectively. The results show that CPA has a high capture affinity towards HA with a short response time (2min for 80%) and the maximum adsorption capacity could reach 112.07mg/g, which is superior to most results that have been reported. We believe CPA could be considered as an efficient and green heterogeneous adsorbent for the adsorption of humic acid, as well as provide a versatile platform for further development of functional hybrid composites for the adsorption of other pollutants.

Tunable Large Pore Mesoporous Carbons for the Enhanced Adsorption of Humic Acid.

Tunable large pore soft templated mesoporous carbons (SMC) were obtained via the organic self-assembly of resorcinol/formaldehyde with the triblock copolymer F127 and by investigating the effect of carbon precursor to surfactant (p/s) ratio and carbonization temperature on the material characteristics. The p/s ratio and carbonization temperature were varied respectively from 0.83 to 0.25 and from 400 to 1200 °C. The resulting SMCs had various average pore sizes, tunable from 7 up to 50 nm. At lower p/s ratios, the pore size increased, pore size distributions broadened, and pore volumes increased. An increase of hydrophobicity was observed at elevated carbonization temperatures. A 2D hexagonal ordered SMC with a narrow pore size distribution was obtained at a ratio of 0.83. Lower ratios (0.5 and 0.25) transformed into disordered porous carbons containing micropores, mesopores, and even macropores. The SMCs were tested for adsorption of a large organic molecule, humic acid (HA), from water. The material characteristics that significantly affected HA adsorption capacity were pore size and mass % (wt %) carbon. The novel SMCs showed an unprecedented high adsorption of HA in the entire molecular weight distribution range. SMCs with large mesopores resulted in higher maximum adsorption capacities and improved HA adsorption kinetics compared to activated carbon.

腐植粘土複合体に関する研究(第3報) : 粘土による腐植酸の吸収

腐植粘土複合体に関する研究(第3報) : 粘土による腐植酸の吸収

Kinetics Adsorption of Humic Acid from Water onto PVDF Nanofiber

Kinetics Adsorption of Humic Acid from Water onto PVDF Nanofiber

Humic acid adsorption and its role in colloidal‐scale aggregation determined with the zeta potential, surface free energy and the extended‐DLVOtheory

SummaryThe effect of colloidal forces involved in the adsorption of commercial humic acids (HAs) and particle cohesion was studied in the soil of an organic olive grove with the extendedDerjaguin,Landau,Verwey andOverbeek (extended‐DLVO) theory. Total interaction energy was determined from the zeta potential (ζ) and surface free energy, measured under different experimental conditions [natural and hydrogen peroxide (H2O2) organic matter‐free mineral surfaces]. The soil was clayey, dominated by illite and vermiculite. It showed electron‐donor behaviour, with negatively charged surfaces and zeta potential < 0 mV. DecreasingmVin the zeta potential,ζ, curves and electron‐donor component,γ–, when addingHAto natural surfaces showed effectiveHAadsorption, but only when soil organic matter had not been removed previously. Isotherms confirmed adsorption by natural soil (> 2.5 mg C g−1). Because the isotherms showed no relation with temperature, adsorption would be better attributed to weak physical interactions. On natural surfaces withHA, soil particle attraction forces increased slightly (≈50kT) through decreasing soil wettability. However, this effect on total surface energy was overcome largely by increasing electrostatic repulsive energy caused by the adsorption of negatively chargedHA(> 300 kT). TheDLVO‐extended model showed that natural surfaces withoutH2O2treatment or addedHAseem to be the most favourable state for colloidal aggregate stability. We recommend some caution about the type and quality of organic matter added to increase organic carbon in soil.HighlightsWe applied the extendedDLVOmodel to study humic acid adsorption and its effects on soil structure.Adsorption on soil surfaces with their natural organic matter was mostly by weak physical forces.Adsorption increased the total particle interaction energy through an increase in electrostatic repulsion.Adsorption of some types of organic matter might decrease the colloidal stability of aggregates.

Mechanisms of soil humic acid adsorption onto montmorillonite and kaolinite

To explore the adsorption mechanisms of a soil humic acid (HA) on purified kaolinite and montmorillonite, a combination of adsorption measurements, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and isothermal titration calorimetry (ITC) was employed at pH 4.0, 6.0 and 8.0. The adsorption affinities and plateaus of HA on the two clays increased with decreasing pH, indicating the importance of electrostatic interaction. The effects were more significant for kaolinite than for montmorillonite. The substantial adsorption at pH 8.0 indicated hydrophobic interaction and/or H-bonding also played a role. The ATR-FTIR results at pH 8.0 showed that the Si-O groups located at basal faces of the two clays were involved in the adsorption process. For kaolinite, at pH 4.0 and 6.0, HA adsorption occurred via OH groups on the edge faces and basal octahedral faces (both positively charged), plus some adsorption at Si-O group. The exothermic molar adsorption enthalpy decreased relatively dramatically with adsorption up to adsorption values of 0.7μmol/g on montmorillonite and 1.0μmol/g on kaolinite, but the decrease was attenuated at higher adsorption. The high exothermic molar enthalpy of HA binding to the clays was ascribed to ligand exchange and electrostatic binding, which are enthalpy-driven. At high adsorption values, JGHA adsorption by hydrophobic attraction and H-bonding also occurs.