Adsorption Of Humic Acid Research Articles

Humic acid adsorption onto cationic cellulose nanofibers for bioinspired removal of copper(II) and a positively charged dye.

Waste pulp residues are herein exploited for the synthesis of a sorbent for humic acid (HA), which is a major water pollutant. Cellulose pulp was etherified with a quaternary ammonium salt in water thereby introducing positive charges onto the surface of the pulp fibers, and subsequently mechanically disintegrated into high surface area cellulose nanofibers (CNF). CNF with three different charge contents were produced and their adsorption capacity towards HA was investigated with UV-spectrophotometry, quartz crystal microbalance with dissipation, and ζ-potential measurements. Substantial coverage of the CNF surface with HA in a wide pH range led to a reversal of the positive ζ-potentials of CNF suspensions. The HA adsorption capacity and the kinetics of HA uptake were found to be promoted by both acidic pH conditions and the surface charge content of CNF. It is suggested that HA adsorption onto CNF depends on electrostatic interactions between the two components, as well as on the conformation of HA. At pH ∼ 6, up to 310 mg g(-1) of HA were adsorbed by the functionalized CNF, a substantially higher capacity than that of previously reported HA sorbents in the literature. It is further shown that CNF-HA complexes could be freeze-dried into "soil-mimicking" porous foams having good capacity to capture Cu(II) ions and positive dyes from contaminated water. Thus, the most abundant natural polymer, i.e., cellulose could effectively bind the most abundant natural organic matter for environmental remediation purpose.

Humic acid interaction with clay minerals. Modification of the surface properties by calcium presence

The environmental importance of humic acid (HA) is mainly related to soil fertility, but it can also develop some human diseases by its intake as well as prevent calcium assimilation. Physicochemical characterisations of a montmorillonite (Mt) and its thermal treated product (Mt550), to which HA, Ca+2 or both were added, will help to better understand the surface behaviour of the binary or ternary systems. Calcium or HA adsorption produces a decrease of the Mt and Mt550 specific surface area (SSA). X-ray diffraction indicates calcium presence and no entrance of humic acid in the interlayer of Mt, while in the ternary systems (calcium-HA-Mt) a hindrance to the calcium entrance was observed. The opposite behaviour produces the adsorption of HA or calcium on electric charge of both samples. The mean pore diameter (MPD) for Mt increases with Ca+2 adsorption while no change was found after HA adsorption, in contrast to that found for Mt550.

Adsorption of Humic Acid from Aqueous Solution Using Composite Magnetic Microspheres of Chitosan and Quaternary Ammonium Chitosan Derivative

Composite magnetic microspheres of chitosan (CTS) and quaternary ammonium chitosan derivative (HTCC) were prepared by inverse suspension method. Tripolyphosphate (TPP) and glutaraldehyde were used successively to co-crosslink the microsphere matrix. The morphology was analyzed using optical microscopy and scanning electron microscopy (SEM), while the chemical composition was characterized using Fourier transform infrared spectroscopy (FTIR). The adsorption of humic acid (HA) by the composite magnetic microspheres (CHMMs) was investigated in terms of adsorption capacity and kinetics in order to optimize preparation conditions. Both CTS/HTCC mass ratio and crosslinker dosage greatly affected the properties of the microspheres. A batch of CHMMs was prepared when the mass ratio of CTS and HTCC was 1:1 and TPP and glutaraldehyde were17% and 30% of total mass of CTS and HTCC, respectively. These CHMMs were between 150 and 800 μm. 85% HA was able to be removed in 60 min using this proposed absorbent. It was fast and efficient for HA removal from aqueous solution.

The Adsorption Performance of Hybrid PVDF Membrane by HA

Ultrafiltration test was carried out to simulate the pollution performance of humic acid (HA) solution. The HA adsorption properties on membrane surface was studied by static adsorption experiment. The influences of HA concentration on adsorption characteristics were taken into account. And Freundlich isotherm model was used to evaluate of adsorption isotherms.

Sorption of Phenanthrene by Dissolved Organic Matters and their Complex with Iron Oxide Nanoparticles

The environmental behavior of polycyclic aromatic hydrocarbons (PAHs) has attracted great research attention. However, their sorption mechanisms in organo-mineral complexes are still not specific enough. Batch sorption experiments with humic acid (HA) were carried out with iron oxide and their complexes adsorption phenanthrene (PHE) to determine the adsorption characteristics and mechanisms in this study. These results showed that the weakly polar and aromatic fractions of DOM preferentially adsorbed on the surface of iron oxide minerals. The organic matter (OM) binding on the surface of iron oxide played an important role for the adsorption of PHE, where van der Waals interactions and hydrophobic bonding, with ligand exchange at an electrified interface being the dominant reaction of HA adsorption to mineral. The sorption of PHE on organo-mineral complexes was controlled by π-π interactions and hydrophobic interactions.

Adsorption Behavior and Mechanism of Humic Acid on Aminated Magnetic Nanoadsorbent

Adsorptive removal of aqueous humic acid (HA) with aminopropyl functionalized silica coated Fe3O4 nanoparticles was investigated. The adsorption isotherm of HA can be described very well by both the Langmuir and Freundlich models and the theoretical maximum adsorption capacity was 181.82 mg/g. Adsorption kinetics followed both the diffusion-controlled and the attachment-controlled process. HA adsorption increased monotonously with increasing solution pH. The presence of cations in solution, results in augmented HA adsorption. The adsorbent exhibits excellent desorption and regeneration properties. Zeta potential and XPS analysis reveal that electrostatic interaction and surface complexation between protonated amino groups and the disassociated HA molecules are the main adsorption mechanism.

Research on hydrophilicity and hydrophobicity of adsorption of NOM on metal oxide/water interface

Natural organic matter, consisting of 40–60% of humic substances of which the main ingredient is humic acid (HA), is ubiquitous in natural water systems. It poses a potential threat to a water treatment system. Metal oxides in the form of minerals in water are usually considered as carriers of HA. The main adsorption mechanisms of HA on metal oxides have been electrostatic interaction, ligand exchange, hydrophobic interaction, etc.; however, few researches have done on hydrophobic interaction. Therefore, the goals of this study were to investigate the hydrophobic interaction of HA-Fe2O3 complexes and the functional groups of HA under various solution conditions, which can give us a better understanding of the adsorption mechanism. Results showed that the thermal weight loss of HA-Fe2O3 complex, which indicated its hydrophilicity and hydrophobicity, changed regularly when the pH value was varying and the ionic strength maintained constant. While the ionic strength was changing and the pH value maintained constant, the weight loss showed a fluctuating trend. FTIR spectra indicated that the HA functional groups, of which the combined effect finally played a significant role in hydrophilicity and hydrophobicity of HA-Fe2O3 complex, might be hydrophilic hydroxyl (OH), carbonyl (C=O), and hydrophobic alkane (CH2). The change trend of HA adsorption amount with solution conditions coincided with that of weight loss of HA-Fe2O3 complex, which testified that hydrophobic interaction did affect the adsorption of HA on metal oxides.

Effect of Gel Interactions with Dissolved Organic Matter on DGT Measurements of Trace Metals

The technique of diffusive gradients in thin films (DGT) has emerged as a powerful technique for obtaining information on the dynamics of chemical speciation and partitioning of a diverse range of solutes in natural waters. However, there have been concerns that adsorption of dissolved organic matter (DOM) to the diffusive hydrogel could affect measurements, particularly of trace metals. Diffusive gels were exposed to solutions containing DOM from eight different sources and the adsorption of organic matter measured spectrophotometrically, both by its removal from solution and its accumulation on the gel. Both fulvic and humic acid extracted from water adsorbed slightly, but there was much more marked adsorption of humic acid extracted from a peaty soil. There was virtually no evidence of adsorption of DOM in filtered natural waters of various sources, including a lake, river and the porewaters of soils, even when the latter had high concentrations of humic substances. It appears that humic substances in solution, rather than those extractable from the solid phase of soils, do not adsorb markedly to the DGT diffusive hydrogel. DGT measurements of Cd were unaffected if their diffusive gels were pre-exposed to DOM in soil and surface waters, but DGT measurements of Cu were suppressed, especially if the pre-exposure had been to a water containing high concentrations of DOM. This effect on the DGT measurement is likely to be minimised by use of longer deployment times, but further work is required to establish the extent of such effects for a range of realistic conditions.

A further study on adsorption interaction of humic acid on natural magnetite, hematite and quartz in iron ore pelletizing process: Effect of the solution pH value

Humic acid (HA) was the predominant component of the MHA (modified humic acid) binder invented by the authors. This work aims to study the effect of the solution pH value on the HA adsorption onto natural magnetite/hematite/quartz particles and the strength of green pellets with the MHA binder. The SEM images for HA indicated that HA had distinct morphology at different pH values. The adsorption density of HA on the three oxide minerals was significantly pH-dependent and decreased with increasing pH value. The zeta potential values of the magnetite, hematite and quartz particles coated by HA became negative and the isoelectric point of the three natural oxide minerals disappeared in the tested pH value range. The electrostatic interaction and the ligand exchange were the two leading interactions for the HA sorption onto the magnetite/hematite particles, while the small adsorption amount of HA onto the quartz was attributed to the hydrogen-bond interaction. The pH value of the MHA binder solution affects markedly the strength of green pellets from magnetite and hematite concentrates. At pH ~7.0, the HA molecule was expanded and dispersed well and the relatively strong bonding bridges were formed among the iron ore particles. The optimal pH value was founded to be around 7.0 for preparing high-quality iron ore green pellets.

Adsorption Mechanism of Humic Acid on Cu/Fe Bimetallic Particles and Its Influence on the Reduction of Nitrobenzene in Groundwater

Humic acid (HA) is ubiquitous in groundwater, and poses great influence on the biogeochemical controls on, as well as treatment of, contaminants. This study deals with the adsorption of HA on a bimetallic iron system, Cu/Fe, and its influence on the reduction of nitrobenzene in synthetic groundwater. The adsorption kinetics, isotherms, and enthalpy of HA on bimetallic Cu/Fe particles are investigated. Compared with the adsorption of HA on Fe0 particles, the adsorption on Cu/Fe is faster than that on Fe0. The adsorption isotherms of HA at different pH values and temperatures show that the adsorption is always greater on Cu/Fe than on Fe0, and increases when the pH decreases and temperature increases. Moreover, the influences of pH and temperature on adsorption by Cu/Fe are less than those observed in adsorption on Fe0. The adsorption enthalpy on Cu/Fe is lower than that on Fe0, and both adsorptions are spontaneous and endothermic. Characterization of the corrosion products by SEM-EDX, XRD, and XPS reveals the appearance of maghemite (γ-Fe2O3) and magnetite (Fe3O4) on Cu/Fe with HA adsorption, which were more crystalline than those of Fe0, indicating that bimetallic Cu/Fe facilitated the formation of crystalline corrosion products. The adsorption of HA accelerates the release of iron ions but suppresses the reduction of nitrobenzene. Compared with Fe0, Cu/Fe accelerates the adsorption of HA and Cu/Fe increases the reduction of nitrobenzene. The suppression on nitrobenzene reduction increased with the increase in HA concentration.

Humic acid transport in saturated porous media: Influence of flow velocity and influent concentration

Understanding the transport of humic acids (HAs) in porous media can provide important and practical evidence needed for accurate prediction of organic/inorganic contaminant transport in different environmental media and interfaces. A series of column transport experiments was conducted to evaluate the transport of HA in different porous media at different flow velocities and influent HA concentrations. Low flow velocity and influent concentration were found to favor the adsorption and deposition of HA onto sand grains packed into columns and to give higher equilibrium distribution coefficients and deposition rate coefficients, which resulted in an increased fraction of HA being retained in columns. Consequently, retardation factors were increased and the transport of HA through the columns was delayed. These results suggest that the transport of HA in porous media is primarily controlled by the attachment of HA to the solid matrix. Accordingly, this attachment should be considered in studies of HA behavior in porous media.

Effect of humic acid on as redox transformation and kinetic adsorption onto iron oxide based adsorbent (IBA).

Due to the importance of adsorption kinetics and redox transformation of arsenic (As) during the adsorption process, the present study elucidated natural organic matter (NOM) effects on As adsorption-desorption kinetics and speciation transformation. The experimental procedures were conducted by examining interactions of arsenate and arsenite with different concentrations of humic acid (HA) as a model representative of NOM, in the presence of iron oxide based adsorbent (IBA), as a model solid surface in three environmentally relevant conditions, including the simultaneous adsorption of both As and HA onto IBA, HA adsorption onto As-presorbed IBA, and As adsorption onto HA-presorbed IBA. Experimental adsorption-desorption data were all fitted by original and modified Lagergren pseudo-first and -second order adsorption kinetic models, respectively. Weber’s intraparticle diffusion was also used to gain insight into the mechanisms and rate controlling steps, which the results suggested that intraparticle diffusion of As species onto IBA is the main rate-controlling step. Different concentrations of HA mediated the redox transformation of As species, with a higher oxidation ability than reduction. The overall results indicated the significant effect of organic matter on the adsorption kinetics and redox transformation of As species, and consequently, the fate, transport and mobility of As in different environmentally relevant conditions.

Adsorption of humic acid by amine-modified nanocellulose: an experimental and simulation study

The purpose of this study was to evaluate the adsorption of humic acid (HA) by amine-modified nanocellulose. At first, nanocellulose was synthesized by acid hydrolysis, and then was modified by N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane. In the next step, HA and amine-modified nanocellulose were incubated at different conditions (pH, incubation time, temperature, and concentration). Furthermore, we used molecular dynamic (MD) simulation for observation of adsorption at molecular scale. For this purpose, HA and amine-modified nanocellulose were prepared by HyperChem software (Hypercube, Inc., USA), and inserted in Ascalaph Designer 1.8.69 software. Once equilibrium was reached, interactions were simulated for 1,000 ps. Finally, different parameters such as interaction energy, potential energy, and root-mean-square displacement (RMSD) were measured. This study demonstrated that the adsorption of HA was pH-, temperature-, dose-, and time-dependent. Based on simulation results, the interaction energy was reduced, but potential energy and RMSD were increased at the final stage of simulation, which indicated the adsorption of HA. The authors suggest amine-modified nanocellulose for removal of HA in wastewater.

Effect of the chemical structure of anion exchange resin on the adsorption of humic acid: Behavior and mechanism

Polystyrenic (PS) anion-exchange resin and polyacrylic (PA) anion-exchange resin were used to investigate the effect of resin chemical structure on the adsorption of humic acid (HA). Due to the rearrangement of HA to form layers that function as barricades to further HA diffusion, PS resin exhibited 12.4 times slower kinetics for the initial adsorption rate and 8.4 times for the diffusion constant in comparison to that of the PA resin. An HA layer and a spherical cluster of HA can be observed on the surface of the PS and PA resins after adsorption, respectively. The considerable difference in HA adsorption between the PS and PA resins was due to the difference in molecule shape for interaction with different resin structures, which can essentially be explained by the hydrophobicity and various interactions of the PS resin. A given amount of HA occupies more positively charged sites and hydrophobic sites on the PS resin than were occupied by the same amount of HA on the PA resin. Increased pH resulted in an increase of HA adsorption onto the PA resin but a decrease in adsorption onto PS resin, as the non-electrostatic adsorption led to electrostatic repulsion between the HA attached to the resin and the HA dissolved in solution. These results suggest higher rates of adsorption and higher regeneration efficiency for interaction of HA with more hydrophilic anion exchange materials.

Adsorption of humic acid from aqueous solution by hematite: effects of pH and ionic strength

Batch experiments were conducted to investigate adsorption of humic acid (HA) on a commercial hematite. The point of zero charge (PZC) and specific surface area of hematite were 9.17 ± 0.25 and 5.22 ± 0.04 m2 g−1, respectively. The concentrations of HA in solutions were quantified by the ultraviolet–visible spectrophotometer, and molecular weight (MW) was determined by E 2/E 3 (the ratio of absorbance at 250 nm (E 2) and 365 nm (E 3)) measurements of HA in solutions. The adsorption of HA on hematite was strongly dependent on solution pH. More HA was adsorbed at acidic conditions, which was also confirmed by Fourier transform infrared spectroscopy (FTIR) measurements. At pH <9, the E 2/E 3 of the HA remaining in solution after adsorption was higher than its initial value indicating that higher MW fractions of HA were preferentially adsorbed on hematite. At pH >9, no significant change in the E 2/E 3 of the residual HA was observed, so other interactions were involved besides electrostatic interactions. The presence of salt promoted HA adsorption on hematite due to electrostatic interactions. The fractionation of HA during adsorption by hematite would affect the fate of other organic contaminants and heavy metals in natural systems.

Soil PH and Solubility of Aluminum, Iron, and Phosphorus in Ultisols: the Roles of Humic Acid

Soil PH and Solubility of Aluminum, Iron, and Phosphorus in Ultisols: the Roles of Humic Acid

The role of humic acid in stabilizing fullerene (C60) suspensions

Natural organic matter (NOM) has a profound effect on the colloidal stability of discharged C60 nanoparticles in the water environment, which influences the environmental behaviors and risks of C60 and therefore merits more specific studies. This study investigates the effects of humic acid (HA), as a model NOM, on the aqueous stabilization of C60 powder and the colloidal stability of a previously suspended C60 suspension (aqu/nC60) with variations of pH values and ionic strengths. Our results reveal that HA could disperse C60 powder in water to some degree, but was unable to stably suspend them. The aqu/nC60 could remain stable at pH>4 but was destabilized at lower pH values. However, the colloidal stability of aqu/nC60 in the presence of HA was insensitive to pH 3–11, owing to the adsorption of HA onto nC60 and the increased electrosteric repulsions among nC60 aggregates. The colloidal stability of aqu/nC60, with and without HA, decreased as we increased the valence and concentration of the added cations. HA was found to mitigate the destabilization effect of Na+ on the colloidal stability of aqu/nC60 by increasing the critical coagulation concentration (CCC) of Na+, while HA lowered the CCCs of Ca2+ and La3+ probably by the bridging effect of nC60 with HA aggregates formed through the intermolecular bridging of the HA macromolecules via cation complexation at high concentrations of cations with high valences.

Effects of rhamnolipid on the adsorption of Pb2+ onto compost humic acid

Biosurfactants can be applied to improve the micro-environment and efficiency of composting, but their biosurfactant effects on the adsorption of heavy metals and humic acid (HA) remain undefined. This study aims to deal with the effects of biosurfactant rhamnolipid (RL) on the adsorption of Pb2+ onto compost HA at various concentrations, temperatures, and pH values. Adding RL solution influenced the adsorption of Pb2+ onto compost HA without fitting the Langmuir or the Freundlich isotherm. Moreover, Pb2+ adsorption onto compost HA was accelerated by RL at low concentrations until maximum at 40 mg L−1. However, the adsorption was weakened at sufficiently high RL concentration. Furthermore, Pb2+ adsorption was enhanced with increasing pH values and was weakened with rising temperature. This study provides reference for applying biosurfactants in compost.

Adsorptive Removal of Humic Acid by Zirconia Embedded in a Poly(ether sulfone) Membrane

The presence of humic acid (HA) in groundwater threatens aquatic life and human health; for the effective treatment of such pollutants, an advanced/hybrid method is essential. In this work, zirconia embedded in poly(ether sulfone) (ZrePES) mixed matrix membranes (MMMs) has been studied for the removal of HA. Chemical precipitation method was utilized to prepare nano zirconia (ZrO2). The modified PES membrane with nano ZrO2 of 2.5 and 5 wt % were studied. Contact angle measurement and protein rejection studies showed an enhanced hydrophilicity with increase in pore radius for ZrePES membranes. Also, the addition of nano ZrO2 altered the membrane morphology and improved pure water permeability. Batch adsorption experiments revealed that HA adsorption efficiency was higher at pH 2 for ZrePES membranes. The HA uptake capacity of 50.5 mg/g was observed for the 5 wt % ZrePES membrane. Experimental adsorption results showed good agreement with adsorption kinetics model. Ultrafiltration studies showed HA rejection was up to 97% for 5 wt % ZrePES membrane. The effects of natural substances and their impact on HA rejection in ZrePES membrane were also analyzed and discussed.

Peat Water Treatment using Chitosan-Silica Composite as an Adsorbent

The objective of this study is synthesis and characterization of the chitosan-silica composite (CSC) and use them as an adsorbent material for peat water treatment. The resulting composite was characterizedby Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM), X-ray diffraction(XRD), N2 adsorption-desorption isotherm and zeta potential. The sorption experiments were carried out inbatch mode to optimize various parameters such as contact time, dose of CSC, pH and temperature. Inaddition, adsorption isotherms of humic acid onto the CSC were also evaluated with the Langmuir, Freundlichand Sips approximations. Kinetic data were tested using the pseudo-first-order, pseudo-second-order kineticmodels and intra-particle equations. The results from this work showed that the adsorption of humic acid wasfound to increase with increase in contact time and temperature while acidic pH was more favorable for theadsorption of humic acid from peat water. The optimum dosage of CSC was 5 g. Equilibrium data were bestdescribed by the Langmuir isotherm model, with maximum monolayer adsorption capacity of 120.2 mg/g at 25 oC and pH 4.12. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model, with a rate constant in the range of 0.034 - 0.105 g/mg/min, while intra-particle-diffusion were the main rate determining step in the humic acid adsorption process. Thermodynamic parameters data indicated that the humic acid sorption process was non-spontaneous and endothermic under the experimental conditions, with the Gibbs free energy (“Go) in the range of 1.05-3.89 kJ/mol, enthalpy (“Ho) and entropy (“So) of 24.69 kJ/ mol and 69.62 J/mol, respectively and the activation energy was 23.23 kJ/mol. The CSC investigated in this study thus exhibited as a high potential adsorbent for the peat water treatment.