Adsorption Capacity Of Humic Acid Research Articles

Investigating the Adsorption of Humic Acid from Water Using CTS/PAM and CTS/PAM/EDTA Adsorbents

In recent decades, reports from around the globe indicate an increase in natural organic matters (NOMs) in surface waters, which has a negative impact on drinking water purification and causes problems such as the taste and color of water, reducing the amount of dissolved oxygen in water, causing membrane fouling in the filtration process, and acting as a precursor for the formation of an antiseptic by-product. This work used the adsorption process to evaluate the elimination of natural organic compounds in aquatic environments. Ethylenediaminetetraacetic acid (EDTA) as a crosslinker for chitosan (CTS) and N, N-methylenebisacrylamide as a crosslinker for polyacrylamide (PAM) were used to prepare humic acid (HA) adsorbents utilizing a two-step procedure. The FTIR spectroscopy proved the EDTA cross-linking agent was effective with the semicrosslinking CTS/PAM hydrogel. CTS/PAM/EDTA double network (DN) hydrogel exhibited a higher HA adsorption capacity (qe = 107.7 mg/g) than CTS/PAM (qe = 59.3 mg/g) at pH = 7 and an initial concentration of 60 mg·L−1 during 60 min. Also, results demonstrate that CTS/PAM/EDTA DN hydrogels showed faster adsorption kinetics than CTS/PAM.

Highly efficient sorbent utilizing regenerated cellulose as an eco-friendly template for humic acid removal and oil–water separation processes

In this study, a novel and environmentally friendly sorbent was developed utilizing regenerated cellulose (RC) as a renewable resource. The preparation process of the regenerated cellulose hydrogel, following a bottom-up strategy, occurs in an aqueous system and offers the added benefits of temperature-induced gelation and solvent recyclability. The RC/PEI aerogel was prepared through a polyethyleneimine (PEI) modification and di-epoxide crosslinking process, which improves the gel's elastic recovery for the squeezing process and concurrently provides excellent ability to remove humic acid (HA) contaminants. As a result of the HA removal experiment using the RC/PEI aerogel in an aqueous environment, the gel showed an experimental HA adsorption capacity of 124.9 mg/g and qm value of 196.7 mg/g. Furthermore, the prepared RC hydrogel template was successfully transformed into a highly effective oil–water separation sorbent through a hydrophobic alkylated graphene oxide (AGO) coating process. Oil-water separation was carried out using AGO-RC/PEI gel, and it was possible to successfully adsorb the oil and then recover it through the squeezing process. In addition, long-term usability has been validated by demonstrating an oil adsorption capacity of over 84 %, even after ten consecutive reuses.

Performance and mechanism of MnCO3/NaOH co-activated corncob-derived biochar for humic acid removal: XDLVO and DFT calculation

In this study, waste corncobs were used as raw materials to prepare biochar (BC). Under the condition of activator (MnCO3 and NaOH) and pyrolysis (900℃), BC with high specific surface area (1161.99 m2/g) possessed satisfactory performance for the removal of humic acid (HA) in water, with a maximum adsorption capacity of 68.49 mg/g as determined by fitting Freundlich model. HA adsorption capacity was almost unaffected by initial solution pH (1 ∼ 9) and coexisting ions (i.e., Na+, K+, Ca2+, Mg2+, Al3+, CO32–, HCO3–, Cl−, SO42−). The extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory suggested that the van der Waals interaction contributed to attraction between HA and BC, and the density functional theory (DFT) calculation visualized the hydrogen bonding and π-π interaction between HA and BC. Meanwhile, combined with characterization and factor experiments, pore filling and electrostatic interaction also were involved in the adsorption process. This study demonstrated the potential of using waste corncobs for producing BC, providing an effective solution for removing HA and highlighting the importance of waste material utilization in water purification.

Adsorption behaviors and mechanisms of humic acid on virgin and aging microplastics

Because of the wide distribution and strong adsorption ability, microplastics (MPs) in aquatic environment tend to adsorb natural organic matter (NOM). This study aimed to investigate behaviors and underlying mechanisms of adsorption of humic acid (HA) on virgin and aging polyamide 66 (mPA66) and polypropylene (mPP). The kinetic data of HA adsorption on virgin and aging MPs well fitted the pseudo-second-order kinetics model (R2 > 0.95), while the adsorption isotherms better followed the Freundlich models (R2 > 0.92) than Langmuir models. The adsorption process of HA on the virgin and aging MPs was spontaneous and exothermic according to thermodynamics analysis. The effect of ionic strength on adsorption indicated that Ca2+ promoted more adsorption of HA on MPs than Na+ due to the formation of more cation bridge between Ca2+ and HA. With the pH increase, the adsorption capacity of HA first decreased and then increased. Desorption experiment showed that desorption efficiencies of HA adsorbed on virgin MPs were all relatively higher than those on corresponding aging MPs. Particularly, higher desorption efficiencies occurred in ultrapure water rather than in surface water, and HA desorption was apparently pH-dependent but slightly effect by ionic strength. Generally, HA had poor adsorption toward on virgin and aging MPs, but the following desorption efficiencies were relatively high, indicating that the adsorption of HA on virgin and aging mPA66 and mPP MPs tended to be reversible. This result was attributed to physical adsorption process, hydrophobic interactions, polarity and n-π electron donor-acceptor (EDA) interactions. The HA adsorption was mainly dominated by surface area of MPs, instead of crystallinity and functional groups based on XRD patterns, FTIR and XPS.

Effective removal of humic acid by mesoporous Zr-MOF adjusted through SDBS.

Humic acid (HA) in makeup water is one of the important safety issues of high-parameter power plants. Herein, the Zr-based metal-organic frameworks (NH2-UiO-66) was applied to remove humic acid in water. The mesoporous of NH2-UiO-66 was controlled by surfactants sodium dodecyl benzene sulfonate (SDBS) to increase the adsorption of HA. The adsorption of HA at 25°C and pH 7 increased fast at the first 0.5 h and then gradually reached equilibrium after 10 h. The maximum adsorption capacity was 108.93 mg g-1, which removal efficiency was high as 95.0%. The morphology and adsorption properties of NH2-UiO-66 were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), surface charge, Fourier transform infrared (FT-IR), N2 adsorption-desorption, and adsorption test. The adsorption process of HA accorded with the pseudo-second-order kinetics, while the adsorption isotherm conformed to be the Langmuir model and the adsorption was proved to be monolayer adsorption. Adsorption was the spontaneous and endothermic process (ΔG°<0, ΔH°>0). The accessible surface area provided by mesopores on the 5 different Zr-MOFs was the reason for the enhanced HA adsorption capacity. These results provided useful information for effective HA removing and enhanced our understanding of the adsorption mechanism of HA on NH2-UiO-66.

Simultaneous preparation of humic acid and mesoporous silica from municipal sludge and their adsorption properties for U(VI)

In this study, humic acid (HA) rich in various highly active functional groups was first synthesized by hydrothermal method using silica- and organic-rich municipal sludge, followed by mesoporous SiO2 with high specific surface area (SSA) by roasting. The prepared HA and mesoporous SiO2 were then used to adsorb uranium from an aqueous solution. The adsorption behaviors of two adsorbents were investigated using batch experiments, adsorption kinetic and isotherm models, and the adsorption mechanisms were analyzed by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Under the present experimental conditions, the maximum adsorption capacity of HA was 220.26 mg/g. The adsorption process of HA was well described by the pseudo-second-order model and the adsorption isotherm was consistent with the Langmuir model. For mesoporous SiO2, the pseudo-second-order model and the Freundlich model better represent its adsorption behavior. Mechanism analysis showed that various functional groups such as amide, phenol, ether or alcohol on HA provide active sites for uranium adsorption, and mesoporous SiO2 has a porous structure and a large SSA, all of which play an important role in the uranium adsorption performance. By preparing two adsorbent materials from municipal sludge, not only the high-value utilization of sludge is fully realized, but also the environmental benefit is achieved through effective adsorption of uranium.

Comparison of 17β-estradiol adsorption on soil organic components and soil remediation agent-biochar

Steroid estrogen residues (SEs) in the soil have attracted growing attention because of their potential for endocrine disruption. Soil organic matter (SOM) and soil remediation agent-biochar, both have important influences on the fate of SEs in the soil environment. This study compared the adsorption of 17β-estradiol (E2) on wheat straw biochar (W-BC) and cow manure biochar (C-BC) with main SOM components including biomacromolecules (cellulose, collagen and lignin) and humic acids (HA). The impact of pyrolysis temperature (350 °C, 550 °C, and 700 °C) on the adsorption capacity of biochar and different concentrations NaClO oxidation on the adsorption capacity of HA were also investigated. The experimental results showed that the adsorption of E2 by biomolecules conformed to the linear isotherm (R2 > 0.88), and the adsorption of E2 on biochars and HA were well described by the Langmuir and Freundlich isotherm (R2 > 0.94). Meanwhile, the order of the E2 adsorption capacity of sorbents was W-BC > C-BC > HA > lignin > collagen > cellulose. The adsorption capacity of biochar and SOM for E2 increased with the enhancement of aromaticity and hydrophobicity and the reduction of polarity. In addition, the increase of pyrolysis temperature of biochars also promoted the adsorption capacity of E2, while oxidation treatment with NaClO reduced the adsorption capacity of HA to E2. These results deepened the understanding of the adsorption behaviour of E2 on SOM and biochar, and expanded the understanding of the behaviour of SEs in the soil environment.

Nanopowders of Yttria-Stabilized Zirconia Doped with Rare Earth Elements as Adsorbents of Humic Acids.

The aim of the investigations was to use, for the first time, zirconia nanopowders stabilized with yttria (YSZ) and rare element oxides (YSZ-Nd, YSZ-Gd) for removal of humic acids (HA) from aqueous solutions. Nanopowders were synthesized by means of hydrothermal crystallization and characterized using scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) methods and analysis of zeta potential. The adsorption processes analysis was carried out in a series of experiments depending on: initial concentration of humic acids, contact time, pH and mass of the used adsorbent. It was found, that the YSZ-Nd exhibits strong and much higher effectiveness of HA adsorption than YSZ and YSZ-Gd. The HA adsorption rate reached 96.8% for YSZ-Nd dosage of 100 mg, pH 4, and 15 min reaction time and for HA initial concentration equal to 25 mg/L. According to the Langmuir model simulation, the maximum adsorption capacity of HA on YSZ-Nd at pH 4 was calculated to be 2.95 mg/g. Changes in the FT-IR spectra of YSZ-Nd confirmed humic acids’ adsorption on the tested nanopowders, by the presence of additional bands representing carboxylic, alcohol, carbonyl and amino groups in humic acid structure. These functional groups could represent humic acids binding on the YSZ, YSZ-Nd or YSZ-Gd surfaces.

Coal Gasification Fine Slag as a Low-Cost Adsorbent for Adsorption and Desorption of Humic Acid

Coal gasification fine slag (CGFS) is a kind of amorphous silica-alumina solid waste with large surface area and broad pore-size distribution which has the potential to store and release humic acid (HA). In this study, the adsorption capacity of HA onto CGFS tuned by contact time, HA initial concentration, temperature, pH and CGFS dosage was investigated. Experimental results showed that the adsorption kinetics was well described by the pseudo-second-order model and Weber’s intraparticle diffusion model. The adsorption isotherm followed Langmuir monolayer absorption isotherm model with an adsorption capacity (qmax) of 60.67 mg/g (293 K, pH = 7). The thermodynamic parameters indicated that the adsorption was exothermic reaction. In addition, enhanced HA adsorption performance was found at low pH, indicating that electrostatic interaction played an important role between HA and CGFS. Furthermore, desorption and resorption experiment results demonstrated that CGFS had favorable properties for HA-releasing and resorption. The characterization results of CGFS and HA-adsorbed CGFS revealed that hydrogen bonding was one of the adsorption mechanisms. The exploration in our work demonstrated evidently that CGFS is a promising candidate as a suitable medium to store and release HA for soil.

Physicochemical characterization of three natural clays used as adsorbent for the humic acid removal from aqueous solution

Adsorption behaviours of humic acid on three natural clays from Ivory Coast were studied. In order to investigate the adsorption mechanism, characterization of clays and the humic acid–clay complex was conducted by using various analytical methods (attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), specific surface area analysis (BET) and chemical composition). As a result, adsorption process showed that the maximum adsorption capacity of humic acid was achieved at pH = 3 and was found to be to 115 mg/g obtained for the best sample. For all clays, the adsorption was found to be strongly dependent on pH and well fitted by the Langmuir model. In addition, it was shown that the adsorption capacity was linked to the kaolinite content of each sample. The results showed that humic acid adsorption onto clay was made via electrostatic interactions, ligand exchange and hydrophobic interactions. This study showed that clays are valuable adsorbents for the removal of humic acid.

Adsorption of Dissolved Organic Matter with Different Relative Molecular Masses on Inorganic Minerals and Its Influence on Carbamazepine Adsorption Behavior

In this work, sorption experiments were conducted to understand the adsorption characteristics of dissolved organic matter (DOM) of different relative molecular masses on minerals and the effects of their interaction with PPCPs on the adsorption process. This study chose carbamazepine (CBZ) as the target pollutant, quartz sand as the inorganic mineral, and commercial humic acid (HA) as the DOM. We studied the structural characteristics of HA with different relative molecular masses and the impact of their interaction with CBZ on their adsorption based on dialysis experiments and infrared spectroscopy. It was found that large molecular weight fractions of HA, which contain more hydroxyl, aromatic hydrocarbons, and aliphatic hydrocarbons, were mainly hydrophobic substances, while the smaller fractions, containing more alcohols and carboxyl groups, were mainly hydrophilic substances. The combination of HA and CBZ had two major mechanisms, the combination of amino groups of CBZ and polar functional groups in small molecular weight fractions of HA and hydrophobic interactions between hydrophobic groups and aliphatic or/aromatic compounds in large molecular weight HA. The interaction between CBZ and HA resulted in obvious differences in the adsorption of HA or CBZ. When CBZ does not exist, hydrophobic combinations occurred between HA through the hydrophobic components and quartz sand, which also experienced the exchange coordination reaction with the hydroxyl or carboxyl group of HA. In addition, HA adsorbed the aliphatic and hydrophobic macromolecular components. Quartz sand was used to adsorb the large hydrophobic molecules. When CBZ existed, it adsorbed the small molecular weight fractions of HA. The maximum HA adsorption capacity of quartz sand decreased. CBZ could be adsorbed on quartz sand by hydrophobic interaction, van Edward forces, and polarity interactions in the absence of HA. When adding HA, the adsorption increment of carbamazepine on quartz sand was due to the co-adsorption or accumulation of HA and CBZ after their combination.

Removal of humic acid from aqueous solution using polyacrylamide/chitosan semi-IPN hydrogel.

In this study, we provide the first documented removal of humic acid (HA) from aqueous solution using polyacrylamide/chitosan (PAAm/CS) semi-IPN hydrogel. The prepared semi-IPN hydrogel was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The factors effecting HA adsorption performance were individually tested, including initial pH, ionic strength, contact time, initial HA concentration, and temperature. The results indicated that semi-IPN hydrogel was successfully fabricated and can be applied in a wide pH range, from 3 to 9. Low ionic strength effectively enhanced the adsorption capacity. As the ionic strength increased, this enhancement was less obvious but still positive. The adsorption kinetics were fitted to a pseudo-first-order kinetic model, and the adsorption isotherm was described using the Sips isotherm model. The HA adsorption capacity increased with increasing temperature. The maximum adsorption capacity has the potential to attain 166.30 mg g-1, based on the Sips isotherm at 25 °C. Experiments demonstrated that the HA adsorption process can be primarily attributed to electrostatic interactions, and hydrogen bonding was also involved. Facile synthesis and good adsorptive performance indicate that semi-IPN hydrogel can be used for removing HA from water.

Removal of humic acid by fixed-bed electrocoagulation reactor: Studies on modelling, adsorption kinetics and HPSEC analyses

The performance of the fixed-bed electrocoagulation (EC) reactor using aluminium ball anodes has been investigated for the removal of humic acid (HA). Response surface methodology with four factors and three levels (Box-Behnken design) was used to create a set of 29 experimental runs needed for optimizing the operating conditions. Four operational parameters; initial pH (pHi): 4–8, current density (j): 2–10mA/cm2, EC time (t): 5–25min and initial humic acid concentration (CHA): 10–50mg/L, were used as input parameters whereas, percentage dissolved organic carbon (DOC), UV254 and color (VIS436) removals (y1-y3) and the adsorption capacity, qt, (mgDOC/g Al produced or coulomb, y4) were used as responses of the system. Analysis of variance (ANOVA) showed a high R2 correlation coefficients value (R2=0.79) and satisfactory prediction for Quadratic regression models. The experimental results showed that under the optimum conditions of pHi=4, j=6A/m2, t=25min and CHA=30mg/L, the EC process could effectively reduce DOC, UV254, and color as 90.8%, 96.5%, and 99.6%, respectively. Furthermore, the adsorption capacity of HA in the EC process was found to be 1740mgDOC/g Al or 0.162mgDOC/C. The results of the SEC showed that the affinity of the EC process is higher for the large molecular size fractions.

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.

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.

Synthesis of walnut shell modified with titanium dioxide and zinc oxide nanoparticles for efficient removal of humic acid from aqueous solutions.

The main aim of this research was to study the efficiency of modified walnut shell with titanium dioxide (TiO2) and zinc oxide (ZnO) in the adsorption of humic acid from aqueous solutions. This experimental study was carried out in a batch condition to determine the effects of factors such as contact time, pH, humic acid concentration, dose of adsorbents (raw walnut shell, modified walnut shell with TiO2 and ZnO) on the removal efficiency of humic acid. pHzpc of raw walnut shell, walnut shell modified with TiO2 and walnut shell modified with ZnO were 7.6, 7.5, and 8, respectively. The maximum adsorption capacity of humic acid at concentration of 30 mg/L, contact time of 30 min at pH = 3 in an adsorbent dose of 0.02 g of walnut shell and ZnO and TiO2 modified walnut shell were found to be 35.2, 37.9, and 40.2 mg/g, respectively. The results showed that the studied adsorbents tended to fit with the Langmuir model. Walnut shell, due to its availability, cost-effectiveness, and also its high adsorption efficiency, can be proposed as a promising natural adsorbent in the removal of humic acid from aqueous solutions.

The sorption interactions of humic acid onto Beishan granite

Abstract To explore the sorption phenomenon and mechanism between humic acid (HA) and Beishan granite (BsG), the influence of factors such as pH, contact time, ionic strength, temperature, HA concentration and solid-to-liquid ratio were investigated using the batch technique. The sorption process was significantly affected by pH and ionic strength. The maximum adsorption capacity of HA on BsG was approximately 0.9493 mg g −1 at pH = 6.7 and T = 305 K, and the thermodynamic parameters indicated that the sorption process was spontaneous and endothermic. The SEM–EDS results indicated the presence of a certain amount of HA on BsG after sorption with HA. The results of FT-IR spectroscopy and the change in pH demonstrated that ligand exchange–surface complexation may be an important mechanism. BET analysis showed that parts of the HA tended to enter the pores formed by close-packing of BsG particles, and albite and muscovite might have played a role in the sorption process, as indicated by the XRD analysis. Overall, it is speculated that the mechanisms governing the sorption behaviors of HA on BsG are precipitation, ligand exchange–surface complexation and electrostatic interaction. Moreover, the colloidal properties of HA under certain conditions may also significantly affect its sorption interactions with BsG.

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.

Synthesis of magnetic chitosan nanoparticle and its adsorption property for humic acid from aqueous solution

In this study, a novel magnetic chitosan nanoparticle (MCNP) was first prepared by one-step in situ co-precipitation at low temperature and normal atmosphere to remove humic acid (HA) from aqueous solution. Modern characterization analysis showed that MCNP was quasi-spherical in shape with a size of 10nm, and the chemical crosslinking occurred mainly on the hydroxyl groups in chitosan. The increase in solution pH from 4 to 10 caused an obvious decrease in equilibrium adsorption capacity of HA from 29.3 to 7.4mg/L due to the changes of surface charge of MCNP and structural morphology of HA molecules. The adsorption process was attachment-limited under low pH conditions, and both transport-limited and attachment-limited under high pH conditions. The effect of ionic strength was complicated at different initial HA concentrations. Low ionic strength significantly improved adsorption performance and enhanced the interactions between adsorption sites and HA molecules, whereas high ionic strength might weaken adsorption ability because of the negative effects of screening enhanced and competitive adsorption. Common ions existed in neutral natural water sources would not have negative effects on HA removal. The adsorption mechanisms during adsorption process were electrostatic attraction and hydrogen bonding. Regeneration studies indicated that MCNP could be recyclable for a long term. This research extended the potential applicability of MCNP to a great extent and provided a convenient approach to efficiently remove HA from water.

Preparation of novel magnetic chitosan nanoparticle and its application for removal of humic acid from aqueous solution

A novel magnetic chitosan nanoparticle (MCNP) with a BET surface area of 108.32m2/g was prepared using a time and energy saving method at mild condition. MCNP exhibits an excellent ability to adsorb humic acid (HA) from aqueous solution in a wide range of initial HA concentration. The rate of HA adsorption is rapid with more than 50% of HA can be adsorbed in initial 10min, and the equilibrium state can be reached in 60min. The adsorption kinetics data fits well to the pseudo-second-order model, and the adsorption process is transport-limited at low initial HA concentration and attachment-limited at high initial HA concentration. The Langmuir isotherm model fits the equilibrium data better than the Freundlich isotherm model, indicating that the adsorption of HA onto MCNP is a monolayer adsorption. Based on the Langmuir isotherm model, the maximum adsorption capacity of HA is 32.6mg/g at 25°C. Thermodynamic parameters presents that the adsorption of HA onto MCNP is spontaneous and endothermic in nature. The mechanism for the adsorption of HA onto MCNP involves electrostatic interaction and hydrogen bonding. Regeneration studies indicate that MCNP can be recyclable for a long term. All the experimental results suggest that MCNP is a promising adsorbent for treating water that is contaminated with humic acid.