Adsorption Of Humic Acid Research Articles

Synthesis and Application of Cobalt-based Metal-organic Framework for Adsorption of Humic Acid from Water

Synthesis and Application of Cobalt-based Metal-organic Framework for Adsorption of Humic Acid from Water

Removal of Disinfection By-Products Precursor (Humic Acid) by Graphene-Silica Composites

Graphene-silica (RGO-SiO2) was successfully synthesized by a simple hydrothermal method. The composites were used to study the adsorption properties of humic acid and disinfection by-product precursors in natural surface water. Compared with reduced graphene oxide (RGO), the specific surface area of the composites doped with silica (SiO2) increased by 31.2% to 259.43 m2/g. RGO-SiO2 could achieve 66.91% adsorption of humic acid (HA), while the maximum adsorption of HA on RGO-SiO2 reached 925.91 mg/g. The adsorption and removal rates of HA by RGO-SiO2 were significantly higher than those of RGO. The whole adsorption process was in accordance with the quasi-secondary kinetic model, the Langmuir isothermal adsorption model. RGO-SiO2 has good adsorption performance for organic matter of different water qualities. RGO-SiO2 has a better removal ability for hydrophobic organics than hydrophilic and nitrogenous organics. The adsorbent was reusable, and the organic removal efficiency of RGO-SiO2 decreased insignificantly after four cycles.

Adsorption of humic acids to lake sediments: Compositional fractionation, inhibitory effect of phosphate, and implications for lake eutrophication

Humic acid (HA) and phosphate interactions play a vital role in the biogeochemical cycle of carbon and nutrients and thus the trophic state of a lake. The adsorption behavior of HAs to sediments in the absence and presence of phosphate was investigated in this study. Three types of HAs were used, AHA from algae-dominated lake sediments, MHA from macrophyte-dominated lake sediments, and a reference HA (RHA) with terrestrial sources. The adsorption capacity of lake sediments was highest for AHA, which can be explained by that AHA contained more carboxyl-containing molecules, proteinaceous compounds and polysaccharides that were preferentially adsorbed by minerals. Phosphate showed a stronger inhibitory effect on MHA adsorption than on AHA adsorption, suggesting that AHA can more effectively replace phosphate adsorbed to sediments. Our findings show that the functional groups of organic compounds control not only their fractionation and burial but also their ability to replace phosphate in sediments. We propose a novel mechanism to explain the legacy effect of lake eutrophication. That is, as lakes shift from a macrophyte-dominated state to more eutrophic, algae-dominated state, increasing algae-derived organic compounds can promote the release of phosphate from sediments, forming a positive feedback loop that sustains internal phosphorus loading and hence lake eutrophication.

Comparative assessment of thermal and thermochemical activation methods of South African kaolinite for effective adsorptive sequestration of humic acid from aqueous media

ABSTRACT Current research has demonstrated that the adsorption capacity of raw kaolin is considerably low. Advances in kaolin activation for enhanced utility and improved adsoptibility of pollutants include thermal treatment, acidification, or combined treatment. In this work activation of South African kaolinite with sulfuric acid and calcination is studied. Comparing the FTIR spectra of the activated kaolin i.e thermochemical treated kaolin (HAK) and thermal treated kaolin (HK) with raw kaolin the following main observation were noted; the bands attributable to Si-O stretching vibration (1023 and 1095 cm−1) increased in intensity by 61 and 59% for HK and HAK, respectively. Increasing the humic acid (HA) concentration (0.5–20 mg/L) increased the HA uptake for both adsorbents, HK increased from 0.52 to 0.75 mg/g while HAK increased from 0.59 to 0.86 mg/g. The adsorption of HA was delineated better by a pseudo-second-order model in both cases (Qe = 0.810; 0.793 mg/g for HK and HAK, respectively). From the synchronous spectra, two auto peaks were observed at (1650;1650) and (3246;3246) indicating concurrent and similar HA adsorption behavior on either of the adsorbents. From the results, it can be concluded that activation of kaolin improved its adsoptibility capacity for HA.

Ultrafast removal of humic acid by amine-modified silica aerogel: Insights from experiments and density functional theory calculation

The efficient and rapid treatment of natural organic matter is a difficult task in wastewater treatment, especially for highly concentrated humic acid (HA). In this work, using agricultural waste rice husk ash (RHA) as silica source, a facile one-pot sol–gel synthesis was introduced to prepare an novel adsorbent amine-modified silica aerogel (AMSA) for HA removal. The characterization demonstrated the amine groups were successfully grafted on the surface of AMSA. Even at the high concentration (2000 mg/L) low adsorbent dosage (1 g/L) and short reaction time (15 min), the AMSA exhibited an excellent adsorption capacity (1749.7 mg/g) on adsorption of HA, increased 184.2 times compared with the pristine silica aerogel (SA). The removal efficiency of HA increased from 84.0% to 92.0% when the pH of the solution increased from 3.0 to 5.0, and it remained at a high level when the pH increased from 5.0 to 9.0. The removal of HA on AMSA shows the high stability in the exist of different interfering cations (Na+, NH4+, Mg2+) and anions (Cl−, CO32−, and SO42−) with different concentrations. Kinetic experiments showed that the adsorption process fit the pseudo-second-order kinetic model and the isotherms of the adsorption process matched the Freundlich model, indicating the non-homogeneity of the adsorption process. According to density functional theory (DFT) calculation results, the AMSA has the most negative adsorption energy −273.15 kCal/mol, indicating that this configuration is the most stable. The electrostatic interaction, O–H…N hydrogen bonding, and self-aggregation were the main adsorption mechanism for the rapid and high capacity adsorption of HA by AMSA.

New insights into the cooperative adsorption behavior of Cr(VI) and humic acid in water by powdered activated carbon

Chromium and humic acid often co-exist in wastewater and source waters, and the removal of chromium through sorption by activated carbon may be greatly influenced by humic acid. In this study, we systematically evaluated concurrent adsorption of humic acid (HA) and hexavalent chromium (Cr(VI)) in water by powdered activated carbon (PAC) and further, the effect on conversion to trivalent chromium (Cr(III)). Adsorption of both HA and Cr(VI) was significantly enhanced in the dual adsorbate system as compared to treatments with HA or Cr(VI) alone. The removal of HA increased by 16.0% in the presence of 80 mg/L Cr(VI), while the removal of Cr(VI) similarly increased with increasing levels of HA. However, the promotion effect of HA was found to decrease with increasing pH. With HA at 20 mg/L, removal of Cr(VI) increased from 40.09% to 70.12% at pH 3, which was about twice the increase at pH 10. The cooperative adsorption mechanism was explored using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), Raman spectroscopy, Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). Comprehensive analysis of spectra suggested that the mutual promotion between HA and Cr(VI) adsorption was attributable to the formation of Cr(VI)-HA and Cr(III)-HA complexes that were readily adsorbed on the PAC surfaces. The higher HA concentrations increased the reduction of Cr(VI) to Cr(III), which was likely due to the electron transfer provided by the functional groups such as -CO, -OH and -COOH in both PAC and HA. At pH 3, 99.1% of Cr adsorbed on the PAC surface was in the form of Cr(III). These findings imply that the interactions between Cr(VI) and HA in the process of water treatment by PAC provides additional and synergistic benefits, leading to a greater removal of chromium.

Adsorption of humic acid onto chitosan polyvinyl alcohol blend membrane from solution and second adsorption toward copper ions

Adsorption of humic acid onto chitosan polyvinyl alcohol blend membrane from solution and second adsorption toward copper ions

INFLUNCE OF CULTIVARS, PLANT GEOMETRY, HUMIC ACID AND THEIR INTERACTIONS ON GROWTH AND YIELD OF NIGER (Guizotia abyssinicia Cass.) CROP

INFLUNCE OF CULTIVARS, PLANT GEOMETRY, HUMIC ACID AND THEIR INTERACTIONS ON GROWTH AND YIELD OF NIGER (Guizotia abyssinicia Cass.) CROP

Natural organic matter removal by electrospun nanofiber membranes coated with heated aluminum oxide particles

The removal of natural organic matter (NOM) from water was studied using polyacrylonitrile (PAN) electrospun nanofibrous membrane (ENM) coated with HAOPs (heated aluminum oxide particles). The removal efficiencies of virgin PAN and HAOP-coated PAN were examined and the suitability of PAN as a support material for HAOPs was studied.The membranes were characterized with Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscope and energy dispersive X-ray spectrometer (SEM-EDS) as well as X-ray photoelectron spectroscopy (XPS). Several analytical techniques were applied to both the feed and the permeate to assess the effectiveness of NOM removal.In filtration of lake water, HAOPs efficiency in NOM removal was 56% measured by UV254 absorbance, but when it comes to virgin PAN membrane the removal efficiency was only 13%. In case of filtration of NOM's high molecular weight component, such as humic acid (HA), the rejection rate of HA was maintained above 97% of aromatic compounds of NOM, and above 43% of total organic carbon (TOC).Additionally, HA adsorption by HAOPs were fitted to isotherm models such as Langmuir and Freundlich models. The results showed that Langmuir model could fit the data better than Freundlich model. The kinetics of HA adsorption by HAOPs were also fitted to the pseudo-first order and pseudo-second order and for the initial HA concentration of 19.9 mg/L the pseudo-first order equation fitted the experimental data better with correlation coefficient of R2 = 0.8336.The results demonstrate that PAN ENM filtration has the potential to be employed as a pretreatment in water treatment and HAOP-coated PAN ENM can significantly enhance the removal of NOM.

Adsorption of Fulvic Acid and Water Extractable Soil Organic Matter on Kaolinite and Muscovite

The interaction of organic matter with mineral components of the solid phase of soils is the most important process that regulates the cycle and balance of carbon in the biosphere. The adsorption of humic acids on minerals is accompanied by their fractionation in size, composition, and amphiphilicity, thus decreasing their heterogeneity. Despite a strong interest in studying the regularities and mechanisms of the interaction between natural organic matter and layered aluminosilicates, it is necessary to take into account the natural diversity of soil organic matter, adsorption conditions, and mineral composition. This study was designed to investigate the adsorption regularities of fulvic acid (FA) and water-extractable organic matter (WEOM) isolated from horizon H of peaty-podzolic-gleyic soil on kaolinite and muscovite. Sorbates and sorbents were examined by the following methods: high-pressure size exclusion chromatography (HPSEC), high-performance liquid chromatography (HPLC), and potentiometric titration. The specific surface areas of the sorbents were determined by the sorption of N2 molecules. We found that hydrophobic components of FA and WEOM are mainly adsorbed on mineral surfaces. The adsorption of FA and WEOM on kaolinite and muscovite is followed by decreased hydrophobicity of organic matter and decreased heterogeneity of its amphiphilic properties in an equilibrium solution. At pH levels around 6, sorption of organic matter from FA solution containing 19% and 81% hydrophilic and hydrophobic components, respectively, onto kaolinite and muscovite occurs mainly due to hydrophobic components. Hydrophobic interactions on siloxane surfaces are the main mechanism to fix FA on both minerals. Kaolinite adsorbs slightly more organic carbon per unit area than muscovite. The adsorption of WEOM from a solution with 41% hydrophilic and 59% hydrophobic components results not only from hydrophobic and hydrophilic components but also from hydrophobic and electrostatic interactions and depends on pH. The most hydrophobic fractions of organic matter are adsorbed from the hydrophobic components on the surface of both minerals. Under conditions of the performed experiments at pH < 5, more WEOM is adsorbed on muscovite than on kaolinite.

Coprecipitation of humic acid and phosphate with Fe(III) enhances the sequestration of carbon and phosphorus in sediments

The coprecipitation of dissolved organic matter (DOM) and phosphate with Fe(III) at the sediment-water interface plays an important role in the biogeochemical cycle of organic carbon (OC) and phosphorus (P) in aquatic ecosystems. However, studies remain limited towards understanding the strength of ternary DOM-phosphate-Fe(III) coprecipitation in sequestering OC and P. Here, we investigated the behaviors of humic acid (HA) and phosphate during their coprecipitation with Fe(III) and compared the coprecipitation behaviors with those during the adsorption process. The results showed that the coprecipitation of HA and phosphate with Fe(III) enhanced as pH decreased or initial Fe(III) concentrations increased. The presence of phosphate had a moderate inhibition effect on HA coprecipitation, leading to 3%–37% of reduction in precipitated HA. Changes in optical properties of DOM (i.e., SUVA254, E2/E3, and fluorescent components) showed that macromolecular, aromatic molecules preferentially coprecipitated, and this selectivity pattern was not influenced by the presence of phosphate. Compared to the adsorption of HA and phosphate to goethite, coprecipitation with Fe(III) displayed stronger binding ability, sequestering more than10 times of HA and phosphate, and was more efficient in sequestering protein-like compounds. The inhibitory effect of phosphate on HA sequestration was weaker during coprecipitation than during adsorption. Moreover, coprecipitation led to a lower degree of compositional fractionation of HA than adsorption, which may be explained by that inclusion, an important pathway for coprecipitation, has low selectivity for chemical compositions. Collectively, our results demonstrate that coprecipitation plays a crucial role in sequestering both OC and P in aquatic systems, arguing that the formation of ternary OC-Fe-P coprecipitates may be an important pathway for sequestering OC and P over a long term and reducing the internal loading of P in eutrophic lakes.

Enhanced adsorption of humic/fulvic acids onto urea-derived graphitic carbon nitride

Since humic substances (HSs) can cause environmental problems, their elimination has been attracting more and more concerns. In this study, we investigated HSs adsorption onto urea-derived graphitic carbon nitride (CNU) and elucidated adsorption mechanisms (i.e. heterogeneity, interface rearrangement, and multiple interactions). The adsorption capacity of CNUs was enhanced as increasing calcination temperature and time. Among CNUs, CNU-575–3 showed the highest adsorption capacity; the maximum adsorption capacities for humic acid (HA) and fulvic acid (FA) were 164.06 mg C/g, 14.61 L/cm·g, 91.12 mg C/g, and 5.34 L/cm·g, respectively. The adsorption affinity of CNUs mainly correlated with the amount of amino groups, and that of HSs components was dependent on aromaticity due to π-π interactions. More specifically, terrestrial humic-like and fulvic-like components within HA and FA showed the greatest adsorption affinity, respectively. HSs adsorption was remarkably affected by pH, alkali metals, and alkali earth metals via electrostatic interactions, H-bonding, cation bridge, and configurational effect. In addition, the adsorption of Elliott soil HA (ESHA) and the landfill leachate concentrate by CNUs was also highly efficient. This study shows the great promise of CNUs for HSs adsorption in waters and wastewaters.

Competitive and multiple adsorption of humic and fulvic acids on spherical silver and gold engineered nanoparticles in aqueous media: A first-principles study

Experimental studies have confirmed that engineered nanoparticles have different shapes such as cylindrical and spherical just to mention a few. The different shapes of engineered nanoparticles are likely to interact with natural organic matter in the aquatic environment. It is evident that when two or more different NOM’s adsorbed on molecules are going to compete for active sites. To understand the competitive and multiple adsorptions of humic acid (HA) and fulvic acid (FA) on spherical silver and gold engineered nanoparticles in aqueous media, dispersion-corrected density functional theory (DFT-D) has been used. For this purpose, HA and FA were used as model compounds for NOM. The results provide evidence of molecular interactions, competition for adsorption sites between NOM’s and Ag and Au spherical engineered nanoparticles, which are critical to understanding engineered nanoparticles behaviour and toxicity in the natural environment. The adsorption energy results of the mixtures of four HA and FA on Ag and Au spherical engineered nanoparticles have the highest adsorption energy of −1.94 eV and −3.40 eV respectively. Global reactivity descriptors such as ionization potential, electron affinity, chemical potential, hardness and electrophilicity index which give insights on adsorption of FA and HA on Ag and Au spherical engineered nanoparticles were calculated.

Insights into metal-organic frameworks HKUST-1 adsorption performance for natural organic matter removal from aqueous solution

Natural organic matter (NOM) has rich halogenation reactive sites, therefore acts as the main precursor of disinfection byproducts (DBPs) in the chlorine disinfection process during drinking water treatment. In this research, high-quality metal-organic framework HKUST-1 is rapidly synthesized by a solvothermal method, and we are the first to report adsorption of aqueous humic acid (HA), representing NOM, and its adsorption behavior, influencing factors, and recycling capability. The crystalline HKUST-1 possessed a microporous framework with a high 1385 m2/g specific surface area, and three-dimensional structure as characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM). 99% removal of 5 mg/L HA was observed at pH 5.8, room temperature, and 0.6 g/L HKUST-1. The maximum capacity was 14.42 mg HA/g HKUST-1 at room temperature. The Langmuir adsorption isotherm, quasi-second-order kinetic model, and thermodynamic parameters accurately describe the spontaneous and disorderly endothermic adsorption of HA by HKUST-1. The desorption regeneration process was accomplished by washing HKUST-1 with NaOH and calcination; it showed that HKUST-1 was viable in three regeneration cycles. The mechanism of HA adsorption by HKUST-1 is electrostatic and synergistic interaction between π-π bonding, and hydrogen bonding. HKUST-1 is a potential treatment strategy to remove NOM.

Investigating the role of the morphology of the Zn-Al LDH on the adsorption of humic acid from aqueous solutions.

Flake Zn-Al layered double hydroxides (FLDHs) and microspheres of LDH (MLDHs) were fabricated with a simple hydrothermal method to investigate the role of the morphology of Zn-Al LDH for humic acid (HA) adsorption from synthetic solutions and natural water. The effect of process variables, i.e. contact time, initial concentration of HA, pH, and competitive ions on the adsorption was investigated. HA removal mechanism was also studied. The two adsorbents exhibited different adsorption behaviors for HA in the presence and absence of background ions, which may be highly correlated with the various adsorption mechanisms involved. Comparison of the HA removal capacity of these two adsorbents implies the superior adsorption capability of FLDH for removal of HA from synthetic solutions (9.5 mg/g), while the adsorption capacity of MLDH was higher for natural organic matters present in natural water samples containing co-existing ions (8.9 mg/g). The pseudo-second-order kinetics model and Longmuir isotherm model could adequately interpret the HA adsorption process for the studied adsorbents. Both LDHs exhibited good regeneration and recycling abilities.

Ultrasonic Assisted and Neural Network Model for Adsorption of of humic acid (HAs) by Synthesised CM-β-CD-Fe3O4NPs from Aqueous Solutions

ABSTRACT In the present study, the applicability of CM-β-CD-Fe3O4NPs synthesis for eliminating humic acid rapidly from aqueous solutions. Identical techniques including BET, FT-IR, XRD and SEM have been utilised to characterise this novel material. The investigation showed the applicability of CM-β-CD-Fe3O4NPs as an available, suitable and low-cost adsorbent for the proper deletion of humic acid from aqueous media. Also, the impacts of variables including initial humic acid (HA) concentration (X1), pH (X2), adsorbent dosage (X3) and sonication time (X4) came under scrutiny using central composite design (CCD) under response surface methodology (RSM). The experiments have been designed utilising response surface methodology. In this current article, the values of 12 mg·L−1, 0.03 g, 7.0, 4.0 min were considered as the ideal values for humic acid (HA) concentration, adsorbent mass, pH value and contact time, respectively. The kinetics and isotherm studies proved the appropriateness of the second-order and Langmuir models for the kinetics and isotherm of the adsorption of humic acids (HAs) on the adsorbent. The adsorbent was proved to be recyclable more than once. Since almost 99.5% of humic acids (HAs) were deleted with ideal adsorption capacities of 105 mg·g−1 for humic acids (HAs). The use of artificial neural network model in predicting data with Levenberg–Marquardt algorithm, purelin or a linear transfer function at the output layer and tansig or a tangent sigmoid transfer function in the hidden layer with five neurons was helpful for deletion of humic acid (HAs), MSE (mean square error) of 0.33 for humic acid (HA) removal by CM-β-CD-Fe3O4NPs. The overall results confirmed that CM-β-CD-Fe3O4NPs could be a promising adsorbent material for humic acid (HA) removal from aqueous solutions.

Phosphorus and humic acid extraction from fermentation liquor of ferric phosphate sludge via layered double hydroxides: Efficiency and interaction mechanism

Iron salts are increasingly employed in wastewater treatment worldwide, generating ferric phosphate sludge with low phosphorus (P) bioavailability. The fermentation of ferric phosphate sludge effectively transfers P from the solid phase to the liquid phase and simultaneously releases high contents of ferrous cations (Fe2+) and humic acids (HA) into the sludge liquor. This study aimed to extract P from simulated and real sludge fermentation liquor via Mg/Al layered double hydroxide (LDH), evaluate the impact of co-existed Fe and explore the interaction mechanism between phosphate and HA adsorption. The Fe influence experiments explored the suitable organic matter concentration range for the LDH adsorbent to extract P without the concurrent precipitation of iron compounds. Thus, the residual ferrous species in sludge liquor can be reused as a flocculant. Moreover, the analysis of the adsorption kinetics of phosphate at 25, 35, and 55 °C showed that increasing temperature accelerated the phosphate adsorption rate but had minor effects on the P adsorption capacity. HA and phosphate were jointly adsorbed onto Mg/Al LDH. Investigations on isotherm, kinetics, and mechanism suggested that phosphate anions have a competitive advantage in the ion exchange process but are hindered by large-molecular-weight HA in surface adsorption because of limited adsorption sites. Subsequent adsorption experiments in sludge liquor and nutrient release test confirmed the possibility of using Mg/Al LDH to simultaneously recover P and organic matters from sludge fermentation liquid based on its stable P adsorption performance and intercalated anion slow-release property.

Fabrication of Nano Zero valent Iron/Biopolymer Composite with Antibacterial Properties for Simultaneous Removal of Nitrate and Humic Acid: Kinetics and Isotherm Studies

This investigation compared the adsorption behavior of humic acid (HA) on cellulose, chitosan and nano zerovalent iron/chitosan (nZVI/chitosan). Results show that nZVI/chitosan is very effective in the adsorption of HA from aqueous media. The feasibility of using nZVI/chitosan as an adsorbent for the simultaneous removal of nitrate and HA from aqueous media was also studied. Structural analyses of the samples were identified by TEM, FT-IR, EDX, XRD and N2 isotherms. The effects of pH, amount of composite, nitrate concentration, HA concentration and contact time and their interactions on responses were explored by central composite design (CCD) and response surface methodology (RSM). The optimal conditions of pH (5.5), adsorbent amount (0.098 g), reaction time (27 min) and initial concentrations (110 mg/L for nitrate and 30 mg/L for HA) were obtained from the desirability function. The adsorption properties of the resulting nanocomposite toward nitrate and HA were investigated through kinetic and isotherm studies. The adsorption kinetics was found to fit the pseudo-second order model. The obtained results indicate that nitrate uptake fitted well with Langmuir model while Freundlich isotherm was the best model for describing the multilayer uptake of HA from aqueous solutions. Moreover, nZVI/chitosan nanocomposite illustrates a very high antibacterial activity against pathogen bacteria strains such as Staphylococcus aureus ATCC 25935, ATCC 25923, and Pseudomonas aeruginosa ATCC 27853. The findings reported in this investigation highlight the potential of using nZVI/chitosan as a promising adsorbent for the simultaneous removal of nitrate and HA from aqueous solutions.

Surface Properties of Nanoparticles Dictate Their Toxicity by Regulating Adsorption of Humic Acid Molecules

In an aquatic environment, nanoparticles (NPs) acquire coatings of natural organic matter (NOM) that alter the fate and toxicity of NPs. However, the essential relationship between engineered NP properties and NOM assemblage that determines how NPs are modified and behave at biological interfaces remains unclear. Herein, we use a complementary experimental and molecular dynamics approach to elucidate the mechanisms underlying adsorption of humic acid (HA) on NPs of different surface properties and effects on NP interactions with bacteria. Our results demonstrate that hydrophobic and positively charged NPs are more capable of adsorbing HAs in unique standing or lying conformations that expose particular groups to modify NP properties. In particular, HA adsorption increases effective NP size, reduces NP’s hydrophobicity, and reverses NP’s surface charge. As a consequence of HA adsorption, the binding of NPs to bacteria is sterically hindered and suppressed by electrostatic repulsion between negatively charged groups in adsorbed HAs and lipopolysaccharide on the bacterial membrane. The toxicity of NPs is mitigated as seen by reductions of NP association with bacteria and NP-induced membrane damage. These findings provide compelling explanations on the cascading events from dictation of HA adsorption by engineered NP properties to how the modified NP surfaces change their toxicity.

Prediction and optimization of adsorption performance of MC@MgAl-LDH for the removal of humic acid from aqueous solution: BBD model and mechanism

In this study, enteromorpha was used as a raw material, magnetic biochar (MC) was prepared by impregnation pyrolysis method. Enteromorpha magnetic biochar MgAl layered double hydroxide composite material (MC@MgAL-LDH) was then prepared by hydrothermal method for the adsorption study of removing humic acid (HA) from water. The effects of different influencing factors on the adsorption of HA by MC@MgAl-LDH were studied using BBD model. The results indicated that the adsorption process can be fitted well by the pseudo-second-order kinetic model and the Freundlich isotherm model. The maximum saturation adsorption capacity of MC@MgAl-LDH for HA was 5.85 ​mg ​g−1 ​at 298.15 ​K. The absorbent was regenerated by thermal regeneration method, and the removal rate remained above 90% after 5 times of reuse. Electrostatic attraction and complexation were the main mechanisms for the removal of HA by MC@MgAl-LDH. Studies showed that the material presented excellent adsorption performance, pH wide adaptability and reusability.