Adsorption Thermodynamic Analysis Research Articles

Two‐Dimensional Copper‐Based Metal‐Organic Framework for Efficient Removal of Methylene Blue from Wastewater

AbstractMetal‐organic frameworks (MOFs) can effectively remove methylene blue (MB) from wastewater due to their abundant adsorption sites and multi‐level pores. In this paper, a copper‐based MOF: {[Cu ⋅ (L) ⋅ (H2O)] ⋅ (DMF)}n (1) (H2L=2‐hydroxyterephthalic acid; DMF=N,N‐dimethylformamide), was synthesized by hydrothermal synthesis method. X‐ray single crystal diffraction showed that a two‐dimensional structure was formed by the carboxyl group of L2− in 1 took μ2‐η1 : η1 bridged two adjacent Cu(II). In this two‐dimensional structure, the coordinated water molecules and hydroxyl group on L2− were distributed on the surface of 1. Thus, it had abundant adsorption sites. The transmission electron microscopy (TEM) of copper‐based MOF nano adsorbent showed that the particle diameter of the nano adsorbent prepared by a cell fragmentation apparatus was about 50 nm. The performance of the copper‐based MOF nano adsorbent in adsorbing MB indicated that the optimal adsorbent dosage was 0.20 g/L and the solution pH was 6. Under the optimal experimental conditions, its maximum adsorption capacity for MB was 143.3 mg/g, which was superior to most MOFs adsorbents. The adsorption thermodynamic analysis showed that the copper‐based MOF nano adsorbent at 25–45 °C was an exothermic (ΔH<0), and spontaneous (ΔG<0) process.

Adsorption of Pb(II) and Ag(I) using iron/manganese oxides modification biochar

The iron/manganese oxides modification biochar (Mn/Fe-biochar) is prepared by pyrolysis of RS impregnated with KMnO4 and Fe(NO3)3 for Pb(II) and Ag(I) removal from wastewater. Pb(II) and Ag(I) adsorption process on Mn/Fe-biochar are exactly analyzed using the Pseudo-second order and Hill model. Pb(II) and Ag(I) adsorption capacity of Mn/Fe-biochar are 88.49 and 134.80 mg/g based on Hill model, respectively. Adsorption thermodynamics analysis indicates the feasible and spontaneous Pb(II) and Ag(I) adsorption on Mn/Fe-biochar. Adsorption mechanism analysis indicates that π-π interaction and surface functional groups contribute to Pb(II) and Ag(I) removal. Density functional theory calculation indicates that binding energies of Pb(II) and Ag(I) interactions with -Mn-O group are the largest than that of the -OH, -COOH, -Fe-O groups, indicating that -Mn-O group plays an important role in Pb(II) and Ag(I) adsorption process. Reusability analysis indicates that Mn/Fe-biochar still has high Pb(II) and Ag(I) adsorption capacity after three cycles. The preliminary economic analysis indicates that the production cost of the Mn/Fe-biochar is estimated as the $4.94/1 kg.

Adsorption of amlodipine on surface-modified activated carbon derived from Delonix regia seed pod

In this study, seed pods of Delonix regia was used to produce activated carbon (DRAC) whose efficiency as an adsorbent in removing amlodipine (AML) from aqueous solution was examined. Adsorbent’s characterization was carried out via Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Boehm titration (BT), and pH point of zero charge (pHpzc). Results obtained from FTIR showed notable peaks attributed to various functional groups present on the DRAC’s surface which must have contributed to the effective adsorptive removal of AML. Images obtained from the SEM analysis revealed that the surface of DRAC possesses various pore sites which enhances the uptake of AML to the adsorbent’s surface. Results obtained from the Boehm titration showed the total value of the acidic group on the surface of the DRAC to be 0.99 ± 0.02 and 0.28 ± 0.01 for the total basic group; this implies that the DRAC’s surface is predominantly acidic as further supported by the value obtained for the pHpzc which was 4.2 ± 0.2. At 303K, a maximum adsorption capacity of 56.5 ± 0.3 mg/g was obtained. It was observed that the Langmuir adsorption model best describes the adsorption data obtained and the data fitted the Pseudo-Second Order kinetics most. Analysis of adsorption thermodynamics showed that the sorption process was exothermic and physisorption defines the nature of the sorption mechanism (Ea< 40 kJmol−1). The cost analysis revealed that producing DRAC is 10 times cheaper as compared to buying commercially-available activated carbon. Hence, the adsorption of AML from aqueous solution using DRAC is efficient as well as cost-effective.

Facile Preparation of Magnetic CuFe2O4 on Sepiolite/GO Nanocomposites for Efficient Removal of Pb(II) and Cd(II) from Aqueous Solution.

CuFe2O4 nanoparticles were synthesized and immobilized on sepiolite fibers and graphene oxide sheets, producing a CuFe2O4/sepiolite/GO (CFSG) nanocomposite via a facile single-pot method. The synthesized nanocomposite was characterized using TEM, FTIR, SEM-EDX, XRD, and TGA techniques to determine its composition, structure, and thermal stability. The adsorptive removal of Pb(II) and Cd(II) heavy metal ions from aqueous solutions was studied using the synthesized CFSG nanocomposite. Adsorption parameters such as CFSG loading, pH, contact time, and temperature were investigated. The CFGS nanocomposite showed a higher Pb(II) removal (qm = 238.1 mg/g) compared to Cd(II) (qm = 14.97 mg/g) in a Pb(II) and Cd(II) binary system. The Pb(II) and Cd(II) adsorption fitted well with the Langmuir model, followed by the pseudo-second-order model, and was found spontaneous. Adsorption thermodynamic analysis showed that the Pb(II) adsorption process was exothermic while Cd(II) adsorption was endothermic. The CuFe2O4 nanoparticles on the CFSG surface could facilitate the adsorption of heavy metal ions through electrostatic interaction and complexation processes.

High biosorption of cationic dye onto a novel material based on paper mill sludge

The valorization of paper mill sludge (PMS) is the main goal of this study. The emissions of PMS continue to increase at global scale, especially from packaging paper and board sectors. The raw sludge was used to prepare an adsorbent to remove toxic pollutants from wastewater, the methylene blue (MB), an organic dye. Firstly, the physico-chemical characterization of PMS was done determining the crystalline phases of PMS fibers, the content of main elements, and the pH zero point charge, which was determined at around pH 7. The adsorption of MB on PMS powder was studied at 18 °C with an agitation of 200 rpm, being the best operating conditions 30 min of contact time, 250 mg L−1 of initial MB concentration and 0.05 g in 25 mL of adsorbent dose. Experimental data of MB adsorption was fitted to Langmuir and Freundlich isotherm equations. The Langmuir model was more accurate for the equilibrium data of MB adsorption at pH 5.1. The PFOM and PSOM were adjusted to experimental adsorption kinetics data, being PSOM, which describes better the MB adsorption by PMS powder. This was confirmed by calculating the maximum adsorption capacity with PSOM, which was 42.7 mg g−1, being nearly similar of the experimental value of 43.5 mg g−1. The analysis of adsorption thermodynamics showed that the MB was adsorbed exothermically with a ΔH0 = − 20.78 kJ mol−1, and spontaneously with ΔG0 from − 0.99 to − 6.38 kJ mol−1 in the range of temperature from 291 to 363 K, respectively. These results confirm that the sludge from paper industry can be used as biosorbent with remarkable adsorption capacity and low cost for the treatment of wastewater. PMS can be applied in the future for the depollution of the effluents from the textile industry, which are highly charged with dyes.

Efficient and selective removal of Pb2+ from aqueous solutions by modified metal-organic frame materials

The broad application of lead in various industries has caused it to accumulate in the environment, with severe implications for human health. There is an urgent need to develop efficient separation materials for treating lead-containing wastewater. In this study, a novel metal-organic framework material (UIO-66-TETA) was prepared using triethylenetetramine (TETA) as a modifier and applied to remove Pb2+ from water. The material was characterized by SEM, EDS, BET, XRD, FTIR, XPS, and other analytical methods. The results indicated that TETA was successfully introduced into the material surface, and the original crystal structure and morphology were maintained. The effects of pH, contact time, initial Pb2+ concentration, and temperature on Pb2+ removal were systematically investigated. Adsorption experimental data were consistent with the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model. The adsorption thermodynamic analysis revealed that the adsorption process was endothermic and spontaneous. UIO-66-TETA had excellent adsorption selectivity for Pb2+ even in a mixed solution containing many other heavy metal ions. Regeneration experiments showed that UIO-66-TETA has good regeneration performance. Based on the results obtained in this work, it can be concluded that UIO-66-TETA can be used as an ideal adsorbent for the removal of Pb2+.

Research on the performance of modified blue coke in adsorbing hexavalent chromium

To solve the issue of hexavalent chromium (Cr(VI)) contamination in water bodies, blue coke powder (LC) was chemically changed using potassium hydroxide to create the modified material (GLC), which was then used to treat a Cr(VI)-containing wastewater solution. The differences between the modified and unmodified blue coke’s adsorption characteristics for Cr(VI) were studied, and the impact of pH, starting solution concentration, and adsorption period on the GLC's adsorption performance was investigated. The adsorption behavior of the GLC was analyzed using isothermal adsorption models, kinetic models, and adsorption thermodynamic analysis. The mechanism of Cr(VI) adsorption by the GLC was investigated using characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). With the biggest difference in removal rate at pH = 2, which was 2.42 times that of LC, batch adsorption experiments revealed that, under the same adsorption conditions, the GLC always performed better than LC. With a specific surface area that was three times that of LC and an average pore diameter that was 0.67 times that of LC, GLC had a more porous structure than LC. The alteration significantly increased the number of hydroxyls on the surface of GLC by altering the structural makeup of LC. The ideal pH for removing Cr(VI) was 2, and the ideal GLC adsorbent dosage was 2.0 g/L. Pseudo-second-order kinetic (PSO) model and Redlich-Peterson (RP) model can effectively describe the adsorption behavior of GLC for Cr(VI). Physical and chemical adsorption work together to remove Cr(VI) by GLC in a spontaneous, exothermic, and entropy-increasing process, with oxidation–reduction processes playing a key role. GLC is a potent adsorbent that can be used to remove Cr(VI) from aqueous solutions.

Effective melanoidin adsorption of polyethyleneimine- functionalised molasses-based porous carbon: Adsorption behaviours and microscopic mechanisms

Sugar industry is an integral part of the food and agriculture sector of the national economy. Cane juice decolourisation is a crucial process in sugar production that directly impacts the final colour value of the sugar. However, the chemicals used in traditional methods may be harmful for food safety. Thus, advanced and effective alternatives methods should be developed to further address the problems on sugar production and quality. In this study, polyethyleneimine-functionalised molasses-based porous carbon (PMPC) was prepared from cane molasses, and was reversely applied to remove melanoidins from cane juice. The melanoidin removal efficiency by PMPC was 91.66% with the adsorption capacity of 550.00 mg/g in the adsorption equilibrium state. From the adsorption thermodynamics analysis, the adsorption process of melanoidins onto PMPC was spontaneous and endothermic. Analysis of the interaction mechanisms demonstrated that the successful adsorption of melanoidins by PMPC was mainly achieved through the electrostatic interations and other weak interactions (hydron-bond interaction), and a melanoidin molecule can be bonded with three to four protonated amine groups of PMPC. In addition, the mass transfer behaviour of the melanoidins adsorbed onto PMPC was determined using the mixed model of external and internal diffusion resistance, and the active-onto-site adsorption model. The results showed the melanoidins adsorbed by PMPC was a multilayer adsorption process dominated by chemisorption. Therefore, PMPC was proved to be an ideal adsorbent for cane juice decolourisation, with the advantages of green, high efficiency, and recyclability.

Dynamic modulation and epoxy functionalization of protein-mediated enoate ester-based hybrid cryogels

The current work is focused on the preparation of protein-mediated poly(hydroxyethyl methacrylate-co-glycidyl methacrylate) copolymer as a self-template for in situ synthesis of hybrid gels. Gelatin, collagen, biotin, and l-arginine were used to create hybrid materials with adjustable swelling and elastic properties. Hybrid cryogels tended to swell more than hybrid hydrogels due to their porous nature. Collaged-doped cryogels had the highest swelling, whereas gelatin-doped hybrids showed enhanced elastic modulus. All hybrid gels exhibited pH-sensitive swelling to controlled release applications depending on the degree of protonation of NH2 and COOH groups in the side chains. At low pH conditions, hybrid cryogels exhibited a higher swelling tendency compared to hydrogels. Ion-stimulus-response of hybrid gels was studied to evaluate the effect of salt concentration and features of ambient ions on swelling. Depending on the polyelectrolytic or polyampholytic nature, the extent of swelling in NaCl and KCl solutions varied according to the charge distribution in the network chains. Hybrid gels showed excellent adsorption performance for methyl orange by the presence of epoxy, hydroxyl groups, amino and carboxyl groups providing sufficient active sites. Adsorption capacity of hybrid cryogels is higher than that of hydrogels. The removal rate 97/%, reached an equilibrium state in a short period, suggested that collagen-doped hybrid cryogels have a potential application to remove dyestuff from wastewater. In relation to the decrease of methyl orange concentration in solution, adsorption process followed pseudo-second-order kinetic model. Avrami model has provided a better experimental-calculated fit and adsorption thermodynamics analysis indicated that the adsorption was a spontaneous process with a negative standard free energy. The characteristic findings from this research will provide insights into the design and application of enoate-ester and protein-based combinations in the food, biomedical and cosmetic fields.

Insights into the Synergistic Removal of Copper(II), Cadmium(II), and Chromium(III) Ions Using Modified Chitosan Based on Schiff Bases-g-poly(acrylonitrile).

Chitosan has received broad consideration as an adsorbent for all pollutants because of its low cost and great adsorption potential. However, its shortcomings, including sensitivity to pH, poor thermal stability, and poor mechanical strength, limit its use. The functional groups of chitosan can be modified to enhance its performance by the grafting technique and Schiff base modification. The grafting process used acrylonitrile (Ch-g-PAN) as a monomer and potassium persulfate as an initiator. After that, the modification via preparation of the Schiff base reaction using salicylaldehyde (Ch-g-Sch I) and P-anisaldehyde (Ch-g-Sch II) was carried out. The synthesized copolymers were detailed and characterized through several spectroscopic and microscopic techniques including infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. In addition, Ch-g-Sch I and Ch-g-Sch II were applied in the removal of different metal ions such as Cu2+, Cd2+, and Cr3+. The maximum adsorption capacity of Ch-g-Sch I for Cd2+ was 183.7 mg g-1 in 24 h, while in the case of Ch-g-Sch II, the maximum adsorption capacity for Cd2+ was improved to 322.9 mg g-1 for the same time. Moreover, adsorption thermodynamic analysis displays that the all ion adsorption process was not random and the pseudo-second-order model fitted with experimental results. Finally, Ch-g-Sch I and Ch-g-Sch II were applied as designs for industrial wastewater treatment with significant efficiency.

Tailored design of a novel composite foam of sodium alginate used for fluoride ion removal.

Fluoride is an essential micronutrient for humans. Nonetheless, when the amount of fluoride ion is greater than required, it will cause skeletal fluorosis and dental fluorosis to threaten human health. In this paper, a series of sodium alginate (SA)-based foam materials are prepared by freeze-drying technique and anchored with the nano-activated alumina (nAl2O3) in the SA to obtain a novel adsorbent of SA-nAl2O3 foam used for fluoride ions removal. The SA-nAl2O3 foam morphology was further explored and confirmed that nAl2O3 existed stably in the SA. The adsorption results showed that the maximal fluoride ion adsorption capacity was 5.09 mg/g with 20 mg/L fluorine solutions at a pH of 3. The adsorption isotherm fitted adequately to the Langmuir isotherm model, which demonstrated that the adsorption process is closer to monolayer adsorption. The adsorption kinetics behavior of SA-nAl2O3 foam was described by a pseudo-second-order model, and the adsorption process occurred by chemisorption. Adsorption thermodynamics analysis emphasized that the adsorption process was spontaneous and endothermic. The main mechanism of the foam is ion exchange. The SA-nAl2O3 foam exhibited excellent regeneration performance and stability after three cycles.

Study on the difference in adsorption thermodynamics for water on swelling and non-swelling clays with implications for prevention and treatment of pneumoconiosis

Excessive inhalation of mineral dust can cause irreversible damage such as diffuse fibrosis of lung tissue. Water-based dust reduction technology can effectively control the dust concentration. The study of the interaction of water-clay mineral dust is helpful to the prevention and treatment of pneumoconiosis by water-based dust removal technology. To better understand the underlying adsorption mechanisms of water molecules on clay mineral dust, the detailed adsorption thermodynamics analysis is necessary. In this paper, we research the thermodynamics of adsorption of water molecules on swelling clay of montmorillonite and non-swelling clay of illite. First, the adsorption isotherms of water molecules on montmorillonite and illite at 293–313 K were measured by gravimetric method. Then, the key thermodynamic variables, including entropy change (Δ S ), surface potential ( Ω ), isosteric heat of adsorption ( Q st ) and variation of Gibbs free energy (Δ G ), were analyzed. Results illustrate that the adsorption amount for water molecules on illite is one order of magnitude smaller than that on montmorillonite, suggesting that swelling clay plays a dominant role in water molecules adsorption process. For water molecules adsorption on montmorillonite, the contribution of secondary adsorption to total adsorption ( a 2 / a ) is always less than 30%. For water molecules adsorption on illite, the contribution of primary adsorption to total adsorption ( a 1 / a ) is greater than a 2 / a at the low pressure region, while a 2 / a can exceed 60% at the high pressure region. The difference in the uptakes of water molecules adsorption on non-swelling and swelling clays is mainly resulted from the difference in primary adsorption on two clays. The Henry’s constant ( K AA ) for montmorillonite is in the range of 21.37–75.08 mmol/g/kPa, which is evidently larger than the K AA values of 0.34–0.98 mmol/g/kPa for illite. Compared with non-swelling clay, the adsorption spontaneity degree for water molecules on swelling clay is higher, and the interaction of swelling clay-water molecules is stronger. Meanwhile, the movement of adsorbed water molecules in swelling clay is more confined than that in non-swelling clay. These findings can offer meaningful guidelines for the prevention and treatment of pneumoconiosis.

Biomass ash pyrolyzed from municipal sludge and its adsorption performance toward tetracycline: effect of pyrolysis temperature and KOH activation.

Large amount of municipal sludge is difficult to handle; its resource utilization is an effective measure. In this study, the municipal sludge from sewage treatment plant was pyrolyzed without gas protection at different temperatures and potassium hydroxide (KOH) concentrations for activation. The pyrolysis products, named biomass ash, with higher surface area and enriched pore structures could be obtained at the pyrolysis temperature of 773K. Moreover, the KOH activation for raw municipal sludge could further increase the surface area of the pyrolysis biomass ash. The maximum specific surface area was 44.71 m2/g, which was obtained under 2mol/L KOH activation before pyrolysis at 773K. And in this situation, the obtained pyrolysis biomass ash as adsorbent showed the maximum adsorption capacity of 50.75mg/g toward tetracycline (TC). Moreover, the TC adsorption onto pyrolysis biomass ash obtained under various conditions followed the pseudo-second-order kinetic model. Adsorption thermodynamics analysis suggested the TC adsorption onto the pyrolysis biomass ash with no pre-activation was mainly due to the multi-molecule heterogeneous adsorption, while the TC adsorption onto pyrolysis biomass ash pretreated through the activation of KOH followed the monomer adsorption mechanism. This different adsorption mechanism was largely related to the pore structure, polarity, and aromaticity of the adsorbent.

Preparation of the Carbonized Zif-8@PAN Nanofiber Membrane for Cadmium Ion Adsorption.

The zeolitic imidazolate framework (ZIF−8)@polyacrylonitrile (PAN) nanofiber membrane was prepared and carbonized for heavy metal cadmium ion (Cd2+) adsorption in aqueous medium. Zinc oxide (ZnO) was first sputtered onto the surface of the PAN electrospun nanofiber membrane to provide a metal ion source. Then, the ZIF−8@PAN nanofiber membrane was prepared via in situ solvothermal reaction and carbonized in a tube furnace at 900 °C under a N2 atmosphere to enhance adsorption performance. The synthesized ZIF−8 particles with polyhedral structure were uniformly immobilized on the surface of the PAN electrospun nanofiber membrane. After being heated at 900 °C, the polygonal ZIF−8 shrank, and the carbonized ZIF−8@PAN nanofiber membrane was obtained. Compared with the nanofiber membrane without being carbonized, the adsorption capacity of the carbonized ZIF−8@PAN nanofiber membrane reached 102 mg L−1, and its Cd2+ adsorption efficiency could be more than 90% under the adsorption temperature of 35 °C and solution of pH = 7.5 conditions. According to the adsorption thermodynamics analysis, the Cd2+ adsorption process of the carbonized ZIF−8@PAN nanofiber membrane was spontaneous. The whole Cd2+ adsorption process was more suitably described by the pseudo second-order adsorption kinetics model, indicating that there exists a chemical adsorption mechanism besides physical adsorption.

Preparation of Magnetic Activated Carbon by Activation and Modification of Char Derived from Co-Pyrolysis of Lignite and Biomass and Its Adsorption of Heavy-Metal-Containing Wastewater

Adsorption with activated carbon (AC) is an important method for the treatment of heavy metal wastewater, but there are still certain challenges in the separation and reuse of activated carbon. The preparation of magnetic activated carbon (MAC) by modifying AC is one of the effective means to realize the separation of AC from solution after the adsorption process. In this work, lignite and poplar leaves were used as raw materials for co-pyrolysis, and the co-pyrolysis char was activated and modified to prepare MAC. The structure and properties were characterized by VSM, N2 adsorption, SEM, XRD, and FT-IR. At the same time, the adsorption performance of MAC on wastewater containing Pb and Cd ions was studied. The results show that the prepared MAC contains Fe3O4, and the saturation magnetization (Ms) of the MAC is 13.83 emu/g; the specific surface area of the MAC is 805.86 m2/g, and the micropore volume is 0.23 cm3/g; the MAC exhibited a good porous structure. When the pH value of the solution was 5, the adsorption time was 120 min, the dosage of MAC was 4 g/L, the initial concentration of Pb ion solution was 50 mg/L, and that of Cd ion solution was 25 mg/L, and the adsorption temperature was 30 °C, the adsorption efficiency of Pb, Cd ions were 84.40 and 78.80%, respectively, and the adsorption capacities were 10.55 and 4.93 mg/g, respectively. The adsorption of Pb and Cd ions by MAC conforms to the Langmuir adsorption model, which is a monolayer adsorption. The adsorption process is mainly chemical adsorption, which can be better described by the pseudo-second-order model. The adsorption thermodynamic analysis showed that the adsorption of Pb and Cd ions by MAC was a spontaneous reaction, and the higher the temperature, the stronger the spontaneity.

Enzyme-enhanced adsorption of laccase immobilized graphene oxide for micro-pollutant removal

Laccase immobilization has been proven to improve the adsorption efficiency for promoting the micro-pollutant removal performance. However, the enzyme-enhanced adsorption mechanism remains poorly investigated. The main objective of this work is to examine the water purification performance of laccase immobilized graphene oxide (Lac-GO), to reveal the enzyme-enhanced adsorption mechanism and to explain the synergy of adsorption and enzymatic degradation, from the views of theory and experiment. Above all, by the appropriate laccase immobilization, the enzyme-enhanced adsorption process formed, and enzymatic degradation was introduced by the change of micromorphology. Then, the laccase immobilization did not affect the GO adsorption behavior, which was dominated by monolayer and homogeneous adsorption, based on the analysis of adsorption thermodynamics and adsorption kinetics theories. Nevertheless, the enzyme-enhanced adsorption showed higher adsorption capacity and greater adsorption rate, because the enzyme is able to degrade the micro-pollutant adsorbed on GO surface, releasing the occupied active sites and delaying the adsorption saturation. Moreover, the calculation of particle diffusion dynamic model clarified that the micro-pollutant diffusion process accelerated after laccase immobilization, since the enzymatic degradation eliminated the diffusion resistance. Afterwards, the GO adsorption and enzymatic degradation exhibited the clear synergy mechanism for micro-pollutant removal, because of the enzymatic degradation enhancement, diffusion resistance elimination and adsorption saturation reduction. In addition, at the optimal operating conditions (laccase concentration of 333.3 mg L−1, Malachite Green concentration of 100 mg L−1, adsorbent concentration of 200 mg L−1, rotation rate of 150 rpm, and temperature of 40 °C), the enzyme-enhanced adsorption process displayed a significant equilibrium adsorption capacity and high micro-pollutant diffusion rate. In final, this study provides an in-depth understanding to improve the adsorption processes for water purification by the unique advantages of enzyme-enhanced adsorption process.

Three-dimensional porous sodium alginate/gellan gum environmentally friendly aerogel: Preparation, characterization, adsorption, and kinetics studies

Three-dimensional porous sodium alginate/gellan gum aerogels (SAG aerogels) were prepared by the method of freeze-drying and ion cross-linking for the removal of methylene blue (MB) in wastewater. The physical morphology and chemical structure of the SAG aerogels were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results revealed that the addition of gellan gum (GG) formed interpenetrating double network structures by ion cross-linking and hydrogen bonding interaction with sodium alginate (SA), which improved the chemical resistance of SAG aerogels and the adsorption capacity of aerogel for MB at a mass ratio of 3:1. The pseudo-second-order kinetic model and Langmuir isothermal model could be used to describe the adsorption process of MB, and the maximum adsorption capacity of the SAG aerogel for MB was 1456.45 mg/g, at 313 K. The adsorption thermodynamic analysis results showed that the adsorption process of MB was spontaneous and exothermic. After 5 adsorption-desorption cycles, the adsorption capacity of SAG aerogel only decreased 1.44% compared with their initial adsorption capacity. The obtained results indicated that the SAG aerogels could be successful and effective used to remove the MB in wastewater.

Rapid synthesis of polyimidazole functionalized MXene via microwave-irradiation assisted multi-component reaction and its iodine adsorption performance

The adsorption applications of MXene-based adsorbents have intensively investigated recently. However, the performance of MXene-based adsorbents has been largely limited owing to their lack of functional groups and adsorptive sites. Therefore, surface functionalization of MXene is an important route to achieve better performance for environmental adsorption. Herein, polyionic liquid functionalized MXene (named as MXene-PIL) was prepared through a multi-component reaction and adsorptive removal of iodine by MXene-PIL was also evaluated. The successful generation of PIL on MXene was confirmed by a series of characterization measurements. Furthermore, the effects of contact time, iodine concentration, environmental temperature and other factors on the adsorption performance of MXene-PIL were investigated. Adsorption kinetic analysis including pseudo-first-order dynamic model, pseudo-second-order dynamic model and Weber-Morris model, adsorption thermodynamic analysis such as Langmuir and Freundlich models and Van’t Hoff equation were used for further analysis the adsorption behavior of iodine by MXene-PIL. We demonstrated that the adsorption capacity could be as high as about 170 mg/g, which is obviously larger than the unmodified MXene and most of other reported adsorbents. Taken together, a simple strategy has been developed for in-situ generation of PIL on MXene and the resultant composites show potential application for adsorptive removal of iodine.

Preparation of Chitosan/Calcium Alginate/Bentonite Composite Hydrogel and Its Heavy Metal Ions Adsorption Properties.

In order to avoid the secondary pollution of the toxic residue of chemical crosslinking agent accompanied by chemical hydrogel adsorbent and enhance the adsorption performance of physical hydrogel, chitosan/calcium alginate/bentonite (CTS/CA/BT) composite physical hydrogel was constructed. The formation mechanism and structure of the composite hydrogel were determined by FTIR, XRD and SEM. Adsorption performances of the hydrogel toward Pb2+, Cu2+ and Cd2+ in water under different condition as well as multi-ion competitive sorption were investigated. The adsorption processes were described with the canonical adsorption kinetics and isotherms models. With the utilization of XPS analysis and adsorption thermodynamics analysis, it was found that the adsorptions were spontaneous physico-chemical adsorptions. The results showed that the maximum adsorption capacity of the hydrogel for Pb2+, Cu2+ and Cd2+ reached up to 434.89, 115.30 and 102.38 mg·g−1, respectively, better than those of other physical hydrogels or chitosan/bentonite composite. Moreover, the composite hydrogel improved the collectability of bentonite and showed a good reusability. The modification of bentonite and the formation of hydrogel were completed simultaneously, which greatly simplifies the operation process compared with the prior similar works. These suggest that the CTS/CA/BT composite hydrogel has promising application prospects for removal of heavy metal ions from water.

Design and characterization of PANI/starch/Fe2O3 bio composite for wastewater remediation

A new synthesized polyaniline/starch/hematite bio composite (PANI/S/Fe2O3 BC) has been studied as an effective material for on-site water remediation. PANI/S/Fe2O3 BC was developed by combining the techniques of co-precipitation and interfacial polymerization in the presence of aqueous starch solution in an acidic medium under ultrasonic irradiation. The nano-morphologies and structures of the designed PANI/S/Fe2O3 BC were evaluated by various techniques relative to PANI and Fe2O3 nanoparticles. In single and multiple systems, PANI/S/Fe2O3 BC was evaluated as a possible adsorbent for different heavy metals, including As3+, Zn2+, and Co2+, relative to PANI and Fe2O3 nanoparticles. In terms of pH value, operating temperature, initial heavy metal concentration, contact time, adsorbent dose and competitive ions in the solutions, the adsorption process was optimized. For 92% overall adsorption of Co2+ and 100% overall adsorption of both As3+ and Zn2+, the adsorption equilibrium was achieved within 60 and 120 min, respectively. In addition, adsorption thermodynamic analysis shows that the As3+ ions adsorption process was not random and the pseudo-second-order fitted with experimental results. Moreover, PANI/S/Fe2O3 BC was evaluated as an antibacterial agent against Gram-negative bacteria (Salmonella typhimurium) and Gram-positive bacteria (S. aureus, Methicillin-Resistant Staphylococcus, Aureus Clinical isolate and Bacillus subtilis). The reported performances indicated that the PANI/S/Fe2O3 BC is a potent candidate for industrial water bioremediation.