ZnO/Cassava Starch-Based Hydrogel Composite for Effective Treatment of Dye-Contaminated Wastewater

Industrial expansion has increased the discharge of contaminated wastewater. Wastewater can be treated by adsorption with petroleum-based hydrogels but the materials are not biodegradable and therefore cause secondary toxic waste. In this work, hydrogel composites are prepared based on non-biodegradable polyacrylamide and biodegradable materials of cassava starch (CS) and poly(vinyl alcohol). The effect of CS content on the porous structure is studied. The highest water absorption capacity of 74 g g⁻¹ is obtained from a hydrogel 30 wt% of CS. Within 4 h, the hydrogel effectively adsorbs the cationic dyes methylene blue (MB) and crystal violet, and the anionic dyes congo red and reactive orange. The maximum adsorption capacity toward MB is 993 mg g⁻¹. Experimental data indicate a monolayer adsorption via chemisorption. Silica-coated ZnO photocatalyst particles are synthesized via a sol–gel method and coated on the outer surface of the hydrogel. Under sunlight, the hydrogel composite degrades almost 90% of adsorbed dye. The hydrogel composite is capable of effective photodegradation for at least three cycles under artificial UV irradiation and four cycles under sunlight, but adsorption capacity remains higher than 80% at the eighth cycle. The hydrogel composite also shows antibacterial activities, indicating an additional beneficial property for industrial wastewater treatment.     

Synthesis and electrochemical capacitance of core-shell poly (3,4-ethylenedioxythiophene)/poly (sodium 4-styrenesulfonate)-modified multiwalled carbon nanotube nanocomposites

A noncovalent method was used to functionalize multiwalled carbon nanotubes with poly (sodium 4-styrene sulfonate). And then, the core-shell poly (3,4-ethylenedioxythiophene)/functionalized multiwalled carbon nanotubes (PEDOT/PSS-CNTs) nanocomposite was successfully realized via in situ polymerization under the hydrothermal condition. In the process, PSS served for not only solubilizing and dispersing CNTs well into an aqueous solution, but also tethering EDOT monomer onto the surface of CNTs to facilitate the formation of a uniform PEDOT coating. Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) were used to characterize the resultant PEDOT/PSS-CNTs. In addition, the PEDOT/PSS-CNTs nanocomposite (50 wt.% PEDOT) had a specific capacitance (SC) of 198.2 F g⁻¹ at a current density of 0.5 A g⁻¹ and a capacitance degradation of 26.9% after 2000 cycles, much better than those of pristine PEDOT and PEDOT/CNTs (50 wt.% PEDOT). The enhanced electrochemical performance of the PEDOT/PSS-CNTs nanocomposite (50 wt.% PEDOT) should be attributed to the high uniform system of the nanocomposite, resulting in the large surface easily contacted by abundant electrolyte ions through the three-dimensional conducting matrix.     

Gas diffusion electrodes containing sulfonated poly (arylene ether) ionomer for polymer electrolyte fuel cells: Part 2. Improvement of the cathode performance

The performances of gas diffusion electrodes (GDEs) containing Pt/C catalyst (48 wt.% and 68 wt.%-Pt) and sulfonated poly (arylene ether) (SPAE) ionomer (ion exchange capacity, IEC = 1.8 and 2.5 meq g⁻¹) as a proton-conducting binder (SPAE-GDE) were examined in a PEFC at 80 °C and relative humidities (RH) from 60% to 100%. Based on our analyses in Part 1, we have succeeded in improving the cathode performance over the whole range of current densities examined by using a high Pt-loading for the catalyst (68 wt.%-Pt/C), in place of the previously used 48 wt.% one, for the reduction of thickness of the catalyst layer, which enabled us to increase the O₂ gas diffusion rate and to suppress the adsorption of the SPAE binder on the Pt surface via an effective utilization of generated water. The performance, especially at low RH, was improved further by employing an SPAE binder with a lower IEC, 1.8 meq g⁻¹ [SPAE(1.8)]. It was demonstrated by cyclic voltammetry that the specific adsorption of the sulfonate or organic moiety on the Pt surface was indeed suppressed for the case of SPAE(1.8). Hence, for the SPAE-GDEs, the use of a high Pt-loading catalyst, together with a binder with an appropriate IEC, is very important.     

A spectro-microscopic investigation of Fe-Co bimetallic catalysts supported on MgO for the production of thin carbon nanotubes

Fe-Co bimetallic catalysts supported on MgO were studied for the catalytic chemical vapor deposition growth of carbon nanotubes (CNTs). Different wt.% metal loadings were investigated at various deposition temperatures and times. Characterization of the products involved thermal analysis (DTA-TGA), X-ray diffraction, spectroscopy (Raman, UPS, EELS and STS) and microscopy (SEM, TEM and STM) techniques. It was found that the metal content is critical, not only to the yield and the structural quality of the synthesized carbon nanotubes, but it can be also used to tune the desired type of synthesized nanotubes. Lower (2 wt.%) loadings of Fe-Co catalysts favor the formation of single- and/or double-wall CNTs for deposition time and temperature 30 min and 800 °C, respectively. Thermal analysis and Raman measurements showed that these thin CNTs were synthesized at high amounts (CNT-per-catalyst wt.% of more than 100%), exhibiting high graphitization degree with only traces of by-products (mainly amorphous carbon) among them. Microscopy results revealed the formation of CNTs bundles, consisting of individual nanotubes with less than 2 nm outer diameter, while additional energy loss measurements pointed out that the deposited CNTs are mainly single wall. Higher (10 wt.%) Fe-Co loadings resulted to the formation of multi-wall CNTs.     

Microwave-polyol synthesis of nanocrystalline ruthenium oxide nanoparticles on carbon nanotubes for electrochemical capacitors

The ruthenium oxide nanoparticles dispersed on multi-wall carbon nanotubes (CNTs) were successfully synthesized via microwave-polyol process combined with forced hydrolysis without additional thermal oxidation or electrochemical oxidation treatment. The HRTEM, Raman spectra and TGA curve indicate that CNTs were uniformly coated with crystalline and partially hydrous RuO₂·0.64H₂O nanoparticles of 2 nm diameter and the loading amount of ruthenium oxide in the composite could be controlled up to 70 wt.%. The specific capacitance was 450 Fg⁻¹ of ruthenium oxide/CNT composite electrode with 70 wt.% ruthenium oxide at the potential scan rate of 10 mV s⁻¹ and it decreased to 362 Fg⁻¹ by 18% at 500 mV s⁻¹. The specific capacitance of ruthenium oxide in the composite was 620 Fg⁻¹ of ruthenium oxide at 10 mV s⁻¹. The ruthenium oxide nanoparticles in ruthenium oxide/CNT nanocomposite electrode had a high ratio of outer charge to total charge of 0.81, which confirmed its high-rate capability of the composite through the preparation of the nano-sized ruthenium oxide particles on the external surface of CNTs.     

Electrochemical enhancement of adsorption capacity of activated carbon fibers and their surface physicochemical characterizations

The adsorption of activated carbon fibers (ACFs) and their surface characteristics were investigated before and after electrochemical polarization. The adsorption kinetics of m-cresol showed the dependence on polarized potential, and the adsorption rate constant increased by 77.1%, from 6.38 × 10⁻³ min⁻¹ at open-circuit (OC) to 1.13 × 10⁻² min⁻¹ at polarization of 600 mV. The adsorption isotherms at different potentials were in good agreement with Langmuir isotherm model, and the maximum adsorption capacity increased from 2.28 mmol g⁻¹ at OC to 3.67 mmol g⁻¹ at polarized potential of 600 mV. These indicated that electrochemical polarization could effectively improve the adsorption rate and capacity of ACFs. The surface characteristics of ACFs before and after electrochemical polarization were evaluated by N₂ adsorption-desorption isotherms, scanning electron microscope (SEM), zeta potential and Fourier transform infrared spectroscopy (FTIR). The results showed that the BET specific surface area and pore size increased as the potential rose. However, the surface chemical properties of ACFs hardly changed under electrochemical polarization of less than 600 mV. This study was beneficial to understand the mechanism of electrochemically enhanced adsorption.     

Electrochemical performance of arc-produced carbon nanotubes as anode material for lithium-ion batteries

The effects of etching process on the morphology, structure and electrochemical performance of arc-produced multiwalled carbon nanotubes (CNTs) as anode material for lithium-ion batteries were systematically investigated by TEM and a variety of electrochemical testing techniques. It was found that the etched CNTs exhibited four times higher reversible capacity than that of raw CNTs, and possessed excellent cyclability with almost 100% capacity retention after 30 cycles. The kinetic properties of three kinds of CNTs electrodes involving the pristine (CNTs-1), etched (CNTs-2) as well as etch-carbonized samples (CNTs-3) were characterized via ac impedance measurement. It was indicated that, after 30 cycles the exchange current density i₀ of etched CNTs ((7.6-7.8) × 10⁻³ A cm⁻²) was higher than that of the raw CNTs (5.9 × 10⁻³ A cm⁻²), suggesting the electrochemical activity of CNTs was enhanced by the etching treatment. The storage characteristics of the CNTs electrodes at room temperature and 50 °C were particularly compared. It was found that the film resistance on CNTs electrode generally tended to become large with the elongation of storage time, especially storage at high temperature. In comparison with CNTs-1 and CNTs-3, CNTs-2 exhibited more distinctly increase of film resistance, which is related with the surface properties.     

Development of electrical conductivity with minimum possible percolation threshold in multi-wall carbon nanotube/polystyrene composites

A method is reported that involves the bulk polymerization of styrene monomer in the presence of multi-wall carbon nanotubes (MWCNTs) and polystyrene (PS) beads, for the preparation of MWCNT/PS conducting composites with a significantly lower (0.08 wt.% MWCNT) percolation threshold than previously reported. Thus, the conductivities of 7.62 × 10⁻⁵ and 1.48 × 10⁻³ S cm⁻¹ were achieved in the MWCNT/PS composites through homogeneous dispersion of 0.08 and 0.26 wt.% CNTs, respectively in the in situ polymerized PS region by using 70 wt.% PS beads during the polymerization. The extent of dispersion and location of the MWCNTs in the PS matrix has been investigated with a scanning and transmission electron microscopy. The conductivity of the composites was increased with increasing wt.% of the PS beads at a constant CNT loading, indicating the formation of a more continuous network structure of the CNTs in PS matrix.     

Adsorption of cadmium(II) from aqueous solution by surface oxidized carbon nanotubes

Carbon nanotubes (CNTs) were oxidized with H₂O₂, KMnO₄ and HNO₃. Their physicochemical properties were investigated by BET N₂ adsorption, laser particle examination, Boehm’s titration, zeta potential measurement and cadmium(II) adsorption. The experimental results suggest that cadmium(II) adsorption capacities for three kinds of oxidized CNTs increase due to the functional groups introduced by oxidation compared with the as-grown CNTs. The cadmium(II) adsorption capacity of the as-grown CNTs is only 1.1 mg g⁻¹, while it reaches 2.6, 5.1 and 11.0 mg g⁻¹ for the H₂O₂, HNO₃ and KMnO₄ oxidized CNTs, respectively, at the cadmium(II) equilibrium concentration of 4 mg l⁻¹. Adsorption of cadmium(II) by CNTs was strongly pH-dependent and the increase of adsorption capacities for HNO₃ and KMnO₄ oxidized CNTs is more obvious than that of the as-grown and H₂O₂ oxidized CNTs at lower pH regions. The experiments of CNT dosage effect on the cadmium(II) adsorption show that the adsorption capacity for KMnO₄ oxidized CNTs has a sharper increase at the CNT dosage from 0.03 to 0.08 g per 100 ml than the as-grown, H₂O₂ and HNO₃ oxidized CNTs and its removal efficiency almost reaches 100% at CNT dosage of 0.08 g per 100 ml. Analysis revealed that the KMnO₄ oxidized CNTs hosted manganese residuals, and these surely contributed to cadmium sorption to a yet-undefined extent.     

The cutting of multi-walled carbon nanotubes and their strong interfacial interaction with polyamide 6 in the solid state

The cutting of multi-walled carbon nanotubes (MWCNTs) using solid state shear milling (S³M) method and their strong interfacial interaction with polyamide 6 (PA6) in the solid state were studied. Transmission electron microscopy showed that after milling, the CNTs were greatly reduced in length, and disentangled, being straighter with open ends. Fourier transform infrared spectra and differential scanning calorimeter analysis indicated the existence of strong interfacial interactions between MWCNTs and PA6 of the pan-milled PA6/CNTs powder. It was further quantified by thermogravimetric analysis that about 30 wt.% of PA6 formed a strong combining force with CNTs after pan-milling. The mechanism of cutting CNTs and the reason for their strong interfacial interactions with PA6 in the solid state were discussed. A fine and homogeneous dispersion of CNTs throughout PA6 matrix was observed by scanning electron microscopy. The tensile properties of the composites prepared by the S³M method were significantly improved compared to those of pure PA6 and composites prepared by conventional melt mixing. Upon incorporation of only 1.5 wt.% MWCNTs, the tensile modulus of PA6 was enhanced from 2448 MPa to 4439 MPa, by about 80%, and the tensile strength was increased by about 23%.     

Carbon nanotube/epoxy composites fabricated by resin transfer molding

Carbon nanotube (CNT)/epoxy composites with controllable alignment of CNTs were fabricated by a resin transfer molding process. CNTs with loading up to 16.5 wt.% were homogenously dispersed and highly aligned in the epoxy matrix. Both mechanical and electrical properties of the CNT/epoxy composites were dramatically improved with the addition of the CNTs. The Young’s modulus and tensile strength of the composites reach 20.4 GPa and 231.5 MPa, corresponding to 716% and 160% improvement compared to pure epoxy. The electrical conductivity of the composites along the direction of the CNT alignment reaches over 1 × 10⁴ S/m.     

Effects of electric potential on hydrogen adsorption

Hydrogen adsorption isotherms of activated carbon and its mixture with platinum coated activated carbon under various electric potentials and hydrogen pressures were measured at ambient temperature. Results indicated that electric potential enhanced hydrogen adsorption. The higher the applied electric potential is, the higher the hydrogen adsorption capacity is in the experimental range of 0-3000 V. The total amount of hydrogen adsorption increases with the hydrogen pressure. However, the enhancement is more obvious at hydrogen pressures below 10 bars. The enhancement ratio can reach about 160% at 1.6 bars pressure and 3000 V applied electric potential, but decreases to about 20% at 80 bars pressure under the same voltage. The adsorption enhancement is much more significant for the mixture of platinum coated activated carbon and activated carbon at a ratio of 1-4. At 1.6 bars, the hydrogen adsorption capacity increases from 0.008 wt.% at 0 V to 0.058 wt.% at 2500 V, which is a 625% adsorption enhancement. At 83 bars, the hydrogen adsorption capacity increases from 0.43 wt.% at 0 V to 0.56 wt.% at 2500 V, about 30% adsorption enhancement.     

Structure and electrochemical performance of nanostructured Fe3O4/carbon nanotube composites as anodes for lithium ion batteries

Polyvinyl alcohol (PVA) was used as a hydrogen bond functionalizing agent to modify multi-walled carbon nanotubes (CNTs). Nanoparticles of Fe₃O₄ were then formed along the sidewalls of the as-modified CNTs by the chemical coprecipitation of Fe²⁺ and Fe³⁺ in the presence of CNTs in an alkaline solution. The structure and electrochemical performance of the Fe₃O₄/CNTs nanocomposite electrodes have been investigated in detail. Electrochemical tests indicated that at the 145th cycle, the CNTs-66.7 wt.%Fe₃O₄ nanocomposite electrode can deliver a high discharge capacity of 656 mAh g⁻¹ and stable cyclic retention. The improvement of reversible capacity and cyclic performance of the Fe₃O₄/CNTs nanocomposite could be attributed to the nanosized Fe₃O₄ particles and the network of CNTs.     

Adsorption of vitamin B12 on ordered mesoporous carbons coated with PMMA

Ordered mesoporous carbons CMK-3 and CMK-1 were prepared from SBA-15 and MCM-48 materials with pore diameters 3.9 nm and 2.7 nm, respectively. When both mesoporous carbons were coated with about 10 wt.% poly(methyl methacrylate) (PMMA), the pore diameters decreased from 3.9 nm to 3.4 nm for CMK-3 and from 2.7 nm to 2.5 nm for CMK-1. These mesoporous carbons containing about 10 wt.% PMMA were studied as adsorbents of Vitamin B 12 (VB12) from water solutions, and their performances were compared with that of pristine CMK-3, CMK-1. Compared with CMK-1, CMK-3 showed higher vitamin B12 adsorption due to a larger mesopore volume, a higher BET surface and a larger pore diameter. After coated with PMMA, both mesoporous carbons showed higher adsorption capacity than pristine materials. The adsorption properties were influenced by the pore structure and surface properties of mesoporous carbons.     

Hydrogen storage on chemically activated carbons and carbon nanomaterials at high pressures

Hydrogen adsorption measurements have been carried out at different temperatures (298 K and 77 K) and high pressure on a series of chemically activated carbons with a wide range of porosities and also on other types of carbon materials, such as activated carbon fibers, carbon nanotubes and carbon nanofibers. This paper provides a useful interpretation of hydrogen adsorption data according to the porosity of the materials and to the adsorption conditions, using the fundamentals of adsorption. At 298 K, the hydrogen adsorption capacity depends on both the micropore volume and the micropore size distribution. Values of hydrogen adsorption capacities at 298 K of 1.2 wt.% and 2.7 wt.% have been obtained at 20 MPa and 50 MPa, respectively, for a chemically activated carbon. At 77 K, hydrogen adsorption depends on the surface area and the total micropore volume of the activated carbon. Hydrogen adsorption capacity of 5.6 wt.% at 4 MPa and 77 K have been reached by a chemically activated carbon. The total hydrogen storage on the best activated carbon at 298 K is 16.7 g H₂/l and 37.2 g H₂/l at 20 MPa and 50 MPa, respectively (which correspond to 3.2 wt.% and 6.8 wt.%, excluding the tank weight) and 38.8 g H₂/l at 77 K and 4 MPa (8 wt.% excluding the tank weight).     

Comparison with as-grown and microwave modified carbon nanotubes to removal aqueous bisphenol A

This study utilized carbon nanotubes (CNTs) to remove bisphenol A (BPA) from aqueous solution. The surfaces of CNTs were modified by SOCl₂/NH₄OH under microwave irradiation. The surface characteristics of as-grown and modified CNTs were analyzed by measuring zeta potential, and using a scanning electron microscope, a surface area analyzer and a Fourier transform infrared spectroscope. The specific surface area of modified CNTs exceeded that of as-grown CNTs. The pH_iep values of as-grown CNTs and modified CNTs were determined to be 4.3 and 6.5, respectively. Some amine functionalities were formed on the surface of modified CNTs; therefore, the surface of the modified CNTs contained more positive charges than that of the as-grown CNTs. The adsorption kinetics were examined using pseudo first- and second-order models, intraparticle diffusion and Bangham's models. The equilibrium data were simulated using Langmuir, Freundlich, Dubinin and Radushkevich (D-R) and Temkin isotherms. The results reveal that the pseudo second-order model and Langmuir isotherm fit the kinetics and equilibrium data, respectively. The adsorption capacity of BPA on the surface of CNTs fluctuates very little with pH in the range of 3-9, suggesting the high stability of CNTs as an adsorbent for BPA over a rather wide pH range. The values of ΔH⁰ and ΔS⁰ were calculated to be − 11.7 kJ/mol and 46.1 J/mol, respectively. The isotherm and thermodynamic simulations indicate that the adsorption of BPA onto as-grown CNTs proceeds by physisorption process.     

Preparation of polystyrene-based activated carbon spheres with high surface area and their adsorption to dibenzothiophene

Polystyrene-based activated carbon spheres (PACS_K) with high surface area were prepared through KOH activation. Effects of the carbonization temperature and the ratio of KOH to carbon spheres (CS) on the textural structure, hardness and yield of the resultant PACS_K were studied, and their adsorption to dibenzothiophene (DBT) were investigated. The as-prepared PACS_K exhibited a high surface area (up to 2022 m²/g), large total pore volume (≥ 0.78 cm³/g), superior mechanical hardness and high adsorption capacity (ca. 153 mg/g). With the increase of the KOH/CS ratio from 2:1 to 4:1, the surface area, total pore volume, volume of micropores, and volume of mesopores, increase, whereas the volume of small-micropores (< 0.8 nm) decreases from 0.36 to 0.31 cm³/g. The adsorption capacity has a good linear correlation with the volume of small-micropores rather than the surface area. In addition, the large quantity of acidic oxygen-containing groups of PACS_K may also be responsible for their higher adsorption capacity and selectivity of DBT. The PACS_K saturated by DBT can be regenerated by a washing process in a shaking bath or using ultrasonic with toluene at 80 °C.     

Preparation, characterization and Methylene Blue adsorption of phosphoric acid activated carbons from globe artichoke leaves

Activated carbons were prepared by the pyrolysis of artichoke leaves impregnated with phosphoric acid at 500 °C for different impregnation ratios: 100, 200, 300 wt.%. Materials were characterized for their surface chemistry by elemental analysis, “Boehm titrations”, point of zero charge measurements, infrared spectroscopy, as well as for their porous and morphological structure by Scanning Electron Microscopy and nitrogen adsorption at 77 K. The impregnation ratio was found to govern the porous structure of the prepared activated carbons. Low impregnation ratios (~ 100 wt.%) led to essentially microporous and acidic activated carbons whereas high impregnation ratios (> 100 wt.%) gave essentially microporous-mesoporous carbons with specific surface areas as high as 2038 m²·g^− 1, pore volume as large as 2.47 cm³·g^− 1, and a slightly acidic surface. The prepared activated carbons were studied for their adsorption isotherms of Methylene Blue at pH = 3 and pH = 9. The supermicroporous structure of the material produced at 200 wt.% H₃PO₄ ratio was found to be appropriate for an efficient adsorption of this dye controlled by dispersive and electrostatic interactions depending on the amount of oxygen at the surface.     

Removal of Remazol Brilliant Blue R dye from aqueous solutions by adsorption onto immobilized Scenedesmus quadricauda: Equilibrium and kinetic modeling studies

The green algae Scenedesmus quadricauda was immobilized in alginate gel beads. The immobilized active (IASq) and heat inactivated S.quadricauda (IHISq) were used for the removal of Remazol Brilliant Blue R (CI 61200, Reactive Blue 19, RBBR) from aqueous solutions in the concentration range 25-200 mg L^− 1. At 150 mg L^− 1 initial dye concentration the IASq and IHISq exhibited the highest dye uptake capacity at 30 °C, at the initial pH value of 2.0. At the same initial dye concentration in the batch system the adsorption capacity was determined for IASq as 44.2; 44.9 and 45.7 mg g^− 1 in 30, 60 and 300 min, respectively. After 300 min the adsorption capacity hardly changed during the adsorption time. The IHISq of adsorption capacity was observed as 47.6; 47.8 and 48.3 mg g^− 1 in 30, 60 and 300 min, respectively. After 300 min the adsorption capacity was not changed for 24 h. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Flory-Huggins isotherm models were used to fit the equilibrium biosorption data. The Langmuir, Freundlich and Dubinin-Radushkevich equations have better coefficients than Temkin and Flory-Huggins equation describing the RBBR dye adsorption onto IASq and IHISq. The monomolecular biosorption capacity of the biomass was found to be 68 and 95.2 mg g^− 1 for IASq and IHISq, respectively. From the Dubinin-Radushkevich model, the mean free energy was calculated as 6.42-7.15 kJ mol^− 1 for IASq and IHISq, indicating that the biosorption of dye was taken place in physical adsorption reactions. The experimental data were also tested in terms of kinetic characteristics and it was determined that the biosorption process of dye was well explained with pseudo-second-order kinetics.     

Preparation and adsorption mechanism of polyvinyl alcohol/graphene oxide-sodium alginate nanocomposite hydrogel with high Pb(II) adsorption capacity

A series of polyvinyl alcohol (PVA)/graphene oxide (GO)-sodium alginate (SA) nanocomposite hydrogel beads were prepared through in situ crosslinking for Pb²⁺ removal. It was found that PVA and SA molecules were intercalated into GO layers through hydrogen bonding interactions, leading to the destruction of orderly structure of GO, while GO uniformly distributed in PVA matrix. With increasing PVA solution concentration, the hydrogel beads became more regular, a large number of polygonal pores with thin walls and open pores formed, the average pore size decreased, and the dense network structure formed. Meanwhile, the permeability of the composite hydrogel decreased, leading to the decline of Pb²⁺ adsorption capacity of the composite hydrogel. With increasing GO content, the ballability of the hydrogel beads was weakened, the pore size increased, and relatively loose network structure formed, resulting in an increase in permeability and Pb²⁺ adsorption capacity of the hydrogel, reaching up to 279.43 mg g⁻¹. Moreover, the composite hydrogel presented relatively good reusability for Pb²⁺ removal. The adsorption mechanism was explored and showed that the adsorption system of the composite hydrogel belonged to the second-order kinetic model and fitted Langmuir adsorption isotherm model for Pb²⁺ removal, which might be mono-layer chemical adsorption. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47318.